ALBERT

Description:    The dynamic behavior of two types of sandwich composites made of E-Glass Vinyl-Ester (EVE) facesheets and Corecell™ A-series foam with a polyurea interlayer was studied using a shock tube apparatus. The materials, as well as the core layer arrangements, were identical, with the only difference arising in the location of the polyurea interlayer. The foam core itself was layered with monotonically increasing wave impedance of the core layers, with the lowest wave impedance facing the shock loading. For configuration 1, the polyurea interlayer was placed behind the front facesheet, in front of the foam core, while in configuration 2 it was placed behind the foam core, in front of the back facesheet. A high-speed side-view camera, along with a high-speed back-view 3-D Digital Image Correlation (DIC) system, was utilized to capture the real time deformation process as well as mechanisms of failure. Post mortem analysis was also carried out to evaluate the overall blast performance of these two configurations. The results indicated that applying polyurea behind the foam core and in front of the back facesheet will reduce the back face deflection, particle velocity, and in-plane strain, thus improving the overall blast performance and maintaining structural integrity. Content Type Journal Article Pages 1-15 DOI 10.1007/s11340-011-9517-9 Authors N. Gardner, Dynamic Photomechanics Laboratory, Department of Mechanical, Industrial & Systems Engineering, University of Rhode Island, 92 Upper College Road, Kingston, RI 02881, USA E. Wang, Dynamic Photomechanics Laboratory, Department of Mechanical, Industrial & Systems Engineering, University of Rhode Island, 92 Upper College Road, Kingston, RI 02881, USA P. Kumar, Dynamic Photomechanics Laboratory, Department of Mechanical, Industrial & Systems Engineering, University of Rhode Island, 92 Upper College Road, Kingston, RI 02881, USA A. Shukla, Dynamic Photomechanics Laboratory, Department of Mechanical, Industrial & Systems Engineering, University of Rhode Island, 92 Upper College Road, Kingston, RI 02881, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    A coordinated modeling and experimental effort to investigate the shear stress-shear strain rate response of ballistic gelatin is presented. A power-law constitutive model that captures non-Newtonian shear-thickening behavior, the evolution of viscosity, and the momentum diffusion at high shear rates is adopted. A simple asymptotic relationship between the maximum wall shear stress and the maximum striking wall velocity is derived in the high diffusion rate regime for a shear flow between two parallel plates. Experimental investigation is conducted on double lap-shear test fixture with gelatin specimens of different thicknesses subjected to high strain rate input on the inner surface, generated by a polymer split Hopkinson pressure bar. This test fixture allows measurement of transmitted shear stress as well as visualization of momentum diffusion through gelatin when imaged by a high speed camera. Gelatin specimens of various thicknesses were used for extracting the power-law model parameters. It is found that ballistic gelatin behaves as a shear-thickening fluid at high shear rates with a power-law exponent of 2.22. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-011-9513-0 Authors G. Subhash, Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611, USA J. Kwon, Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611, USA R. Mei, Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611, USA D. F. Moore, Department of Neurology, Tulane University School of Medicine, New Orleans, LA 70112, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    An experimental-numerical hybrid method for the stress separation in photoelasticity is proposed in this study. In the proposed method, boundary conditions for a local finite element model, that is, tractions along boundaries are inversely determined from photoelastic fringes. Two algorithms are proposed for determining the boundary condition. One is a linear algorithm in which the tractions are obtained by the method of linear least-squares from both principal stress difference and principal direction. Another is the nonlinear algorithm in which the tractions are determined only from the principal stress difference. After determining the boundary conditions for the local finite element model, the stresses can be obtained by finite element direct analysis. The effectiveness is demonstrated by applying the proposed method to a perforated plate under tension and contact problems. Results show that the boundary conditions of the local finite element model can be determined from the photoelastic fringes and then the individual stresses can be obtained by the proposed method. Furthermore, the stresses can be evaluated even if the boundary condition is complicated such as at the contact surface. It is expected that the proposed method can be powerful tool for stress analysis. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-011-9512-1 Authors S. Yoneyama, Department of Mechanical Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 252–5258, Japan S. Arikawa, Department of Mechanical Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 252–5258, Japan Y. Kobayashi, Department of Mechanical Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 252–5258, Japan Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    A non-invasive measurement method for transparent objects using digital holographic interferometry based on iterative least-squares phase unwrapping is presented. Holograms are captured and processed by digital method. The phase reconstructed from holograms is wrapped. Continual and real phase is obtained by phase unwrapping. In this paper iterative unwrapping of phase difference is combined with least-squares unwrapping to eliminate errors. The relations between the phase variation of object wave and the thickness deformation and stress of transparent object are given. A polymethyl methacrylate (PMMA) specimen with a hole under uniform tensile force is tested by this method. The experimental results are in accordance with the theoretical ones. That means the method is correct. Content Type Journal Article Pages 1-7 DOI 10.1007/s11340-011-9516-x Authors H.-T. Xia, Faculty of Civil and Architectural Engineering, Kunming University of Science and Technology, Kunming, Yunnan 650093, China R.-X. Guo, Faculty of Civil and Architectural Engineering, Kunming University of Science and Technology, Kunming, Yunnan 650093, China Z.-B. Fan, Faculty of Science, Kunming University of Science and Technology, Kunming, Yunnan 650093, China H.-M. Cheng, Faculty of Civil and Architectural Engineering, Kunming University of Science and Technology, Kunming, Yunnan 650093, China B.-C. Yang, Faculty of Civil and Architectural Engineering, Kunming University of Science and Technology, Kunming, Yunnan 650093, China Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The aim of the present study is to investigate the nucleation and growth behavior of twin region around yield point of polycrystalline pure Ti under deformation. Firstly, we prepare commercial polycrystalline pure Ti plate, and investigate the microstructure and pole figures using an Electron Backscatter Diffraction Patterns device. Secondly, tensile specimens are cut out from 0°, 30°, 45° and 90° relative to plate rolling direction. Then, we measure the macroscopic stress–strain curve, local strain distribution and nucleation and growth of twin region arising in specimens under uniaxial tensile loading. Results show the anisotropic characteristics in those behaviors. Those could be related to c axis in hcp lattice. However, detailed anisotropic mechanism may have something to do with several interactions between slips and twins arising in its body. It is also understood that the avalanche behavior of twin region nucleation occurs as a result of larger twin region formation, with inhomogeneous small twin region nucleation in transient process. Finally, we could suppose the bridge mechanism of deformation behaviors from macroscale to microscale for polycrystalline pure Ti under deformation. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-011-9508-x Authors G. Murasawa, Department of Mechanical Engineering, Yamagata University, 4-3-16, Jonan, Yonezawa, Yamagata 992-8510, Japan T. Morimoto, Department of Mechanical Engineering, Yamagata University, 4-3-16, Jonan, Yonezawa, Yamagata 992-8510, Japan S. Yoneyama, Department of Mechanical Engineering, Aoyama Gakuin University, 5-10-1, Fuchinobe, Sagamihara, Kanagawa 229-8558, Japan Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    A microelectromechanical systems (MEMS) cantilever array was monolithically fabricated in the gap region of a split ring resonator (SRR) to enable electrostatic tuning of the resonant frequency. The design consisted of two concentric SRRs each with a set of cantilevers extending across the split region. The cantilever array consisted of five beams that varied in length from 300 to 400 μm, with each beam adding about 2 pF to the capacitance as it actuated. The entire structure was fabricated monolithically to reduce its size and minimize losses from externally wire bonded components. The beams actuate one at a time, longest to shortest with an applied voltage ranging from 30–60 V. The MEMS embedded SRRs displayed dual resonant frequencies at 7.3 and 14.2 GHz or 8.4 and 13.5 GHz depending on the design details. As the beams on the inner SRR actuated the 14.2 GHz resonance displayed tuning, while the cantilevers on the outer SRR tuned the 8.4 GHz resonance. The 14.2 GHz resonant frequency shifts 1.6 GHz to 12.6 GHz as all the cantilevers pulled-in. Only the first two beams on the outer cantilever array pulled-in, tuning the resonant frequency 0.4 GHz from 8.4 to 8.0 GHz. Content Type Journal Article Pages 1-9 DOI 10.1007/s11340-011-9498-8 Authors E. A. Moore, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson Air Force Base, Wright-Patterson AFB, OH 45433, USA D. Langley, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson Air Force Base, Wright-Patterson AFB, OH 45433, USA M. E. Jussaume, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson Air Force Base, Wright-Patterson AFB, OH 45433, USA L. A. Rederus, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson Air Force Base, Wright-Patterson AFB, OH 45433, USA C. A. Lundell, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson Air Force Base, Wright-Patterson AFB, OH 45433, USA R. A. Coutu, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson Air Force Base, Wright-Patterson AFB, OH 45433, USA P. J. Collins, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson Air Force Base, Wright-Patterson AFB, OH 45433, USA L. A. Starman, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson Air Force Base, Wright-Patterson AFB, OH 45433, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The resistance of glass-fibre reinforced polymer (GFRP) sandwich panels and laminate tubes to blast in air and underwater environments has been studied. Procedures for monitoring the structural response of such materials during blast events have been devised. High-speed photography was employed during the air-blast loading of GFRP sandwich panels, in conjunction with digital image correlation (DIC), to monitor the deformation of these structures under shock loading. Failure mechanisms have been revealed by using DIC and confirmed in post-test sectioning. Strain gauges were used to monitor the structural response of similar sandwich materials and GFRP tubular laminates during underwater shocks. The effect of the backing medium (air or water) of the target facing the shock has been identified during these studies. Mechanisms of failure have been established such as core crushing, skin/core cracking, delamination and fibre breakage. Strain gauge data supported the mechanisms for such damage. These studies were part of a research programme sponsored by the Office of Naval Research (ONR) investigating blast loading of composite naval structures. The full-scale experimental results presented here will aid and assist in the development of analytical and computational models. Furthermore, it highlights the importance of support and boundary conditions with regards to blast resistant design. Content Type Journal Article Pages 1-23 DOI 10.1007/s11340-011-9506-z Authors H. Arora, Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ UK P. A. Hooper, Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ UK J. P. Dear, Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ UK Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    A cyclic biaxial stress measurement method using electrodeposited copper foil was examined. The crystallographic orientations of individual grains that undergo grain growth in copper foil subjected to cyclic loading were analyzed by electron backscatter diffraction (EBSD). One of the slip directions in most of the grains corresponded to the direction of maximum shear stress when the biaxial stress ratio was negative. However, the number of grains with other orientations gradually increased as the biaxial stress ratio approached zero. On the basis of these features, we propose biaxial stress measurement using EBSD analysis of grown grains in copper foil. Our new method has excellent resolution compared with other stress-strain measurement methods since it can measure the average biaxial stress ratios in an area of 500 μm × 500 μm. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-011-9515-y Authors Y. Ono, Department of Mechanical and Aerospace Engineering, Tottori University, 4-101, Koyama-cho Minami, Tottori, 680–8552 Japan S. Morito, Department of Materials Science, Shimane University, 1060, Nishikawatsu, Matsue, Shimane, 690–8504 Japan C. Li, Department of Mechanical and Aerospace Engineering, Tottori University, 4-101, Koyama-cho Minami, Tottori, 680–8552 Japan Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    To characterize the materials parameters and deformation of a convex shell of axial symmetry, a hydrogel contact lens is mechanically deformed by two loading configurations: (a) compression between two parallel plates and (b) central load applied by a shaft with a spherical tip. A universal testing machine with nano-Newton and submicron resolutions is used to measure the applied force, F , as a function of vertical displacement of the plate/shaft, w 0 , while a homemade laser aided topography system records the in-situ deformed shell profile and the contact radius or central dimple, a . A nonlinear shell theory and an iterative finite difference method are used to account for the large elastic deformation, the central buckling for the central load compression, and the interrelationship between the measureable quantities ( F , w 0 , a ). Content Type Journal Article Pages 1-11 DOI 10.1007/s11340-011-9514-z Authors J. Shi, Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA M. Robitaille, Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA S. Muftu, Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA K.-T. Wan, Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    In this paper a non-contact excitation system based on electromagnets is described. The system aims at exciting cyclically symmetric structures like bladed disks by generating typical engine order-like travelling wave excitations that bladed disks encounter during service. Detailed description of the analytical formulation for the electromagnets sizing, quality assessment and practical implications of the final assembly for the bladed disk excitation are addressed. In particular, the paper proposes an original method to setup the excitation system in order to perform step-sine controlled force measurements. This feature is necessary when non-linear forced response must be measured on bladed disks in order to characterize the dynamic behaviour at different level of excitation. Typical applications of the designed excitation system are two: the first is the study of the effect of a force pattern characterized by a particular engine order on the forced response of mistuned bladed disks, the second is the characterization of intentional non-linear damping source occurring, for instance, for friction phenomena in presence of shrouds or underplatform dampers. Content Type Journal Article Pages 1-13 DOI 10.1007/s11340-011-9504-1 Authors C. M. Firrone, Department of Mechanical Engineering, Politecnico di Torino, Corso Duca degli Abruzzi, 24, Torino, Italy T. Berruti, Department of Mechanical Engineering, Politecnico di Torino, Corso Duca degli Abruzzi, 24, Torino, Italy Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    An experimental methodology has been developed to characterize local strain heterogeneities in alloys via in-situ scanning electron microscope (SEM) based mechanical testing. Quantitative measurements of local strains as a function of grain orientation, morphology and neighborhood are crucial for mechanistic understanding and validation of crystal plasticity models. This study focuses on the technical challenges associated with performing creep tests at elevated temperatures ≤700°C in an SEM. Samples of nickel-based superalloy Rene 104 were used for this study, but the technique is applicable to testing of any metal samples at elevated temperature. Electron beam lithography was employed to produce a suitable surface speckle pattern of hafnium oxide to facilitate full field displacement measurements using a commercial software package. The speckle pattern proved to have good thermal stability and provided excellent contrast for image acquisition using secondary electron imaging at elevated temperature. The speckle pattern and microscope magnification were optimized to obtain the resolution necessary to discern strain localizations within grain interiors and along grain boundaries. Minimum strain resolution due to SEM image distortions was determined prior to tensile testing, and image integration methods were utilized to minimize imaging artifacts. Limitations due to the present specimen heating method and potential solutions to these limitations are also addressed. Content Type Journal Article Pages 1-12 DOI 10.1007/s11340-011-9499-7 Authors J. L. Walley, The Ohio State University, 477 Watts Hall, 2041 College Rd., Columbus, OH 43210, USA R. Wheeler, UES, Inc., 4401 North Dayton-Xenia Rd., Dayton, OH 45432, USA M. D. Uchic, Air Force Research Laboratory, Materials & Manufacturing Directorate, AFRL/RXLM, Wright Patterson AFB, Dayton, OH 45433, USA M. J. Mills, The Ohio State University, 477 Watts Hall, 2041 College Rd., Columbus, OH 43210, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The low specific weight of composite materials, together with their excellent mechanical properties, make them suitable to be widely used in many modern engineering structures. However, composite materials are quite sensitive to impacts: a specific kind of damage, called Barely Visible Impact Damage (BVID), may occur, constituting an unsafe failure of difficult assessment. In the past few years several methods have been developed aiming at assessing this type of damage. In this paper, a vibration-based technique that combines both the natural frequencies and the modal damping factors as damage sensitive features is tested for locating impact damage in carbon fibre reinforced laminates. The method is intended to be used for locating damage in real laminated composite structures that undergo in-service impacts, such as an airplane’s fuselage or wings. Assessing a minimum of one response coordinate is the strict requirement during each inspection, because it uses the dynamic global parameters of the structure as damage features. This is possible because the method assumes that, at least for BVID, the mode shapes remain practically unchanged. The theory is summarized and the method is tested using experimental setups where damage is introduced at different locations. Additionally, the hypothesis that different damage morphologies on composite materials have different contributions to the damage features is addressed. Content Type Journal Article Pages 1-16 DOI 10.1007/s11340-011-9472-5 Authors D. Montalvão, Department of Mechanical Engineering, Escola Superior de Tecnologia, Polytechnic Institute of Setúbal, Campus do IPS, Estefanilha, 2910-761 Setúbal, Portugal A. M. R. Ribeiro, Department of Mechanical Engineering, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon, Portugal J. A. B. Duarte-Silva, Department of Mechanical Engineering, Escola Superior de Tecnologia, Polytechnic Institute of Setúbal, Campus do IPS, Estefanilha, 2910-761 Setúbal, Portugal Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    This work presents a novel experimental apparatus to determine the cutting effectiveness of grinding grits. The apparatus consists of a custom high-speed scratch tester, a force measurement system, and an offline 3D optical profilometer. Preliminary results based on a spherical tool are presented to demonstrate the usefulness of the system. Experiments were performed at depths of cut ranging from 0.3 μm to 7.5 μm at cutting speeds of 5 m/s to 30 m/s in 5 m/s increments. High resolution scans of the scratch profiles provided insight into the change in the cutting mechanics as the depth of cut and cutting speed were increased. In general, lower cutting speeds produced higher pile-up heights while higher cutting speeds produced lower pile-up heights. The force measurements indicated that the normal forces increased with cutting speed due to strain rate hardening of the workpiece material while the tangential forces decreased with cutting speed due to a reduction in the coefficient of friction and a change in the cutting mechanics. The force ratio data and the specific energy data both demonstrated high slopes at low depths of cut due to asperity contact between the tool and the workpiece. The modular nature of the developed system allows different grit geometries to be investigated. Content Type Journal Article Pages 1-9 DOI 10.1007/s11340-011-9471-6 Authors D. Anderson, Department of Mechanical Engineering, Dalhousie University, Halifax, NS Canada B3J 1Z1 A. Warkentin, Department of Mechanical Engineering, Dalhousie University, Halifax, NS Canada B3J 1Z1 R. Bauer, Department of Mechanical Engineering, Dalhousie University, Halifax, NS Canada B3J 1Z1 Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Joint kinematic and thermal full field measurement provides rich and relevant information on the thermomechanical properties of materials. A new experimental method is proposed to measure both these fields simultaneously. Although solely based on images captured with a unique infrared camera, it affords both kinematic and thermal fields. It consists of an enriched global Digital Image Correlation technique, where the variation of optical flow due to the local displacement and the change of temperature are jointly evaluated through a decomposition over a finite element mesh. After an a priori evaluation of the performance of the method on synthetic cases, a first experimental application to a Shape Memory Alloy specimen under tension is done. It is shown that the method is able to capture localized transformation bands which are a few pixel wide. Content Type Journal Article Pages 1-15 DOI 10.1007/s11340-011-9483-2 Authors A. Maynadier, Laboratoire de Mécanique et Technologie (LMT-Cachan), ENS de Cachan/CNRS UMR, 8535/Univ. Paris 6/PRES UniverSud Paris, 61 Avenue du Président Wilson, 94235 Cachan Cedex, France M. Poncelet, Laboratoire de Mécanique et Technologie (LMT-Cachan), ENS de Cachan/CNRS UMR, 8535/Univ. Paris 6/PRES UniverSud Paris, 61 Avenue du Président Wilson, 94235 Cachan Cedex, France K. Lavernhe-Taillard, Laboratoire de Mécanique et Technologie (LMT-Cachan), ENS de Cachan/CNRS UMR, 8535/Univ. Paris 6/PRES UniverSud Paris, 61 Avenue du Président Wilson, 94235 Cachan Cedex, France S. Roux, Laboratoire de Mécanique et Technologie (LMT-Cachan), ENS de Cachan/CNRS UMR, 8535/Univ. Paris 6/PRES UniverSud Paris, 61 Avenue du Président Wilson, 94235 Cachan Cedex, France Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    We studied the dynamic response of a two-dimensional square packing of uncompressed stainless steel spheres excited by impulsive loadings. We developed a new experimental measurement technique, employing miniature tri-axial accelerometers, to determine the stress wave properties in the array resulting from both an in-plane and out-of-plane impact. Results from our numerical simulations, based on a discrete particle model, were in good agreement with the experimental results. We observed that the impulsive excitations were resolved into solitary waves traveling only through initially excited chains. The observed solitary waves were determined to have similar (Hertzian) properties to the extensively studied solitary waves supported by an uncompressed, uniform, one-dimensional chain of spheres. The highly directional response of this system could be used as a basis to design granular crystals with predetermined wave propagation paths capable of mitigating stress wave energy. Content Type Journal Article Pages 1-11 DOI 10.1007/s11340-011-9544-6 Authors A. Leonard, Department of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, USA F. Fraternali, Department of Civil Engineering, University of Salerno, 84084 Fisciano, SA, Italy C. Daraio, Department of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Slamming, the impact between a marine craft’s hull and the water surface is a critical load case for structural design of marine vessels. The importance of hull slamming has led to a significant body of work to understand, predict and model these impacts. There is however, a lack of experimental data for validation, particularly for deformable panels and sandwich structures. This paper describes a high-velocity panel slamming test system that enables the generation of comprehensive and reliable experimental data on slamming impacts for both rigid and flexible panel structures. The pressure magnitudes, time-histories and spatial distributions resulting from testing of a nominally rigid panel have been compared with previous analytical, semi-empirical and experimental studies. Slamming impacts of a deformable sandwich panel are shown to cause different pressures to those from a rigid panel impact, resulting in increased transverse shear loading at the panel edge. Content Type Journal Article Pages 1-12 DOI 10.1007/s11340-011-9543-7 Authors M. Battley, Centre for Advanced Composite Materials, Department of Mechanical Engineering, The University of Auckland, Auckland, New Zealand T. Allen, Centre for Advanced Composite Materials, Department of Mechanical Engineering, The University of Auckland, Auckland, New Zealand Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Three-dimensional scanning laser vibrometers enable extremely accurate non-contact measurement of the three-dimensional displacements on the surface of structures. This paper looks at the feasibility of using such a scanning laser vibrometer for the non-contact measurement of dynamic strain fields across the surface of a planar structure subjected to in-plane loading. Issues such as laser head alignment and choice of differentiation filter parameters are discussed. Finally, experimental results of two test specimens are presented which clearly demonstrate the significant potential of this new experimental technique as well as highlighting several limitations. Content Type Journal Article Pages 1-11 DOI 10.1007/s11340-011-9545-5 Authors H. Weisbecker, Institut für Festkörpermechanik, Technische Universität Dresden, 01062 Dresden, Germany B. Cazzolato, School of Mechanical Engineering, University of Adelaide, Adelaide, SA, Australia S. Wildy, School of Computer Science, Engineering and Mathematics, Flinders University of South Australia, Adelaide, SA, Australia S. Marburg, LRT4 - Institute of Mechanics, Universität der Bundeswehr München, 85577 Neubiberg, Germany J. Codrington, School of Mechanical Engineering, University of Adelaide, Adelaide, SA, Australia A. Kotousov, School of Mechanical Engineering, University of Adelaide, Adelaide, SA, Australia Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Since the glass is a birefringent material, the analysis of residual stress in glass is usually carried out by means of photoelastic methods. This paper considers the automation of the “test fringes” method which is based on the use of a Babinet compensator or of a beam subjected to bending. In particular, two automated methods are proposed: the first one is based on the use of the centre fringe method in monochromatic light and the second one is based on the use of RGB photoelasticity in white light. The proposed methods have been applied to the analysis of membranal residual stresses in some tempered glasses, showing that they can effectively replace manual methods of photoelastic analysis of residual stresses in glass. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-011-9558-0 Authors A. Ajovalasit, University of Palermo (Italy), Viale delle Scienze, 90128 Palermo, Italy G. Petrucci, University of Palermo (Italy), Viale delle Scienze, 90128 Palermo, Italy M. Scafidi, University of Palermo (Italy), Viale delle Scienze, 90128 Palermo, Italy Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Indentation tests are performed to evaluate the viscoelastic characteristics of a short-fiber reinforced composite. Finite element analysis is also carried out to estimate the macroscopic viscoelastic characteristics of the composite by using a unit cell models. The results of indentation tests show that a force-displacement curve obtained by the indentation test depends on the area of the fibers appeared in the impression. The creep compliance evaluated by these indentation tests is compared to that by the finite element analysis. As the results, it is suggested that the result of indentation test performed on the surface of the composite without fibers means the measurement result for isotropic composite or anisotropic composite in the direction of the smallest rigidity. On the other hand, indentation test performed on the fiber indicates the measurement result of anisotropic composite in the direction of the largest rigidity. These results present the method to measure the macroscopic characteristics of short-fiber reinforced composite by indentation tests. Content Type Journal Article Pages 1-6 DOI 10.1007/s11340-011-9551-7 Authors K. Sakaue, Department of Mechanical Engineering, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo, 135-8548 Japan T. Isawa, Department of Mechanical Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan T. Ogawa, Department of Mechanical Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan T. Yoshimoto, Mitsubishi Electric Corporation Advanced Technology R&D Center, 8-1-1 Tsukaguti-Honmati, Amagasaki, Hyogo 664-0864, Japan Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Response surface methodology (RSM) is a technique used to determine and represent the cause and effect of relationship between true mean responses and input control variables influencing the responses as an n-dimensional hyper surface. Welded joints are used extensively in many modern industries to fabricate jointed structures that contribute significantly to the inherent slip damping. The main problem faced in the manufacture of such structures is the selection of optimum combination of input variables for achieving the required damping. This problem can be solved by developing the mathematical models through effective and strategic planning and executing experiments by RSM. This investigation highlights the use of RSM by designing a four-factor three-level central composite rotatable design matrix with full replication of planning, conducting, executing and developing the mathematical models. This is useful for predicting the mechanism of interfacial slip damping in layered and welded structures. The design utilizes the initial amplitude of excitation, number of tack welded joints and surface roughness at the interfaces as well as the material property to develop a model for the logarithmic damping decrement of layered and welded structures with different end conditions. Experimental results indicate that the proposed mathematical models adequately predict the logarithmic damping decrement within the limits of the factors that are being investigated. Content Type Journal Article Pages 1-21 DOI 10.1007/s11340-011-9563-3 Authors B. Singh, Department of Mechanical Engineering, National Institute of Technology, Rourkela, Orissa, India B. K. Nanda, Department of Mechanical Engineering, National Institute of Technology, Rourkela, Orissa, India Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    In this work, the notched shear strength test (NST) has been further improved. In order to simplify and accelerate the testing procedure, the notches with declined slopes were used. With the proposed procedure, the shear strength profile in the thickness direction of a paperboard can be measured using one sheet only. By using the test setup, the dependency of shear zone length on shear strength was investigated. Experimental results show that both the measured shear strength values as well as the shear strength profile varied significantly with different shear zone length. Longer shear zone gave lower shear strength values and flatter profiles, while a shorter shear zone gave higher strength values and more pronounced shear strength profiles that better followed the paperboard ply structure. This proposed new method was also compared with the NST, strip shear test (SST) and rigid shear test (RST) method by using the same test material. Content Type Journal Article Pages 1-9 DOI 10.1007/s11340-011-9559-z Authors H. Huang, KTH, Department of Solid Mechanics, 100 44 Stockholm, Sweden M. Nygårds, KTH, Department of Solid Mechanics, 100 44 Stockholm, Sweden Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Calibration procedures for constitutive models for powder compaction are presented. A practical calibration method based on a die compaction experiment is presented. A newly developed apparatus consisting of a die instrumented with radial stress sensors is described. The paper proposes two contributions to account for errors present in instrumented die testing, which are due to 1) elastic compliance of the testing frame, influencing the measurement of axial strain and 2) the presence on non-homogeneous stress state in the test specimen. It is shown that system compliance is important for generating an accurate stress-strain curve for compression. The effect of different compliance correction methods is evaluated with regard to the accuracy of models predicting pressing forces. The system compliance becomes more significant during unloading in the die; this information is used to determine the elastic properties. A new compliance correction method is introduced following a detailed analysis of the forces and deformations of different parts of the loading frame. In instrumented die compaction the axial and radial stresses are measured at fixed locations and the specimen is subject to non-homogeneous stresses and strains due to the effect of friction between the powder and die wall. Starting from the Janssen-Walker method of differential slices a method to account for non-homogeneous stress and strain is developed. Content Type Journal Article Pages 1-14 DOI 10.1007/s11340-011-9542-8 Authors C. Shang, Department of Engineering, University of Leicester, Leicester, UK I. C. Sinka, Department of Engineering, University of Leicester, Leicester, UK J. Pan, Department of Engineering, University of Leicester, Leicester, UK Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    To better understand the failure characteristics of lead titanate zirconate (PZT) piezoelectric ceramics, in-situ measurements of displacement and crack growth rates were conducted during high cycle fatigue testing, e.g., 5 kHz. A commercial PZT ceramic (used in a buzzer) was employed as the specimen. To examine the failure characteristics, two newly proposed systems were used: (i) a high speed camera system and (ii) a condenser microphone system. The former system consisted of two high speed cameras with an analytical system, which could measure the displacement of the PZT ceramic during the cyclic loading. The maximum displacement value of the ceramic was found to be approximately 20 μm at 0.5 kHz. The three-dimensional shape of the PZT ceramic during cyclic loading could be clearly observed. With the latter system, the displacement intensity arising from the ceramic vibration was detected continuously. It was found that the crack growth rate was not correlated with the fatigue frequency due to the resonance caused by the ceramic oscillation. There is a linear relationship between the crack growth rate and sonar intensity. On the basis of the crack growth behavior, the failure characteristics of the PZT ceramic could be clearly determined. Content Type Journal Article Pages 1-12 DOI 10.1007/s11340-011-9550-8 Authors M. Okayasu, Department of Machine Intelligence and Systems Engineering, Akita Prefectural University, 84-4 Aza Ebinokuchi, Tsuchiya, Yurihonjo City, Akita 015-0055, Japan Y. Sato, Department of Machine Intelligence and Systems Engineering, Akita Prefectural University, 84-4 Aza Ebinokuchi, Tsuchiya, Yurihonjo City, Akita 015-0055, Japan Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Many recent works in inverse identification of constitutive parameters have pointed to the need of tests which exhibit heterogeneous strain paths. The present study details a new testing procedure based on out-of-plane motion capture by Stereo-Image Correlation (SIC). With the original test proposed hereby, a unique sample is deformed on a tensile machine along two perpendicular tensile directions, two perpendicular shear directions and one expansion area. The choice of the sample shape is discussed along with the stereo imaging device, 3D reconstruction and measurement uncertainties. The test sample is made from a sheet of commercially pure titanium. A Finite-Element updating inverse method is applied in order to identify six parameters of an anisotropic plastic constitutive model. Results show that this new testing procedure allows every constitutive parameter of the model to be identified from one and only one test. Content Type Journal Article Pages 1-13 DOI 10.1007/s11340-011-9555-3 Authors T. Pottier, Chiang Mai University, Faculty of Engineering, Department of Mechanical Engineering, Chiang Mai, 50200 Thailand P. Vacher, Laboratoire SYMME, Université de Savoie, Polytech’Annecy-Chambéry BP, 80439, 74944 Annecy le Vieux Cedex, France F. Toussaint, Laboratoire SYMME, Université de Savoie, Polytech’Annecy-Chambéry BP, 80439, 74944 Annecy le Vieux Cedex, France H. Louche, Laboratoire de Mécanique et Génie Civil, Université Montpellier II, pl. E. Bataillon, 34095 Montpellier Cedex, France T. Coudert, SINTEF Materials and Chemistry, Trondheim, Norway Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The bulge test is mostly used to analyze equibiaxial tensile stress state at the pole of inflated isotropic membranes. Three-dimensional digital image correlation (3D-DIC) technique allows the determination of three-dimensional surface displacements and strain fields. In this paper, a method is proposed to determine also the membrane stress tensor fields for in-plane isotropic materials, independently of any constitutive equation. Stress-strain state is then known at any surface point which enriches greatly experimental data deduced from the axisymmetric bulge tests. Our method consists, first in calculating from the 3D-DIC experimental data the membrane curvature tensor at each surface point of the bulge specimen. Then, curvature tensor fields are used to investigate axisymmetry of the test. Finally in the axisymmetric case, membrane stress tensor fields are determined from meridional and circumferential curvatures combined with the measurement of the inflating pressure. Our method is first validated for virtual 3D-DIC data, obtained by numerical simulation of a bulge test using a hyperelastic material model. Afterward, the method is applied to an experimental bulge test performed using as material a silicone elastomer. The stress-strain fields which are obtained using the proposed method are compared with results of the finite element simulation of this overall bulge test using a neo-Hookean model fitted on uniaxial and equibiaxial tensile tests. Content Type Journal Article Pages 1-16 DOI 10.1007/s11340-011-9571-3 Authors G. Machado, Laboratoire 3SR, Université de Grenoble/CNRS, BP53, 38041 Grenoble Cedex 9, France D. Favier, Laboratoire 3SR, Université de Grenoble/CNRS, BP53, 38041 Grenoble Cedex 9, France G. Chagnon, Laboratoire 3SR, Université de Grenoble/CNRS, BP53, 38041 Grenoble Cedex 9, France Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    It is well known that granular materials are not homogeneous, i.e. the forces between grains are localized in force chains. However, previous work on plant root growth has neglected this variability in granular soils and reported bulk characteristics or used homogeneous media, such as agar, to grow plant roots. In this paper we report the results of pinto bean root growth through a granular system where photoelastic grains are used to visualize and quantify the local forces in the system. Two issues are addressed: how plant roots respond to different levels of force between grains, and how the growing roots alter the force distribution in a granular system. We find that pinto bean roots are less likely to grow between grains as the force between those grains increases and that roots can exert, on average, 110 mN of force on the granular system. However, both of these observations are time-dependent. Both the inter-grain forces as the roots grow and the forces that the roots impart to the system increase in time without observable concomitant geometric changes in root cross-section. Content Type Journal Article Pages 1-5 DOI 10.1007/s11340-011-9569-x Authors D.M. Wendell, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA K. Luginbuhl, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA J. Guerrero, Schlumberger-Doll Research Center, Cambridge, MA, USA A.E. Hosoi, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Shape analysis techniques such as geometric moment descriptors, Fourier descriptors, wavelet descriptors etc. have been used commercially in the fields of biometrics for finger print matching, iris matching and facial recognition for almost over a decade. These techniques are capable of decomposing high resolution images with 10 5 to 10 6 pixels into only a few hundred unique shape descriptors which are a true representation of the features in the corresponding images thus tremendously reducing the computational data and time required for image analysis and comparison. This paper explores the possibility of employing shape analysis techniques to facilitate the comparison of full-field data obtained from techniques such as digital image correlation, thermoelasticity and photoelasticity for the purpose of validation of computational models and damage assessment. A new shape descriptor is introduced which combines Fourier decomposition with Zernike moments. The Fourier-Zernike descriptor is shown to be capable of decomposing full-field strain distributions containing engineering features and discontinuities arising from damage by combining the desirable properties of its parent shape descriptors while eliminating their individual limitations. Content Type Journal Article Pages 1-13 DOI 10.1007/s11340-011-9570-4 Authors A. S. Patki, Department of Mechanical Engineering, Michigan State University, 2555 Engineering Building, East Lansing, MI 48824, USA E. A. Patterson, Department of Mechanical Engineering, Michigan State University, 2555 Engineering Building, East Lansing, MI 48824, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    In-situ straining experiments and residual stress evaluations by micromachining require accurate measurement of surface displacements. Such measurements can be conveniently done using Digital Image Correlation (DIC). Three surface decoration techniques are presented to enhance surface deformation and residual stress measurement capabilities on micron-scale samples within a Scanning Electron Microscope—Focused Ion Beam (SEM-FIB) instrument. They involve the use of Yttria-stabilized-zirconia nano particles applied chemically, nano platinum dots applied using FIB, and Focused Electron Beam (FEB) assisted deposition. The three decoration techniques create distinctive, random surface features that can be used with Digital Image Correlation to provide full field maps of surface displacements at high magnifications. A series of experiments using a FEGSEM-FIB demonstrated the effectiveness of the three surface decoration techniques for FEGSEM imaging at magnifications from 2,000× to 60,000×. The precision of the image correlation is substantially enhanced by the surface decoration, with displacement standard deviations reduced to the 0.005–0.03 pixel range, depending on the patch size used. By means of an example application, the use of surface decoration for microscopic hole-drilling residual stress measurements within a FIB-SEM is presented. The same trends in DIC uncertainty observed in the analysis of the surface decoration patterns carried through to the example application. Guidelines are given for appropriate choice of decoration method to suit various practical applications. Content Type Journal Article Pages 1-12 DOI 10.1007/s11340-011-9568-y Authors B. Winiarski, School of Materials, University of Manchester, Manchester, M1 7HS UK G. S. Schajer, Department of Mechanical Engineering, University of British Columbia, Vancouver, BC, Canada P. J. Withers, School of Materials, University of Manchester, Manchester, M1 7HS UK Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    In order to predict the high-temperature deformation behavior of Al-Zn-Mg-Cu alloy, the hot compression tests were conducted in the strain rate range of (0.001–0.1)s −1 and the forming temperature range of (573–723) K. Based on the experimental results, Johnson-Cook model was found inadequate to describe the high-temperature deformation behavior of Al-Zn-Mg-Cu alloy. Therefore, a new phenomenological constitutive model is proposed, considering the coupled effects of strain, strain rate and forming temperature on the material flow behavior of Al-Zn-Mg-Cu alloy. In the proposed model, the material constants are presented as functions of strain rate. The proposed constitutive model correlates well with the experimental results confirming that the proposed model can give an accurate and precise estimate of flow stress for the Al-Zn-Mg-Cu alloy investigated in this study. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-011-9546-4 Authors Y. C. Lin, School of Mechanical and Electrical Engineering, Central South University, Changsha, 410083 China L.-T. Li, School of Mechanical and Electrical Engineering, Central South University, Changsha, 410083 China Y.-Q. Jiang, School of Mechanical and Electrical Engineering, Central South University, Changsha, 410083 China Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Cold expansion has proven to be an effective technique for extending the fatigue life of monolithic materials. Although fiber metal laminate materials show improved fatigue performance compared to their monolithic counterparts, the nucleation and growth of small cracks tends to occur early on in the fatigue life of the material, making acceptance of fiber metal laminates in aerospace more difficult. This work examined whether cold expansion could delay this process in fiber metal laminates and increase the fatigue life of these materials at the same time. The results showed that significant differences existed in the residual strain field between the mandrel exit and entry faces resulting in slower fatigue crack growth on the exit face, which also had higher residual strains in the region surrounding the cold expanded hole. Overall, cold expansion is effective at increasing the fatigue life of fiber metal laminate materials, but is less effective at delaying nucleation and growth of small cracks on the entry face. Content Type Journal Article Pages 1-13 DOI 10.1007/s11340-011-9553-5 Authors D. Backman, National Research Council Canada, Institute for Aerospace Research, Ottawa, ON, Canada E. A. Patterson, School of Engineering, University of Liverpool, Liverpool, UK Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The market demand for thicker complex shaped structural composite parts is increasing. Processes of the Liquid Composite Moulding (LCM) family, such as Resin Transfer Moulding (RTM) are considered to manufacture such parts. The first stage of the RTM process consists in the preforming of the part. During the pre-forming of multilayered reinforcements, frictions between the plies occur and need to be taken into account for the forming simulation. An experimental device designed to analyse the ply/ply and ply/tool frictions has been set up. The different set up steps of the device are described. First results are presented, which show the ply/ply friction behaviour for a glass plain weave fabric. A specific contact behaviour has been observed for dry reinforcement fabric in comparison to non-technical textiles. A honing effect classically observed in dry fabric testing has also been pointed out through cyclic experiments. It can be attributed to both fibre material abrasion and fibre reorganisation inside the yarn. Content Type Journal Article Pages 1-14 DOI 10.1007/s11340-011-9566-0 Authors G. Hivet, Laboratoire PRISME, UPRES EA 4229, Université d’Orléans, Polytech’Orléans, 8 rue Léonard de Vinci, 45072 Orléans Cedex 2, France S. Allaoui, Laboratoire PRISME, UPRES EA 4229, Université d’Orléans, Polytech’Orléans, 8 rue Léonard de Vinci, 45072 Orléans Cedex 2, France B. T. Cam, Laboratoire PRISME, UPRES EA 4229, Université d’Orléans, Polytech’Orléans, 8 rue Léonard de Vinci, 45072 Orléans Cedex 2, France P. Ouagne, Laboratoire PRISME, UPRES EA 4229, Université d’Orléans, Polytech’Orléans, 8 rue Léonard de Vinci, 45072 Orléans Cedex 2, France D. Soulat, Laboratoire PRISME, UPRES EA 4229, Université d’Orléans, Polytech’Orléans, 8 rue Léonard de Vinci, 45072 Orléans Cedex 2, France Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    A new shear-compression experiment for investigating the influence of hydrostatic pressure (mean stress) on the large deformation shear response of elastomers is presented. In this new design, a nearly uniform torsional shear strain is superposed on a uniform volumetric compression strain generated by axially deforming specimens confined by a stack of thin steel disks. The new design is effective in applying uniform shear and multiaxial compressive stress on specimens while preventing buckling and barreling during large deformation under high loads. By controlling the applied pressure and shear strain independently of each other, the proposed setup allows for measuring the shear and bulk response of elastomers at arbitrary states within the shear-pressure stress space. Thorough evaluation of the new design is conducted via laboratory measurements and finite element simulations. Practical issues and the need for care in specimen preparation and data reduction are explained and discussed. The main motivation behind developing this setup is to aid in characterizing the influence of pressure or negative dilatation on the constitutive shear response of elastomeric coating materials in general and polyurea in particular. Experimental results obtained with the new design illustrate the significant increase in the shear stiffness of polyurea under moderate to high hydrostatic pressures. Content Type Journal Article Pages 1-11 DOI 10.1007/s11340-011-9572-2 Authors M. Alkhader, Graduate Aerospace Laboratories, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA W. G. Knauss, Graduate Aerospace Laboratories, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA G. Ravichandran, Graduate Aerospace Laboratories, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    A novel high temperature ring-on-ring Kolsky bar technique was employed to investigate the dynamic equibiaxial flexural strength of borosilicate glass at temperatures ranging from room temperature up to 750°C. This technique provided non-contact heating of the glass specimen and prevented thermal shocks in the specimen. Experimental results at the loading rate of 22.5 MN/s showed significant temperature dependence on the flexural strength. To explore the mechanisms of this temperature effect, controlled surface cracks were introduced on the tensile surface of the glass specimens using a Vickers indentation technique. These surface cracks were then heat treated under the same thermal histories as those tested in the high temperature dynamic experiments. The evolution of crack morphologies at 200°C, 550°C and 650°C were examined. The results indicate that residual stress relaxation may play an important role in the strengthening below 200°C, while crack healing and blunting may account for the strengthening above 500°C. Content Type Journal Article Pages 1-9 DOI 10.1007/s11340-011-9549-1 Authors X. Nie, Schools of Aeronautics/Astronautics and Materials Engineering, Purdue University, West Lafayette, IN 47907, USA W. W. Chen, Schools of Aeronautics/Astronautics and Materials Engineering, Purdue University, West Lafayette, IN 47907, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Digital Image Correlation is used for controlling load shedding fatigue crack propagation. A specific algorithm is used to perform Stress Intensity Factors (SIFs) and crack length estimation in real time. Crack length measurements are validated by comparison with potential drop technique. SIFs results are compared with more common techniques using standard analytical formula considering confined plasticity at the crack tip. The proposed non-contact method is shown to be a powerful tool to control crack propagation. Content Type Journal Article Pages 1-11 DOI 10.1007/s11340-011-9552-6 Authors E. Durif, CNRS, INSA-Lyon, LaMCoS UMR5259, Université de Lyon, 69621 Villeurbanne Cedex, France J. Réthoré, CNRS, INSA-Lyon, LaMCoS UMR5259, Université de Lyon, 69621 Villeurbanne Cedex, France A. Combescure, CNRS, INSA-Lyon, LaMCoS UMR5259, Université de Lyon, 69621 Villeurbanne Cedex, France M. Fregonese, CNRS, INSA-Lyon, MATEIS UMR5510, Université de Lyon, 69621 Villeurbanne Cedex, France P. Chaudet, CNRS, INSA-Lyon, LaMCoS UMR5259, Université de Lyon, 69621 Villeurbanne Cedex, France Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    High temperature (298 K–573 K) and high strain rate (4000 s −1 ) compression experiments were performed on a cryomilled ultra-fine grained (UFG) Al-5083 using a modified Kolsky bar with a heating system designed to reduce “cold contact” time. The resulting stress strain curves show a reduction in strength of approximately 300 MPa at the highest temperature tested. This softening has been related to a thermally activated deformation mechanism. In addition, an experimental procedure was developed to investigate the microstructure evolution during the preheating, prior to mechanical loading, so as to identify the intrinsic mechanical response of the material at high temperatures. The results of this procedure are in good agreement with a TEM study on material that has been heated but not loaded. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-011-9565-1 Authors E. Huskins, Department of Mechanical Engineering, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA B. Cao, Department of Mechanical Engineering, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA B. Li, Department of Mechanical Engineering, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA K. T. Ramesh, Department of Mechanical Engineering, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Cracks are one of the most common types of damage occurring in engineering structures. A reliable nondestructive evaluation technique is essential to detect any possible damage at the initiation phase. Real fatigue closed-surface cracks are difficult to detect through visual inspection. Ultrasound has been widely used, but conventional contact ultrasonic inspection techniques are not suitable for couplant-sensitive structures. In addition, these techniques are generally laborious for large field structures and the inspection speed is relatively slow. We present a novel fully non-contact hybrid ultrasonic propagation imaging (UPI) system that uses laser ultrasonic scanning excitation and piezoelectric air-coupled sensing. Ultrasonic frequency tomography and wavelet-transformed ultrasonic propagation imaging algorithms are used to extract damage features. These features are used to perform a thorough diagnosis of damage. The system enables remote and fully non-contact automatic one-sided inspection for temporal reference-free damage evaluation, and is also applicable to in-field structures. Optimization provides improved performance of air-coupled transducers (ACTs) used as receivers for the hybrid UPI system, as shown by our experimental results. Surface crack evaluation results were analyzed on the basis of ease of damage visualization, accuracy of crack size estimation, and sensitivity. The proposed hybrid UPI system is sensitive enough to detect a real fatigue closed-surface micro-crack with size detection accuracy as high as 96%. We also show that the relation between the scanning interval and crack width affects damage visualization performance, and the accuracy and sensitivity of damage size estimation. Content Type Journal Article Pages 1-12 DOI 10.1007/s11340-011-9567-z Authors D. Dhital, Department of Aerospace Engineering and LANL-CBNU Engineering Institute Korea, Chonbuk National University, 567 Baekje-daero, 561-756, Deokjin-gu, Jeonju, Republic of Korea J. R. Lee, Department of Aerospace Engineering and LANL-CBNU Engineering Institute Korea, Chonbuk National University, 567 Baekje-daero, 561-756, Deokjin-gu, Jeonju, Republic of Korea Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    In order to determine the influence of internal interfaces on the material’s global mechanical behavior, the strength of single interfaces is of great interest. The experimental framework presented here enables quantitative measurements of the initiation and propagation of interfacial cracks on the microscale. Cantilever beams are fabricated by focused ion beam milling out of a bulk sample, with an interface of interest placed close to the fixed end of the cantilever. Additionally, a U-notch is fabricated at the location of the interface to serve as a stress concentrator for the initiation of the crack. The cantilevers are then mechanically deflected using a nanoindentation system for high resolution load-displacement measurements. In order to determine the onset and propagation of damage, the stiffness of the cantilevers is recorded by partial unloads during the test as well as by making use of a continuous stiffness technique. A finite element model is used to normalize the load and stiffness in order to establish the framework for comparisons between different interfaces. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-011-9530-z Authors D. Kupka, Institute of Materials Research, Materials Mechanics, Helmholtz-Zentrum Geesthacht, Max-Planck-Strasse 1, 21502 Geesthacht, Germany E. T. Lilleodden, Institute of Materials Research, Materials Mechanics, Helmholtz-Zentrum Geesthacht, Max-Planck-Strasse 1, 21502 Geesthacht, Germany Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    As an important factor in evaluating the safety of civil infrastructures, predictions of displacement become the basis for determining the decrease of structural performance and the degree of aging in general. It is, however, well known that it is not easy to measure the displacement response of civil infrastructures such as suspension bridges due to a lack of appropriate measurement techniques, despite the importance of measurements in the displacement response. Thus, as an alternative for predicting the displacement response indirectly, the conversion of the measured strain signal obtained using Fiber optic Bragg-Grating (FBG) sensors into the displacement response is suggested. In previous studies on the prediction of displacement response using FBG sensors, static displacement was mainly predicted. A known complication in the use of the measured strain signal to predict dynamic displacement is the fact that the measured strain signal includes higher modes, and that the predicted dynamic displacement can be inherently contaminated by broad-band noises. To overcome such a problem, a mode decomposition technique was used. This is a method that estimates the total displacement response combined with each displacement response about the major mode of the structure and the quasi-static displacement responses. In order to verify the suggested algorithm to predict the displacement responses from FBG strain signals, a model experiment and field tests were executed. Content Type Journal Article Pages 1-17 DOI 10.1007/s11340-011-9522-z Authors S.-J. Chang, Department of Civil and Environmental Engineering, Pusan National University, 30 Jangjeon-dong, Geumjeong-gu, Busan, 609–735 Republic of Korea N.-S. Kim, Department of Civil and Environmental Engineering, Pusan National University, 30 Jangjeon-dong, Geumjeong-gu, Busan, 609–735 Republic of Korea Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Mechanical properties of most metallic materials can be improved by reducing their grain size. One of the methods used to reduce the grain size even to the nanometer level is the severe plastic deformation processing. Equal Channel Angular Pressing (ECAP) is one of the most promising severe plastic deformation processes for the nanocrystallization of ductile metals. Nanocrystalline and ultrafine grained metals usually have significantly higher strength properties but lower tensile ductility compared to the coarse grained metals. In this work, the torsion properties of ECAP processed ultrafine grained pure 1070 aluminum were studied in a wide range of strain rates using both servohydraulic materials testing machines and Hopkinson Split Bar techniques. The material exhibits extremely high ductility in torsion and the specimens did not fail even after 300% of strain. Pronounced yield point behavior was observed at strain rates 500 s −1 and higher, whereas at lower strain rates the yielding was continuous. The material showed slight strain softening at the strain rate of 10 −4  s −1 , almost ideally plastic behavior at strain rates between 10 −3  s −1 and 500 s −1 , and slight but increasing strain hardening at strain rates higher than that. The tests were monitored using digital cameras, and the strain distributions on the surface of the specimens were calculated using digital image correlation. The strain in the specimen localized very rapidly after yielding at all strain rates, and the localization lead to the development of a shear band. At high strain rates the shear band developed faster than at low strain rates. Content Type Journal Article Pages 1-9 DOI 10.1007/s11340-011-9511-2 Authors M. Hokka, Department of Materials Science, Tampere University of Technology, P.O.B. 589, 33101 Tampere, Finland J. Kokkonen, Department of Materials Science, Tampere University of Technology, P.O.B. 589, 33101 Tampere, Finland J. Seidt, Department of Mechanical Engineering, The Ohio State University, Columbus, OH, USA T. Matrka, Department of Mechanical Engineering, The Ohio State University, Columbus, OH, USA A. Gilat, Department of Mechanical Engineering, The Ohio State University, Columbus, OH, USA V.-T. Kuokkala, Department of Materials Science, Tampere University of Technology, P.O.B. 589, 33101 Tampere, Finland Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Interfacial fracture is a critical issue for extensive applications of adhesively bonded structures to a variety of modern industries. Extensive global experimental tests have been conducted to measure the global behavior of adhesively bonded joint, such as ultimate load capacity and toughness. Recently, several studies have also been employed to characterize the local interfacial traction–separation laws. However, very few tests have investigated the dependency of the local interfacial constitutive laws on the adhesive thickness, particularly, under Mode-II loading conditions. In this work, six typical adhesive thicknesses (from 0.1 mm to 1.0 mm) are prepared for the bonded joints with a configuration of end notched flexure (ENF) specimen to realize the Mode-II fracture loading (shear fracture). With a recently developed analytical model, the global energy release rates of the ENF specimens are experimentally measured. Meanwhile, with the image analysis technique, the local slips between the two adherends are obtained. Finally, based on the J -integral theory, the local interfacial constitutive laws at different bondline thicknesses are obtained. Several experimental findings are reported in this work. This work may provide valuable baseline experimental data for the input in cohesive zone model (CZM) based analytical and numerical simulations. Content Type Journal Article Pages 1-11 DOI 10.1007/s11340-011-9507-y Authors G. Ji, Department of Mechanical Engineering, Louisiana State University, Baton Rouge, LA 70803, USA Z. Ouyang, Department of Mechanical Engineering, Southern University and A&M College, Baton Rouge, LA 70813, USA G. Li, Department of Mechanical Engineering, Louisiana State University, Baton Rouge, LA 70803, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Few shear test techniques exist that cover the range of strain rates from static to dynamic. In this work, a novel specimen geometry is presented that can be used for the characterisation of the shear behaviour of sheet metals over a wide range of strain rates using traditional tensile test devices. The main objectives during the development of the shear specimen have been 1) obtaining a homogeneous stress state with low stress triaxiality in the zone of the specimen subjected to shear and 2) appropriateness for dynamic testing. Additionally, avoiding premature specimen failure due to edge effects was aimed at. Most dimensional and practical constraints arose from the dynamic test in which the specimen is loaded by mechanical waves in a split Hopkinson tensile bar device. Design of the specimen geometry is based on finite element simulations using ABAQUS/Explicit. The behaviour of the specimen is compared with the more commonly used simple shear specimen with clamped grips. Advantages of the new technique are shown. The technique is applied to Ti6Al4V sheet. During the high strain rate experiments high speed photography and digital image correlation are used to obtain the local shear strain in the specimen. Comparison of experimental and numerical results shows good correspondence. Content Type Journal Article Pages 1-13 DOI 10.1007/s11340-011-9541-9 Authors J. Peirs, Department of Materials Science and Engineering, Ghent University, Technologiepark 903, 9052 Zwijnaarde (Ghent), Belgium P. Verleysen, Department of Materials Science and Engineering, Ghent University, Technologiepark 903, 9052 Zwijnaarde (Ghent), Belgium J. Degrieck, Department of Materials Science and Engineering, Ghent University, Technologiepark 903, 9052 Zwijnaarde (Ghent), Belgium Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    A novel approach to nanoscale broadband viscoelastic spectroscopy is presented. The proposed approach utilizes the recently developed modeling-free inversion-based iterative control (MIIC) technique to achieve accurate measurement of the material response to the applied excitation force over a broad frequency band. Scanning probe microscope (SPM) and nanoindenter have become enabling tools to quantitatively measure the mechanical properties of a wide variety of materials at nanoscale. Current nanomechanical measurement, however, is limited by the slow measurement speed: the nanomechanical measurement is slow and narrow-banded and thus not capable of measuring rate-dependent phenomena of materials. As a result, large measurement (temporal) errors are generated when material is undergoing dynamic evolution during the measurement. The low-speed operation of SPM is due to the inability of current approaches to (1) rapidly excite the broadband nanomechanical behavior of materials, and (2) compensate for the convolution of the hardware adverse effects with the material response during high-speed measurements. These adverse effects include the hysteresis of the piezo actuator (used to position the probe relative to the sample); the vibrational dynamics of the piezo actuator and the cantilever along with the related mechanical mounting; and the dynamics uncertainties caused by the probe variation and the operation condition. In the proposed approach, an input force signal with frequency characteristics of band-limited white-noise is utilized to rapidly excite the nanomechanical response of materials over a broad frequency range. The MIIC technique is used to compensate for the hardware adverse effects, thereby allowing the precise application of such an excitation force and measurement of the material response (to the applied force). The proposed approach is illustrated by implementing it to measure the frequency-dependent plane-strain modulus of poly(dimethylsiloxane) (PDMS) over a broad frequency range extending over 3 orders of magnitude (~1 Hz to 4.5 kHz). Content Type Journal Article Pages 1-13 DOI 10.1007/s11340-011-9547-3 Authors Z. Xu, Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA D. Tramp, Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA Q. Zou, Mechanical and Aerospace Engineering, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA P. Shrotriya, Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA P. Xie, School of Electrical Engineering, Yanshan University, Qinghuangdao, Hebei 066064, China Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Waves induced by impact initiate deformation mechanisms within a material that precede later flow. An impulse excites a cascade of deformation mechanisms starting with ultrafast and concluding with slower ones. In metals, brittle glasses and polycrystalline ceramics there are a combination of mechanisms with differing relaxation times that condition a loaded target. In the case of ballistic impact, once failure has occurred, long rod penetration can occur and the depth achieved within each target can be scaled with the deformation strengths recorded during the initial high pressure impulse. A review of material shock response and target preconditioning shows a correlation with the ballistic penetration of the target after loading. This indicates that the effect of an initial loading impulse upon material behaviour is a strong feature of the effects observed in many dynamic phenomena. Content Type Journal Article Pages 1-7 DOI 10.1007/s11340-011-9548-2 Authors N. K. Bourne, AWE, Aldermaston, Reading, RG7 4PR UK Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Polymeric composite sandwich structures, often manufactured using a thick foam core material and thin composite facings, are of significant interest in naval applications. This paper summarizes the coupled effect of sea water and low temperature on the mechanical properties of closed cell polymeric H100 foam core material. The study considers the effects of harsh sea environmental conditions on the fracture and deformation behavior of such a foam material under complex loading conditions that include tension, torsion, compression, and true-triaxial stress paths. Mechanical testing techniques are developed using coupon samples of suitable geometry that minimize grip effects on these low density complex foam materials, along with information associated with the observed cross-anisotropic behavior. Interfacial delamination fracture response for the sandwich structures due to the combined effects of sea water and low temperature are evaluated and the associated degradation in critical energy release rate for delamination is found to be substantial. Experimental data for H100 foam cores associated with moisture induced expansional strains are also included. Content Type Journal Article Pages 1-12 DOI 10.1007/s11340-011-9564-2 Authors A. Siriruk, Civil and Environmental Engineering, University of Tennessee, 223 Perkins Hall, Knoxville, TN 37996-2010, USA D. Penumadu, Civil and Environmental Engineering, University of Tennessee, 223 Perkins Hall, Knoxville, TN 37996-2010, USA A. Sharma, Civil and Environmental Engineering, University of Tennessee, 223 Perkins Hall, Knoxville, TN 37996-2010, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The deformation and failure response of composite sandwich beams and panels under low velocity impact was reviewed and discussed. Sandwich facesheet materials discussed are unidirectional and woven carbon/epoxy, and woven glass/vinylester composite laminates; sandwich core materials investigated include four types of closed cell PVC foams of various densities, and balsa wood. Sandwich beams were tested in an instrumented drop tower system under various energy levels, where load and strain histories and failure modes were recorded for the various types of beams. Peak loads predicted by spring-mass and energy balance models were in satisfactory agreement with experimental measurements. Failure patterns depend strongly on the impact energy levels and core properties. Failure modes observed include core indentation/cracking, facesheet buckling, delamination within the facesheet, and debonding between the facesheet and core. In the case of sandwich panels, it was shown that static and impact loads of the same magnitude produce very similar far-field deformations. The induced damage is localized and is lower for impact loading than for an equivalent static loading. The load history, predicted by a model based on the sinusoidal shape of the impact load pulse, was in agreement with experimental results. A finite element model was implemented to capture the full response of the panel indentation. The investigation of post impact behavior of sandwich structures shows that, although impact damage may not be readily visible, its effects on the residual mechanical properties of the structure can be quite detrimental. Content Type Journal Article Pages 1-11 DOI 10.1007/s11340-011-9479-y Authors I. M. Daniel, Robert R. McCormick School of Engineering and Applied Science, Northwestern University, Evanston, IL 60208, USA J. L. Abot, The Catholic University of America, Washington, DC 20064, USA P. M. Schubel, Aerospace Corporation, El Segundo, CA 90245, USA J.-J. Luo, Illinois Tool Works, Glenview, IL 60026, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    This paper describes the measurement of average strain, strain distribution and vibration of a cantilever beam made of Carbon Fiber Reinforced Plastics (CFRP), using a single Fibre Bragg Grating (FBG) sensor mounted on the beam surface. Average strain is determined from the displacement of the peak wavelength of reflected spectrum from the FBG sensor. Two unstrained reference FBG sensors were used to compensate for temperature drift. Measured strains agree with those measured by a resistance foil strain gauge attached to the sample. Stress distributions are measured by monitoring the variation in the full width at half maximum (FWHM) values of the reflected spectrum, using a proposed optical analytical model, described in the paper. FWHM values were measured for both the cantilever test beam and for a reference beam, loaded using a four-point bending rig. The trend of the stress distribution for the test beam matches with our analytical model, however with a relatively large noise present in the experimentally determined data. The vibration of a cantilever beam was measured by temporal analysis of the peak reflection wavelength. This technique is very stable as measurements are not affected by variations in the signal amplitude. Finally an application of FBG sensors for damage detection of CFRP plates, by measuring the natural frequency, is demonstrated. With small defects of different sizes applied to the CFRP plate, the natural frequency decreased with damage size. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-011-9467-2 Authors Y. Mizutani, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2600 GB Delft, The Netherlands R. M. Groves, Optical Non-Destructive Testing Laboratory, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2600 GB Delft, The Netherlands Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Pinned (bolted) joints are an extremely important, but difficult to analyze, structural or mechanical element. They are a class of inverse problems in which the stresses at the pin/hole interface are typically unknown. Moreover, stresses vary non-linearly with applied load. Failures of mechanical or structural systems frequently initiate at connections. Although almost always present, many stress analyses of such mechanical connections ignore friction for simplicity. The stresses are evaluated here in an aluminum connector using a series solution of an Airy stress function, the coefficients being evaluated from known boundary tractions (near, but not including the contact region on the hole) and photoelastically measured data obtained from a bonded birefringent coating. Both friction and pin/hole clearance are accounted for, and individual stresses are evaluated full-field, including on the contact boundary of the hole. Content Type Journal Article Pages 1-12 DOI 10.1007/s11340-011-9477-0 Authors B. E. Foust, Manitowoc Cranes, Manitowoc, WI 54220, USA J. R. Lesniak, Stress Photonics, Madison, WI 53716, USA R. E. Rowlands, University of Wisconsin-Madison, Madison, WI 53701, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description: Advanced Imaging Methods Content Type Journal Article Pages 1-3 DOI 10.1007/s11340-011-9469-0 Authors M. A. Sutton, Department of Mechanical Engineering, University of South Carolina, 300 Main Street, Room A129, Columbia, SC 29208, USA F. Hild, ENS Cachan, LMT Cachan, 61 Avenue du Président Wilson, Cachan Cedex, 94235 France H. Jin, Sandia National Laboratories, Microsystems and Mechanics Materials, 7011 East Ave, MS 9409, Livermore, CA 94551, USA X. Li, Department of Mechanical Engineering, University of South Carolina, 300 Main Street, Columbia, SC 29208, USA M. M. Grédiac, Universite’ Blaise Pascal-IFMA, Laboratoiré de Mecanique et Ingenieries, Campus des Cézeaux, BP 275, Aubiére Cedex, 63175 France Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Increasing interest in the use of digital image correlation (DIC) for full-field surface shape and deformation measurements has led to an on-going need for both the development of theoretical formulae capable of providing quantitative confidence margins and controlled experiments for validation of the theoretical predictions. In the enclosed work, a series of stereo vision experiments are performed in a manner that provides sufficient information for direct comparison with theoretical predictions using formulae developed in Part I. Specifically, experiments are performed to obtain appropriate optimal estimates and the uncertainty margins for the image locations/displacements, 3-D locations/displacements and strains when using the method of subset-based digital image correlation for image matching. The uncertainty of locating the 3-D space points using subset-based pattern matching is estimated by using theoretical formulae developed in Part I and the experimentally defined confidence margins for image locations. Finally, the uncertainty in strains is predicted using formulae that involves both the variance and covariance of intermediate variables during the strain calculation process. Results from both theoretical predictions and the experimental work show the feasibility and accuracy of the predictive formulae for estimating the uncertainty in the stereo-based deformation measurements. Content Type Journal Article Pages 1-19 DOI 10.1007/s11340-010-9450-3 Authors X.-D. Ke, Correlated Solutions Inc, 120 Kaminer Way Parkway Suite A, Columbia, SC 29210, USA H. W. Schreier, Correlated Solutions Inc, 120 Kaminer Way Parkway Suite A, Columbia, SC 29210, USA M. A. Sutton, Department of Mechanical Engineering, University of South Carolina, 300 South Main Street, Columbia, SC 29208, USA Y. Q. Wang, Department of Mechanical Engineering, University of South Carolina, 300 South Main Street, Columbia, SC 29208, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Using the basic equations for stereo-vision with established procedures for camera calibration, the error propagation equations for determining both bias and variability in a general 3D position are provided. The results use recent theoretical developments that quantified the bias and variance in image plane positions introduced during image plane correspondence identification for a common 3D point (e.g., pattern matching during measurement process) as a basis for preliminary application of the developments for estimation of 3D position bias and variability. Extensive numerical simulations and theoretical analyses have been performed for selected stereo system configurations amenable to closed-form solution. Results clearly demonstrate that the general formulae provide a robust framework for quantifying the effect of various stereo-vision parameters and image-plane matching procedures on both the bias and variance in an estimated 3D object position. Content Type Journal Article Pages 1-18 DOI 10.1007/s11340-010-9449-9 Authors Y.-Q. Wang, Department of Mechanical Engineering, University of South Carolina, 300 South Main Street, Columbia, SC 29208, USA M. A. Sutton, Department of Mechanical Engineering, University of South Carolina, 300 South Main Street, Columbia, SC 29208, USA X.-D. Ke, Correlated Solutions Inc, 126 Kaminer Way Parkway Suite 1A, Columbia, SC 29210, USA H. W. Schreier, Correlated Solutions Inc, 126 Kaminer Way Parkway Suite 1A, Columbia, SC 29210, USA P. L. Reu, Sandia National Laboratory, PO Box 5800, Albuquerque, NM 87185, USA T. J. Miller, Sandia National Laboratory, Mechanical Environments, Dept. 1534. MS-1139, P.O. Box 5800, Albuquerque, NM 87185-1139, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Dynamic compressive behavior of dry quartz sand (Quikrete #1961 sand quarried in Pensacola, FL) under confinement was characterized using a modified long split Hopkinson pressure bar (SHPB). Sand grains were confined inside a hollow cylinder of hardened steel and capped by cemented tungsten carbide cylindrical rods. This assembly was subjected to repeated shaking to consolidate sand to attain precise bulk mass densities. It is then sandwiched between incident and transmission bars on SHPB for dynamic compression measurements. Sand specimens of five initial mass densities, namely, 1.51, 1.57, 1.63, 1.69, and 1.75 g/cm 3 , were characterized at high strain rates near 600 s −1 , to determine the volumetric and deviatoric behaviors through measurements of both axial and transverse responses of a cylindrical sand sample under confinement. The stress–strain relationship was found to follow a power law relationship with the sand initial bulk density, with an exponent of 8.25, indicating a behavior highly sensitive to mass density. The energy absorption density and compressibility of sand were determined as a function of axial stress. Content Type Journal Article Pages 1-12 DOI 10.1007/s11340-011-9475-2 Authors H. Luo, Department of Mechanical Engineering, the University of Texas at Dallas, Richardson, TX 75080, USA H. Lu, Department of Mechanical Engineering, the University of Texas at Dallas, Richardson, TX 75080, USA W. L. Cooper, Air Force Research Laboratory, Eglin Air Force Base, Valparaiso, FL 32542, USA R. Komanduri, School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, OK 74078, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The real-time measurement of the surface acoustic wave (SAW) was carried out during the fatigue testing of the bolted joints of aluminum alloy plates with a frequency of 0.001 Hz. SAW distributions in the bolted region were compared with those obtained by the synchronized measurement, in which the ultrasonic wave was generated in synchronization with a loading cycle in the fatigue testing with a frequency of 10 Hz. At different numbers of fatigue cycles, the intensity of the reflection from the fatigue crack obtained by the real-time measurement was in good agreement with that obtained by the synchronized measurement. In the real-time measurement, the reflection intensity and profile changed with the stress level in a loading cycle, which were in good agreement with those obtained by the synchronized SAW measurement. From these results, it was confirmed that the SAW distributions obtained by the synchronized measurement is coincident with ones obtained by the real-time measurement in one loading cycle, and is not influenced by the measurement conditions. Content Type Journal Article Pages 1-6 DOI 10.1007/s11340-011-9473-4 Authors S. Wagle, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-Ku, Saitama, 338-8570 Japan H. Kato, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-Ku, Saitama, 338-8570 Japan Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description: Erratum to: Identification of Interaction Pressure Between Structure and Explosive with Inverse Approach Content Type Journal Article Pages 1-1 DOI 10.1007/s11340-011-9474-3 Authors S. Xu, Department of Mechanical Engineering, Georgia Southern University, Statesboro, GA 30458, USA V. Tiwari, Department of Mechanical Engineering, University of South Carolina, Columbia, SC 29208, USA X. Deng, Department of Mechanical Engineering, University of South Carolina, Columbia, SC 29208, USA M. A. Sutton, Department of Mechanical Engineering, University of South Carolina, Columbia, SC 29208, USA W. L. Fourney, Department of Aerospace Engineering, University of Maryland, College Park, MD 20742, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    A novel Kolsky torsion bar technique is developed and successfully utilized to characterize the high strain rate shear response of a rate-independent end-linked polydimethylsiloxane (PDMS) gel rubber with a shear modulus of about10 KPa. The results show that the specimen deforms uniformly under constant strain rate and the measured dynamic shear modulus follows reasonably well the trend determined by dynamic mechanical analysis (DMA) at lower strain rates. For comparison, Kolsky compression bar experiments are also performed on the same gel material with annular disk specimens. The dynamic moduli obtained from compression experiments, however, are an order of magnitude higher than those obtained by the torsional technique, due to the pressure caused by the radial inertia and end constraints. Content Type Journal Article Pages 1-8 DOI 10.1007/s11340-011-9481-4 Authors X. Nie, School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA R. Prabhu, School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA W. W. Chen, School of Aeronautics and Astronautics and School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA J. M. Caruthers, School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA T. Weerasooriya, US Army Research Laboratory, Aberdeen Proving Ground, Aberdeen, MD 21005, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The paper aims at characterizing some key features of the mechanical behavior of two semi-crystalline polymers in weakly pressurized hydrogen. The opportunity to use hydrogen as an alternative energy strengthens the need for reliable data on possible coupling effects between gas diffusion and mechanical properties, especially for safe design purpose. However, such effects have not been really quantified in polymers. In the present study, a hydraulic testing machine has been fitted with a pressure hydrogen chamber, and three major aspects of the mechanical behavior have been investigated in polyethylene and polyamide 11: monotonic tension, long-term creep (based on a time-temperature superposition principle) and ductile fracture (evaluated from an essential work of fracture method). Suitable protocols have been defined to take into account specificity like temperature and pressure history dependence and gas saturation kinetics of the sample. Content Type Journal Article Pages 1-11 DOI 10.1007/s11340-011-9484-1 Authors S. Castagnet, Département de Physique et Mécanique des Matériaux, Institut P’ (UPR CNRS 3346), CNRS-ENSMA-Université de Poitiers, ENSMA, 1 Avenue Clément Ader, BP 40109, 86961 Futuroscope cedex, France J.-C. Grandidier, Département de Physique et Mécanique des Matériaux, Institut P’ (UPR CNRS 3346), CNRS-ENSMA-Université de Poitiers, ENSMA, 1 Avenue Clément Ader, BP 40109, 86961 Futuroscope cedex, France M. Comyn, Département de Physique et Mécanique des Matériaux, Institut P’ (UPR CNRS 3346), CNRS-ENSMA-Université de Poitiers, ENSMA, 1 Avenue Clément Ader, BP 40109, 86961 Futuroscope cedex, France G. Benoît, Département de Physique et Mécanique des Matériaux, Institut P’ (UPR CNRS 3346), CNRS-ENSMA-Université de Poitiers, ENSMA, 1 Avenue Clément Ader, BP 40109, 86961 Futuroscope cedex, France Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Understanding the radiation embrittlement of reactor pressure vessel (RPV) steels is required to be able to operate safely a nuclear power plant or to extend its lifetime. The mechanical properties degradation is partly due to the clustering of solute under irradiation. To gain knowledge about the clustering process, a Fe−1.1 Mn−0.7 Ni (at.%) alloy was irradiated in a test reactor at two fluxes of 0.15 and 9 ×10 17 n E  〉 1 MeV .m  − 2 .s  − 1 and at increasing doses from 0.18 to 1.3 ×10 24 n E  〉 1 MeV .m  − 2 at 300°C. Atom probe tomography (APT) experiments revealed that the irradiation promotes the formation in the α iron matrix of Mn/Mn and/or Ni/Ni pair correlations at low dose and Mn–Ni enriched clusters at high dose. These clusters dissolve partially after a thermal treatment at 400°C. Based on a comparison with thermodynamic calculations, we show that the solute clustering under irradiation can just result from an induced mechanism. Content Type Journal Article Pages 1-6 DOI 10.1007/s11340-011-9476-1 Authors E. Meslin, Service de Recherches de Métallurgie Physique, CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France B. Radiguet, Groupe de Physique des Matériaux UMR-CNRS 6634, Equipe de Recherche Technologique No. 1000, Université de Rouen, B.P. 12, 76801 Saint Etienne du Rouvray, France P. Pareige, Groupe de Physique des Matériaux UMR-CNRS 6634, Equipe de Recherche Technologique No. 1000, Université de Rouen, B.P. 12, 76801 Saint Etienne du Rouvray, France C. Toffolon, Service de Recherches en Métallurgie Appliquée, CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France A. Barbu, Service de Recherches de Métallurgie Physique, CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Generally, the complex behaviour of the disc of the temporomandibular joint (TMJ) cannot be adequately represented using linear elastic or linear viscoelastic models. Since the disc is regularly subjected to large strain and stress levels, the study of its non-linear response under compression is of practical interest, especially for analysis of medical dysfunctions. With this aim, relaxation and creep tests were carried out using round specimens of diameters ranging between 4 and 6 mm cut off from the central, anterior, posterior, lateral and medial zones of porcine discs to investigate the regional mechanical properties differences. The experimental data results are fitted using Prony series, based on generalized Maxwell and Kelvin models, allowing the relaxation and creep moduli to be represented, respectively, as a function of the strain and stress. The results show that the non-linear material behaviour of this biological tissue is properly described by the proposed models, to be considered subsequently in numerical calculations. Content Type Journal Article Pages 1-6 DOI 10.1007/s11340-011-9465-4 Authors M. J. Lamela, Department of Construction and Manufacturing Engineering, University of Oviedo, Campus de Viesques, 33203 Gijón, Spain Y. Prado, Department of Construction and Manufacturing Engineering, University of Oviedo, Campus de Viesques, 33203 Gijón, Spain P. Fernández, Department of Construction and Manufacturing Engineering, University of Oviedo, Campus de Viesques, 33203 Gijón, Spain A. Fernández-Canteli, Department of Construction and Manufacturing Engineering, University of Oviedo, Campus de Viesques, 33203 Gijón, Spain E. Tanaka, Department of Orthodontics and Dentofacial Orthopedics, University of Tokushima, 3-18-15 Kuramoto-cho, Tokushima, 770-8504 Japan Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The acrylic elastomer membrane VHB 4910 is a material widely used for applications as Dielectric Elastomer Actuators DEA. For suitable actuation performance however, it is necessary to pre-strain the very compliant membrane. This reduces the lifetime of DEA due to early failure of the tensioned membrane. Interpenetrating Polymer Network Reinforced Acrylic Elastomers (IPN) are produced by introducing a curable additive into the pre-strained acrylic elastomer membrane. While curing at elevated temperature, the additive forms a second polymeric network that supports part of the pre-strain in the acrylic membrane. This leads to a free standing material that combines the actuation performance of pre-strained VHB 4910 with an excellent long-term reliability. This work presents a detailed mechanical characterization of acrylic IPN membranes. To reduce the experimental effort required to characterize the nonlinear elastic behavior, we developed a unique specimen design that enables the assessment of uni- and biaxial stress states within one experiment. Slight changes in the material composition of IPN-membranes lead to substantial variations in their mechanical properties. The extraction of material behavior in different kinematic states within a single sample thus reduces the uncertainty on the determination of constitutive models. An extensive experimental campaign was carried out involving uniaxial and equibiaxial tension and relaxation. Image based local deformation measurements and iterative finite element calculations were applied to derive constitutive model parameters that describe the mechanical response in a wide range of planar strain and strain rate. Content Type Journal Article Pages 1-13 DOI 10.1007/s11340-010-9462-z Authors A. Schmidt, Swiss Federal Laboratories for Materials Testing and Research (Empa), 8600 Dübendorf, Switzerland A. Bergamini, Swiss Federal Laboratories for Materials Testing and Research (Empa), 8600 Dübendorf, Switzerland G. Kovacs, Swiss Federal Laboratories for Materials Testing and Research (Empa), 8600 Dübendorf, Switzerland E. Mazza, Swiss Federal Laboratories for Materials Testing and Research (Empa), 8600 Dübendorf, Switzerland Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The paper deals with the parameter sensitivity analysis of a passenger/seat model that can be used for ride comfort assessments. The final aim is to produce a comprehensive framework for enabling vehicle seat designers to develop comfortable (and healthy) seats, especially for those people who spend their lives while working on vehicles. In this paper a seated passenger proprietary model has been proposed and validated either by comparing it with a mathematical model derived by means of commercial software, either by experimental activities. On the basis of the validated model a sensitivity analysis has been performed, aiming to identify the key parameters affecting the ride comfort. A total of 47 parameters were accounted for. Many parameters seem relevant to describe the ride comfort of a seated road vehicle passenger. The most important conclusion of the research is that the parameters referring to posture have proved to influence ride comfort to a great extent. Other relevant but less important parameters are: the stiffness and damping of the seat, the geometry of the seat, the size and inertia properties of the body segments, and the stiffness and damping of the different parts of the human body. Different running conditions have been considered, i.e. vehicle passing over cleats or running on a randomly profiled road. Different running conditions influence differently the ride comfort, so care has to be used when performing either experimental or numerical simulations. Content Type Journal Article Pages 1-13 DOI 10.1007/s11340-010-9460-1 Authors M. Brogioli, Department of Mechanical Engineering, Politecnico di Milano, Via La Masa 1, Milan, Italy M. Gobbi, Department of Mechanical Engineering, Politecnico di Milano, Via La Masa 1, Milan, Italy G. Mastinu, Department of Mechanical Engineering, Politecnico di Milano, Via La Masa 1, Milan, Italy M. Pennati, Department of Mechanical Engineering, Politecnico di Milano, Via La Masa 1, Milan, Italy Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Ares I-X is a flight test vehicle developed by NASA to demonstrate a new class of crew launch vehicle. For this first flight test, the first stage was a four segment solid rocket booster with mass simulators used to represent the other sections of the Ares I vehicle. Although this vehicle is significantly simpler than the Ares I, model calibration was required for the finite element model used in loads analysis and flight control evaluations before its maiden flight. The process of calibrating models involves updating parameters and reconciling predictions with test data. This work presents a probabilistic approach to the calibration process. The approach uses Analysis of Variance (ANOVA) for parameter sensitivity, nonlinear optimization to minimize the error between test and analysis, and multiple FEM models to bound the system response and to assess the probability of finding a reconciling solution. To reduce the computational burden associated with ANOVA, response surface models are used in lieu of computationally intensive finite element solutions. Uncertainty in the parameters and their effect on the frequency response function is studied in terms of Principal Values of the frequency response functions. Uncertainty bounds of the principal values are established across multiple models to allow one to determine the probability of finding a solution that reconciles analysis with test results. Results from applying this model calibration process to the Ares I-X project are described. Findings presented in the paper confirmed that the baseline model used for pre-flight assessments was within the acceptable range established for guidance and control. Content Type Journal Article Pages 1-13 DOI 10.1007/s11340-010-9456-x Authors L. G. Horta, NASA Langley Research Center, MS 230, Hampton, VA 23681, USA M. C. Reaves, NASA Langley Research Center, MS 230, Hampton, VA 23681, USA R. D. Buehrle, NASA Langley Research Center, MS 434, Hampton, VA 23681, USA J. D. Templeton, NASA Langley Research Center, MS 434, Hampton, VA 23681, USA D. R. Lazor, NASA Marshall Space Flight Center, ET40, Huntsville, AL 35812, USA J. L. Gaspar, NASA Langley Research Center, MS 434, Hampton, VA 23681, USA R. A. Parks, NASA Marshall Space Flight Center, ET40, Huntsville, AL 35812, USA P. A. Bartolotta, NASA Glenn Research Center, 49-B, Cleveland, OH 44135, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description: Erratum to: Experimental Investigation on Mechanical Behavior of Coarse Marble Under Six Different Loading Paths Content Type Journal Article Pages 1-1 DOI 10.1007/s11340-010-9461-0 Authors S.Q. Yang, State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, 221008 People’s Republic of China H.W. Jing, State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, 221008 People’s Republic of China Y.S. Li, State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, 221008 People’s Republic of China L.J. Han, State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, 221008 People’s Republic of China Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Asphalt binders are common construction materials, however due to time- and temperature- dependence, their mechanical properties are often difficult to characterize. Several standard tests methods exist to describe their complex behavior. This paper presents an exploratory feasibility study of a flat-tip indentation testing to analyze the linear viscoelastic properties of asphalt binders. Depth-sensing indentation testing has been extensively used to characterize the properties of many engineering materials, however the applications to asphalt binders are very limited. This paper presents a simple solution for the creep compliance in tension derived for flat-tipped indenter. This solution was verified with the Finite Element Analysis and then applied to the experimental results from the indentation testing performed on one typical unmodified asphalt binder. The testing was conducted at three different low temperatures and under three different creep load levels to verity the linearity of the response, and to evaluate the robustness and applicability of the indentation method. Furthermore, the creep compliance functions determined from the indentation testing were compared with a more traditional 3-point bending experiments. The results show that there is a non-uniform discrepancy between the two testing methods, most likely due to nonlinear behavior of the asphalt binder at higher temperatures and micro-damage of the binder samples at lower temperatures. Other possible sources of error between indentation and 3-point bending are problems determining the initial tip-specimen contact surface and possible tip-specimen adhesion. It is concluded that flat-tipped indentation at low temperatures should be performed at lower load levels to avoid excessive stress concentrations that leads to micro-damage and nonlinear response of asphalt binders. Alternatively, asphalt binders at low temperatures could be evaluated using different indenter geometries, such as spherical or pyramidal, using corresponding parameter interpretation procedures. Content Type Journal Article Pages 1-13 DOI 10.1007/s11340-011-9464-5 Authors A. Zofka, Department of Civil and Environmental Engineering, University of Connecticut, 261 Glenbrook Road Unit 2037, Storrs, CT 06269-2037 USA D. Nener-Plante, Department of Civil and Environmental Engineering, University of Connecticut, 261 Glenbrook Road Unit 2037, Storrs, CT 06269-2037 USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    An orthotropic polymeric foam with transverse isotropy (Divinycell H250) used in composite sandwich structures was characterized at various strain rates. Uniaxial experiments were conducted along principal material axes as well as along off-axis directions under tension, compression, and shear to determine engineering constants, such as Young’s and shear moduli. Uniaxial strain experiments were conducted to determine mathematical stiffness constants, i. e., C ij . An optimum specimen aspect ratio for these tests was selected by means of finite element analysis. Quasi-static and intermediate strain rate tests were conducted in a servo-hydraulic testing machine. High strain rate tests were conducted using a split Hopkinson Pressure Bar system built for the purpose using polymeric (polycarbonate) bars. The polycarbonate material has an impedance that is closer to that of foam than metals and results in lower noise to signal ratios and longer loading pulses. It was determined by analysis and verified experimentally that the loading pulses applied, propagated along the polycarbonate rods at nearly constant phase velocity with very low attenuation and dispersion. Material properties of the foam were obtained at three strain rates, quasi-static (10 −4 s −1 ), intermediate (1 s −1 ), and high (10 3 s −1 ) strain rates. A simple model proposed for the Young’s modulus of the foam was in very good agreement with the present and published experimental results. Content Type Journal Article Pages 1-9 DOI 10.1007/s11340-011-9466-3 Authors I. M. Daniel, Robert R. McCormick School of Engineering and Applied Science, Northwestern University, Evanston, IL 60208, USA J.-M. Cho, Hyundai Motor Company, Seoul, Korea Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The objective of this paper is to explore both grid method and Digital Image Correlation (DIC) technique for microscale and discontinuous displacement measurements, such as those associated with crack tips. First, the principle of the grid method is revisited. The grid method and DIC technique are then applied to computer generated images to calculate the displacement field around crack tips. Finally, the grid method is applied to actual experimental images of fracture tests which are conducted inside a Scanning Electron Microscope (SEM) chamber. A new technique is developed to generate microscale pattern that is suitable for both grid method and DIC technique. The displacement fields calculated from grid method are compared with those from DIC technique to identify the strengths and weaknesses of each technique for the microscale and discontinuous displacement measurements. It has been determined that grid method can obtain data closer to the discontinuity than DIC; however, DIC produces smoother displacement fields at the far field. Using this new pattern generation technique, both grid method and DIC technique can be applied to the fracture test at the microscale to complement with each other to achieve the best experiment results. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-010-9459-7 Authors H. Jin, Mechanics of Materials, Sandia National Laboratories California, Livermore, CA USA S. Haldar, Department of Mechanical Engineering, University of Maryland, College Park, MD USA H. A. Bruck, Department of Mechanical Engineering, University of Maryland, College Park, MD USA W.-Y. Lu, Mechanics of Materials, Sandia National Laboratories California, Livermore, CA USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Double Torsion (DT) is a powerful testing technique for fracture mechanics characterisation of brittle materials as, in principle, it provides a crack length independent test configuration. However, several corrections have been proposed to address variations of experimental results reported from various laboratories. These correction factors address the validity of the DT configuration and its crack length independent stress intensity. Never the less, there seems to be no consensus in literature on the various corrections and the reason of reported variations. This paper presents firstly a critical review of the DT technique, followed by proposed corrections through an experimental analysis using the proposed corrections, a Finite Element model of the geometry and the use of Digital Image Correlation to measure out-of-plane surface deformations. It focuses on the validity of the constant stress intensity regime and the independence of crack length in a critical evaluation using Polymethylmethacrylate test specimens. Assessment of three un-grooved specimen geometry configurations demonstrated the apparent regime of approximately constant stress intensity, although a small but clear dependence of the stress intensity on crack length was observed in all specimen configurations. This dependence is attributable to significant load-point deflections and out-of plane deformations that are not accounted for in the DT analysis. Revisions of the proposed analysis methodologies show that a crack length independent specimen geometry can be achieved, however at the cost of less accurate data. Reliable and accurate data can be achieved with a DT testing configuration using an optimum specimen configuration. Content Type Journal Article Pages 1-16 DOI 10.1007/s11340-011-9468-1 Authors T. H. Becker, Department of Mechanical Engineering, University of Cape Town, Cape Town, South Africa T. J. Marrow, Department of Materials, University of Oxford, Oxford, UK R. B. Tait, Department of Mechanical Engineering, University of Cape Town, Cape Town, South Africa Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Advances using optical fibres as sensors may represent an important contribution for development of minimally invasive techniques in biomedical and biomechanical applications. Concerning spine injuries, intervertebral disc (IVD) degeneration is a major clinical issue since it represents gross structural disruption and it is irreversible. Measuring biomechanical parameters of the IVD should contribute for better understanding on its mechanical response to external applied forces. The purpose of this study was to explore the potential of a Fibre Bragg Grating (FBG) sensor to measure strain caused by bulging of the intervertebral disc under axial compression. Disc bulging is a consequence of IVD compression and a technique to register this behaviour is addressed in this study. Needle-mounted sensors were already used to measure IVD pressure in cadaveric material. In this study we also explored the possibility of using needles only for sensor guiding and positioning leaving sensor directly in contact with the IVD material. An ex vivo porcine dorsal functional spinal unit was instrumented with a FBG sensor and submitted to axial compression. Results suggest the sensor’s ability to measure strain response to load. Bulging of the annulus fibrosus as a consequence of axial compression was confirmed using the FBG sensor. Hysteresis and viscoelastic behaviour were observable suggesting that energy is dissipated by the deformation of the annulus and that unloading time was insufficient for disc recovery. Nevertheless the relatively low strain sensitivity of the sensor as well as signal artefacts caused by transverse loading may constitute a problem in the analysis and interpretation of strain data. The technique may not be suitable for measurement of physiologic bulging being more indicative of the radial force exerted by the annulus. Content Type Journal Article Pages 1-5 DOI 10.1007/s11340-011-9470-7 Authors P. Roriz, Department of Mechanical Engineering, University of Aveiro, 3810-193 Aveiro, Portugal I. Abe, Physics Department, University of Aveiro, 3810-193 Aveiro, Portugal M. Schiller, Physics Department, University of Aveiro, 3810-193 Aveiro, Portugal J. Gabriel, Ohio Orthopaedics & Sports Medicine, Inc, 301 West Wallace Street, Findlay, OH 45840, USA J. Simões, Department of Mechanical Engineering, University of Aveiro, 3810-193 Aveiro, Portugal Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Natural materials (e.g. nacre, bone, and spider silk) exhibit unique and outstanding mechanical properties. This performance is due to highly evolved hierarchical designs. Building a comprehensive understanding of the multi-scale mechanisms that enable this performance represents a critical step toward realizing strong and tough bio-inspired materials. This paper details a multi-scale experimental investigation into the toughening mechanisms in natural nacre. By applying extended digital image correlation and other image processing techniques, quantitative information is extracted from otherwise prodominantly qualitative experiments. In situ three point bending fracture tests are performed to identify and quantify the toughening mechanisms involved during the fracture of natural nacre across multiple length scales. At the macro and micro scales, fracture tests performed in situ with a macro lens and optical microscope enable observation of spreading of damage outward from the crack tip. This spreading is quantified using an iso-contour technique to assess material toughness. At the nanoscale, fracture tests are performed in situ an atomic force microscope to link the larger-scale damage spreading to sliding within the tablet-based microstructure. To quantify the magnitude of sliding and its distribution, images from the in situ AFM fracture tests are analyzed using new algorithms based on digital image correlation techniques which allow for discontinuous displacement fields. Ultimately, this comprehensive methodology provides a framework for broad experimental investigations into the failure mechanisms of bio- and bio-inspired materials. Content Type Journal Article Pages 1-17 DOI 10.1007/s11340-011-9463-6 Authors D. Grégoire, Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA O. Loh, Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA A. Juster, Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA H. D. Espinosa, Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    In the present work, shear-compression specimen was successfully employed to study the shear flow behavior of AZ31 magnesium alloy at high temperatures and in quasi-static regime. The loading process of shear-compression testing was simulated using ABAQUS software. This was carried out in the temperature range of 250–450°C and displacement rates of 1.5, 15 and 150 mm/min. In addition, to validate the numerical simulation results, the shear compression specimens were also compressed experimentally at the same conditions of numerical ones. Equivalent stress–strain curves obtained from numerical simulation results along with microstructural observations were utilized to investigate the effect of loading conditions on deformation behavior of the experimental alloy. The results indicated a homogenous distribution of shear strains within the gage and the high applicability of shear-compression specimen to study shear flow behavior of materials at hot deformation conditions. Content Type Journal Article Pages 1-8 DOI 10.1007/s11340-011-9525-9 Authors S. Moemeni, School of Metallurgy and Materials Engineering, University of Tehran, Tehran, Iran A. Zarei-Hanzaki, School of Metallurgy and Materials Engineering, University of Tehran, Tehran, Iran H. R. Abedi, School of Metallurgy and Materials Engineering, University of Tehran, Tehran, Iran V. Torabinejad, School of Metallurgy and Materials Engineering, University of Tehran, Tehran, Iran Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    For Kolsky bar testing beyond strain-rates of 10,000/s, it is useful to employ bars with diameters of only a few millimeters or less. Furthermore, very small (sub-millimeter) systems are compatible with micron-sized specimens, to be used, for example, for the determination of mesoscale properties. However, at these sizes, traditional strain-gage measurements of the longitudinal waves within the bars become impractical. In this paper we describe the application of optical measurement techniques to two Kolsky bars, with 3.2 and 1.6 mm diameters. A transverse displacement interferometer is used to measure the displacement of the mid-point of the incident bar and provide measurements of the incident and reflected pulses. Similarly, a normal displacement interferometer is used to measure the displacement of the free-end of the transmitter bar and provide a measurement of the transmitted pulse. The new methods are used to characterize the behavior of 6061-T6 aluminum at rates greater than 100,000/s. The feasibility of application to smaller bars is also discussed. Content Type Journal Article Pages 1-12 DOI 10.1007/s11340-011-9524-x Authors D.T. Casem, US Army Research Laboratory, RDRL-WMP-B, Aberdeen Proving Ground, Aberdeen, MD 21005-5069, USA S.E. Grunschel, Oak Ridge Institute for Science and Education, Oak Ridge, TN, USA B.E. Schuster, US Army Research Laboratory, RDRL-WML-H, Aberdeen Proving Ground, Aberdeen, MD 21005-5069, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    This paper presents results of numerical simulations and an experimental investigation of a method to determine shape of a beam from curvature and/or strain measurements. The purpose of this work was to develop an efficient and accurate method that can be used in real time shape monitoring of beam type structures with possible extension to more complex systems. A method based upon solving a set of continuity equations is presented. Numerical simulations were implemented to minimize the number of sensors and to determine the most beneficial sensor locations and sensor/model configuration to capture the shape in a timely and effective manner. Simulations showed that dividing the beam into segments (elements) and placing sensors at the Gauss point locations of each segment gave only 0.14% systematic error while using three elements and two Gauss points per element. An experiment was designed using an aluminum beam combined with a data acquisition system and a shape reconstruction algorithm. The real-time reconstruction of shape from curvature data was accomplished using strain gages for the curvature estimates. The results were compared to a technique based on position only data and point cloud image data. Overall, consistent results were obtained. The percent difference between the experimental and photogrammetry results fluctuated from 1.4 to 3.5% when various magnitudes of concentrated loads were applied to the beam. This methodology may be useful in real-time shape control and shape modification systems with potential applications in structural health monitoring and damage detection. Content Type Journal Article Pages 1-16 DOI 10.1007/s11340-011-9523-y Authors R. Glaser, Department of Mechanical Engineering, University of Maine, 5711 Boardman Hall, Room 203, Orono, ME 04469-5711, USA V. Caccese, Department of Mechanical Engineering, University of Maine, 5711 Boardman Hall, Room 212, Orono, ME 04469-5711, USA M. Shahinpoor, Department of Mechanical Engineering, University of Maine, 5711 Boardman Hall, Room 219, Orono, ME 04469-5711, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The present paper is devoted to the identification of frictional properties in bolted assemblies. It is shown that kinematic data provided by digital image correlation can be used to analyze the change of the friction coefficient with the number of cycles. Two approaches are followed. The first one is based on the displacement jump between the assembled plates, and the second one relies on displacement fields measured on the same surface. Content Type Journal Article Pages 1-12 DOI 10.1007/s11340-011-9518-8 Authors J. de Crevoisier, Laboratoire de Mécanique et Technologie (LMT-Cachan), ENS de Cachan / CNRS / Université Paris 6 / PRES UniverSud Paris, 61 Avenue du Président Wilson, 94235 Cachan Cedex, France N. Swiergiel, EADS-IW, 12 rue Pasteur, 92152 Suresnes, France L. Champaney, Laboratoire de Mécanique et Technologie (LMT-Cachan), ENS de Cachan / CNRS / Université Paris 6 / PRES UniverSud Paris, 61 Avenue du Président Wilson, 94235 Cachan Cedex, France F. Hild, Laboratoire de Mécanique et Technologie (LMT-Cachan), ENS de Cachan / CNRS / Université Paris 6 / PRES UniverSud Paris, 61 Avenue du Président Wilson, 94235 Cachan Cedex, France Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Microelectromechanical system (MEMS) devices based on electro-thermal actuation have been used over the past few years to perform tensile tests on nanomaterials. However, previous MEMS designs only allowed small ( e . g ., 〈100 nm) total displacement range without a significant increase in temperature near the nanospecimens (〈20°C), thereby limiting the design of the load sensor or the range of nanomaterials to test. Here we characterize the thermo-mechanical behavior of three MEMS devices, using optical displacement measurements, micro-Raman temperature measurements, and finite element modeling. We observe the increase in temperature near the nanospecimen gap per displacement of thermal actuator to linearly decrease with the distance between nanospecimen gap and thermal actuator. We also present a MEMS device that can provide up to 1.6 μm of total displacement with less than 10°C increase in temperature near the nanospecimens, more than one order of magnitude improvement with respect to previously published MEMS material testing setups. This MEMS device can be used for accurate, temperature-controlled tensile testing of nanocrystalline metallic nanobeams. Content Type Journal Article Pages 1-11 DOI 10.1007/s11340-011-9526-8 Authors B. Pant, G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405, USA S. Choi, G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405, USA E. K. Baumert, G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405, USA B. L. Allen, G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405, USA S. Graham, G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405, USA K. Gall, G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405, USA O. N. Pierron, G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    One of the prominent threats in the endeavor to develop next-generation space assets is the risk of space debris impact in earth’s orbit and micrometeoroid impact damage in deep space. To date, there is no study available which concentrates on the analysis of dynamic crack growth from hypervelocity impacts on such structures, resulting in their eventual catastrophic degradation. Experiments conducted using a unique two-stage light-gas gun facility have examined the in situ dynamic fracture of brittle polymers subjected to this high-energy-density event. Optical techniques of caustics and photoelasticity, combined with high-speed photography, analyze crack growth behavior of Mylar and Homalite 100 thin plates after impact at velocities ranging from 3 to 7 km/s (7,000–15,500 mph). Results indicate that even under extreme impact conditions of out-of-plane loading, highly localized heating, and energetic impact phenomena involving plasma formation and ejecta, the dynamic fracture process occurs during a deformation regime dominated by in-plane loading. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-011-9521-0 Authors L. Lamberson, Graduate Aerospace Laboratories, California Institute of Technology, Pasadena, CA 91125, USA V. Eliasson, Department of Aerospace & Mechanical Engineering, University of Southern California, Los Angeles, CA 90089, USA A. J. Rosakis, Graduate Aerospace Laboratories, California Institute of Technology, Pasadena, CA 91125, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    A method for the stress separation of interferometrically measured isopachics using an Airy stress function is proposed in this study. A Poisson equation that represents the relationship between the sum of principal stresses and an Airy stress function is solved using a finite element method. The Dirichlet boundary condition for solving the Poisson equation is determined by the approximation of an assumed Airy stress function along the boundary of the model. Therefore, the distribution of the Airy stress function is obtained from the measured isopachic contours. Then, the stresses are obtained from the computed Airy stress function. The effectiveness of the proposed method is validated by applying the proposed method to the isopachic contours in a perforated plate obtained by Mach-Zehnder interferometry. Results indicate that stress components around a hole in a plate can be obtained from isopachics by the proposed method. Content Type Journal Article Pages 1-9 DOI 10.1007/s11340-011-9531-y Authors S. Yoneyama, Department of Mechanical Engineering, Aoyama Gakuin University, Sagamihara, 252-5258 Japan S. Arikawa, Department of Mechanical Engineering, Aoyama Gakuin University, Sagamihara, 252-5258 Japan T. Shibayama, Department of Mechanical Engineering, Aoyama Gakuin University, Sagamihara, 252-5258 Japan Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    High energy x-ray diffraction can be used to probe the crystal scale mechanical response of polycrystalline alloys. Recently there have been several efforts to create new high energy x-ray experiments. These include the lattice Strain Pole Figure (SPF) technique. By measuring lattice strains in thousands of directions, the lattice strain tensor associated with each orientation can be determined. The focus of this paper is on transforming the SPF technique from a one-off style experiment to a measurement capability. Such a standardization process is of the utmost importance for the field of mechanics of materials and shifts the discovery associated with these experiments from the measurements themselves, to what they reveal about the material. We define a new technique for quantifying how effectively a set of lattice strain measurements (SPFs) probes each crystal orientation. The polycrystal sampling matrix, defined , represents the mapping between the most likely strain tensor for each orientation and the lattice strain results. The orientation space sampling matrix, defined , represents the set of lattice strain measurements that interrogate each crystal orientation. The rank of can be used to quantitatively compare different experimental configurations and systematically investigate . The net result is a new tool for selecting experimental conditions to produce optimal sets of SPF data. Results are shown for different experiment configurations and an example of the SPF technique is provided for the Low Solvus High Refractory (LSHR) nickel base superalloy. In addition, we show that for the face centered cubic LSHR, with lattice strains measured for the {111}, {200}, {220}, and the {311} crystallographic families, there are at most 25 lattice strain measurements that interrogate a single orientation. Content Type Journal Article Pages 1-19 DOI 10.1007/s11340-011-9505-0 Authors J. C. Schuren, Mechanical and Aerospace Engineering, Cornell University, 194 Rhodes Hall, Ithaca, NY 14853, USA M. P. Miller, Mechanical and Aerospace Engineering, Cornell University, 194 Rhodes Hall, Ithaca, NY 14853, USA A. Kazimirov, Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY 14853, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    This paper reports a new technique, namely the incremental micro-hole-drilling method (IμHD) for mapping in-plane residual or applied stresses incrementally as a function of depth at the micron-scale laterally and the sub-micron scale depth-wise. Analogous to its macroscale counterpart, it is applicable either to crystalline or amorphous materials, but at the sub-micron scale. Our method involves micro-hole milling using the focused ion beam (FIB) of a dual beam FEGSEM/FIB microscope. The resulting surface displacements are recorded by digital image correlation of SEM images recorded during milling. The displacement fields recorded around the hole are used to reconstruct the stress profile as a function of depth. In this way residual stresses have been characterized around a drilled hole of 1.8microns. diameter, enabling the profiling of the stress variation at the sub-micron scale to a depth of 1.8 microns. The new method is used to determine the near surface stresses in a (peened) surface-severe-plastically-deformed (S 2 PD) Zr 50 Cu 40 Al 10 (in atomic percent, at.%) bulk metallic glass bar. In plane principal stresses of -800 MPa ± 90 MPa and −600 MPa ± 90 MPa were measured, the maximum compressive stress being oriented 15° to the axis of the bar. Content Type Journal Article Pages 1-12 DOI 10.1007/s11340-011-9502-3 Authors B. Winiarski, School of Materials, Materials Science Centre, The University of Manchester, Grosvenor Street, Manchester, M1 7HS UK P. J. Withers, School of Materials, Materials Science Centre, The University of Manchester, Grosvenor Street, Manchester, M1 7HS UK Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Piezoceramic transducers, acting as actuators and sensors, are attractive for generation and reception of Lamb waves in Structural Health Monitoring (SHM) systems. To get insight into the source-mechanisms of Lamb waves, the vibrations of piezoceramic actuators are analyzed for the free and bonded state of the piezoceramic by analytical and finite element (FEM) calculations. Mode shapes and spectra of piezoceramic actuators and Lamb wave fields are experimentally recorded by scanning laser vibrometry. The analytical solutions for bending modes are shown to be valid for large diameter-to-thickness-relations of a free piezoactuator (D/H 〉 10) only. For thicker piezoceramics, a FEM-solution gives better results. Calculated frequencies for radial modes of vibration are confirmed by 3-D-laser-vibrometry and measurements of electrical impedance. The bonded case of a piezoactuator exhibits a broad resonance peak resulting from the strong coupling between radial and bending modes. The assumption that optimal excitation of Lamb modes occurs for a matching of the wavelengths to the diameter of the piezoceramic holds only for thin ceramics. Otherwise the distinct modes of out-of-plane and in-plane vibrations control the excitation of the Lamb modes more than the wavelength matching. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-011-9503-2 Authors J. Pohl, Department of Electrical, Mechanical and Industrial Engineering (EMW), Anhalt University of Applied Sciences, Bernburger Str. 55, 06366 Köthen, Germany C. Willberg, Institute of Mechanics (IFME), Otto-von-Guericke-University, PF 4120, 39016 Magdeburg, Germany U. Gabbert, Institute of Mechanics (IFME), Otto-von-Guericke-University, PF 4120, 39016 Magdeburg, Germany G. Mook, Institute of Materials and Joining Technology (IWF), Otto-von-Guericke-University, PF 4120, 39016 Magdeburg, Germany Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    An experimental investigation was conducted to evaluate the dynamic performance of E-glass Vinyl Ester composite face sheet / foam core sandwich panels when subjected to pre-compression and subsequent blast loading. The sandwich panels were subjected to 0 kN, 15 kN and 25 kN of in plane compression respectively, prior to transverse blast wave loading with peak incident pressure of 1 MPa and velocity of 3 Mach. The blast loading was generated using a shock tube facility. During the experiments, a high-speed photographic system utilizing three digital cameras was used to acquire the real-time 3-D deformation of the sandwich panels. The 3D Digital Image Correlation (DIC) technique was used to quantify the back face out-of-plane deflection and in-plane strain. The results showed that in-plane compressive loading facilitated buckling and failure in the front face sheet. This mechanism greatly reduced the blast resistance of sandwich composites. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-011-9500-5 Authors E. Wang, Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA A. Shukla, Department of Mechanical, Industrial and Systems Engineering, University of Rhode Island, Kingston, RI 02881, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The sandwich plate twist test method involves torsion loading of a panel by application of concentrated loads at two diagonally opposite corners and supporting the panel at the other two corners. Compliance measured in this test can be used to extract the shear moduli of monolithic, composite and sandwich plates, and it may also be employed for determination of the twist stiffness, D 66 . Previous studies of the plate twist specimen have shown that classical laminated plate theory does not adequately predict the compliance of sandwich panels with a low density/modulus core, as a result of transverse shear deformation. This work proposes a “shear-corrected” model for accurate prediction of the plate twist compliance by incorporation of the transverse shear stiffnesses of the core. This model was used to extract the transverse shear modulus of a range of low density PVC foam cores from the measured panel twist compliance. Good agreement with published PVC foam core shear modulus values was obtained. Content Type Journal Article Pages 1-7 DOI 10.1007/s11340-011-9501-4 Authors F. Avilés, Centro de Investigación Científica de Yucatán, A.C., Unidad de Materiales, Calle 43 # 103, Col. Chuburná de Hidalgo, C.P. 97200 Mérida, Yucatán, México L. A. Carlsson, Department of Mechanical Engineering, Florida Atlantic University, Boca Raton, FL 33431, USA A. May-Pat, Centro de Investigación Científica de Yucatán, A.C., Unidad de Materiales, Calle 43 # 103, Col. Chuburná de Hidalgo, C.P. 97200 Mérida, Yucatán, México Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    This paper introduces a double shear axisymmetric specimen (Shear Compression Disk) and the methodology to extract flow and fracture properties of ductile materials, under various stress triaxiality levels. A thorough numerical investigation of the experimental set-up is performed, which reveals that the stresses are quite uniformly distributed in the gauge section during all the stages of the test. The attainable level of stress triaxiality (with pressures of up to 1.9 GPa) ranges from −0.1 to 1, which can be adjusted by a proper choice of geometrical parameters of the specimen. The methodology is implemented to quasi-static experiments on 4340 Steel and Aluminum 7075-T651 specimens. The flow properties are compared to those obtained by upsetting cylinders and show a very good agreement. For these materials it is observed that, contrary to the fracture strain, the flow properties are quite insensitive to the level of stress triaxiality. The fracture strain of the aluminum alloy increases with triaxiality and may be fitted with an exponential polynomial of the type suggested by [ 27 ]. These examples demonstrate the potential of the new specimen to obtain flow and fracture properties of ductile materials under controlled triaxiality. Content Type Journal Article Pages 1-13 DOI 10.1007/s11340-011-9482-3 Authors A. Dorogoy, Faculty of Mechanical Engineering, Technion—Israel Institute of Technology, 32000 Haifa, Israel B. Karp, Department of Mechanical Engineering, Ben-Gurion University of the Negev, P.O.B. 653, Beer-Sheva, 84105 Israel D. Rittel, Faculty of Mechanical Engineering, Technion—Israel Institute of Technology, 32000 Haifa, Israel Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description: Erratum: How Do Sperm Get to the Egg? Bioengineering Expertise Needed! Content Type Journal Article Pages 1-1 DOI 10.1007/s11340-010-9446-z Authors S. S. Suarez, Department of Biomedical Sciences, Cornell University, Ithaca, NY 14853, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Future generations of transistors, sensors, and other devices maybe revolutionized through the use of one-dimensional nanostructures such as nanowires, nanotubes, and nanorods. The unique properties of these nanostructures will set new benchmarks for speed, sensitivity, functionality, and integration. These devices may even be self-powered, harvesting energy directly from their surrounding environment. However, as their critical dimensions continue to decrease and performance demands grow, classical mechanics and associated experimental techniques no longer fully characterize the observed behavior. This perspective examines the evolving role of experimental mechanics in driving the development of these new devices. Emphasis is placed on advances in experimental techniques for comprehensive characterization of size effects and their coupling, as well as assessment of device-level response. Content Type Journal Article DOI 10.1007/s11340-010-9437-0 Authors R. Agrawal, Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Rd., Evanston, IL 60208-3111, USA O. Loh, Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Rd., Evanston, IL 60208-3111, USA H. D. Espinosa, Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Rd., Evanston, IL 60208-3111, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The X-Ray Diffraction technique has been widely applied for decades in many industrial sectors for the quantification of residual stresses in metallic parts. The present paper describes the laboratory calibration of this technique with the aim of adapting it to the quantification of global stresses (non residual) in metallic structures, in service for civil engineering and building. A small structure specifically built for this research has been repeatedly loaded at laboratory. In each load level the global stresses in a bar of the structure have been quantified by means of X-Ray Diffraction technique. The experimental procedure allows one to discern the residual stresses and the structural (mechanical) stresses in service. The correlation between the stresses deduced experimentally and the applied stresses is excellent. As conclusion, it can be stated that the X-Ray Diffraction technique as a non-destructive technique, has been calibrated to be used for stress deduction in metallic elements in service. Content Type Journal Article Pages 1-7 DOI 10.1007/s11340-010-9454-z Authors S. Sánchez-Beitia, Faculty of Architecture, Basque Country University, 20018 San Sebastián, Spain Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    This paper studies the effects of a microwave excitation on the transverse vibrations of viscoelastic bars placed inside unconventional electromagnetic waveguides. Its purpose is to present a general approach that can be applied to analyze and to interpret the physical phenomena risen during the heating process. These phenomena were not predicted either by conventional experiments or by existing theoretical models. To measure the bar transverse deformations, an opening line and a hole have been made respectively on one of the small transverse sides of the waveguides. The comparison between the spectra of the experimental transverse velocities measured with these two waveguides has pointed out some differences. Theoretical and finite element (FE) simulations of the experiments have been firstly applied to figure out the nature of these variations. The analysis is conducted by a parameterized approach that takes into account the effects of the opening line made along the waveguide on both the propagation of the electromagnetic power density and the temperature rise distribution inside the sample. Good agreements between the models and the experimental data are demonstrated. Furthermore, the method has also shown a sudden asymmetric temperature distribution that leads to the generation of new flexural modes. These last modes are specific to the experiment used to apply the microwave induce acoustic technique. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-010-9451-2 Authors A. Mohamed Elarif, Université de Bordeaux, Laboratoire de Mécanique Physique UMR CNRS 5469, IPB, 351, cours de la Libération, 33405 Talence Cedex, France C. Bacon, Université de Bordeaux, Laboratoire de Mécanique Physique UMR CNRS 5469, IPB, 351, cours de la Libération, 33405 Talence Cedex, France B. Hosten, Université de Bordeaux, Laboratoire de Mécanique Physique UMR CNRS 5469, 351, cours de la Libération, 33405 Talence Cedex, France Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The dissipation of strain energy density per cycle was analyzed to understand its trend through a fatigue process. The motivation behind this analysis is to improve a fatigue life prediction method, which is based on a strain energy and failure correlation. The correlation states that the same amount of strain energy is dissipated during both monotonic fracture and cyclic fatigue. This means the summation of strain energy density per cycle is equal to the total strain energy density dissipated monotonically. In order to validate this understanding, the strain energy density per cycle was analyzed at several alternating stress levels for fatigue life of Aluminum 6061-T6 (Al 6061-T6) between 10 3 and 10 5 cycles. The analysis includes the following: Alternating between high and low operating frequencies (50x magnitude difference), interruption of cyclic load during testing, and idle/zero-loading intervals of 20–40 minutes in-between cyclic loading sequences. All experimental results show a consistent trend of cyclic softening as the loading cycles approach failure; however, due to an inefficient curve fit procedure of the stress-dependent strain equation at low alternating stresses onto the experimental stress-strain data, a new approach for calculating the strain energy density per cycle is explored and shows promising results. Content Type Journal Article Pages 1-7 DOI 10.1007/s11340-010-9457-9 Authors O. E. Scott-Emuakpor, Air Force Research Laboratory, Wright-Patterson AFB, WPAFB, OH 45433, USA T. J. George, Air Force Research Laboratory, Wright-Patterson AFB, WPAFB, OH 45433, USA C. J. Cross, Air Force Research Laboratory, Wright-Patterson AFB, WPAFB, OH 45433, USA M.-H. H. Shen, Department of Mechanical Engineering, The Ohio State University, Columbus, OH 43210, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    An experimental apparatus designed specifically for fretting experiments on mechanical lap joints is presented. A piezoactuator is used to impose fretting motion, and a tri-axial load cell is used to measure tangential force as well as possible misalignment forces. A laser nanosensor is employed to measure the relative motion between the joint halves. No post-processing and filtering of the data is needed to obtain the fretting response using this apparatus. Instead, raw data obtained from experiments with monolithic and 1-bolt aluminum and steel joints under various loading conditions suggest that noise, misalignment, stiffness and damping associated with the apparatus are minimal, and thus the fretting behavior of the mechanical lap joints is accurately captured. Analyses of typical fretting loops obtained by the proposed apparatus suggest that normal preload and maximum tangential displacement influence the critical joint parameters of stiffness and damping. Aluminum joints show a more compliant behavior with more energy dissipation compared to steel joints. Content Type Journal Article Pages 1-15 DOI 10.1007/s11340-010-9458-8 Authors M. Eriten, Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL USA A. A. Polycarpou, Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL USA L. A. Bergman, Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, Urbana, IL USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Films with thickness ranging from 10 to 100 μm are increasingly being used as the structural components of microelectromechanical systems (MEMS). Measuring the mechanical properties of these thick films is essential for enabling the design of MEMS with high performance and sufficient reliability. In this paper, we present a simple and convenient method for measuring the elastic modulus of thick films by loading a clamped circular film using a spherical tip. The test is implemented using a commercial nanoindenter so that the load and displacement can be measured with resolution of micronewtons and nanometers, respectively. Robust protocols have been developed for implementing the test within the constraints imposed by the nanoindenter. A crucial component of these protocols is a method for selecting loads to ensure deformation in the elastic bending regime and to minimize the relative contribution of contact indentation. The accuracy and utility of the nanoindenter-based bending test are discussed using measurements on thick films of aluminum and a standard epoxy. Content Type Journal Article Pages 1-8 DOI 10.1007/s11340-011-9494-z Authors B. Ashrafi, Department of Mechanical Engineering, McGill University, 817 Sherbrooke Street West, Montreal, QC, Canada K. Das, Department of Mechanical Engineering, McGill University, 817 Sherbrooke Street West, Montreal, QC, Canada R. Le Faive, Department of Mechanical Engineering, McGill University, 817 Sherbrooke Street West, Montreal, QC, Canada P. Hubert, Department of Mechanical Engineering, McGill University, 817 Sherbrooke Street West, Montreal, QC, Canada S. Vengallatore, Department of Mechanical Engineering, McGill University, 817 Sherbrooke Street West, Montreal, QC, Canada Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    An experimental investigation was conducted to study the effect of quasi-static and dynamic compressive loading on the electrical response of multi-wall carbon nanotube (MWCNT) reinforced epoxy nanocomposites. An in - situ polymerization process using both a shear mixer and an ultrasonic processor were employed to fabricate the nanocomposite material. The fabrication process parameters and the optimum weight fraction of MWCNTs for generating a well-dispersed percolation network were first determined. Absolute resistance values were measured with a high-resolution four-point probe method for both quasi-static and dynamic loading. In addition to measuring the percentage change in electrical resistance, real-time damage was captured using high-speed photography. The real-time damage was correlated to both load and percentage change in resistance profiles. The experimental findings indicate that the bulk electrical resistance of the nanocomposites under both quasi-static and dynamic loading conditions initially decreased between 40%–60% during compression and then increased as damage initiated and propagated. Content Type Journal Article Pages 1-8 DOI 10.1007/s11340-011-9488-x Authors N. J. Heeder, Dynamic Photomechanics Laboratory, Department of Mechanical, Industrial & Systems Engineering, University of Rhode Island, Kingston, RI 02881, USA A. Shukla, Dynamic Photomechanics Laboratory, Department of Mechanical, Industrial & Systems Engineering, University of Rhode Island, Kingston, RI 02881, USA V. Chalivendra, Department of Mechanical Engineering, University of Massachusetts Dartmouth, North Dartmouth, MA 02747, USA S. Yang, Department of Chemistry, University of Rhode Island, Kingston, RI 02881, USA K. Park, Micro/Nanoscale Engineering Laboratory, Department of Mechanical, Industrial & Systems Engineering, University of Rhode Island, Kingston, RI 02881, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The material addressed in this research is stainless steel 2169, a 200 series stainless steel which has so far found applications in aviation, demolition, motor-vehicle design and nuclear reactor containment. Longitudinal and lateral stresses during the shock loading of 2169 have been measured using manganin stress gauges. The shock Hugoniot has been determined and is shown to be similar to other grades of steel in the longitudinal stress range ca. 2–18 GPa. The shear strength has been shown to increase with impact stress and it is seen that when compared with another common austenitic stainless steel (304 L) the initial HEL is greater, but that 2169 has a lesser degree of hardening with increased impact stress. This is discussed as being due to the relative stacking fault energies (SFE) of the two materials, with lower SFE leading to a greater degree of deformation twinning and therefore an increase in twin and dislocation interactions. Content Type Journal Article Pages 1-9 DOI 10.1007/s11340-011-9487-y Authors G. Whiteman, AWE, Aldermaston, Reading, Berkshire, RG7 4PR UK J. C. F. Millett, AWE, Aldermaston, Reading, Berkshire, RG7 4PR UK Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The results of experimental investigation on the mechanical properties of clay brick masonry after high temperature exposition are here presented. The adopted physical model of masonry means to represent both new and old load bearing walls, so to get useful and applicable results. Uniaxial and diagonal compressive tests were carried on masonry samples exposed to 300 and 600°C. Samples of the component materials were tested in compression as well, and the elastic moduli of bricks and mortar were also measured. The results allow to evaluate the levels of residual strength and stiffness of all tested materials after exposure to high temperatures. Finally, property-temperature laws of mechanical decay for masonry, brick and mortar after high temperature exposition are here proposed and discussed. Content Type Journal Article Pages 1-19 DOI 10.1007/s11340-011-9493-0 Authors S. Russo, Research Unit CdSM—“Assessment of monumental buildings”, IUAV University of Venice, Dorsoduro 2206, 30123 Venice, Italy F. Sciarretta, Research Unit CdSM—“Assessment of monumental buildings”, IUAV University of Venice, Dorsoduro 2206, 30123 Venice, Italy Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    During their operating life, electromechanical relays (EMRs) are subjected to external mechanical vibrations that can induce undesirable vibratory responses in the movable part of the relay and thus produce an unwanted temporary break in electric connections. This paper presents a simplified multiphysics model dedicated to the prediction of the maximum vibration levels that these relays can undergo before a loss of contact occurs. Our methodology considers the magnetic aspects as well as the mechanical aspects. The dynamic behaviour of the movable part is modelled as a cantilever beam subjected at its extremity to an elastic force. The dynamic parameters were updated from the identification of the first natural modes of the movable part of the relay. The magnetic force acting on the movable part was computed using a one-dimensional approach with an equivalent magnetic circuit and was corroborated thanks to experimental measurements and two-dimensional Finite Element simulations. The interaction between the electromagnetic and mechanical phenomena was taken into account using a parameterization coupled approach. Our methodology has been applied to the study of the PED PXC-1203 relay. The numerical predictions were validated using experimental data measured in the frequency range [2–8 kHz]. A parametric analysis of our model was performed and shows the influence of some factors, like the air gap and the rated voltage, that affect the performance of the relay under external mechanical vibrations. Content Type Journal Article Pages 1-14 DOI 10.1007/s11340-011-9478-z Authors D. Wattiaux, Faculté Polytechnique, University of Mons, 20 place du parc, 7000 Mons, Belgium O. Verlinden, Faculté Polytechnique, University of Mons, 20 place du parc, 7000 Mons, Belgium Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description: Erratum to: The Effect of Limb Kinematics on the Speed of a Legged Robot on Granular Media Content Type Journal Article Pages 1-1 DOI 10.1007/s11340-011-9497-9 Authors C. Li, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA P. B. Umbanhowar, Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208, USA H. Komsuoglu, Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA D. I. Goldman, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    This paper deals with the investigations of a porous carbon black-filled rubber, tested with regard to its pressure and tension behaviour. In the tension range only uniaxial tests are performed while in the pressure range uniaxial as well as hydrostatic tests are performed. The uniaxial experiments are carried out in a custom-made uniaxial device and the hydrostatic tests in a pressure chamber which is specially developed for this application. The construction and use of the pressure chamber is clearly described in this paper. All experiments are related to the basic elasticity of the material. The viscoelastic behaviour is completely disregarded at this point. Not only the experiments are discussed, also the modelling of the material is looked at. The tested cellular rubber is composed of an incompressible solid phase and a compressible gas phase. For that reason a so-called structural compressibility is observed. The compressible behaviour of cellular rubber is an important property. So the main focus of the paper is on the pressure tests and the simulation of these. The existing material models for rubber like materials only deal with incompressible rubber structures. To represent the compressible behaviour, the Theory of Porous Media is used. The constitutive model is based on a polynomial approach for an incompressible material. This is complemented by a volumetric expansion term with a point of compaction to model the structural compressibility. Content Type Journal Article Pages 1-8 DOI 10.1007/s11340-011-9489-9 Authors N. Koprowski-Theiß, Department of Applied Mechanics, Saarland University, Saarbrücken, Saarland, Germany M. Johlitz, Department of Applied Mechanics, University of the Federal Armed Forces Munich, Munich, Bavaria, Germany S. Diebels, Department of Applied Mechanics, Saarland University, Saarbrücken, Saarland, Germany Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Metal magnetic memory (MMM) method is a novel, passive magnetic method for inspecting mechanical degradation of ferromagnetic components. To promote a further understanding of the relation between the magnetic characteristics and mechanical deformation, the normal spontaneous stray field component and its gradient of Q235-steel specimens were measured during uniaxial tensile and compressive loading processes. The results show that the normal spontaneous stray field component and its gradient are effective in capturing different deformation stages under tensions, but no detectable change can be found during the whole compressive loading processes. Compared with the amplitude of the normal spontaneous stray field component, the gradient is a more sensitive parameter. In addition, the result demonstrates that it is easy to differentiate macro-crack and plastic deformation because the differences among measured spontaneous stray field signals are obvious. Moreover, various factors affecting test results were also considered. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-011-9490-3 Authors K. Yao, Department of Mechanics, School of Civil Engineering, Beijing Jiao-Tong University, Beijing, 100044 China Z. D. Wang, Department of Mechanics, School of Civil Engineering, Beijing Jiao-Tong University, Beijing, 100044 China B. Deng, Department of Mechanics, School of Civil Engineering, Beijing Jiao-Tong University, Beijing, 100044 China K. Shen, Department of Mechanics, School of Civil Engineering, Beijing Jiao-Tong University, Beijing, 100044 China Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    In this study the influence of stress and temperature on the elastic modulus during fully-reversed low cycle fatigue of the titanium alloy Ti6242 is examined. The change of the elastic properties with stress manifests itself in a crescent-like shaped hysteresis loop of stress vs. plastic strain at very low amplitudes, i.e. below the technical yield stress. A quadratic extension of Hooke’s law with a second constant “ k ” is applied. The parameters are determined all along the unloading curve in tension and compression. The approach results in the alignment of the hysteresis loop so that they become vertical, i.e. the elastic strain is accurately described. The value and sign of “ k ” depend on whether the deformation occurs in tension or compression. Like the Young’s modulus E 0 , “k” also depends on temperature. At temperatures up to 550°C the values of “ k ” in tension and compression do not change during fatigue life. However, at 650°C thermally activated slip processes lead to changes of both, E 0 and “ k ”. Content Type Journal Article Pages 1-7 DOI 10.1007/s11340-011-9492-1 Authors T. K. Heckel, Institut für Werkstofftechnik, Universität Siegen, 57068 Siegen, Germany A. Guerrero-Tovar, Materials Science Department, Universidad Simón Bolívar, Apartado 89000, Caracas, 1080A Venezuela H.-J. Christ, Institut für Werkstofftechnik, Universität Siegen, 57068 Siegen, Germany Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Measuring accurate displacement distributions for large-scale structures is an important issue and a very challenging task. Recently, a simple and accurate phase measurement technique called sampling moiré method [Exp Mech 50–4:501–508, ( 2010 )] has been developed for small-displacement distribution measurements. In this method, the phase distribution of moiré fringes can be analyzed from a single grating image by simultaneously performing down-sampling image processing and intensity-interpolation to generate multiple phase-shifted moiré fringe images. In addition, the phase of the original grating can also be obtained from the phase of the moiré fringe by adding the phase of the sampling grating. In this study, the measurement accuracy of the sampling moiré method was analyzed through computer simulations and a displacement measurement experiment. Four factors of the sampling moiré method were investigated, including the sampling pitch, the order of the intensity-interpolation, random noise, and the form of grating. The results show that determining the optimal sampling pitch is an important factor for obtaining better results but it is not critical. In addition, a practical application of the sampling moiré method is presented that involves a deflection measurement on a 10-meter-long crane. The experimental results demonstrate that submillimeter deflections of the crane can be successfully detected. Content Type Journal Article Pages 1-10 DOI 10.1007/s11340-011-9491-2 Authors S. Ri, Department of Nanomechanics, Graduate School of Engineering, Tohoku University, Aoba 6-6-01, Aramaki, Aoba-ku, Sendai, 980-8579 Japan T. Muramatsu, Department of Nanomechanics, Graduate School of Engineering, Tohoku University, Aoba 6-6-01, Aramaki, Aoba-ku, Sendai, 980-8579 Japan M. Saka, Department of Nanomechanics, Graduate School of Engineering, Tohoku University, Aoba 6-6-01, Aramaki, Aoba-ku, Sendai, 980-8579 Japan K. Nanbara, Electric Power Research & Development Center, Chubu Electric Power Co., Inc., Kitasekiyama 20-1, Ohdaka-Cho, Midoriku, Nagoya, 458-8522 Japan D. Kobayashi, Electric Power Research & Development Center, Chubu Electric Power Co., Inc., Kitasekiyama 20-1, Ohdaka-Cho, Midoriku, Nagoya, 458-8522 Japan Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    The present paper aims at providing a contribution to the testing strategies in the field of mechanics of materials, with particular reference to low cycle fatigue in the strain control mode. After a detailed analysis of the state of the art on possible techniques for strain controlling, the paper points out the difficulties that could be encountered when a conventional longitudinal contact extensometer cannot be used. This methodology, based on controlling the strain at a particular specimen location, by controlling the relative displacement between its ends, was developed to provide an alternative solution in such occurrences. The paper introduces its analytical fundamentals for its most general application in the execution of fatigue or even static tests. Particular attention was devoted to the validation of the proposed methodology: this task was conducted by applying the suggested technique to both static and fatigue testing of hourglass specimens, by analyzing results also in comparison to other experimentations or numerical simulations, always observing a good agreement. The methodology proved to be efficient and reliable on a wide range of strain amplitudes. Content Type Journal Article Pages 1-15 DOI 10.1007/s11340-011-9496-x Authors G. Olmi, DIEM Department, Engineering Faculty, University of Bologna, Viale del Risorgimento, 2, 40136 Bologna, Italy Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    To determine a machine’s mechanical condition it is of importance to know the radial bearing forces in the machine. Radial forces are caused by magnetic pull forces in the generator, clamped shafts, mass unbalance and flow properties around the turbine. Measuring the shaft displacement in the bearing or the bearing housing acceleration is not sufficient for status determination of a vertical hydropower unit. It is the magnitude and frequencies of the radial forces in combination with structure properties which give information as to whether a measured value is harmful or not. This paper presents an alternative method for measurement of radial bearing load in a hydropower unit. The method presented in this paper is based on strain measurements on pivot pins. The pivot pins are placed behind the bearing pad and the radial loads acting on the pad propagate through the pivot pin. New pivot pins were purchased and equipped with strain gauges. The new pivot pins were calibrated and a transfer function between applied load and measured output voltage was identified for each pivot pin. After calibration the pivot pins were installed in a vertical hydropower unit. Measurements were performed for several different operating modes of the hydropower unit. To verify that the measured load levels were of right order of magnitude, the radial bearing loads were calculated from numerical simulations of bearing properties and shaft eccentricity measurements. The two methods for determining bearing load showed almost the same results. This indicates that either method can be used to determine bearing load. Content Type Journal Article Pages 1-9 DOI 10.1007/s11340-011-9495-y Authors M. Nässelqvist, Vattenfall Research & Development AB, Civil & Materials Engineering, SE-814 26 Älvklarleby, Sweden R. Gustavsson, Vattenfall Power Consultant AB Mechanical & Process Engineering, Kyrkogatan 4, 80320 Gävle, Sweden J.-O. Aidanpää, Division of Solid Mechanics, Luleå University of Technology, SE-97187 Luleå, Sweden Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Knowledge of the flow curve in metal forming is crucial to analyse formability, to describe strain-hardening and to set-up the non-linear constitutive equations of metal plasticity. Commonly available mechanical testing of materials supplied in the form of sheets and plates, under low loading rates, is limited to small values of strain. As a result of this, there is a generalized practice, and important source of modelling errors, of extrapolating the remaining part of the flow curves that are usually determined by means of tensile and bulge tests. The aim of this paper is to provide a new level of understanding for the stack compression test and to evaluate its capability for constructing the flow curves of metal sheets under high strains across the useful range of material testing conditions. The presentation draws from the fundamentals of the stack compression test to the assessment of its overall performance by comparing the flow curves obtained from its utilisation with those determined by means of compressive testing carried out on solid cylinder specimens of the same material. Results show that mechanical testing of materials by means of the stack compression test is capable of meeting the increasing demand of accurate and reliable flow curves for sheet metals. Content Type Journal Article Pages 1-8 DOI 10.1007/s11340-011-9480-5 Authors L. M. Alves, IDMEC, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049–001 Lisboa, Portugal C. V. Nielsen, Department of Mechanical Engineering, Technical University of Denmark, DTU - Building 425, DK-2800 Kgs. Lyngby, Denmark P. A. F. Martins, IDMEC, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049–001 Lisboa, Portugal Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851

Description:    Metallic micro-wires (diameter ≈10 μm) are widely used to suspend reference bodies and isolate them from micro-seismic vibration because of their low bending and torsional stiffness. They make it possible to realize torsion/swing low-resonant frequency oscillators, spectrally separable from the higher frequency physics of interest. In this study, metallic micro-wires are used to provide both seismic isolation through flexural compliance and high-speed actuation thanks to axial stiffness. An experimental apparatus is realized to characterize the dynamic response of a 25 μm diameter tungsten wire used to actuate a suspended mass (10 -2 kg) subjected to accelerations up to 0.2 m/s 2 . A theoretical non-linear model taking into account flexural and axial behaviour of the wire is developed and validated experimentally. Such a model makes it possible to predict the actual motion of the object, which significantly differs from that of the actuator. Content Type Journal Article Pages 1-14 DOI 10.1007/s11340-011-9485-0 Authors M. Benedetti, Department of Materials Engineering and Industrial Technologies, University of Trento, Via Mesiano 77, 38123 Trento, Italy D. Bortoluzzi, Department of Mechanical and Structural Engineering, University of Trento, Via Mesiano 77, 38123 Trento, Italy C. Zanoni, Department of Mechanical and Structural Engineering, University of Trento, Via Mesiano 77, 38123 Trento, Italy Journal Experimental Mechanics Online ISSN 1741-2765 Print ISSN 0014-4851