bluuebunny/crossref_metadata_2025_split huggingface dataset:
An alternative perspective on the concept of stress in classical continuum mechanics
Authors: Eugster Simon R. , Glocker Christoph 
Published: October 2016

AbstractWithin a variational formulation of continuum mechanics, as proposed for instance by Germain [1], the internal virtual work contribution of a continuum is postulated as a smooth density integrated over the deformed configuration of the body. In this smooth density the stress field appears as dual quantity to the gradient of the virtual displacement field. Since the mathematical definition of the volume integral naturally provides a macro‐micro relation between infinitesimal volume elements and the continuous body, we propose in this paper an alternative definition of stress on the micro level of the infinitesimal volume elements. In particular, the stress is defined as the internal forces of the body that model the mutual force interaction between neighboring volume elements. The existence of the stress tensor on the macro level is then obtained from the summation of all virtual work contributions within the body, followed by a limit process in which the volume elements are sent to zero. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A computational two scaled model for the simulation of micro‐heterogeneous low‐alloyed TRIP steels
Authors: Gandhi Ashutosh , Prüger Stefan , Balzani Daniel 
Published: October 2016

AbstractIn transformation induced plasticity (TRIP) steel a diffusionless austenitic‐martensitic phase transformation induced by plastic deformation can be observed, resulting in excellent macroscopic properties. In particular low‐alloyed TRIP steels, which can be obtained at lower production costs than high‐alloyed TRIP steel, combine this mechanism with a heterogeneous arrangement of different phases at the microscale, namely ferrite, bainite, and retained austenite. The macroscopic behavior is governed by a complex interaction of the phases at the micro‐level and the inelastic phase transformation from retained austenite to martensite. A reliable model for low‐alloyed TRIP steel should therefore account for these microstructural processes to achieve an accurate macroscopic prediction. To enable this, we focus on a multiscale method often referred to as FE2 approach, see [6]. In order to obtain a reasonable representative volume element, a three‐dimensional statistically similar representative volume element (SSRVE) [1] can be used. Thereby, also computational costs associated with FE2 calculations can be significantly reduced at a comparable prediction quality. The material model used here to capture the above mentioned microstructural phase transformation is based on [3] which was proposed for high alloyed TRIP steels, see also e.g. [8]. Computations based on the proposed two‐scale approach are presented here for a three dimensional boundary value problem to show the evolution of phase transformation at the microscale and its effects on the macroscopic properties. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A consistent implementation for inelastic materials in an ALE formulation for steady state rolling contact
Authors: Garcia Mario A. , Kaliske Michael 
Published: October 2016

AbstractThe numerical analysis of rolling contact for rubber materials is a challenging task, especially due to the many nonlinearities inherent to the material, large deformations, friction, and energy dissipation, among others. Industrial applications can be found in ball bearings, rollers, and most commonly in tires of vehicles, applications where reliable numerical simulations lead to the improvement of durability, performance and safety. While a transient analysis stands as a practical and powerful tool for the simulation of rotating bodies, the large amount of computational resources required represents its biggest disadvantage. An alternative frequently used lays in a steady state simulation by means of an Arbitrary Lagrangian Eulerian (ALE) formulation, where the rotational velocity and axial loads are assumed to remain constant. Within this framework, the reference configuration is neither attached to the material particles nor fixed in space and special attention should be paid to the history variables of inelastic materials. In this work, a viscoelastic material model is implemented in an in‐house finite element code, based on a generalized Maxwell model. The implementation takes into consideration the contribution of all elements connected in circumferential direction and a consistent linearization is made for each of them, leading to an assembled stiffness matrix with more non‐zero values than a standard one. This approach is combined with smeared reinforcement embedded in base elements. The reinforcing layers are described by a hyperelastic material model, providing additional advantages for the modeling and simulation of reinforced rollers and tires. Numerical results for different examples show the capabilities of this implementation and the efficiency of the numerical algorithms is discussed. Important remarks and an outlook for further research concludes this presentation. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effective heat conduction of short fibre reinforced materials considering the fibre distribution
Authors: Goldberg Niels , Ihlemann Jörn 
Published: October 2016

AbstractThis contribution focuses on the effective heat conductivity of short fibre reinforced materials. For this purpose, a representative volume element (RVE), which is able to represent all possible fibre orientation distributions, is introduced and modelled in ABAQUS. Subsequently, the effective heat conductivity of the RVE is derived, employing a numerical homogenisation scheme, and a phenomenological material model is fitted to those results. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental and numerical investigation of metal foams undergoing large deformations
Authors: Heinze Stephan , Jung Anne , Diebels Stefan , Düster Alexander 
Published: October 2016

AbstractOpen cell aluminum metal foams are a new kind of material that are used in composite structures to reduce their weight, to increase their sound or energy absorption capability or to decrease their thermal conductivity. The design and analysis of such structures requires a macroscopic constitutive model of the foam that has to be determined by various experiments under different loading conditions. We support this procedure by analyzing the microstructure of the metal foam numerically under large deformations. To this end, we employ the finite cell method that can deal with large deformations and allows for an automatic and efficient discretization of the CT‐image of the foam. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micromorphic Homogenisation of a Porous Medium: Application to Size Effects and Quasi‐Brittle Damage
Authors: Hütter Geralf , Skrypnyk Rostyslav 
Published: October 2016

AbstractThe classical theory of continuum mechanics requires that distances over which gradients occur are much larger than the length scales of the microstructure. This requirement is violated if deformation localizes due to material softening which is why the predictions of classical damage models feature certain unrealistic aspects. In the present contribution, a micromorphic model for quasi‐brittle damage, derived through homogenisation, is employed in FEM simulations to overcome this problem. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of thick adhesive layers at finite strains utilizing an associated flow rule in a thermodynamically consistent framework
Authors: Kieser Florian , Klinkel Sven 
Published: October 2016

AbstractThe application of elastoplastic material models is commonly used for the modelling of adhesive layers with high strength adhesives as realized with polyurethane or epoxy resin. To fulfill thermodynamic consistency often restrictions on the choice of material parameters are requested. One of them is the introduction of a non‐associated flow rule, which always ensures positive dissipation. Nevertheless, this assumption is a non‐essential criterion, which will be addressed in this work. Continuing along this argumentation, the constitutive relations for the material is modified based on an associated flow rule. The applied model for the simulation of the adhesives is based on a small strain theory. A yield surface including two stress invariants, the hydrostatic pressure as well as the deviator stress state, set the elastic limit of the material response. Linear as well as exponential hardening is incorporated and material softening that arises subsequently is also included by substituting effective invariants in the yield function. This material model as proposed from literature was extended to finite strain application with the concept of generalized stress‐strain‐measure, which was realized in a previous work. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of microstructural pattern formation in crystal plasticity
Authors: Klusemann Benjamin 
Published: October 2016

AbstractThe mechanical behavior of most materials is dictated by a present or emergent underlying microstructure which is a direct result of different, even competing physical mechanisms occurring at lower length scales. In this work, energetic microstructure interaction via different non‐convex contributions to the free energy in metals is modeled. For this purpose rate dependent gradient extended crystal plasticity models at the glide‐system level are formulated. The non‐convex energy serves as the driving force for the emergent microstructure. The competition between the kinetics and the relaxation of the free energy is an essential feature of the model. Non‐convexity naturally arises in finite‐deformation single‐slip crystal plasticity and the results of the gradient model for this case are compared with an effective laminate model based on energy relaxation. Similarities as well as essential differences are observed and explained. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Null‐Lagrangians and the indeterminate couple stress model
Authors: Neff Patrizio , Ghiba Ionel‐Dumitrel , Madeo Angela , Münch Ingo 
Published: October 2016

AbstractThe aims of this note is to present a new model based on a new representation of the curvature energy in the indeterminate couple stress model and to discuss some related choices from the literature. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling the quasi‐static mechanical behavior of the extensible worm‐like chain in the finite‐element framework
Authors: Schulz Matthias , Böl Markus 
Published: October 2016

AbstractA new modeling approach for the force‐extension behavior of polymers and the solution scheme within the finite‐element framework are presented. More specifically, the first variation of the energy function of an initially curved and extensible worm‐like chain [1] and a geometrically exact beam‐element formulation [2] were used to validate the model performing an optimization procedure [3]. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental and Numerical Study of Polypropylene/Polyethylene Thin Foil in Biaxial Tension
Authors: Sguazzo Carmen , Betz Sebastian , Hartmann Stefan 
Published: October 2016

AbstractThe material under consideration is a thermoplastic copolymer blend of polypropylene and polyethylene (PP/PE), constituting the core layer of a steel/polymer/steel composite material. A biaxial loading machine was developed for studying the behavior of the copolymer subjected to in‐plane complex stress states. A study on the shape of the specimen by means of numerical finite element simulations and preliminary experimental tests are carried out, in order to obtain a maximization of the strain distribution in the middle region of the cruciform specimen. Afterwards, the sensitivity of the mechanical response under both equibiaxial and non‐equibiaxial conditions is addressed. All the experiments are monitored by means of a digital image correlation (DIC) system, providing full‐field measurements of the displacements, and, consequently, of the strain distribution. The presented experimental results will be used for validating the material model developed for the PP/PE layer material. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A mesoscale approach for dislocation density motion using a Runge‐Kutta discontinuous Galerkin method
Authors: Schulz Katrin , Wagner Lydia , Wieners Christian 
Published: October 2016

AbstractIn this note, the issue of numerical diffusion in the context of a dislocation based continuum formulation is addressed. Using a geometrical description of dislocation lines and their averages based on a higher order configuration space, a kinematic continuum model is presented for the evolution of curved dislocation lines. In order to include the physical interactions occuring between dislocation lines, an accurate numerical description of the dislocations represented by different quantities of dislocation density has to be ensured. By applying a finite volume scheme as well as a discontinuous Galerkin scheme to a simple benchmark problem, we compare the two numerical methods and discuss the results in the context of dislocation based plasticity. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental and numerical investigation of granular materials for an increase of the collision safety of double‐hull vessels
Authors: Woitzik Christian , Chaudry Moshin Ali , Wriggers Peter , Düster Alexander 
Published: October 2016

AbstractIn the present contribution lightweight granulate like expanded glass will be considered as crash absorbing material in ship constructions. The granules were originally not intended for this application purpose, therefore the material behaviour for this load case has to be determined. To this end, the granulate is compressed in an aluminium cylinder to less than half of its initial height. Based on this experiment, the expanded glass is modelled as Mohr‐Coulomb material within a nonlinear finite element simulation and the parameters of the constitutive equations are identified from the experimental data. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Viscoelastic‐viscoplastic‐damage modeling of thermoplastics under long‐term cyclic loading
Authors: Zerbe Patrick , Schneider Benjamin , Kaliske Michael 
Published: October 2016

AbstractThermoplastics tend to creep under mechanical loads and recover deformation during unloading. A viscoelastic‐viscoplastic‐damage model is presented to accommodate the behavior of a thermoplastic under cyclic loading‐unloading. Finite element simulations may be computationally expensive in case of many loading cycles. A cycle jump method is proposed to mitigate parts of the cost. It can efficiently approximate large parts of the cyclic calculations by extrapolating internal variables over several cycles at once. Hence, only a fraction of the original computational effort remains. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational bridge aeroelasticity using turbulence models
Authors: Alfarra Anas , Dinkler Dieter 
Published: October 2016

AbstractLong‐span bridges may collapse due to the interaction of turbulent wind flow and structural motion. The investigation of the fluid‐structure interaction requires appropriate models for the structure, the wind flow and the coupling between them. Modeling and simulation of the wind flow is still a challenging aspect. The aim of this paper is to show the application of Reynolds Averaged Navier‐Stokes (RANS) equations with a turbulence model in the context of bridge aeroelasticity. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fluid Structure Interaction of Blood Vessels in Circle of Willis
Authors: Alimi Aria , Wünsch Olaf 
Published: October 2016

AbstractThis work involves studying the role of the Brain Blood Barriers (BBB) on damping the stress applied on brain tissue through blood pressure that is the main cause of brain aneurysm. The numerical simulations are focused on the geometry of the Anterior Communicating Artery (ACoA) because there is a 30 % higher probability for a brain aneurysm in this location. A linear elastic model is used to model the structure part including BBB and brain tissue. Regarding the fluid properties, blood is assumed to behave as a Newtonian fluid. The stress and deformation of the brain tissue is analyzed. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A polyconvex strain‐energy split for a high‐order phase‐field approach to fracture
Authors: Bilgen Carola , Hesch Christian , Weinberg Kerstin 
Published: October 2016

AbstractThis contribution focuses on a novel phase‐field model for a high‐order phase‐field approach to brittle fracture in the range finite deformation. In particular, two different challenges are tackled in this study: First, we want to establish a polyconvex free energy density to ensure the existence of a minimizer for the coupled problem, second, we have to deal with a fourth‐order Cahn‐Hilliard type equation for the approximation of the phase‐field.Phase‐field methods employ a variational framework for brittle fracture and have proven to predict complex fracture patterns in two and three dimensional examples. Basis of the model are the conjugate stresses of the three strain measures deformation gradient (line map), its cofactor (area map) and its determinant (volume map). The introduction of the tensor cross product simplifies the presentation of the first Piola‐Kirchhoff stress tensor and its derivatives in elegant manner.The proposed Cahn‐Hilliard type equation requires global
${\cal C}^1$
‐continuity. Therefore, we apply an isogeometric framework using NURBS basis functions. Moreover, a general hierarchical refinement scheme based on subdivision projection is used here for one, two and three dimensional simulations. This technique allows to enhance the approximation space using finer splines on each level but preserves the partition of unity as well as the continuity properties of the original discretization. We finally demonstrate the accuracy and the robustness with a series of benchmark problems. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of Extrinsic and Autonomous Self‐Healing phenomena within the Framework of the Theory of Porous Media
Authors: Bluhm Joachim , Specht Steffen , Schröder Jörg 
Published: October 2016

AbstractIn this work a multiphase model is presented to describe the damage and healing behavior of a self‐healing microstructure. In this academic example a single microcapsule is enclosed in a polymeric matrix. Attention is payed to the outflow of the liquid healing agents from the capsule into the damaged area and the subsequent phase transition from liquid to solid. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Towards the Embedding of Relaxation‐based Magnetostriction Models into a Micromagnetically‐Motivated Finite Element Framework
Authors: Buckmann Karsten , Kiefer Björn , Bartel Thorsten , Menzel Andreas 
Published: October 2016

AbstractIn this contribution we present a variational framework which is suitable for the finite element implementation of energy‐relaxation based magnetostriction models. Our recent work [1] has shown that energy‐relaxation based models are able to capture all key response characteristics of multi‐ferroic magnetic shape memory alloys (MSMA). In order to simulate the response behavior of arbitrarily shaped samples we are switching to a micromagnetically inspired finite element framework [3], where the magnetization inside the magnetic material and the nonlocal demagnetization field are spatially resolved. First results compare the magnetization responses for FE‐simulations and calculations using the demagnetization tensor concept. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling Grain Coarsening in the Framework of Rational Extended Thermodynamics
Authors: Kertsch Lukas , Helm Dirk 
Published: October 2016

AbstractGrain growth and shrinkage at elevated temperatures is a significant phenomenon during the processing of metals. Often, grain coarsening is described without thermodynamic considerations. But since the grain boundary mobility is thermally activated and energy stored in the grain boundaries is released during their motion, a thermodynamic framework is required to capture the various effects of the process. For this purpose, the procedure of Rational Extended Thermodynamics is applied to derive a thermodynamically consistent model for grain coarsening due to the growth and shrinkage of individual grains. Despite the different approach used, a grain growth model is obtained which is similar to existing ones and can be regarded as a thermodynamic extension of that by Hillert (1965) to more general systems. The model reproduces grain growth experiments in pure copper very accurately and predicts the associated energy release. The present approach combining a microstructure description and continuum mechanics can be further used to develop thermomechanical material models considering the microstructure. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gradient based enhanced finite element formulation for diffuse phase interfaces
Authors: Krauss Matthias , Münch Ingo 
Published: October 2016

AbstractInterfaces between adjacent phases, so‐called domain walls, appear as non‐linear gradients of order parameters in diffuse phase field models. Usually, the interface width is much smaller than the dimension of the simulated region. Since the position of domain walls is not known a priori the maximum size of finite elements needs to be adapted to the length scale of interfaces within the entire region. We suggested a selective finite element method to improve the numerical solution of diffuse phase field models [1, 2]. It enhances the finite element interpolation space using supplementary local degrees of freedom. However, corresponding additional nodes are strictly located in the interior of elements, thus, C0‐continuity at element border is guaranteed. Since C0‐continuity limits the performance of this method we propose in this paper a relaxation of C0‐requirements perpendicular to the gradient of the order parameter. Therefore, the direction of interfaces is analyzed as additional information for further adaptive improvement of the interpolation space. A dual phase field model is used to validate the proposed method. The analytical solution of a stationary domain wall allows error analysis of regular and distorted finite element meshes. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A three‐dimensional model of hydraulic fracturing
Authors: Luo Chenyi , Ehlers Wolfgang 
Published: October 2016

AbstractHydraulic fracturing, also known as “fracking”, is a common technology in the oil and gas industry. In practice, adequate fissures and cracks are generated in the stratum by injecting the fracking fluid consisting of multiple chemicals. As a result, more oil and gas are released and later extracted from the outflow. To describe the fracking process, the interaction between the soil and the fracking fluid is an important task. Another challenge comes from the description of the crack propagation, especially in the three‐dimensional case. The proposed model is based on the Theory of Porous Media (TPM), which offers a modern approach to model the biphasic, namely solid‐fluid, material. In order to simulate the crack propagation, an order parameter is included in the constitutive equations. The evolution of the order parameter is related to the stored energy of the solid. With an increasing order parameter, the stiffness of the solid and the interaction between the solid and fluid are decreasing. Hence, the material is transformed from an intact solid skeleton with a pore fluid to a broken one with a bulk fluid. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)