bluuebunny/crossref_metadata_2025_split huggingface dataset:
A quasi‐axisymmetric lattice model applied to analyze the vibrational contact between a PTFE shaft seal and a rotor
Authors: Albrecht Florian , Kletschkowski Thomas 
Published: March 2018

AbstractShaft seals shall prevent the leakage of oil and the intrusion of dirt particles in rotating machineries. A loss of contact between shaft and seal results in leakage. In order to ensure the functionality of the sealing system, the followability of the seal needs to be ensured. To analyze this problem, a model of a Polytetrafluorethylen (PTFE) shaft seal is coupled with an unbalanced rotor. PTFE has pronounced viscous and plastic characteristics. This leads – combined with other non neglectable nonlinearities – to a numerically challenging problem. To reduce the complexity and to increase the computational efficiency, the PTFE shaft seal is discretized by a quasi‐axisymmetric lattice model. The results show that loss of contact at rotor speeds close to the eigenfrequency of the rotor (high amplitude) and at high rotor speeds (high frequency) is possible and shall be avoided to prevent leakage. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rotor‐systems with compliant seals: A comparison of the rotordynamics using the Muszynska model and Hirs' lubrication equations
Authors: Bäuerle Simon , Hetzler Hartmut 
Published: March 2018

AbstractThis contribution compares two approaches for modelling seal fluid forces in a rotor system with compliant seal support: on the one hand side the non‐linear ODEs of the Muszynska model are used. On the other hand side Hirs' PDEs for turbulent lubrication flow are numerically integrated and an ODE coefficient model is fitted to this data. Simulations are performed with both fluid models and the results are compared: they show not only quantitative differences in the stability behaviour of the rotor‐system but also qualitative differences in the bifurcation behaviour. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the numerical approximation of invariant manifolds for quasiperiodic motions
Authors: Fiedler Robert , Hetzler Hartmut 
Published: March 2018

AbstractThe interference of oscillations with different physical origins with incommensurable frequencies can lead to quasiperiodic motions. Concerning engineering problems, there is a variety of models which exhibit multi frequent oscillations. This contribution proposes a numerical approach approximating stationary solutions by an invariant manifold. To apply the approach a partitioning of the phase variables is necessary, which defines the parametrisation of a dynamical system. In order to demonstrate the applicability of the proposed method, stationary solutions of an unbalanced Laval‐rotor (Jeffcott‐rotor) are calculated and continued under variation of a control parameter. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimization of Damping for Squeal Avoidance in Disc Brakes
Authors: Jekel Dominic , Hagedorn Peter 
Published: March 2018

AbstractThis paper deals with the optimization of the linear stability behavior of circulatory systems with respect to particularly advantageous damping properties. The technique is demonstrated by applying it to an industrial finite element model of a disc brake in order to reduce the propensity of squeal noise. After decomposing the damping matrix into several component matrices, which may have some special structure or physical relevance, the ratio of these are varied to either stabilize or make more stable the equilibrium state subject to sensible constraints. For the purpose of this study, a system is defined to be more stable if its eigenvalue with largest real part is as negative as possible. For a certain velocity range, it is shown to be beneficial to reduce the material damping in the pads and in the caliper, which might be counterintuitive from an engineer's perspective. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the modelling of curvature effects in fibre‐reinforced nanocomposites
Authors: Asmanoglo Tobias , Menzel Andreas 
Published: March 2018

AbstractMotivated by the progress in nanoengineering over the past years, novel experimental approaches to characterise the material behaviour on the nanoscale have been developed which indicate that the material response on the nanoscale does not have to be identical with the one observed on the macro scale, i.e. size effects occur. However, experiments at the nanoscale are expensive and difficult to conduct, therefore necessitates the development of sophisticated modelling approaches which allow for predictive simulations at these scales. Regarding experimental findings on one‐dimensional nano‐materials presented in e.g. [1], and adopting the higher‐order gradient based modelling framework proposed in [2], the development of a fibre‐curvature based contribution to the stored energy function which results into well‐interpretable contributions to the stress‐ and to the couple stress tensor is presented. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanical Modeling of the Strain‐Induced‐Crystallization in Polymers
Authors: Aygün Serhat , Klinge Sandra 
Published: March 2018

AbstractThe strain‐induced crystallization (SIC) in polymers is a phenomenon manifesting itself as the natural reinforcement caused by the high deformation or by the reduction of the temperature. It is typical for natural rubber, since this material contains more regularly oriented chains than the other polymers. Most of the models focusing on the modeling of polymers use the Langevin expression for the free energy as a basis [1]. The current work, however, treats a polymer affected by the strain induced crystallization as a heterogeneous medium consisting of regions with a different degree of network regularity. Such a concept allows the depiction of the nucleation and the growth of crystalline regions as well as the change of effective material parameters depending on the level of the strain applied. The model proposed is thermodynamically consistent. It is based on the assumptions for the free Helmholtz energy and dissipation potential. The inelastic deformations and degree of the network regularity are internal variables. Their evolution equations are derived according to the minimum principle of the dissipation potential. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Consistency of dynamic recrystallization models from the perspective of physical metallurgy and continuum mechanics
Authors: Bambach Markus , Klinge Sandra 
Published: March 2018

AbstractDynamic recrystallization (DRX) is characterized by the nucleation and growth of new grains, which takes place concurrently to plastic deformation. DRX processes are used in industrial hot forming operations to control the microstructure and properties of the workpiece. Various models have been developed that consider the coupled evolution of microstructure and flow stress during hot deformation processes, some from a perspective of physical metallurgy, some from continuum mechanics. It is widely accepted that the onset of DRX is characterized by an inflection point of the strain hardening rate as a function of stress. This criterion was derived by Poliak and Jonas using results from the thermodynamics of irreversible processes. The present paper analyses the conditions that need to be met by DRX models to be consistent with the criterion by Poliak and Jonas. It is shown that for models which use classical Avrami kinetics to describe the evolution of the recrystallized volume fraction, the Avrami exponent should exceed a value of 3 to ensure that the Poliak‐Jonas criterion is not violated. Based on this observation, a framework for consistent DRX kinetics is presented and discussed. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Towards a micromagnetics‐inspired framework for the modelling of variant switching in magnetic shape memory alloys
Authors: Bartel Thorsten , Kiefer Björn , Buckmann Karsten , Menzel Andreas 
Published: March 2018

AbstractThis contribution deals with a micromechanical model for the simulation of the magnetomechanical behaviour of magnetic shape memory alloys which captures effects such as martensite variant switching, domain wall motion, and the rotations of local magnetisations. It is revealed, however, that the implementation into micromagnetics‐inspired Finite Element schemes cannot be realized in a standard fashion but requires the treatment of state variables via macroscopic fields. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite element modeling of laser beam welding for residual stress calculation
Authors: Herrnring Jan , Klusemann Benjamin 
Published: March 2018

AbstractNumerous welding processes are used in naval, automotive and aircraft industries for joining structural components. Laser beam welding represents a key technology due to his low heat input and the high degree of process automation. Nonetheless, all welded materials are characterised by a strong change of microstructure in the heat effected and fusion zone. For simulation of residual stress fields the finite element method is the most often simulation tool. Reliable simulations have to take into account the changes in microstructure. Within this work, a viscoplastic material model for welding is presented, accounting for the solid and fluid phase, which is extended later on by a simple kinetic model to model precipitation hardening. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale modeling of thermoplastic PC/ABS blends
Authors: Hund Jonas , Seelig Thomas 
Published: March 2018

AbstractRubber‐toughened thermoplastic polymers such as PC/ABS blends exhibit a pronounced plastic dilatancy in their overall deformation behavior which results primarily from damage mechanisms in the ABS phase while PC behaves plastically incompressible, e.g. [1]. In this contribution, two commercial PC/ABS blends of different composition and morphology are approximated through appropriate unit cell models featuring the two constituents PC and ABS as distinct phases. Different visco‐plasticity models are utilized to capture the specific deformation behavior of each phase. Numerical studies of the unit cell models looking at the effect of the blend composition on the overall response are compared with experimental data. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of Gold Microbeams with Higher Order Continuum Theories
Authors: Kandaz Murat , Dal Hüsnü , Ünlü Mehmet 
Published: March 2018

AbstractMicrobeams are building blocks for many microstructures as well as microelectromechanical systems (MEMS) and cannot accurately be modelled by classical continuum theories due to size effects based on their micro‐scale. These size effects can be taken into account by the so‐called higher order continuum theories. Modified Strain Gradient Theory (MSGT) and Modified Couple Stress Theory (MCST) are two commonly used theories, which extend the classical local continuum theories of grade one with the introduction of additional length scale parameters. In this contribution, the variational problem governing the elasticity of higher order beam formulation and the finite element implementation based upon, are briefly introduced. To this end, well known Euler‐Bernoulli beam formulation assumptions are used. The size effect for gold‐micro beams is demonstrated and the length scale parameters of gold microbeams for MSGT and MCST are identified form the existing experimental data from literature for the first time. As a novel aspect, significant size effect is demonstrated for the length‐scales associated with the state of the art gold microbeam structures developed for MEMS applications, which reveals the necessity of the use of higher order theories at these length scales. Advantages and drawbacks of these theories are also identified. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A multisurface model for gradient‐enhanced damage coupled to finite plasticity
Authors: Sprave Leon , Menzel Andreas 
Published: March 2018

AbstractA gradient‐enhanced damage formulation is coupled to isotropic plasticity in the framework of finite strains. Within the finite element method, an additional field variable representing nonlocal damage is introduced and linked to its local counterpart in order to allow a standard local formulation at the material point level. The onset of damage and plasticity is governed by damage and yield criteria respectively. This multisurface approach requires the determination of the two Lagrange multipliers. By using logarithmic strains, a formulation in principal axes in combination with a von Mises yield criterion is implemented. The damage functions are defined by means of exponential functions in order to avoid further constraints on the local damage variable. The model is able to capture a wide range of material responses, ranging from brittle to ductile damage and plasticitiy dominated behaviour. The mesh independence of the model is shown by means of representative finite element examples. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of the Elastic Behaviour of Hybrid‐yarn Reinforced Elastomers using Twisted‐periodic Boundary Conditions
Authors: Storm Johannes , Kaliske Michael 
Published: March 2018

AbstractReinforcements of elastomers using hybrid‐yarns allow to take advantage of the bi‐modular stiffness behaviour of those yarns. The initial deformation behaviour is characterised by low stiffness and the potential for finite deformations. Reaching a certain limit of hybrid‐yarn stretch, the mechanical behaviour changes towards larger stiffness and only allows for small further deformations. In comparison to other yarn reinforcements with finite deformations, the achieved material strength is relatively high. The bending behaviour of the involved yarns is approximated using anisotropic hyperelastic material laws. The efficiency of the applied computational homogenisation method is significantly improved by introducing twisted‐periodic boundary conditions. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
External boundary value problems in the quasi static theory of thermoviscoelasticity for Kelvin‐Voigt materials with double porosity
Authors: Svanadze Maia M. 
Published: March 2018

AbstractIn the present paper the linear quasi static theory of thermoviscoelasticity for Kelvin‐Voigt materials with double porosity is considered. The basic external boundary value problems (BVPs) of steady vibrations in this theory are formulated. The uniqueness and existence theorems for regular (classical) solutions of the BVPs are proved by using of the potential method (boundary integral equations method) and the theory of singular integral equations. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
External boundary value problems in the quasi static theory of triple porosity thermoelasticity
Authors: Svanadze Merab 
Published: March 2018

AbstractIn this paper the quasi static linear theory of thermoelasticity for materials with triple porosity is considered. 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. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical solution of plane constrained shear problem for single crystals within continuum dislocation theory
Authors: Tran Tuan Minh , Baitsch Matthias , Le Khanh Chau 
Published: March 2018

AbstractWithin the recently proposed Continuum Dislocation Theory (CDT), numerical solutions of simple shear test for single crystals strip using finite elements are performed. Under the assumption of plane constrained deformation of crystal having only one active slip system, the plastic slip, the dislocation density as well as the stress‐strain curve are computed. The results of numerical simulations are compared with those obtained from analytical solutions which show good agreement. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite element implementation and simulation of the functional fatigue in shape memory alloys
Authors: Waimann Johanna , Junker Philipp , Hackl Klaus 
Published: March 2018

AbstractDue to the effects of pseudoelasticity and pseudoplasticity, shape memory alloys (SMAs) are very promising materials for the industrial usage. However, applications of SMA are still challenging due to the functional degradation during cyclic loading. The related effect of functional fatigue which occurs during pseudoelastic loading is modeled by subdividing the diffusionless solid/solid phase transformation into a reversible and an irreversible process which is an experimentally motivated ansatz for the complex material behavior, see e.g. [1]. Thus, we take into account a reversible and an irreversible volume fraction for the austenitic and several martensitic phases. To consider the material's polycrystalline structure and hence, differently oriented grains, we use an orientation distribution function which depends on three Euler angles and affects a high numerical efficiency as presented in [2]. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ideas regarding a physically motivated selection of snapshots for POD calculations – a potential application to z‐pin pullout?
Authors: Weber Wolfgang E. , Fangye Yannick F. , Zastrau Bernd W. , Balzani Daniel 
Published: March 2018

AbstractIn order to keep the computational effort manageable, which arises from the modeling of micro‐heterogeneous materials, methods of model reduction are more and more used in computational mechanics. In this contribution, the proper orthogonal decomposition is analyzed. Applying this method to the pullout of metallic fibers, conclusions are drawn which relate the proper orthogonal modes to the mode shapes related to this physical phenomenon. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational generation of statistical volume elements of biphasic asphalt concrete and its material behavior
Authors: Wingender Dennis , Schüler Thorsten , Jänicke Ralf 
Published: March 2018

AbstractAsphalt concrete is a complex mixture appearing as a biphasic material containing mineral aggregates and bitumen and as a triphasic material containing voids in addition [1]. Because of that, the overall material behavior of the asphalt concrete cannot be obtained easily from the known material data of its components and therefore, we apply computational homogenization based on statistical volume elements (SVEs). These SVEs are assumed to be statistically representative to obtain the material properties by finite element simulations and homogenization. We generate these microstructures computationally based on data from XRCT scans. The artificial microstructures show reduced geometrical complexity and therefore, reduced numerical costs compared to direct numerical simulations based on XRCT data. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermomechanics of strain‐induced crystallization in natural rubber under cyclic loading
Authors: Zybell Lutz , Domurath Jan , Schneider Konrad 
Published: March 2018

AbstractStrain‐induced crystallization in natural rubber has been widely investigated in the last decades by scattering techniques. Due to dissipative processes and structural changes in the material, deformation processes are accompanied with a significant amount of heat production/consumption. Time‐resolved wide‐angle X‐ray diffraction (WAXD) was used to characterize the structural changes in natural rubber and the local degree of crystallinity during mechanical deformation. By the simultaneous use of an infrared camera, the scattering results could be combined with changes in the temperature of the specimen due to dissipation and crystallization resp. melting of the crystallites. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the numerical modelling of initiation of sediment transport using Smoothed Particle Hydrodynamics
Authors: Falkner Nadine , Steeb Holger 
Published: March 2018

AbstractMobilization of solid particles at the interface between a porous and a free flow domain is a relevant subject in many fields of mechanical, civil and environmental engineering. One example is the initiation of sediment transport as it appears in river beds. To approximate this initiation state, various theoretical models exist. Common approaches use two‐domain formulations as in [1] or one‐domain formulations as in [6]. The named approaches were compared with Direct Numerical Simulations (DNS) using Smoothed Particle Hydrodynamics (SPH) in [3]. The results of these simulations showed that the theoretical models often underestimate the occurring velocities at the interface and therefore critical velocities to initialize the motion of single grains can be lower than predicted by theoretical approaches. In our numerical simulations, we study creeping flow in a free flow domain coupled to flow in a porous media applying various porous structures. To investigate velocities and shear stresses at the interface more intensively we then compare our numerical results to data from experiments that were performed on equivalent microstructures. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A thermomechanical analysis of interfaces between the mating parts in ultrasonic wire bonding
Authors: Mostafavi Shimaalsadat , Heider Yousef , Markert Bernd 
Published: March 2018

AbstractUltrasonic welding (USW) is an alternative solution for the bonding process especially in automotive industry. Ultrasonic welding of metals is a joining technique as a combination of applying pressure and frictional vibrations within the range of ultrasonic frequencies. In automotive industry, ultrasonic welding is often used for wired connections. As an alternative for crimping technology of multi‐strand aluminum cables in wire bonding, ultrasonic welding is used. This work presents a thermomechanical analysis of the interface between two mating parts in USW. For this reason, the temperature distribution at bonding locations inside a wire bundle due to frictional vibrations and pressure is investigated using the finite element method (FEM). The obvious difference in microsections from different welding samples, which originates from different local temperature rises, was the motivation for this study to further investigate the thermomechanical aspects of the USW by use of finite element simulations. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Untersuchung von Abstiegsanlagen von Horizontalrechen mit Hilfe von Flachwassergleichungen
Authors: Ostermann Lars , Seidel Christian 
Published: March 2018

AbstractDas Erreichen einer guten ökologischen Durchgängigkeit besitzt in der Wasserkraft eine immer größer werdende Priorität. Wurde zunächst die ökologische Durchgängigkeit im Auf‐ und Abstieg durch die Errichtung von Fischwanderhilfen an den Wasserkraftanlagen maßgeblich verbessert, wird nun in der Wasserkraft eine weitere Optimierung des Abstiegs angestrebt. Hierzu werden den mit der Kraftwerksströmung folgenden Wasserlebewesen, die vor dem Schutzrechen der Wasserkraftanlage stehen, zusätzliche Abstiegsmöglichkeiten geschaffen, um in das Unterwasser zu gelangen. Die Entwicklung besonders geeigneter Abstiegsanlagen, die sowohl eine optimale Kraftwerksanströmung, eine gute Leitströmung in die Abstiegsanlage als auch eine optimale Anströmung der Rechenanlage ermöglichen, stellt dabei eine besondere Herausforderung dar. Die hierbei zu lösende Optimierungsaufgabe wird im Rahmen der Entwicklung einer Forschungswasserkraftanlage für ein Hochleistungswasserr mit Hilfe von flachwassergleichungsbasierten Verfahren durchgeführt und nachfolgend vorgestellt. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)