bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sensitivity analysis of weakened beams on elastic foundation with Green's functions
Authors: Schwartpaul Kai , Zhang Chuanzeng , Carl Oliver 
Published: December 2012

AbstractThe approach of Sensitivity Analysis with Green's Functions (SAGF) [1,2] was developed to predict changes in deformations, stresses or eigenfrequencies of structures resulting from stiffness modifications or cracking by considering only the weakened or damaged parts of the structures. This approach results in a local analysis instead of a global analysis by recalculating the whole structure. Consequently, it is computationally less time‐consuming than the conventional methods based on a global analysis. The key idea of the SAGF approach is based on the comparison between the elastic strain energies of the original and the weakened structures and the substitution of the virtual displacements by the corresponding Green's functions [1, 2].Furthermore, an approximate approach for the sensitivity analysis was suggested which is described in [1, 3] in details. This approach enables us to predict the changes in the structural responses due to the stiffness weakening in the beam or in the elastic Winkler foundation by considering only the internal forces or the deflections of the original unweakened system. In addition, an iterative method was developed to enhance the accuracy of the SAGF approach.In this paper, the local SAGF method for sensitivity analysis of elastic beams on Winker foundation with stiffness weakening is presented. The accuracy and the efficiency of the proposed method are verified by using a numerical example. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Oscillations of a channel with a flexible wall conveying viscous flow
Authors: Bach Karolina , Hetzler Hartmut , Seemann Wolfgang 
Published: December 2012

AbstractThe interaction between a flexible structure and flowing fluid can cause flow‐induced vibrations and the steady state may loose stability by divergence or flutter, thus leading to undesirable dynamic behaviour.As a model for fluid‐structure‐interaction a planar channel guiding a flowing fluid is studied. It can be shown that for thin channels the coupling effects are strong [1] and therefore the focus of this contribution is to investigate the behaviour of a channel, where the structural displacements are non‐negligible compared to the gap width. Due to this comparatively large amplitudes a linear description of the interface between fluid and structure will not be sufficient anymore and the relation between the Eulerian description of the fluid and the Lagrangian description of the structure must be taken into account: eventually, this yields nonlinear boundary conditions. Furthermore in narrow gaps the viscosity of the fluid cannot be ignored [2]. Hence the effect of viscosity will also be considered within this contribution. In order to allow for analytical results and keep the focus on the effects due to the moving interface, the fluid flow is modelled using lubrication theory. The linear stability of the steady state ist investigated as well as the influence of the inherent nonlinearities of the coupled problem. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Network evolution model: thermodynamics consistency, parameter identification and finite element implementation
Authors: Khiêm Vu Ngoc , Dargazany Roozbeh , Navrath Uwe , Itskov Mikhail 
Published: December 2012

AbstractIn this contribution, the previously proposed network evolution model [1] for carbon black filled elastomers is further studied. First, we show that the model does not contradict the second law of thermodynamics and is thus thermodynamically consistent. On the basis of new experimental data the influence of filler concentration on the material parameters is further examined. Accordingly, this influence concerns only three material parameters and is approximated by phenomenological relations. These relations enable one to simulate rubbers based on the same compound with various filler concentrations. Finally, the model is implemented into the FE‐Software ABAQUS and illustrated by a number of numerical examples. The examples demonstrate good agreement with experimental results with respect to the Mullins‐Effect, permanent set and induced anisotropy. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Shakedown analysis of periodic composites with kinematic hardening material model
Authors: Chen Min , Hachemi Abdelkader , Weichert Dieter 
Published: December 2012

AbstractLower‐bound limit and shakedown analysis of periodic composites with the consideration of kinematic hardening are carried out on the representative volume element level. In combination with homogenization theory, the homogenized macroscopic admissible loading domains are determined. Furthermore, the strengths of periodic composites by using elastic perfectly plastic, unlimited and linear limited kinematic hardening material models are calculated and compared. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of phase‐transformations based on numerical minimization of intersecting Gibbs energy potentials
Authors: Ostwald Richard , Bartel Thorsten , Menzel Andreas 
Published: December 2012

AbstractWe present a novel approach for the simulation of solid to solid phase‐transformations in polycrystalline materials. To facilitate the utilization of a non‐affine micro‐sphere formulation with volumetric‐deviatoric split, we introduce Helmholtz free energy functions depending on volumetric and deviatoric strain measures for the underlying scalar‐valued phase‐transformation model. As an extension of affine micro‐sphere models [5], the non‐affine micro‐sphere formulation with volumetric‐deviatoric split allows to capture different Young's moduli and Poisson's ratios on the macro‐scale [1]. As a consequence, the temperature‐dependent free energy assigned to each individual phase takes the form of an elliptic paraboloid in volumetric‐deviatoric strain space, where the energy landscape of the overall material is obtained from the contributions of the individual constituents. For the evolution of volume fractions, we use an approach based on statistical physics–taking into account actual Gibbs energy barriers and transformation probabilities [2]. The computation of individual energy barriers between the phases considered is enabled by numerical minimization of parametric intersection curves of elliptic Gibbs energy paraboloids. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Steady vibrations problem in the theory of viscoelasticity for Kelvin‐Voigt materials with voids
Authors: Svanadze Maia M. 
Published: December 2012

AbstractIn this paper the linear theory of viscoelasticity for Kelvin‐Voigt materials with voids is considered. The uniqueness and existence theorems for internal boundary value problem (BVP) of steady vibrations are proved by means of the potential method (boundary integral method) and the theory of singular integral equations. The application of this method to the 3D BVP of the considered theory reduces this problem to 2D singular integral equation. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carbon Fibre Prepregs: Simulation of a Thermo‐Mechanical‐Chemical Coupled Problem
Authors: Hankeln Frederik , Mahnken Rolf 
Published: December 2012

AbstractIn automotive industry research is done to replace high strength steel by combinations of steel and carbon‐fibre prepregs (pre‐impregnated fibres). It is planned to form both steel and uncured prepregs in one step followed by the curing process under pressure in the forming die. The ability to simulate the mechanical behaviour during forming and curing would allow more economical processes. The simulation of prepregs must regard highly anisotropic, viscoelastic and thermal‐ chemical properties. For this the model is split into an anisotropic elastic part, which represents the fibre fraction and an isotropic, viscoelastic part, representing the matrix. This part also contains curing, causing a dependency on time and temperature. During deep‐drawing large deformations are occurring, so a large strain model regarding anisotropy, viscoelasticity and curing has been developed. Also experiments were made to validate this model. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of nanoindentation experiments by means of rheological models
Authors: Müller Wolfgang H. , Worrack Holger 
Published: December 2012

AbstractThe nanoindentation technique is established in the field of material characterization at small dimensions. It is daily practice to analyze nanoindentation data with an almost “classical” formula based on the publications by Oliver and Pharr and Fischer‐Cripps. The procedure works well for elastic‐time independent plastic material behavior, for example copper and the calibration material fused silica, even at higher test temperatures. However, low melting solder materials are susceptible to creep behavior. For this reason, additional analysis procedures are required to determine the material parameters more precisely. In this paper the authors want to give an introduction to an “enhanced” analysis of nanoindentation data based on rheological models, which are often used to describe the time‐dependence of material response. Two examples of such models are the MAXWELL‐ and the KELVIN‐body. The authors present a rheological model, published by Mencik in 2011 [1], in context with the corresponding equation which is used to extract the material properties from the recorded data. Results of the analysis at the calibration material fused silica are presented and discussed together with the material parameters published in the literature. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computation of material forces for the thermo‐mechanical response of dynamically loaded elastomers
Authors: Behnke Ronny , Kaliske Michael 
Published: December 2012

AbstractElastomers are widely used in today's life. The material is characterized by large deformability upon failure, elastic and time dependent as well as non‐time dependent effects which can be also a function of temperature. In addition, cyclically loaded components show heat build‐up which is due to dissipation. As a result, the temperature evolution of an elastomeric component can strongly influence the material properties and durability characteristics. Representing best the real thermo‐mechanical behaviour of an elastomeric component in its design process is one motivation for the use of sophisticated, coupled material approaches within numerical simulations. In order to assess the durability characteristics, for example regarding crack propagation, material forces (configurational forces) are one possible approach to be applied. In the present contribution, the implementation of material forces for a thermo‐mechanically coupled material model including a continuum mechanical damage (CMD) approach is demonstrated in the context of the Finite Element Method (FEM). Special emphasis is given to material forces resulting from internal variables (viscosity and damage variables), temperature field evolution and dynamic loading. Using the example of an elastomeric component, for which the material model parameters have been previously identified by a uniaxial extension test, material forces are evaluated quantitatively. The influence of each contribution (internal variables, temperature field and dynamics) is illustrated and compared to the overall material force response. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale modelling and simulation of micro machining of titanium
Authors: Lohkamp Richard , Müller Ralf , Schneider Frank , Aurich Jan 
Published: December 2012

AbstractThe microscale morphology of micro machined component surfaces is directly connected to the heterogeneous microstructure. The deformation depends on the crystal structure, in case of the considered cp‐titanium, the hcp crystal structure. In a first approach the crystal plastic deformation is modeled with isotropic hardening. A visco‐plastic evolution law accounts for the rate dependency. The concept of configurational forces is used with the framework of crystal plasticity to model the cutting process of cp‐titanium. The setting is implemented into the finite element method. The examples show the effect of the material heterogeneity on the deforamtion behavior and on the related configurational forces. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Material parameter identification using model reduction to uniaxial tensile test
Authors: Krämer Stephan , Rothe Steffen , Hartmann Stefan 
Published: December 2012

AbstractMaterial parameter identification is the necessary link between constitutive modeling and application of material models in complex simulations of real world problems. We present an approach to make use of already developed stress algorithms for three‐dimensional finite‐element computations in terms of a reduction to uniaxial tensile tests for material parameter identification. Strain‐driven stress algorithms lead to the approach of solving differential‐algebraic equations. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A stochastic model for the direct and inverse problem of adhesive materials
Authors: Nörenberg Nicole , Mahnken Rolf 
Published: December 2012

AbstractThis work deals with the generation of artificial data based on experimental data for adhesive materials and the application of this data to the inverse and the direct problem. In reality there are only a very limited number of experimental data available. Therefore, the prediction of material behaviour is difficult and a statistical analysis with a stochastic proved thesis is nearly impossible. In order to increase the number of tests a method of stochastic simulation based on time series analysis is applied.With artificial data an arbitrary number of data is available and the process of the parameter identification can be statistically analysed. Additionally, one example is shown, which adapts the analysed material parameter to the direct problem. The stochastic finite element method is used to take into account the distribution and deviation of the fracture strain. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of induced anisotropy at large deformations for polymers
Authors: Caylak Ismail , Mahnken Rolf 
Published: December 2012

AbstractIn this work we develop a model to describe the induced plasticity of polymers at large deformations. Polymers such as stretch films exhibit a pronounced strength in the loading direction. The undeformed state of the films is isotropic, whereas after the uni‐axial loading the material becomes anisotropic. In order to consider this induced anisotropy during the stretch process, a spectral decomposition of the inelastic right CAUCHY‐GREEN tensor is done. Therefore, the yield function can be formulated as a function of the anisotropic tensor, where again the anisotropic tensor is a function of the maximum eigenvalue. A backward EULER scheme is used for updating the evolution equations, and the algorithmic tangent operator is derived. The numerical implementation of the resulting set of constitutive equations is used in a finite element program and for parameter identification. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Deformation induced martensite transformation in a cold‐worked forming process of austenitic stainless steel
Authors: Dally Tim , Weinberg Kerstin 
Published: December 2012

AbstractWithin the last years the goal of industrial manufacturing processes – such as tube forming – has shifted towards an optimization of technological as well as mechanical properties of the manufactured structures. For example, during the forming procedure of sheets made of austenitic stainless steel X5CrNi18‐10, the content of strain‐induced martensite needs to be controlled. In order to achieve optimal structural properties of the manufactured tube with respect to very high‐cycle fatigue (VHCF), a martensite ratio of approximately 25% needs to be obtained [1].On the basis of experimental investigations this contribution deals with the numerical simulation of the tube‐forming process with special consideration of the martensite ratio c as a function of temperature and deformation field. For this purpose we extend an existing martensite model on polyaxial states of stress and compare experimental results and numerical simulations for the modified model. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A solid‐shell finite element for fibre reinforced composites
Authors: Simon Jaan‐Willem , Stier Bertram , Reese Stefanie 
Published: December 2012

AbstractFibre reinforced composites consisting of several layers, each of which is composed of a woven fabric embedded in a matrix material, are investigated in this paper. Such materials are characterized by a complex anisotropic behavior, which necessitates a fully three‐dimensional formulation of the constitutive equations. On the other hand, they are frequently used in thin shell‐like applications. In order to account for the three‐dimensional material law while still providing the suitable shape for thin structures, a solid‐shell finite element for fibre composite materials is presented herein. Locking phenomena are treated by both the enhanced assumed strain (EAS) concept and the assumed natural strain concept (ANS). Using reduced integration together with hourglass stabilization leads to high computational efficiency. The anisotropic constitutive behavior of the composites is reflected by a micromechanically motivated continuum model, which –together with the solid‐shell formulation– allows for an accurate representation of the through‐the‐thickness stress distribution even for thin structures. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On response functions in linear thermoelastic models of shape memory polymers
Authors: Aydin Aycan O. , Kazakeviciute‐Makovska Rasa , Steeb Holger 
Published: December 2012

AbstractThis paper is concerned with the broad class of Liner Thermoelastic (LTE) models for Shape Memory Polymers (SMPs) which unifies numerous constitutive theories proposed in the literature for this kind of smart material. It is shown that the response functions for the general model of this class may be determined directly from experimental data measured in standard thermomechanical cyclic tests. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A new continuum approach to the coupling of shear yielding and crazing with fracture in glassy polymers
Authors: Schänzel Lisa , Dal Hüsnü , Miehe Christian 
Published: December 2012

AbstractOver the past decades, several constitutive models accounting for finite viscoplasticity and failure in glassy polymers were developed. However, depending on thermal and loading rate conditions, the response might change from ductile to brittle. This brittle response is characterized by inelastically deformed zones, so‐called crazes, having the thickness of micrometers and spanning at some fractions of a millimeter, containing a dense array of fibrils interspersed with elongated voids, detailed discussion e.g. [1]. The shear yielding and crazing are not completely independent excluding each other. Present models introduce crazing either discrete by cohesive surfaces, e.g. [2], or continuous, see [3]. In this work, we outline an extension of a ductile plasticity model towards (i) the description of volumetric directional plasticity effect due to crazing and (ii) the modeling of the local failure due to fracture. The ultimate amount of volumetric plastic craze strain is bounded by a limiting value, where failure occurs. In a second step, the modeling of subsequent failure mechanisms is realized by introducing a fracture phase field, characterizing via an auxiliary variable the crack. Here, we adopt structures of a continuum phase field model of fracture in brittle solids [4], and modify it for a fracture driving term related to the volumetric plastic deformation of the crazes. We demonstrate the performance of proposed formulation by means of a representative boundary value problem. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling and Simulation of Microwave Heating for Spalling of Radioactive Contaminated Concrete
Authors: Melcher Andreas , Lepers Benjamin , Umminger Martin , Kayser Thorsten , Link Guido , Haist Michael , Jelonnek John , Müller Harald 
Published: December 2012

AbstractMicrowave heating is becoming of growing importance in material sciences in the last two decades. Due to the volumetric heating effect, microwave heating offers an energy efficient way of processing materials in several ways. The modeling and simulation of material processing with microwaves with respect to the material structure is a challenging task. The corresponding mathematical modeling results in a coupled, multiscale problem in space and time consisting of Maxwell equations, the heat equation and a temperature‐dependent description of the dielectric properties of them material under investigation. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the flow characteristics of a geothermal plant in a heterogeneous subsurface
Authors: Koch David , Ehlers Wolfgang 
Published: December 2012

AbstractDue to the scarcity of fossil fuel with a simultaneous rising in global energy demand, it is important to gain access to other energy sources. Geothermal energy holds great potential, and has therefore been studied increasingly in recent years. Within the construction of a geothermal plant, a fluid is introduced via a borehole into the initially gas‐filled porous rock. Due the rising pressure gradient, the fluid distributes, displaces the gas and escapes through a second borehole. The modelling approach of these processes in a heterogeneous subsurface proceeds from the Theory of Porous Media (TPM) including an elastically deformable solid, an incompressible fluid, and a gaseous phase [1]. To solve the initial‐boundary‐value problem, the governing primary variables of the strongly coupled three‐phase model are spatially approximated by mixed finite elements, whereas the time‐discretisation is carried out by an implicit Euler time‐integration scheme. The goal of the presented numerical simulations is to study the specific flow characteristics in a heterogenous subsurface. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Approximate Galerkin method applied to an analysis of vibration of continuous mechanical systems
Authors: Płaczek Marek 
Published: December 2012

AbstractPaper presents fundamental assumptions of the approximate Galerkin method application in order to vibration analysis of continuous mechanical systems with different form of vibration and different boundary conditions. Flexural vibration of beams, longitudinal vibration of rods and torsional vibration of shafts with all possible ways of fixing were considered. Analyzed mechanical systems were treated as subsystems of mechatronic systems with piezoelectric transducers. This work was done as an introduction to the analysis of mechatronic systems with piezoelectric transducers used as actuators or passive vibration dampers [1–3]. It is impossible to use an exact Fourier method in this case. This is the reason why the approximate Galerkin method was chosen and analysis of its exactness was done as a first step of this work. Dynamic flexibilities of considered mechanical systems were calculated twice, using exact and approximate methods. Obtained results were juxtaposed and it was proved that in some cases the approximate method should be corrected while in the other it is precise enough. A correction method was proposed and it was assumed that the approximate method can be used in mechatronic systems analysis. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)