bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of the Physiological Contact Pressure Distribution in the Human Hip Joint
Authors: Lutz André , Fietz Kristin , Nackenhorst Udo
Published: March 2010

In this contribution a finite element analysis of the proximal femur and the acetabulum regarding the physiological contact pressure distribution is presented. Using a detailed 3D finite element model obtained from CT data, the contact pressure in the human hip will be analysed and a summary with respect to different movement situations will be shown. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A micro‐sphere‐based remodelling formulation for anisotropic biological tissues
Authors: Waffenschmidt Tobias , Menzel Andreas
Published: March 2010

Soft biological tissues possess a pronounced composite‐type multi‐scale structure together with strongly anisotropic mechanical properties. A fibre‐like network structure is characteristic for this kind of materials. If the tissue is exposed to mechanical loading, the initially possibly unstructured collagen fibre network tends to reorient with the local dominant stretch direction – it adapts according to the particular loading conditions. In general, biological tissues exhibit changes in mass, also denoted as growth, and internal structure, which is commonly referred to as remodelling. In this regard, an anisotropic micromechanically motivated model that incorporates such time‐dependent remodelling effects will be discussed in this contribution. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of Damage Hysteresis in Soft Biological Tissues
Authors: Brinkhues Sarah , Balzani Daniel , Holzapfel Gerhard A.
Published: March 2010

Arterial lumen reductions result in hypertension and possibly rupture of plaque deposits as a consequence of atherosclerotic degeneration which can finally cause a heart attack or a stroke. Hence, therapeutical treatments such as balloon angioplasty and stenting are required. The aim of this work is to propose a new model for the softening hysteresis observed in overstretched arterial tissues and related computer simulations. The physiological loading domain is described by a purely elastic polyconvex anisotropic strain‐energy function, which is decoupled into an isotropic part related to the non‐collagenous matrix material, and into a transversely isotropic part related to the embedded (collagen) fibers. A scalar‐valued damage variable is taken into account for the fibers to cover a saturation function converging to a maximal damage value at a fixed maximum load level. In addition, the model captures remnant strains in the fiber direction after unloading. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A three‐dimensional multiscale finite element model describing the adhesion of a gecko seta
Authors: Sauer Roger A.
Published: March 2010

A three‐dimensional multiscale model is presented which describes the adhesion and deformation of a gecko seta. The setae are micrometer fine hairs, covering the surface of the gecko toes, which enable the gecko to adhere to inclined and overhanging surfaces. The seta modeling is approached on three different length scales: At the top level, on the order of several micrometers, a finite element rod model is chosen to capture the branched microstructure of the gecko seta. At the intermediate level, on the order of several nanometers, a second finite element model is used to capture the detailed behavior of the seta tips, the so‐called spatulae. At the third level, on the order of Ångstroms, the adhesion forces between spatulae and substrate are modeled on the molecular level. The model allows for a detailed, yet efficient simulation of the mechanical seta behavior. A numerical relaxation technique is introduced to handle the jump‐off‐contact instability that can occur in pull‐off computations. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An Enriched Biphasic Model for Solute Driven Degradation
Authors: Ricken T. , Bluhm J. , Epple M. , Wehmöller M. , Annen T.
Published: March 2010

Transport of solutes in porous materials plays an important role in many kinds of materials such as biological tissues, porous implants or even soils. In most of the cases the liquid phase in the pores acts as a solvent for one or more solutions. The motion of the solutions is driven by both, the advective and convective transport. The former is related to the fluid phase velocity whereas the letter follows the concentration gradient. The interactions between the solutes and the solid and liquid phase may influence the overall material behavior. Although the solutes often carry electrical charges this paper is focused on neutrally charged solutions. In this contribution the model to describe the solute transport in a fluid saturated porous material is based on the well founded Theory of Porous Media. We will present the basic framework and the governing equations. Finally, we will show a three dimensional numerical example of the solute driven degradation of a skull implant. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling and numerical simulation of fluid flow induced by the sutureless 3F‐Enable aortic valve
Authors: Hou Guojun , Wendt Daniel , Stühle Sebastian , Tsagakis Konstantinos , Jakob Heinz , Kowalczyk Wojciech
Published: March 2010

Diseases of the aortic valve belong to the most common health problems. The aortic valve maintains the blood flow in one direction and serves to prevent retrograde flow from aorta to the left ventricle. To date, new bio‐prosthetic, suturless heart valves have been designed. The purpose of the present study is therefore to evaluate their influence on hemodynamics in the cardiovascular system. Especially the blood flow in the vicinity of the aortic valve, in the sinus of Valsalva and the ascending aorta becomes on importance from the fluid dynamical point of view. The three‐dimensional geometrical model is generated after segmentation of CT data of the 3F‐Enable aortic valve prosthesis. A set of simulations with different initial velocity profiles and pulse frequencies has been created to examine the transient behavior of the fluid flow and the heart valve prosthesis. The function of heart valve system, however, involves an analysis of fluid‐structure interaction to predict the motion of leaflets. Hence, the separation of the soft tissue and the hard nitinol‐based frame is carried out. The results reveal pressure and velocity distributions as well as normal and shear stresses acting on the wall of the prosthesis and aorta. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental verification of damage detection methods based on mode shape measurements for beams and plates.
Authors: Radzieński Maciej , Krawczuk Marek
Published: March 2010

This paper presents experimental verification and comparison of damage detection methods based on changes in mode shapes such as: mode shape curvature (MSC), damage index (DI), strain energy (SE), modified Laplacian operator (MLO), generalized fractal dimension (GFD) and Wavelets Transform (WT). The object of the investigation is to determine benefits and drawbacks of the aforementioned methods and to develop data preprocessing algorithms for increasing damage assessment effectiveness by using signal processing techniques such as interpolation and extrapolation of measured points. Noise reduction algorithms are also tested. The experiments were performed on a steel cantilever beam and on an aluminium plate with riveted stiffeners. Damage was introduced in a form of open crack for beam object and damaged rivets and a saw cut in the angle bar for plate structure. Measurements were made using non‐contact Scanning Laser Doppler Vibrometer (SLDV) at 125 points along beam length and 101 points in two rows, distributed on over the plate height and positioned along two reinforcing ribs. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Selection of the eddy currents frequency for conductivity measurements in two‐layer structures
Authors: Dziczkowski Leszek
Published: March 2010

Conductance measurements of conductive parts can serve as a background for conclusion about structure of material and possible defects (e.g. fractures, fissures, delamination, flaking, etc.) that may occur in examined parts. When the need arises to test surfaces of parts that are made of a conductive but non‐ferromagnetic material, the method of eddy currents offers unsurpassed advantages. The problem refers to application of the eddy current method to examination of conductive material coated with conductive films. The major outcome consists in development of a very simple and useful mathematical model that can be used to determine conductivity of the deep layer for the needs of non‐destructive tests. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energy driven crack propagation at finite strains based on the embedded strong discontinuity approach
Authors: Radulovic Radan , Bruhns Otto Time , Mosler Jörn
Published: March 2010

New advances in three‐dimensional finite element modeling of crack propagation at finite strains are presented. The proposed numerical model is based on the Enhanced Assumed Strain concept. The enhanced part of the deformation gradient is associated with a displacement discontinuity. In contrast to previous works, a new, energy based criterion for crack propagation is presented. The necessity for a tracking algorithm for the crack path is avoided by using more than one discontinuity within each finite element. This leads to a strictly local formulation, i.e., no information about the neighboring elements are required. Further advantages of such a formulation are a symmetric tangent stiffness matrix and the reduction of locking effects. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase field simulation of thermomechanical fracture
Authors: Kuhn Charlotte , Müller Ralf
Published: March 2010

In Francfort and Marigo's variational free‐discontinuity formulation of brittle fracture [1] cracking is regarded as an energy minimization process, where the total energy is minimized with respect to any admissible crack set and displacement field. No additional criterion is needed to determine crack paths, branching of cracks and crack initiations. However, a direct discretization of the model is faced with significant technical problems, as it involves minimizations in a set of possibly discontinuous functions. A regularized version of the model has been introduced by Bourdin [2] and based on this, we use the concept of a continuum phase field model to simulate cracking processes. Cracks are indicated by the order parameter of the phase field model and cracking can be regarded as a phase transition problem. Additionally, introducing the heat equation into the model, it is capable to also take account of crack propagation due to thermal stresses. In the numerical implementation, crack parameter as well as temperature are treated as additional degrees of freedom and the coupled field equations are solved using the finite element method together with an implicit time integration scheme. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fracture Mechanical Investigation of Elastomeric Material
Authors: Morgner Christiane , Kaliske Michael
Published: March 2010

The increasing use of elastomeric components in advanced engineering applications requires a thorough understanding of the complex material properties and a reliable assessment of the quality and durability of the products. This contribution concentrates on the computational determination of fracture mechanical parameters for rubber material using the material force method. For dissipative, inelastic material, a distinction between two fracture mechanical parameters is presented. The time‐dependent behaviour of these fracture mechanical parameters is illustrated by an application to the dwell‐effect. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of short crack propagation using a hybrid boundary element technique
Authors: Kübbeler Martin , Fritzen Claus‐Peter , Roth Ingmar , Christ Hans‐Jürgen , Krupp Ulrich
Published: March 2010

Service life of cyclically loaded components is often determined by the propagation of short fatigue cracks, which is highly influenced by microstructural features such as grain boundaries. A two‐dimensional model to simulate the growth of such stage I‐cracks is presented. The crack is discretised by dislocation discontinuity boundary elements and the direct boundary element method is used to mesh the grain boundaries. A superposition procedure couples these different boundary element methods to employ them in one model. Varying elastic properties of the grains are considered and their influence on short crack propagation is studied. A change in crack tip slide displacement determining short crack propagation is observed. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparison of ductile damage models with application to LCF
Authors: Kintzel Olaf
Published: March 2010

In the present research work, the modification of the microvoid damage model of Gurson by Leblond et al. is considered using a common framework of multiplicative finite strain elastoplasticity. The formulation for an advanced kinematic hardening model for cyclic plasticity is outlined. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Compressor Blade Health Monitoring with Use of Tip Timing and Modal Analysis Method
Authors: Witos Miroslaw , Wisnioch Marcin
Published: March 2010

The intended aim of this report is to deliver a short review of AFIT experience in the field of the blade health monitoring. A special attention has been put down for diagnostic methods (tip timing, modal analysis, metal magnetic memory) and symptom verification. Knowledge, which is necessary for reliable diagnosis and prognosis, during engine operation, as well as during overhaul and numerical simulation. It has been proven that the resonance characteristic shape analysis gives an ability to determinate if we deal with fatigue or with a blade crack. Early fatigue symptoms, i.e. modal properties of material strengthening and weakening phases have been shown. A new source of diagnostic information to ‘actively’ control blade fatigue (VHCF, HCF & LCF) has been described. The discussed problems have been illustrated with some examples. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Comparison of Alternative Space‐Time Discretizations of Nonlinear Shells
Authors: Sänger Nicolas , Betsch Peter
Published: March 2010

Geometrically exact shell models are suitable for modelling shell‐type flexible components in the context of finite‐deformation multibody dynamics. Conserving time‐stepping schemes are known to yield enhanced numerical stability properties. This approach is compared to alternative methods, including a momentum‐symplectic variational integrator. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling issues of a holistic finite element approach in the virtual engineering design process
Authors: Barthel Corinna , Gabbert Ulrich
Published: March 2010

In the paper methods for the coupling of different meshed local domains of a product model, which occur in an adaptivity process are compared. The properties of the applied coupling methods are demonstrated on finite element models from structural mechanics to point out the advantages and disadvantages of the methods in a model adaptivity process in the field of automotive engineering. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear third‐order shear deformation theory and finite element simulation of smart plates with piezoelectric layers
Authors: SCHMIDT Ruediger , VU Thang Duy
Published: March 2010

This paper deals with nonlinear finite element analysis of plates incorporating piezoelectric layers. The finite elements are based on von Kármán‐type first‐ and third‐order transverse shear deformation theory (FOSD and TOSD, respectively). The presented finite element implementation is based on a total Lagrangian approach. As an example we consider shape control of a hinged plate with PZT actuator layers bonded to the top and bottom surfaces. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polygonal finite element formulations for 2d linear‐elastic FE problems
Authors: Kraus Markus , Steinmann Paul
Published: March 2010

Polygonal finite elements provide great flexibility meshing complex structures and for the refinement of meshes. The actual task in the development of these elements is to offer adequate and secure numerical results compared with regular finite elements at low computational costs. Particulary, finding an efficient and appropriate interpolation of the arbitrary element domain exhibits strong difficulties. Based on the general interpolant equation three element formulations are shown that use different interpolation strategies. The elements' performances are shown with a numerical example considering 2d linear elasticity. The results of the different element formulations are compared among each other, with analytical as well as with regular elements' results. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modes of transition from imperfection sensitivity to imperfection insensitivity
Authors: Mang Herbert A. , Hoefinger Gerhard , Jia Xin
Published: March 2010

In order to a priori find the mode of conversion of a structure from imperfection sensitivity to insensitivity in the course of sensitivity analysis of the initial postbuckling path (cf. [2]), terms appearing in the consistently linearized eigenvalue problem (cf. [1]) are studied. Two main classes can be identified (cf. [4]). The first one is characterized by the restriction of the prebuckling deformations to axial deformations. For this class, the quality of the aforementioned conversion is better than the one for the other class, for which the above restriction does not hold. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stability of thin walled structures strongly coupled with contact
Authors: Izi Ridvan , Schweizerhof Karl , Konyukhov Alexander
Published: March 2010

Stability problems strongly coupled with contact are examined using different contact algorithms. Applying the penalty formulation a high dependence of the buckling load on the penalty parameter is found. This observation becomes clear when considering a classical Euler case. Applying kinematical constraint conditions (close to a Lagrange scheme) for contact on the other hand more consistent results regarding the buckling load are obtained. Thus for a Nitsche scheme a better and more flexible solution is expected. The FE implementation of a Nitsche interface element is carried out. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Free vibrations of thin annular plates made from functionally graded material
Authors: Wirowski Artur
Published: March 2010

Subject of the consideration is thin annular plate made of a two‐phase functionally graded composte. The plate has periodically inhomogeneous microstructure slowly varying in space: the λ‐periodic structure along circular coordinate, but smoothly graded apparent (averaged) properties in the perpendicular, radial direction. The aim of the contribution is to derive and apply a deterministic macroscopic model describing the free vibrations of this plate. Modeling procedure is based on tolerance averaging technique. We received, equations system with smooth coefficients. We made numerical solution of this problem, using finite difference method, and analyze influence of material proportion and microstructure size on first frequency of free vibrations. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reduced hybrid model of moving and rotating continua
Authors: Orlikowski Cezary , Hein Rafał
Published: March 2010

The paper introduces the method of the model reduction of systems that experience a Coriolis acceleration or gyroscopic effect component. In such causes that corresponding system equations are non‐self‐adjoined. Modal reduced model is built up for the system without Coriolis or gyroscopic effect terms. These phenomena are next included by application of any lumping technique. Hence, the final reduced model is a hybrid one, obtained by both lumping and modal methods of modeling. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micro‐vibrations of thin cylindrical shells with uniperiodic structure
Authors: Tomczyk Barbara
Published: March 2010

Micro‐vibrations of thin linear‐elastic Kirchhoff‐Love cylindrical shells, having a periodic structure along one direction tangent to the shell midsurface, are investigated using the new averaged non‐asymptotic model of such shells proposed by Tomczyk (2008). This model describes the effect of microstructure size on the overall shell behaviour and makes it possible to analyze the shell's micro‐dynamics independently of its macro‐dynamics. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Damped vibrations of the beam systems in rotational transportation
Authors: Żółkiewski S.
Published: March 2010

The major aim of this thesis is dynamical analysis of systems in rotational transportation with taking into consideration in the mathematical models the damping forces. The dissipation of energy in form of damping is inseparable connected with motion of analyzed systems. Up to now modelling of rod and beam systems in transportation was very often based on simplification and reduction of damping effect and on the other side the considerations very rarely apply to systems where the transportation effect was took into consideration. In this thesis the dynamical flexibility of the damped beam systems in transportation was presented. Analyzing systems were assumed as simple homogenous beam systems with symmetrical cross‐section constant on whole length of the system. Most popular technical applications of such systems are put into use in propellers and sails of wind power plant, main, auxiliary rotors of helicopters, turbines, etc. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Disturbance Propagation in the Melt Spinning Process
Authors: McVeigh Anthony
Published: March 2010

This work deals with the propagation of a disturbance acting on a fibre in the melt‐spinning process, where molten polymer is ejected vertically downwards from an orifice before being drawn onto a wind‐up spool. The disturbance may be produced by a sudden horizontal draught of air impinging on a part of the fibre. The flow is modeled as a wave propagating on a moving string under the influence of damping and variable tension. The amplitude of the disturbance is obtained in closed‐form along the characteristics which emanate from the boundaries of the localised initial disturbance; the general solution of the damped disturbance is determined numerically. An important aspect of the model is the ability to predict the magnitude of this disturbance close to the orifice, where the extruded polymer is molten and therefore extremely sensitive to disturbances. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear stability analysis of rotor‐bearing systems
Authors: Boyaci Aydin , Seemann Wolfgang , Proppe Carsten
Published: March 2010

High‐speed rotors supported by floating ring bearings exhibit beside self‐excited vibrations various nonlinear vibration effects, which may cause the damage of the rotor. After deriving the equations of motion of a perfectly balanced turbocharger rotor supported by floating ring bearings, bifurcation analyses are carried out with both rigid and flexible model by applying numerical continuation methods. Thereby, the main focus of the investigation is on the critical bifurcations emanating destructive limit‐cycle oscillations of higher amplitudes. Finally, the influence of the shaft elasticity on the critical limit‐cycle oscillations is discussed. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical modelling and analysis of high frequency dynamic contact in the hybrid transducer type ultrasonic motor
Authors: Weerayuth Nantawatana , Seemann Wolfgang
Published: March 2010

The finite element model for describing the intermittent contact dynamics between the stator and the rotor of a hybrid transducer type piezoelectric ultrasonic motor is presented. The contact simulations are performed using an augmented Lagrangian method to determine the normal contact force, the interface condition between the stator and the rotor as dependency of the other factors such as pre‐load force on the stator, the thickness of friction layer, the electrical driving voltage and the operational frequency of the stator. Effects of friction layer, both for elastic and viscoelastic frictional materials, are numerically investigated. The numerical results provide some aspects to make the impact that may occur between the contact interface pairs effectively softer. Furthermore, the noncontact phase between the stator and the rotor of this kind of piezoelectric ultrasonic motor will also be optimized. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An ultrasonic motor with intermittent contact modeled as a two degree of freedom oscillator in time domain
Authors: Wurpts Wiebold , Twiefel Jens
Published: March 2010

The driving mechanism of standing wave ultrasonic motors is basically caused by changing contact states: as the tip of the motor describes an ellipse a tangential force drives an object during contact. The tip moves back without contact and hence produces a resulting driving force. Although ultrasonic motors are known for several decades, the contact description is still topic of ongoing research. As an extension of previous models the trajectory of the tip is not impressed but part of a dynamic structure. An elementary model is proposed using a two degree of freedom oscillator with one mass and a moving ground representing the driven body. The contact forces are given in differential form for stick, slip and separation. The oscillator is simulated for different frequencies, normal contact forces and ground velocities in time domain. The results show a nonlinear frequency behavior and in some configurations stable sub harmonic solutions. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Free vibrations and stability of hydraulic cylinder fixed elastically on both ends
Authors: Uzny Sebastian
Published: March 2010

The boundary value problem of the stability and free vibration of a hydraulic cylinder has been formulated and solved in this paper. The considered hydraulic cylinder has been elastically fixed at both ends and loaded by Euler force. An elastical fixation has been modelled by rotational springs. The mentioned above hydraulic cylinder consists of a piston rod and cylinder replaced by rods. There are conditions of continuity between the rods. The boundary value problem has been formulated on the basis of minimum potential energy (static problem) and on the basis of Hamilton's principle (free vibration problem). In this paper example results of numerical calculations of the stability and free vibration have been presented. Experimental research has been performed in order to verify the correctness of the assumed mathematical model. Professional measuring apparatus and special stand for research into the slender systems have been used in experiment. Natural frequencies have been measured in dependence on the values of an external load. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the role of dislocation conservation in higher‐order crystal plasticity
Authors: Hirschberger C. B. , Peerlings R. H. J. , Brekelmans W. A. M. , Geers M. G. D.
Published: March 2010

The interactions between individual dislocations contribute significantly to size effects as observed at the plastic deformation of miniaturized structures. When employing a crystal plasticity framework, these interactions are usually captured by an additional balance relation. In this paper we study two approaches to capture dislocation interactions in crystal plasticity that differ by the conservation of dislocations. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strength Analyses of Laminated Composite Structures Based on Different Theories
Authors: Wilde R. , Ostwald M.
Published: March 2010

Modern materials, such as composite ones, slowly replace conventional materials in structures of different kind and their growing popularity is caused by their multiple advantages. Through selection of parameters, such as number of layers, thickness of layers, direction of arranging fibers, or material from which internal and outside layers are made, it is possible to control properties of a structure. In the result, structures made of composite materials have high ratio of flexural stiffness to weight. The goal of this paper is to compare three theories of laminated composite plates and shells with the help of the multilayered rectangular plate model subjected to crosswise pressure perpendicular to the surface of a plate. Comparison was made for the classical laminated theory (CLT), first‐order laminated theory and third‐order laminated theory (TSDT). In all these theories, the number of parameters describing the displacement doesn't depend on the number of layers. For each of these theories strains and displacements were determined. Additionally, the computations time for every method were compared. Obtained results are presented in the form of tables. The analysis of the obtained solutions will be used as the base in choosing the best theory in multicriteria optimization process of composite thin‐walled structures. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constitutive Modeling of Rubber Behavior with an Application to Dynamics of Rolling Tires
Authors: Suwannachit Anuwat , Nackenhorst Udo
Published: March 2010

Mechanical response of technical rubbers is described by nonlinear elastic deformation, damage and hysteretic behavior under quasi‐static cyclic loading conditions, while dynamic stiffening and viscous effects are predominant for high frequency analysis. For the computation of the vibration of rolling tires, a material description incorporating all of these effects is needed. A constitutive model for filled rubbers under low frequency excitation is presented. A good agreement between the computational results and experimental data is also presented here. Furthermore, an idea to extend the constitutive model into a broad frequency domain is suggested through the uncoupled kinematic response in linear and nonlinear part. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Towards variational constitutive updates for finite strain plasticity models based on non‐associative evolution equations
Authors: Mosler Jörn
Published: March 2010

In this contribution, first steps towards variational constitutive updates for finite strain plasticity theory based on non‐associative evolution equations are presented. These schemes allow to compute the unknown state variables such as the plastic part of the deformation gradient, together with the deformation mapping, by means of a fully variational minimization principle. Therefore, standard optimization algorithms can be applied to the numerical implementation leading to a very robust and efficient numerical implementation. Particularly, for highly non‐linear, singular or nearly ill‐posed physical models like that corresponding to crystal plasticity showing a large number of possible active slip planes, this is a significant advantage compared to standard constitutive updates such as the by now classical return‐mapping algorithm. While variational constitutive updates have been successfully derived for associative plasticity models, their extension to more complex constitutive laws, particularly to those featuring non‐associative evolution equations, is highly challenging. In the present contribution, a certain class of non‐associative finite strain plasticity models is discussed and recast into a variationally consistent format. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The conservation energy principle in description of stable and unstable states for aluminium
Authors: Wegner T. , Kurpisz D.
Published: March 2010

In the paper the physical model based on the energy conservation principle is proposed. On the basis of this principle the division of energy on volumetric and deviatory parts is presented. In this model a concept of energy division is recognised as important. Using the strain energy density function we can formulate criteria of the material equilibrium stability. Considerations are carried out for aluminium. All assumptions are based on uniaxial tension test supported by transverse deformation measurements. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling and Simulation of Curing Processes of Epoxy Resin
Authors: Yagimli Bülent , Lion Alexander
Published: March 2010

During the curing reaction, the adhesive changes its thermomechanical material behaviour from a viscous fluid to a viscoelastic solid. This phase transition is an exothermal chemical reaction which is accompanied by thermal expansion, chemical shrinkage and changes in temperature. In this work the numerical simulation of the curing process will be presented. The material model for the implementation is presented in [1]. For the implementation of the material model the consistent tangent operator has been derived. In the presentation, experimental data and simulation are shown. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micromechanical Modeling of Woven Fiber Composites for the Construction of Effective Anisotropic Polyconvex Energies
Authors: Ebbing Vera , Schröder Jörg , Neff Patrizio , Gruttmann Friedrich
Published: March 2010

In computer simulations where constitutive equations are considered polyconvex energies can preferably be used because the existence of minimizers is then automatically guaranteed. In this work we investigate the capability to simulate woven fiber composites using polyconvex energies. A virtual experiment of the microstructure of the considered composite is performed and the results are used for the specification of an effective macroscopic anisotropic polyconvex model. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On The Formulatio and Numerical Implementation of Dissipative Electro‐Mechanics at Large Strains
Authors: Rosato Daniele , Miehe Christian
Published: March 2010

In the last year an increasing interest in functional materials such as ferroelectric polymers and ceramics has been shown. For those materials viscous effects or electric polarizations cause hysteresis phenomena accompanied with possibly large remanent strains. This paper outlines aspects of the formulation and numerical implementation of dissipative electro‐mechanics at large strains. In the first part, we focus on the geometric nature of dissipative electro‐mechanics. In a second part, we discuss constitutive assumptions which account for specific problems arising in the geometric nonlinear setting. This concerns the definition of objective energy storage and dissipation functions with suitable symmetries and (weak) convexity properties. With regard to the choice of the internal variables entering these functions, a critical point are kinematic assumptions. Here, we investigate the multiplicative decomposition of the local deformation gradient into reversible and remanent parts as well as the introduction of a remanent metric. In a third part, we summarize details of the constitutive updates as well as the finite element formulations, both on the basis of compact incremental variational principles. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Configurational–Force–Based Adaptive Methods in Nonlocal Gradient‐Type Inelastic Solids
Authors: Welschinger Fabian , Miehe Christian
Published: March 2010

We propose a configurational‐force‐based framework for h‐adaptive finite element discretizations of solids with nonlocal, gradient‐type constitutive response. Typical applications are related to gradient‐type damage mechanics, strain gradient plasticity and regularized brittle fracture. On the theoretical side, we outline a general incremental variational framework for the multifield problem of gradient‐type dissipative solids, where generalized internal variable fields account for the current state of evolving microstructures. The Euler equations of the multifield variational principle define the macroscopic balance of momentum along with balance‐type evolution equations for the generalized internal variables in the physical space as well as the balance of configurational forces in the material space. We propose a staggered computational scheme for satisfying those balances in both the physical as well as the material space. The coupled micro‐ and macro‐structural balances of momentum and internal variables provide a solution in the physical space for a given finite element mesh. The balance in the material space is then used to provide an indicator for the quality of the finite element mesh and accounts for a subsequent h‐type mesh refinement. Such a configurational‐force‐based approach provides in a natural and unified format mesh refinement indicators for a broad class of complex nonlocal problems. This framework is applied to damage‐type regularized brittle fracture. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling of viscoelastic material behaviour close to the glass transition temperature
Authors: Johlitz Michael , Diebels Stefan , Lion Alexander , Possart Wulff
Published: March 2010

In this contribution we investigate the mechanical behaviour of polyurethane over a range of different but constant temperatures from the glass to the viscoelastic state. Therefore uniaxial tension tests are performed on dogbone specimens under different isothermal conditions. In this manner an experimental data set is provided. As a theoretical basis we present the well known thermomechanically coupled one dimensional linear viscoelastic material model which is able to display the experimentally observed material behaviour. For this we adopt temperature dependent relaxation times. The introduced model parameters are identified via a standard parameter identification tool. Finally, the experimental results are compared with the ones of simulations of the identified model parameters. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A finite element model for laminated piezoelectric shell structures
Authors: Legner Dieter , Klinkel Sven , Wagner Werner
Published: March 2010

Thin piezoelectric laminates are used for a wide range of technical applications. A four‐node piezoelectric shell element is presented to analyse such structures effectively. In case of bending dominated problems incompatible approximation functions of the electrical and mechanical fields cause incorrect results. In order to overcome this problem the finite element formulation is based on a mixed variational principle implying six independent fields: displacements, electric potential, strains, electric field, mechanical stresses and dielectric displacements. This allows for an interpolation of the strains and the electric field in thickness direction independent of the bilinear interpolation functions. A piecewise quadratic approach for the shear strains in thickness direction and the corresponding electric field is proposed for arbitrarily layered shells. Regarding coupling of electrical and mechanical fields this yields to an appropriate balance of the approximation functions. Numerical examples show more precise results in contrast to standard elements with lowest order interpolation functions. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic finite deformation viscoelasticity and energy‐consistent time integration
Authors: Müller Melanie , Groß Michael , Betsch Peter
Published: March 2010

In the present work we deal with the conserving integration of viscoelastic bodies undergoing finite deformations.

Isotropic viscoelastic materials can be described by using a symmetric viscous internal variable ${\cal C}_i$ for measuring the inelastic strains, and the right Cauchy‐Green tensor $\cal C$ as measure of the total strain (see Reese & Govindjee [1]). Then, by using the unsymmetric product tensor ${\cal C} {\cal C}_i^{-1}$, the purely elastic strains enter the isotropic free energy function. Alternatively, the i application of the symmetric right stretch tensor ${\cal U}_i$ as internal variable allows to define a symmetric elastic strain tensor ${\cal C}_e$ which enters the free energy (see also Miehe [2]). These two different approaches lead to different evolution equations for the viscous internal variable.

In this lecture, both evolution equations are discretised by an ordinary midpoint rule at each Gauss point of a standard nonlinear displacement‐based finite element in space. For discretising the semidiscrete Hamilton's equations of motion in time, we use numerical time integrators which preserve the fundamental conservation laws of the underlying system. In particular, we make use of a modified midpoint rule according to the discrete gradient method, proposed in Gonzalez [3]. Numerical examples demonstrate the difference between both formulations. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermo‐mechanical behaviour of X‐ray masks in micro system technology
Authors: Körner Claudia , Seemann Wolfgang
Published: March 2010

In the field of micro system technology, the fabrication of micro structure components is on the cusp to industrial production due to economical competition and the necessity to innovate technology. Regarding the X‐Ray lithography process (LIGA), an X‐Ray radiation passes through a mask in form of a membrane with extremely high intensive synchrotron radiation. This leads to locally high temperatures and thus to an inhomogeneous and unsteady deformation in the mask and in the resist. Though, necessary for the production process, this concentration of energy is contradictory to the demand of quality. The goal of this paper is to present a first simplified model of the exposure step in a finite‐element program in order to get a tool providing an optimization of the temperature rise. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermomechanically coupled modeling and simulation of aluminum alloys during hot forming processes
Authors: Parvizian Farhad , Kayser Tobias , Svendsen Bob
Published: March 2010

The aim of this work is thermomechanically coupled simulation and modeling of material behavior and microstructural evolutions during metal forming processes such as extrusion. The material model is implemented as an UMAT in the Finite Element (FE) software ABAQUS. The microstructre parameters such as subgrain size, misorientation and dislocation density are considered as internal state variables. Some of the results of the applied model are presented. The simulation results are in good agreement with experimental observations. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermodynamic Modelling of Defect Migration in Ferroelectric Materials
Authors: Goy Oliver , Mueller Ralf , Gross Dietmar
Published: March 2010

Motivated by the phenomenon of electric fatigue, point defects and their interaction in ferroelectric material are studied with a focus on the tendency of clustering. The underlying continuum model takes into account the full anisotropic electromechanical material properties. Isotropic and anisotropic defect descriptions and their influence on defect interaction will be compared. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Proof of Positive Definiteness of FI and Extended Finite Element Tearing and Interconnecting XFETI
Authors: Sadeq Obaid Abdulrahman , Reese Stefanie
Published: March 2010

We propose a mathematical theorem to prove the positive definiteness of the term FI used in Finite Element Tearing and Interconnecting introduced by Farhat [1]. Furthermore, we introduce a new idea to extend FETI to include non‐self adjoint operators emerging from, for example, elastoplastic large deformation, non‐associative plasticity or when coupling BEM and FEM [2]. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Freezing and thawing processes in porous media – Experiment and Simulation
Authors: Bluhm Joachim , Ricken Tim , Bloßfeld Wolfgang Moritz
Published: March 2010

In this paper, a ternary macroscopic model has been presented with respect to the simulation of freeze‐thaw cycles in liquid filled porous media. Regarding the detection of energetic effects during the phase transition a modified ansatz for the supply term of mass was discussed. The illustrated results of the example show that the simplified model is capable to predict experimental observations. Especially, the influence of the heat of fusion could be realized in an efficient manner. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Geometrical Aspects of the Incorporation of Free Space in Magnetomechanics at Finite Strains
Authors: Kiefer Björn , Rosato Daniele , Miehe Christian
Published: March 2010

This paper addresses the modeling of finite magnetoelasticity with a particular focus on the incorporation of free space energy storage and magnetic body forces. First, a coordinate‐invariant formulation of an extended Neo‐Hookean model with magnetostrictive coupling is presented. Then, a finite element model for finite magnetomechanics based on a variational stationarity principle is formulated. The influence of magnetic body forces is studied in an exemplary boundary value problem. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The discrete‐continuous model of the one‐dimension vibrating mechatronic system
Authors: Buchacz Andrzej , Płaczek Marek
Published: March 2010

This work presents the analysis of the flexural vibrating one‐dimension mechatronic system – the cantilever beam and the piezoelectric transducer bonded with the beam's surface by means of a connection layer. The external RC circuit is adjoined to the transducer's clamps. Dynamic equations of motion of the considered mechatronic system were written down using discrete – continuous mathematical model, taking into consideration the influence of the connection layer and the external electric circuit. The dynamic flexibility of the mechatronic system was assigned on the basis of the approximate Galerkin's method. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of the Chain‐Like Non‐Linear Multi‐Degree‐of‐Freedom Systems Constant Parameters under Dynamical Complex Loads
Authors: Bocian M. , Jamroziak K. , Kulisiewicz M.
Published: March 2010

A determination of mechanical properties of the real material systems under dynamical excitations is a very complex problem. The real system can be described by continuous model as well as a discrete model with a finite number of degree‐of‐freedom. Some mechanical systems like beams, rods, strings, tow‐lines etc. have so‐called chain‐like configuration and may be treated as the dynamical one‐dimensional cascade systems. In this paper, an identification method of internal interaction force, which can be arbitrary selected in discrete chain‐like non‐linear system, is presented. The method was tested on example of a two‐mass system in which the interaction forces were modeled by spring‐damper elements in a non‐parallel arrangement. In experiment some non‐sinusoidal complex loads were applied. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A reformulation of the Jiles‐Atherton hysteresis model for ferromagnetic/ferroelectric components
Authors: Müller Andreas
Published: March 2010

The original Jiles‐Atherton model for modeling hysteresis in ferroelectric media relates the magnetization, or likewise the magnetic polarization, and the magnetic field strength. Since discrete dimensional electromechanical systems are usually modeled using the flux formulation the Jiles‐Atherton model is not applicable in its original form. In this contribution a reformulation in terms of the magnetic flux density is presented. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)