bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical simulation of electrical double layers and internal electrodes in microchannels
Authors: Wälter Bettina , Ehrhard Peter 
Published: March 2010

AbstractWe investigate the influence of flow field and electrode reactions onto an electrical double layer (EDL), which is located in the immediate vicinity of the walls of a rectangular microchannel. The precise knowledge of the EDL appears to be important for many technical applications in microchannels of small width, since the electrokinetic effects, as electroosmosis or electrophoresis, in such cases depend on the detailed charge distribution. Furthermore, the influence of internal electrodes onto the flow field is of interest. The mathematical model for the numerical treatment relies on a first‐principle description of the EDL and the electrical forces, caused by the electrical field between internal electrodes. Hence, the so‐called Debye‐Hueckel approximation is avoided. The simulations are time‐dependent and two‐dimensional (plane) in nature and employ a finite‐volume method. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Hybrid Micro–Macro–Model of Finite Plasticity with Discrete CODF–Textures
Authors: Frankenreiter Ilona , Rosato Daniele , Miehe Christian 
Published: March 2010

AbstractWe outline recent developments towards an efficient theoretical and algorithmic modeling of evolving crystal orientation microstructures in finite plasticity of polycrystals. We construct a framework for the description of grain texture induced anisotropy in planar polycrystals based on a hybrid micro‐macro modeling. On the macroscopic side this concerns a purely phenomenological setting of anisotropic finite plasticity based on evolving structural tensors accounting for the deformation‐induced macroscopic anisotropy. On the micro‐mechanical side, the macro‐model is linked with an accompanying microscopic plasticity model that accounts locally for microscopic structural changes in the form of grain re‐orientations. The model‐inherent scale bridging is accomplished by an evolving crystal orientation distribution function (CODF), which governs the evolution of the structural tensors. The evolution of the CODF is updated in a novel format based on the exploitation of two evolution equations in the Lagrangian setting. We discuss an efficient numerical implementation of evolving CODFs discretizing the orientation space. The new approach is compared with a Taylor model. The new model provides an efficient and fast computationally two‐scale approach for the prediction of the complex microstructures evolution in polycrystals. The capability of the proposed method is demonstrated by means of representative numerical examples. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of disk brake noise behavior via measurement of friction forces
Authors: Schlagner Stefan , von Wagner Utz 
Published: March 2010

AbstractSquealing of disk brakes is a major problem in the field of vehicle design. It is commonly acknowledged, that this squeal is initiated by instability due to friction forces between the pads and the disk, leading to self excited vibrations. This work addresses the mechanical work of these friction forces in order to draw conclusions for the investigation of the noise behavior of disk brakes. Therefore a multi degree of freedom model is used to compare its stability behavior with the frictional work at the pads. The results obtained are applied to experiments in which, on the one hand brake pads with integrated piezoceramic actuators cause a broad band excitation and, on the other hand, dynamic pad velocities/accelerations and friction forces are measured. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulations and Tests of Innovative Friction Laws in Brake Systems
Authors: Bode Kai Henning , Ostermeyer Georg‐Peter 
Published: March 2010

AbstractModeling of friction in mechanical systems is classically carried out by an incorporation of suitable algebraic functions. The general layout of these functions depends on the system under consideration [1]. For an analysis of brake systems, whose external parameters generally change rapidly, such steady state descriptions do not suffice. A detailed understanding of these systems and their dynamics requires innovative friction laws, which must be able to also capture transient effects in the contact zone. The tribological interface between brake lining material and brake disc is characterised by a closed‐loop interaction between heat, wear and friction, which causes a continuous growth and destruction of smooth and hard surface structures [2]. This equilibrium of flow can be well reproduced by modern automata methods [3]. It is significantly influenced by external load parameters, such as normal force and sliding velocity, which modulate the life cycle and average size of the contact patches and by that the coefficient of friction over time. Based on this principal mechanism, a new mathematical description of friction has been derived, which uses a set of coupled differential equations. This layout gives insights into the third body dynamics during transient friction events. Therewith, predictions of the surface topography, heat distribution and friction characteristics of different brake lining compositions become possible. The performance of the developed model will be illustrated by a discussion of specific braking events, extracted from industrial testing procedures (AK‐Master test). (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Temporal Regularity of Solutions of Rate‐independent Damage Processes
Authors: Thomas Marita 
Published: March 2010

AbstractThis contribution deals with the temporal regularity of energetic solutions of rate‐independent processes describing the partial, isotropic damage of physically nonlinearly elastic solids. In general, energetic solutions may have jumps. Here we discuss settings that lead to continuity, Hölder‐ or Lipschitz‐continuity in time and we give examples on suitable energy densities. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental investigation of ovine intervertebral disc units in longitudinal loading
Authors: Helfenstein Jörg , Hollenstein Marc , Papes Ondrej , Mazza Edoardo 
Published: March 2010

AbstractThe assessment of the predictive power of material models for soft biological tissues is an important issue when it comes to realistic simulations for medical applications. The determination of the model parameters needs sound experimental data. In our case we want to test the viscoelastic properties of ovine lumbar intervertebral discs (IVD's) in longitudinal loading. The complex geometry as well as the small imposed displacements combined with rather high forces are to be treated. The two vertebrae adjacent to the IVD are mounted using custom made clampings where attention is paid not to prestress the tissue. First tests were done with steel springs in order to check the suitability of the used materials testing machine. No significant compliance of the machine could be detected but a negative hysteresis that might origin from the data acquisition process. Experiments on IVD's gave us an in‐depth insight into the underlying mechanics such that we can now define appropriate protocols for future experiments. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Intraoperative mechanical characterization of human liver
Authors: Hollenstein Marc , Jabareen Mahmood , Breitenstein Stefan , Riener Marc‐Oliver , Clavien Pierre‐Alain , Bajka Michael , Mazza Edoardo 
Published: March 2010

AbstractThe tissue aspiration experiment, the instrumentation for intraoperative measurements and the procedure for quantitative evaluation of the measurement results are presented. This experiment is currently used in a clinical study on the correlation between the mechanical properties of liver tissue and its histopathologic state. To date the liver of 25 patients has been tested. The results indicate a difference of 40% in the initial stiffness between peritumoral normal liver tissue and liver tumor. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental and numerical study of the relaxation behavior of facial soft tissue
Authors: Barbarino Giuseppe. G. , Jabareen Mahmood , Mazza Edoardo 
Published: March 2010

AbstractChallenges in computational simulation of the mechanical behavior of soft tissues and organs for clinical applications are related to the reliability of the models with respect to the anatomy, the mechanical interactions between different tissues, and the non linear (time dependent) force deformation characteristics of soft biological materials. In this paper a 3D finite element model of the face and neck, which has applications in surgical devices optimization and surgery planning, is presented. Bones, muscles, skin, fat, and superficial muscoloaponeurotic system (SMAS) were reconstructed from magnetic resonance images and their shape, constraints and interactions have been modeled according to anatomical, plastic and reconstructive surgery literature. Non linear time dependent constitutive equations are implemented in the numerical model, based on the Rubin‐Bodner model. For the present calculations a simplified hyperelastic formulation has been used. The corresponding model parameters were selected according to previous work with mechanical measurements ex vivo on facial soft tissue. For determination of model parameters, in particular the ones corresponding to the time dependent behavior, an instrument for measuring the relaxation behavior of the face tissue in vivo was developed. The experimental set‐up is described and results are presented for tests performed on different locations of the face (jaw, mid‐face, parotid regions) and neck. The measured “long term” reaction force of the facial soft tissue is compared to numerical results. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wave propagation in the soil due to a falling chimney
Authors: Bochert Jana 
Published: March 2010

AbstractThis paper describes a simulation of wave propagation in the soil as a result of an impact. In this specific case, the dynamic load is the velocity of a falling chimney. The impacting parts of the chimney transfer their dynamic forces to the adjacent continuum. This causes vibrations in the surrounding area. In this paper, measurements of velocities in the soil caused by a falling chimney are compared with numerical solutions using a two‐dimensional FEM‐SBFEM model. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Scaled boundary finite element analysis of stress singularities in piezoelectric multi‐material systems
Authors: Mayland Wibke , Becker Wilfried 
Published: March 2010

AbstractThe scaled boundary finite element method (SBFEM) in an extension for piezoelectric materials is used to analyze twoand three‐dimensional stress singularities in piezoelectric multi‐material systems. It is found to be an efficient tool for the analysis of singularity orders of such situations, that turn out to be rather complex. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of High‐Speed Ball Bearings with MSC/ADAMS
Authors: Fritz Felix , Basler Alexander , Seemann Wolfgang 
Published: March 2010

AbstractHigh‐speed‐rotors can be supported by angular ball bearings. Therefore, the nonlinear, time‐variant bearing reaction forces are modeled for high revolution rates in this approach. Assuming local deformations, bearing stiffness is modeled with Hertzian contact between balls and races. Centrifugal forces on balls and rings are considered. Under consideration of clearance ratio the contact angle changes due to bearing load, rotational frequency and tilting angle of the inner ring. Since the contact angle determines the direction of reaction force and moment, it is possible to analyze the non‐planar inner ring movement. To be able to attach further machinery parts easily to the bearing model, this approach has been done with the multi‐body simulation software package MSC/ADAMS. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐linearity of multibody dynamic equations with respect to Lagrange multipliers: application to railway dynamics
Authors: Fisette Paul , Lipinski Krzysztof , Samin Jean‐Claude 
Published: March 2010

AbstractIn this paper, the dynamics of multibody systems with closed kinematical chains of bodies is considered. The main focus is set on non‐linearity of the multibody equations with respect to the Lagrange multipliers. When closed chains are considered, loop cutting procedure is a solution to express the constraint equations associated with the loops. Dynamic equations of the multibody tree‐like structure are thus completed with the constraint forces via the Lagrange multipliers. In the considered case of railway vehicles, constraints arise from the contact between the rigid wheels and the rails. Corresponding contact forces applied to the wheels appears via the Lagrange multipliers λ and the tangent creep forces as well. Resulting differential‐algebraic equations can be transformed into an ODE system and then time‐integrated using the coordinate partitioning method [3], when the system is linear with respect to λ. This paper presents an algorithm allowing us to solve this system in case of nonlinearities with respect to λ, which is typical of wheel/rail contact force models. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Holistic Simulation Approach from a Measured Load to Element Stress Using Combined Multi‐body Simulation and Finite Element Modelling
Authors: Harter Matthias , Beitelschmidt Michael 
Published: March 2010

AbstractThe design of vehicle bodies requires the knowledge of the vehicle's structural response to external loads and disturbances. In rigid multi‐body simulation the dynamic behaviour of complex systems is calculated with rigid bodies and neglect of body elasticity. On the other hand, in finite element models large degree of freedom numbers are used to represent the elastic properties of a single body. Both simulation methods can be combined, if the finite element model size is reduced to a degree of freedom number feasible to multi‐body simulation. The application to practical purposes requires the use and interconnection of several different software tools. In this contribution a holistic method is presented, which starts with the measurement or synthesis of loads and excitations, continues with the integration of a reduced finite element model into a multi‐body system, the dynamic response calculation of this combined model, and concludes with the result expansion to the full finite element model for calculating strain and stress values at any point of the finite element mesh. The applied software tools are Simpack, Nastran, and Matlab. An example is given with a railway vehicle simulated on measured track geometry. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Studies on Bone Remodeling Theory Based on Microcracks Using Finite Element Computations
Authors: Kardas Dieter , Nackenhorst Udo 
Published: March 2010

AbstractThe investigation of the microcrack theory supports the research work of understanding the microstructural behaviour of physiological loaded bones. Microcracks in cortical bone are assumed to have a stimulatory effect on osteocytes – the sensor cells for the bone remodeling process. In this contribution an approch to simulate microcrack initiation and propagation inside a 3D anisotropic and inhomogenious FEA model of cortical bone tissue will be shown. The numerical formulations are based on computational continuum damage mechanics. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An efficient quantitative ultrasonic elastography based on variational mesh refinement
Authors: Arnold Alexander , Bruhns Otto T. , Mosler Jörn 
Published: March 2010

AbstractPalpation is often utilised in medicine to detect pathological changes in soft tissue such as those associated with breast cancer or prostate tumor. Ultrasound elastography can be used to measure the stiffness in regions deeper than those reachable by palpation. Conceptually, ultrasound echo signals are measured before and after a defined compression. A displacement field can be calculated with these signals and subsequently, the stiffness distribution can be determined using quantitative elastography. In this regard, the difference between measured und estimated displacement fields is minimised (inverse problem). The region of interest is discretised using the finite element method. In order to reduce the resulting numerical costs and to improve the accuracy of the method, a variational mesh refinement combined with a clustering technique known from digital image compression is elaborated and presented. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electromechanics of Cardiac Tissue: A Unified Approach to the Fully Coupled Excitation‐Contraction Problem
Authors: Göktepe Serdar , Kuhl Ellen 
Published: March 2010

AbstractThis contribution is concerned with a new, unified finite element approach to the fully coupled problem of cardiac electromechanics. In contrast to the existing numerical approaches suggested in the literature; to the best of our knowledge, for the first time, we propose a fully implicit, purely finite‐element‐based approach to the coupled problem. The system of coupled algebraic equations obtained by simultaneous linearization of non‐linear weighted residual terms is solved monolithically. The put forward modular algorithmic framework leads to an unconditionally stable and geometrically flexible structure that can readily be extended towards complex ionic models of cardiac electrophysiology. The performance of the proposed approach is illustrated by the coupled electromechanical analysis of a biventricular generic heart model. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An anisotropic viscoelastic model for collagenous soft tissues at large strains – Computational aspects
Authors: Ehret Alexander E. , Itskov Mikhail , Weinhold Georg W. 
Published: March 2010

AbstractThis paper focusses on computational aspects related to a recently proposed anisotropic viscoelastic model for soft biological tissues at large strains [1]. A key aspect of this model is the generalisation of micromechanically motivated one‐dimensional constitutive equations to three dimensions by numerical integration over the unit sphere. A strong effect of this procedure on the accuracy and in particular on the material symmetry of the model is observed. Finally a finite element example of an artery subject to normotensive blood pressure is presented. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Dynamic Analysis of the Flow Process Through the Aortic Valve Leaflet Model
Authors: Konderla Piotr , Krzysztof Patralski 
Published: March 2010

AbstractThe object under study is an aortic valve, located in the aortic annulus. The aortic valve leaflet has been assumed to be a three‐dimensional object. The computations were performed using the Ansys CFX system. The result of our analysis takes the form of a model describing the interaction between two domains. The opening of the aortic valve model was obtained by iteration process. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of Feasible Muscle Forces in Human Walking Using Static Optimization and Hill's Muscle Dynamics Constraints
Authors: Ou Ye , Kecskeméthy Andrés 
Published: March 2010

AbstractStatic optimization is a widely used technique for solving the redundant problem of muscle‐force determination for given inverse dynamics. There are different cost functions, such as minimal metabolic energy, minimal forces, minimal fatigue, which lead to different results. One problem in this setting is that the resulting time histories of the ensuing equilibrium forces may not be feasible with respect to the muscle dynamics, i.e., the resulting force gradients at the muscle cannot be reproduced by the dynamics of the corresponding muscle. In this paper, a combined method is presented which takes into account the limitations induced by the muscle dynamics by applying static optimization techniques at each time step and prescribing minimal and maximal constraints for the forces by extrapolating the force values from previous steps using feasible muscle activation values. Thus, both the advantages of fast static optimization and the guarantee of feasible time histories of the muscle forces can be achieved. Moreover, joint forces turn out to be 20–40% higher in swing phase than those predicted with classical static optimization. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Real‐time FEM for the Virtual Surgery of Soft Tissues
Authors: Willberg Christian , Gabbert Ulrich , Berger Harald 
Published: March 2010

AbstractThe virtual surgery of soft tissues, such as the virtual laparoscopy, requires realistic 3D models of all the inner organs belonging to the virtual scenario, which in connection with fast numerical algorithms have to assure the real‐time performance of the simulation. The simulation has to take into account the interaction of the surgical instruments with the organs, the contact behavior between the organs including self contact as well as cutting, stitching, bleeding, coagulation etc. Recently, different approaches have been published to achieve a real time performance with sufficient accuracy. In the paper a finite element approach is presented, which includes the geometrical and physical nonlinear dynamic behavior of the organs during the surgery as well as the required contact conditions between the organs and the organs with surgical instruments. Some simplifications of the standard procedure (contact search, updating rate, etc.) to increase the computational speed as well as the beneficial behavior of an implicit time integration scheme resulting in larger time steps are discussed. In the paper some examples are presented to demonstrate the performance and the accuracy of the approach. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Design of the exoskeleton as a rehabilitation system
Authors: Tuliński J. , Jasińska‐Choromańska D. 
Published: March 2010

AbstractThe presented paper concerns development of a parallel kinematic structure of a palm fingers exoskeleton as a prospective solution for common design difficulties encountered in typical serial‐kinematics exoskeletons for the fingers rehabilitation. The performed state of the art review showed that in spite of over 40 years of development of exoskeletons, considered to be particularly useful as programmable medical devices, there is not achieved the acceptable level of safety and usability. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Free vibration of sandwich plates with impact‐induced damage
Authors: Burlayenko Vyacheslav N. , Sadowski Tomasz 
Published: March 2010

AbstractFree vibrations of impact‐damaged sandwich plates with honeycomb and foam cores are studied. It is assumed that damages caused by impact events are to exist before the vibration start and to be constant during oscillations. The influence of the impact damage modes involving the core crushing (planar damage), face sheets fracture (indentation) and the core to face sheets interface degradation (debonding) on the natural frequencies and associated mode shapes of the sandwich plates was investigated using commercially available finite element code ABAQUS. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)