bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies Regarding the Alternate Simulation Techniques for Machine Toolsand Industrial Robots
Authors: Pisla A. , Pisla D. 
Published: November 2004

AbstractIn the paper are presented results regarding the design, simulation and testing of some robotized structures with parallel kinematics in order to identify appropriate simulation techniques and to reveal the properties of particular studied characteristics. The paper is structured in three parts: introduction regarding the tasks of the simulations techniques and the developed applications, comparison of the results obtained in simulations, considering the working space modelling accuracy and the speed of workspace identification and the last part conclusions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling and Mechanical Design of Underactuated Robot Manipulators with Impact and Friction
Authors: Welge‐Luessen Tobias 
Published: November 2004

AbstractThis paper provides a theoretical approach for describing underactuated mechanical systems and conceptual ideas for the design of an underactuated robot manipulator. The mathematical description uses the Linear Complementarity Problem (LCP) formulation in order to handle the equations of motion with inequality constraints. The robot manipulator serves later on as an experimental platform for the verification of control strategies of underactuated systems and the exploration of underactuated walking patterns. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Thermomechanical Model for a Class of Hyperelastic Materials with Viscoelastic Properties of a Single‐Integral Type
Authors: Dobovšek Igor 
Published: November 2004

AbstractTo incorporate the strain rate dependence and strain memory properties in the constitutive formulation, we introduce integral hereditary operators of Volterra type in place of free material constants of a general hyper stress constitutive model. The corresponding constitutive equations, which are derived from the proposed form of a free energy functional, are based on a single‐integral type representation of the response functionals inherent in the expression for free energy. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Konstitutive Modellierung der Anisotropie in kalandrierten Gummib
Authors: Ehret Alexander , Itskov Mikhail , Aksel Nuri 
Published: November 2004

AbstractIn Experimenten weisen kalandrierte Gummibänder eine transversale Isotropie hinsichtlich der Kalandrierrichtung auf [1]. Fig. 1 zeigt den Unterschied in den Nominalspannungen zwischen Kalandrier‐ und Transversalrichtung und macht deutlich, dass diese Anisotropie bei der konstitutiven Modellierung berücksichtigt werden sollte. Zu diesem Zweck werden hier zwei hyperelastische Modelle vorgeschlagen. Das erste Modell ist vom St. Venant‐Kirchhoff‐Modell abgeleitet [2] und nicht polykonvex. Polykonvexität stellt jedoch nicht nur Elliptizität und damit die Legendre‐Hadamard‐Beziehung sicher, sondern garantiert zusammen mit der Koerzivität auch die Existenz einer Deformation, die die gesamte elastische Energie des Körpers global minimiert. Dies ist insbesondere bei der Lösung von Randwertproblemen von Bedeutung. Das zweite Modell basiert daher auf einer polykonvexen Verzerrungsenergiefunktion [3]. Beide Verzerrungsenergiefunktionen werden durch Potenzreihen mit beliebig vielen Termen und einer entsprechenden Zahl an Materialparametern approximiert. Mit Hilfe der Methode der kleinsten Fehlerquadrate werden diese Modelle an experimentelle Daten angepasst. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A cohesive element approach for viscoelastic interface properties
Authors: Geissler Gordon , Kaliske Michael 
Published: November 2004

AbstractThis paper introduces a time dependent extension of the nonlinear traction separation law for an interface element. The constitutive equations of the load history dependent behaviour of the material are depicted and derived according to a generalized Maxwell‐model. This finite linear, viscoelastic approach allows the consideration of long term loading and time dependent material behaviour in thin layers. The implementation of the presented element formulation and the material approach are verified by numerical examples. The paper gives an outlook on further work and research topics. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of the rail pad on a vehicle travelling on a straight track
Authors: Gerstberger Ulf , Knothe Klaus , Rücker Werner 
Published: November 2004

AbstractIn the following text, the influence of the stiffness of rail fastening systems of high‐speed railway lines on the dynamic stability of a vehicle travelling along a straight track is investigated. The dynamic behaviour of the rail head in lateral direction is incorporated in the model by means of mechanical models derivedfrom a preceding frequency analysis of the track. For the wheel‐rail interface, linear contact mechanics and kinematic relations are applied. The investigation leads to the conclusion that on high‐speed lines the critical velocity of vehicles is reduced as a result of the increased elasticity of the rail pads. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reibungsinduzierte thermoelastische Instabilitäten von Kreisringplatten
Authors: Krempaszky Christian , Werner Ewald , Lippmann Horst 
Published: November 2004

AbstractIn diesem Beitrag wird auf Basis der Kirchhoffschen Plattentheorie ein Modell zur Beschreibung der reibungsinduzierten thermoelastischen Instabilitäten (TEI) in Kreisringplatten erstellt. Die Hauptaufgabe besteht in der Formulierung der thermomechanischen Rückkopplung des Reibkontakts. Mit dem resultierenden Eigenwertproblem lassen sich die kritischen Betriebszustände abschätzen. Als Anwendungsbeispiel wird das Scheibenpaket einer Mehrscheibenkupplung betrachtet. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A 3‐level discretisation strategy using substructuring
Authors: Rickelt Christian , Schwarze Marco , Reese Stefanie 
Published: November 2004

AbstractThis contribution deals with a new three‐level discretisation strategy which enables to discretise a structure according to the required modelling accuracy. Correspondingly the structure is separated into a continuum, a structural and a black box model level. This note especially focuses on the transitions between continuum‐structure and structure‐substitute model. The first one is realised by means of a model adaptive concept based on the innovative finite element technology of the Q1SP family. The latter is carried out by an enhanced modal reduction method which is combined with a novel substructure technique. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inplane Stress Singularities at the Corner of an Anisotropic Material Discontinuity
Authors: Wigger Hubertus Michael , Becker Wilfried 
Published: November 2004

AbstractIn the mechanics of composite laminates the local mechanical inplane fields at corners of anisotropic material discontinuities are of particular interest since they can have singular behavior. In the present study, the stress and strain fields in the local near field of such corners are investigated by an asymptotic analysis. The order of the singularity of these mechanical inplane fields are determined in closed‐form manner by use of the complex potential method based on Lekhnitskii's approach. Various different geometrical setups and material combinations of corners with material discontinuities are investigated with regard to their effect on the singular behavior of the mechanical fields present. These examples show that the order of singularity considered is clearly weaker than the typical crack tip singularity in fracture mechanics. Nevertheless, it may render the corner a critical location for the onset of failure. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical simulation of microstructures via higher‐order rank‐one relaxation
Authors: Hoppe Ulrich , Hackl Klaus 
Published: November 2004

AbstractCalculation of inelastic material behaviour by means of relaxation algorithms provides an effective way to deal with fine‐scale microstructures resulting from non‐quasiconvex potentials. Especially the rank‐one relaxation admits a straight forward algorithmical realization and results in valuable information that enables the reconstruction of the underlying microstructure. This article is concerned with the application of higher–order rank–one relaxation to a single–slip plasticity model and focusses especially on the numerical algorithm. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reine Scherung mit rotierenden Achsen
Authors: Besdo D. , Hohl C. , Ihlemann J. 
Published: November 2004

AbstractBei der Entwicklung komplexer Stoffgesetze und bei deren Anpassung an konkrete Materialien spielen die experimentelle Realisierung und die Simulation homogener Belastungs‐ und Verformungsprozesse eine entscheidende Rolle, da diese das reine Materialverhalten widerspiegeln. Für die Formulierung der jeweiligen Randbedingungen bieten sich bei verschiedenen Prozessen unterschiedliche Spannungs‐ und Deformationsmaße an. Als ein mit herkömmlichen Algorithmen besonders schwer zu erfassendes Beispiel wird die reine Scherung mit rotierenden Achsen vorgestellt. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ellipsoidrepräsentation von Anisotropietensoren
Authors: Besdo D. , Ihlemann J. 
Published: November 2004

AbstractBei vielen Werkstoffen, deren mechanisches Verhalten langfristig von der Belastungsvorgeschichte beeinflußt wird, ist dieser Einfluß mit einer ausgeprgten induzierten Anisotropie verbunden. Während sich für die Modellierung isotroper Materialver änderungen im Idealfall ein einzelnes skalares Maß als ausreichend erweist, sind f ür die Beschreibung induzierter Anisotropie tensorielle Größen erforderlich. Häufig sind hierfür Tensoren 4. Stufe nötig [1]. In einfacheren Fällen erlaubt die Ellipsoidrepräsentation von Tensoren 2. Stufe einen anschaulichen Zugang zu deren Verwendung als Anisotropietensoren. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of nonlinear properties of ferroelectric and piezoceramicmaterials
Authors: Delibas Bülent , Arockiarajan Arunachalakasi , Seemann Wolfgang 
Published: November 2004

AbstractFerroelectric and piezoelectric materials are becoming a very significant part of smart materials that are used widely as actuators, sensors and most common applications such as vibration control, precision positioning, precision cutting and microelectromechanical systems (MEMS). Piezoceramic materials show nonlinear characteristics when they are under high electromechanical loading. In this study, nonlinear behaviour of tetragonal perovskite type piezoceramic materials is simulated using micromechanical model. In the simulations uni‐axial loading is applied. The calculations which are based on a linear constitutive model, nonlinear domain switching model and a model of probability to switch are performed at each grain. The different domain switching effects (900 or 1800 domain switching for tetragonal perovskite structure) due to energy differences, different probability functions, different statistical random generators and material parameters are analyzed. Finally, simulation results are compared with the data of experiments are giving in literature. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micro‐ and nanoscale modelling of dry friction with application to the wheel/rail contact
Authors: Ertz M. , Knothe K. , Popov V. L. , Psakhie S. G. 
Published: November 2004

AbstractFriction is a phenomenon involving elastic interactions, plastic deformation and failure processes at different length scales. A model of dry friction is established based on the method of Movable Cellular Automata (MCA). The influence of material and loading parameters has been investigated within a large number of numerical simulations. The new friction law is applied to the calculation of stresses, deformations and tractive forces in wheel/rail contact with rough surfaces. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The theoretical treatment of cooling processes in porous rocket thrustchambers
Authors: Ghadiani Said , Ehlers Wolfgang 
Published: November 2004

AbstractOne of the most promising approaches for future high pressure rocket combustion chambers is the application of porous carbon fiber reinforced ceramics in conjunction with the effusion cooling in fluid‐cooled rocket engines. In order to determine the coolant mass flow through the porous material, the influences of the temperature have to be taken into account additionally. Thus, one has to deal with interacting continua governed by non‐isothermal processes, when designing a porous rocket combustion chamber for realistic operating conditions such as extremely high temperatures. Describing coupled solid‐fluid problems efficiently, it is generally convenient to utilize macroscopic strategies like the Theory of Porous Media (TPM). While in the past, most of the multiphase problems based on the TPM have been treated isothermally, the present contribution extends the theoretical treatment to non‐isothermal problems. This is achieved by proceeding from a thermoelastic solid skeleton saturated by a compressible viscous pore‐fluid, whereas a separate temperature field has to be established for each constituent. Finally, the efficiency of the developed model will be briefly discussed by computing some simple non‐isothermal physical effects, which are solved by the FE tool PANDAS. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modellierung der pseudoelastischen Materialeigenschaften von Formgedächtnislegierungen
Authors: Helm Dirk 
Published: November 2004

AbstractDie pseudoelastischen Materialeigenschaften von Formgedächtnislegierungen werden unter anderem im Bereich der Medizintechnik eingesetzt (vgl. [1]). In dem Artikel wird ein Materialmodell zur Beschreibung der Pseudoelastizität vorgestellt (vgl. [2]). Das Materialmodell basiert auf einer Materialfunktion für die Freie Energie sowie Evolutionsgleichungen für Innere Variable. Die Energiefunktion beschreibt dabei Energiespeicherungsvorgänge aufgrund der Thermoelastizität, der Energiedifferenz zwischen den beiden betrachteten Phasen (Austenit und Martensit) sowie die Energiespeicherung infolge der Entwicklung von Inneren Spannungen. Das System der Konstitutivgleichungen erfüllt den 2. Hauptsatz der Thermodynamik in Form der Clausius‐Duhem Ungleichung. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the effect of cell irregularity on the effective behavior of solid foams
Authors: Hohe Jörg , Becker Wilfried 
Published: November 2004

AbstractThe present study provides an analytical probabilistic approach for the homogenization of hyperelastic solid foams with irregular microstructure. The scheme is based on the multiple analysis of a randomized representative volume element in conjunction with a stochastic evaluation of the results in terms of the stress mean values and the corresponding standard deviations defining the scatter band widths. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Konstitutives Modellieren von Fichtenholz unter biaxialer Beanspruchung mittels eines orthotropen Einflächenmodells unter Berücksichtigung von Ver‐ und Entfestigung
Authors: Müllner Herbert Wolfgang , Eberhardsteiner Josef , Mackenzie‐Helnwein Peter 
Published: November 2004

AbstractIn diesem Beitrag wird über die Entwicklung eines Einflächen‐Plastizitätsmodells für fehlerfreies Fichtenholz unter biaxialen Beanspruchungszuständen berichtet. Zur Beschreibung des elasto‐plastischen Materialverhaltens wurde eine elliptische Fließfläche nach [5] herangezogen, dessen Form mittels einer nicht‐assoziierten Ver‐ und Entfestigungsregel gesteuert wird. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the stabilization mechanisms in liquid metallic foams
Authors: Wübben Th. , Odenbach S. 
Published: November 2004

AbstractMetal foams are porous structures made up of conventional metals such as aluminium. Their advantageous density to stiffness ratio leads to a variety of applications especially in automotive industry, where they have gained interest as material used in shock absorbers and light weight construction parts.Solid metal foams are usually produced by solidification of a liquid metallic foam. The latter is generated by the introduction of gas into a melt analogous to aqueous foams. Depending on the parameters of the production process, porous structures with relative densities down to 10% of the original metal can be achieved. However, while the mechanisms leading to stable aqueous foams are quite well understood, this is not the case for metallic foams. In contrast for example to soap foams, no surface active or polar substances are present in liquid metals. It is merely known empirically that solid particles have a major influence on the stability of a liquid metallic foam.In this paper we present experimental observations showing that the stability and structure of metallic foams produced via a melt route are predominantly governed by interface rather than drainage effects. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Higher order continuum models for cellular materials including damage
Authors: Ebinger Tobias , Steeb Holger , Diebels Stefan 
Published: November 2004

AbstractAn extended continuum‐mechanical model for the description of the deformation behavior of foam‐like structures including damage ist presented. While it is very difficult to formulate constitutive equations on the macroscale for these materials, the constitutive equations, material parameters and evolution equations including damage are assumed to be known for the beamlike microstructure. Within a finite element computation the strains and, according to the macroscopic extended continuum model, the curvatures are mapped to the integration point. Attaching a microstructure to each integration point allows for the construction of a boundary value problem for the local microstructure. After evaluation of the microscopic constitutive equations, the forces and moments are mapped back to the macroscale by a homogenization procedure yielding the stress and couple stress response. This approach is known from literature as FE2 model. The capability of the model is demonstrated in a numerical example. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the assessment of cracks within the interface of thin layers on a substrate
Authors: Müller A. , Goswami S. , Hohe J. , Becker W. 
Published: November 2004

AbstractAlthough bimaterial wedge or notch configurations are identified as potential weak locations, the assessment of the degree of criticality of cracks in such regions is still a demanding problem. The singular character of the stress field at cracks or at bimaterial notches can be calculated analytically or numerically. The angle of the direction of potential crack initiation may also be determined, but the decisive question is whether a hypothetical crack will be initiated or not.An essential question in the context of crack assessment is to find a criterion for crack nucleation. For that aim, the hypothesis of Leguillon is modified. Herein, the crack is assumed to be critical when and only when both the released energy and the local stress reach critical values along a hypothetical crack of finite length. This concept can be transferred to a bimaterial interface configuration of a thin layer on a substrate. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prenatal ultrasound diagnosis of a case of Pfeiffer syndrome without cloverleaf skull and review of the literature
Authors: Nazzaro Alfredo , Monica Matteo Della , Lonardo Fortunato , Blasi Arturo Di , Baffico Maria , Baldi Maurizia , Nazzaro Giovanni , Placido Giuseppe De , Scarano Gioacchino 
Published: November 2004

AbstractPfeiffer syndrome is characterized by bilateral coronal craniosynostosis, midface hypoplasia, beaked nasal tip, broad and medially deviated thumbs and great toes. Originally, it was described in eight persons from three generations in a pedigree consistent with an autosomal dominant transmission. Since then, several reports have documented its high clinical and genetic heterogeneity. The condition is usually detected in the newborn period or later, and very few prenatal ultrasound diagnoses have been reported.We present a case of Pfeiffer syndrome prenatally diagnosed at 20 weeks' gestation, in which the sonographic features of craniosynostosis, hypertelorism associated with an extreme proptosis, and broad thumb led to the diagnosis, confirmed after termination of pregnancy by dysmorphological, pathological and radiological evaluation.DNA analysis of the fibroblast growth factor receptor 2 (FGFR2) showed a missense mutation consisting in a transversion G → C at nucleotide 870. This led to a Trp290Cys amino acidic substitution.We discuss the relevant findings of our and previously published cases. Our report demonstrates that a careful sonographic examination can lead to an early prenatal diagnosis of Pfeiffer syndrome also in cases without cloverleaf skull. Copyright © 2004 John Wiley & Sons, Ltd.
Placenta growth factor levels in second‐trimester maternal serum in Down syndrome pregnancy and in the prediction of preeclampsia
Authors: Lambert‐Messerlian Geralyn M. , Canick Jacob A. 
Published: November 2004

AbstractObjectivesTo determine the levels of placenta growth factor (PlGF) in second‐trimester maternal serum samples from pregnancies affected with fetal Down syndrome and from those that developed preeclampsia and to assess the utility of PlGF as a screening tool for these conditions.MethodsResidual second‐trimester maternal serum samples were retrieved from freezer storage for 39 cases of Down syndrome and 44 pregnancies that later developed preeclampsia. Each case was matched to 5 control samples for gestational age at collection and duration of freezer storage. PlGF levels were measured in each sample by enzyme‐linked immunosorbent assay (ELISA).ResultsPlGF levels increased with gestational age between 15 and 20 gestational weeks. After adjusting for gestational‐age effects, the median level of PlGF was 1.01 MoM in Down syndrome pregnancy and 0.74 MoM in pregnancies that developed preeclampsia, which were not significantly different from matched controls. The duration between sampling and onset of preeclampsia did not have an effect on the PlGF level.ConclusionPlGF levels are not significantly altered in second‐trimester maternal serum samples from cases of Down syndrome or in pregnancies that develop preeclampsia. Copyright © 2004 John Wiley & Sons, Ltd.
Temporary networks in polymer‐modified asphalts
Authors: Polacco Giovanni , Stastna Jiri , Vlachovicova Zora , Biondi Dario , Zanzotto Ludovit 
Published: November 2004

AbstractThe viscosity functions of several polymer‐modified asphalts (PMAs) were studied at different temperatures in steady‐state rate sweep tests. The materials were obtained by mixing different base asphalts with either styrene‐butadiene‐styrene (SBS), ethylene‐vinylacetate (EVA) or reactive ethylene terpolymers (RET). The first two polymers form a physical network that is swollen by the asphalt, while the latter is functionalized with glycidylmethacrylate (GMA) and can crosslink and/or chemically bond with the molecules of asphaltenes. In the presence of SBS or EVA, at certain temperatures, the viscosity curves exhibit a Newtonian behavior at low shear rates, followed by two distinct shear‐thinning phenomena. In some cases, the first shear‐thinning is preceded by a small shear‐thickening region. Similar phenomena are not present in the viscosity curves of the RET‐modified asphalts and can be related to a temporary nature of the physical polymer network. Polym. Eng. Sci. 44:2185–2193, 2004. © 2004 Society of Plastics Engineers.