bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ein O(n) Verfahren mit Kontaktbedingungen zur Modellierung einer zweibeinigen Laufmaschine
Authors: Gattringer Hubert , Bremer Hartmut 
Published: December 2005

AbstractBei der dynamischen Modellierung von baumstrukturierten Mehrkörpersystemen (starr oder elastisch), wie das bei Laufmaschinen der Fall ist, entstehen hochdimensionale Bewegungsgleichungen. Der Rechenaufwand zur Invertierung der Massenmatrix und somit zur numerischen Lösung explodiert förmlich mit der kubischen Ordnung der Freiheitsgrade. Ausgehend von der Projektionsgleichung, einer synthetischen Methode zur Berechnung der Bewegungsgleichung, kann ein O(n) Verfahren hergeleitet werden. Dabei werden die Einzelkörper zu definierten Subsytemen (immer wiederkehrende Baugruppen) zusammengefasst, um das Problem geeignet zu strukturieren. Über die den Subsystemen zugeordneten beschreibenden Geschwindigkeiten erhält man gut interpretierbare Zwischenergebnisse. Die in dieser Arbeit vorgestellte zweibeinige Laufmaschine besteht aus 28 Starrkörpern , wobei jeweils 2 Körper (Motor und Arm) zu einem Subsystem zusammengefasst sind. Für die Berechnung der Beschleunigung müssen nur quadratische Matrizen vom Rang 2 (Anzahl der Relativfreiheitsgrade pro Subsystem) invertiert werden. Bei der Modellierung des Gehens werden Bindungen mit dem zweiten Fuß immer wieder geöffnet und geschlossen. Dies wird mithilfe einer Kontaktkraft (Lagrangescher Parameter) implementiert. Die Invertierung der Gesamtmassenmatrix kann für die Berechnung des Lagrangeschen Parameters mit einer Erweiterung des O(n) Verfahrens ebenfalls umgangen werden. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Unkontrollierbare Bewegungen ebener Mechanismen mit Gelenkspiel
Authors: Hofmeister Adolf , Sextro Walter , Röschel Otto 
Published: December 2005

AbstractIn dieser Arbeit wird ein analytisches Berechnungsverfahren vorgestellt, mit dem der gesamte Positions‐ und Orientierungsraum (ErrorWorkspace) ebener Mechanismen mit spielbehafteten Gelenken kinematisch beschrieben bzw. dargestellt werden kann. Für die Berechnung wird der gesamte Positions‐ und Orientierungsraum im Kinematischen Bildraum dargestellt, wobei auf besondere Merkmale eingegangen wird. Der ErrorWorkspace, der mit Hilfe des Berechnungsverfahren bestimmt wird, wird an einem Koppelgetriebe, an einem Filmgreifergetriebe und an einem Double‐rocker four‐bar mechanism mit Kurbelantrieb dargestellt und analysiert. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The discrete null space method for constrained mechanical systems in nonlinear structural and multibody dynamics
Authors: Leyendecker S. , Betsch P. , Steinmann P. 
Published: December 2005

AbstractCorresponding to d'Alemberts principle in classical mechanics, the discrete null space method developed in [1] provides an energy‐momentum conserving time stepping scheme for conservative finite‐dimensional dynamical systems subject to constraints. The elimination of the Lagrange multipliers from the temporal discrete system leads to a reduced number of unknowns and to an improved condition number during the iterative solution of the nonlinear system. External and internal constraints are fulfilled likewise at the time nodes, wherefore the discrete null space method is particularly suited for the treatment of elastic multibody systems in structural dynamics. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Troubleshooting in Studying the Behavior of Ballast Stones using Molecular Dynamic Simulation
Authors: Mircea Alina , Popp Karl 
Published: December 2005

AbstractFor the safety of the railways very important, beside tracks and trains, is the behavior of ballast stones. In the last years many scientists have started to investigate the behavior of the ballast stones and the parameters that influence them. In order to describe this behavior, one can choose a continuum mechanical description of the system or a discrete one. The problem with the first method is that the material parameter set depends on stone geometry, humidity and further factors. The second method (also called Molecular Dynamic Method MDS) makes possible a close‐to‐reality rendition of each ballast stone by means of numeric time step integration. We use MDS in order to built up a model for the system ballast stones ‐ track. Through our model we analyze small ballast stones range like under a magnifying glass. The ballast stones appear as polygons with a number of corners between 5 and 8, written in ellipses, and a size of 2 to maximally 6.3 cm. In the first step the model B70 has been selected for the track and the parameter of the model has been investigated. In the second step the program became more flexible and one can decide if the system consists from one track and ballast stones or from two tracks and ballast stones. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Studies Regarding the Development of Integrated Microgrippers Models Design Based on the PLM Systems
Authors: Pisla Adrian 
Published: December 2005

AbstractIn the paper are presented the tendencies, considerations and conclusions regarding the design, simulation, testing and development of some integrated microgripers, based or destined on the parallel kinematics by using the PLM concepts and a PLM system, in order to identify the most appropriate correlation between the factors that are leading to the final design and to the manufacturing process of the integrated microgripers. The paper is structured in three parts: introduction regarding the gripping systems tasks and evolution, the development of the applications in the miniaturization direction and the model and conclusions accomplished for the next developments. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New Algorithm for the Identification and Analysis of the Parallel Robots Singularities
Authors: Pisla Doina 
Published: December 2005

AbstractThe paper presents a new algorithm for the analysis of the kinematic singularities for different parallel structures using a testing stand. The derived expressions are used to superimpose graphical representations of the manipulators singularity and workspace. The analytical description of the singularity loci can be successfully used for the optimisation of the kinematic design. The derived algorithm for singularities analysis has been integrated in an already developed parallel robots simulation system, which provides an easy to read graphical representation of the singularities that enables their isolation within the working space and their avoiding in the path programming activity. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamisches Verhalten einer elektromechanisch betätigten Lamellenkupplung
Authors: Treder Marco , Woernle Christoph 
Published: December 2005

AbstractEine Alternative zur hydraulischen Betätigung automatisierter Fahrzeugkupplungen stellt die elektromechanische Betätigung dar. Ein Funktionsmuster eines elektromechanischen Kupplungsaktors besteht aus einem Stellmotor, einem Untersetzungsgetriebe und einerMechanik zur Realisierung der Betätigungskraft, die auf die Kupplungslamellen wirkt. Für die Simulation des dynamischen Kupplungsverhaltens wird ein detailliertes Mehrkörpermodell entwickelt, das Modelle des elektromechanischen Aktors und der nasslaufenden Lamellenkupplung enthält. Die Betätigung der Kupplung wird durch Vorgabe unterschiedlicher Zeitfunktionen des Moments des Stellmotors realisiert. Die Simulationsergebnisse werden mit Messergebnissen verglichen. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling and application of the self‐locking phenomenon in the context of a non‐discrete impact clutch
Authors: Welge‐Luessen Tobias , Glocker Christoph 
Published: December 2005

AbstractThis paper describes an application of the self locking phenomenon in order to realize a non‐discrete impact clutch. It is used to generate velocity jumps in an underactuated robot manipulator. Due to control reasons the impacts have to be made possible at arbitrary times, which calls for a non‐discrete device. Different design alternatives are listed and a numerical simulation as well as a possible mechanical design of the self‐locking mechanism are presented. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effective Dynamic Material Properties of Foam‐like Microstructures
Authors: Alvermann S. , Schanz M. 
Published: December 2005

AbstractThe effective material parameters of a microstructured material can be found using homogenization procedures based on calculations of a Representative Volume Element (RVE) of the material. In our approach the RVE is calculated in frequency domain and inertia is taken into account, leading to a frequency dependent behavior of the RVE.With the frequency response of the RVE, effective dynamic properties of the material are calculated using an optimization procedure. Due to the frequency dependent material behavior on the microscale a viscoelastic constitutive equation is applied on the macroscale. An example calculation is presented for an auxetic 2‐D foam‐like microstructure which is modelled as a plane frame structure. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Beanspruchungsgerechte Gestaltung bei Biegebelastung
Authors: Ertz M. 
Published: December 2005

AbstractBei der Entwicklung beanspruchungsgerechter Bauteile werden oft Verfahren zur numerischen Strukturoptimierung eingesetzt. Manche Ansätze auf diesem Gebiet gehen von einem Abbau hoher Spannungen durch gezielten Materialzuwachs an hoch beanspruchten Stellen aus. Bei Biegebelastung führt dieser Ansatz aber nicht immer zum Erfolg, weil ein Materialzuwachs hier unter Umständen sogar zu einer Erhöhung der lokalen Materialbeanspruchung führen kann. Am Beispiel eines einfachen Biegebalkens lässt sich dieses Problem anschaulich darstellen. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Conservation laws for a consistent plate theory
Authors: Kienzler Reinhold , Bose Dipak K. 
Published: December 2005

AbstractWithin the framework of a consistent second‐order plate theory, three material conservation laws are established, which are useful to describe the energy‐release rates and the material forces connected with the change of configuration of inhomogeneities or defects within the plate. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Buckling‐Bending Problem for Circular Plate
Authors: Marko Lubomir 
Published: December 2005

AbstractWe consider radially symmetric deformation of a thin flat elastic circular plate of constant thickness clamped at its edge. The plate is under the action of a uniform compressive thrust along its edge in the midplane of the plate. The thrust is proportional to a real parameter λ. The plate is also subjected to a radially symmetric load, normal to its midplane. The equilibrium states of the given buckling‐bending problem are the solutions of von Kármán equations. Let λ1 < λ2 be the first and the second eigenvalue of the linearized problem. If λ ≤ λ1 the buckling‐bending problem has unique solution for any normal load. If λ ∈ (λ1, λc), where λ1 < λc < λ2 the buckling‐bending problem has one or three solutions depending on the normal load. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asymptotic Analysis of Free‐Edge and Free‐Corner Effects in Laminate Structures
Authors: Mittelstedt Christian , Becker Wilfried 
Published: December 2005

AbstractStress fields in the vicinity of free edges and corners of composite laminates exhibit singular characteristics and may lead to premature interlaminar failure modes like delamination fracture. It is of practical interest to investigate the nature of the arising free‐edge and free‐corner stress singularities ‐ i.e. the singularity orders and modes ‐ closely. The present investigations are performed using the Boundary Finite Element Method (BFEM) which in essence is a fundamental‐solution‐less boundary element method employing standard finite element formulations. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Incompatibility Induced Nonlocal Crystal Plasticity
Authors: Becker Martin , Miehe Christian 
Published: December 2005

AbstractMotivated by the fact that locally inhomogeneous elastic or plastic deformations may result in incompatibilities of the fictitious intermediate configuration a strain gradient crystal plasticity model is developed. Thereby incompatibilities can be accounted for and scale dependent material behavior, as also observed experimentally, is predictable. A nonlocal extension of existing local formulations is proposed which does not require additional boundary conditions and thus maintains the classical BVP structure. On the numerical side key developments are an extended FE‐formulation for rate‐(in)dependent strain gradient plasticity and a local FE‐formulation which bases the gradient computation on an operator split combined with a smoothing algorithm. Comparative numerical studies for classical examples proove the superior efficiency of the second approach. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Local and extended models for high‐speed, dynamic loading of metals
Authors: Flatten Arnd , Svendsen Bob , Klingbeil Dietmar 
Published: December 2005

AbstractThe purpose of this work is to compare and contrast two different modeling approaches for high‐speed, dynamic loading of metals. A so‐called “local” model including hardening, strain‐rate hardening as well as temperature and ductile damage softening behaviour is extended by gradient plasticity. In particular, both models are compared in the context of their application to the modeling and simulation of dynamic shear‐banding in the alloy Inconel 718. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Instability prevention at the modeling of large elasto‐plastic strains under cyclic loading
Authors: Gorokhov M. Yu. , Semenov A. S. , Melnikov B. E. , Ulbricht V. 
Published: December 2005

AbstractThe cyclic instability phenomenon is investigated at the modeling of large elasto‐plastic strains. The possible causes of the cyclic instability and conditions ensuring cyclical stability of elasto‐plastic models are analyzed for the case of large strains. Among the possible causes of the cyclic instability the following are considered: the method of strain decomposition on elastic and plastic parts; the constitutive law for the elastic deformation (hypo‐ and hyper‐elasticity); the constitutive equation for the plastic deformation; the constitutive relation for the plastic spin; kinematic hardening law, in particular, the type of the objective rate in the generalized Prager's law. Predictions of 50 various models of the elasto‐plastic material have been compared in order to find the causes of the cyclic instability. Two test problems are considered: cyclic simple shear, combined cyclic simple shear and tension‐compression. Results of numerical experiments for the various material models are presented and discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Creep of Single Crystals – Modelling and Numerical Aspects
Authors: Vladimirov Ivaylo , Reese Stefanie , Eggeler Gunther 
Published: December 2005

AbstractA number of constitutive models, utilizing both microstructural and/or phenomenological considerations, have been developed for the simulation of the creep behaviour of nickel‐base single crystal superalloys at elevated temperatures. In this work, emphasis is placed on the rate‐dependent single crystal plasticity model [1]. A strategy for the identification of the material parameters of the model to fit the results from experiments has been implemented. The parameter fitting methodology rests upon a two‐membered evolution strategy. In addition, a proposal is made for the extension of the Cailletaud model [1] by means of an evolution equation for a damage variable which enables the modelling of the tertiary creep stage. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Hill's Bipotential
Authors: Ban M. , Vallée C. , Lerintiu C. 
Published: December 2005

AbstractA new formulation of the constitutive law of materials based on the concept of bipotential was introduced by de Saxcé. This concept is able to describe non‐associated laws and to suggest robust numerical algorithms. Materials that admit a bipotential to model their behaviour constitute the class of Implicit Standard Materials (ISM). This class contains, as a sub‐class, the Generalized Standard Materials (GSM). In this paper, we present a bipotential expressing the coaxiality of two tensors with preservation of the order of the eigenvalues. We call it Hill's bipotential. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Relaxation model of piezoelectric materials
Authors: Delibas B. , Arockiarajan A. , Seemann W. 
Published: December 2005

AbstractPolarization switching inside grains is time dependent. When external applied loading is not quasi‐static, macroscopic properties of piezoelectric materials changes with the rate of loading. In this paper, a 2‐D micromechanical model is proposed in order to simulate the rate dependent properties of certain perovskite type tetragonal piezoelectric materials based on linear constitutive, nonlinear domain switching, intergranular effects and kinetics models. The material is electrically loaded with an alternating voltage of various frequencies. For the onset of domain switching, energy equation is implemented. Propagation of the domain wall during domain switching in grains is modeled by means of exponential kinetics relation after domain nucleation. Mechanical strain butterfly loops under different frequencies (0.01Hz–1Hz) are simulated. The model gives important insights into the rate dependency of the piezoelectric materials that have been observed in some experiments reported in the literature. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of polycrystalline ferroelectrics based on discrete orientation distribution functions
Authors: Kurzhöfer Ingo , Schröder Jörg , Romanowski Holger 
Published: December 2005

AbstractFerroelectric materials exhibit a spontaneous polarization, which can be reversed by an applied electric field of sufficient magnitude. The resulting nonlinearities are expressed by characteristic dielectric and butterfly hysteresis loops. These effects are correlated to the structure of the crystal and especially to the axis of spontaneous polarization in case of single crystals. We start with a representative meso scale, where the domains consist of unit cells with equal spontaneous polarization. Each domain is modeled within a coordinate invariant formulation for an assumed transversely isotropic material as presented in [10], in this context see also [8]. In this investigation we obtain the macroscopic polycrystalline quantities via a simple homogenization procedure, where discrete orientation distribution functions are used to approximate the different domains. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A fluid mechanical model for granular flow in silos
Authors: Leppert Caroline , Dinkler Dieter 
Published: December 2005

AbstractGranular materials may display both solid and fluid like behaviour. For low densities and high strain rates as in avalanches or during the discharge of silos the behaviour is mainly governed by interparticle collisions. On the other hand, frictional contacts characterise the solid state which is represented within the framework of plasticity theory. A fluid like constitutive model describes granular materials when subjected to large deformations and high strain rates. It bases upon a modified viscoplastic model that is valid for both yielded and unyielded regions. The central idea is the distinction between fluid and solid regions by means of comparing actual shear stress and Coulomb yield stress. The application to the simultion of the discharge of silos shows the feasibility of the chosen method. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Aspects of the simulation of the ferroelectric hysteresis
Authors: Romanowski H. , Schröder J. 
Published: December 2005

AbstractIn this paper we present a thermodynamically consistent phenomenological model for an assumed transversely isotropic ferroelectric crystal. Such materials become spontaneously polarized within a certain range of temperature. On the macro scale a remanent polarization and remanent strains, due to the reorientation of the polarization vectors, are observed, if an electric field above the so‐called coercive field is applied. The goal of this work is to construct a thermodynamically consistent formulation of the electro‐mechanically coupled ceramic on a meso scale, that takes into account the orientation of the assumed transversely isotropic unit cell, see [4]. The anisotropic behavior is governed by isotropic tensor functions, which are formulated in terms of a finite set of invariants, see [3]. Considering a simple model problem we discuss the linearization of discrete weak forms, resulting from the electromechanical boundary value problem. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computation of Material Forces in Thermoplasticity Based on Alternative Smoothing Algorithms
Authors: Zimmermann Dominik , Miehe Christian 
Published: December 2005

AbstractDifferent approaches to the computation of material forces in inelastic structures are investigated. Dissipative effects in inelastic materials are described by internal variables. The formulation of balance equations in the material space requires the computation of gradients of these internal variables. The computational evaluation of these gradients in the context of finite element simulations needs a global representation of the internal variable fields. On the one side, this request can be carried out by a global formulation that discretizes the internal variable fields in terms of nodal degrees additional to the displacements. A numerically more effective approach applies smoothing algorithms which project the internal variables of a typical local formulation from the integration points onto the nodal points. In detail, the implementation of two smoothing algorithms for the computation of material forces is dicussed. The L2–projection necessiates the solution of a system of equations on the global level. A patch recovery yields a smoothed solution from an element patch surrounding the nodal point of interest. The performance of both algorithms is compared for the material force computation in finite thermoplasticity. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In‐situ pultrusion of urea‐formaldehyde matrix composites. II: Effect of processing variables on mechanical properties
Authors: Yen Chih‐Chao , Chen Chin‐Hsing , Lue Jun‐Yi 
Published: December 2005

AbstractUnidirectional fiber reinforced urea‐formaldehyde (UF) composites have been prepared by the pultrusion processes. The effects of the processing parameters on the mechanical properties (flexural strength and flexural modulus, etc.) of the glass fiber reinforced UF composites by pultrusion has been studied. The processing variables investigated included die temperature, pulling speed, postcure temperature and time, filler type and content, and glass fiber content. The die temperature was determined from differential scanning calorimetry (DSC) diagram, swelling ratio, and mechanical properties tests. It was found that the mechanical properties increased with increasing die temperature and glass fiber content, and with decreasing pulling rate. The die temperature, pulling speed, and glass fiber content were determined to be 220°C, 20–80 cm/min, and 60–75 vol%, respectively. The mechanical properties reached a maximum value at 10, 5, 5, and 3 phr filler content corresponding to the kaolin, talc, mica, and calcium carbonate, respectively, and then decreased. The mechanical properties increase at a suitable postcure temperature and time. Furthermore, the properties that decreased due to the degradation of composite materials for a long postcure time are discussed. POLYM. COMPOS., 27:8–14, 2006. © 2005 Society of Plastics Engineers