bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermodynamically consistent integration of coupled thermoelastic systems
Authors: Schiebl Mark , Betsch Peter , Hesch Christian 
Published: October 2016

AbstractThis work deals with the energy‐momentum‐entropy consistent integration of thermoelastic systems. While energy‐momentum preserving integrators are well‐known for conservative mechanical systems, Romero recently introduced in [6] a thermodynamically consistent (TC) integrator for coupled thermomechanical systems. TC integrators also respect symmetries of the underlying coupled system and are therefore capable of conserving associated momentum maps. A first step towards the systematic design of a TC integrator is to cast the evolution equations into the GENERIC framework. GENERIC stands for General Equation for Non‐Equilibrium Reversible‐Irreversible Coupling and has been originally proposed by Grmela and Öttinger for complex fluids [3]. As a second step applying the notion of a discrete gradient in the sense of Gonzalez [2] leads to a TC integrator. The GENERIC‐based framework reveals additional underlying physical structures of the thermodynamical system due to the separation of irreversible and reversible driving forces. Using the entropy as the thermodynamical state variable as in [4,6] the GENERIC framework yields an easy structure. However, this choice of thermodynamical state variable leads to a restriction in the material model and, more importantly, only allows to prescribe entropy Dirichlet boundary conditions. This drawback can only be compensated by using Lagrange‐multipliers to be able to handle temperature Dirichlet boundary conditions, which unfortunately extends the system of algebraic equations to be solved (see Krüger et al. [5]). Alternatively, the present contribution uses the temperature as the thermodynamical state variable (see also the recent work by Conde Martín et al. [1]). This temperature‐based approach allows to set Dirichlet boundary conditions directly. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of different least‐squares mixed finite element formulations for hyperelasticity
Authors: Schwarz Alexander , Steeger Karl , Igelbüscher Maximilian , Schröder Jörg 
Published: October 2016

AbstractThe main goal of this contribution is the solution of geometrically nonlinear problems using the mixed least‐squares finite element method (LSFEM). An investigation of a hyperelastic material law based on logarithmic deformation measures is performed. The basis for the proposed LSFEM is a div‐grad first‐order system consisting of the equilibrium condition and the constitutive equation, see e.g. Cai and Starke [1]. For the interpolation of the solution variables vector‐valued Raviart‐Thomas functions for the approximation of the stresses and standard Lagrange polynomials for the displacements are used. In order to show the performance of the presented formulations a numerical example is investigated, where we compare the different interpolation combinations used. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational integration in endochronic theory for small strain elastoplastodynamics
Authors: Bär Sebastian , Groß Michael 
Published: October 2016

AbstractThis paper presents a basic endochronic plasticity model with isotropic hardening for small strain theory according to Valanis. The key point of this model is a convolution integral over an intrinsic time scale involving past values of the strain measure and a so‐called memory kernel which leads to a smooth evolution equation for the internal variable. For the temporal discretization of the underlying constitutive equations and the resulting evolution equation we use higher order accurate variational integrators (VI). The remarkable feature is the fact that we approximate the position vector in terms of velocities according to partitioned Runge‐Kutta methods (pRK). As a representative model problem serves a quasistatic, uniaxial tensile testing as well as a dynamic, elastoplastic cantilever beam with a smooth plasticity model according to the Valanis framework. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bifurcation behaviour and limit cycles of a compliant seal‐rotor system
Authors: Baeuerle Simon , Hetzler Hartmut 
Published: October 2016

AbstractThis contribution discusses the non‐linear dynamic behaviour of a rotor system equipped with a compliant seal. The investigated model consists of a Laval‐Rotor and a stiff seal ring which is visco‐elastically supported. The fluid forces stemming from the turbulent incompressible lubricant film are accounted for by the non‐linear Muszynska model. The added compliance leads to an improved stability behaviour of the steady state. Within the post‐critical regime the additional compliance gives rise to bifurcations of the stationary vibration: Hopf bifurcations lead to limit cycles which can loose their stability via Neimark‐Sacker bifurcations. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Conditions for the existence and stability of the regime of type 0/1 for an excited unbalanced rotor
Authors: Bartkowiak René 
Published: October 2016

AbstractStationary regimes of motion of an unbalanced rotor with harmonic base excitation are investigated. The equation of motion of the rotor can be transformed into integro‐differential equations for the so called slow and fast motions of these regimes using the method of direct separation of motion. The existence and stability conditions of special regimes of motion then can be derived by introducing the approximate solutions of the fast equation into the slow equation. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling and simulating a variable displacement vane pump
Authors: Köster Marius , Fidlin Alexander , Schröders Simon 
Published: October 2016

AbstractVariable displacement vane pumps are used in a variety of applications, most prominently in the context of modern automotive vehicles. Minimal models capturing the main dynamic effects of such pumps have remained scarce. In this contribution, a minimal model taking into account the force effects from line pressure exposure and dead volume compression and expansion is presented. The pump model is autonomous and allows for a simple integration in simulation models for which an example in the form of a non‐smooth hydraulic circuit is given. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Validation of the applicability of a creep model for directionally solidified eutectics with a lamellar microstructure
Authors: Albiez Jürgen , Sprenger Ioannis , Weygand Daniel , Heilmaier Martin , Böhlke Thomas 
Published: October 2016

AbstractDepending on the process parameters, the directional solidification (DS) of eutectic alloys leads to a fibrous or lamellar microstructure. A physically motivated creep model which was evaluated for a DS‐eutectic with a fibrous microstructure is applied to a DS‐eutectic with a lamellar microstructure. Creep curves are simulated and compared to experimentally measured ones. It is shown, that the simulation is in good agreement with the experiment. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐quadratic defect energy: A comparison of gradient plasticity simulations to discrete dislocation dynamics results
Authors: Bayerschen Eric , Stricker Markus , Weygand Daniel , Böhlke Thomas 
Published: October 2016

AbstractA small‐deformation strain gradient plasticity (GP) model for single‐crystals has been proposed in [1], including a grain boundary (GB) yield condition without hardening. It has been extended by a hardening term for the GBs after a comparison to discrete dislocation dynamics (DDD) results in [2]. Differences between the strain gradients of the GP results and the DDD results motivate the consideration of a non‐quadratic defect energy [3] in the GP model. It is shown that the gradients in the GP model can be improved using an exponent different from two. Remaining discrepancies in the strain profiles, compared to the DDD results, are attributed to the neglect of the individual gradients of plastic slip and due to the lack of a mechanism for the misorientation‐dependent elastic interactions of dislocations across GBs [4] in the GP model. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transient Finite Element Simulation of the Temperature Field during Cryogenic Turning of Metastable Austenitic Steel AISI 347
Authors: Becker Steven , Mayer Patrick , Kirsch Benjamin , Aurich Jan C. , v. Harbou Erik , Müller Ralf 
Published: October 2016

AbstractThe process chain in manufacturing often consists of many steps. As part of current researches the possibility of combining two process steps, turning and hardening, is investigated to optimize the manufacturing time and to decrease the energy consumption of the process. For metastable austenitic steels, deformation induced hardening during turning can be used to achieve surface hardening [1] and thus to increase the wear resistance [2] as well as the fatigue strength [3], by applying high passive forces onto the workpiece. This enables an austenite‐martensite phase transformation, for which it is necessary to maintain low process temperatures, typically below room temperature. Thus, cryogenic coolants are applied [4].For a better understanding of the influence of cutting parameters on the process temperatures and thus martensite formation, knowledge of the exact temperature distribution in the workpiece and in the contact zone between workpiece and tool is essential. Since the experimental determination of the temperature field is hardly possible, an inverse determination of the process temperatures via transient finite element simulation is performed.The present finite element approach only takes thermal loads into account. The simulations are performed in the finite element program FEAP (Finite Element Analysis Program) with an Eulerian mesh, which requires special consideration of the rigid body rotation of the workpiece. In order to prevent unphysical oscillations in the solution, introduced by the convective time derivative, a streamline upwind / Petrov–Galerkin stabilization scheme is utilized. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Discussion of Different Model Approaches for the Flow Behavior of Ice
Authors: Christmann Julia , Rückamp Martin , Müller Ralf , Humbert Angelika 
Published: October 2016

AbstractIce of Antarctic ice shelves is assumed to behave on long‐term as an incompressible viscous fluid, which is dominated on short time scales by the elastic response. Hence, a viscoelastic material model is required. The thermodynamic pressure is treated differently in elastic and viscous models. For small deformations, the elastic isometric stress for ν → 0.5 gives similar results to those solving for pressure in an incompressible laminar flow model. A viscous model, in which the thermodynamic pressure is approximated by an elastic isometric stress, can be easily extended to viscoelasticity. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An experimentally validated rod model for soft continuum robots
Authors: de Payrebrune Kristin M. , O’Reilly Oliver M. 
Published: October 2016

AbstractSoft robots are bio‐inspired, highly deformable robots with the ability to interact with workpieces in a manner that complements their hard robot counterparts. To develop practical applications and reproducible designs of soft robots, new models are necessary to describe their kinematics and dynamics. In the present work, we describe experimental and numerical investigations of a popular pneumatically‐actuated soft continuum arm. These works enable us to derive constitutive relations and develop a rod model for large deformations of the arm that faithfully describes its bending behavior. We show how the resulting non‐classical constitutive relation can be defined either through experiments or through quasi‐static finite element simulations. With the help of this relation, the resulting rod model can be used to study the dynamics of the soft robot arm in a fast and tractable manner. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A laminate‐based framework for switching and microstructure evolution in polycrystalline ferroelectrics
Authors: Dusthakar Dinesh K , Menzel Andreas , Svendsen Bob 
Published: October 2016

AbstractThis contribution deals with the numerical modelling of polycrystalline ferroelectric materials considering a sequential laminate‐based approach established for tetragonal single‐crystal ferroelectrics. The particular model [1] is considered and extended to predict the material behaviour of poly‐crystal tetragonal ferroelectric ceramics. The derived laminate‐based model is implemented in a finite element environment to simulate the time‐dependent domain evolution and switching response of a bulk polycrystalline ferroelectric ceramic. © 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Large Strain Gradient Plasticity Theory with a Discontinuous Grain Boundary Yield Condition
Authors: Erdle Hannes , Bayerschen Eric , Böhlke Thomas 
Published: October 2016

AbstractAn equivalent plastic strain gradient theory [1] is extended to account for finite strains. The presented model considers discontinuities of the equivalent plastic strain at grain boundaries by using enriched trial functions in the Finite‐Element discretization. As a consequence, a grain boundary flow rule is introduced, depending on both the mean value and the jump of the equivalent plastic strain. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of dilatant plasticity models in application to rubber‐toughened polymers
Authors: Hund Jonas , Naumann Johanna , Seelig Thomas 
Published: October 2016

AbstractThe overall deformation behavior of rubber‐toughened polymers (e.g. PC/ABS blends) exhibits a pronounced plastic dilatancy. As this volume increase results from diverse micromechanisms the appropriate structure of a macroscopic model is not obvious. In this contribution, different material models featuring plastic dilatancy are compared with regard to their ability to capture the deformation behavior of PC/ABS in different loading situations. All models are calibrated to match experimental data under uniaxial tension in terms of true stress‐strain curves and the evolution of volume strain. Afterwards they are employed in finite element (FE) simulations of single‐edge‐notch‐tensile (SENT) tests. Patterns of plastic deformation computed from the different material models are compared to experimental findings. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental investigation, material modeling and parameter identification of a zinc die‐casting alloy
Authors: Martinez Page Maria Angeles , Hartmann Stefan 
Published: October 2016

AbstractThe zinc die‐casting alloy Zamak is widely used in the production of components of cars and machines. Because of its complex highly non‐linear thermo‐mechanical behavior, it is problematic to approximate its response with classical viscoplasticity models, such as von Mises‐viscoplasticity. Based on an extensive experimental investigation on thin‐walled cylindrical specimens, a proposal for the modeling of the rate‐ and temperature‐dependent behavior of the alloy Zamak 5 is presented and its applicability through a numerical example is shown. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of two different modeling approaches to describe the non‐linear viscoelastic behavior of filled rubber material
Authors: Scheffer Tobias , Diebels Stefan 
Published: October 2016

AbstractThis contribution presents the characterisation of an incompressible carbon black‐filled elastomer as one characteristical example for highly filled rubber material. The material model is developed with respect to uniaxial tension data. The experiments show that a strongly pronounced non‐linear viscoelastic material behavior is present and the most important characteristic is the extremely long relaxation time which has to be taken into account. These long relaxation times are also visible in cyclic tests, where a pronounced hysteresis loop appears even for the slowest possible strain rates [1,2].In the material's characterization two different model approaches are realized. As a first approach the behavior is represented by a pure viscoelastic model. Since all the deformations are reversible for a stress‐free relaxation, no plasticity parts are included in the model. In order to display the non‐linearities process‐dependent material parameters have to be applied. Hence, the resulting coupling of different material parameters yields a complex parameter identification.For a more effective identification process, a second approach is provided describing the interaction of the filler particles. The friction of the fillers during deformation results in a statical hysteresis, which does not depend on the strain rate. Therefore, special attention is turned towards the behavior of the hysteresis loops that are observed, similar to the description of Vandenbroucke et al. [3]. Therein, in a rheological model, some Prandtl‐elements, consisting of a friction element and a spring are added to the classical viscoelastic model. This results in a model, which does not need any process‐dependency. Hence, the identification process can be simplified. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐resolution simulation of microstructures in dual‐phase steel
Authors: Scherff Frederik , Goldschmidt Florian , Scholl Sebastian , Diebels Stefan 
Published: October 2016

AbstractModern dual‐phase (DP) steels are widely used in industry due to their favorable material behavior based on the complex microstructure. In the presented work, a microstructure based FEM model for the elasto‐plastic deformation of DP steels is developed in order to accomplish a deeper understanding of the structure‐property correlation. The underlying microstructure is obtained by serial section tomography. The following contribution deals with a comparison of different approaches to build a FE mesh, which is based on such microstructures. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time and frequency domain finite element implementation of a fully anisotropic linear visco‐elastic model
Authors: Toth Florian , Kaltenbacher Manfred 
Published: October 2016

AbstractConsistent time and frequency domain formulations for a fully anisotropic, linear visco‐elastic material model are presented. The finite element implementation leads to a complex valued stiffness matrix in the frequency domain. A homogenisation procedure based on unit‐cell analyses in the frequency domain is presented to derive input parameters for the material model. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Digital Rock Physics: A case study of carbonate rocks
Authors: Uribe David , Saenger Erik H. , Steeb Holger 
Published: October 2016

AbstractDigital Rock physics is a numerical framework applying image‐based methods to determine effective material properties of rock. It is possible to find several of these methods in the literature, but we focused mainly in micro X‐Ray Computed Tomography (µXRCT) to acquire the digital rock samples. After scanning the 3‐D microstructure, morphological filters and numerical simulations were performed to characterize the samples. In particular carbonate rocks present a mismatch in numerical results compared to laboratory experiments. The elastic parameters, the P‐ and S‐wave moduli, respectively,are overestimated when compared to ultrasonic measurements in the laboratory. We describe possible causes of this mismatch and propose a new segmentation technique to improve the correlation between numerical simulations and laboratory data. Furthermore, the workflow proposed for the characterization of carbonate rocks has been applied to different digitized samples from different sources, and a data driven material law has been found that fits better experimental results than the lower Hashin‐Shtrikman bound. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A variational model for the functional fatigue in polycrystalline shape memory alloys
Authors: Waimann Johanna , Junker Philipp , Hackl Klaus 
Published: October 2016

AbstractShape memory alloys show a very complex material behavior associated with a diffusionless solid/solid phase transformation between austenite and martensite. Due to the resulting (thermo‐)mechanical properties – namely the effect of pseudoelasticity and pseudoplasticity – they are very promising materials for the current and future technical developments. However, the martensitic phase transformation comes along with a simultaneous plastic deformation and thus, the effect of functional fatigue.We present a variational material model that simulates this effect based on the principle of the minimum of the dissipation potential. We use a combined Voigt/Reuss bound and a coupled dissipation potential to predict the microstructural developments in the polycrystalline material. We present the governing evolution equations for the internal variables and yield functions. In addition, we show some numerical results to prove our model's ability to predict the shape memory alloys' complex inner processes. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Generalized Interface Models With Damage in Gradient Plasticity
Authors: Wulfinghoff Stephan , Alipour Atefeh , Rezaei Shahed , Kochmann Julian , Reese Stefanie 
Published: October 2016

AbstractGradient plasticity can account for experimentally observed size effects. Here, a previously developed gradient plasticity model is extended to account for interface delamination processes. The crystal plasticity model is based on the gradient of an equivalent plastic strain measure. A modification of the related boundary conditions allows for the formulation of a generalized cohezive zone model which can take into account the effect of interface delamination on the gradient plasticity solution. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Deformed gap space using macro‐micro FEA model and transferred into a CFD model
Authors: Anwar Ali , Gorash Yevgen , Dempster William , Nash David 
Published: October 2016

AbstractUsing a cylindrical nozzle and seat of a Pressure Relief Valve (PRV) the surface form and waviness is modelled using actual metrological data i. e. average surface form and waviness (Wa and Wsm) in a ${1 \over 4}$ symmetry manner. To model the surface waviness the technique used is based on the summing technique created by Tsukizoe & Hisakado [1, 2] for micro contact analysis. Due to the actual surface form measurements being in the micro‐meter range, the model is required to incorporate micro and macro‐meter dimensions. The material in question is stainless steel. The deformed finite element analysis model is then transferred into a CAD geometry allowing the void space to be meshed and solved using computational fluid dynamics. © 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)