bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Dynamic Model for a Hybrid Articulated Robot
Authors: Höbarth Wolfgang , Gattringer Hubert , Bremer Hartmut 
Published: February 2009

AbstractThe dynamic modeling of hybrid systems, consisting of flexible and rigid parts results in large partial differential equation systems (PDE). With the assumption of small deflections and the Ritz expansion the PDE can be approximated by an ordinary differential equation system (ODE) but the number of degrees of freedom is generally high.In this paper a hybrid articulated robot with 2 flexible links and 6 joints is under consideration. The joints are equipped with Harmonic Drive gears with high gear ratio but relative low stiffness. Therefore additionally degrees of freedom are introduced for the elastic deflection of the gears. The links are modeled with flexibility in two bending directions and in torsional sense.To be able to achieve structured equations the projection equation in subsystem representation is used. The projection equation is based on the momentum and the angular momentum equations of each single finite or infinitesimal body which are projected into the space of minimal coordinates and subsequently are summed up. Groups of bodies are collected to the so called subsystems with separated describing velocities. These subsystems are linked together with the kinematical chain. Because the robot is tree structured it is possible to obtain an explicit expression for the second derivatives of the minimal coordinates with a recursive scheme (O(n) efficiency).The robot is controlled with a feed forward controller and a linear PD joint controller. Simulation results and measured data are presented and compared. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of Force Transmission in Vehicle Steering Systems
Authors: Tobias Christoph , Eberhard Peter 
Published: February 2009

AbstractThis contribution proposes an approach, how the problem of a moving load on an elastic, beam–like body in an elastic MBS can be solved. Thereby a so–called moving interface marker is used. This marker can move along the bending line of the elastic, beam–like body and locates the point where the moving load is applied. With its help, the moving load can be transformed to forces and torques that have to be applied at the adjoining body–fixed interface markers. These calculated forces and torques lead to an identical deformation of the beam. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the performance of ground vehicles under the influence of stochastic wind loads
Authors: Wetzel Christian , Proppe Carsten 
Published: February 2009

AbstractThe influence of aerodynamic loads on the performance of ground vehicles is an important economical, safety and comfort issue. For the safety and comfort matters, especially the crosswind behavior of the ground vehicles is of great interest, as strong lateral winds can cause major accidents or at least make the driver and the passengers feel very uncomfortable and insecure.Two different failure scenarios dominate the safety aspect. The most important one is the risk of overturning, which happens not very often but if it occurs it leads in most cases to serious personal damages and the second one is the sudden lane change of road vehicles and the associated driving instabilities because of unforeseen gusts.As most of the design and excitation parameters of the system are uncertain, they are recognized as stochastic variables. Taking the mentioned failure scenarios into account the probability of failure of a freight vehicle has been computed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computer system for kinematic and dynamic analysis synthesis of rigid and flexible multibody systems
Authors: Zahariev E. 
Published: February 2009

AbstractIn the paper an overview of a general numerical algorithm and program system library for deriving the kinematic constraint equations and dynamic equations of motion, as well as, computation of their first and second order partial derivatives with respect to kinematic parameters of motion, design parameters and mass and inertia characteristics for rigid and flexible multibody systems is presented. These are the main basic computational modules for implementation of kinematic and dynamic synthesis, optimization and design. The main theoretical basis consists in matrix methods for deriving the kinematic constraints and dynamic equations, as well as, the generalized Newton – Euler dynamic equations for rigid and flexible bodies, and finite element discretization in relative coordinates. Block–scheme of the computational procedures and problem oriented program compilation is presented. An example of kinematic synthesis of six–link path generating mechanism with singular points is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An efficient quantitative ultrasonic elastography based on variational h‐refinement
Authors: Arnold Alexander , Mosler Jörn , Reichling Stefan , Khaled Walaa , Bruhns Otto Timme 
Published: February 2009

AbstractQuantitative elastography is a method to visualise a stiffness distribution. It is motivated by the observation that changes in mechanical properties of soft tissue mostly include important diagnostic information. With an ultrasound–elastography system, the displacement field can be calculated from the pre– and post–deformation image. Using the assumption that the material is elastic, isotropic and nearly incompressible, the distribution of shear modulus is determined by solving an inverse problem. While common approaches use a constant mesh, a variational h–refinement is in the focus of this work. In doing so, the efficiency and accuracy of the determination can be increased. The presented results are generated by using numerical simulations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pressure induced phase transitions in edible fats
Authors: Gillig Sebastian , Ferstl Peter , Eder Cornelia , Wierschem Andreas , Ruß Winfried 
Published: February 2009

AbstractPhase change reactions of food ingredients are essential for food technology. We present an optical in situ–technique to examine high pressure induced freezing processes in edible fats up to 450 MPa. The results indicate that the thermodynamic parameters not only influence the solidification kinetics, but also influence the structure of the resulting solid fat. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of different plasticity criteria for trabecular bone failure modelling
Authors: Jirousek Ondrej 
Published: February 2009

AbstractDifferent plasticity criteria applied to failure analysis of trabecular bone are compared. A cylindrical sample of bovine trabecular bone is mechanically tested in uniaxial compression/tension with 2% applied strain. Obtained response in compared to responses obtained using finite element model of trabecular bone inner structure subjected to the same loading conditions. FE model is reconstructed from micro–CT images. Elastic material properties at the level of trabecula are determined using nanoindentation. Compared plasticity criteria are based on these elastic material properties, i.e. on Young's modulus of elasticity from nanoindentation. The objective of the paper is to demonstrate the importance to reflect the anisotropic plasticity and to evaluate variation in obtained response when the anisotropy is neglected. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On a variational, free‐discontinuity formulation of brittle fracture: mean‐field relaxation and numerical solution
Authors: Dimitrov Slav , Bhlke Thomas 
Published: February 2009

AbstractIn this paper we address the resolution of two important issues arising in the context of the relaxed variational formulation of the incremental free–boundary value problem of brittle fracture. First issue, is how by recasting the formulation into a discrete, minimum–maximum problem one can avoid the undesirable scale effects expressed in terms of the characteristic size and domain–shape dependence of the calculated minimum; second, how by a remeshing procedure in combination with a domain–shape update for tracking the propagating 0–th level set one can reconstruct the crack surface. We finally illustrate our approach by a geometrically linear 2–dimensional example for crack propagation in an initially isotropic brittle solid. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of primary and secondary creep for a wide stress range
Authors: Gorash Yevgen , Altenbach Holm , Naumenko Konstantin 
Published: February 2009

AbstractMany materials exhibit a stress range dependent creep behavior. The power–law creep observed for a certain stress range changes to the viscous type creep if the stress value decreases. Recently published experimental data for advanced heat resistant steels indicate that the high creep exponent (in the range 5–12 for power–law behaviour) may decrease to the low value of approximately 1 within the stress range relevant for engineering structures. The aim of this paper is to confirm the necessity of the assumption of the stress range dependent power–law–viscous creep transition for the solution of stress relaxation problems affected by creep behavior at elevated temperatures. A constitutive model for the minimum creep rate is introduced to describe both the linear and the power law creep depending upon the stress level. The proposed constitutive model includes a strain hardening function to describe the primary creep stage. To demonstrate the existence of the linear creep behaviour in the low stress range of application area and the influence of the primary creep behaviour on relaxation, several solutions of a uniaxial stress relaxation problem are presented for the loading values relevant to engineering applications. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fracture analysis of cladded components considering residual stresses
Authors: Hohe Jörg , Brand Marcus , Siegele Dieter 
Published: February 2009

AbstractThe present study is concerned with an experimental and numerical investigation of the behavior of sub–clad and surface cracks in cladded components considering the residual stress field due to the welding and heat treatment processes. For this purpose, two large–scale tests on cladded cracked specimens have been performed and analyzed numerically. It is observed that the fracture process is initiated in the heat affected zone of the base metal underneath the cladding whereas the cladding remains intact even in case of a brittle crack extension and arrest in the base material. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Periodic set of the interface cracks with contact zones
Authors: Kozinov S. 
Published: February 2009

AbstractA closed form solution to the plane problem of the theory of elasticity for an infinite isotropic bimaterial space (plane) with a periodic set of the interface cracks with frictionless contact zones near its tips is obtained. By means of the complex function presentation the problem is reduced to the combined Dirichlet–Riemann boundary value problem for a sectionally–holomorphic function and solved exactly. The equations for the determination of the contact zone length as well as the closed form expressions for the stress intensity factors are carried out. The variation of the mentioned values with respect to the distance between the cracks is illustrated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A phase field model for fracture
Authors: Kuhn C. , Müller R. 
Published: February 2009

AbstractThe variational formulation of brittle fracture as formulated for example by Francfort and Marigo in [1], where the total energy is minimized with respect to any admissible crack set and displacement field, allows the identification of crack paths, branching of preexisting cracks and even crack initiation without additional criteria. For its numerical treatment a continuous approximation of the model in the sense of Γ‐convergence has been presented by Bourdin in [2]. In the regularized Francfort–Marigo model cracks are represented by an additional field variable (secondary variable) s∈[0,1] which is 0 if the material is cracked and 1 if it is undamaged.In this work, we reinterpret the crack variable as a phase field order parameter and address cracking as a phase transition problem. The crack growth is governed by the evolution equation of the order parameter which resembles the Ginzburg–Landau equation. The numerical treatment is done by finite elements combined with an implicit Euler scheme for the time integration. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fracture Mechanics of Rubber Material
Authors: Morgner Christiane , Kaliske Michael 
Published: February 2009

AbstractThis contribution presents an approach based on the material force method which allows to evaluate the fracture sensitivity of rubber material. In order to account for the rate–independent dissipation of filled elastomers subjected to low rates, an endochronic plasticity formulation is introduced. It is shown how configurational forces under consideration of material body forces correspond with the elastic and dissipative energy and how they can be related to energy release rates measured in test configurations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of Cracks with Bridged Zone of Large Scale
Authors: Perelmuter Mikhail 
Published: February 2009

AbstractABSTRACT. The direct boundary element method is used to analyze of the stress–strain state and fracture parameters of fiber–reinforced and layered composites with bridged interface cracks under transient thermal and mechanical loadings. It is supposed that unbroken fibers make up a bridged zone along of whole or part of a delamination region between layers of composite materials. For modelling purposes a bridged zone is considered as a part of a crack between joined materials and supposed that distributed spring–like bonds with given nonlinear deformation law link and constrain crack surfaces. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On a numerical scheme for curved crack propagation based on configurational forces and maximum dissipation
Authors: Schütte Henning , Molla‐Abbasi Kianoush 
Published: February 2009

AbstractA numerical scheme is presented to predict crack trajectories in two dimensional components. First a relation between the curvature in mixed–mode crack propagation and the corresponding configurational forces is derived, based on the principle of maximum dissipation. With the help of this, a numerical scheme is presented which is based on a predictor–corrector method using the configurational forces acting on the crack together with their derivatives along real and test paths. With the help of this scheme it is possible to take bigger than usual propagation steps, represented by splines. Essential for this approach is the correct numerical determination of the configurational forces acting on the crack tip. The methods used by other authors are shortly reviewed and an approach valid for arbitrary non–homogenous and non–linear materials with mixed–mode cracks is presented. Numerical examples show, that the method is a able to predict the crack paths in components with holes, stiffeners etc. with good accuracy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fatigue crack initiation in naval welded joints: experimental and numerical approaches
Authors: Thevenet D. , Lautrou N. , Cognard J.Y. 
Published: February 2009

AbstractThis work deals with the fatigue behavior of welded joints. The proposed strategy can be split into two stages: the structure shakedown study and the fatigue crack initiation study. Firstly, stabilized elastic stress–strain cycles are obtained in any point of the welded joint by a finite element analysis, taking constant or variable amplitude loadings into account. The second part of this work is the calculation of the fatigue crack initiation period. Under the assumption of a fast elastic shakedown, a recent approach, proposed by Lemaitre et al., based on damage mechanics, can be used to predict the fatigue crack initiation life in a structure subjected to variable and complex loadings. This strategy is used as a post–treatment of the shakedown finite element calculation for the studied welded specimen. As a validation, four–point bending fatigue tests under constant amplitude loading were carried out on welded specimens provided by DCNS group. Good correlations between experimental and calculated fatigue crack initiation lives have been established. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adaptive finite elements methods for virtual engineering design
Authors: Barthel Corinna , Gabbert Ulrich 
Published: February 2009

AbstractThe focus of this paper is the utilization of improved stresses on the surface of a construction for error estimation. The improved stresses are derived by using stress boundary conditions. They are applied for the calculation of recovered stresses required by the Zienkiewicz–Zhu error indicator. This approach leads to an enhancement of the error estimation on the boundary. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigations of the influence of geometrical irregularities and roughness on the normal contact stiffness of joints
Authors: Goerke Daniel , Willner Kai 
Published: February 2009

AbstractConducting experiments is necessary to determine the normal contact stiffness of rough surfaces. In compression tests the interface of specimen pairs is loaded in normal direction and the deflection is measured by extensometers with strain gages. The results can be used for example to describe the contact behaviour of joints in finite element analyses. It is shown that geometrical irregularities which are superposed by the surface roughness have a large influence on the elastic deformation of a joint and on the determination of the contact stiffness. They can be characterized by a skewed and a waved form of the surface with wavelengths which are larger than the surface roughness. In the experimental setup several different surfaces are compressed. In addition, the influence of the size of the contact area on the deformation of a joint is analysed. The results of the normal contact tests are compared with numerical simulations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Combined unstructured and hanging‐node‐based remeshing with boundary control for metal forming simulations
Authors: Gu X. , Hortig C. , Svendsen B. 
Published: February 2009

AbstractDuring finite element simulation of metal forming process, the mesh which represents the workpiece undergoes extreme large deformation, which could result in highly distorted mesh and numerical failure in simulation. To overcome the problem and improve computation efficiency, advancing front quad meshing technique and non–conforming mesh refinement approach are combined to generate new mesh according to desired mesh size distribution. Application of the combined remeshing strategy to rolling simulation will be presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Assessment of Historic Masonry by Cutting and Fracture Tests
Authors: Gutermann Marc , Schröder Carsten 
Published: February 2009

AbstractThe existing stress and strain conditions of historic masonry structures are unknown due to several influences (e.g. damages, settlements, permanent loads). Their actual load carrying safety can only be assessed analytically by a conservative estimation of all imponderables. The result is often insufficient and may lead to a reduction of the allowed live load. By assessing experimentally the existing strain conditions using a slightly destructive method, the allowed live load may be increased. Thus some masonry structures can be prevented from demolition or be admitted to higher live load. The new developed method is based on the well known “Flat–Jack–Procedure” and shall improve the applications as well as the accuracy. It involves attaching measurement devices to the masonry surface, cutting longitudinally and horizontally and measuring the relief of strain. A mobile load device is used to collect information of the inhomogeneous specimen (consisting of brick and mortar). Thus Young's Modulus of Elasticity as well as the ultimate strain ϵ[u] are assessed. In this paper the theoretical background and the experimental set–up is described and examples show the achieved results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stability analysis of a liquid filled barrelled horizontal tank
Authors: Jasion P. 
Published: February 2009

AbstractThe present work is devoted to the stability of liquid filled horizontal tanks. The possibility of substitution of a cylindrical tank with a barrelled one is investigated. A family of barrelled shells was created and subjected to the numerical analysis. The model of the shell was simply supported at both ends and subjected to the hydrostatic pressure. The values of the critical load and the buckling shapes were determined. The advantages of barrelled shells and their behaviour under hydrostatic load are described. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Material models in principal stretches for elastodynamics
Authors: Müller Melanie , Groß Michael , Betsch Peter 
Published: February 2009

AbstractIn the present work we deal with the conserving integration of elastic bodies undergoing finite deformations. In particular, we make use of constitutive laws formulated in terms of principal stretches.Most material models for hyperelastic isotropic materials are described in terms of principal stretches (Simo and Taylor [1]), like the Neo–Hooke material which is a special case of the Ogden material, or in invariants. The main advantage of principal stretches is the fact that they can be measured directly, which means that the numerical results can be compared easily with experimental ones, see for example, Ogden [2]. Moreover, it is advantageous to describe viscoelastic material behaviour (e.g. rubberlike materials) in terms of principal stretches.Concerning the discretization in space we apply the enhanced assumed strain (EAS) method, see Simo and Armero [3]. For the discretization in time we aim at numerical integrators which inherit fundamental conservation laws from the underlying continuous system. In particular, we propose an energy and momentum conserving time–stepping scheme which relies on the notion of a discrete gradient (or derivative) in the sense of Gonzalez [4]. The proposed approach starts from our previous developments in [5]. Numerical examples demonstrate the advantageous properties of the present formulation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Elactic buckling of thin‐walled beams with sandwich and double bends flanges
Authors: Paczos P. , Zawodny P. 
Published: February 2009

AbstractThis of the paper are two thin–walled beams with sandwich and double bends flanges. Cross section of these beams is of C type. The beams are simply supported and subjected to a couple of moment – the pure bending. Geometric propeties (warping functions and inertia moments) of two sections with sandwich and double bendsflanges are separately described by dimensionless parameters. Values of critical loads for family of thin–walled beams are numerically determined on the ground of analytical solution. A comparative analysis for selected beams with the use of FEM is performed. Morover the values of critical loads for a family of thin–walled beams are experimentally researched in the Material Strength Laboratoey of the Poznan University of Technology. Finally, the results of the investigation for thin–walled beams are compared in paper. Results of the calculation are presented in tables and figures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)