bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interpretation of parameters in phase field models for fracture
Authors: Kuhn Charlotte , Müller Ralf 
Published: December 2012

AbstractPhase field fracture models typically feature a length parameter, which controls the width of the diffuse transition zone between broken and undamaged material. In the limit case of a vanishing length parameter, these models converge to a sharp crack formulation. From this point of view, the length scale parameter is a purely auxiliary numerical quantity. However, the study of the stability of homogeneous solutions in a one dimensional setting permits a different interpretation. Since the length parameter is directly related to the critical stress at which the homogeneous solution becomes unstable and crack nucleation occurs, it can be related to the strength of the material. In this regard, the length parameter itself may be seen as a material parameter. These analytical findings are approved by finite element simulations. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanical properties of hybrid composites made of a steel plate and a laminate connected by means of barbed studs
Authors: Zolkiewski Slawomir 
Published: December 2012

AbstractIn this paper the research results of hybrid composite materials made of a steel plate and laminates are presented. The tested composites were made of a metal sheet plate and a laminate plate connected by means of barbed studs. The laminates were made of three different types of fabrics with: fibreglass, carbon fibres and aramid fibres. As a warp, epoxide resin and polyester resin were used. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Boundary Integral Equations in the Frequency Domain for Interface Cracks under Impact Loading
Authors: Menshykov Oleksandr , Menshykova Marina 
Published: December 2012

AbstractIn the study interface cracks between two dissimilar homogeneous isotropic half‐spaces undergoing impact loading are considered. The problem is solved using the boundary integral equations in the frequency domain. The distributions of the displacements and tractions at the bonding interface and surfaces of the cracks are obtained and analyzed. The stress intensity factors (opening and shear modes) are computed for different load conditions and various properties of the bimaterial. The results are compared with the ones obtained in the time domain. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asymptotic formulae for the flexibility of an infinite row of pin‐loaded holes
Authors: Kratochvil Jan , Becker Wilfried 
Published: December 2012

AbstractThe problem of the flexibility of an infinite row of pin‐loaded holes in an elastic plane or half‐plane is considered within the framework of the complex potential method [1] and the theory of compound asymptotic expansions [2]. The holes are loaded by a given distribution of normal stresses with a resultant equal to the overall transmitted force. First, the relative radius of the holes is introduced as a small parameter. Then, an asymptotic expansion of the complex potentials in terms of this small parameter is constructed. This expansion is uniformly valid in the whole domain, i.e. in the vicinity of the holes as well as in the far‐field. Finally, the flexibility of the row of pin‐loaded holes is evaluated using this solution. In this manner, closed‐form analytical approximations of the flexibility of an infinite row of pin‐loaded holes in a full plane and a half‐plane are obtained. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of domain decomposition methods to isogeometric analysis
Authors: Hesch Christian , Betsch Peter 
Published: December 2012

AbstractDuring the past decade various new spatial discretization techniques have been developed. In particular, the usage of NURBS based shape functions, well known to the CAD community, has been adapted to finite element technology. In the present work we use the mortar finite element method for the coupling of nonconforming discretized sub‐domains in the framework of nonlinear elasticity. We show that the method can be applied to isogeometric analysis with little effort, once the framework of NURBS based shape functions has been implemented. Furthermore, a specific coordinate augmentation technique allows the design of an energy‐momentum scheme for the constrained mechanical system under consideration. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Incompatible Modes for Volumetric Shell Elements in Explicit Time Integration
Authors: Mattern Steffen , Schmied Christoph , Schweizerhof Karl 
Published: December 2012

AbstractExplicit time integration is characterized by small time steps and efficient global operations, leading to a domination of element processing regarding CPU‐time, in particular, as diagonal mass matrices are used. The Enhanced Assumed Strain (EAS) approach requires local operations in order to condense‐out additional degrees of freedom. The method of Incompatible Modes (IM) is presented as an alternative, where incompatible degrees of freedom are included in the global equations, which leads to efficient element formulations. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bayesian inference of linear time‐varying systems based on Hilbert‐Huang transform
Authors: Hu Han , Proppe Carsten 
Published: December 2012

AbstractThis paper proposes an identification method for general linear time‐varying (LTV) MDOF systems (including chainlike and non‐chainlike systems) based on the Hilbert‐Huang Transform (HHT). First, by using Bayesian Inference and a Transitional Markov Chain Monte Carlo (TMCMC) algorithm [1], initial knowledge about the system responses and the white noise in system responses is updated based on measured system responses, which yields the posterior distributions of the noise parameters. Second, each sample system responses are obtained from the posterior distribution and are processed by HHT in order to obtain intrinsic mode functions (IMFs) and the residue as well as the corresponding analytical IMFs and the analytical residue for system responses of each DOF. Finally, the above analytical signals for each DOF are summed respectively to form new analytical responses for each set of sample system responses, which are then used in the identification equations [2] to identify the distributions of system parameters. The proposed method is applied to chainlike and non‐chainlike LTV systems with three types of stiffness variations: smooth, abrupt and periodical variations. The effectiveness and accuracy of the proposed method on 1DOF and 2DOF systems is discussed in numerical simulations. System responses are perturbed by white noise, and the identified results demonstrate the robustness of the method. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energy‐consistent time‐integration for a dynamic finite deformation thermoviscoelastic continuum
Authors: Krüger Melanie , Groß Michael , Betsch Peter 
Published: December 2012

AbstractThe main goal of the present work is to develop a structure‐preserving time integrator, which is based on the works of Öttinger [2] (GENERIC formalism) and Romero [4] (Thermodynamically consistent (TC) algorithm). This intergator is called the enhanced TC algorithm for thermoviscoelastic continuums. The underlying structure is then called enhanced GENERIC, analogously to the earlier puplished thermoviscoelastic double pendulum of Krüger et al. [1]. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature and displacement fields in brake and clutch systems with thermoelastic instabilities
Authors: Graf Matthias , Ostermeyer Georg‐Peter 
Published: December 2012

AbstractIn brake and clutch systems kinetic energy is converted into thermal energy. Experiments show that the corresponding temperature field can develop unstable periodic structures. The temperature field couples to the displacement field by thermal expansion. Local pressure maxima in the frictional plane and the corresponding maxima in heat generated cause thermoelastic instabilities (TEI). A model describing both effects covers layers of thermoelastic materials for all necessary mechanical components of the system. The set of field equations of each layer can analytically be solved by separation of constants. These solutions must fulfill the boundary conditions e.g. in the sliding plane. A stability discussion yields whether TEI appear or not. As a study a brake system is analyzed comprising two pads pressed against a rotating disk with cooling channels inside. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Geometrically exact solution of a buckling column with asymmetric boundary conditions
Authors: Prechtl Gerhard , Schagerl Martin , Schröder Kai‐Uwe 
Published: December 2012

AbstractFor the symmetrically supported Euler buckling column with both ends hinged the classical stability theory yields simple trigonometric functions as buckling modes, i.e. w(x) = A sin αx. The eigenvalues α are just multiples of π. In comparison, the analysis of the asymmetrically supported Euler buckling column with one end clamped and the other end hinged is more complicated: The buckling modes are a combination of trigonometric functions in form of w(x) = A (sin αx − αx cos (αL)). The eigenvalues follow from a transcendental equation.Applying a geometrically exact theory to the aforementioned Euler buckling problems, a similar relation in the complexity of the analyses will naturally arise. Using, e.g., the elastica model the buckling behavior of the symmetrically supported column is represented by elliptic integrals. However, the determination of the buckling behavior of the asymmetrically supported column turns out to be much more complex and elaborate. This article presents a direct comparison of the symmetrically and asymmetrically supported buckling columns regarding their analyses by means of classical stability theory and by the geometrically exact theory of the elastica. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micro‐mechanical analysis of creep behavior in a multipass weld
Authors: Lvov Ivan 
Published: December 2012

AbstractA method of evaluating creep response of the multipass weld based on the micro‐macro mechanics approach is introduced. Multipass weld microstructure that consists from columnar, coarse and fine grained zones is considered. Materials of these constituents assumed to be isotropic. Weld metal properties of inelastic behavior have general type of symmetry and are described by the anisotropic creep constitutive model.To model the microstructure of the multipass weld metal the representative volume element (RVE) is created for CAE Abaqus. Material properties of weld metal grain type zones are taken from the experiments. Numerical tests on uniform loading of the RVE are performed. Creep material properties for equivalent weld material are found for welds with different number of passes. The symmetry type of the creep material properties of multi‐pass weld are evaluated for the equivalent weld material. As an example of macro model analysis of the welding, the creep calculation of the cylindrical shell with the welding under the uniform inner pressure is performed. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Plastic deformation of rough surfaces
Authors: Willner Kai , Hauer Franz 
Published: December 2012

AbstractFriction forces are only transferred within the the real area of contact Areal, which is usually smaller than the apparent area of contact Ao. The maximum friction stress τfric is therefore determined by the shear limit τmax in the area of real contact and the fraction of the real area of contact (τfric = τmax (Areal/Ao)). For rough surfaces the size of Areal is governed o by the plastic deformation of the surface roughness. We present a fully elasto‐plastic halfspace contact formulation based on the work of Jacq et al. [1]. Linear elastic‐plastic material behavior is modeled based on v. Mises plasticity with isotropic hardening. The algorithm gives the residual stress as well as the full plastic deformation field due to a frictionless normal contact. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical modelling of layered composite struts
Authors: Völlmecke Christina , Müller Wolfgang H. 
Published: December 2012

AbstractA numerical approach simulating the effects of interlaminar defects on the buckling stability of layered composite struts is presented. The formulation is based on the weak form of the balance of linear momentum whilst large strains are considered. First results are presented whilst comparisons are drawn to analytically derived results. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Methodology of ROMing applying POD of BWR Fuel Assemblies applied to Introductory Examples
Authors: Prill Dennis P. , Stokmaier Markus , Class Andreas G. 
Published: December 2012

AbstractFor high‐power low‐flow operating conditions associated with unfavorable power distribution Boiling Water Reactor (BWR) operation requires maintaining a certain distance to the stability limit given. The stability boundary with respect to small perturbations is given by analytical methods. Supplementary evaluation of non‐linear states require time‐consuming numerical integration or experimental data and strongly depend on the considered transient. Developing a self‐contained methodology for investigating the full non‐linear BWR system parameter space at low computational cost supplements established methods. The methodology of Reduced Order Modeling based on Proper Orthogonal Decomposition (ROM‐POD) is tested for this purpose and validation in terms of the Korteweg de‐Vries (KdV) equation. A transient analysis of simplified reactor physics [1] yields a low‐rank ROM and is depending on the chosen transients but not on the details. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of a stochastic friction coefficient depending on a randomly rough surface
Authors: Gaus Nicole , Proppe Carsten , Hetzler Hartmut 
Published: December 2012

AbstractThe goal of this contribution is to calculate the the friction coefficient for a scanned surface of a worn brake pad. The data shows that the asperities can be approximated by paraboloids which allows to calculate the contact force and area with the Hertz contact model if the deformation is elastic. The friction force is calculated with the Bowden‐Tabor approach which suggests that the friction force is the force to shear apart contacting asperities. This is considered to be the dominant friction cause in dry contact. To generate many surfaces with similar peak statistics the spectral decomposition is used. The friction coefficient and it's stochastic properties is calculated for these surfaces. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Zur Interaktion von Sägedraht und Ingot
Authors: Lorenz Michael , Ams Alfons 
Published: December 2012

AbstractEs wird ein mechanisches Modell zur Beschreibung des bewegten Sägedrahtes unter Einwirkung des Siliziumblocks (Ingot) vorgestellt. Mit dem Prinzip von HAMILTON wird, unter der Voraussetzung nichtlinearer Verformungskinematik sowie unter Berücksichtigung der Dehn‐ und Biegesteifigkeit des Drahtes, das Variationsproblem und die Bewegungsgleichungen hergeleitet. Die Wirkung des Ingot auf den bewegten Draht wird als Folgelast modelliert. Ausgehend vom Variationsproblem wird mit einem gemischten RITZ‐Ansatz die stationäre Lage des Drahtes für verschiedene Einflussparameter berechnet und Stabilitätsuntersuchungen durchgeführt. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling of human motion in interaction with sports surface – Energetic Aspects vs. Risk of Injury
Authors: Bellanger Claudia , Hetzler Hartmut , Seemann Wolfgang 
Published: December 2012

AbstractThe aim in high‐performance sports activities is reaching the optimum between high efficiency and low risk of injuries during workout. This paper wants to investigate several types of human motion in interaction with a compliant ground. The influence of the surface parameters on the human metabolic cost consumption and the reaction force is analysed. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An Experimental Method for the Phase Controlled Frequency Response Measurement of Nonlinear Vibration Systems
Authors: Mojrzisch Sebastian , Wallaschek Jörg , Bremer Jan 
Published: December 2012

AbstractExperimental determination of frequency response function of nonlinear systems is difficult when there exists more than one solution branch. Depending on the system at hand, various types of jump phenomena can be observed and in the example of the well‐known Duffing‐oscillator, it is not possible to experimentally determine the unstable solution branch if the system is excited by a harmonic force. In the present paper we investigate the Duffing‐oscillator and present a method, which allows to reformulate the equation of motion of the system with force‐excitation in the form of an equivalent self‐excited system. Considering the phase between force and response as the input variable, it is possible to evaluate the frequency of the systems vibration for any given phase shift. In the same way the corresponding response amplitude is determined. An experimental set‐up is presented, which is used to validate the performance of the method. Measurements of the backbone curve are performed and discussed on the background of theoretical predictions. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Degenerate cases of stability loss of an elastic fluid‐conveying tube
Authors: Jurisits Richard , Steindl Alois 
Published: December 2012

AbstractThe two‐dimensional non‐linear dynamics of a liquid‐filled tube is considered. The tube is clamped at the upper end, a point mass is fixed to its free lower end and laterally it is supported by two springs. The uniform flow velocity of the fluid, the end mass, the spring constant and the vertical position of the springs are considered as the distinguished parameters of the problem. A linear stability analysis shows that the (degenerate) case of a Takens‐Bogdanov‐Hopf bifurcation exists, which is associated with a high frequency flutter movement superimposed on a low frequency flutter around a statically buckled state of the tube. We account for this degenerate case by indicating the parameter regime necessary for its occurence and and give the bifurcation diagram for the trivial equilibrium position of the tube. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermodynamically and variationally consistent modeling of distortional hardening: application to magnesium
Authors: Shi Baodong , Mosler Jörn 
Published: December 2012

AbstractTo capture the complex elastoplastic response of many materials, classical isotropic and kinematic hardening alone are often not sufficient. Typical phenomena which cannot be predicted by the aforementioned hardening models include, among others, cross hardening or more generally, the distortion of the yield function. However, such phenomena do play an important role in several applications in particular, for non‐radial loading paths. Thus, they usually cannot be ignored. In the present contribution, a novel macroscopic model capturing all such effects is proposed. In contrast to most of the existing models in the literature, it is strictly derived from thermodynamical arguments. Furthermore, it is the first macroscopic model including distortional hardening which is also variationally consistent. More explicitly, all state variables follow naturally from energy minimization within advocated framework. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prediction of microstructure in a Cosserat continuum using relaxed energies
Authors: Khan Muhammad Sabeel , Hackl Klaus 
Published: December 2012

AbstractWe develop a nonlinear incompressible multiphase material model in a Cosserat continuum with microstructure. The free energy of the material is enriched with an interaction potential taking into account the intergranular kinematics at the continuum scale. As a result the total energy becomes non‐convex, thus giving rise to the development of microstructural phases. To guarantee the existence of minimizers an exact quasi‐convex envelope of the corresponding energy functional is derived. As a result a three phase material energy appears, among them two of the phases are with microstructure in the translational motion (displacment field) and micromotion (microrotation field), whereas the third phase is without internal structure. The corresponding relaxed energy is then used for finding the minimizers of the two field minimization problem corresponding to a Cosserat continuum. Results from a numerical example predicting the development of microstructure in the material are presented. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
About the Microstructural Effects of Polycrystalline Materials and their Macroscopic Representation at Finite Deformation
Authors: Lehmann Eva , Loehnert Stefan , Wriggers Peter 
Published: December 2012

AbstractIn the sheet bulk metal forming field, the strict geometrical requirements of the workpieces result in a need of a precise prediction of the material behaviour. The simulation of such forming processes requires a valid material model, performing well for a huge variety of different geometrical characteristics and finite deformation.Because of the crystalline nature of metals, anisotropies have to be taken into account. Macroscopically observable plastic deformation is traced back to dislocations within considered slip systems in the crystals causing plastic anisotropy on the microscopic and the macroscopic level. A finite crystal plasticity model is used to model polycrystalline materials in representative volume elements (RVEs) of the microstructure. A multiplicative decomposition of the deformation gradient into elastic and plastic parts is performed, as well as a volumetric‐deviatoric split of the elastic contribution. In order to circumvent singularities stemming from the linear dependency of the slip system vectors, a viscoplastic power‐law is introduced providing the evolution of the plastic slips and slip resistances. The model is validated with experimental microstructural data under deformation. The validation on the macroscopic scale is performed through the reproduction of the experimentally calculated initial yield surface. Additionally, homogenised stress‐strain curves from the microstructure build the outcome for a suitable effective material model. Through optimisation techniques, effective material parameters can be determined and compared to results from real forming processes. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of an anisotropic growth formulation to computational structural design
Authors: Waffenschmidt Tobias , Menzel Andreas 
Published: December 2012

AbstractCommon structural optimisation problems consist of problem‐specific objective functions which have to be minimised mathematically with respect to design and state variables taking into account particular constraints. In contrast to this, we adopt a conceptually different approach for the design of a structure which is not based on a topology‐optimisation technique. Instead, we apply a one‐dimensional energy‐driven constitutive evolution equation for the referential density–originally proposed for the simulation of remodelling effects in bones–and embed this into the micro‐sphere‐concept to end up with a three‐dimensional anisotropic growth formulation. The objective of this contribution is to investigate this approach with emphasis on its application to structural design problems by means of two three‐dimensional benchmark‐type boundary value problems. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)