bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimal bounds from below of the critical load for elastic solids subject to uniaxial compression
Authors: Castellano Anna , Foti Pilade , Fraddosio Aguinaldo , Marzano Salvatore , Piccioni Mario Daniele 
Published: October 2015

AbstractIn the recent papers [1,2] we studied a new procedure based on the Korn inequality for determining sufficient conditions for the Hadamard stability, aimed at determining optimal lower bound estimates for the critical load in bifurcation problems. Here, we discuss the effectiveness of our approach for the classical representative problem of uniaxial compression of a Mooney‐Rivlin circular cylinder. We find that our lower bound estimate is effective and advantageous for applications, since it is easily implementable in numerical codes. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On fast and accurate modelling of distributed fibre directions in composites
Authors: Goldberg Niels , Ihlemann Jörn 
Published: October 2015

AbstractThis contribution presents an alternative approach for the consideration of distributed fibre directions in a composite, which is almost as accurate as the solution of angular integrals but considerably faster. It makes use of representative directions according to an Angular Central Gaussian distribution function and does not require the solution of angular integrals. As the choice of the representative directions bears a significant impact on the accuracy of the method, a study on the integration error is presented. Furthermore, the results of homogeneous deformations using the already existing methods as well as the new approach are compared to each other, pointing out the advantages and disadvantages of each method. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling the evolution of microstructures in finite plasticity
Authors: Günther Christina , Junker Philipp , Hackl Klaus 
Published: October 2015

AbstractKochmann and Hackl introduced in [1] a micromechanical model for finite single crystal plasticity. Based on thermodynamic variational principles this model leads to a non‐convex variational problem. Employing the Lagrange functional, an incremental strategy was outlined to model the time‐continuous evolution of a first order laminate microstructure. Although this model provides interesting results on the material point level, due to the global minimization in the evolution equations, the calculation time and numerical instabilities may cause problems when applying this model to macroscopic specimens.In order to avoid these problems, a smooth transition zone between the laminates is introduced to avoid global minimization, which makes the numerical calculations cumbersome compared to the model in [1]. By introducing a smooth viscous transition zone, the dissipation potential and its numerical treatment have to be adapted. We obtain rate‐dependent time‐evolution equations for the internal variables based on variational techniques and show as an example single slip shear. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical analysis of Ni/Al hybrid metal foams using the finite cell method
Authors: Heinze Stephan , Chen Zhaoyu , Jung Anne , Diebels Stefan , Düster Alexander 
Published: October 2015

AbstractAluminium metal foams are a new type of material that can be used in many lightweight applications. One method to improve their mechanical properties is to coat them with a thin layer of nickel by electrodeposition. A voxel representation of this hybrid foam can be obtained in a straightforward way using a CT scanner. The voxel‐based geometry can then be processed and modified with respect to the thickness of the nickel layer in order to investigate its influence on the effective properties. By employing the finite cell method (FCM) we are able to automatically convert the voxel‐based geometry into a finite cell grid and to directly perform a homogenization procedure. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the natural Fiber (Maize) Composite material
Authors: Ilie Ruxandra , Chiroiu Veturia 
Published: October 2015

AbstractThis work is focused on the compressive behavior in the elastic region of a composite material made out of stalk‐based maize fiber and unsaturated polyester resin polymer as matrix with methyl ethyl ketone peroxide as a catalyst and Cobalt Octoate as a promoter [1]. Deformation and fracture behavior are investigated by using Extended Finite Element Method (XFEM). XFEM enables the accurate approximation of solutions with jumps, discontinuities or general high gradients across interfaces between the fibers and the matrix [2], [3]. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The perturbation method applied to tube drawing with floating plug
Authors: Ioan Rodica , Ioan Stefan 
Published: October 2015

AbstractThe determination of the load on the machine tool is crucial in the mechanics of metal forming processes as it has a critical influence over the deformation of the material into a new shape and the optimal conditions for the process. The problems of strip, wire, tube drawing without plug, tube drawing with floating plug [1‐4] viscoplastic deformation has no exact solutions, but this paper addresses them using an approximate method. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rank‐One Convexification Approach for the Modeling of Magnetic Shape Memory Response
Authors: Buckmann Karsten , Kiefer Björn , Bartel Thorsten , Menzel Andreas 
Published: October 2015

AbstractWe present an incremental energy minimization model for magnetic shape memory alloys (MSMAs) whose derivation departs from the constrained theory of magnetoelasticity [1], but additionally accounts for elastic deformations, magnetization rotation, and dissipative mechanisms. The minimization of the proposed incremental energy yields the evolution of the internal state variables. In this sense, the presented modeling concept clearly distinguishes itself from standard phenomenological approaches to MSMA modeling [4]. The extended model is applied to simulate the response of single crystalline Ni2MnGa. It is shown to accurately capture the nonlinear, anisotropic, hysteretic, and highly stress level‐dependent features of MSMA behavior, based on just a few fundamental material parameters, which is validated by comparison to experimental data. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Direct connection of rheological elements at large strains: Application to multiplicative viscoplasticity
Authors: Kießling Robert , Landgraf Ralf , Ihlemann Jörn 
Published: October 2015

AbstractIn the field of nonlinear continuum mechanics, rheological models are often used to exemplify the structure of complex material models at large strains. For this purpose, different rheological elements are combined in series and parallel connections. Ihlemann [1] developed an innovative concept, which enables the direct connection of rheological elements within the framework of multiplicative decomposition of the deformation gradient. In the contribution at hand, this approach is applied to multiplicative viscoplasticity. Towards this end, the relations for parallel and series connections are introduced and several individual material models, i.e. the rheological elements, are defined. By analytical and numerical evaluation of the connection relations, a viscoplastic material model from the literature is reproduced. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of material parameters of heterogeneous viscoelastic curing polymers
Authors: Klinge Sandra , Steinmann Paul 
Published: October 2015

AbstractTwo goals characterize the present contribution: First, the development of a numerical approach for determining the properties of the material microstructure, and second, the shift of the focus of the inverse analysis from investigating a purely elastic material toward the parameter identification related to heterogeneous inelastic materials. As a rule, the constitutive laws in this case involve a greater number of material parameters the determination of which requires different kinds of tests. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase‐field modeling of martensitic phase transformations in polycrystals coupled with crystal plasticity – A spectral‐based approach
Authors: Kochmann Julian , Wulfinghoff Stephan , Svendsen Bob , Reese Stefanie 
Published: October 2015

AbstractThe purpose of this work is the phase‐field modeling of fcc‐to‐bcc martensitic phase transformations in polycrystals and the coupling with crystal plasticity. Assuming microscopic periodic fields, Green‐function‐ and fast Fourier transform (FFT)‐methods are used to solve the quasi‐static balance of linear momentum. The Allen‐Cahn evolution equation is discretized based on a semi‐implicit time integration scheme in Fourier space. Two‐dimensional results are presented and the interplay between martensitic phase transformation and plastic slip is studied at different stages of the deformation. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dislocation Structure of Grain Boundaries in Single Crystals Deforming in Simple Shear
Authors: Koster Michael , Le Khanh Chau 
Published: October 2015

AbstractA model for the formation of grain boundaries in single crystals having a single active slip system for the case of plane strain simple shear is proposed. It is shown that non‐convexity of the condensed energy gives rise to the formation of a laminate structure, where sharp interfaces between laminate layers are interpreted as grain boundaries. Based on these results the dislocation structure of the boundaries is determined introducing a transition zone between laminate layers, where smooth functions of displacement and plastic slip connect adjacent layers. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phenomenological modelling for viscohyperelasticity: How to find suitable evolution laws in order to extend hyperelastic models?
Authors: Kröger Nils Hendrik , Juhre Daniel 
Published: October 2015

AbstractMaterials used for adhesive tapes indicate viscohyperelastic behaviour. We presented a model approach for extending hyperelastic material models for viscous effects via an evolution law approach. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of Carbon Fiber Reinforced Plastics for Wave Propagation Analysis in Plates
Authors: Lammering Rolf , Hennings Bianca 
Published: October 2015

AbstractThe modeling of the carbon fiber reinforced plastic (CFRP) for finite element analysis of wave propagation in plates from this material is presented. The random distribution of fibers in the matrix material is considered in a microscale model in order to properly capture the experimentally observed “quasi‐continuous mode conversion” (QCMC). (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of micro cutting considering crystal plastic deformations
Authors: Lohkamp Richard , Kuhn Charlotte , Müller Ralf , Aurich Jan C. , Schneider Frank 
Published: October 2015

AbstractThe micro cutting process of microstructured material is simulated with consideration of the heterogeneities of the microstructure. In the case of cp‐titanium with its hcp crystal structure the basal and prismatic slip systems are taken into account. The concept of crystal plasticity for large deformations is applied considering elastic anisotropy, self and latent hardening. The visco‐plastic evolution law incorporates rate dependent material behavior. This setup is implemented within the finite element method. The effects of the microstructure are demonstrated by an illustrative example and a comparison to an isotropic von Mises elasto‐plastic material. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the sonic composites with scatterers made from auxetic material
Authors: Mo¸ snegu¸ tu Valerica , Donescu Stefania 
Published: October 2015

AbstractA finite size periodic array of resonators made from auxetic material embedded into an epoxy matrix is analyzed in this paper. According to the Bragg's theory, the sound attenuation band is due to the superposition of multiple reflected waves inverse proportional to the central distance between resonators. The sound attenuation in such composites is studied using a method that combines the features of the cnoidal method and the genetic algorithm [1‐3]. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of imperfect contact interfaces in sonic composites
Authors: Munteanu Ligia , Brişan Cornel 
Published: October 2015

AbstractIn this paper, the tangential and normal discontinuities at the interface between the scatterer and the matrix are independently modeled, and these relative displacements are directly proportional to the corresponding components of tractions at the interface. The generation of full band‐gaps is investigated on the basis of the derived imperfect interface conditions for a sonic plate with an array of acoustic piezoceramic hollow spheres scatterers embedded in an epoxy matrix. The scatterers are made from functionally graded materials with radial polarization. Numerical evaluation has shown that imperfect interface may have a significant effect on the increasing of the length of the full band‐gaps. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Modeling of Functional Fatigue in NiTi Wires
Authors: Osman Muhammad , Bartel Thorsten , Menzel Andreas 
Published: October 2015

AbstractMotivated by the high potential of shape memory alloys (SMA) in several industrial applications, we investigate the material response under cyclic loading. In particular, the focus is set on the modelling of functional fatigue, which results in the deterioration of the specific features of SMA. In fact, functional fatigue restricts SMA in terms of its applicability for real structures and workpieces. This necessitates the development of material models which take this phenomenon into account. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A misorientation dependent grain boundary yield criterion
Authors: Prahs Andreas , Bayerschen Eric , Böhlke Thomas 
Published: October 2015

AbstractAn equivalent plastic strain gradient theory, cf. [1], is extended by a GB flow rule, that accounts for the misorientation of adjacent grains. In contrast to previous works, the grain boundary (GB) resistance against plastic flow is not treated as a constant parameter. Therefore, in the work at hand, the grain boundary dislocation density (GBD), cf. [2], is used as a measure for geometrical mismatch between all glide system orientations of two adjacent grains. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constitutive modeling of fiber‐reinforced aerogels
Authors: Rege Ameya , Itskov Mikhail 
Published: October 2015

AbstractAerogels are open‐cell highly porous solids having exclusive properties such as lowest bulk density, lowest thermal conductivity and lowest acoustic velocity. These properties make them useful over a large spectrum of applications. However, their brittle and hydrophilic natures result in a road block which is overcome by polymer or fiber reinforcement. In this study, we are focussing on fiber‐reinforced aerogels which retain the exclusive properties of aerogels mentioned above while giving them a good load bearing strength at the same time. These fiber‐reinforced aerogels show many complex phenomena under loading such as, a strong nonlinearity, cyclic stress softening, and permanent set. However, there have been very few studies on fiber‐reinforced aerogels oriented towards their mechanical characterization. To the best of our knowledge, there also is no micromechanical model that can capture the constitutive response of these fiber‐reinforced aerogels. In this contribution, we propose a micro‐mechanically motivated constitutive model of fiber reinforced aerogels. The prime source of elasticity and damage in these aerogels is the effect of bending and breakage of fibers in the material network. Accordingly, we consider non‐linear bending of fibers supported by an elastic foundation of particles. Based on this concept, the strain energy function is analytically derived for a single fiber in a particular direction. The strain energy of the whole network is then obtained by integration over an unit sphere. The model shows good agreement with experimental data. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of short fiber reinforced polymers
Authors: Röhrig Céline , Diebels Stefan 
Published: October 2015

AbstractThis contribution presents ideas, how composite materials can be characterized with respect to experimental testing. The material properties of the investigated short glass fiber reinforced polymer are obtained by providing results from the experiment in order to seperate different material effects, such as elasticity, plasticity, damage, viscoelasticity, compressibility and anisotropy. Therefore, at first, linear uniaxial tensile tests with cyclic loadings have been realized. The application of the material in this work is the machining by a three‐dimensional forming process. Hence, multiaxial loadings have to be additionally taken into account matching these conditions. In order to provide more information, biaxial tensile tests have to be realized using a testing device supplying the additional necessary experimental data [1, 2]. A final aim of this work is to develope a verification experiment representing the three‐dimensional forming process as realistically as possible, e. g. a Nakajima test [4]. For this case, a three‐dimensional optical analysis in order to get the necessary measurement data, is indispensable to realize an inverse method [3] by comparing the information of the complete deformation field as well as the force data of the experiment using a given material model. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterisation of filled rubber with a pronounced non‐linear viscoelasticity
Authors: Scheffer Tobias , Goldschmidt Florian , Diebels Stefan 
Published: October 2015

AbstractThis contribution presents the characterisation of an incompressible carbon black‐filled elastomer as one characteristical example for highly filled rubber. It shows a strongly pronounced non‐linear viscoelastic behaviour and the most important characteristic is the extremely long relaxation time which has to be taken into account. The material model is developed with respect to uniaxial tension data. The basis in the development of a phenomenological model is given by the basic elasticity. For this evaluation the long term relaxation behaviour results in a complex experimental procedure. Therefore, special attention has to be paid according to an optimised experimental process in order to get the necessary reference data in an adequate and reproduceable way [1].With this model basis further investigations are taken into account concerning the time‐dependent viscoelasticity. Therefore, cyclic deformations from zero up to a maximum of deformation are considered for different strain rates. Furthermore, the relaxation behaviour is investigated for multiple strain levels. The phenomena which are observed in the experimental results yield in a purely viscoelastic model, based on a rheological analogous model consisting of an equilibrium spring and several Maxwell‐elements which contain nonlinear relations for the relaxation times of the dashpot elements [1,2].The material model's numerical realisation is accomplished in two ways. Because of its numerical simplicity especially according to the parameter identification the model is restricted only to the simple case of uniaxial tension. A second, alternative implementation is executed providing the benefit that more complex deformation conditions can also be taken into account. Therefore, the general, three‐dimensional finite model is implemented in an open‐source Finite Element library [3]. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inverse Parameter Identification for Orthotropic Elasto‐Plastic Sheet‐Steel
Authors: Söhngen Benjamin , Willner Kai 
Published: October 2015

AbstractIn this contribution the Finite Element Model Updating (FEMU) approach is utilized to determine the material parameters of sheet‐steel. From experimental testing it is observed that the considered cold‐rolled steel exhibits orthotropic behaviour. To regard this in the simulation, a user‐implemented material model based on a quadratic yield function is used. Via the method of digital image correlation (DIC), the displacement field of a biaxially loaded specimen is measured from images taken at different stages of loading. Comparing the experimentally determined displacements to those obtained by simulation an error measure is defined which can be minimized by optimization algorithms. Starting with initial values for the orthotropic elasto‐plastic material parameters, the FEM model is thus updated consecutively until a specified error margin is reached. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
External boundary value problems of steady vibrations in the theory of rigid bodies with a double porosity structure
Authors: Svanadze Merab 
Published: October 2015

AbstractThis paper concerns with the linear 3D theory of rigid solids with a double porosity structure. Basic external boundary value problems (BVPs) of steady vibrations are formulated. The uniqueness and existence theorems for regular (classical) solutions of these BVPs are established. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Automatic Implementation of Elasto‐plastic Incremental Formulations at Finite Strains using Hyper‐Dual Numbers
Authors: Tanaka Masato , Balzani Daniel , Schröder Jörg 
Published: October 2015

AbstractNumerical simulation of standard dissipative materials undergoing finite strains remains an important and challenging topic in computational mechanics. The incremental variational formulation (IVF), firstly proposed by Ortiz et al. [1], provides a general variational framework which is suitable for the implementation of a broad range of constitutive laws for standard dissipative materials. The IVF recasts the inelasticity theory as an equivalent optimization problem where the incremental stress potential is minimized with respect to the internal variables. However, their implementation often requires more effort than classical formulations due to high‐order tensor derivatives. In this contribution, a novel implementation of IVFs is presented to arrive at a fully automatic and robust scheme with computer accuracy using hyper‐dual numbers (HDNs). The HDNs, which are originally developed by Fike [2], derive exact and automatic derivative calculations without any cumbersome choice of perturbation values. Its uncomplicated implementation for associative finite strain elasto‐plasticity and its performance is illustrated by a representative numerical example. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A micromechanical model for the transformation induced plasticity in polycrystalline steels
Authors: Waimann Johanna , Junker Philipp , Hackl Klaus 
Published: October 2015

AbstractDue to the effect of transformation induced plasticity (TRIP) , TRIP‐steels are very promising materials, e.g. for the automobile industry. The material behavior is characterized by very complex inner processes, namely phase transformation coupled with plastic deformation and kinematic hardening. We establish a micromechanical model which uses the volume fractions of the single phases, the plastic strain and the hardening parameter in every grain of the polycrystalline material as internal variables. Furthermore, we apply the Principle of the Minimum of the Dissipation Potential to derive the associated evolution equations. The use of a coupled dissipation functional and a combined Voigt/Reuss bound directly results in coupled evolution equations for the internal variables and in one combined yield function. Additionally, we show numerical results which prove our model's ability to give a first prediction of the TRIP‐steels' complex material behavior. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)