ALBERT

Description: In high-speed electric trains, a pantograph is mounted on the roof the train to collect power through contact with an overhead catenary wire. The effect of fast harmonic and parametric excitation on a stochastically driven pantograph-catenary system is studied in this paper. A single-degree-of-freedom model of the pantograph-catenary system is adopted, wherein the stiffness of the nonlinear spring has a time-varying component characterized by both low and high frequencies. Using perturbation and harmonic averaging, a Fokker-Planck-Kolmogorov equation governing the stationary response of the pantograph-catenary system is set up. Based on the transition probability density of the stationary response, it is found that even small high-frequency parametric excitation has an appreciable effect on the system response. Among other things, it shifts the resonant frequency and often changes the response characteristics markedly. Content Type Journal Article Pages - DOI 10.3233/SAV-130818 Authors R.H. Huan, Department of Mechanics, Zhejiang University, Hangzhou, Zhejiang, China W.Q. Zhu, Department of Mechanics, Zhejiang University, Hangzhou, Zhejiang, China F. Ma, Department of Mechanical Engineering, University of California, Berkeley, CA, USA Z.H. Liu, Department of Civil Engineering, Xiamen University, Xiamen, Fujian, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Predicting the degradation process of bearings before they reach the failure threshold is extremely important in industry. This paper proposed a novel method based on the support vector machine (SVM), and the Markov model to achieve this goal. Firstly, the features are extracted by time and time-frequency domain methods. However, the extracted original features still with high dimensional and include superfluous information, the nonlinear multi-features fusion technique LTSA is used to merge the features and reduce the dimension. Then, based on the extracted features, the SVM model is used to predict the bearings degradation process, the CAO method is used to determine the embedding dimension of the SVM model. After the bearing degradation process is predicted by SVM model, the Markov model is used to improve the prediction accuracy. The proposed method was validated by two bearing run-to-failure experiments, the results proved the effectiveness of the methodology. Content Type Journal Article Pages - DOI 10.3233/SAV-130817 Authors Shaojiang Dong, School of Mechatronics and Automotive Engineering, Chongqing Jiaotong University, Chongqing, China Shirong Yin, School of Mechatronics and Automotive Engineering, Chongqing Jiaotong University, Chongqing, China Baoping Tang, The State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing, China Lili Chen, School of Mechatronics and Automotive Engineering, Chongqing Jiaotong University, Chongqing, China Jun Li Tianhong Luo, School of Mechatronics and Automotive Engineering, Chongqing Jiaotong University, Chongqing, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: A methodology is presented to study resonances and stability for a single-degree-of-freedom (SDOF) system with piecewise linear-nonlinear stiffness terms (i.e. one piece is linear and the other is weakly nonlinear). Firstly, the exact response of the linear governing equation is obtained, and a modified perturbation method is applied to finding the approximate solution of the weakly nonlinear equation. Then, the primary and 1/2 subharmonic resonances are obtained by imposing continuity conditions and periodicity conditions. Furthermore, Jacobian matrix is derived to investigate the stability of resonance responses. Finally, the results of theoretical study are compared with numerical results, and a good agreement is observed. Content Type Journal Article Pages - DOI 10.3233/SAV-130819 Authors X. Gao, State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, China Q. Chen, State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: A direct approach is used to derive the exact solution for the free vibration of thin rectangular plates with discrete sprung masses attached. The plate is simply supported along two opposite edges and elastically supported along the two other edges. The elastic support can represent a range of boundary conditions from free to clamped supports. Considering only the compatibility of the internal forces between the plate and the sprung masses, the equations of the coupled vibration of the plate-spring-mass system are derived. The exact expressions for mode and frequency equations of the coupled vibration of the plate and sprung masses are determined. The solutions converge steadily and monotonically to exact values. The correctness and accuracy of the solutions are demonstrated through comparison with published results. A parametric study is undertaken focusing on the plate with one or two sprung masses. The results can be used as a benchmark for further investigation. The solution provided in the paper is general and includes several special cases, such as the plate with classical boundary conditions, the plate attached with discrete rigid masses, the plate supported by discrete springs and the plate restricted by rigid vertical point-supports. Content Type Journal Article Pages - DOI 10.3233/SAV-2010-0618 Authors Ding Zhou, College of Civil Engineering, Nanjing University of Technology, Nanjing 210009, People's Republic of China Tianjian Ji, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester, UK Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This paper presents the dynamic response of an Euler- Bernoulli beam supported on two-parameter Pasternak foundation subjected to moving load as well as moving mass. Modal analysis along with Fourier transform technique is employed to find the analytical solution of the governing partial differential equation. Shape functions are assumed to convert the partial differential equation into a series of ordinary differential equations. The dynamic responses of the beam in terms of normalized deflection and bending moment have been investigated for different velocity ratios under moving load and moving mass conditions. The effect of moving load velocity on dynamic deflection and bending moment responses of the beam have been investigated. The effect of foundation parameters such as, stiffness and shear modulus on dynamic deflection and bending moment responses have also been investigated for both moving load and moving mass at constant speeds. Numerical results obtained from the study are presented and discussed. Content Type Journal Article Pages - DOI 10.3233/SAV-2010-0624 Authors Rajib Ul Alam Uzzal, Concordia Center for Advanced Vehicle Engineering (CONCAVE), Mechanical and Industrial Engineering Department, Concordia University, 1515 St. Catherine West, Montreal, H3G 1M8, Canada Rama B. Bhat, Concordia Center for Advanced Vehicle Engineering (CONCAVE), Mechanical and Industrial Engineering Department, Concordia University, 1515 St. Catherine West, Montreal, H3G 1M8, Canada Waiz Ahmed, Concordia Center for Advanced Vehicle Engineering (CONCAVE), Mechanical and Industrial Engineering Department, Concordia University, 1515 St. Catherine West, Montreal, H3G 1M8, Canada Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Motivated by deployable satellite technology, this article presents a homogenization model of an inflatable, rigidized lattice structure with distributed macro-fiber composite (MFC) actuation. The model is based upon a general expression for the strain and kinetic energy of a fundamental repeated element of the structure. These expressions are reduced in order and expressed in terms of the strain and displacement components of an equivalent one-dimensional vibration model. The resulting model is used to analyze changes in the structural natural frequencies introduced by the local effects of the added macro-fiber composite actuators for several configurations. A finite element solution is used as a comparison for the homogenization model, and the two are shown to be in good agreement, although the latter requires significantly less computational effort. Content Type Journal Article Pages - DOI 10.3233/SAV-2010-0617 Authors A. Salehian, Department of Mechanical and Mechatronics Engineering, University of Walterloo, Waterloo, Ontario, Canada N2L 3G1 T.M. Seigler, Department of Mechanical Engineering, University of Kentucky, Lexington, KY, USA Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This paper presents a method for detection and estimation of structural damage on the basis of modal parameters of a damaged structure using imperialist competitive algorithm. The imperialist competitive algorithm was developed over the last few years in an attempt to overcome inherent limitations of traditional optimize method. In this research, imperialist competitive algorithm has been employed due to its favorable performance in detection of structural damages. The performance of the proposed method has been verified through using a benchmark problem provided by the IASC-ASCE Task Group on Structural Health Monitoring and a number of numerical examples. By way of comparison between location and amount of damage obtained from the proposed method and simulation model, it was concluded that the method is sensitive to the location and amount of damage. The results clearly revealed the superiority of the presented method in comparison with energy index method. Content Type Journal Article Pages - DOI 10.3233/SAV-2010-0639 Authors A. Bagheri, Center of Excellence for Fundamental Studies in Structural Engineering, School of Civil Engineering, Iran University of Science & Technology, Tehran 16846, Iran G. Ghodrati Amiri, Center of Excellence for Fundamental Studies in Structural Engineering, School of Civil Engineering, Iran University of Science & Technology, Tehran 16846, Iran Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: A novel method to generate time series of vibration waves is proposed in the paper. Considering the frequency band energy as the criterion, synthesis formulas for fluctuating wind pressure and earthquake ground motion are developed in terms of Daubechies wavelet and Harr wavelet respectively. The wavelet reconstruction method is applicable to both stationary and non-stationary process simulation. Theoretically, for non-stationary (such as seismic) process synthesis, it has a better non-stationarity in time-frequency domain than the traditional trigonometric series. Influence of wavelet delamination number and wavelet function type is also analyzed. Numerical results show that the synthesis of vibration waves based on wavelet reconstruction method contains main components of vibration, and can reflect the main properties of practical vibrations. Content Type Journal Article Pages - DOI 10.3233/SAV-2010-0638 Authors L.H. Zou, Department of Civil Engineering, Fuzhou University, Fuzhou 350108, China A.P. Liu, Department of Civil Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China X. Ma, School of Natural and Built Environments, University of South Australia, Adelaide 5095, Australia C. Zhang, Department of civil and Environmental Engineering, University of Auckland Auckland 1142, New Zealand K. Huang, Department of Civil Engineering, Fuzhou University, Fuzhou 350108, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: We present in this paper a novel and unified control approach that combines intelligent fuzzy logic methodology with predictive method for controlling chaotic vibration of a class of uncertain chaotic systems. We first introduce prediction into each subsystem of Takagi Sugeno (T-S) fuzzy IF-THEN rules and then present a unified T-S predictive fuzzy model for chaos control. The proposed controller can successfully stabilize the chaos and track the desired targets. The simulation results illustrate its effectiveness. Content Type Journal Article Pages - DOI 10.3233/SAV-2010-0637 Authors Abdelkrim Boukabou, Department of Electronics, Jijel University, BP98 Ouled Aïssa, Jijel 18000, Algeria Noura Mansouri, Department of Electronics, Constantine University, RT Ain Elbey, Constantine 25000, Algeria Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Gearboxes usually run under fluctuating load conditions during service, however most of papers available in the literature describe models of gearboxes under stationary load conditions. Main task of published papers is fault modeling for their detection. Considering real situation from industry, the assumption of stationarity of load conditions cannot be longer kept. Vibration signals issued from monitoring in maintenance operations differ from mentioned models (due to load non-stationarity) and may be difficult to analyze which lead to erroneous diagnosis of the system. The objective of this paper is to study the influence of time varying load conditions on a gearbox dynamic behavior. To investigate this, a simple spur gear system without defects is modeled. It is subjected to a time varying load. The speed-torque characteristic of the driving motor is considered. The load variation induces speed variation, which causes a variation in the gearmesh stiffness period. Computer simulation shows deep amplitude modulations with sidebands that don't differ from those obtained when there is a defective tooth. In order to put in evidence the time varying load effects, Short Time Fourier Transform and then Smoothed Wigner-Ville distribution are used. Results show that the last one is well suited for the studied case. The experimental validation presented at the end of the paper confirms the obtained results. Such results offer useful information when diagnosing gear transmissions by avoiding confusing conclusions from vibration signals. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0656 Authors Fakher Chaari, Dynamics of Mechanical Systems Research Unit, National School of Engineers of Sfax, BP 1173-3038, Sfax, Tunisia Walter Bartelmus, Wroclaw University of Technology, Poland Radoslaw Zimroz, Wroclaw University of Technology, Poland Tahar Fakhfakh, Dynamics of Mechanical Systems Research Unit, National School of Engineers of Sfax, BP 1173-3038, Sfax, Tunisia Mohamed Haddar, Dynamics of Mechanical Systems Research Unit, National School of Engineers of Sfax, BP 1173-3038, Sfax, Tunisia Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Investigated are modeling and control approaches for vibration analysis of two identical beams which are coupled with fluid and active mechanical links. In the modeling of the coupled beam system, orthogonal functions are used to represent vibration of the beams and the fluid-structure interaction is considered. Frequency Response Functions (FRFs) are derived from the coupled governing equations and the superposition principle for linear vibration systems. In the control of vibration of the beams, impulse response functions corresponding to the FRFs and an adaptive control algorithm are employed to attenuate vibration transmission between the two beams. Natural frequencies, mode shapes as well as the pressure distribution in the fluid are computed. The results obtained by the proposed modeling method are in good consistency with those obtained by the finite element analysis. Moreover, it is demonstrated that the active mechanical link is able to reduce vibration transmission and change the deformation of beams as well as the distribution of fluid pressure. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0657 Authors Zhiyi Zhang, State Key Laboratory of Mechanical Systems and Vibration, Shanghai Jiaotong University, Shanghai, P.R. China Fang Hu, State Key Laboratory of Mechanical Systems and Vibration, Shanghai Jiaotong University, Shanghai, P.R. China Zeng Li, State Key Laboratory of Mechanical Systems and Vibration, Shanghai Jiaotong University, Shanghai, P.R. China Hongxing Hua, State Key Laboratory of Mechanical Systems and Vibration, Shanghai Jiaotong University, Shanghai, P.R. China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This paper deals with the dynamic analysis of pre-stressed laminated composite plates. Particular emphasis is devoted to the case of in-plane mono-axial, biaxial, shear and combined loadings. Both equivalent single layer and layer-wise plate kinematic description are addressed, according to the hierarchical approach proposed by the Carrera's unified formulation. The different kinematic approaches are compared in order to identify the appropriate modeling for laminated composite plates subjected to combined loadings. The principle of virtual displacement is applied in order to obtain governing equations and the corresponding problem is solved through the finite element method. When possible, assessments/comparisons with exact solutions are proposed. Moreover, the effects of different stacking sequences, boundary conditions, geometries and materials on plate natural frequencies are illustrated. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0655 Authors E. Carrera, Department of Aeronautics and Space Engineering, Politecnico di Torino, Turin, Italy P. Nali, Department of Aeronautics and Space Engineering, Politecnico di Torino, Turin, Italy S. Lecca, Department of Aeronautics and Space Engineering, Politecnico di Torino, Turin, Italy M. Soave, Department of Aeronautics and Space Engineering, Politecnico di Torino, Turin, Italy Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The impact duration between two structures is not easy to forecast. Indeed it depends on many parameters including local parameters as well as structural parameters which characterize the dynamics of the structures. In this paper we will show that it is possible to have a prior estimation of the impact duration. In fact the simulations show that this parameter is connected to some characteristics of a specific model, the so-called antioscillator model, even for the complex case of the impact between two flexible structures. All the simulations carried out on different cases show the close relationship between the first impact duration and the antioscillator characteristics. However some limitations exist and have been highlighted. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0653 Authors E. Jacquelin, Université de Lyon, F-69622, Lyon,France – LBMC, UMR-T9406, Université Lyon 1, Villeurbanne, France – IFSTTAR, Bron, France S. Pashah, Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Box 1095 KFUPM, Dharan 31261, Saudi Arabia J.P. Lainé, Université de Lyon, F-69622, Lyon,France - Ecole Centrale de Lyon, CNRS, LTDS, UMR 5513, F-69134, Ecully – France M. Massenzio, Université de Lyon, F-69622, Lyon,France – LBMC, UMR-T9406, Université Lyon 1, Villeurbanne, France – IFSTTAR, Bron, France Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: In recent years carbon fibre reinforced polymers (CFRPs) have become some of the most important structural materials in the aerospace industry due to their excellent stiffness and strength to weight ratios. The real-life loading histories of aerospace composite components and structures involve the generation of transient loads that can propagate as cyclic impacts. This phenomenon is known as impact fatigue (IF). Such loads can cause various types of damage in composites, including fibre breakage, transverse matrix cracking, de-bonding between fibres and matrix and delamination, resulting in a reduction of residual stiffness and a loss of functionality. The effects of IF are of major importance due its detrimental effect on the performance and reliability of components and structures after relatively few impacts and low force levels compared to those in a standard fatigue regime. This study employs a unique testing system with the capability of subjecting specimens to fully instrumented repetitive impact loading. The main aim of this paper is to provide results elucidating the effect of IF on the damage behaviour of CFRP specimens. A detailed damage analysis is implemented utilising an X-ray micro computed tomography (CT) system. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0651 Authors George Tsigkourakos, Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Leicester-shire, LE11 3TU, UK Vadim V. Silberschmidt, Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Leicester-shire, LE11 3TU, UK Ian A. Ashcroft, Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Leicester-shire, LE11 3TU, UK Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The study describes recent simulation results for underwater explosions in close-proximity to rigid targets. Simulations are performed using Chinook, an Eulerian computational fluid dynamics (CFD) code. Predicted target loadings are compared with measurements taken from a series of experiments conducted under an international collaboration between Canada, The Netherlands, and Sweden. The simulations of the rigid target tests focused on the modelling of gas bubble collapse and water jetting behaviour. Both two-dimensional and three-dimensional simulations were performed. It was found that the two-dimensional analyses produced good bubble periods and reasonable impulse loading compared to experimental data. The time of arrival of the bubble collapse and water jetting were found to be very mesh dependent and refining the mesh did not always produce better results. The two-dimensional approach provides a good initial understanding of the problem for a reasonable computational effort. The three-dimensional simulations were found to produce improved impulse predictions. The numerical gas bubble radii time histories are also compared to empirical time histories. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0650 Authors Mark Riley, Defence Research and Development Canada – Atlantic, Dartmouth, N.S. Malcolm Smith, Defence Research and Development Canada – Atlantic, Dartmouth, N.S. J.E. van Aanhold, TNO, Delft Niklas Alin, FOI Defence and Security Systems and Technology – Grindsjön Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Transverse non-linear vibration is investigated in principal parametric resonance of an axially accelerating viscoelastic beam. The axial speed is characterized as a simple harmonic variation about a constant mean speed. The material time derivative is used in the viscoelastic constitutive relation. The transverse motion can be governed by a non-linear partial-differential equation or a non-linear integro-partial-differential equation. The method of multiple scales is applied to the governing equations to determine steady-state responses. It is confirmed that the mode uninvolved in the resonance has no effect on the steady-state response. The differential quadrature schemes are developed to verify results via the method of multiple scales. It is demonstrated that the straight equilibrium configuration becomes unstable and a stable steady-state emerges when the axial speed variation frequency is close to twice any linear natural frequency. The results derived for two governing equations are qualitatively the same, but quantitatively different. Numerical simulations are presented to examine the effects of the mean speed and the variation of the amplitude of the axial speed, the dynamic viscosity, the non-linear coefficients, and the boundary constraint stiffness on the instability interval and the steady-state response amplitude. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0648 Authors Li-Qun Chen, Department of Mechanics, Shanghai University, Shanghai 200444, China Hu Ding, Department of Mechanics, Shanghai University, Shanghai 200444, China C.W. Lim, Department of Building and Construction, City University of Hong Kong, Kowloon, Hong Kong, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Space inflatable technology is a promising solution to placing large metrology systems in space. Lighter weight, higher packaging efficiency, and easier maintenance are among a few of their advantages over mechanically deployed structures. On the other hand, their large volume after deployment makes them susceptible to disturbances in space. Therefore, vibration control is one major issue for this technology. The present work is an extension of the previous work of the author on continuum modeling of these structures for their vibrations analysis. Kinetic and strain energy expressions of the fundamental lattice elements of a structure are expanded in terms of the nodal displacement components. Certain assumptions are made to reduce the order of strain components in a three-dimensional structure in order to find the equivalent continuum model. Additionally, this work includes the effects of strain rates on the kinetics of these structures. The frequency results for various structures are compared to those of a previous model which neglects such effects. It is shown that the frequency changes are noticeable when the strain rate components are included in the kinetic energy derivations. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0649 Authors A. Salehian, Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1, USA. Tel.: +1 519 888 4567, Ext. 38531; Fax: +1 519 888 4333; E-mail: salehian@uwaterloo.ca Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The current paper presents the results of a ship impact study conducted using various analytical approaches available in the literature with the results obtained from detailed finite element analysis. Considering a typical container vessel impacting a rigid wall with an initial speed of 10 knots, the study investigates the forces imparted on the struck obstacle, the energy dissipated through inelastic deformation, penetration, local deformation patterns, and local failure of the ship elements. The main objective of the paper is to study the accuracy and generality of the predictions of the vessel collision forces, obtained by means of analytical closed-form solutions, in reference to detailed finite element analyses. The results show that significant discrepancies between simplified analytical approaches and detailed finite element analyses can occur, depending on the specific impact scenarios under consideration. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0647 Authors Pawel Woelke, Weidlinger Associates, Inc., 375 Hudson Street, New York, NY, USA Najib Abboud, Weidlinger Associates, Inc., 375 Hudson Street, New York, NY, USA Darren Tennant, Weidlinger Associates, Inc., 6301 Indian School Rd NE, Albuquerque, NM, USA Eric Hansen, Weidlinger Associates, Inc., 6301 Indian School Rd NE, Albuquerque, NM, USA Chad Mcarthur, Weidlinger Associates, Inc., 6301 Indian School Rd NE, Albuquerque, NM, USA Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Nonlinear response history analyses (NRHA) of a 3-story isolated reinforced concrete (RC) building are carried out under both uni- and bi-directional earthquake excitations of near-field records. NRHA are conducted for a wide range of yield strength (Q/W) of lead rubber bearings (LRB), and isolation period (T). Selected near-field records are used to investigate both the contribution of orthogonal components on maximum isolator displacements and accuracy of equivalent lateral force (ELF) procedure on estimation of maximum isolator displacements. Analyses results show that both the contribution of orthogonal components and accuracy of ELF procedure depend on the soil condition where isolation system is implemented. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0646 Authors Gokhan Ozdemir, Graduate Research Associate, Ph.D., Middle East Technical University, Department of Civil Engineering Ugurhan Akyuz, Professor, Middle East Technical University, Department of Civil Engineering Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Wind and gravity both impact trees in storms, but wind loads greatly exceed gravity loads in most situations. Complex behavior of trees in windstorms is gradually turning into a controversial concern among ecological engineers. To better understand the effects of nonlinear behavior of trees, the dynamic forces on tree structures during periods of high winds have been examined as a mass-spring system. In fact, the simulated dynamic forces created by strong winds are studied in order to determine the responses of the trees to such dynamic loads. Many of such nonlinear differential equations are complicated to solve. Therefore, this paper focuses on an accurate and simple solution, Differential Transformation Method (DTM), to solve the derived equation. In this regard, the concept of differential transformation is briefly introduced. The approximate solution to this equation is calculated in the form of a series with easily computable terms. Then, the method has been employed to achieve an acceptable solution to the presented nonlinear differential equation. To verify the accuracy of the proposed method, the obtained results from DTM are compared with those from the numerical solution. The results reveal that this method gives successive approximations of high accuracy solution. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0654 Authors H. Doumiri Ganji, Department of Agriculture and natural resource, Islamic Azad University, Science and Research Branch, Tehran, Iran S.S. Ganji, Department of Transportation Engineering, Islamic Azad University, Science and Research Branch, Tehran, Iran D.D. Ganji, Department of Mechanical Engineering, Babol University of Technology, P.O. Box 484, Babol, Iran F. Vaseghi, Department of Industerial Engineering, Iran University of Science and Technology, Tehran, Iran Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Damage localization is a primary objective of damage identification. This paper presents damage localization in beam structure using impact-induced Lamb wave and Frequency Slice Wavelet Transform (FSWT). FSWT is a new time-frequency analysis method and has the adaptive resolution feature. The time-frequency resolution is a vital factor affecting the accuracy of damage localization. In FSWT there is a unique parameter controlling the time-frequency resolution. To improve the accuracy of damage localization, a generalized criterion is proposed to determine the parameter value for achieving a suitable time-frequency resolution. For damage localization, the group velocity dispersion curve (GVDC) of A_{0} Lamb waves in beam is first accurately estimated using FSWT, and then the arrival time of reflection wave from the crack for some individual frequency component is determined. An average operation on the calculated propagation distance is then performed to further improve the accuracy of damage localization. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0652 Authors Xinglong Liu, National Engineering Laboratory for System Integration of High Speed Train, CSR Qingdao Sifang Locomotive & Rolling Stock, Co., Ltd, Qingdao, China Zhongwei Jiang, Department of Mechanical Engineering, Engineering Faculty, Yamaguchi University, Ube, Japan Zhonghong Yan, Biomedical Department, Chongqing University of Technology, Chongqing, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: In this paper, a new beam shape function configuration method for determining transient responses of a finite Euler-Bernoulli beam with two intermediate supports excited by moving pressure wave loads is developed. To clarify this method, this beam structure is excited by the moving sinusoidal loads as an example. Transient responses of this beam structure are investigated and verified by the traditional finite element method. This method can be used to solve transient response problems of moving pressure loads exciting the beam structure with intermediate support. Actually it can be extended to solve other complicated beam structure problems. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0682 Authors Biaobiao Zhang, Department of Mechanical Engineering, The University of Alabama, Tuscaloosa, AL, USA Steve Shepard, Department of Mechanical Engineering, The University of Alabama, Tuscaloosa, AL, USA Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: An analytical approach is presented to obtain the sloshing natural frequencies and modes of ideal liquid in a rigid cylindrical container with a rigid annular baffle. The free surface waves of the liquid are considered in the analysis. The artificial interfaces are introduced to divide the complicated liquid domain into several simple sub-domains. The exact analytical solutions of velocity potential of liquid corresponding to every sub-domain are obtained by using the method of separation of variables and the superposition principle. The Eigen-frequency equation is precisely derived by using the Fourier-Bessel expansion on the free surface and the artificial interfaces of the liquid. The convergence study shows high accuracy and fast convergence of the present approach. The comparative studies with those available from literature are made, excellent agreements have been achieved. Numerical results showing the variations of natural frequencies and modes versus position and inner diameter of the annular baffle are provided. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0681 Authors J.D. Wang, College of Civil Engineering, Nanjing University of Technology, Nanjing, China D. Zhou, College of Civil Engineering, Nanjing University of Technology, Nanjing, China W.Q. Liu, College of Civil Engineering, Nanjing University of Technology, Nanjing, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Vibration signals acquired from bearing have been found to demonstrate complicated nonlinear characteristics in literature. Fractal geometry theory has provided effective tools such as fractal dimension for characterizing the vibration signals in bearing faults detection. However, most of the natural signals are not critical self-similar fractals; the assumption of a constant fractal dimension at all scales may not be true. Motivated by this fact, this work explores the application of the multi-scale fractal dimensions based on morphological cover (MC) technique for bearing fault diagnosis. Vibration signals from bearing with seven different states under four operations conditions are collected to validate the presented MFD based on MC technique. Experimental results reveal that the vibration signals acquired from bearing are not critical self-similar fractals. The MFD can provide more discriminative information about the signals than the single global fractal dimension. Furthermore, three classifiers are employed to evaluate and compare the classification performance of the MFD with other feature extraction methods. Experimental results demonstrate the MFD to be a desirable approach to improve the performance of bearing fault diagnosis. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0679 Authors Bing Li, Forth department, Mechanical Engineering College, Shi Jia zhuang, HeBei, China Pei-Lin Zhang, First department, Mechanical Engineering College, Shi Jia zhuang, HeBei, China Shuang-Shan Mi, Forth department, Mechanical Engineering College, Shi Jia zhuang, HeBei, China Ying-Tang Zhang, First department, Mechanical Engineering College, Shi Jia zhuang, HeBei, China Dong-Sheng Liu, Forth department, Mechanical Engineering College, Shi Jia zhuang, HeBei, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The nonlinear vibration of a rotor excited by transverse electromagnetic and oil-film forces is presented in this paper. The rotor-bearing system is modeled as a continuum beam which is loaded by a distributed electromagnetic load and is supported by two oil-film bearings. The governing equation of motion is derived and discretized as a group of ordinary differential equations using the Galerkin's method. The stability of the equilibrium of the rotor is analyzed with the Routh-Hurwitz criterion and the occurrence of the Andronov-Hopf bifurcation is pointed out. The approximate solution of periodic motion is obtained using the averaging method. The stability of steady response is analyzed and the amplitude-frequency curve of primary resonance is illustrated. The Runge-Kutta method is adopted to numerically solve transient response of the rotor-bearing system. Comparisons are made to present influences of electromagnetic load, oil-film force and both of them on the nonlinear vibration response. Bifurcation diagrams of the transverse motion versus rotation speed, electromagnetic parameter and bearing parameters are provided to show periodic motion, quasi-periodic motion and period-doubling bifurcations. Diagrams of time history, shaft orbit, the Poincaré section and fast Fourier transformation of the transverse vibration are presented for further understanding of the rotor response. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0671 Authors Haiyang Luo, State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian, China Yuefang Wang, State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Sloshing response of liquid in a rigid cylindrical container with a rigid annual baffle subjected to lateral excitation has been studied. The complicated liquid domain is separated into several simple sub-domains by introducing the artificial interfaces. The analytical solutions of potential function corresponding to every sub-domain are obtained by using the method of separation of variables and the superposition principle. The total potential function under lateral excitation is taken as the sum of the container potential function and the liquid perturbed function. The expression of the liquid perturbed function is obtained by introducing the generalized coordinates. On the base of the natural frequencies and modes having been obtained by the sub-domain method, the orthogonality among the sloshing modes has been demonstrated. Substituting the potential functions into the free surface wave equation establishes the dynamic response equation of liquid. Then, the generalized coordinates are solved. The sloshing surface displacement, the hydrodynamic pressure distribution, the resultant hydrodynamic force and moment are discussed for the containers subjected to harmonic and seismic lateral excitation, respectively. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0674 Authors J.D. Wang, College of Civil Engineering, Nanjing University of Technology, Nanjing, Jiangsu, China D. Zhou, College of Civil Engineering, Nanjing University of Technology, Nanjing, Jiangsu, China W.Q. Liu, College of Civil Engineering, Nanjing University of Technology, Nanjing, Jiangsu, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: A feasibility study of friction base isolation system for seismic protection has been performed. Four different sliding interfaces, namely, green marble/High Density Poly Ethylene (HDPE), green marble/green marble, green marble/geosynthetic, and green marble/ rubber layers have been studied through experimental and analytical investigations. The experimental investigations show that the coefficient of friction values of these interfaces lies in the desirable range for seismic protection, i.e., 0.05 to 0.15. The analytical investigation reveals that most of these sliding interfaces are effective in reducing spectral accelerations up to 50% and the sliding displacement is restricted within plinth projection of 75 mm (3 in). Green marble and geosynthetic are found to be better alternatives for use in friction isolation system with equal effectiveness of energy dissipation and limiting the earthquake energy transmission to super structure during strong earthquake leading to a low cost, durable solution for earthquake protection of masonry buildings. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0675 Authors Radhikesh P. Nanda, Department of Civil Engineering, National Institute of Technology Durgapur, Durgapur, India Pankaj Agarwal, Department of Earthquake Engineering, Indian Institute of Technology Roorkee, Roorkee, India Manish Shrikhande, Department of Earthquake Engineering, Indian Institute of Technology Roorkee, Roorkee, India Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: In the presented work, a non linear effect of rubber referred as Fletcher-Gent effect or Payne effect is investigated. It leads to a change in the rubber dynamic modulus with vibration amplitudes and, consequently, modifies resonance frequencies of mechanical systems including non linear elastomers. In this study a new methodology is developed to take into account Payne effect in a linear viscoelastic rubber material. Small vibration amplitudes around a no-preloaded state are predicted by considering frequency and amplitude dependencies of the material. This methodology has the advantage of using tabular experimental data from characterization tests which avoids the development of a complex model. In order to compute frequency responses, the non linear harmonic balance method is used and, for each iteration, new rubber properties are affected at each element according to its strain state. An equivalent strain measure is evaluated from the element strain energy density. This equivalent strain allows to associate dynamic properties of a material element subjected to multiaxial strain state with experimental dynamic properties of a material sample subjected to an uniaxial strain state. Practically, DMAP alter procedures are developed in order to evaluate energies in models defined with MSC.Nastran and the non linear solver is developed with Matlab. The method is applied on a satellite instrument isolator including four non linear rubber mounts. A non homogeneous spatial distribution of element equivalent strains is observed. Moreover, the maximum equivalent strain varies with frequency. These two observations validate the use of a specific methodology to deal with amplitude dependency of rubber. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0670 Authors V. Jaumouillé, Laboratoire de Tribologie et Dynamique des Syst\`emes UMR-CNRS 5513, Ecole Centrale de Lyon, Ecully Cedex, France J.-J. Sinou, Laboratoire de Tribologie et Dynamique des Syst\`emes UMR-CNRS 5513, Ecole Centrale de Lyon, Ecully Cedex, France B. Petitjean, EADS Innovation Works, Suresnes, France Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: In this study, the geometrically nonlinear dynamic behaviour of simply supported tapered laminated composite plates subjected to the air blast loading is investigated numerically. In-plane stiffness, inertia and the geometric nonlinearity effects are considered in the formulation of the problem. The equations of motion for the tapered laminated plate are derived by the use of the virtual work principle. Approximate solution functions are assumed for the space domain and substituted into the equations of motion. Then, the Galerkin method is used to obtain the nonlinear algebraic differential equations in the time domain. The resulting equations are solved by using the finite difference approximation over the time. The effects of the taper ratio, the stacking sequence and the fiber orientation angle on the dynamic response are investigated. The displacement-time and strain-time histories are obtained on certain points in the tapered direction. The results obtained by using the present method are compared with the ones obtained by using a commercial finite element software ANSYS. The results are found to be in an agreement. The method presented here is able to determine the nonlinear dynamic response of simply supported tapered laminated plates to the air blast loading accurately. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0667 Authors Sedat Susler, Istanbul Technical University, Faculty of Aeronautics and Astronautics, Maslak, Istanbul, Turkey Halit S. Turkmen, Istanbul Technical University, Faculty of Aeronautics and Astronautics, Maslak, Istanbul, Turkey Zafer Kazancı, Turkish Air Force Academy, Aerospace Engineering Department, Yesilyurt, Istanbul, Turkey Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Free vibration equations for non-cylindrical (conical, barrel, and hyperboloidal types) helical springs with noncircular cross-sections, which consist of 14 first-order ordinary differential equations with variable coefficients, are theoretically derived using spatially curved beam theory. In the formulation, the warping effect upon natural frequencies and vibrating mode shapes is first studied in addition to including the rotary inertia, the shear and axial deformation influences. The natural frequencies of the springs are determined by the use of improved Riccati transfer matrix method. The element transfer matrix used in the solution is calculated using the Scaling and Squaring method and Pad'e approximations. Three examples are presented for three types of springs with different cross-sectional shapes under clamped-clamped boundary condition. The accuracy of the proposed method has been compared with the FEM results using three-dimensional solid elements (Solid 45) in ANSYS code. Numerical results reveal that the warping effect is more pronounced in the case of non-cylindrical helical springs than that of cylindrical helical springs, which should be taken into consideration in the free vibration analysis of such springs. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0677 Authors A.M. Yu, School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai, China Y. Hao, School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: A three-dimensional elasticity-based continuum model is developed for describing the free vibrational characteristics of an important class of isotropic, homogeneous, and completely free structural bodies (i.e., finite cylinders, solid spheres, and rectangular parallelepipeds) containing an arbitrarily located simple inhomogeneity in form of a spherical or cylindrical defect. The solution method uses Ritz minimization procedure with triplicate series of orthogonal Chebyshev polynomials as the trial functions to approximate the displacement components in the associated elastic domains, and eventually arrive at the governing eigenvalue equations. An extensive review of the literature spanning over the past three decades is also given herein regarding the free vibration analysis of elastic structures using Ritz approach. Accuracy of the implemented approach is established through proper convergence studies, while the validity of results is demonstrated with the aid of a commercial FEM software, and whenever possible, by comparison with other published data. Numerical results are provided and discussed for the first few clusters of eigen-frequencies corresponding to various mode categories in a wide range of cavity eccentricities. Also, the corresponding 3D mode shapes are graphically illustrated for selected eccentricities. The numerical results disclose the vital influence of inner cavity eccentricity on the vibrational characteristics of the voided elastic structures. In particular, the activation of degenerate frequency splitting and incidence of internal/external mode crossings are confirmed and discussed. Most of the results reported herein are believed to be new to the existing literature and may serve as benchmark data for future developments in computational techniques. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0676 Authors Seyyed M. Hasheminejad, Acoustics Research Laboratory, Department of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran, Iran Yaser Mirzaei, Department of Mechanical Engineering, Damavand Branch, Islamic Azad University, Damavand, Iran Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The variational iteration method (VIM) for determining periodic solutions of non-linear jerk equations involving third-order time-derivative is presented. This method is based on the use of Lagrange multipliers for identification of optimal value of a parameter in a functional. We propose first-order approximate VIM solution for this equation and we compare this solution with the solution obtained by harmonic balance method. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-00749 Authors Behrouz Raftari, Department of Mathematics, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran. E-mail: behrouz.arftari@gmail.com Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The dynamics of a system and its safety can be considerably affected by the presence of cracks. Health monitoring strategies attract so a great deal of interest from industry. Cracks detection methods based on modal parameters variation are particularly efficient in the case of large cracks but are difficult to implement in the case of small cracks due to measurement difficulties in the case of small parameters variation. Therefore the present study proposes a new method to detect small cracks based on active modal damping and piezoelectric components. This method uses the active damping variation identificated with the Rational Fraction Polynomial algorithm as an indicator of cracks detection. The efficiency of the proposed method is demonstrated through numerical simulations corresponding to different crack depth and locations in the case of a finite element model of a clamped-clamped beam including four piezoelectric transducers. Content Type Journal Article Pages - DOI 10.3233/SAV-130772 Authors B. Chomette, Institut d'Alembert, UMR, CNRS, Paris, France A. Fernandes, Institut d'Alembert, UMR, CNRS, Paris, France J.-J. Sinou, Laboratoire de Tribologie et Dynamique des Systèmes UMR-CNRS, Ècole Centrale de Lyon, Ecully, France Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: In this paper four semi-active dynamic vibration absorbers (DVAs) are analytically studied, where the time delay induced by measurement and execution in control procedure is included in the system. The first-order approximate analytical solutions of the four semi-active DVAs are established by the averaging method, based on the illustrated phase difference of the motion parameters. The comparisons between the analytical and the numerical solutions are carried out, which verify the correctness and satisfactory precision of the approximate analytical solutions. Then the effects of the time delay on the dynamical responses are analyzed, and it is found that the stability conditions for the steady-state responses of the primary systems are all periodic functions of time delay, with the same period as the excitation one. At last the effects of time delay on control performance are discussed. Content Type Journal Article Pages - DOI 10.3233/SAV-130774 Authors Yongjun Shen, Department of Mechanical Engineering, Shijiazhuang Tiedao University, Shijiazhuang, Hebei, China Mehdi Ahmadian, Center for Vehicle Systems and Safety, Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The traditional beam element was improved to consider the variable axial parameters. The variable axial parameters were formulated in terms of a power series, and the general forms of elementary mass and stiffness matrices which depend on the power order were derived. The mass and stiffness matrices of the improved beam element were obtained in terms of an elementary matrix series. The beam elements for various tapered beams and a beam under linearly axial temperature distribution were derived. The vibrations of the beams with various taper shapes were studied and the variations of natural frequencies and modal shapes were investigated. A uniform beam under linearly axial temperature distribution was modeled and studied. The influences of axial temperature difference on the natural frequencies and modal shapes were investigated. Results show that the improved beam element could consider the variable axial parameters of beam conveniently. Content Type Journal Article Pages - DOI 10.3233/SAV-130771 Authors Peng He, School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, China Zhansheng Liu, School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, China Chun Li, School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Vibration analysis is an accepted method in condition monitoring of machines, since it can provide useful and reliable information about machine working condition. This paper surveys a new scheme for fault diagnosis of main journal-bearings of internal combustion (IC) engine based on power spectral density (PSD) technique and two classifiers, namely, K-nearest neighbor (KNN) and artificial neural network (ANN). Vibration signals for three different conditions of journal-bearing; normal, with oil starvation condition and extreme wear fault were acquired from an IC engine. PSD was applied to process the vibration signals. Thirty features were extracted from the PSD values of signals as a feature source for fault diagnosis. KNN and ANN were trained by training data set and then used as diagnostic classifiers. Variable K value and hidden neuron count (N) were used in the range of 1 to 20, with a step size of 1 for KNN and ANN to gain the best classification results. The roles of PSD, KNN and ANN techniques were studied. From the results, it is shown that the performance of ANN is better than KNN. The experimental results dèmonstrate that the proposed diagnostic method can reliably separate different fault conditions in main journal-bearings of IC engine. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-00742 Authors A. Moosavian, Department of Mechanical Engineering of Agricultural Machinery, University of Tehran, Karaj, Iran H. Ahmadi, Department of Mechanical Engineering of Agricultural Machinery, University of Tehran, Karaj, Iran A. Tabatabaeefar, Department of Mechanical Engineering of Agricultural Machinery, University of Tehran, Karaj, Iran M. Khazaee, Department of Mechanical Engineering of Agricultural Machinery, University of Tehran, Karaj, Iran Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This paper presents theoretical and experimental studies of H_{&infty;} control of a flexible plate with time delay. A matrix inequality used for stability analysis is proposed and proved by using the Lyapunov-Krasovskii functional and free-weighting matrix. An H_{&infty;} controller is designed based on the matrix inequality and by using the parameter-adjusting method. Three control scenarios are discussed in detail by transforming the problem into parameters optimization: (i) controller design when maximum time delay of the system is known; (ii) allowable time delay when controller is known; (iii) the biggest allowable time delay to guarantee system stability when controller is unknown. Numerical simulations and experiments are also given to demonstrate the validity and feasibility of the proposed methods in this paper. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-00740 Authors Tong Zhao, Department of Engineering Mechanics, State Key Laboratory of Ocean Engineering, Shanghai Jiaotong University, Shanghai, China Long-Xiang Chen, Department of Engineering Mechanics, State Key Laboratory of Ocean Engineering, Shanghai Jiaotong University, Shanghai, China Guo-Ping Cai, Department of Engineering Mechanics, State Key Laboratory of Ocean Engineering, Shanghai Jiaotong University, Shanghai, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Control of seismic response of a building fitted with magnetorheological dampers is considered using Optimal Static Output Feedback (OSOF) for desired damper forces. The Modified Bouc-Wen damper model is used and two control voltage laws based on the MR constraint filter, i.e., Semi-inverse Quadratic Voltage Law and Semi-inverse On-Off Voltage Law, are proposed. These appear to perform at least as well as an existing Clipped Voltage Law. Comparisons with available results from a robust reliability-based controller show OSOF control to be quite effective. Controlled response using OSOF is compared with Linear Quadratic Guassian (LQG) and passive-on controllers. Moderate to substantial reduction in maximum peak/RMS responses is mostly obtained with base configuration of sensors when using OSOF control, and controller CPU time reduces by two orders of magnitude. Parametric studies regarding sensor configuration and state/control weighting matrices are performed in order to obtain effective control. Effective OSOF control requires drift feedback with drift sensor preferably collocated with damper. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0684 Authors N.K. Chandiramani, Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai, India S.P. Purohit, Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai, India Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This paper developed an effective optimization method, i.e., Gradient-Hessian matrix-based method or second order method, of frame structures subjected to the transient loads. An algorithm of first and second derivatives of dynamic displacement and stress with respect to design variables is formulated based on the Newmark method. The inequality time-dependent constraint problem is converted into a sequence of appropriately formed time-independent unconstrained problems using the integral interior point penalty function method. The gradient and Hessian matrixes of the integral interior point penalty functions are also computed. Then the Marquardt's method is employed to solve unconstrained problems. The numerical results show that the optimal design method proposed in this paper can obtain the local optimum design of frame structures and sometimes is more efficient than the augmented Lagrange multiplier method. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0685 Authors Qimao Liu, Department of Civil and Structural Engineering, Aalto University, Espoo, Aalto, Finland Jing Zhang, Department of Mechanical Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, IN, USA Liubin Yan, College of Civil and Architecture Engineering, Guangxi University, Nanning, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The potential of using topology optimization as a tool to optimize the passive constrained layer damping (PCLD) layouts with partial coverage on flat plates is investigated. The objective function is defined as a combination of several modal loss factors solved by finite element-modal strain energy (FE-MSE) method. An interface finite element is introduced to modeling the viscoelastic core of PCLD patch to save the computational space and time in the optimization procedure. Solid isotropic material with penalization (SIMP) method is used as the material interpolation scheme and the parameters are well selected to avoid local pseudo modes. Then, the method of moving asymptote (MMA) is employed as an optimizer to search the optimal topologies of PCLD patch on plates. Applications of two flat plates with different shapes have been applied to demonstrate the validation of the proposed approach. The results show that the objective function is in a steady convergence process and the damping effect of the plates can be enhanced by the optimized PCLD layouts. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0738 Authors Weiguang Zheng, State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, China Yingfeng Lei, State Key Lab of Vehicle NVH and Safety Technology, Chongqing, China Shande Li, State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, China Qibai Huang, State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The authors recently developed a damage identification method which combines ambient vibration measurements and a Statistical Modal Filtering approach to predict the location and degree of damage. The method was then validated experimentally via ambient vibration tests conducted on full-scale reinforced concrete laboratory specimens. The main purpose of this paper is to demonstrate the feasibility of the identification method for a real bridge. An important challenge in this case is to overcome the absence of vibration measurements for the structure in its undamaged state which corresponds ideally to the reference state of the structure. The damage identification method is, therefore, modified to adapt it to the present situation where the intact state was not subjected to measurements. An additional refinement of the method consists of using a genetic algorithm to improve the computational efficiency of the damage localization method. This is particularly suited for a real case study where the number of damage parameters becomes significant. The damage diagnosis predictions suggest that the diagnosed bridge is damaged in four elements among a total of 168 elements with degrees of damage varying from 6% to 18%. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0736 Authors S. El-Ouafi Bahlous, Applied Mechanics and Systems Research Laboratory, Tunisia Polytechnic School, University of Carthage, La Marsa, Tunisia M. Neifar, Applied Mechanics and Systems Research Laboratory, Tunisia Polytechnic School, University of Carthage, La Marsa, Tunisia S. El-Borgi, Applied Mechanics and Systems Research Laboratory, Tunisia Polytechnic School, University of Carthage, La Marsa, Tunisia H. Smaoui, Laboratory of Materials, Energy and Optimization for Sustainability, ENIT, University of El Manar, Tunis, Tusia Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This study investigates both the static and dynamic behaviors for the uniform beam supported at its ends by rotational supports. The stiffness coefficients of these supports are treated as interval variables. It is first demonstrated on the static problem that the classical interval analysis may lead to overestimation of the response. The paper introduces a remedy for this "ill" of the classical interval analysis. The artificial interval parameter is introduced and the extrema of the static displacements and natural frequencies are determined. Finally, the hybrid case of uncertain boundary conditions and uncertain mass density is treated with attendant interesting results. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0733 Authors Isaac Elishakoff, Department of Ocean and Mechanical Engineering, Florida Atlantic University, Boca Raton, FL, USA Clément Soret, Institut Français de Mécanique Avancée, Aubière, France Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Nearly a century ago, the liquid self-balancing device was first introduced by M. LeBlanc for passive balancing of turbine rotors. Although of common use in many types or rotating machines nowadays, little information is available on the unbalance response and stability characteristics of this device. Experimental fluid flow visualization evidences that radial and traverse circulatory waves arise due to the interaction of the fluid backward rotation and the baffle boards within the self-balancer annular cavity. The otherwise destabilizing force induced by trapped fluids in hollow rotors, becomes a stabilizing mechanism when the cavity is equipped with adequate baffle boards. Further experiments using Particle Image Velocimetry (PIV) enable to assess the active fluid mass fraction to be one-third of the total fluid mass. An analytical model is introduced to study the effects of the active fluid mass fraction on a flexible rotor supported by flexible supports excited by bwo different destabilizing mechanisms; rotor internal friction damping and aerodynamic cross-coupling. It is found that the fluid radial and transverse forces contribute to the balancing action and to improve the rotor stability, respectively. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0731 Authors Leonardo Urbiola-Soto, Department of Mechanical Engineering, Universidad Nacional Autonoma de Mexico (UNAM), Campus Juriquilla, Queretaro, Mexico Marcelo Lopez-Parra, Department of Mechanical Engineering, Universidad Nacional Autonoma de Mexico (UNAM), Campus Juriquilla, Queretaro, Mexico Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Current practices for modeling the ocean floor in underwater explosion simulations call for application of an inviscid fluid with soil properties. A method for modeling the ocean floor as a Lagrangian solid, vice an Eulerian fluid, was developed in order to determine its effects on underwater explosions in shallow water using the DYSMAS solver. The Lagrangian solid bottom model utilized transmitting boundary segments, exterior nodal forces acting as constraints, and the application of prestress to minimize any distortions into the fluid domain. For simplicity, elastic materials were used in this current effort, though multiple constitutive soil models can be applied to improve the overall accuracy of the model. Even though this method is unable to account for soil cratering effects, it does however provide the distinct advantage of modeling contoured ocean floors such as dredged channels and sloped bottoms absent in Eulerian formulations. The study conducted here showed significant differences among the initial bottom reflections for the different solid bottom contours that were modeled. The most important bottom contour effect was the distortion to the gas bubble and its associated first pulse timing. In addition to its utility in bottom modeling, implementation of the non-reflecting boundary along with realistic material models can be used to drastically reduce the size of current fluid domains. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0737 Authors A.P. Walters J.M. Didoszak Y.W. Kwon Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The so-called Adaptive Impact Absorption (AIA) is a research area of safety engineering devoted to problems of shock absorption in various unpredictable scenarios of collisions. It makes use of smart technologies (systems equipped with sensors, controllable dissipaters and specialised tools for signal processing). Examples of engineering applications for AIA systems are protective road barriers, automotive bumpers or adaptive landing gears. One of the most challenging problems for AIA systems is on-line identification of impact loads, which is crucial for introducing the optimum real-time strategy of adaptive impact absorption. This paper presents the concept of an impactometer and develops the methodology able to perform real-time impact load identification. Considered dynamic excitation is generated by a mass M_{1} impacting with initial velocity V_{0}. An analytical formulation of the problem, supported with numerical simulations and experimental verifications is presented. Two identification algorithms based on measured response of the impacted structure are proposed and discussed. Finally, a concept of the AIA device utilizing the idea of impactometer is briefly presented. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0732 Authors Krzysztof Seku, Institute of Fundamental Technological Research, Warsaw, Poland Cezary Graczykowski, Institute of Fundamental Technological Research, Warsaw, Poland Jan Holnicki-Szulc, Institute of Fundamental Technological Research, Warsaw, Poland Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This work deals with the design and the assessment of electromagnetic actuators (EMAs) for the control of rotating machines. The system studied has a hybrid bearing that exhibits nonlinear behavior. The system is composed of a horizontal flexible shaft supported by two ball bearings at one end and a roller bearing that is located in a squirrel cage at the other end. Four identical EMAs supplied with constant current are utilized. The EMAs associated to the squirrel cage constitutes the hybrid bearing. The aim is to develop a strategy in order to define and to identify a reliable model necessary for the control of rotating machinery in the presence of localized non-linearity. The identification strategy consists in modeling the system with as many sub-models as needed that are identified separately. This enables obtaining a straightforward modeling of rotating machinery even in the case in which system components are frequency or time dependent. For the system studied, two sub-models were necessary. First the EMAs were modeled by using classical equations of electromagnetism and then identified experimentally. Then, a linear model of the shaft mounted on its bearings was defined by using the finite element method and was identified successfully. The model of the system was adjusted after assembling the different identified sub-models. The identification is carried out by using a pseudo-random search algorithm. The model of the system is then assessed for different configurations. The results obtained demonstrate the effectiveness of the developed strategy. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0735 Authors T.S. Morais, Federal University of Uberlândia, School of Mechanical Engineering, Campus Santa Monica, Uberlândia, Brazil J. Der Hagopian, Université de Lyon, Laboratoire de Mécanique des Contacts et des Structures, Institut National des Sciences Appliquées de Lyon, Lyon, France V. Steffen, Jr., Federal University of Uberlândia, School of Mechanical Engineering, Campus Santa Monica, Uberlândia, Brazil J. Mahfoud, Université de Lyon, Laboratoire de Mécanique des Contacts et des Structures, Institut National des Sciences Appliquées de Lyon, Lyon, France Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Classical component mode synthesis methods for reduction are usually limited by the size and compatibility of the coupling interfaces. A component mode synthesis approach with constrained coupling interfaces is presented for vibro-acoustic modelling. The coupling interfaces are constrained to six displacement degrees of freedom. These degrees of freedom represent rigid interface translations and rotations respectively, retaining an undeformed interface shape. This formulation is proposed for structures with coupling between softer and stiffer substructures in which the displacement is chiefly governed by the stiffer substructure. Such may be the case for the rubber-bushing/linking arm assembly in a vehicle suspension system. The presented approach has the potential to significantly reduce the modelling size of such structures, compared with classical component mode synthesis which would be limited by the modelling size of the interfaces. The approach also eliminates problems of nonconforming meshes in the interfaces since only translation directions, rotation axes and the rotation point need to be common for the coupled substructures. Simulation results show that the approach can be used for modelling of systems that resemble a vehicle suspension. It is shown for a test case that adequate engineering accuracy can be achieved when the stiffness properties of the connecting parts are within the expected range of rubber connected to steel. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0734 Authors Eskil Lindberg Nils-Erik Hörlin Peter Göransson Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This paper provides a critical overview of available technology and facilities for determining human-induced dynamic forces of civil engineering structures, such as due to walking, running, jumping and bouncing. In addition to traditional equipment for direct force measurements comprising force plate(s), foot pressure insoles and instrumented treadmills, the review also investigates possibility of using optical motion tracking systems (marker-based and marker-free optoelectronic technology) and non-optical motion tracking systems (inertial sensors) to reproduce contact forces between humans and structures based on body kinematics data and known body mass distribution. Although significant technological advancements have been made in the last decade, the literature survey showed that the state-of-the-art force measurements are often limited to individuals in artificial laboratory environments. Experimental identification of seriously needed group- and crowd-induced force data recorded on as-built structures, such as footbridges, grandstands and floors, still remains a challenge due to the complexity of human actions and the lack of adequate equipment. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0727 Authors Vitomir Racic, Department of Civil and Structural Engineering, University of Sheffield, Sheffield, UK Aleksandar Pavic, Department of Civil and Structural Engineering, University of Sheffield, Sheffield, UK James Mark William Brownjohn, Department of Civil and Structural Engineering, University of Sheffield, Sheffield, UK Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This paper presents the dynamic response of a delaminated composite beam under the action of a moving oscillating mass. In this analysis the Poisson's effect is considered for the first time. Moreover, the effects of rotary inertia and shear deformation are incorporated. In our modeling linear springs are used between delaminated surfaces to simulate the dynamic interaction between sub-beams. To solve the governing differential equations of motion using modal expansion series, eigen-solution technique is used to obtain the natural frequencies and their corresponding mode shapes necessary for forced vibration analysis. The obtained results for the free and forced vibrations of beams are verified against reported similar results in the literatures. Moreover, the maximum dynamic response of such beam is compared with an intact beam. The effects of different parameters such as the velocity of oscillating mass, different ply configuration and the delamination length, its depth and spanwise location on the dynamic response of the beam are studied. In addition, the effects of delamination parameters on the oscillator critical speed are investigated. Furthermore, different conditions under which the detachment of moving oscillator from the beam will initiate are investigated. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0729 Authors M.H. Kargarnovin, School of Mechanical Engineering, Sharif University of Technology, Tehran, Iran M.T. Ahmadian, School of Mechanical Engineering, Sharif University of Technology, Tehran, Iran R.A. Jafari-Talookolaei, School of Mechanical Engineering, Sharif University of Technology, Tehran, Iran Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This paper presents the transverse vibration of Bernoulli-Euler homogeneous isotropic damped beams with general boundary conditions. The beams are assumed to be subjected to a load moving at a uniform velocity. The damping characteristics of the beams are described in terms of fractional derivatives of arbitrary orders. In the analysis where initial conditions are assumed to be homogeneous, the Laplace transform cooperates with the decomposition method to obtain the analytical solution of the investigated problems. Subsequently, curves are plotted to show the dynamic response of different beams under different sets of parameters including different orders of fractional derivatives. The curves reveal that the dynamic response increases as the order of fractional derivative increases. Furthermore, as the order of the fractional derivative increases the peak of the dynamic deflection shifts to the right, this yields that the smaller the order of the fractional derivative, the more oscillations the beam suffers. The results obtained in this paper closely match the results of papers in the literature review. Content Type Journal Article Pages 333-347 DOI 10.3233/SAV-2010-0634 Authors R. Abu-Mallouh, Applied Sciences University, Amman 11931, Jordan I. Abu-Alshaikh, Applied Sciences University, Amman 11931, Jordan H.S. Zibdeh, Jordan University of Science and Technology, Irbid, Jordan Khaled Ramadan, Applied Sciences University, Amman 11931, Jordan Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622 Journal Volume Volume 19 Journal Issue Volume 19, Number 3 / 2012

Description: In this paper, an approach using observability and controllability grammian matrices is proposed to determine if structural damage has occurred together with an estimate of its location. The theory is outlined and simulations are carried out on a simple structure to demonstrate the method. Experimental tests were also carried out to demonstrate the validity of the approach using real signals. The dynamic properties of the structure are identified using the eigensystem realization algorithm (ERA) and a reduced order state-space model of the system subsequently constructed. Either the observability or controllability grammians can then be used depending on the number of sensors available. It is shown that these are sensitive to both the degree and location of the damage and offer promise for structural health monitoring applications. Content Type Journal Article Pages 287-299 DOI 10.3233/SAV-2010-0631 Authors D.D. Bueno, UNESP – Univ Estadual Paulista, Faculdade de Engenharia de Ilha Solteira, Grupo de Materiais e Sistemas Inteligentes – GMSINT, Av. Brasil, n. 56, Centro, 15385-000, Ilha Solteira, SP, Brazil C.R. Marqui, UNESP – Univ Estadual Paulista, Faculdade de Engenharia de Ilha Solteira, Grupo de Materiais e Sistemas Inteligentes – GMSINT, Av. Brasil, n. 56, Centro, 15385-000, Ilha Solteira, SP, Brazil V. Lopes Jr., UNESP – Univ Estadual Paulista, Faculdade de Engenharia de Ilha Solteira, Grupo de Materiais e Sistemas Inteligentes – GMSINT, Av. Brasil, n. 56, Centro, 15385-000, Ilha Solteira, SP, Brazil M.J. Brennan, UNESP – Univ Estadual Paulista, Faculdade de Engenharia de Ilha Solteira, Grupo de Materiais e Sistemas Inteligentes – GMSINT, Av. Brasil, n. 56, Centro, 15385-000, Ilha Solteira, SP, Brazil Daniel J. Inman, Center for Intelligent Material Systems and Structures, Virginia Tech, Blacksburg, VA, USA Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622 Journal Volume Volume 19 Journal Issue Volume 19, Number 3 / 2012

Description: In this paper we study the periodic solutions of free vibration of mechanical systems with third and fifth-order nonlinearity for two examples using He's Frequency-Amplitude Formulation (HFAF).The effectiveness and convenience of the method is illustrated in these examples. It will be shown that the solutions obtained with current method have a fabulous conformity with those achieved from time marching solution. HFAF is easy with powerful concepts and the high accuracy, so it can be found widely applicable in vibrations, especially strong nonlinearity oscillatory problems. Content Type Journal Article Pages 323-332 DOI 10.3233/SAV-2010-0633 Authors A. Fereidoon, Department of Mechanical Engineering, Faculty of Engineering, Semnan University, Semnan, Iran M. Ghadimi, Department of Mechanical Engineering, Babol University of Technology, Babol, Iran A. Barari, Department of Civil Engineering, Aalborg University, Sohngårdsholmsvej 57, 9000 Aalborg, Aalborg, Denmark H.D. Kaliji, Department of Mechanical Engineering, Islamic Azad University, Semnan Branch, Semnan, Iran G. Domairry, Department of Mechanical Engineering, Babol University of Technology, Babol, Iran Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622 Journal Volume Volume 19 Journal Issue Volume 19, Number 3 / 2012

Description: The principal parametric resonance of two van der Pol oscillators under coupled position and velocity feedback control with time delay is investigated analytically and numerically on the assumption that only one of the two oscillators is parametrically excited and the feedback control is linear. The slow-flow equations are obtained by the averaging method and simplified by truncating the first term of Taylor expansions for those terms with time delay. It is found that nontrivial solutions corresponding to periodic motions exist only for one oscillator if no feedback control is applied although the two oscillators are nonlinearly coupled. Based on Levenberg-Marquardt method, the effects of excitation and control parameters on the amplitude of periodic solutions of the system are graphically given. It can be seen that both of the two oscillators can be excited in periodic vibration with proper feedback. However, the amplitudes of the periodic vibrations are independent of the sign of feedback gains. In addition, the influence of time delay on the response of the system is periodic. In terms of numerical simulations, it is shown that both of the two oscillators can also have quasi-periodic motions, periodic motions about a new equilibrium position and other complex motions such as relaxation oscillation when feedback control is considered. Content Type Journal Article Pages 365-377 DOI 10.3233/SAV-2010-0636 Authors Xinye Li, School of Mechanical Engineering, Hebei University of Technology, Tianjin, P.R. China Huabiao Zhang, School of Astronautics, Harbin Institute of Technology, Harbin, P.R. China Lijuan He, School of Mechanical Engineering, Tianjin University of Science and Technology, Tianjin, P.R. China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622 Journal Volume Volume 19 Journal Issue Volume 19, Number 3 / 2012

Description: Design of mechanical systems often necessitates the use of dynamic simulations to calculate the displacements (and their derivatives) of the bodies in a system as a function of time in response to dynamic inputs. These types of simulations are especially prevalent in the shock and vibration community where simulations associated with models having complex inputs are routine. If the forcing functions as well as the parameters used in these simulations are subject to uncertainties, then these uncertainties will propagate through the models resulting in uncertainties in the outputs of interest. The uncertainty analysis procedure for these kinds of time-varying problems can be challenging, and in many instances, explicit data reduction equations (DRE's), i.e., analytical formulas, are not available because the outputs of interest are obtained from complex simulation software, e.g. FEA programs. Moreover, uncertainty propagation in systems modeled using nonlinear differential equations can prove to be difficult to analyze. However, if (1) the uncertainties propagate through the models in a linear manner, obeying the principle of superposition, then the complexity of the problem can be significantly simplified. If in addition, (2) the uncertainty in the model parameters do not change during the simulation and the manner in which the outputs of interest respond to small perturbations in the external input forces is not dependent on when the perturbations are applied, then the number of calculations required can be greatly reduced. Conditions (1) and (2) characterize a Linear Time Invariant (LTI) uncertainty model. This paper seeks to explain one possible approach to obtain the uncertainty results based on these assumptions. Content Type Journal Article Pages 433-446 DOI 10.3233/SAV-2010-0641 Authors J.B. Weathers, Shock, Noise, and Vibration Group, Northrop Grumman Shipbuilding, Pascagoula, MS, USA Rogelio Luck, Department of Mechanical Engineering, Mississippi State University, Mississippi State, MS, USA Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622 Journal Volume Volume 19 Journal Issue Volume 19, Number 3 / 2012

Description: The free transverse vibrations of thin nonhomogeneous rectangular plates of variable thickness have been studied using boundary characteristic orthogonal polynomials in the Rayleigh-Ritz method. Gram-Schmidt process has been used to generate these orthogonal polynomials in two variables. The thickness variation is bidirectional and is the cartesian product of linear variations along two concurrent edges of the plate. The nonhomogeneity of the plate is assumed to arise due to linear variations in Young's modulus and density of the plate material with the in-plane coordinates. Numerical results have been computed for four different combinations of clamped, simply supported and free edges. Effect of the nonhomogeneity and thickness variation with varying values of aspect ratio on the natural frequencies of vibration is illustrated for the first three modes of vibration. Three dimensional mode shapes for all the four boundary conditions have been presented. A comparison of results with those available in the literature has been made. Content Type Journal Article Pages 349-364 DOI 10.3233/SAV-2010-0635 Authors R. Lal, Department of Mathematics, Indian Institute of Technology Roorkee, Roorkee, India Yajuvindra Kumar, Department of Mathematics, Indian Institute of Technology Roorkee, Roorkee, India Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622 Journal Volume Volume 19 Journal Issue Volume 19, Number 3 / 2012

Description: The formulation and solution of the inverse problem of damage identification based on wave propagation approach are presented. Different damage scenarios for a bar are considered. Time history responses, obtained from pulse-echo synthetic experiments, are used to identify damage position, severity and shape. In order to account for noise corrupted data, different levels of signal to noise ratio – varying from 30 to 0 dB – are introduced. In the identification process, different optimization methods are investigated: the deterministic Levenberg-Marquardt; the stochastic Particle Swarm Optimization; and a hybrid technique combining the aforementioned methods. It is shown that the damage identification procedure built on the wave propagation approach was successful, even for highly corrupted noisy data. Test case results are presented and a few comments on the advantages of deterministic and stochastic methods and their combination are also reported. Finally, an experimental validation of the sequential algebraic algorithm, used for modeling the direct problem, is presented. Content Type Journal Article Pages 301-321 DOI 10.3233/SAV-2010-0632 Authors R.A. Tenenbaum, Graduate Program in Computational Modeling, Polytechnic Institute, State University of Rio de Janeiro, Rua Alberto Rangel S/N, Vila Nova, Nova Friburgo, RJ, Brazil K.M. Fernandes, Graduate Program in Computational Modeling, Polytechnic Institute, State University of Rio de Janeiro, Rua Alberto Rangel S/N, Vila Nova, Nova Friburgo, RJ, Brazil L.T. Stutz, Graduate Program in Computational Modeling, Polytechnic Institute, State University of Rio de Janeiro, Rua Alberto Rangel S/N, Vila Nova, Nova Friburgo, RJ, Brazil A.J. Silva Neto, Graduate Program in Computational Modeling, Polytechnic Institute, State University of Rio de Janeiro, Rua Alberto Rangel S/N, Vila Nova, Nova Friburgo, RJ, Brazil Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622 Journal Volume Volume 19 Journal Issue Volume 19, Number 3 / 2012

Description: Recently it has been shown that also transmissibilities can be used to identify the modal parameters. This approach has several advantages: because of the deterministic character of the transmissibility functions, the estimated parameters are more accurate than the results obtained with the power spectra based operational modal analysis techniques. Another advantage is that the transmissibility functions do not depend on the colouring of the unknown forces. A disadvantage of the transmissibility based operational modal analysis techniques is that non-physical modes show up in the stabilisation diagrams. In this contribution it will first be shown that those non-physical modes will show up when traditional stabilisation diagrams are used. In a second step, a new approach of selecting the physical modes out of a set of estimated modes will be discussed and the new approach will be validated using data generated with an acoustical Finite Element Model. Finally, the approach will be validated using real acoustical data. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0714 Authors Gert De Sitter, Vrije Universiteit Brussel, Brussel, Belgium Christof Devriendt, Vrije Universiteit Brussel, Brussel, Belgium Patrick Guillaume, Vrije Universiteit Brussel, Brussel, Belgium Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Stator vanes which are found in axial compressors are subject to vibratory fatigue. Their division into monoblock sectors makes the prediction of their vibratory behaviour difficult by deterministic methods due to the loss of the cyclic symmetry properties and also to a high sensitivity to mistuning. The purpose is to present a robust calculation strategy based on a stochastic modelisation of the structure. The methodology has been developed first on a simplified model and then applied to an industrial case. Polynomial chaos based results are in good agreement with reference Monte Carlo simulations. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0710 Authors A.C. Sall, École Centrale de Lyon, Laboratoire de Tribologie et Dynamique des Systèmes, Écully Cedex, France F. Thouverez, École Centrale de Lyon, Laboratoire de Tribologie et Dynamique des Systèmes, Écully Cedex, France L. Blanc, École Centrale de Lyon, Laboratoire de Tribologie et Dynamique des Systèmes, Écully Cedex, France P. Jean, Snecma, Safran group, Moissy-Cramayel, France Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This paper presents a new semi-analytical solution for the Timoshenko beam subjected to a moving load in case of a nonlinear medium underneath. The finite series of distributed moving loads harmonically varying in time is considered as a representation of a moving train. The solution for vibrations is obtained by using the Adomian's decomposition combined with the Fourier transform and a wavelet-based procedure for its computation. The adapted approximating method uses wavelet filters of Coiflet type that appeared a very effective tool for vibration analysis in a few earlier papers. The developed approach provides solutions for both transverse displacement and angular rotation of the beam, which allows parametric analysis of the investigated dynamic system to be conducted in an efficient manner. The aim of this article is to present an effective method of approximation for the analysis of complex dynamic nonlinear models related to the moving load problems. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0706 Authors Piotr Koziol, Department of Civil and Environmental Engineering, Koszalin University of Technology, Koszalin, Poland Zdzislaw Hryniewicz, Department of Civil and Environmental Engineering, Koszalin University of Technology, Koszalin, Poland Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: During the recent years several new tools have been introduced by the Vrije Universiteit Brussel in the field of Operational Modal Analysis (OMA) such as the transmissibility based approach and the the frequency-domain OMAX concept. One advantage of the transmissibility based approach is that the ambient forces may be coloured (non-white), if they are fully correlated. The main advantage of the OMAX concept is the fact that it combines the advantages of Operational and Experimental Modal Analysis: ambient (unknown) forces as well as artificial (known) forces are processed simultaneously resulting in improved modal parameters. In this paper, the transmissibility based output-only approach is combined with the input/output OMAX concept. This results in a new methodology in the field of operational modal analysis allowing the estimation of (scaled) modal parameters in the presence of arbitrary ambient (unknown) forces and artificial (known) forces. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0713 Authors Christof Devriendt, Acoustic and Vibration Research Group, Vrije Universiteit Brussel, Brussel, Belgium Tim De Troyer, Acoustic and Vibration Research Group, Vrije Universiteit Brussel, Brussel, Belgium Gert De Sitter, Acoustic and Vibration Research Group, Vrije Universiteit Brussel, Brussel, Belgium Patrick Guillaume, Acoustic and Vibration Research Group, Vrije Universiteit Brussel, Brussel, Belgium Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The paper demonstrates the application of guided ultrasonic waves for estimating material elastic properties in multi-layered composite plates. Two-dimensional Lamb wave propagation is modelled using the Local Interaction Simulation Approach (LISA). The wave responses are then used to estimate relevant material properties. This numerical inverse method is based on an optimisation scheme using a Differential Evolution (DE) algorithm. The method is demonstrated on a simulated seven-layered glass fibre-epoxy composite plate. The results show a good agreement between the exact and reconstructed material properties. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0709 Authors A.B. Spencer, Dynamics Research Group, Department of Mechanical Engineering, University of Sheffield, Sheffield, UK K. Worden, Dynamics Research Group, Department of Mechanical Engineering, University of Sheffield, Sheffield, UK W.J. Staszewski, Dynamics Research Group, Department of Mechanical Engineering, University of Sheffield, Sheffield, UK J.A. Rongong, Dynamics Research Group, Department of Mechanical Engineering, University of Sheffield, Sheffield, UK N.D. Sims, Dynamics Research Group, Department of Mechanical Engineering, University of Sheffield, Sheffield, UK Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: A wavelet based approach is proposed in this paper for analysis and optimization of the dynamical response of a multilayered medium subject to a moving load with respect to the material properties and thickness of supporting half-space. The investigated model consists of a load moving along a beam resting on a surface of a multilayered medium with infinite thickness and layers with different physical properties. The theoretical model is described by the Euler-Bernoulli equation for the beam and the Navier's elastodynamic equation of motion for a viscoelastic half-space. The moving load is modelled by a finite series of distributed harmonic loads. A special method based on a wavelet expansion of functions in the transform domain is adopted for calculation of displacements in the physical domain. The interaction between the beam and the multilayered medium is analyzed in order to obtain the vibration response at the surface and the critical velocities associated. The choice of the specific values of the design parameters for each layer, which minimize the vibration response of the multilayered medium, can be seen as a structural optimization problem. A first approach for using optimization techniques to explore the potential of the wavelet model is presented and briefly discussed. Results from the analysis of the vibration response are presented to illustrate the dynamic characterization obtained by using this method. Numerical examples reflecting the results of numerical optimizations with respect to a multilayered medium parameters are also presented. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0707 Authors Piotr Koziol, Department of Civil and Environmental Engineering, Koszalin University of Technology, Koszalin, Poland M.M. Neves, IDMEC-IST, Instituto Superior Técnico, Lisboa, Portugal Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Structures include elements designated as load bearing and non-load bearing. While non-load bearing elements, such as facades and internal partitions, are acknowledged to add mass to the system, the structural stiffness and strength is generally attributed to load bearing elements only. This paper investigates the contribution of non-load bearing elements to the dynamic response of a new structure, the Charles Institute, in the grounds of University College Dublin (UCD) Ireland. The vertical vibration response of the first floor and the lateral response at each floor level were recorded at different construction stages. The evolution of the structural response as well as the generation of a finite element (FE) model is discussed. It was found that the addition of the non-load bearing facades increased the first floor natural frequency from 10.7 Hz to 11.4 Hz, a change of approximately +6.5%. resulted in the first sway mode having its frequency increased by 6%. subsequent addition of internal partitions, mechanical services and furnishings resulted in the floor natural frequency reducing to 9.2 Hz. It is concluded that external facades have the net effect of adding stiffness the effect of internal partitions and furnishings is to add mass. In the context of finite element modelling of structures there is a significant challenge to represent these non-structural elements correctly so as to enable the generation of truly predictive FE models. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0711 Authors A. Devin, School of Architecture, Landscape and Civil Engineering, University College Dublin, Belfield, Dublin, Ireland P.J. Fanning, School of Architecture, Landscape and Civil Engineering, University College Dublin, Belfield, Dublin, Ireland Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Comfort, road holding and safety of passenger cars are mainly influenced by an appropriate design of suspension systems. Improvements of the dynamic behaviour can be achieved by implementing semi-active or active suspension systems. In these cases, the correct design of a well-performing suspension control strategy is of fundamental importance to obtain satisfying results. Operational Modal Analysis allows the experimental structural identification in those that are the real operating conditions: Moving from output-only data, leading to modal models linearised around the more interesting working points and, in the case of controlled systems, providing the needed information for the optimal design and verification of the controller performance. All these characters are needed for the experimental assessment of vehicle suspension systems. In the paper two suspension architectures are considered equipping the same car type. The former is a semi-active commercial system, the latter a novel prototypic active system. For the assessment of suspension performance, two different kinds of tests have been considered, proving ground tests on different road profiles and laboratory four poster rig tests. By OMA-processing the signals acquired in the different testing conditions and by comparing the results, it is shown how this tool can be effectively utilised to verify the operation and the performance of those systems, by only carrying out a simple, cost-effective road test. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0715 Authors L. Soria, Politecnico di Bari, Dipartimento di Ingegneria Meccanica e Gestionale, Bari, Italy B. Peeters, LMS International nv, Interleuvenlaan, Leuven, Belgium J. Anthonis, LMS International nv, Interleuvenlaan, Leuven, Belgium Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This paper presents an integrated approach to optimize for design and control of mechanical systems with random input parameters. Random parameters are represented by probability density functions. A numerical technique defining directly the representative values and the associated probabilities is implemented by modeling the stochastic parameters as generalized Wiener processes. The Monte Carlo¡¯s method is also implemented to deal with correlated parameters. A design and control sensitivity analysis optimization formulation is derived. A conceptual separation between time variant and time invariant design parameters is presented, this way including the design space into the control space and considering the design variables as control variables not depending on time. By using time integrals through all the derivations, the design and control problems are unified. In the optimization process we can use both types of variables simultaneously or by interdependent levels. The dynamic response is modeled via space and time finite elements, and is integrated either by at-once integration or step-by-step. The formulation is applied to a numerical example. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0708 Authors P.P. Moita, Escola Superior de Tecnologia, Setúbal, Portugal J.B. Cardoso, Departamento de Engenharia Mecânica, Instituto Superior Técnico, Lisboa, Portugal A. Barreiros, Departamento de Engenharia Mecânica, Instituto Superior Técnico, Lisboa, Portugal Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The vibration and damping characteristics of an assembled structure made of steel are investigated by an experimental modal analysis and compared with the results of a finite element modal analysis. A generic experiment is carried out to evaluate the stiffness and the damping properties of the structure's join patches. Using these results, an appropriate finite element model of the structure is developed where the join patches are represented by thin-layer elements containing material properties which are derived from the generic experiment's results. The joint's stiffness is modeled by orthotropic material behavior whereas the damping properties are represented by the model of constant hysteresis, leading to a complex-valued stiffness matrix. A comparison between the experimental and the numerical modal analysis shows good agreement. A more detailed damping model in conjunction with an optimization procedure for the joint's parameters results in an improved correlation between the experimental and the numerical modal quantities and reveals that the results of the generic experiment are sound. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0717 Authors A. Schmidt, Institut für Angewandte und Experimentelle Mechanik, Universtät Stuttgart, Stuttgart, Germany S. Bograd, Institut für Angewandte und Experimentelle Mechanik, Universtät Stuttgart, Stuttgart, Germany L. Gaul, Institut für Angewandte und Experimentelle Mechanik, Universtät Stuttgart, Stuttgart, Germany Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The integral model of dry friction components is built with assumption of classical Coulomb friction law and with specially developed model of normal stress distribution coupled with rolling resistance for elliptic contact shape. In order to avoid a necessity of numerical integration over the contact area at each the numerical simulation step, few versions of approximate model are developed and then tested numerically. In the numerical experiments the simulation results of the Celtic stone with the friction forces modelled by the use of approximants of different complexity (from no coupling between friction force and torque to the second order Padé approximation) are compared to results obtained from model with friction approximated in the form of piecewise polynomial functions based on the Taylor series with hertzian stress distribution. The coefficients of the corresponding approximate models are found by the use of optimization methods as in identification process using the real experiment data. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0716 Authors J. Awrejcewicz, Department of Automation and Biomechanics, The Technical University of Lodz, Lodz, Poland G. Kudra, Department of Automation and Biomechanics, The Technical University of Lodz, Lodz, Poland Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: It is well known that nonlinear systems, as well as linear time-varying systems, are characterized by non-stationary response signals. In this sense, they both show natural frequencies that are not constant over time; this variation has however different origins: for a time-varying system the mass, and possibly the stiffness distributions, are changing over time, while for a nonlinear system the natural frequencies are amplitude-dependent. An interesting case of time-varying system occurs when analyzing the transit of a train over a railway bridge, easily simulated by the crossing of a moving load over a beam. In this case, the presence of a nonlinearity in the beam behaviour can cause a significant alteration of the modal parameters extracted from the linearized model, such that the contributions of the two effects are no more distinguishable. For this study, some reinforced concrete beams have been tested in the framework of a vast project: these beams show a clear softening nonlinear behaviour, well detectable when the excitation is produced by a hammer (free response). If the passage of a carriage is considered, moreover, the variation of natural frequencies is always larger than expected because of this softening nonlinearity. The article first analyzes theoretically the two effects on the natural frequencies of a simply supported beam, then a numerical and an experimental tests are presented. The identification procedure is conducted with a linear algorithm called ST-SSI, which has been demonstrated to be appropriate for the analysis of non-stationary signals, in particular in presence of moving masses. The article shows that the nonlinear contribution can be well estimated by using this linear tool but, on the contrary, when also moving masses are present, it is difficult to separate the nonlinear effects from the time varying ones. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0704 Authors A. Bellino, Politecnico di Torino, Dipartimento di Meccanica, Corso Duca degli Abruzzi, Itlay S. Marchesiello, Politecnico di Torino, Dipartimento di Meccanica, Corso Duca degli Abruzzi, Itlay L. Garibaldi, Politecnico di Torino, Dipartimento di Meccanica, Corso Duca degli Abruzzi, Itlay Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The Attitude Control System (ACS) for Flexible Space Structures (FSS) like rigid-flexible satellite and solar sails demands great reliability, autonomy and robustness. The association of flexible motion and large angle maneuver imply that the FSS dynamics is only captured by complex non-linear mathematical model. As a result, FSS controller performance designed by linear control technique under the hypothesis of rigid dynamic can be degraded. Although vibrations can be suppressed rapidly, the flexibility effect can introduce a tracking error resulting in a minimum attitude acquisition time. On the other hand, faster manoeuvres can excite flexible modes in such a way to make the FSS lose the required pointing accuracy. In the present work, it is shown that a new multi-objective optimization algorithm, called M-GEOreal (Multi-objective Generalized Extremal Optimization with real codification), is a good tool to be used in such kind of problems. The M-GEOreal is a real coded version of the M-GEO evolutionary algorithm. Its performance on finding the gains of a non linear control law is evaluated through its application to the problem of controlling a large angle attitude manoeuvre of a rigid-flexible satellite.. The satellite non-linear model consists of a rigid central hub with a clamped free flexible beam. The multi-objective approach allows optimizing conflicting objective functions like time and energy. As a result, one can find a trade-off solution (non-dominated solutions). These solutions become available to the designer for posterior choice of an individual solution to be implemented. The non-dominated solutions are represented in the design space (Pareto set) and in the objective functions space (Pareto front). Having in mind the complexity of implementing a control algorithm in onboard satellite computer, this preliminary investigation has shown that the non-linear controller based on the M-GEOreal algorithm is a promising technique, since it has satisfied all the ACS requirements. A great advantage of the M-GEOreal procedure is its capacity to deal with non-linear system and designing non-linear controller with constant gains facilitating the on board computer implementation. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0702 Authors I. Mainenti-Lopes, National Institute for Space Research, Space Mechanics and Control Division, SP, Brasil L.C.G. Souza, National Institute for Space Research, Space Mechanics and Control Division, SP, Brasil F.L. De Sousa, National Institute for Space Research, Space Mechanics and Control Division, SP, Brasil Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The forces applied to a structure from the soil ground during an earthquake and the dynamic response of a structure are problems that are not well understood. In recent years, seismic design technology aided by numerical simulation is under active development. Successful improvement of the accuracy and reliability of numerically simulated results relies on a clear understanding of the seismic force transmission mechanism between the soil and a structure associated with mechanical properties of soil. In this study, laboratory shaking tests were conducted using the unique apparatus designed to have a structure move only by its inertial force and the lateral earth pressure that comes from surrounding sandy soils. The earth pressure at the structure surface and the relative displacement between the soil and the structure were measured in the experiments under various conditions. A new Finite Element interface model for sandy soil-structure dynamic interaction is proposed from the experimental results. Estimated seismic responses of a bridge pier calculated by the proposed interface model, conventional linear elastic model and tension cut-off model are compared. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0712 Authors N. Kodama, Waseda Institute for Advanced Study, Suginami, Tokyo, Japan K. Komiya, Chiba Institute of Technology, Narashino, Chiba, Japan Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Many structures or machines interact with some internal nonconservative forces and present asymmetric systems in which the stiffness and damping matrices are asymmetric. Examples include friction-induced vibration and aeroelastic flutter. Asymmetric systems are prone to flutter instability as a result of the real parts of some poles becoming positive when certain system parameters vary. This paper presents a receptance-based inverse method for assigning a number of complex poles of second-order damped asymmetric systems while keeping other unassigned poles unchanged. It uses state-feedback (active damping and active stiffness) to shift the poles to desired locations where all poles have negative real parts. Receptances at only a small, limited number of degrees-of-freedom of the underlying symmetric system are required. Simulated numerical examples indicate that this is an effective method and is capable of assigning negative real parts to unstable poles to stabilise an otherwise unstable second-order dynamic system. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0718 Authors M. Ghandchi Tehrani, Institute of Sound and Vibration Research, University of Southampton, Highfield, Southampton, UK H. Ouyang, School of Engineering, University of Liverpool, The Quadrangle, Liverpool, UK Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This paper presents a novel approach to the study of shock in elastic structures. An energy storage property for linear elastic non-dissipative structures is demonstrated, then extrapolated also to damped systems. This property relates locations of energy accumulation along the structure to the form of its stiffness and mass matrices. This result can be profitable used at a design stage of complex structures undergoing shock excitations. On the theoretical ground, the obtained results disclose indeed general properties of energy distribution in dynamical systems with implications on energy localization as well as on energy equipartitioning. Finally, these findings open a new point of view on energy transmission in structures, with potential application in the context of Statistical Energy Analysis. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0719 Authors A. Carcaterra, Department of Mechanics and Aeronautics, University of Rome, Rome, Italy N. Roveri, Department of Mechanics and Aeronautics, University of Rome, Rome, Italy Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: We investigate non-linear dynamics of flexible rectangular plates subjected to external shear harmonic load action. We show that an application of the classical and widely used Fourier analysis does not allow to obtain real picture of the frequency vibration characteristics in each time instant. On the other hand, we show that application of the wavelets approach allows to follow frequency time evolutions. Our numerical results indicate that vibrations in different plate points occur with the same frequencies set although their power is different. Hence, the vibration characteristics can be represented by one arbitrary taken plate point. Furthermore, using wavelets scenarios of transitions from regular to chaotic dynamics are illustrated and discussed including two novel scenarios not reported so far in the existing literature. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0705 Authors J. Awrejcewicz, TU Darmstadt LOEWE-Zentrum AdRIA, Darmstadt, Germany I.V. Papkova, Department of Mathematics and Modeling, The Saratov State Technical University, Saratov, Russia E.U. Krylova, Department of Mathematics and Modeling, The Saratov State Technical University, Saratov, Russia V.A. Krysko, Department of Mathematics and Modeling, The Saratov State Technical University, Saratov, Russia Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Buckling of load-carrying column structures is an important design constraint in light-weight structures as it may result in the collapse of an entire structure. When a column is loaded by an axial compressive load equal to its individual critical buckling load, a critically stable equilibrium occurs. When loaded above its critical buckling load, the passive column may buckle. If the actual loading during usage is not fully known, stability becomes highly uncertain. This paper presents an approach to control uncertainty in a slender flat column structure critical to buckling by actively stabilising the structure. The active stabilisation is based on controlling the first buckling mode by controlled counteracting lateral forces. This results in a bearable axial compressive load which can be theoretically almost three times higher than the actual critical buckling load of the considered system. Finally, the sensitivity of the presented system will be discussed for the design of an appropriate controller for stabilising the active column. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0700 Authors G.C. Enss, TU Darmstadt, System Reliability and Machine Acoustics SzM, Darmstadt, Germany R. Platz, Fraunhofer Institute for Structural Durability and System Reliability LBF, Darmstadt, Germany H. Hanselka, TU Darmstadt, System Reliability and Machine Acoustics SzM, Darmstadt, Germany Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: We describe a multi-component boundary element method for predicting wave energy distributions in a complex built-up system with material properties changing discontinuously at boundaries between sub-components. We point out that depending on the boundary conditions and the number of interfaces between sub-components, it may be advantageous to use a normal derivative method to set up the integral kernels. We describe how the resulting hypersingular integral kernels can be regularised. The method can be used to minimise the number of weakly singular integrals thus leading to BEM formulations which are easier to handle. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0703 Authors H.A.M. Ben Hamdin, School of Mathematical Sciences, University of Nottingham, Nottingham, UK G. Tanner, School of Mathematical Sciences, University of Nottingham, Nottingham, UK Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Design of Satellite Attitude Control System (ACS) that involves plant uncertainties and large angle manoeuvres following a stringent pointing control, may require new non-linear control techniques in order to have adequate stability, good performance and robustness. In that context, experimental validation of new non-linear control techniques through prototypes is the way to increase confidence in the controller designed. The Space Mechanics and Control Division (DMC) of INPE is constructing a 3-D simulator to supply the conditions for implementing and testing satellite ACS hardware and software. The 3-D simulator can accommodate various satellites components; like sensors, actuators, computers and its respective interface and electronic. Depending on the manoeuvre the 3-D simulator plant can be highly non-linear and if the simulator inertia parameters are not well determined the plant also can present some kind of uncertainty. As a result, controller designed by linear control technique can have its performance and robustness degraded, therefore controllers designed by new non-linear approach must be considered. This paper presents the application of the State-Dependent Riccati Equation (SDRE) method in conjunction with Kalman filter technique to design a controller for the DMC 3-D satellite simulator. The SDRE can be considered as the non-linear counterpart of Linear Quadratic Regulator (LQR) control technique. Initially, a simple comparison between the LQR and SDRE controller is performed. After that, practical applications are presented to address problems like presence of noise in process and measurements and incomplete state information. Kalman filter is considered as state observer to address these issues. The effects of the plant non-linearities and noises (uncertainties) are considered in the performance and robustness of the controller designed by the SDRE and Kalman filter. The 3-D simulator simulink-based model has been developed to perform the simulations examples to investigate the SDRE controller performance using the states estimated by the Kalman filter. Simulations have demonstrated the validity of the proposed approach, once the SDRE controller has presented good stability margin, great performance and robustness. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0701 Authors L.C.G. Souza, National Institute for Space Research- INPE, Brazilian Aeronautical Company-Embraer, SP, Brasil R.G. Gonzáles, National Institute for Space Research- INPE, Brazilian Aeronautical Company-Embraer, SP, Brasil Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: A highly efficient seismic protection of bridges have been demonstrated by the passive control systems with mechanical links with selective viscoelastic energy dissipation through viscous friction and dry friction. These systems are able to take over the deformations and movements caused by temperature variations, those due to seismic activities and from road traffic. A number of natural factors such as atmospheric and anthropogenic parameters, such as shock and vibration from road traffic, lead to the degradation of the viscoelastic bonds of passive control systems based on rubber molding. The presence of the elastic and dissipative nonlinear forces in the functioning of antiseismic systems inevitably leads to quantitative and qualitative changes of the structural responses of bridges and viaducts both in time and spectral domains. The implications of these changes on the integrity and stability of the bridge or viaduct sections may be from the simplest to the most severe depending on the type of seismic excitation to which they are subjected. For these reasons, it is imperative that we should identify and quantify the degree of nonlinearity of antiseismic systems embedded in the structure of bridges and viaducts in order to prevent accidents with severe socioeconomic implications. In this way can determine the dependence of the nonlinear behavior of the bearing system and the degree of degradation of their viscoelastic links. From a theoretical point of view the following parameters of the vibration of the system will be comparatively analyzed: the displacement and acceleration of the bridge deck in time and frequency domains, the hysteretic loop, the representation in the plane of phases, the power spectral density and the spectrograms of the acceleration signals. From an experimental point of view there will be identified and plotted the parameters able to provide information regarding the abnormal operation of the bearings from the elastomer: system acceleration, representations in time and frequency and its spectrogram. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0699 Authors A. Leopa, Research Center for Mechanics of the Machines, and Technological Equipments, "Dunarea de Jos" University of Galati, Faculty of Engineering, City???, Country??? S. Nastac, Research Center for Mechanics of the Machines, and Technological Equipments, "Dunarea de Jos" University of Galati, Faculty of Engineering, City???, Country??? C. Debeleac, Research Center for Mechanics of the Machines, and Technological Equipments, "Dunarea de Jos" University of Galati, Faculty of Engineering, City???, Country??? Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: In hydraulic hybrid vehicles (HHV), vibration in dual-mode pump/motor units should be isolated from the chassis. A mixed mode magnetorheological (MR) fluid mount was adopted to isolate this vibration and was evaluated in a quarter car model. The MR fluid mount was designed to be able to operate in flow mode and squeeze mode independently and simultaneously. For HHVs, it is desirable to control force and displacement transmissibility. These simulation results presented a basis for designing an effective algorithm to control both the displacement transmissibility and force transmissibility. Moreover, a hierarchical controller for minimizing the two requirements for transmissibility was also constructed. At last, a fuzzy logic controller was devised to closely reproduce the effect of the hierarchical controller. The experiments were set up to facilitate the hardware-in-the-loop evaluation of the mount. Results from the experiments showed that the mixed mode MR fluid mount was able to achieve desired dynamic stiffness profile to minimize the dual-transmissibility criterion. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0721 Authors Shuo Wang, Dynamic and Smart Systems Laboratory, The University of Toledo, Toledo, OH, USA Mohammad Elahinia, Dynamic and Smart Systems Laboratory, The University of Toledo, Toledo, OH, USA The Nguyen, MIE Department, University of Minnesota Duluth, Duluth, MN, USA Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Explicit finite element programme LS-DYNA was used to simulate a long-span steel reticulated shell under blast loading to investigate the structural dynamic responses in this paper. The elaborate finite element model of the Kiewitt-8 single-layer reticulated shell with span of 40 m subjected to central blast loading was established and all the process from the detonation of the explosive charge to the demolition, including the propagation of the blast wave and its interaction with structure was reproduced. The peak overpressure from the numerical analysis was compared with empirical formulas to verify the credibility and applicability of numerical simulation for blast loading. The dynamic responses of the structure under blast loading with different TNT equivalent weights of explosive and rise-span ratios were obtained. In addition, the response types of Kiewitt-8 single-layer reticulated shell subjected to central explosive blast loading were defined. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0722 Authors Ximei Zhai, School of Civil Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, China Yonghui Wang, Department of Civil and Environmental Engineering, National University of Singapore, Singapore Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The present work is focused on the study of damping mechanism in layered and welded cantilever beams with unequal thickness. It is observed that a number of vital parameters such as: thickness ratio, pressure distribution characteristics, relative slip and kinematic co-efficient of friction at the interfaces, initial amplitude of excitation, length and thickness of the beam specimen govern the damping capacity of these structures. Experiments have been conducted in order to study the effect of these parameters and validate the developed damping model. The damping model of the structure is found to be in fairly good agreement with the measured data. Finally, the results for the damping capacity are discussed and rationalized. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0720 Authors Bhagat Singh, Department of Mechanical Engineering, National Institute of Technology, Rourkela, Odisha, India Bijoy Kumar Nanda, Department of Mechanical Engineering, National Institute of Technology, Rourkela, Odisha, India Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Dynamic analysis of foundation plate-beam systems with transverse shear deformation is presented using modified Vlasov foundation model. Finite element formulation of the problem is derived by using an 8-node (PBQ8) finite element based on Mindlin plate theory for the plate and a 2-node Hughes element based on Timoshenko beam theory for the beam. Selective reduced integration technique is used to avoid shear locking problem for the evaluation of the stiffness matrices for both the elements. The effect of beam thickness, the aspect ratio of the plate and subsoil depth on the response of plate-beam-soil system is analyzed. Numerical examples show that the displacement, bending moments and shear forces are changed significantly by adding the beams. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0723 Authors Korhan Ozgan, Department of Civil Engineering, Faculty of Engineering, Karadeniz Technical University, Turkey. Tel.: +90 462 377 2662; Fax: +90 462 377 2606; E-mail: korhanozgan@yahoo.com Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: In this paper, a dynamic model for a magnetic planetary gear drive is proposed. Based on the model, the dynamic equations for the magnetic planetary gear drive are given. From the magnetic meshing forces and torques between the elements for the drive system, the tangent and radial magnetic meshing stiffness is obtained. Using these equations, the natural frequencies and the modes of the magnetic planetary gear drive are investigated. The sensitivity of the natural frequencies to the system parameters is discussed. Results show that the pole pair number and the air gap have obvious effects on the natural frequencies. For the planetary gear number larger than two, the vibrations of the drive system include the torsion mode of the center elements, the translation mode of the center elements, and the planet modes. For the planetary gear number equal to two, the planet mode does not occur, the crown mode and the sun gear mode occur. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0680 Authors Lizhong Xu, Mechanical Engineering Institute, Yanshan University, Hebei, China Xuejun Zhu, Mechanical Engineering Institute, Yanshan University, Hebei, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The purpose of this work is the experimental investigation and the mathematical modeling of the impact force behavior in a vibro-impact system, where an impact pendulum is mounted on a cart that moves with a prescribed displacement. The dynamics of the system will be evaluated considering different excitation frequencies and changing the impact gap. Experimental data are used to validate the mathematical model. The mathematical model allows a detailed nonlinear analysis, showing the rich response of the system, which includes dynamical jumps, bifurcations and chaos. In impact systems, discrepancies between numerical results and experimental measurements are common due to the difficulty in describing all factors that influence the resulting impact force profile. The use of wires to suspend the impacting body has the purpose to limit these uncertainties. Content Type Journal Article Pages - DOI 10.3233/SAV-2012-0678 Authors R.R. Aguiar, Department of Mechanical Engineering, Pontifical Catholic University of Rio de Janeiro, City? Brazil H.I. Weber, Department of Mechanical Engineering, Pontifical Catholic University of Rio de Janeiro, City? Brazil Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The current paper presents enhancement introduced to the elasto-viscoplastic shell formulation, which serves as a theoretical base for the finite element code EPSA (Elasto-Plastic Shell Analysis) [1–3]. The shell equations used in EPSA are modified to account for transverse shear deformation, which is important in the analysis of thick plates and shells, as well as composite laminates. Transverse shear forces calculated from transverse shear strains are introduced into a rate-dependent yield function, which is similar to Iliushin's yield surface expressed in terms of stress resultants and stress couples [12]. The hardening rule defined by Bieniek and Funaro [4], which allows for representation of the Bauschinger effect on a moment-curvature plane, was previously adopted in EPSA and is used here in the same form. Viscoplastic strain rates are calculated, taking into account the transverse shears. Only non-layered shells are considered in this work. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0644 Authors Pawel Woelke, Weidlinger Associates, Inc. 375 Hudson Street, New York, NY, USA Ka-Kin Chan, Weidlinger Associates, Inc. 375 Hudson Street, New York, NY, USA Raymond Daddazio, Weidlinger Associates, Inc. 375 Hudson Street, New York, NY, USA Najib Abboud, Weidlinger Associates, Inc. 375 Hudson Street, New York, NY, USA Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Design of mechanical systems often necessitates the use of dynamic simulations to calculate the displacements (and their derivatives) of the bodies in a system as a function of time in response to dynamic inputs. These types of simulations are especially prevalent in the shock and vibration community where simulations associated with models having complex inputs are routine. If the forcing functions as well as the parameters used in these simulations are subject to uncertainties, then these uncertainties will propagate through the models resulting in uncertainties in the outputs of interest. The uncertainty analysis procedure for these kinds of time-varying problems can be challenging, and in many instances, explicit data reduction equations (DRE's), i.e., analytical formulas, are not available because the outputs of interest are obtained from complex simulation software, e.g. FEA programs. Moreover, uncertainty propagation in systems modeled using nonlinear differential equations can prove to be difficult to analyze. However, if (1) the uncertainties propagate through the models in a linear manner, obeying the principle of superposition, then the complexity of the problem can be significantly simplified. If in addition, (2) the uncertainty in the model parameters do not change during the simulation and the manner in which the outputs of interest respond to small perturbations in the external input forces is not dependent on when the perturbations are applied, then the number of calculations required can be greatly reduced. Conditions (1) and (2) characterize a Linear Time Invariant (LTI) uncertainty model. This paper seeks to explain one possible approach to obtain the uncertainty results based on these assumptions. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0641 Authors J.B. Weathers, Shock, Noise, and Vibration Group, Northrop Grumman Shipbuilding, P.O. Box 149, Pascagoula, MS, USA Rogelio Luck, Department of Mechanical Engineering, Mississippi State University, 210 Carpenter Engineering Building, P.O. Box ME, Mississippi State, MS, USA Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The identification of the modal parameters of bridges and other large civil constructions has become an important research issue. Different approaches have been proposed depending on the excitation used: ambient excitations (due to wind, traffic, …) or artificial excitations (e.g. impact test with heavy drop weights). In practice it turns out that not all modes are well excited by the ambient forces. Hence the application of an artificial actuator is advisable. The problem is that larger constructions often require large and heavy excitation devices, which are hard to manipulate. Another difficulty encountered in performing a modal analysis on large civil constructions is the necessity for a large number of high sensitivity sensors. Consequently a large number of cables has to be installed resulting in a large setup time. This paper is a proof-of-concept which demonstrates the possibility of using lightweight Pneumatic Artificial Muscles combined with the scanning laser Doppler vibrometer to perform a modal analysis on a civil structure. This combination allows for an important reduction in setup time and allows for sine testing as well as the application of broadband signals such as periodic chirps, true noise or multisines. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0640 Authors K. Deckers, Acoustics and Vibration Research Group, Department of Mechanical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium P. Guillaume, Acoustics and Vibration Research Group, Department of Mechanical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium C. Vuye, Acoustics and Vibration Research Group, Department of Mechanical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium D. Lefeber, Acoustics and Vibration Research Group, Department of Mechanical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: In this paper the dynamic behavior of a viscoelastic beam subjected to a moving distributed load has been studied analytically. The viscoelastic properties of the beam have been considered as the linear standard model in shear and incompressible in bulk. The stress components have been separated to the shear and dilatation components then, the governing equation in viscoelastic form has been obtained with direct method and it has been solved with the eigenfunction expansion method. Using the obtained dimensionless coefficients from the governing equation, an analytical procedure has been presented and by parametric studies the effects of the load properties and viscoelastic materials on the amplitude and frequency of the response have been investigated. Such results can present an idea for selecting some parameters in engineering design. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0642 Authors Mohammad Tehrani, Mechanical Engineering Faculty, Shahrood University of Technology, P.O. Box 316, Shahrood, I.R. Iran H.R. Eipakchi, Mechanical Engineering Faculty, Shahrood University of Technology, P.O. Box 316, Shahrood, I.R. Iran Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The aim of this research is to create a mechanical and mathematical model of a multi-rod stabilizer for the sport archery bow and to analyze its capability to damp disagreeable recoil and vibration of the bow during internal ballistic motion. The research methods are based on the Euler-Bernoulli theory of beam bending, Lagrange equations of the second kind, the Cauchy problem, and the Runge-Kutta method. A mathematical software package was used to analyze the problem. The approach to the problem of sport-bow stabilization in the vertical plane that is proposed in this paper addresses the practical needs both of applied engineering mechanics and of the sport of archery. Numerical results from computer simulation are presented in both tabular and graphical form. The common motion of the string and arrow (internal ballistic motion) is accompanied by intense vibration which is caused by disruption of the static force balance at the moment of string release. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0626 Authors Igor Zaniewski, Casimir Pulaski Technical University, Radom, Poland Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This paper presents a comparison among classical elasticity, nonlocal elasticity, and modified couple stress theories for free vibration analysis of Timoshenko beams. A study of the influence of rotary inertia and nonlocal parameters on fundamental and higher natural frequencies is carried out. The nonlocal natural frequencies are found to be lower than the classical ones, while the natural frequencies estimated by the modified couple stress theory are higher. The modified couple stress theory results depend on the beam cross-sectional size while those of the nonlocal theory do not. Convergence of both non-classical theories to the classical theory is observed as the beam global dimension increases. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0627 Authors J.V. Araújo dos Santos, IDMEC/IST--Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal J.N. Reddy, Mechanical Engineering Department, Texas A&M University, 3123 TAMU, College Station, TX 77843-3123, USA Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Woven polymer-based composites are currently used in a wide range of marine applications. These materials often exhibit highly nonlinear, rate dependent, anisotropic behavior under shock loadings. Correlation to transient response data, beyond an initial peak, is often difficult. The state of damage evolves throughout the time history and the unloading response varies based on the amount, and nature of, the accumulated damage. Constitutive theories that address the loading and unloading responses have been developed and integrated with each other. A complete theory, applicable to transient dynamic analysis, is presented. The model is implemented within the commercial finite element code, Abaqus, in the form of a user material subroutine. In this study, the conical shock tube is used to experimentally reproduce the high strain rates and fluid structure interactions typical of underwater shock loadings. The conical shock tube data is used to validate analytical model predictions. Simulation results are in good agreement with test data. Content Type Journal Article Pages - DOI 10.3233/SAV-2010-0619 Authors David R. Hufner, General Dynamics Electric Boat, 75 Eastern Point Road, Groton, CT, USA Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The efficiency and accuracy of the elements proposed by the Finite Element Method (FEM) considerably depend on the interpolating functions, namely shape functions, used to formulate the displacement field within an element. In this paper, a new insight is proposed for derivation of elements from a mechanical point of view. Special functions namely Basic Displacement Functions (BDFs) are introduced which hold pure structural foundations. Following basic principles of structural mechanics, it is shown that exact shape functions for non-prismatic thin curved beams could be derived in terms of BDFs. Performing a limiting study, it is observed that the new curved beam element successfully becomes the straight Euler-Bernoulli beam element. Carrying out numerical examples, it is shown that the element provides exact static deformations. Finally efficiency of the method in free vibration analysis is verified through several examples. The results are in good agreement with those in the literature. Content Type Journal Article Pages - DOI 10.3233/SAV-2010-0623 Authors Ahmad Shahba, School of Civil Engineering, University College of Engineering, University of Tehran, P.O. Box: 11365-4563, Iran Reza Attarnejad, School of Civil Engineering, University College of Engineering, University of Tehran, P.O. Box: 11365-4563, Iran Mehran Eslaminia, Department of Civil, Construction and Environmental Engineering, North Carolina State University, Raleigh P.O. Box 27695-7908, USA Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: In this paper the free nonlinear vibration behavior of a cracked cantilever beam is investigated both theoretically and experimentally. For simplicity, the dynamic behavior of a cracked beam vibrating at its first mode is simulated using a simple single degree of freedom lumped parameter system. The time varying stiffness is modeled using a harmonic function. The governing equation of motion is solved by a perturbation method – the method of Multiple Scales. Results show that the correction term that is added to the main part of the response reflects the effect of breathing crack on the vibration response. Moreover, this part of response consists of the superharmonic components of the spectrum which is due to the systems intrinsic nonlinearity. Using this method an analytical relation is established between the system characteristics and the crack parameters in one hand and the nonlinear characteristics of system response on the other hand. Results have been validated by the experimental tests and a numerical method. Content Type Journal Article Pages - DOI 10.3233/SAV-2010-0622 Authors M. Rezaee, Mech. Eng. Dept, Faculty of Mech. Eng., University of Tabriz, Iran H. Fekrmandi, Mech. Eng. Dept, Faculty of Mech. Eng., University of Tabriz, Iran Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The free vibration analysis of one-layered and two-layered metallic cylindrical shell panels is evaluated in this work. The free frequency values are investigated for both thermo-mechanical and pure mechanical problems. Thermo-mechanical frequencies are calculated by means of a fully coupled thermo-mechanical model where both the displacement and temperature are primary variables in the considered governing equations. Pure mechanical frequencies are obtained from a mechanical model where the effect of the temperature field is not included in the stiffness matrix and the displacement is the only primary variable of the problem. The inclusion of the thermal part in the stiffness matrix gives larger frequencies. Both thermo-mechanical and pure mechanical models are developed in the framework of Carrera's Unified Formulation (CUF) in order to obtain several variable kinematic models. Both equivalent single layer and layer wise approaches are considered for multilayered shells. The use of refined two-dimensional theories for shells permits the evaluation of the effects of the thermo-mechanical coupling for lower and higher order modes, higher frequency values, multilayered configurations, thick and thin shells and several values of the radius of curvature of the shell geometry. It has mainly been concluded that the thermo-mechanical coupling is not influenced by the curvature of the shells, therefore, the main conclusions already given for the plate geometry are here confirmed: – the thermo-mechanical coupling is correctly determined if both the thermal and mechanical parts are correctly approximated; – it is small for each investigated case; – it influences the various vibration modes in different ways; – it has a limited dependence on the considered case, but this dependence vanishes if a global coupling is considered. Content Type Journal Article Pages - DOI 10.3233/SAV-2010-0621 Authors S. Brischetto, Department of Aeronautics and Space Engineering, Politecnico di Torino, Italy E. Carrera, Department of Aeronautics and Space Engineering, Politecnico di Torino, Italy Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This paper investigates the influence of the wheel vertical dynamics in the mechanism of squeal noise on a scaled test bench. To this purpose, sustained oscillations are first studied on a single degree of freedom oscillator, considering both a decreasing slope of the friction curve and a vertical excitation. Their relative importance to sustain the oscillations is discussed. Then, a mathematical model of a quarter scale test bench is developed in the frequency domain. Using this model, it is shown that the squeal noise resulting from the excitation of the bending modes of the wheel is sustained because these bending modes are associated with variations of the vertical contact force. Results are further confirmed by experiments conducted on a scaled test bench. Content Type Journal Article Pages - DOI 10.3233/SAV-2010-0620 Authors C. Collette, University of Brussels, Department of Mechanical Engineering and Robotics. 50 av. F.D. Roosevlet, 1050 Brussels, Belgium Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The frequency-response curve is an important information for the structural design, but the conventional time-history method for obtaining the frequency-response curve of a multi-degree-of-freedom (MDOF) system is time-consuming. Thus, this paper presents an efficient technique to determine the forced vibration response amplitudes of a multi-span beam carrying arbitrary concentrated elements. To this end, the "steady" response amplitudes | Y(x)| _s of the above-mentioned MDOF system due to harmonic excitations (with the specified frequencies ω _e) are determined by using the numerical assembly method (NAM). Next, the corresponding "total" response amplitudes | Y(x)| _t of the same vibrating system are calculated by using a relationship between | Y(x)| _t and | Y(x)| _s obtained from the single-degree-of-freedom (SDOF) vibrating system. It is noted that, near resonance (i.e., &omega_e/ω≈ 1.0), the entire MDOF system (with natural frequency ω) will vibrate synchronously in a certain mode and can be modeled by a SDOF system. Finally, the conventional finite element method (FEM) incorporated with the Newmark's direct integration method is also used to determine the "total" response amplitudes | Y(x)| _t of the same forced vibrating system from the time histories of dynamic responses at each specified exciting frequency ω _e . It has been found that the numerical results of the presented approach are in good agreement with those of FEM, this confirms the reliability of the presented theory. Because the CPU time required by the presented approach is less than 1% of that required by the conventional FEM, the presented approach should be an efficient technique for the title problem. Content Type Journal Article Pages - DOI 10.3233/SAV-2010-0616 Authors J.S. Wu, Department of Systems and Naval Mechatronic Engineering, National Cheng-Kung University, Tainan, 70101 Taiwan J.H. Chen, Department of Systems and Naval Mechatronic Engineering, National Cheng-Kung University, Tainan, 70101 Taiwan Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: This paper presents the transverse vibration of Bernoulli-Euler homogeneous isotropic damped beams with general boundary conditions. The beams are assumed to be subjected to a load moving at a uniform velocity. The damping characteristics of the beams are described in terms of fractional derivatives of arbitrary orders. In the analysis where initial conditions are assumed to be homogeneous, the Laplace transform cooperates with the decomposition method to obtain the analytical solution of the investigated problems. Subsequently, curves are plotted to show the dynamic response of different beams under different sets of parameters including different orders of fractional derivatives. The curves reveal that the dynamic response increases as the order of fractional derivative increases. Furthermore, as the order of the fractional derivative increases the peak of the dynamic deflection shifts to the right, this yields that the smaller the order of the fractional derivative, the more oscillations the beam suffers. The results obtained in this paper closely match the results of papers in the literature review. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0634 Authors R. Abu-Mallouh, Applied Sciences University, Amman 11931, Jordan I. Abu-Alshaikh, Applied Sciences University, Amman 11931, Jordan H.S. Zibdeh, Jordan University of Science and Technology, Irbid, Jordan Khaled Ramadan, Applied Sciences University, Amman 11931, Jordan Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: In this paper we study the periodic solutions of free vibration of mechanical systems with third and fifth-order nonlinearity for two examples using He's Frequency-Amplitude Formulation (HFAF).The effectiveness and convenience of the method is illustrated in these examples. It will be shown that the solutions obtained with current method have a fabulous conformity with those achieved from time marching solution. HFAF is easy with powerful concepts and the high accuracy, so it can be found widely applicable in vibrations, especially strong nonlinearity oscillatory problems. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0633 Authors A. Fereidoon, Department of Mechanical Engineering, Faculty of Engineering, Semnan University, Iran M. Ghadimi, Department of Mechanical Engineering, Babol University of Technology, Babol, Iran A. Barari, Department of Civil Engineering, Aalborg University, Sohngårdsholmsvej 57, 9000 Aalborg, Aalborg, Denmark H.D. Kaliji, Department of Mechanical Engineering, Islamic Azad University, Semnan Branch, Semnan, Iran G. Domairry, Department of Mechanical Engineering, Babol University of Technology, Babol, Iran Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: Inerters have become a hot topic in recent years especially in vehicle, train, building suspension systems, etc. Eight different layouts of suspensions were analyzed with a quarter-car model in this paper. Dimensionless root mean square (RMS) responses of the sprung mass vertical acceleration, the suspension travel, and the tire deflection are derived which were used to evaluate the performance of the quarter-car model. The behaviour of semi-active suspensions with inerters using Groundhook, Skyhook, and Hybrid control has been evaluated and compared to the performance of passive suspensions with inerters. Sensitivity analysis was applied to the development of a high performance semi-active suspension with an inerter. Numerical simulations indicate that a semi-active suspension with an inerter has much better performance than the passive suspension with an inerter, especially with the Hybrid control method, which has the best compromise between comfort and road holding quality. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0628 Authors Xin-Jie Zhang, State Key Laboratory of Automobile Dynamics Simulation, Jilin University, Changchun, China Mehdi Ahmadian, Center for Vehicle Systems and Safety, Virginia Tech, Blacksburg, VA, USA Kong-Hui Guo, State Key Laboratory of Automobile Dynamics Simulation, Jilin University, Changchun, China Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: In this paper, an approach using observability and controllability grammian matrices is proposed to determine if structural damage has occurred together with an estimate of its location. The theory is outlined and simulations are carried out on a simple structure to demonstrate the method. Experimental tests were also carried out to demonstrate the validity of the approach using real signals. The dynamic properties of the structure are identified using the eigensystem realization algorithm (ERA) and a reduced order state-space model of the system subsequently constructed. Either the observability or controllability grammians can then be used depending on the number of sensors available. It is shown that these are sensitive to both the degree and location of the damage and offer promise for structural health monitoring applications. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0631 Authors D.D. Bueno, Department of Mechanical Engineering, UNESP – São Paulo State University, Av. Brasil, N° 56, Centro, Ilha Solteira, SP, Brazil, Zip Code 15385000 C.R. Marqui, Department of Mechanical Engineering, UNESP – São Paulo State University, Av. Brasil, N° 56, Centro, Ilha Solteira, SP, Brazil, Zip Code 15385000 V. Lopes Jr., Department of Mechanical Engineering, UNESP – São Paulo State University, Av. Brasil, N° 56, Centro, Ilha Solteira, SP, Brazil, Zip Code 15385000 M.J. Brennan, Department of Mechanical Engineering, UNESP – São Paulo State University, Av. Brasil, N° 56, Centro, Ilha Solteira, SP, Brazil, Zip Code 15385000 Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622

Description: The free transverse vibrations of thin nonhomogeneous rectangular plates of variable thickness have been studied using boundary characteristic orthogonal polynomials in the Rayleigh-Ritz method. Gram-Schmidt process has been used to generate these orthogonal polynomials in two variables. The thickness variation is bidirectional and is the cartesian product of linear variations along two concurrent edges of the plate. The nonhomogeneity of the plate is assumed to arise due to linear variations in Young's modulus and density of the plate material with the in-plane coordinates. Numerical results have been computed for four different combinations of clamped, simply supported and free edges. Effect of the nonhomogeneity and thickness variation with varying values of aspect ratio on the natural frequencies of vibration is illustrated for the first three modes of vibration. Three dimensional mode shapes for all the four boundary conditions have been presented. A comparison of results with those available in the literature has been made. Content Type Journal Article Pages - DOI 10.3233/SAV-2011-0635 Authors R. Lal, Department of Mathematics, Indian Institute of Technology Roorkee, Roorkee – 247 667, India Yajuvindra Kumar, Department of Mathematics, Indian Institute of Technology Roorkee, Roorkee – 247 667, India Journal Shock and Vibration Online ISSN 1875-9203 Print ISSN 1070-9622