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  • Articles  (471)
  • 2010-2014  (471)
  • 1990-1994
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  • 1950-1954
  • 2013  (471)
  • PAMM - Proceedings in Applied Mathematics and Mechanics  (135)
  • Microgravity Science and Technology  (39)
  • Microgravity Science and Technology. 2013; 25(1): 83-94. Published 2013 Feb 01. doi: 10.1007/s12217-012-9337-2.  (1)
  • Microgravity Science and Technology. 2013; 25(2): 121-126. Published 2013 Jan 08. doi: 10.1007/s12217-012-9336-3.  (1)
  • Microgravity Science and Technology. 2013; 25(2): 127-139. Published 2013 Feb 06. doi: 10.1007/s12217-013-9338-9.  (1)
  • Microgravity Science and Technology. 2013; 25(3): 141-151. Published 2013 May 15. doi: 10.1007/s12217-013-9339-8.  (1)
  • Microgravity Science and Technology. 2013; 25(3): 153-159. Published 2013 Jun 02. doi: 10.1007/s12217-013-9341-1.  (1)
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  • 1
    Publication Date: 2013-09-17
    Description: It is a difficult job to gauge the liquid fuel mass in a tank on spacecrafts under microgravity condition. Without the presence of strong buoyancy, the configuration of the liquid and gas in the tank is uncertain and more than one bubble may exist in the liquid part. All these will affect the measure accuracy of liquid mass gauge, especially for a method called Compression Mass Gauge (CMG). Four resonance resources affect the choice of compression frequency for CMG method. There are the structure resonance, liquid sloshing, transducer resonance and bubble resonance. Ground experimental apparatus are designed and built to validate the gauging method and the influence of different compression frequencies at different fill levels on the measurement accuracy. Harmonic phenomenon should be considered during filter design when processing test data. Results demonstrate the ground experiment system performances well with high accuracy and the measurement accuracy increases as the compression frequency climbs in low fill levels. But low compression frequencies should be the better choice for high fill levels. Liquid sloshing induces the measurement accuracy to degrade when the surface is excited to wave by external disturbance at the liquid natural frequency. The measurement accuracy is still acceptable at small amplitude vibration.
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  • 2
    Publication Date: 2013-09-21
    Description: Linear stability of plane-parallel pulsational flow of two miscible fluids in a horizontal layer subjected to high frequency horizontal vibrations is investigated neglecting viscosity and diffusion. Long-wave instability is studied analytically and instability to the perturbations with finite wavelength—numerically.
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  • 3
    Publication Date: 2013-09-28
    Description: The computational and experimental studies have been performed to investigate the hydrodynamic process of liquid propellant reorientation for the launch vehicle series fuel tanks in microgravity environment. The VOF method was used to simulate the free surface flow of gas-liquid. The process of the liquid propellant reorientation started from initially curved interface at low Bond number. The propellant reorientation flow procedure at high Bond number was obtained from numerical simulation and scale model experiment in drop tower. The numerical results agreed well with the experiments. The results can be used to adjust the engineering reorientation parameters.
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  • 4
    Publication Date: 2013-09-30
    Description: Recent measurements of the temperature profiles across the liquid-vapor interface of a steady evaporating liquid were performed in a thin planar liquid layer subjected to externally imposed horizontal temperature differences when the interface was open to air. Temperature discontinuities have been found to exist at the interface with an growing tendency as the imposed horizontal temperature difference increasing. Under the co-influence of thermocapillary convection and evaporation effect, a thin layer of 0.5 mm thick with approximate uniform temperature was found just below the liquid-vapor interface. Repeated experiments and further comparisons of the interfacial temperature profiles for different spatial positions along the streamwise center line and varying depths of the liquid layer were also carried out. And the temperature discontinuity was found related to the temperature in liquid phase, which was strongly influenced by the coupling of thermocapillary convection and evaporation effect.
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  • 5
    Publication Date: 2013-04-10
    Description: The ability of a micro-groove to prevent the spreading of HFE-7100 fluid (C 4 F 9 OCH 3 ) having low surface tension (γ = 13.6 mN/m) on a surface is studied. In this study, micro-grooves were made around square openings of a plate made of either polycarbonate or 316 stainless steel. To verify effectiveness of micro-grooves to stop the spread of HFE-7100, experiments were done under non-saturated and saturated conditions. Under non-saturated conditions the micro-grooves on both materials confined the liquid up to apparent angle of 55 ± 5° due to the edge effect. Saturated gas-vapor mixture with vapor mass fraction of w v = 88% and w v = 97% did not significantly influence the confinement of the liquid by the micro-groove. This result is promising for application of micro-grooved plates in CIMEX experiment planned for ISS.
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  • 6
    Publication Date: 2013-04-10
    Description: There exists an instrument SODI (Selected Optical Diagnostic Instrument) on the ISS where series of the DCMIX (Diffusion Coefficients in Mixtures) experiments are conducted by members of the ESA Topical Team. The study is addressed to the performance of thermal design of SODI instrument for DCMIX configuration. We report the results on the temperature fields which were measured interferometrically both in two ground setups (one thermally optimized; the other one, the engineering model of the ISS SODI-DCMIX experiment: non optimized) and in the ISS experiment itself with the respective numerical simulations. Even though monitoring of the cell with binary mixture $THN-nC_{12}$ employs only an interferometer with one wave length instead of two for other cells with ternary mixtures, it gives valuable information about the instrument performance. Temperature and concentration fields observed during the tests in the engineering model are compared with those obtained in laboratory experiments with the same liquid, with numerical simulations and with first results from the ISS in Run #16. The thermal design of the microgravity cell, being not optimized for ground experiments, exhibits a promising performance in the weightlessness condition.
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  • 7
    Publication Date: 2013-04-10
    Description: Motility and aging in Drosophila have proven to be highly modified under altered gravity conditions (both in space and ground simulation facilities). In order to find out how closely connected they are, five strains with altered geotactic response or survival rates were selected and exposed to an altered gravity environment of 2 g . By analysing the different motile and behavioural patterns and the median survival rates, we show that altered gravity leads to changes in motility, which will have a negative impact on the flies’ survival. Previous results show a differential gene expression between sessile samples and adults and confirm that environmentally-conditioned behavioural patterns constrain flies’ gene expression and life span. Therefore, hypergravity is considered an environmental stress factor and strains that do not respond to this new environment experience an increment in motility, which is the major cause for the observed increased mortality also under microgravity conditions. The neutral-geotaxis selected strain (strain M) showed the most severe phenotype, unable to respond to variations in the gravitational field. Alternatively, the opposite phenotype was observed in positive-geotaxis and long-life selected flies (strains B and L, respectively), suggesting that these populations are less sensitive to alterations in the gravitational load. We conclude that the behavioural response has a greater contribution to aging than the modified energy consumption in altered gravity environments.
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  • 8
    Publication Date: 2013-04-10
    Description: Previous studies indicated that human Adipose Tissue-derived Mesenchymal Stem Cells (AT-MSCs) cultured in simulated microgravity (sim-μg) in standard laboratory incubators alter their proliferation and differentiation. Recent studies on the stem cell (SC) niches and the influence of oxygen on SC proliferation, senescence, and differentiation point to oxygen level as one of the key regulators of SC fate. Here we present the results of a study that focussed at the evaluation of the influence of oxygen level in the cultivation of AT-MSCs in sim-μg. In detail, cells were cultured for 14 days in sim-μg using the Random Positioning Machine (RPM) and two different oxygen concentrations: 5 % and 20 %. The results were compared with those obtained at 1g in the same conditions. Affymetrix Human Gene 1.0 ST array and Gene Ontology (GO) analysis were performed. The results confirmed that in all of the sim-μg experiments oxygen concentration modulates cell signalling and adhesion, in line with the knowledge that sim-μg affects cell shape and cytoskeletal organization.
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  • 9
    Publication Date: 2013-04-10
    Description: Experiments with gas shear-driven rivulet flows in a minichannel of height 1.4 mm and of width 30 mm were conducted during several parabolic flights campaigns organized by the European Space Agency (ESA). Rivulet flow is defined as a particular case of liquid film flow when the film occupies only a part of the substrate without touching to the lateral walls of the channel. A high frequency schlieren technique has been used for visualization of the two-phase flows. It is shown that surface tension becomes the dominating force with decreasing of the gravity level, which results in reducing of the rivulet width. The width increases with the gravity level and with the liquid flow rate growth and reduces with the gas flow rate growth.
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  • 10
    Publication Date: 2013-04-10
    Description: The objective of this study was to explore the potential interaction between gravity and growth hormones on isoflavonoid accumulation. Soybean callus ( Glycine max (L.) Merr. cv. ‘Acme’) was grown in the dark for 16 days at 22 °C in a growth medium supplemented with four different combinations of phytohormones and subjected to 4- g and 8- g forces simulated in a centrifuge and 1- g in an adjacent stationary control. Isoflavonoid aglycones and their glycoside concentrations (daidzein, genistein, daidzin, 6″-O-malonyl-7-O-glucosyl daidzein, genistin, 6″-O-malonyl-7-O-glucosyl genistein) were determined in the resulting tissues. Although gravity had no significant impact on callus growth, increasing gravity reduced isoflavonoid accumulation in three out of the four phytohormone-supplemented culture media. The ratio of the auxin naphthalene acetic acid (NAA) to the cytokinin benzylaminopurine (BAP) was found to have profound effect on both callus growth and isoflavonoid accumulation. The cytokinin BAP promoted callus tissue growth, but reduced callus isoflavonoid suggesting the isoflavonoid accumulation was not keeping pace with the cell growth in the elevated concentration of BAP. On the other hand, NAA had little or no effect on callus growth, but greatly enhanced isoflavonoid accumulation. Interactive effects of gravity and hormone on isoflavonoid accumulation were evident and its implication to the mechanism by which gravity exerts the effect on plant secondary metabolites is discussed.
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  • 11
    Publication Date: 2013-04-10
    Description: Microgravity-induced muscle atrophy is a problem of utmost importance for the impact it may have on the health and performance of astronauts. Therefore, appropriate countermeasures are needed to prevent disuse atrophy and favour muscle recovery. Muscle atrophy is characterized by loss of muscle mass and strength, and a shift in substrate utilization from fat to glucose, that leads to a reduced metabolic efficiency and enhanced fatigability. Laser therapy is already used in physical medicine and rehabilitation to accelerate muscle recovery and in sports medicine to prevent damages produced by metabolic disturbances and inflammatory reactions after heavy exercise. The aim of the research we present was to get insights on possible benefits deriving from the application of an advanced infrared laser system to counteract deficits of muscle energy metabolism and stimulate the recovery of the hypotrophic tissue. The source used was a Multiwave Locked System (MLS) laser, which combines continuous and pulsed emissions at 808 nm and 905 nm, respectively. We studied the effect of MLS treatment on morphology and energy metabolism of C2C12 cells, a widely accepted myoblast model, previously exposed to microgravity conditions modelled by a Random Positioning Machine. The MLS laser treatment was able to restore basal levels of serine/threonine protein phosphatase activity and to counteract cytoskeletal alterations and increase in glycolytic enzymes activity that occurred following the exposure to modelled microgravity. In conclusion, the results provide interesting insights for the application of infrared laser in the treatment of muscle atrophy.
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  • 12
    Publication Date: 2013-04-10
    Description: The long-duration fluid physics experiments on a thermocapillary-driven flow have been carried out on the Japanese Experiment Module ‘Kibo’ aboard the International Space Station (ISS) since 2008. In these experiments, various aspects of thermocapillary convection in a half-zone (HZ) liquid bridge of high Prandtl number fluid have been examined under the advantages of the long-duration high-quality microgravity environment. In 2010, the authors succeeded to realize nonlinear convective fields in the HZ liquid bridge of rather high aspect ratio. Special attention was paid on to the complex convective fields, especially on the behaviors of the hydrothermal wave (HTW) over the free surface visualized by an infrared camera. In order to evaluate the characteristics of the nonlinear convective behaviors and their transition processes, the authors indicate the images taken by the infrared camera describing the time evolution of HTW, the spatio-temporal diagram, the Fourier analysis, and the pseudo-phase space, reconstructed from the time series of the scalar information of the liquid bridge, that is, surface temperature variation. In this paper, the authors introduce the signature of complex HTW behaviors observed at the long-duration on-orbit experiments, and make comparisons with some previous terrestrial and microgravity experiments.
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  • 13
    Publication Date: 2013-04-10
    Description: The paper deals with the investigation of a behavior of a system of particles suspended in a fluid in a container subjected to high frequency translational vibrations of linear polarization. Pair interaction forces act on the particles under these conditions. These forces decrease with the distance and depend on the interacting particles orientation with respect to the vibration direction. The presence of these forces leads to the formation of structures in space. The problem is solved numerically using molecular dynamics method with pair interaction approximation. It is shown that the process of the structures formation consists of the fast stage of compact cluster formation and slow evolution of these clusters. It is found that for vibrations of linear polarization the particles form the chains oriented perpendicular to the direction of vibrations. At long time-scales these chains form the layers perpendicular to the direction of the vibrations and located almost periodically all over the fluid volume.
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  • 14
    Publication Date: 2013-04-10
    Description: Boiling in porous media is an active topic of research since it is associated with various applications, e.g. microelectronics cooling, wetted porous media as thermal barriers, food frying. Theoretical expressions customary scale boiling heat and mass transfer rates with the value of gravitational acceleration. Information obtained at low gravity conditions show a deviation from the above scaling law but refers exclusively to non-porous substrates. In addition, the role of buoyancy in boiling at varying gravitational levels (i.e. from microgravity—important to satellites and future Lunar and Martial missions, to high-g body forces—associated with fast aerial maneuvers) is still unknown since most experiments were conducted over a limited range of g-value. The present work aims at providing evidence regarding boiling in porous media over a broad range of hypergravity values. For this, a special device has been constructed for studying boiling inside porous media in the Large Diameter Centrifuge (LDC at ESA/ESTEC). LDC offers the unique opportunity to cancel the shear stresses and study only the effect of increased normal forces on boiling in porous media. The device permits measurement of the temperature field beneath the surface of the porous material and video recordings of bubble activity over the free surface of the porous material. The preliminary results presented from experiments conducted at terrestrial and hypergravity conditions, reveal for the first time the influence of increased levels of gravity on boiling in porous media.
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  • 15
    Publication Date: 2013-04-10
    Description: In this paper we report about the BIOKIS payload: a multidisciplinary set of experiments and measurements in the fields of Biology (4) and Dosimetry (3) performed in microgravity. BIOKIS took advantage of the last STS-134 Endeavour mission and engineering state of the art in Space Life Science. The BIOKIS payload is compact, efficient, and capable to host experiments with different samples and science disciplines. Moreover, the time overlap of biological experiments and dosimetry measurements will produce more insightful information.
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  • 16
    Publication Date: 2013-04-10
    Description: Aircraft parabolic flights provide repetitively short periods of reduced gravity and are used to conduct scientific and technology microgravity investigations, to test instrumentation prior to space flights and to train astronauts before a space mission. Since 1997, ESA, CNES and DLR use the Airbus A300 ZERO-G, currently the largest airplane in the world for this type of experimental research flight. This mean is managed by the French company Novespace. Since 2010, Novespace offers the possibility of flying reduced gravity levels equivalent to those on the Moon and Mars achieved repetitively for periods of more than 20 s. ESA, CNES and DLR issued an international call for experiments inviting European Scientists to submit experiment proposals to be conducted at these partial gravity levels. The scientific objectives are on one hand to obtain results at intermediate levels of gravity (between 0 and 1 g) allowing a better study of the influence of gravity, and on the other hand to give them some elements to prepare for research and exploration during space flights and future planetary exploration missions. ESA, CNES and DLR jointly organised in June 2011 the first Joint European Partial-G Parabolic Flight campaign with 13 experiments selected among 42 received proposals. Parabolas were flown during three flights providing micro-, Moon and Mars gravity levels with duration typically of 20 s, 25 s and 32 s with a mixed complement of investigations in physical and life sciences and in technology. The paper presents the approach taken to organise this campaign and the 13 selected experiments with some preliminary results are presented to show the interest of this unique research tool for microgravity and partial gravity investigations.
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  • 17
    Publication Date: 2013-04-10
    Description: Planarians of the species Schmidtea mediterranea are a well-established model for regeneration studies. In this paper, we first recall the morphological characters and the molecular mechanisms involved in the regeneration process, especially focussing on the Wnt pathway and the establishment of the antero-posterior axial polarity. Then, after an assessment of a space-experiment (run in 2006 on the Russian Segment of the International Space Station) on planarians of the species Girardia tigrina , we present our experimental program to ascertain the effects that altered-gravity conditions may have on regeneration processes in S. mediterrnea at the molecular and genetic level.
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  • 18
    Publication Date: 2013-04-10
    Description: Numerical modeling of thermodiffusion experiment for a binary mixture of water and isopropanol under micro-vibrations condition is presented. The vibrations obtained onboard ISS and FOTON-M3 are due to different activities. The effect of micro-gravity vibration level on the variation of mixture properties were investigated in detail. In this paper, the thermodiffusion experiment was investigated for two different g-jitter vibrations in the presence of a thermal gradient. The cavity is filled with a binary mixture of water and isopropanol with negative Soret. All physical properties including density, mass diffusion and thermodiffusion coefficients were assumed as functions of temperature and concentration. In order to understand the behavior of the mixture during the course of the experiment, five locations in the domain were chosen. It was found that a similarity between g-jitter vibration and induced velocity pattern exist. Micro vibration was found to have a minimal effect on the molecular and thermodiffusion coefficients.
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  • 19
    Publication Date: 2013-04-10
    Description: Seedlings of Arabidopsis thaliana -ABD2-GFP were grown under slow clinorotation (2 rpm) and treated with actin and tubulin disrupting drugs in order to characterize the role of actin microfilaments in cell growth and gravisensing. Changes in microfilament organization and cell parameters have shown that the transition root zone (TZ) is rather sensitive to microfilament disruption in control plants. It is assumed that under clinorotation, organization of actin cytoskeleton in the TZ is coordinated in a different way than in the control. Organization of microfilaments depends upon organization of microtubules and clinorotation does not influence this interrelation significantly.
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  • 20
    Publication Date: 2013-04-10
    Description: The need for an in-orbit 1×g control originated from the fact that Space radiation or other environmental factors of Space flight could not be excluded as cause for the effects on biological systems that were mainly interpreted as effects of the weightlessness environment. Indeed, in many experiments the 1×g reference centrifuge on board revealed the same data as the 1×g controls on ground, proving the lack of gravity was causing the results. In other cases, the reference centrifuge data were intermediate or clearly different to the ground data which was either due to interrupted 1×g conditions on board or to other, sometimes not well understood factors. This triggered also the development of sophisticated hardware allowing the start, i.e. the transition from 1×g to 0×g, or the termination of the experiment without stopping the centrifuge. Recently developed facilities provide also a complete life support system on the centrifuge rotor. Besides the in-flight 1×g control, acceleration experiments required a centrifuge for determination of threshold values in orbit.
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  • 21
    Publication Date: 2013-04-10
    Description: Seeds of Arabidopsis thaliana were exposed to hypergravity environments (2 g and 6 g ) and germinated during centrifugation. Seedlings grew for 2 and 4 days before fixation. In all cases, comparisons were performed against an internal (subjected to rotational vibrations and other factors of the machine) and an external control at 1 g . On seedlings grown in hypergravity the total length and the root length were measured. The cortical root meristematic cells were analyzed to investigate the alterations in cell proliferation, which were quantified by counting the number of cells per millimeter in the specific cell files, and cell growth, which were appraised through the rate of ribosome biogenesis, assessed by morphological and morphometrical parameters of the nucleolus. The expression of cyclin B1, a key regulator of entry in mitosis, was assessed by the use of a CYCB1:GUS genetic construction. The results showed significant differences in some of these parameters when comparing the 1 g internal rotational control with the 1 g external control, indicating that the machine by itself was a source of alterations. When the effect of hypergravity was isolated from other environmental factors, by comparing the experimental conditions with the rotational control, cell proliferation appeared depleted, cell growth was increased and there was an enhanced expression of cyclin B1. The functional meaning of these effects is that cell proliferation and cell growth, which are strictly associated functions under normal 1 g ground conditions, are uncoupled under hypergravity. This uncoupling was also described by us in previous experiments as an effect of microgravity, but in an opposite way. Furthermore, root meristems appear thicker in hypergravity-treated than in control samples, which can be related to changes in the cell wall induced by altered gravity.
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  • 22
    Publication Date: 2013-04-10
    Description: In addition to the presence of specific gravity receptors in living organisms, biological membranes were found to directly respond to gravity changes. Among others, changes in membrane permeability and as a consequence in membrane potential and intracellular ion concentrations have been demonstrated mainly by using electrophysiological techniques. However, the acquired amount of data up to now is low due to technical limitations of electrophysiology in microgravity platforms. Optical techniques will be able to deliver much higher amounts of data here, especially in case high throughput techniques based on 96 well plate (or higher numbers of wells) readers can be used. In this manuscript we present a new set-up for parabolic flight campaigns based on a multi-purpose plate reader for photometric, luminescent and fluorometric measurements. In a first series of experiments during a parabolic flight campaign the system was verified for membrane potential and intracellular calcium concentration measurements of neuronal cells using fluorescent dyes.
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  • 23
    Publication Date: 2013-02-09
    Description: Common structural optimisation problems consist of problem-specific objective functions which have to be minimised mathematically with respect to design and state variables taking into account particular constraints. In contrast to this, we adopt a conceptually different approach for the design of a structure which is not based on a topology-optimisation technique. Instead, we apply a one-dimensional energy-driven constitutive evolution equation for the referential density–originally proposed for the simulation of remodelling effects in bones–and embed this into the micro-sphere-concept to end up with a three-dimensional anisotropic growth formulation. The objective of this contribution is to investigate this approach with emphasis on its application to structural design problems by means of two three-dimensional benchmark-type boundary value problems. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Electronic ISSN: 1617-7061
    Topics: Mathematics , Physics , Technology
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  • 24
    Publication Date: 2013-02-09
    Description: The present work aims at the modelling and simulation of Internal Traverse Grinding of hardened 100Cr6/AISI 52100 using electro plated cBN grinding wheels. We focus on the thermomechanical behaviour resulting from the interaction of tool and workpiece in the process zone on a mesoscale. Based on topology analyses of the grinding wheel surface, two-dimensional single- and multigrain representative numerical experiments are performed to investigate the resulting load-displacement-behaviour as well as the specific heat generation due to friction and plastic dissipation. A thermoelastic-viscoplastic constitutive model is used to capture thermal softening of the material taken into account. Based on previous work, an adaptive remeshing scheme which uses a combination of error estimation and indicator methods, is applied to overcome mesh dependence. In consequence, the formulation allows to resolve the complex deformation patterns and to predict a realistic thermomechanical state of the resulting workpiece surface. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 25
    Publication Date: 2013-11-30
    Description: Landfill gas is composed of methane (CH 4 ) and (CO 2 ) at a ratio of about (60% – 40%), whereby the impact of methane on the greenhouse effect is about 25 times higher than that of carbon dioxide. Bacterial methane oxidation, taking place in the landfill cover layer, helps to reduce the climate active emissions from landfill sites. This contribution presents a theoretical and numerical approach to model the coupled processes of bacterial methane oxidation. An isothermal biphasic model based on the Theory of Porous Media (TPM) and Mixture Theory is introduced as well as the coupled finite element (FE) calculation concept. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 26
    Publication Date: 2013-11-30
    Description: The injection of supercritical CO 2 into deep saline aquifers is regarded as one possible alternative to lessen the impact of emitted CO 2 on the greenhouse effect. During injection, a great variety of thermodynamical and mechanical changes of both the fluid phases and the porous solid matrix can be expected. The prediction of these processes is crucial to prevent from critical incidents during CO 2 injection, such as leakage of CO 2 or contamination of drinking water. For simulation purpose, a macroscopic, fully coupled description of multi-phasic flow inside a deformable porous medium based on the Theory of Porous Media (TPM) is generated. Appropriate constitutive relations are applied to account for changes in the fluid properties of both the saline water and CO 2 during injection and leakage. Furthermore, an elasto-plastic description of solid deformations of the porous matrix is included. The model is tested based on a benchmark problem. Therein, the leakage of CO 2 through an abandoned well after injection is investigated. The fully coupled approach between fluid flow and solid deformation allows additional results to be gained from the simulation. Quantification of the leakage rate through the abandoned well and localisation of phase-change events are addressed to calibrate the presented model. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 27
    Publication Date: 2013-11-30
    Description: The transitional and turbulent flow in the near wall sublayer is now mostly modeled based on the existing knowledge of simple 2D flows. To determine the effect of three dimensionality on the turbulent flow structures and turbulent heat transfer in the near wall areas the authors investigate numerically (SVV) turbulent flow in rotor/stator and rotor/rotor flows (with and without axial throughflow). These simple model flows contain most of the phenomena that are needed to understand more complex, 3D transitional and turbulent flows. Attention is focused on the turbulent characteristics which should have more universal character. To stabilize calculations for high Reynolds numbers (up to Re=800 000) the SVV operator is introduced into the Navier-Stokes and energy equations solver for cylindrical coordinate system without using complex numbers. Code optimization and parallelization have speeded up computations 20 times. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 28
    Publication Date: 2013-11-30
    Description: In this essay a fully coupled, monolithic thermo-mechanical coupled simulation using high-order finite elements based on hierarchical shape-functions in combination with a high-order time-integration scheme using diagonally-implicit Runge-Kutta schemes is presented. The constitutive model is based on a finite strain thermo-viscoelasticity relation of overstress-type. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 29
    Publication Date: 2013-11-30
    Description: In this work we present a novel approach to the modeling of magnetorheological elastomers (MREs) for finite deformations. Keeping in mind the composite nature at the microscale, we employ the microsphere model as an effective tool to capture the constitutive response of the material. The microsphere model has been successfully applied to the modelling of rubber-like materials. Here, we extend this approach by taking into account the effect of the magnetic dipole-dipole interactions on the orientation of the polymer chains. Thus, the presented microsphere model is directly motivated by considering the underlying phenomena at the microscale level. Finally the material model is embedded in a finite element framework and the results of a boundary value problems is presented. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 30
    Publication Date: 2013-11-30
    Description: Finite element simulation of hot working of steel has gained significant importance in steel industries. The aim of describing such processes using the finite element method is to predict phenomena like shrinkage during solidification. Due to this thermo-mechanical behaviour residual stresses appear, which cause cracks and the final steel slab loses its required properties as a result. We propose a two-phase incompressible model based on the Theory of Porous Media (TPM) for a numerical description of steelmaking processes. A thermo-mechanical coupling is required to model a high temperature-dependency. In order to consider thermal expansion of solid, a multiplicative decomposition of the deformation gradient into a mechanical and a thermal part has been applied. The Von Mises J 2 plasticity with isotropic hardening criterion has been selected for the solid-phase of the model. Representative numerical examples, as well as the influence of single material parameters on the model will be shown. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 31
    Publication Date: 2013-10-19
    Print ISSN: 0938-0108
    Electronic ISSN: 1875-0494
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Natural Sciences in General , Technology
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  • 32
    Publication Date: 2013-11-30
    Description: Within measurements of brake pads on the IDS high load Tribometer, the wear of pads was investigated by a new non-contact wear measurement under low normal pressures and low temperatures. The first results show that the wear of the pad in the sliding friction is nearly proportional to the friction work, and inversely proportional to the shear strength. The results are also interpreted by the adhesion theory of friction and Archard's equation. On the basis of further interpretations of shear strength and extension of adhesion theory of friction, the wear is derived as a piecewise linear function, which can evaluate explicitly the effect factors of wear and relative correlations at different pressures and different temperatures. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 33
    Publication Date: 2013-11-30
    Description: The modeling of size effects in elastic-plastic solids, such as the width of shear bands or the grain size dependence in polycrystals, must be based on non-standard theories which incorporate length-scales. This is achieved by models of strain gradient plasticity , incorporating spatial gradients of selected micro-structural fields which describe the evolving dissipative mechanisms. The key aspect of this work is to provide a rigorous incremental variational formulation and mixed finite element design of additive finite gradient plasticity in the logarithmic strain space. We start from a mixed saddle point principle for metric-type plasticity, which is specified for the important model problem of isochoric plasticity with gradient-extended hardening/softening response. To this end, we propose a novel finite element design of the coupled problem incorporating a local-global solution strategy of short- and long-range fields. This includes several new aspects, such as extended Q1P0-type and MINI-type finite elements for gradient plasticity [4]. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 34
    Publication Date: 2013-11-30
    Description: A one-dimensional strain gradient plasticity model is reviewed in the context of Finite Element Method (FEM) solvability. It is found that under certain conditions specified the resulting system of two coupled partial differential equations in space and time leads to a symmetric global stiffness matrix. This is achieved upon standard weak form approach and yields a favorable system for an efficient numerical solution. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 35
    Publication Date: 2013-11-30
    Description: The deformation in polycrystals is often heterogenous, e.g. due to grain size dependent hardening. In a semi-analytical representative volume element (RVE), a log-normal distributed grain size is assumed together with a grain size dependent local plastic behavior. The numerical results are well approximated by a simple analytical expression. The effect of the homogenization comparison stiffness on the transient behaviour is explained using a simplified localization equation. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 36
    Publication Date: 2013-11-30
    Description: In this paper, we present a constitutive model for granular materials exhibiting microstructures using the concept of energy relaxation. Within the framework of Cosserat continuum theory the free energy of the material is enriched with an interaction energy potential taking into account the counter rotations of the particles. The enhanced energy potential fails to be quasiconvex. Energy relaxation theory is employed to compute the relaxed energy which yields all possible displacement and micro-rotations field fluctuations as minimizers. Based on a two-field variational principle the constitutive response of the material is derived. The developed constitutive model is then implemented in a finite element analysis program using the finite element method. Numerical simulations are presented to observe the localized deformation phenomenon in a granular medium. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 37
    Publication Date: 2013-11-30
    Description: In nowadays polymer materials are used in a multitude of different applications. A promising class of smart materials are biodegradable polymers. The present work proposes a micromechanical motivated description of degradation. Since degradation leads finally to an eroding material both cases of erosion, namely bulk and surface erosion, are considered. Degradation is modelled in a strong coupled chemo mechanical framework for an arbitrary spatial motion problem. Deformations arising due to surface erosion are described as material motion. Finally, the modelling concept is embedded in a finite element method. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 38
    Publication Date: 2013-11-30
    Description: For the simulation of the interaction of elastic waves in CFRP plates with inhomogeneities and defects the spectral finite element method (SEM) is under investigation. The SEM uses high-order shape functions which are composed of Lagrange polynomials with nodes at the Gauss-Lobatto quadrature (GLq) points. In this way we obtain a diagonal mass matrix which makes an explicit time scheme more efficient. The goal of this work is to investigate the effect of SEM on the CFL-Condition. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 39
    Publication Date: 2013-11-30
    Description: In this paper, composite structures are considered which consist of several layers of carbon fiber reinforced plastics (CFRP). For such layered composite structures, delamination constitutes one of the major failure modes and hence predicting its initiation is essential for their design. Evaluating stress-strength relation based onset criteria requires an accurate representation of the through-the-thickness stress distribution, which can be particularly delicate in the case of shell-like structures. Thus, in this paper, a solid-shell finite element is utilized, which allows for incorporating a fully three-dimensional material model, still being suited for application to thin structures. Moreover, locking phenomena are cured by using both the EAS and the ANS concept, and numerical efficiency is ensured through reduced integration. The proposed anisotropic material model accounts for the material's micro-structure by using the concept of structural tensors. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 40
    Publication Date: 2013-11-30
    Description: In this contribution, a micromechanical modeling approach in the framework of poromechanics is adopted to study structure-stiffness relations of two quite different species, namely spruce and yew, in detail. In particular, microstructural specialties of yew and spruce are assessed. A dominant influence of the cellulose content and its orientation on the stiffness of the cell wall is revealed, while on the macroscopic scale, density is found to be the governing microstructural characteristic for elastic properties. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 41
    Publication Date: 2013-11-30
    Description: PDE-constrained parameter optimization problems suffer from the high dimensionality of the corresponding discretizations, which results in long optimization runtimes. One possible approach to solve such large scale optimization problems more rapidly is to replace the PDE constraint by a low-dimensional model constraint obtained via model reduction. We present a general technique for certification of such surrogate optimization results by a-posteriori error estimation based on Reduced Basis (RB) models. We allow arbitrary PDEs and optimization functionals, in particular cover nonlinear optimization problems. Experiments on a stationary heat-conduction problem demonstrate the applicability of the error bound. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 42
    Publication Date: 2013-11-30
    Description: In a number of fcc materials such as copper or aluminum, as well as more complex materials such as twinning induced plasticity (TWIP) steels, the interaction between dislocations and other defects such as stacking faults or twins plays an important role in the hardening behavior of such materials. Interactions of dislocation and twin or stacking fault layers have been studied in this work using molecular dynamics. Depending on the material and the loading conditions, possible interaction modes include (i) penetration of the dislocation into the faulted layer, (ii) reduction of the faulted layer after interaction, (iii) growth of the faulted layer after interaction. Such studies up to this point have been performed without temperature control near zero K (0 to 2 K). In this work, we extend the previous studies to higher temperature with the help of two methods, both based on molecular dynamics (MD) modeling. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 43
    Publication Date: 2013-11-30
    Description: The paper reports on Direct Numerical Simulations of bubble-laden flows performed to investigate the interaction of bubbles with turbulence in an upward flow between two parallel vertical plates. Two simulations are presented with uniform bubble diameter and a third one with bi-disperse bubbles. Three different approaches are used to characterize bubble clustering in the investigated configuration. Horizontal pairing and tendency to form cluster has been found for all reported cases, slightly less pronounced in the bi-disperse swarm. Among other results, a 60°-alignment has been found by means of the angular pair correlation function for the mixed pairs in the bi-disperse swarm. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 44
    Publication Date: 2013-11-30
    Description: During wheel bumping caused by stochastic road excitation, the wheel performs rotational and translational movements. The bump and rebound wheel velocity leads to significant angular velocities based on the (elasto-)kinematics of the suspension system. Based on the gyroscopic effect, moments arise about the rotating wheel induced by the angular change while bumping. Therefore it leads to undesirable wheel changes and degrades the tire contact and finally decreases the driving stability. A flexible MBS-model of the five-link rear axle system that includes these effects has been built up to allow a detailed investigation of the gyroscopic effect. Using the simulation results, conclusions can be drawn for refining design criteria for the kinematics, elastokinematics and topology of the suspension system to increase the active safety of the vehicle. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 45
    Publication Date: 2013-11-30
    Description: Dynamics of multi deformable bodies coupled by standard light fractional order discrete continuum layers is described by coupled partial fractional order differential equations. A mathematical analogy and phenomenological mapping between generalized coordinates of fractional order discrete chain systems and eigen time functions correspond to one of infinite numbers of eigen amplitude functions of dynamics of multi deformable bodies (beams, plates or membranes) coupled by standard light fractional order discrete continuum layers are identified. Eigen fractional order vibration modes are approximately determined analytically and graphically presented. A number of theorems is defined and proofed. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 46
    Publication Date: 2013-11-30
    Description: A viscoplastic strain gradient crystal plasticity theory based on the gradient of the equivalent plastic strain ∇γ eq is proposed. A grain boundary yield condition is introduced. The microstructural explanation of the Hall-Petch effect, accounting for notch-like stress concentrations at the grain boundary as a result of discrete slip bands, is reviewed. Periodic tensile test FEM simulation results illustrate the prediction of the numerical model. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 47
    Publication Date: 2013-11-30
    Description: Volume 13 (2013) of PAMM “Proceedings in Applied Mathematics and Mechanics” assembles the contributions to the 84th Annual Meeting of the Gesellschaft für Angewandte Mathematik und Mechanik, held 18 – 22 March 2013 at the University of Novi Sad, Serbia. The contributions are grouped according to the minisymposia and sessions of the conference. Overview of the Sections Minisymposia Mathematics Ma 1 Model reduction for PDEs Minisymposia Mechanics Me 1 Nano-mechanics of carbon nanoparticles Me 2 Size-dependent crystal plasticity: experiment, theory and simulation Me 3 Simulation and modeling of bubbly flows Sections 1–24 1 Multi-body dynamics 2 Biomechanics 3 Damage and fracture mechanics 4 Structural mechanics 5 Nonlinear oscillations 6 Material modelling in solid mechanics 7 Coupled problems 8 Multiscales and homogenization 9 Laminar flows and transition 10 Turbulence and reactive flows 11 Interfacial flows 12 Waves and acoustics 13 Flow control 14 Applied analysis 15 Applied stochastics 16 Optimization 17 Applied and numerical linear algebra 18 Numerical methods of differential equations 19 Optimization of differential equations 20 Dynamics and control 21 Mathematical image processing 22 Scientific computing 23 Applied operator theory Young Researchers' Minisymposia YR Ma2 Analytical and engineering aspects in the material modeling of solids YR Ma3 Numerical methods with non-matching meshes YR Me2 Scale-bridging modeling and simulation – methodological and computational aspects YR Me3 Isogeometric methods
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  • 48
    Publication Date: 2013-11-28
    Description: In this work, we propose an approximate model of evaporation-induced Bénard-Marangoni instabilities in a volatile liquid layer with a free surface along which an inert gas flow is externally imposed. This setting corresponds to the configuration foreseen for the ESA—“EVAPORATION PATTERNS” space experiment, which involves HFE-7100 and nitrogen as working fluids. The approximate model consists in replacing the actual flowing gas layer by an “equivalent” gas at rest, with a thickness that is determined in order to yield comparable global evaporation rates. This allows studying the actual system in terms of an equivalent Pearson’s problem (with a suitably defined wavenumber-dependent Biot number at the free surface), allowing to estimate how far above critical the system is for given control parameters. Among these, a parametric analysis is carried out as a function of the liquid-layer thickness, the flow rate of the gas, its relative humidity at the inlet, and the ambient pressure and temperature.
    Print ISSN: 0938-0108
    Electronic ISSN: 1875-0494
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Natural Sciences in General , Technology
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  • 49
    Publication Date: 2013-11-30
    Description: Articular cartilage is a multiphase material consisting of fluids and electrolytes, which is described with the Theory of Porous Media. The mechanical characteristics of articular cartilage are porosity, incompressible material behavior combined with transversely isotropic behavior for solid and fluid phases. There are two central points to model articular cartilage: the poro-viscosity of the porous matrix and the visco elasticity, and orientation of the collagen fibers. A numerical example is presented. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 50
    Publication Date: 2013-11-30
    Description: Orientation of collagen fibers and their spatial distribution predefine macroscopic mechanical properties of the soft tissue and in particular its anisotropy directions. In this contribution, we apply two different procedures to automatically generate these directions for a 3D FE-model. The first procedure is based on an analogy with a heat conduction problem. Accordingly, a thermal flux under certain temperature boundary conditions is calculated by the same FE model and is further utilized for the definition of the anisotropy directions. The numerical result shows good agreement with Langer's lines data in human skin. Within the second procedure, the fiber vector field is calculated by the Laplacian smoothing method based on the user defined fiber direction sketches. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 51
    Publication Date: 2013-11-30
    Description: The current paper proposes a model for describing mechanical phenomena that occur during the process of mammal fertilization when spermatozoa impact the surface of Zona Pellucida. Zona pellucida (ZP) is a dynamical 3D matrix that surrounds the mammalian oocyte. In the process of fertilization, sperm cell has to penetrate this structure. To describe impact of sperm cells with velocities that are effective and those that are ineffective relative to the oscillatory behavior of ZP , the discreet continuum model in the form of spherical net model is used. Resultant trajectories of knot mass particles dynamics of mouse ZP spherical net model in the form of generalized Lussajous curves are presented. Using generalized Lussajous curves, parametric frequency analysis of oscillatory behavior of knot material particles in the mouse ZP spherical net model is conducted. The influence of impact angles of sperm cells on corresponding knot mass particle trajectory is discussed. Favorable and unfavorable trajectories of knot mass particle motions are discussed in the context of successful fertilization. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 52
    Publication Date: 2013-11-30
    Description: Multi body system contains finite number of rigid bodies that are placed on each axis, which do not intersect each other. Derivatives of the linear momentum and angular momentum with respect to time by use mass moment vectors and vector rotators for pole and axis, are determined. A number of theorems are defined. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 53
    Publication Date: 2013-11-30
    Description: In the present work the mechanical behaviour of a dual-rotor vibrotactor has been investigated with special attention to its stationary motions and their linear stability. After the introduction of the used mechanical model, the formulae for the stationary motions are given, and characteristic stablity charts are presented. The linear stability is investigated for uncontrolled and controlled system as well. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 54
    Publication Date: 2013-11-30
    Description: This work is devoted to parametric study on creep-fatigue endurance of the steel AISI type 316N(L) weldments defined as type 3 according to R5 Vol. 2/3 procedure at 550°C. The study is implemented using a novel direct method known as the Linear Matching Method (LMM) and based upon the creep-fatigue evaluation procedure considering time fraction rule for creep-damage assessment. Seven geometrical configurations of the weldment, which are characterised by individual values of a geometrical parameter ρ, are proposed. Parameter ρ, which represents different grades of TIG dressing, is a ratio between the radius of the fillet of the remelted metal on a weld toe and the thickness of welded plates. For each configuration, the total number of cycles to failure N * in creep-fatigue conditions is assessed numerically for different loading cases including normalised bending moment and dwell period Δ t . The obtained set of N * is extrapolated by the analytic function dependent on , Δ t and ρ. Proposed function for N * shows good agreement with numerical results obtained by the LMM. It is used for the identification of Fatigue Strength Reduction Factors (FSRFs) effected by creep and dependent on Δ t and ρ. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 55
    Publication Date: 2013-11-30
    Description: We introduce a consistent variational framework for inelasticity at finite strains, yielding dual balances in physical and material space as the Euler equations. The formulation is employed for the simultaneous usage of configurational forces as both driving forces for crack propagation as well as h -adaptive mesh refinement. The theoretical basis builds upon a global balance of internal and external power, where the mechanical response is exclusively governed by two scalar functions, the free energy function and a dissipation potential . The resulting variational structure is exploited in the context of fracture mechanics and yields evolution equations for internal variables. In the discrete setting, we present a geometry model fully separated from the finite element mesh structure that represents structural changes of the material configuration due to crack propagation. Advanced meshing algorithms provide an optimal discretization at the crack tip. Local and global criteria are obtained via error estimators based on configurational forces being interpreted as indicators of an energetic misfit due to an insufficient discretization. The numerical handling is decomposed into a staggered algorithm scheme for the dual set of equilibrium equations in material and physical space and efficient mesh generation tools. Exemplary numerical examples are considered to illustrate the method and to underline the effects of inelastic material behaviour in the presented context. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 56
    Publication Date: 2013-11-30
    Description: The contribution adresses the simulation of ferroelectric matrials in the framework of the Piezoresponse Force Microscopy (PFM). Based on the PFM, ferroelectric domain structures can be analyzed in great detail by measuring the electrically induced mechanical deformations of the surface of a ferroelectric. We employ a flexible continuum-mechanical model based on the phase-field method in order to analyze the behavior of ferroelectric microstructures numerically. Since ferroelectric materials are often highly anisotropic, the phase-field formulation will account for transversely isotropic symmetry. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 57
    Publication Date: 2013-11-30
    Description: The present contribution deals with the atomistic modelling of ferroelectric barium titanate. In this context a core-shell model is implemented in a Molecular Static algorithm. Furthermore, Coulomb forces are simulated by the Wolf summation method in order to allow for a small cut off radius. We discuss the core-shell model, molecular statics as a finite elements approach and present some numerical results. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 58
    Publication Date: 2013-11-30
    Description: This work is concerned with the material modeling of the inelastic behavior of bonding and debonding effects in adhesive layers. High-strength adhesives are applied in building industries utilizing thick adhesive layers due to huge building elements and construction tolerances. Therefore a continuum approach is presented to describe the nonlinear material behavior. In the failure criterion two stress invariants are used, which involves the hydrostatic pressure as well as the deviator stress state. A non-associated flowrule, which determines the evolution of the inelastic variables, is required to ensure the thermodynamical consistency of the model. Hardening and softening are included as well as the rate-dependency of the adhesive. Furthermore the viscoplastic approach is used for regularization of the mesh dependency in case of material softening. The nonlinear material model is implemented in a finite element program. The material tangent modulus is incorporated to obtain quadratic convergence for the global equilibrium iteration. The identification of material parameters is discussed on the simulation of typical experiments for adhesive materials. As a drawback of the presented phenomenological material model, the large number of parameters involved in the constitutive description is discussed. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 59
    Publication Date: 2013-11-30
    Description: In this work a material model for shape memory alloy (SMA) fibers is presented. A constitutive model is provided which aims for computational use. The presented model incorporates all relevant material nonlinear phenomena. It takes pseudoplasticity into account as well as pseudoelasticity and further the shape memory effect (SME). The constrained SME (CSME) and the two-way SME are covered by the presented material model. The constitutive model is implemented in a one-dimensional truss formulation and in a 3D-rebar element. Both formulations are used to model fiber composite structures. Those are described by the use of a non-conforming and a conforming mesh on the mesoscale. The numerical examples show the capability of the formulation. Different meshing strategies for the fiber–matrix compound are discussed. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 60
    Publication Date: 2013-11-30
    Description: From a macroscopic point of view, the deformation of most metals results in an evolution of the symmetry groups characterizing the isotropy of the considered materials. With respect to plastic deformation for instance, the shape of the macroscopic yield surface evolves during deformation. In the present paper, a novel constitutive framework capturing this evolution is proposed. This framework is based on the fundamentals of thermodynamics. Furthermore, it also shows a variational structure such that all state variables follow jointly from minimizing an incrementally defined energy functional. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 61
    Publication Date: 2013-11-30
    Description: There exists a large variety of different techniques used to generalize the Prandtl-Reuss relations of small strain elasto-plasticity to finite strains. Obviously, any systematic study of such generalization techniques should be based on some sound principles. In this work, one aspect is taken into account, concerning arbitrary isochoric change of the local reference configuration. We analyze some models of finite strain elasto-plasticity in order to find out if the specific choice of the reference configuration can affect the predicted stress response. For material models which remain invariant under the reference change, no preferred reference configuration exists. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 62
    Publication Date: 2013-11-30
    Description: Quasi-static cyclic loading tests on filled rubber-like materials reveal a significant stress softening in the first cycle. The magnitude of this softening, widely known as the Mullins effect, reduces in the next cycles until it reaches a stabilized value referred to as hysteresis. In this contribution, we associate the hysteresis with the fracture of carbon bonds in the filler network. In order to calculate the cyclic energy dissipation, we modify the classic concept of network decomposition [1, 2] and add a new network considered to be responsible for the breakage and re-formation of carbon black aggregates during loading and unloading. The proposed model is in-line with a wide range of experimental observations. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 63
    Publication Date: 2013-07-31
    Description: The separation of multiphase flow constituents in a microgravity environment is of considerable interest as the functionality of many spacecraft systems is dependent on the proper sequestration of interpenetrating gas and liquid phases. Cyclonic separators provide the desired gas-liquid separatory action by swirling the multiphase flow—causing the gas to accumulate along the axis of the vortex as the denser liquid is forced to the walls—thereby allowing segregated extraction of the respective phases. Passive cyclonic separators utilize only the inertia of the incoming flow to accomplish this task. In the current work, combined experimental, numerical, and phenomenological modeling analyses have been performed to quantitatively describe the steady and dynamic response of these separators. Specifically, the gas core behavior under steady conditions as well as under single-phase and multiphase injection step-changes have been examined experimentally and compared to computational fluid dynamics results. Also, a simple control-volume analysis of the cyclonic separator has been created and compared to these results. The results afford insight into the transient behavior of the device with respect to both the device and system-level conduct.
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  • 64
    Publication Date: 2013-04-26
    Description: Transient phenomenon of laminar film condensation along a vertical flat plate under sinusoidal g-jitter has been analyzed, based on the same assumptions of Nusselt’s analysis of film condensation where the heat transfer within the liquid film is by pure conduction. The momentum equation retains the transient term. The perturbed acceleration due to gravity has been assumed to be a sinusoidal function of time and frequency of oscillation for the simplicity. The resultant equation has been solved analytically and the velocity profiles and mass flow rate under such g-jitter has been simulated. It has been observed that at the different heights the velocity response with time is purely sinusoidal with different amplitude. Last but not the least; boundary layer thickness is also oscillating with time, hence heat transfer coefficient. However, the entire analysis is an extension of Nusselt’s analysis of film condensation which includes transient response.
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  • 65
    Publication Date: 2013-04-26
    Description: The effect of temperature dependent viscosity on the onset of Marangoni-Bénard ferroconvection under microgravity conditions in a horizontal ferrofluid layer in the presence of a uniform vertical magnetic field has been studied. The viscosity is considered to be varying exponentially with temperature. The lower rigid and the upper horizontal free boundaries are considered to be perfectly insulated to temperature perturbations. The resulting eigenvalue problem is solved numerically using the Galerkin technique as well as analytically by regular perturbation technique with wave number a as a perturbation parameter. It is observed that the analytical results agree well with those obtained numerically. The characteristics of stability of the system are strongly dependent on the viscosity parameter B . It is found that increase in the viscosity parameter B has a stabilizing effect on the onset of Marangoni-Bénard ferroconvection. Moreover, the nonlinearity of fluid magnetization M 3 is observed to have no consequence on the onset of convection in the case of fixed heat flux boundary conditions.
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  • 66
    Publication Date: 2013-05-18
    Description: In order to improve depiction of pressure variation and investigate the interrelation among the physical processes in propellant tanks, a 2D axial symmetry Volume-of-Fluid (VOF) CFD model is established to simulate a large-sized liquid propellant tank when the rocket is preparing for launch with propellant loaded at the launch site. The numerical model is considered with propellant free convection, heat transfer between the tank and the external environment, thermal exchange between propellant and inner tank wall surfaces, gas compressibility, and phase change modeled under the assumption of thermodynamic equilibrium. Vaporization rate of the vented LH2 tank and prediction of pressure change in the tank pressurized with GHe are obtained through simulation. We analysis the distributions of phase, temperature, and velocity vectors to reveal interactions among the propellant’s own convection motion, heat transfer and phase change. The results show that the vaporization rate is mainly affected by heat leaks though the tank wall when the tank is vented, but it does not completely accord with the trend of the leakage because of convection motion and temperature nonuniformity of the liquid propellant in the tank. We also find that the main factors on pressure variation in the pressurized tank are the heat transfer on the tank wall surface bonding the ullage and propellant vaporization which has comparatively less influence.
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  • 67
    Publication Date: 2013-05-15
    Description: The influence of the horizontal component of the temperature gradient on nonlinear oscillatory convective flows, developed under the joint action of buoyant and thermocapillary effects in the 47 v2 silicone oil - water system, is investigated. The layers of equal thicknesses are considered. Transitions between nonlinear regimes of convection, have been studied. It is shown that under the action of the horizontal component of the temperature gradient, the asymmetric oscillatory flow takes place in the system.
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  • 68
    Publication Date: 2013-11-20
    Description: This paper reports a theoretical investigation on rapid evaporation of a saline droplet during depressurization. A mathematical model was developed to simulate the droplet temperature variation by considering the ambient pressure change, the heat transfers due to evaporation and convection at the droplet surface, accompanying the heat and mass transfer inside the droplet. The component diffusion and the temperature gradient inside the droplet were mainly discussed by comparing the numerical droplet temperature with the experimental data. The result shows that, the variation of internal concentration is small, while the temperature gradient within the droplet is significant during the evaporation process. In addition, the influencing factors of the droplet temperature variation were analyzed, such as: the final ambient pressure, theinitial salt concentration and the initial droplet temperature. The present model calculations help to understand the thermodynamic process of rapid evaporation of a saline droplet during depressurization.
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  • 69
    Publication Date: 2013-01-03
    Description: In this paper the linear theory of viscoelasticity for Kelvin-Voigt materials with voids is considered. The uniqueness and existence theorems for internal boundary value problem (BVP) of steady vibrations are proved by means of the potential method (boundary integral method) and the theory of singular integral equations. The application of this method to the 3D BVP of the considered theory reduces this problem to 2D singular integral equation. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 70
    Publication Date: 2013-09-04
    Description: In the published microgravity bubbly-slug data sets, the average critical void fraction for the bubbly-to-slug transition is observed to cluster around $\sim $ 0.20 and $\sim $ 0.45. The origin of what causes there to be two data subsets remains an open question. The $\sim $ 0.20 and $\sim $ 0.45 critical void fractions were reported by one researcher to occur during 1-g and $\mu $ -g intervals on a reduced gravity aircraft, respectively. This suggests that the experiments belonging to the $\sim $ 0.20 data subset may have encountered undue buoyancy effects or perturbations which may have caused the bubbly-to-slug flow regime transitions to occur at prematurely low void fractions. Should this assertion hold, the ∼0.20 data subset can be treated separately from the ∼0.45 data subset, which provides a much clearer picture of the bubbly-to-slug flow regime transition. A new theory has been developed which explains the mechanics of the $\sim $ 0.45 data subset, for which corresponding physical and dimensionless models have been derived. The new theory and models are validated by their clear fit to the entirety of the published ∼0.45 data subset, however, they do not offer a firm explanation of the mechanics of the $\sim $ 0.20 data subset. This provides further indication that these two data subsets are indeed different. Further investigation into the differences between experiments and the manner in which they were conducted may explain the existence of these two data subsets.
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  • 71
    Publication Date: 2013-06-30
    Description: In order to understand the transition characteristics of the thermal-solutal capillary convection in an annular pool, a series of two-dimensional numerical simulations were conducted. The bottom of the pool is adiabatic rigid wall and the top is adiabatic and non-deformable free surface. The inner and outer cylindrical walls maintain at constant temperature and solute concentration, respectively. The thermo-capillary force is supposed to equal to the solute-capillary force, but their directions are contrary. Results show that the thermal-solutal capillary convection is steady at a small Reylonds number. When the capillary Reynolds number exceeds a critical value, the steady flow transits into unstable thermal-solutal capillary convection. The transition from the steady to oscillatory flow undergoes a Hopf bifurcation. Furthermore, the effects of the liquid layer aspect ratio, the radius ratio, the Prandtl number and the Lewis number on the onset of flow pattern transition are discussed. The physical mechanism of the unstable thermal-solutal capillary convection is also analyzed.
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  • 72
    Publication Date: 2013-11-02
    Description: Numerical simulations on the effects of axial magnetic fields on the thermocapillary convection in a liquid bridge of silicone-oil-based ferrofluid under zero gravity have been conducted. The Navier-Stokes equations coupled with the energy conservation equation are solved on a staggered grid, and the mass conserving level set approach is used to capture the free surface deformation of the liquid bridge. The obvious effects of the magnetic fields on the flow pattern as well as the velocity and temperature distributions in the liquid bridge can be detected. The axial magnetic fields suppress the thermocapillary convection and a stagnant flow zone is formed between the circulating flow and the symmetric axis as the magnetic fields increase. The axial magnetic fields affect not only the velocity level inside the liquid bridge but also the velocity level on the free surface. The temperature contours near the free surface illustrates conduction-type temperature profiles at moderate strength fields.
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  • 73
    Publication Date: 2013-08-17
    Description: The Brazilian Microgravity Program is mainly based on experiments carried out on sounding rockets. A solidification furnace, capable of producing temperatures up to 900 °C, was developed to process metal and semiconductor alloys in microgravity environment. This paper describes a solidification experiment made in this furnace during a parabolic flight, with two eutectic alloys. The behavior of the eutectic alloys PbSn with 26.1 Pb at. % composition, and PbTe with 10.9 Pb at. % composition were presented and compared with laboratory solidifications carried out in the same furnace and thermal cycle. It was concluded that the formation of dendritic structures in PbSn alloy is related to the presence of sedimentation and convective flow during solidification, and the size of these structures is connected to the solidification time. Thus, in the microgravity alloy, there was no formation of dendritic structures and the profile of solute distribution remained constant throughout the sample. For the PbTe eutectic alloy the microgravity conditions have not caused significant changes compared to the earth solidified sample.
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  • 74
    Publication Date: 2013-08-17
    Description: We report on ground-based studies in course of preparation of the experiment DCMIX 2 (Diffusion coefficient in mixtures) to be performed on the International Space Station (ISS). In microgravity experiment the diffusion and thermodiffusion coefficients will be measured at six points with different compositions of the ternary mixture Toluene-Methanol-Cyclohexane. This mixture attracts attention of the researchers, as it has a miscibility gap and presumably large region with negative Soret coefficients. By using Optical Digital Interferometry we have measured the variations of refractive index Δ n in the full parameter space of concentrations. The regions of stable and unstable behavior of system were determined from the time-dependent behavior of Δ n . The system is hydrodynamically unstable in a wide region of compositions where Soret measurement should be done in microgravity. We present the results of the study of the compatibility of this mixture with often used sealing materials:Viton (R), Chemraz (R) and different types of Kalrez. To facilitate the expected theoretical studies we have measured density and thermal expansion in the points of the interest.
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  • 75
    Publication Date: 2013-07-31
    Description: The article considers the joint flow of a liquid film entrained by turbulent gas. Since liquid velocity is small in comparison with gas velocity, the problem is reduced to the calculation of pressure and shear stresses produced by the gas flowing over a wavy wall with small amplitude. Further, these data are used at the boundary conditions, when the flow of a liquid film is considered separately. As a result, we obtain a new system of equations for modeling the dynamics of long-wave perturbations on the surface of a viscous liquid film entrained by turbulent gas at microgravity. At small Reynolds numbers typical to the condition of microgravity, it was proved that this system is reduced to one evolution equation for the film thickness. Some numerical solutions of this equation have been received in this work.
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  • 76
    Publication Date: 2013-04-10
    Description: This paper examines the evaporation rate through the interface of a evaporating—convecting non-isothermal cylindrical column (liquid bridge). The liquid phase is subject to a vigorous thermocapillary convection. Experiments were performed in a wide range of the imposed temperature difference. The obtained data are compared to a theoretical model of mass transport that does not account for the bulk fluid flow. The analytical results obtained for the real experimental conditions reveal an important role of the convective heat and mass transport in evaporization. The convective process is found responsible for enhancing the evaporation rate by several times with respect to the conductive regime.
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  • 77
    Publication Date: 2013-04-10
    Description: This study has been performed in the frame of preparing the space experiment JEREMI (Japanese and European Research Experiment on Marangoni Instabilities). The use of forced coaxial gas flow is proposed as a way to stabilize the Marangoni convection in liquid bridges, which might have important technological applications in the floating zone technique. A new set-up is under development and all sub-systems have passed severe tests. Here we present the design of this set-up and preliminary results of experiments for shear-driven two-phase flows in a confined volume of liquid under conditions of normal gravity. The geometry corresponds to a cylindrical liquid bridge concentrically surrounded by an annular gas channel with external solid walls. Gas enters into the annular duct, flows between solid walls and upon reaching the liquid zone entrains initially quiescent liquid. The test liquids are ethanol, n-decane and 5 cSt silicone oil, which have different degrees of viscosity and of volatility. The gas flow along the interface strongly enhances the evaporation and, correspondingly, affects the interface shape. Silhouette measurements are used for optical determination of the interface shape. From the digital images the variation of the liquid volume as a function of flow rate is calculated.
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  • 78
    Publication Date: 2013-06-03
    Description: The fast-rotating 2-D clinostat, a ground-based facility for investigations in simulated microgravity, is mainly used for experiments with cell suspensions. Here, we describe the adaptation of a 2-D clinostat for adherent cell investigations using commercially available slide flasks. As a gradient of residual accelerations is present in the slide flasks during clinorotation, the range of maximal g-values has to be adjusted to the investigated cells and type of analysis. For gene expression analysis, a harvesting slide chamber was constructed, allowing collection of cells exposed to defined g-values. Using this slide chamber, human 1F6 melanoma cell line, exposed in the ranges of ≤0.012 g, ≤0.024 g, or ≤0.036 g for 24 h, was harvested and the respective mRNA levels of guanylyl cyclase A (GC-A), an enzyme catalyzing cyclic GMP synthesis, were determined by real-time quantitative PCR analysis. Our results show that the down-regulation of GC-A mRNA levels in 1F6 melanoma cells depends on the residual acceleration values with a maximal reduction at ≤0.012 g. We further used the slide flasks by the clinorotation of murine RAW 264.7 macrophage cell line for f-actin analysis. The laser scanning microscopy images of cells exposed to g-values of ≤0.006 g for 1 h show an increase in the cell size of clinorotated cells, but no rearrangement in the f-actin filament system compared to static 1-g controls. Thus, 2-D clinostats equipped with slide flasks can be used for adherent cell experiments, however, the maximal g-values have to be carefully considered.
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  • 79
    Publication Date: 2013-11-30
    Description: A flow structure interaction of a membrane and a fluid is investigated. A conventional segregated numerical algorithm, where the membrane deformation and the flow dynamics are calculated alternately has to fail due to the artificial added mass instability. Thus, a new iteration scheme is proposed. In order to get a good prediction for the deformation of the membrane, the equations describing the membrane are coupled to a potential flow solver (panel method). Then a CFD solver can be used to determine the corrections of the flow field due viscosity and turbulence. An example is presented that this procedure seems to be numerically stable. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 80
    Publication Date: 2013-11-30
    Description: A multivariant phase field model for martensitic transformations in elastoplastic materials is introduced which is in mathematical terms the regularization of a sharp interface approach. The evolution of microstructure is assumed to follow a time dependent Ginzburg-Landau equation. The coupled problem of the mechanical balance equation and the evolution equations is solved using finite elements and an implicit time integration scheme. In this work, plasticity is considered for the austenitic phase which influences the martensitic evolution. With aid of the model these interactions are studied in detail. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 81
    Publication Date: 2013-11-30
    Description: We discuss generalized boundary conditions for representative volume elements (RVE), which include the classical boundary conditions as special cases. From the generalization, stochastic boundary conditions are derived. These allows to adjust the the stiffness of the boundary conditions smoothly between the extremal cases of homogeneous strain and homogeneous stress boundary conditions. We found that it needs to be distinguished between the resistance of the boundary conditions against homogeneous and inhomogeneous RVE deformation. The stochastic BC can combine the moderate stiffness of the well known periodic boundary conditions with the high resistance against localization of the homogeneous strain boundary conditions. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 82
    Publication Date: 2013-11-30
    Description: In the present contribution, the problem of non-linear deformation of materials with stochastically distributed anisotropic inclusions is considered on the basis of the methods of mechanics of stochastically non-homogeneous media. The homogenization model of materials of stochastic structure with physically non-linear components is developed for the case of a matrix which is strengthened by unidirectional ellipsoidal inclusions. It is assumed that the matrix is isotropic, deforms non-linearly; inclusions are linear-elastic and have transversally-isotropic symmetry of physical and mechanical properties. Stochastic differential equations of physically non-linear elasticity theory form the underlying equations. Transformation of these equations into integral equations by using the Green's function and application of the method of conditional moments allow us to reduce the problem to a system of non-linear algebraic equations. This system of non-linear algebraic equations is solved by the Newton-Raphson method. On the analytical as well as the numerical basis, the algorithm for determination of the non-linear effective characteristics of such a material is introduced. The non-linear behavior of such a material is caused by the non-linear matrix deformations. On the basis of the numerical solution, the dependences of homogenized Poisson's coefficients on macro-strains and the non-linear stress-strain diagrams for a material with randomly distributed unidirectional ellipsoidal pores are predicted and discussed for different volume fractions of pores. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 83
    Publication Date: 2013-11-30
    Description: In this paper, we present a numerical procedure that can be used to model the electro-mechanical coupled behavior of the dielectric actuator domain. The equation describing the electrostatical part is given by the reduced form of the Maxwell equation and the electrostatic potential [1]. The mechanical problem is described by the constitutive equations and equilibrium equations. Using the finite element method, this technique is to divide a whole problem into sub-problems. The complexity of the original problem is therefore reduced by focusing only on the most relevant areas. A finite element analysis is then performed by applying the electrostatic Maxwell pressure as Neumann boundary conditions to compute the displacements. Once the displacement is computed, the electrostatic domain or the conductor is updated. Electrostatic analysis is performed on the updated geometry and the finite element method is then used to determine the change in potential due to geometric perturbations. Once the surface charge densities are known, the new electrostatic Maxwell pressure is computed. The mechanical and electrostatic analysis is repeated until an equilibrium state is computed. The procedure is demonstrated in the paper by the solution of some two-dimensional and three-dimensional problems. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 84
    Publication Date: 2013-11-30
    Description: In this work a comparison of polycrystal and classical continuum models illustrated by examples of full structures is investigated. The general idea is to represent the averaged distribution of displacement, stress and strain fields for statistically randomized realizations of discrete structures. A technique for averaging fields in the FEM program ABAQUS is proposed and implemented. To improve the computation efficiency mesh dependence was investigated. Results of simulation are given for a rectangular plate and for the Kirsch's problem for both examples elastic as well as inelastic material behavior. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 85
    Publication Date: 2013-11-30
    Description: This paper presents a quasi-static solution for the mechanically coupled diffusion problem in a Lithium-ion battery thin film electrode during charge. The concentration field and the stresses are calculated under the assumption of a constant flux. The influence of the electrode's stiffness, its thickness, and of the current density on the results are discussed. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 86
    Publication Date: 2013-11-30
    Description: The reformulation in conservative form of the higher-dimensional continuum dislocations dynamics(hdCDD) theory of Hochrainer (Ph.D. thesis, 2006) is presented together with a framework for elasto-plasticity problem based on this theory. A Runge-Kutta discontinuous Galerkin(RKDG) method is used for the evolution of hdCDD to obtain information of the micro-structure which is coupled with a finite element method for the stress computation. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 87
    Publication Date: 2013-11-30
    Description: In this work, we analyze a strategy for the selection of the adequate RVE size for elastic problems on thin sheets with strong texture. The selection strategy includes the construction of the geometric descriptor as periodic tesselation of the sheets and the stochastic assignment of stiffness matrices for the different material grains inside the RVE. The procedure is illustrated with an example on DC01 steel sheets with thickness 50 µm. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 88
    Publication Date: 2013-11-30
    Description: The motion and interaction of dislocation lines are the physical basis of the plastic deformation of metals. Although ‘discrete dislocation dynamic’ (DDD) simulations are able to predict the kinematics of dislocation microstructure (i.e. the motion of dislocations in a given velocity field) and therefore the plastic behavior of crystals in small length scales, the computational cost makes DDD less feasible for systems larger than a few micro meters. To overcome this problem, the Continuum Dislocation Dynamics (CDD) theory was developed. CDD describes the kinematics of dislocation microstructure based on statistical averages of internal properties of dislocation systems. In this paper we present a crystal plasticity framework based on the CDD theory. It consists of two separate parts: a classical 3D elastic boundary value problem and the evolution of dislocation microstructure within slip planes according to the CDD constitutional equations. We demonstrate the evolution of dislocation density in a micropillar with a single slip plane. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 89
    Publication Date: 2013-11-30
    Description: In this work, a micromechanically motivated affine full network model (AFNM) is used to simulate the load-displacement response of nonwoven materials. These materials are made from synthetic advanced fibers by bonding or interlocking networks of randomly laid fibers through mechanical, chemical or thermal processes. This results into a random fibrous network microstructure and a highly inhomogeneous response to external loadings with a very high degree of anisotropy. The load-displacement response under large strains is observed to be highly non-linear with a stiffening behavior which is also accompanied by complex dissipative phenomena. The preliminary simulation results with the AFNM, after reducing to two-dimensional setting, highlight its limitations and help identify the areas of improvement for a realistic material modeling. Reorientation of fibers are shown to play a critical role in the overall macroscale response of the materials. A new evolution law for reorientation is presented in the form of a first order ordinary differential equation where an exact analytical solution to the same is also computed. Improvements of the predicted load-displacement response signify the microscopic origins of the non-linear stiffening behavior as reorientation of fibers. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Electronic ISSN: 1617-7061
    Topics: Mathematics , Physics , Technology
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  • 90
    Publication Date: 2013-11-30
    Description: The finite cell method is extended to enable the computation of solids consisting of heterogeneous materials. The approach is based on a domain decomposition utilizing the hp-d method. Our results reveal that the proposed method improves the accuracy of the finite cell method significantly. It also paves the way for combining the finite cell method with other approaches like partition of unity based methods which can be of interest in many cases, such as dealing with composites and numerical homogenization. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Electronic ISSN: 1617-7061
    Topics: Mathematics , Physics , Technology
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  • 91
    Publication Date: 2013-11-30
    Description: The focus of this paper is on the simulation of two-phase magneto-electric (ME) composites, consisting of a piezoelectric matrix with piezomagnetic inclusions. In such composites, the coupling between electric and magnetic fields is strain-induced and thus ME coupling arises as a product porperty. In order to compute the effective properties of the composite a computational homogenization scheme based on the Finite Element Method will be applied. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Electronic ISSN: 1617-7061
    Topics: Mathematics , Physics , Technology
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  • 92
    Publication Date: 2013-11-30
    Description: The mechanical vibrations have been perceived as unhealthy, although in some circunstances these may lead to a human body fortification. The trainings that use the vibrating stimulus have certain advantages to the classical trainings. Stabilizers and postural muscles are less visible, being hidden by large muscle groups and have little growth potential. For this reason most types of training does not focus on training and strengthening them. This article presents the advantages of training muscular groups of the vertebral column performed on vibrating plates. This type of training has the advantage that besides the requiring to all muscles in where the vibratory stimulus reaches, leads to an increase flexibility of joints. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Electronic ISSN: 1617-7061
    Topics: Mathematics , Physics , Technology
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  • 93
    Publication Date: 2013-11-30
    Description: The authors of this paper aim to highlight issues related to the organology and the integration of the hardware component in the mechanical structure of a tracked mini robot, called Robo Geniu , part of the unmanned ground vehicles category having the ability to act autonomously and enabling its endowment with means of observation, listening, tapping, relaying and jamming. This paper reveals, in detail, the composing parts of the hardware component, as well as the way they are assembled in the mechanical structure of the mini robot under study. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Electronic ISSN: 1617-7061
    Topics: Mathematics , Physics , Technology
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  • 94
    Publication Date: 2013-11-30
    Description: Computational expenses restrict the usage of continuum mechanics in modelling (parts of) the musculoskeletal system, although, continuum mechanics would provide the possibility to represent the complex mechanical behaviour of a muscle-tendon complex (MTC). This work provides an overview on a modelling framework, which aims to achieve forward-dynamics simulations of musculoskeletal systems by coupling three-dimensional continuum-mechanical-based finite element simulations to rigid-body simulations based on a simplified two-muscle upper arm model. Here, the focus is on implementing a sophisticated representation of the skeletal MTC and tissue-bone interaction. The three-dimensional continuum-mechanical description of the skeletal muscle is described within the framework of finite elasticity. To model the MTC, two additional parameters are introduced providing the possibility to describe muscle tissue, tendon tissue, and soft tissue within one set of constitutive equations. Further, a realistic fibre orientation for the skeletal muscles and contact mechanics between the muscles and the bones is considered. For different elbow flexion angle positions, the muscles' mechanical state is compared with and without considering contact mechanics. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Electronic ISSN: 1617-7061
    Topics: Mathematics , Physics , Technology
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  • 95
    Publication Date: 2013-11-30
    Description: Two approaches of including active contractile behaviour of muscle tissue written in a continuum-mechanical formulation are presented. One approach relies on the addition of active and passive stress contributions, while the other approach is based on a multiplicative decomposition of the deformation gradient tensor. Both formulations can be stated in a thermodynamically consistent manner, each with different constraints, and both models can reproduce experimental data of passive and fully active muscle. Different behaviours are observed when comparing the active muscle models at submaximal stimulation rates. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Electronic ISSN: 1617-7061
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  • 96
    Publication Date: 2013-11-30
    Description: The reinforcement of porous vertebral cancellous bone by the injection of bone cement is a practical procedure for the stabilisation of osteoporotic compression fractures and other weakening lesions. This contribution concerns the reproduction and prediction of the resulting bone-cement distribution during the injection procedure by means of numerical simulation. A detailed micromechanical (locally single-phasic) model exhibits the drawback that all geometrical and physical transition conditions of the individual parts of the complex aggregate have to be known. Therefore, we rather proceed from a macroscopic (and multi-constituent) continuum-mechanical model based on the Theory of Porous Media. In this regard, the homogenisation of the underlying micro-structure results in a model of three constituents: these are the solid bone skeleton, which is saturated by the liquid bone marrow that may be displaced by the injected liquid bone cement. The influence of the micro-architecture of the pore space on the spreading of the bone cement is considered by a spatial diversification of the anisotropic permeability tensors, obtained through image processing techniques applied to medical imaging data (µCT). The numerical investigation of the strongly coupled problem enables the study of vertebroplasty and allows for the comparison between the simulation results and the experimentally determined bone-cement distribution that were imaged during injections. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Electronic ISSN: 1617-7061
    Topics: Mathematics , Physics , Technology
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  • 97
    Publication Date: 2013-11-30
    Description: In this contribution we investigate the influence of dispersed microscopic quantities on the damage behavior in collagenous tissues. Therefore, we derive a damage model, that may take into account statistical distributions of collagen fiber properties. In detail, we regard distributions of the orientation of fibril-interconnecting proteoglycan (PG) bridges and of an internal fibril length parameter. The damage model is embedded into the constitutive framework from [1] and a numerical example in a finite element framework is given. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Electronic ISSN: 1617-7061
    Topics: Mathematics , Physics , Technology
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  • 98
    Publication Date: 2013-11-30
    Description: The presented continuum mechanical model describes isotropic and transversely isotropic growth in biphasic materials with focus on biological tissue. The model is capable to describe full isotropic growth, full transversely isotropic growth as well as a combination of both types. This approach is chosen to describe the most common occurring growth types, namely isotropic and transversely isotropic growth, but also to describe effects where the growth of the investigated body depends on multiple single growth effects that are difficult to distinguish among each other. For the description of growth a biphasic homogenized approach within the framework of the theory of porous media (TPM) is used. In this work we focus on the applied formulation of multiple multiplicative decoupling of the deformation gradient into elastic, growth, isotropic and transversely isotropic parts including the governing constitutive equations. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Electronic ISSN: 1617-7061
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  • 99
    Publication Date: 2013-11-30
    Description: This work presents an extension of newly developed 3D finite elements to model failure in purely mechanical based materials [1, 2] to electromechanical coupled materials. Following the approach suggested in [6] for the plane setting, new finite elements are developed, which in addition to resolving strong discontinuities in the mechanical displacement field are capable of modeling strong discontinuities in 3D also in the electric potential. An application to a 3D off-centered three point bending test under combined mechanical and electrical loading outlines the performance of the newly developed finite elements. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Electronic ISSN: 1617-7061
    Topics: Mathematics , Physics , Technology
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  • 100
    Publication Date: 2013-11-30
    Description: A simulation model for damage evolution in slip bands under VHCF condition is presented. By use of a numerical method it is applied to a real simulated microstructure of AISI304. It considers orientations of slip systems as well as individual anisotropic elastic properties in each grain. The numerical method is the two-dimensional boundary element method which is based on two integral equations and implies fundamental solutions for anisotropic elastic solids. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Electronic ISSN: 1617-7061
    Topics: Mathematics , Physics , Technology
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