bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reibleistendämpfung in Leichtbaustrukturen
Authors: Kröger Matthias , Reckmann Hanno , Popp Karl , Romberg Oliver 
Published: June 2004

AbstractDie Erhöhung der Dämpfung in Leichtbaustrukturen ist immer dann sinnvoll, wenn die dynamischen Beanspruchungen durch Schwingungen dominant sind. Dann kann durch Reibleistendämpfer die Schwingungsamplitude und dadurch die Gesamtmasse reduziert werden. Die analytische Vorauslegung von Reibleisten wird an einem Seitenleitwerk aufgezeigt. Die berechneten und optimierten Dämpfungsgrade lassen sich durch experimentellen Untersuchungen bestätigen. Insgesamt zeigte sich ein großes Potential für den Einsatz von Reibleisten zur Dämpfungserhöhung.
Investigation of Parametric Resonance in Tuned Liquid Column Dampers
Authors: Reiterer Michael , Hochrainer Markus 
Published: June 2004

AbstractTuned liquid column dampers (TLCDs) are innovative vibration absorbing devices in the low frequency range, which have been studied extensively in the last decade. Most research work focuses on the suppression of horizontal motions of structures, but there is still a demand to investigate the influence of vertical motions on the damping behavior of TLCD, especially if the absorber is attached to earthquake excited buildings or long span bridges. When considering vertical motions the TLCD dynamics becomes nonlinear and quite sensitive to parametric resonance. Consequently an unstable system might be obtained, which is dangerous for the main structure. Hence, a small‐scale model of a TLCD under both, horizontal and vertical excitation has been developed and analyzed numerically and experimentally. For this sake, a small‐scale testing facility has been constructed to perform these experimental investigations. Samples of free and electro‐dynamically forced vibration experiments with different TLCD configurations and excitation scheme has been performed. The experimental results turned out in good agreement with the theoretical predictions of the computer model and both, theoretical and experimental studies indicate that the vertical motion of a structure should be considered carefully since in case of parametric resonance it might dominate the overall dynamic behavior of TLCDs.
Computation of the Temperature between Brake Disk and Pad
Authors: Rudolph M. , Popp K. , Hogenkamp W. 
Published: June 2004

AbstractThe authors present a computation method which is based on an analytical approach describing the temperature distribution due to a moving heat source. This approach has been adapted to the technical problem of the diskpad contact and programmed in MATLAB. In particular, the inhomogeneous pressure distribution in the contact plane has been taken into account. Further, FE‐calculations have been conducted to ascertain the correctness of the analytical approximation. By this combination of analytical and numerical methods an efficient calculation of the contact temperature became possible which is by far faster than corresponding FE‐calculations. The results have been confirmed by measurements using a brake test rig and an IR‐camera system.
On Some Property of the Natural Frequencies of Elastic Chains
Authors: Strobach Daniel , Braun Manfred 
Published: June 2004

AbstractIn this paper we consider plane oscillations of a chain consisting of an elastic spring with concentrated mass points attached to it. It is shown that the sum of squared reciprocal natural frequencies does not depend on the number and distribution of the attached masses. For an arbitrary chain, an equivalent simple oscillator with one or two degrees of freedom can be constructed having the same sum of squared reciprocal natural frequencies as the original chain. Results are also specialized to regular chains with equal masses at equidistant spacing.
Dynamic Shape Control of a Flying Cantilever by Piezoelectric Actuation
Authors: Zehetner Ch. , Irschik H. 
Published: June 2004

AbstractThe present contribution is concerned with active suppression of plane flexural vibrations of a cantilevered panel. The vibrations of the panel are produced by imposed forces and by a prescribed large rigid‐body motion of the cantilevered end, such that the panel appears to fly with respect to an inertial frame. The rigid body motion defines a floating reference configuration of the panel. With respect to the latter, the vibrations are assumed to remain in the elastic regime and to be moderately large. The cantilever is considered to be equipped with integrated piezoelectric actuators. It is the scope of the present paper to derive a spatial shape of these actuators such that the vibrations can be completely suppressed by the piezoelectric actuation. This inverse problem is exactly solved in the context of an equivalent single‐layer Kirchhoff‐theory for thin panels rigid in shear. Coupling to the electric field is taken into account. The presented solution of the shape‐control problem is intended to serve as a benchmark test for the field of intelligent wings. For comparison sake, 3‐dimensional Finite Element computations are performed.
Analysis and Active Rejection of Chatter in Rolling Mills
Authors: Holl Johann , Schlacher Kurt , Keintzel Georg , Eisenköck Norman 
Published: June 2004

AbstractThis contribution is concerned with a vibration phenomenon in multistand rolling mills called (third octave) chatter. In order to analyse the dynamical system, which is nonlinear in nature, a mathematical lumped parameter model of the plant is presented. This model comprises the mill stands, the strip as a coupling element of neighbouring mill stands and the hydraulic actuators. By means of the mathematical model of the coupled system the third octave chatter can be explained by an instability of the dynamic system. For the purpose of an active vibration rejection a nonlinear controller based on the PCH structure of the hydraulic system is designed.
Elasto‐plastic deformation in a spherical pendulum
Authors: Dibold M. , Gerstmayr J. , Irschik H. 
Published: June 2004

AbstractHeavily loaded deformable structures performing rigid body motions may exhibit elastic as well as plastic strains, particularly when the elastic stiffness and the yield stress are considerably lowered by catastrophic environmental influences. The dynamic equations are derived from the Newton‐Euler equations. Plastic strains are included by an additive split of the total strains. Exemplarily we study the movement of a spherical pendulum.
Rekursive Lösung der Bewegungsgleichung von elastischen Mehrkörperketten
Authors: Ferrara Paolo , Bremer Hartmut 
Published: June 2004

AbstractRoboterarme, Manipulatoren, Konstruktionswerkzeuge sind derzeit auf hohe Genauigkeit und Schnelligkeit optimiert. Diesen Anforderungen entsprechend sind deren Arme und Getriebe steif und unnachgiebig gebaut. Dies ist mit hohem Eigengewicht verbunden. Dort wo Gewichteinsparung, Leichtbau oder auch Kosteneinsparungen an Bedeutung gewinnen, werden starre Elemente durch nachgiebige ersetzt werden müssen. Die Nachgiebigkeit ist dabei nicht nur von Nachteil. Nachgiebige Elemente sind z.B. geradezu prädestiniert für hybride Antriebe, wo Position und Kraft gleichzeitig geregelt werden. Auch Laufmaschinen, die meist der Natur nachempfunden sind, könnten mit nachgiebigen Beinen natürlicher, leichter und flexibler gebaut werden. Die Schwierigkeiten der Handhabung elastischer Mehrkörper liegen darin, dass sich, durch die auftretenden Verformungen, das Verhalten des elastischen Systems gegenüber dem starren drastisch ändert. Bauteilverformungen pflanzen sich von Element zu Element fort. Der Versuch, einzelne Kettenglieder als elastische Balken zu beschreiben und diese modular zu einem System zusammenzufügen, soll die Komplexität der Beschreibung verringern und die Interpretation sowie die messtechnische Kontrolle einzelner Terme erleichtern.
A 3D Finite Element Solver for Multibody Systems Based on Implicit Runge‐Kutta Schemes
Authors: Gerstmayr J. , Schöberl J. 
Published: June 2004

AbstractAn efficient finite element (FE) formulation and a time‐integration scheme for the simulation of multibody systems are derived. The absolute nodal coordinate formulation is chosen. In the discretized form, a constant mass matrix and a nonlinear stiffness matrix follow from a variational formulation. According to the classical assumptions of multibody systems, only small deformations but large rotations are taken into account. A special decomposition of the Green strain tensor leads to a stiffness matrix which is multiplicatively composed of the rotation matrix of the rigid body rotation and the small strain stiffness matrix, which has to be computed only once. Thus, Runge Kutta schemes of higher order accuracy can be solved efficiently.
Generic Inverse Kinematics Approach for Robotics Applications
Authors: Krenn R. , Schäfer B. 
Published: June 2004

AbstractThe concept of DLR's new light‐weight robot generation is a modular one. It offers an almost infinite number of kinematics configurations. For pre‐simulations a virtual assembly and modeling tool was developed that supports online simulations using commercial multi‐body simulation software. Here, a key feature is the generic implementation of the inverse kinematics in order to deal with arbitrary kinematics. The paper addresses a method that combines the advantages of two basic algorithms and that can be easily implemented in MBS software.
Modellierung und Regelung baumstrukturierter, hybrider Mehrkörpersysteme
Authors: Mitterhuber R. , Bremer H. 
Published: June 2004

AbstractEs wird eine Modellbildungs‐ und Regelungsstrategie von kettenförmigen, teils elastischen Mehrkörpersystemen am Beispiel von zwei Knickarmrobotern mit je sechs Gelenken vorgestellt. Während der eine Roboter eine Standard‐ Industriemaschine ist, besitzt der zweite so schlanke Arme, dass deren Elastizität nicht vernachlässigt werden kann. Die Roboter fahren eine vorgegebene Trajektorie, wobei ihre Ende.ektoren miteinander im Kontakt stehen.
Spatial Tracks in Multibody Simulation. Theory and Simple Roller Coaster Example
Authors: Schott K. , Tobolář J. 
Published: June 2004

AbstractA calculation method for spatial tracks has been developed which is based on the numerical solution of the Frenet equations for spatial curves. The spatial track can be used in multibody simulations of vehicle dynamics. As an application example of this method a simple roller coaster model has been generated. The results are reasonable and show that multibody simulations are suitable to evaluate the vehicle dynamics of a roller coaster ride.
Numerik viskoelastischer Stoffgesetze mit fraktionalen Zeitableitungen
Authors: Aschenbrenner Lars , Dinkler Dieter 
Published: June 2004

AbstractZur Beschreibung des viskoelastischen Werkstoffverhaltens eignen sich Werkstoffgesetze mit gebrochenen Zeitableitungen, da sie das Materialverhalten auch über große Frequenzbereiche mit wenigen Materialparametern zutreffend wiedergegeben. Mit dem hier verwendeten Exponentialalgorithmus mit inneren Variablen gelingt es, den numerischen Aufwand auch gegenüber einer laufzeitoptimierten Entwicklung der Grünwaldreihe zu reduzieren und gleichwertige Ergebnisse zu erhalten.
On sensitivity investigations of thin‐walled shell structures using transient finite element analysis and finite perturbations
Authors: Ewert E. , Schweizerhof K. 
Published: June 2004

AbstractIn standard stability investigations of structures applying the finite element method usually the bifurcation and snapthrough points are detected. For practical design purposes not only the equilibrium state itself is significant but also the safety of the stable equilibrium state. The sensitivity, which quantifies the safety, can be investigated by introducing finite perturbations at a certain load level and considering the perturbed motion. In this contribution the application of Liapunov Characteristic Exponents (LCE) for the judgement of the perturbed motion is investigated.
An Anisotropic Porous Media Model of the Intervertebral Disc
Authors: Karajan Nils , Ehlers Wolfgang , Markert Bernd 
Published: June 2004

AbstractOn the microscale, the human intervertebral disc is a complex arrangement of mostly water, collagen (arranged in fibre bundles), proteoglycans and proteins. Attempting to separately describe each component would yield a too elaborated model, even by todays computing power. Therefore, an appropriate macro model needs to be developed. This can be done by splitting the disc into two distinct regions, which are a gelatinous core (nucleus pulposus) surrounded by a pliant, fibrous composite tissue (annulus .brosus). The nucleus may be considered as an isotropic material, whereas anisotropic effects have to be included for the annulus. This is due to the present fibres, which are not arranged in ideal chaos, but are assumed to be helically arranged yielding a locally orthotropic material.
Viskoelastizität von Elastomeren bei großen Deformationen
Authors: Zecha Holger , Lee Seokho , Miehe Christian 
Published: June 2004

AbstractDer Beitrag befasst sich mit der Darstellung eines Materialmodells zur Beschreibung der viskoelastischen Eigenschaften von Elastomeren bei großen dreidimensionalen Deformationen. Auf der Basis neuer Versuchsergebnisse erfolgt (i) eine geeignete Spezifizierung der in dem Modell auftretenden konstitutiven Funktionen und (ii) die Anwendung eines diskreten Relaxationsspektrums zur Erfassung des viskoelastischen Verhaltens. Numerische Simulationen werden mit ein– und mehrachsigen experimentellen Daten verglichen.
Stability Problems of Micro‐to‐Macro Transitions in Finite Plasticity
Authors: Becker Martin , Miehe Christian 
Published: June 2004

AbstractStability problems on the micro‐scale have a substantial influence on the macroscopic material behavior. For example micro‐instabilities such as the buckling of stiff fibers of a micro‐heterogeneous material result in a considerable softening of the macroscopic behavior. Instability phenomena of this kind lead to the problem of non‐convex homogenization where the size of the representative volume element has to be determined. These problems as well as the interaction between micro‐ and macro‐instabilities are examined within an incremental variational formulation of inelasticity.
Numerical Investigations on the Plastic Memory Effect of PTFE Compounds
Authors: Kletschkowski Thomas , Schomburg Uwe , Bertram Albrecht 
Published: June 2004

AbstractTo describe the nonlinear material behaviour of thermoplastic materials via the example of Polytetrafluorethylene (PTFE), a viscoplastic material model of overstress type is proposed. The approach is motivated by a rheological model, consisting of a rate‐independent elastoplastic element with an endochronic flow rule and a nonlinear elastic element in parallel connection with a nonlinear Maxwell model. For the generalization to three dimensions, the theory of finite viscoplasticity based on material isomorphisms is applied. To describe the non‐isothermal plastic memory effect, thermally induced plastic strains and a scalar back stress (inside the equilibrium branch) are taken into account.
Application of the Dunford‐Taylor Integral to Isotropic Tensor Functions
Authors: Itskov M. 
Published: June 2004

AbstractIn the present contribution closed‐form representations for isotropic tensor functions and their derivative are formulated using the Dunford‐Taylor integral. These representations are given in terms of eigenvalues of the tensor argument and are valid for all second‐order tensors defined as a linear mapping over the n‐dimensional real vector space. The solution obtained is especially useful for non‐symmetric tensor functions where representations based on the spectral decomposition in diagonal form cannot generally be applied.
Application of Relaxation Techniques to Nonconvex Isotropic Damage Model
Authors: Gürses Ercan , Lambrecht Matthias , NaMiehechname Christian 
Published: June 2004

AbstractA new energy relaxation technique for nonconvex inelasticity is applied to an isotropic damage model. The increasing damage yields nonconvex incremental potentials indicating the instability of the material and the development of finescale microstructures. The microstructures are resolved as first‐order laminates by convexifiaction techniques.
Static and extending interface cracks with contact zones in anisotropic as well as in piezoelectric bimaterials
Authors: Herrmann Klaus , Loboda Volodymyr 
Published: June 2004

AbstractAn interface crack with an electrically permeable and mechanically frictionless contact zone in a piezoelectric bimaterial under the action of a remote mixed mode mechanical loading as well as thermal and electrical fields is considered in the first part of this paper. By use of the matrix‐vector representations of thermal, mechanical and electrical fields via sectionally‐holomorphic functions the problems of linear relationships are formulated and solved exactly both for an electrically permeable and an electrically impermeable interface crack. For these cases the transcendental equations and clear analytical formulas are derived for the determination of the contact zone lengths and the associated fracture mechanical parameters.A plane strain problem for a crack with a frictionless contact zone at the leading crack tip extending stationary along an interface of two semi‐infinite anisotropic spaces with a subsonic speed under the action of various loading is considered in the second part of this paper. By introducing of a moving coordinate system connected with the crack tip and by using the formal similarity of static and propagating crack problems the combined Dirichlet‐Riemann boundary value problem is formulated and solved exactly for this case as well and a transcendental equation is obtained for the determination of the real contact zone length. It is found that the increase of the crack speed leads to an increase of the real contact zone length and the correspondent stress intensity factors which increase significantly for a quasi‐Rayleigh wave speed.
On the application of a slip‐based interface model for textile reinforced concrete
Authors: Richter Mike , Lepenies Ingolf , Zastrau Bernd W. 
Published: June 2004

AbstractThe macroscopic material properties of textile reinforced concrete (TRC) are essentially a.ected by the bond behavior between the fiber reinforcement and the surrounding matrix. If the brittle matrix is cracked the successive debonding of the fibers can be assumed to be the main reason for the high ductility of TRC. Based on pullout tests a slip based analytically treatable interface model with a piecewise linear shear stress – slip relation and numerically solvable models are developed.
Local and non‐local ductile damage and failure modelling at large deformation with applications to engineering
Authors: Svendsen Bob , Reusch Frederik , Klingbeil Dietmar 
Published: June 2004

AbstractThe numerical analysis of ductile damage and failure in engineering materials is often based on the micromechanical model of Gurson [1]. Numerical studies in the context of the finite‐element method demonstrate that, as with other such types of local damage models, the numerical simulation of the initiation and propagation of damage zones is strongly mesh‐dependent and thus unreliable. The numerical problems concern the global load‐displacement response as well as the onset, size and orientation of damage zones. From a mathematical point of view, this problem is caused by the loss of ellipticity of the set of partial di.erential equations determining the (rate of) deformation field. One possible way to overcome these problems with and shortcomings of the local modelling is the application of so‐called non‐local damage models. In particular, these are based on the introduction of a gradient type evolution equation of the damage variable regarding the spatial distribution of damage. In this work, we investigate the (material) stability behaviour of local Gurson‐based damage modelling and a gradient‐extension of this modelling at large deformation in order to be able to model the width and other physical aspects of the localization of the damage and failure process in metallic materials.
A Finite Interface Crack Interacting With A Subinterface Crack In Metal/Piezoelectric Ceramic Bimaterial
Authors: Tian Wen‐Ye , Gabbert Ulrich 
Published: June 2004

AbstractThe “pseudo‐traction‐electric‐displacement’ method was adopted to solve the interaction problem between a finite interface crack and a subinterface crack in metal/piezoelectric bimaterial. After deriving the fundamental solutions for a finite interface crack and a special subinterface crack respectively loaded by the normal and tangential concentrated tractions and the concentrated electric displacement, the present interaction problem was reduced to a system of integral equations, which may be solved numerically. The crack tip mode I stress intensity factor was calculated and detailed comparisons of the results derived under the compound mechanical‐electric loading conditions and those derived under the purely mechanical loading condition are performed.
Dynamical Calculation of Plane Frameworks using Boundary Integral Equations
Authors: Alvermann Steffen , Schanz Martin , Antes Heinz 
Published: June 2004

AbstractThe beam bending problem according to Timoshenkos theory can be solved using the Finite Element method. Here, the Boundary Integral Method is applied to the bending problem in frequency domain, providing an analytical solution for beams and systems of beams like trusses. An example is presented to demonstrate the method.
Homogenisierungsbasierte Mehrgitter‐Transferoperatoren für nichtlineare heterogene Materialien
Authors: Bayreuther C.G. , Miehe C. 
Published: June 2004

AbstractMehrgitterverfahren ermöglichen eine effiziente Lösung großer Gleichungssysteme, die bei Finite Element‐Diskretisierungen nichtlinearer Randwertprobleme auftreten können. Bei heterogenen Materialien bedingt der Einsatz solcher Löser die Konstruktion spezieller Transferoperatoren. Diese Aufgabe wird mit Hilfe von Homogenisierungstechniken gelöst. Die neuen Strategien werden anhand repräsentativer Modellprobleme mit bekannten Verfahren verglichen.
Optimization of Microstructures by Evolution Strategies
Authors: Bohn Niels , Gabbert Ulrich 
Published: June 2004

AbstractEvolution strategies can be classified as a type of direct methods, requiring only information about the objective function. Contrary to analytical methods, the calculation of gradients is not necessary. Thus the method is applicable to a wide range of problem classes.The paper introduces the basic algorithm of an evolution strategy and shows its application on the basis of two simple examples from the field of discrete optimization.
A microscopical model for electric‐mechanical contact
Authors: Boso Daniela P. , Zavarise Giorgio , Schrefler Bernhard A. 
Published: June 2004

AbstractIn this paper a model to deal with electric‐mechanical contact problems in the framework of the FEM is presented. On the basis of some micro‐mechanical studies, a new approach is developed to define the non‐linear constitutive law that governs the normal force‐displacement behaviour and the electric resistance of the contacting surfaces.
Volume and Surface Based Homogenization Procedures for Cosserat Continua
Authors: Diebels S. , Steeb H. , Ebinger T. 
Published: June 2004

AbstractThe deformation of a beam lattice is investigated as a two‐dimensional model of a foam. Forces, moments, displacements and rotations are averaged leading to stress, couple stress, strain and curvature on the macroscale. Therefore, the effective medium is assumed to be micropolar.