bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stabilitätsanalyse einer Scheibenbremse bei periodischer Parametererregung
Authors: Schmalfuss C. , Wedig W. , Ams A. 
Published: April 2003

AbstractEin mechanisches Modell mit vier Freiheitsgraden beschreibt die Scheibenbremse eines Personenkraftwagens. Nach Herleitung der Bewegungsdifferentialgleichnungen wird eine Stabilitätsanalyse bei periodischer Parametererregung (Floquet–Theorie) durchgeführt. Umfangreiche Parametervariationen zeigen den Einfluß einzelner Parameter bezüglich des Stabilitätsverhaltens des Systems.
Regen‐Wind‐induzierte Schwingungen ‐ Ursache und Beschreibung
Authors: Seidel C. , Dinkler D. 
Published: April 2003

Abstract1986 entdeckte Y. Hikiami [1] an der Meikonishi Brücke in Japan ein Schwingungsphänomen, das bei gleichzeitigem Auftreten von Regen und Wind an geneigten Kabeln bzw. Hängern entstehen kann. Hierbei sind die beobachteten Schwingungen durch große Amplituden und hohe Frequenzen charakterisiert. Das Phänomen ließ sich seitdem an vielen anderen Brücken weltweit nachweisen.
Unilateral Constrained Bending Vibrations on a Torsional String
Authors: Kreuzer E. , Struck H. 
Published: April 2003

AbstractVibrations in long torsional strings result in spatio‐temporal dynamics. In order to actively damp these vibrations the system has to be analysed analytically, numerically and experimentally. Stick‐slip‐effects result in torsional selfexcited vibrations of the string. These vibrations are coupled with bending vibrations which are constrained by the borehole. The straight string was modelled in an experimental setup. The control of the straight string and the unilateral constrained bending vibrations were treated seperately. The dynamics of straight strings were controlled using three different approaches: firstly, a simple PD‐controller with the parameters calculated based on a one‐degree‐of‐freedom oscillator, secondly, the parameters were optimized using a simplex‐method, thirdly, the Karhunen‐Loeve‐transformation was used in order to reduce the dimension of the system. A controller based on the reduced system was implemented and the parameters were optimized with the same simplex algorithm.The unilateral constrained bending motion were examined at a cantilever beam which was assumed to be constrained in one direction in the middle of the beam. First, the beam was modelled analytically as a continuous system. The two states (contact and no contact) were described separately. The transition between these states were modelled with energy assumptions. Second, the beam was modelled as a Finite‐Element‐System. The numerical results of both methods were compared with experimental data.
On Synchronization of Control Systems
Authors: Ekimov A. V. 
Published: April 2003

AbstractIn the present work the problem of synthesis of synchronizing control is considered. The point is that, instead of stabilization problem we have to construct a special control under which the close‐loop system realized a given programmed motion starting at a fixed moment of time. The theorem on the necessary and sufficient conditions of synchronizability of linear control systems is proved.
Optimal Robust Control of Robotic Systems
Authors: Kiriazov P. 
Published: April 2003

AbstractThere are continuously increasing demands to robotic systems (RS) for faster operation, higher accuracy, and lower energy cost. For the purpose of feedback stabilization, we design decentralized controllers with maximum degree of robustness. The control design criterion is based on a generalized diagonal dominant (GDD) condition proven to be necessary and su.cient for such controllers to be robust against arbitrary, but bounded, disturbances. It is defined by optimal trade‐off relations between the bounds of disturbances, the required accuracy, and the control force limits.
Contributions to flatness‐based control of systems with input‐dependent delays
Authors: Rudolph J. , Winkler J. 
Published: April 2003

AbstractFlatness‐based control of nonlinear systems has been generalized in [1] to systems with time‐delays of constant amplitude. Continuous stirred tank chemical reactors with recycle provide examples of such systems. However, if the volume flow‐rate in the recycle is used as control input the time delay depends on control. This can be avoided by a proper choice of the independent variable, i.e., time transformation: Transported volume is used instead of time. This leads to systems with a time delay of constant amplitude belonging to a class of systems which can be called a generalized type of π‐flat systems [2], barely studied so far. Motion planning and tracking control can be achieved by flatness‐based methods.
Representation and Simulation of Smart Structures in Multibody Dynamics
Authors: Heckmann Andreas 
Published: April 2003

AbstractThis paper presents a methodology for the simulation of smart structures with piezoceramic patches by means of multibody dynamics. Therefore, the theoretical background is outlined adapting a modal multifield approach. Then, an application example is used to illustrate the implemented process chain. This procedure provides the framework for the development of an environment in order to design, optimise and verify all vibration control elements.
Dynamics Modelling and Simulation Environment for Rapid Manipulator Design
Authors: Krenn R. , Schäfer B. 
Published: April 2003

AbstractFor rapid development of space robotics mission scenarios, DLR provides an efficient assembly and simulation environment. It combines a CAD based robotic subsystems data base with kinematic and kinetic software tools for modeling and simulating the behaviour of the entire robotic system. In space environment, redundant manipulators are prefered. This paper addresses two implemented approaches for solving inverse kinematics and kinetics of such kind of systems.
Dynamik von verankerten meerestechnischen Konstruktionen
Authors: Kreuzer E. , Wilke U. 
Published: April 2003

AbstractThe dynamical behaviour of moored structures in ocean engineering in an irregular sea is usually investigated by means of simplified mathematical models. Nonlinear phenomena like the influence of the motion on the mooring geometry or the fluid‐structure interaction are not considered. In this paper a method is described for analyzing the dynamical behaviour of mooring systems including the hydrodynamic forces due to the fluid surrounding the structure. The model for the dynamic analysis is generated using the multibody system method.
Modellierung instationärer Reibkräfte
Authors: Kröger M. , Lindner M. , Popp K. 
Published: April 2003

AbstractDie schnelle Geschwindigkeitsänderung während einer Stick‐Slip‐Schwingung beeinflußt oft die Reibkräfte im Kontakt so stark, dass eine einfache Beschreibung mit einer stationären Reibkraftcharakteristik nicht mehr sinnvoll ist. Die instationären Reibkräfte können mit einer Differentialgleichung anhand der stationären Reibkraftcharakteristik und zweier Zeitkonstanten beschrieben werden. Schwerpunkt dieser Untersuchung ist die experimentelle Verifizierung der Beschreibung sowie Ansätze zur Identifikation der Zeitkonstanten anhand von Geschwindigkeitssprüngen oder ‐rampen.
Motion Planning of Robot Locomotion
Authors: Mladenova C. 
Published: April 2003

AbstractSince the treatment of robot locomotion is quite closed with this one of human locomotion, the present paper treats the problems of modelling, simulation and motion planning of robot locomotion on the base of knowledge of the skeletal system, as well as on the base of multibody system modelling, simulation and control using some ideas from Lie group theory and differential geometry.
Classification and higher order analysis of manipulator singularities
Authors: Müller A. , Maisser P. 
Published: April 2003

AbstractA purely algebraic approach to higher order analysis of (singular) configurations of rigid multibody systems with kinematic loops (CMS) is presented. Rigid body con.gurations are described by elements of the Lie group SE(3) and so the rigid body kinematics is determined by an analytical map f : V → SE(3), where V is the configuration space, an analytic variety. Around regular configurations V has manifold structure but this is lost in singular points. In such points the concept of a tangent vector space does not makes sense but the tangent space CqV (a cone) to V can still be defined. This tangent cone can be determined algebraically using the special structure of the Lie algebra se (3), the generating algebra of the special Euclidean group SE (3), and the fact that the push forward map f*, the tangential mapping CqV → se (3), is given in terms of the mechanisms screw system. Moreover the differentials of f of arbitrary order can be expressed algebraically. The tangent space to the configuration space can be shown to be a hypersurface of maximum degree 4, a vector space for regular points. It is the structure of the tangent cone to V that gives the complete geometric picture of the configuration space around a (singular) point. Identification of the screw system and its matrix representation with the kinematic basic functions of the CMS allows an automatic algebraic analysis of mechanisms.
Permeability Studies on Soft Open‐Cell Foams
Authors: Ehlers Wolfgang , Markert Bernd , Diebels Stefan , Nödling Axel 
Published: April 2003

AbstractThe behaviour of fluid‐saturated solid foams can be very well described using multiphasic continuum mechanical models [4]. Concerning permeable soft foams, like e. g. gas‐filled open‐cell polyurethane (PU) foams, the transient compressive response is strongly influenced by the outstreaming pore‐fluid. Following this, it is the objective of the present contribution to point out the macroscopic permeability properties of soft foams including non‐linear phenomena influenced by the pore space deformation at varying flow rates. In particular, based on experimental investigations, an appropriate constitutive setting is presented considering the dependency of the permeability on the deformation state and on the seepage velocity in the sense of a modified Forchheimer ansatz. The constitutive equations are embedded into the macroscopic Theory of Porous Media (TPM), where the numerical treatment of the strongly coupled problem can effciently be performed with the finite element method (FEM). Finally, a numerical example shows the applicability of the presented approach.
The equivalent inclusion technique and its convergence
Authors: Müller W.H. 
Published: April 2003

AbstractThis paper addresses the convergence characteristics of an iterative solution scheme of the Neumann‐type useful for obtaining homogenized mechanical material properties within an RVE. The analysis is based on the idea of “equivalent inclusions” and, within the context of stress/strain analysis, allows modeling of elastically highly heterogeneous bodies with the aid of discrete Fourier transforms. Within the iterative scheme the proof of convergence depends critically upon the choice of an appropriate, auxiliary stiffness matrix, which also determines the speed of convergence. Mathematically speaking it is based on Banach's fixpoint theorem and only results in necessary convergence conditions. However, for all cases of elastic heterogeneity that are of practical importance convergence can be demonstrated.
Reibungsbehafteter Kontakt elastischer Walzen unter nichtsymmetrischer Last
Authors: Walter H. , Braun M. 
Published: April 2003

AbstractEine zylindrische Walze, bestehend aus einem starren Kern und einer elastischen Schicht, wird gegen eine starre, ebene Unterlage gedrückt. Der Anpreßvorgang erfolgt quasistatisch, jedoch wird die Haftreibung in der Kontaktzone berücksichtigt. Im Rahmen der linearen Elastizitätstheorie lassen sich die Verschiebungen und Spannungen in der Walze für beliebige Randlasten durch Fourier‐Reihen mit komplexen Koeffizientenfunktionen ausdrücken. Der Anpreßvorgang hängt, auch bei quasistatischer Betrachtung, von der Vorgeschichte der Deformation ab und muß deshalb inkrementell betrachtet werden. Innerhalb der Kontaktzone bilden sich Haft‐ und Verschiebungsbereiche aus.
Classes of Anisotropic Finite Plasticity Models and their Implementation in a Brick‐Type Shell Element
Authors: Apel N. , Miehe C. 
Published: April 2003

AbstractWe discuss two constitutive models formulated in terms of logarithmic strains suitable for the description of elastoplastic material response. We consider two different approaches to the definition of the plastic deformation. The first is based on the introduction of a plastic map yielding a multiplicative decomposition of the deformation gradient into an elastic and plastic part. The second one uses an additive decomposition of the current metric. A quantitative analysis of both approaches by means of numerical examples of sheet metal forming processes are presented.
Eine geschlossene Darstellung für die Ableitung von Potenzreihen nichtsymmetrischer Tensoren
Authors: Itskov M. , Aksel N. 
Published: April 2003

AbstractIsotrope Tensorfunktionen, die in Form einer Potenzreihe in bezug auf nichtsymmetrische Argumenttensoren definiert sind, spielen eine große Rolle in der numerischen Mechanik. In der finiten anisotropen Plastizität und insbesondere Einzelkristall‐Plastizität hat sich beispielsweise die Exponentialfunktion des räumlichen Geschwindigkeitsgradienten als sehr hilfreich erwiesen. Bei symmetrischen Argumenttensoren stellt man die Ableitung einer Potenzreihe mit Hilfe einer geschlossenen Formel dar, die auf der Spektralzerlegung basiert. Da jedoch nichtsymmetrische Tensoren im allgemeinen keine Spektralzerlegung (in der Diagonalform) zulassen, ist man gezwungen, sehr aufwendige numerische Prozeduren heranzuziehen. In diesem Beitrag stellen wir eine geschlossene Darstellung für Tensorpotenzreihen und ihre Ableitung vor. Diese Darstellung ist durch die Eigenwerte des Argumenttensors formuliert und gilt für alle Tensoren zweiter Stufe, symmetrische und nichtsymmetrische, mit oder ohne Spektralzerlegung. Im Sonderfall eines Argumenttensors mit einer Spektralzerlegung reduziert sich diese Darstellung auf die wohlbekannte Lösung für isotrope Funktionen symmetrischer Tensoren (siehe z.B. [1]).
A Study on Finite Orthotropic Plasticity using Generalized Measures
Authors: Löblein J. , Schröder J. , Gruttmann F. , Mehling V. 
Published: April 2003

AbstractA numerical study of anisotropic plasticity using generalized strain and stress measures [1] according to [2] is presented. The constitutive frame is described and an algorithmic implementation is proposed. The coaxiality of generalized and standard deformation measures is exploited for the numerical treatment of the projection tensors.
Controlled Deployment of a Tethered Satellite System
Authors: Barkow Bernhard 
Published: April 2003

AbstractThe deployment of a tethered satellite system undoubtedly represents one of the most critical phases in a tether mission: due to its complicated dynamics, high amplitude oscillations are likely to rise in the system, and it will take a long time to reach the desired stable radial equilibrium state. Based on a viscoelastic space billiard model, a targeting strategy is developed in this paper, which makes use of the system's chaotic nature and allows to steer the system into its equilibrium faster and more efficiently compared to conventional strategies.
A Time‐Stepping Algorithm for Stiff Mechanical Systems with Unilateral Constraints
Authors: Funk K. , Pfeiffer F. 
Published: April 2003

AbstractThis paper presents a stable implicit first order time‐stepping method for the simulation of stiff mechanical systems with unilateral constraints and Coulomb friction. It ensures that the unilateral constraints are fulfilled directly on the displacement level. The resulting linear complementarity problem is formulated in a very compact nonstandard way. A modified form of Lemke's algorithm is presented to solve it.
On the Description of Partially Saturated Soils by the Theory of Porous Media
Authors: Ehlers Wolfgang , Graf Tobias , Diebels Stefan 
Published: April 2003

AbstractIn this contribution, a multi‐phase soil model based on the Theory of Porous Media (TPM) is presented. The model is fully coupled in the following constitutive phases: An elasto‐plastic or elasto‐viscoplastic solid skeleton, a materially incompressible pore‐liquid (water) and a materially compressible pore‐gas (air). The interaction of the solid skeleton and the pore‐fluids is specified by a capillary pressure‐saturation relation, whereas the mobilities of the fluid phases in the pore‐space of the solid skeleton are described by the so‐called relative permeabilities. Finally, a gravity governed initial‐boundary‐value problem solved by the FE method is presented.
Lösung komplexer dynamischer Aufgabenstellungen mit expliziten Verfahren auf Parallelrechnern
Authors: Grochla Joachim , Köppe Heinz , Gabbert Ulrich 
Published: April 2003

AbstractDie Finite‐Elemente‐Simulation des nichtlinearen und zeitabhängigen Verhaltens komplexer mechanischer Strukturen unter Berücksichtigung von nichtlinearem Materialverhalten, großen Verformungen und Kontakteinflüssen soll genaue Aussagen zur Deformation und Stabilität mechanischer Strukturen liefern. Die Grenzen der Computersimulation werden von der Rechenzeit und der verfügbaren Speicherkapazität der vorhandenen Hardware bestimmt. Die Verwendung von expliziten Zeitintegrationsverfahren zur Lösung der semidiskreten Bewegungsdifferentialgleichungen ermöglicht eine Reduzierung der erforderlichen Speicherressourcen durch den Verzicht auf den Aufbau von Element‐ und Systemmatrizen sowie der Rechenzeit durch die Parallelisierung der Berechnungssoftware, für die sich die expliziten Verfahren sehr gut eignen. Ausgehend von einer vorhandenen speziellen Finite‐Elemente‐Software wurde ein Parallelisierungskonzept auf der Basis von MPI entwickelt und getestet, das eine schnelle Lösung großdimensionierter FE‐Probeleme der Strukturmechanik erlaubt und hier kurz vorgestellt wird.
3D Surface Smoothing for Arbitrary FE‐Meshes by Means of an Enhanced Surface Description
Authors: Helnwein P. 
Published: April 2003

AbstractThis paper describes a novel approach to the problem of 3D surface smoothing by introducing an enhanced surface description of the structural model. The idea of the enhanced surface model is the introduction of an independent vector field for the description of the surface normal field. It is connected to the discretized surface by means of a weak form of the orthogonality conditions. Surface smoothing then is applied element‐by‐element using the interpolation of the surface patch and the nodal normal vectors.
Dynamics of Layered Structures with Bonded Piezoelectric Material
Authors: Mesecke‐Rischmann S. , Lammering R. 
Published: April 2003

AbstractFor the proper design of plate and shell composite structures with piezoelectric patches bonded to the surfaces of a host structure, appropriate finite elements are presented. The linear piezoelectric effect is taken into account so that the displacements and the electric potential serve as independent variables. The electric potential can be condensed on the element level and does not enter the system of equations. This condensation has the advantage of a more efficient calculation especially for dynamic problems. With dynamic examples the two formulations are compared with each other and with solutions from the literature, which prove the accuracy and the efficiency of the formulations.
Numerische Modellierung von Hochdruckhydraulikschläuchen mit Geflechtsverstärkungen
Authors: Rattensperger H. , Eberhardsteiner J. , Mang H.A. 
Published: April 2003

AbstractIn dieser Arbeit wird ein Modell für die numerische Simulation von Hochdruckhydraulikschläuchen vorgestellt. Dabei werden das Matrixmaterial (Gummi) und die Verstärkungseinlagen (Draht‐ oder Textilgeflecht) dieser Verbundstruktur im Rahmen einer Finite Elemente (FE) Berechnung getrennt betrachtet. Die Verstärkungseinlagen werden durch Rebar‐Elemente repräsentiert, deren nichtlineares mechanisches Verhalten mittels eines Stabgittermodells beschrieben wird.
Galerkin‐type space‐time finite elements for volumetrically coupled problems
Authors: Steeb Holger , Diebels Stefan , Ehlers Wolfgang 
Published: April 2003

AbstractThe study focuses on error estimation techniques for a coupled problem with two constituents based on the Theory of Porous Media. After developing space‐time finite elements for this mixed problem, we extend the numerical scheme to a coupled space‐time adaptive strategy. Therefore, an adjoint or dual problem is formulated and discussed, which is solved lateron numerically. One advantage of the presented technique is the high flexibility of the error indicator with respect to the error measure.
Supervision System of Machining Process States
Authors: Lipiński D. , Kacalak W. , Krzyżyński T. 
Published: April 2003

AbstractDue to non‐linear, multidimensional and random character of most processes of machining, an use of analytical methods to process monitoring is difficult, time‐consuming and expensive. An application of algorithms which base on models in real processes is very limited, especially in the case of grinding processes. On the one hand, such methods require realistic and exact models of monitored process, on the other hand, they can characterize restrictive hypothesis concerning the process modeled. Most of model‐basing learning algorithms have an application to linear and steady‐state processes. However, majority of monitored processes are non‐linear, and, additionally, of nonstationary character. The system of monitoring proposed in the paper bases on artificial intelligence methods, which makes it possible to exclude from it a model of the grinding process.
On Modelling of Stochastic Processes of Abrasive Wear and Durability of Grinding Wheel
Authors: Kacalak W. , Kasprzyk M. , Krzyżyński T. 
Published: April 2003

AbstractThe aim of the paper is to present modelling of abrasive wear and grinding wheel durability by means of probabilistic description of abrasion and crush dressing of grinding wheels. Relations describing distributions of active grain age and its change during of grinding are determined. A practical application of the models proposed in the paper, using empirical data, makes it possible to determine other quantities which are very difficult to estimate in an experimental way.
On the Identification of the Parameters of a Viscoelastic Material Law for Polymeric Foams
Authors: Ehlers Wolfgang , Klar Oliver 
Published: April 2003

AbstractIn this paper, the gradient‐based sequential quadratic programming (SQP) technique is used to determine the parameters of a finite viscoelastic material law for the description of polymeric foams. Due to the cellular structure of foams, the resulting non‐linear behaviour is reproduced by an Ogden‐type law in the framework of the Theory of Porous Media (TPM) [1]. The conformity between experimental data and numerical simulation is improved by the minimization of a least squares functional under consideration of equality and inequality constraints. The result is shown by a finite element based back‐analysis of unconfined compression tests.
On Modelling and Experimental Verification of Micro‐Smoothing Process in Extra Low Temperatures
Authors: Kacalak W. , Kasprzyk M. , Krzyżyński T. , Lewkowicz R. , Ściegienka R. 
Published: April 2003

AbstractParticularly good results in micro‐smoothing of steel work‐pieces surfaces by means of imperial micro‐finishing films, and difficulties in obtaining proper machining effects for aluminium and its alloys and also for other high plasticity materials in surrounding temperature, have caused examining of this process in extra low temperatures. Carrying out the process in extra low temperature, and at the same time in vacuum, makes it possible to obtain extra smooth surfaces of elements made from aluminium. The paper presents the experimental stand which is adapted for operations in extra low temperatures and results of micro‐smoothing processes.