bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computation of Creep in an Axially Moving Beam
Authors: Simon Gottfried , Holl Helmut J. 
Published: December 2011

AbstractTwo mechanical models for an axially moving beam supported by discrete elastic springs are derived, analysed and compared. It is considered that the beam has a constant thickness, a predefined temperature distribution and a given transversal load. The first beam model applies global Ritz approximations for the spans with springs. Gauss integration points are used in longitudinal and transverse direction. The second beam model uses a conventional FE description. The thermal and pressure loads cause stresses, which lead to strain rates due to creep of the material so that a time dependent deformation between the elastic supports results. Here the axial motion is considered to be so slow so that inertia effects can be neglected. The axial transport of the inelastic creep‐strains has been considered in the computation. The temperature field is constant and fixed in space. The deflection of the axially moving beam model is computed considering a variable number of spans separated by elastic springs. The computed results of the two mechanical models are compared for a beam with two spans. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Combined asymptotic and direct approach to the nonlinear plane problem of dynamics of a thin curved strip
Authors: Vetyukov Yury 
Published: December 2011

AbstractOn the example problem of large elastic oscillations of a thin curved strip we present a combined modeling approach: the non‐reduced continuous problem splits asymptotically into a system of linear equations of the rod model and a problem over the thickness; direct approach to a material line provides nonlinear equations; after the numerical solution of the reduced problem we restore the distributions of stresses, strains and displacements over the thickness. Convergence to the solution for the non‐reduced continuum as the thickness tends to zero justifies the analytical conclusion that the curvature and variation of the material properties over the thickness do not require special treatment for classical Kirchhoff's rods. Further terms of the asymptotic expansion lead to a model with shear and extension, in which curvature appears in a non‐trivial way.The results of the study are illustrated by a numerical example and provide better understanding of the relation between the solutions of the original and dimensionally reduced problems for spatial rods and shells. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Seismic collapse capacity spectra for simple structures vulnerable to dynamic instabilities
Authors: Adam Christoph , Jäger Clemens 
Published: December 2011

AbstractIn this study collapse capacity spectra based on various definitions of the seismic intensity are set in contrast and evaluated. The presented collapse capacities for highly inelastic non‐deteriorating single‐degree‐of‐freedom (SDOF) systems, which are vulnerable to the destabilizing effect of gravity loads, are derived for a near‐fault set of ground motions with distinct pulse characteristics. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Instability maps of a system of Mathieu‐Equations using different perturbation methods
Authors: Hubinger Stefan , Gattringer Hubert , Bremer Hartmut , Mayrhofer Karl 
Published: December 2011

AbstractIt is well known, that the Mathieu‐equation possesses several instability regions. Dealing with systems of Mathieu‐ equations results in an increase of the number and size of the instability regions. The so called combination frequencies, an addition of the natural frequencies of the time invariant system, appear. Applying the Floquet theory and numerical integration yields a grid of stable and unstable areas. Even if this procedure delivers good results it is not suitable for a fast calculation, because it is very CPU‐ time consuming. Therefore several Perturbation methods are compared in this paper. The first one is the Lindstedt‐ Poincaré method, delivering some of the instability areas. The second one is the Multiple‐ Scales‐ method used with an approximation up to second order. Assuming the periodicity of the equations solution, with parameters on the boundary curve, facilitates the mathematical description of the borderline. An example is carried out; the analytical stability boundaries are validated by the Floquet theory. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study on dimension reduction methods for a fluid conveying tube
Authors: Steindl Alois 
Published: December 2011

AbstractThe Application of Dimension Reduction by Approximate Inertial Manifolds to the dynamics of a fluid conveying tube doesn't perform as expected due to the presence of viscous damping terms, which lead to a cluster point of stable eigenvalues. We investigate methods to circumvent the problems introduced by this cluster point: For the spectral decomposition part of the invariant subspaces are computed using the Schur factorisation. Also a different choice of basis functions for the dominating modes avoids the difficulties. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the influence of design parameters and nonlinearities in vehicle suspensions on road deformation
Authors: Vogt Heike , Hetzler Hartmut , Seemann Wolfgang 
Published: December 2011

AbstractAmong others, two main objectives of modern vehicle design are road friendliness and ride comfort. Both aspects are strongly related since the dynamical tire forces depend on the vertical acceleration of the vehicle. In order to investigate the influence of design and operation parameters, different car models are considered which move with constant velocity on a rippled road. First, a linear half car model is examined and the influence of different design parameters is discussed. Second, nonlinear suspensions with Coulomb friction due to sealings as well as with bilinear shock absorbers are taken into account. The vertical dynamics of the vehicle model and the dynamic tire forces between vehicle and road are calculated using analytical methods. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An extended tube model for thermo‐viscoelasticity of rubberlike materials: Parameter identification and examples
Authors: Behnke Ronny , Dal Hüsnü , Kaliske Michael 
Published: December 2011

AbstractThe extended tube‐model was presented by KALISKE & HEINRICH (RCT 72, 602‐632) in 1999 as a novel approach for isothermal hyperelasticity of rubberlike materials. This contribution is dedicated to its further development to finite non‐linear thermo‐viscoelasticity. A non‐linear evolution law and a thermo‐mechanical coupled free energy formulation are the kernel of the phenomenological approach where the elastic material response is inspired by statistical‐mechanical theory. The representation of viscoelasticity is based on a multiplicative decomposition of the deformation gradient. The Helmholtz free energy of the material is formulated in terms of isothermal free energy functions multiplicatively coupled with non‐linear temperature evolution functions. The non‐linear evolution law for the viscous material branch is solved by applying a predictor‐corrector algorithm with an exponential mapping scheme. In today's literature, several sophisticated thermo‐mechanical material models are available. However, they are built upon a considerable number of material parameters governing the mechanical and thermal material response which need to be identified for practical application. Therefore, particular emphasis is given to an appropriate parameter identification technique for the thermal field. For the latter, a uniaxial extension test is carried out where the recorded data of the temperature field of the rubber specimen under cyclic loading is used for parameter identification. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Collapse criteria of foam cells under various loading
Authors: Evdokymov Nikolai , Altenbach Holm , Eremeyev Victor A. 
Published: December 2011

AbstractRecently porous materials are widely used in civil and mechanical engineering. In particular, such porous materials as metal and polymer foams have applications in lightweight structures. From mechanics point of view foams can demonstrate unusual behavior such as strain localization related to foam cells buckling under certain loads.The aim of this work is the elaboration of the model of foam material taking into account the cell collapse. We consider the cell collapse initiation during the elastic instability and its further evolution under loading. The geometrical structure of foam is generated with the use of the Voronoi algorithm. Based on stochastic distributions of cells we create various geometrical models of foams. The influence of the cell volume, wall thicknesses and material properties of the foam material on critical loads is obtained. The calculations are performed with the use of Abaqus CAD/CAE system. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparison between inverse form finding and shape optimization methods for anisotropic hyperelasticity in logarithmic strain space
Authors: Germain Sandrine , Steinmann Paul 
Published: December 2011

AbstractIn this paper an inverse mechanical formulation and a Limited‐Broyden‐Flechter‐Goldfarb‐Shanno method for shape optimization are compared. Both methods deal with the determination of the undeformed shape of an hyperelastic part knowing its deformed configuration and the applied loads. We consider anisotropic hyperelastic materials that are formulated in the logarithmic strain space. Beside the theoretical aspects, we present a numerical example. We established that no difference could be found between the node coordinates on the undeformed sheets computed with both methods. However the convergence to the solution is faster for the inverse mechanical formulation compared to the L‐BFGS algorithm. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Model for the Texture Evolution in Polycrystalline Materials
Authors: Heinz Sebastian 
Published: December 2011

AbstractWe study a polycrystalline material that undergoes a rigid‐plastic rate‐independent evolution. Of our particular interest is the creation of texture and the resulting qualitative change in the macroscopic material response: from isotropic to anisotropic. Texture is represented by a crystal orientation distribution function, which associates every spatial point with a probability measure on the set of rotations. We discuss an energetic formulation for the texture evolution in the context of generalized standard materials. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of coupled deformation‐induced twinning and dislocation slip using incremental energy minimization
Authors: Homayonifar Malek , Mosler Jörn 
Published: December 2011

AbstractThe complex interplay between dislocations and deformation‐induced twinning leads to a relatively poor formability of magnesium at room temperature. For understanding the complicated behavior of this metal, a novel model is presented. It is based on a variational principle. Within this principle based on energy minimization, dislocation slip is modeled by crystal plasticity theory, while the phase decomposition associated with twinning is considered by sequential laminates. The proposed model captures the transformation of the crystal lattice due to twinning in a continuous fashion by simultaneously taking dislocation slip within both, possibly co‐existent, phases into account. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of pseudo‐plasticity in shape‐memory‐alloys
Authors: Junker Philipp , Hackl Klaus 
Published: December 2011

AbstractThe name shape memory originates from the material's capability to recover its original shape after an apparent plastic deformation. The secret of this property lies in the specific microstructure. During mechanical loading, alloys of this particular kind change their crystallographic structure from randomly orientated martensite to ordered martensite. With austenite as high‐temperature inter‐state induced by heat supply, a recovery from the ordered to the unordered martensite is possible. This is accompanied by a macroscopic "healing" process.We apply our material model for shape‐memory alloys to this special property and present numerical results. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
From atomistics to the continuum: a mesh‐free quasicontinuum formulation based on local max‐ent approximation schemes
Authors: Kochmann Dennis M. , Amelang Jeffrey S. , Español Malena I. , Ortiz Michael 
Published: December 2011

AbstractA novel quasicontinuum formulation based on mesh‐free local maximum‐entropy approximation schemes is presented, whose accuracy (compared to full atomistic simulations) is tunable and, in particular, can be designed superior to conventional affine approximation schemes. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of a Viscoelastic Model to simulate the Interface of a Metal/Fibre‐Reinforced Polymer Joint
Authors: Konchakova Natalia , Mueller Ralf , Barth Franz‐Josef 
Published: December 2011

AbstractA viscoelastic model with the Lemaitre‐type damage is applied to simulate an interfacial adhesive zone in light weight engineering structures, like aluminum/fiber‐reinforced polymer specimens. The evolution of irreversible deformation and damage progression are investigated. The joint of aluminium alloy 5754 (AA5754) and carbon fibre reinforced thermoplastic composite CF‐PA66 is manufactured by means of an epoxy (1K) adhesive. The adhesive zone is considered as an interface material. The aim of the research is to study the influence of the interface geometry on the mechanical characteristics of the structure. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A material model of nonlinear fractional viscoelasticity
Authors: Müller Sebastian , Kästner Markus , Brummund Jörg , Ulbricht Volker 
Published: December 2011

AbstractMultiscale methods are frequently used in the design process of textile reinforced composites. In addition to the models for the local material structure it is necessary to formulate appropriate material models for the constituents. While experiments have shown that the reinforcing fibers can be assumed as linear elastic, the material behavior of the polymer matrix shows certain nonlinearities.These effects are mainly due to strain rate dependent material behavior. Fractional order models have been found to be appropriate to model this behavior. Based on experimental observations of Polypropylene a one‐dimensional nonlinear fractional viscoelastic material model has been formulated. Its parameters can be determined from uniaxial, monotonic tensile tests at different strain rates, relaxation experiments and deformation controlled processes with intermediate holding times at different load levels. The presence of a process dependent function for the viscosity leads to constitutive equations which form nonlinear fractional differential equations. Since no analytical solution can be derived for these equations, a numerical handling has been developed. After all, the stress‐strain curves obtained from a numerical analysis are compared to experimental results. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of nanoindentation experiments by means of atomic force microscopy
Authors: H. Müller Wolfgang , Worrack Holger , Zapara Maksim 
Published: December 2011

AbstractNanoindentation is quite a common method for local material characterization. Values for hardness and Young's modulus can be determined directly from the recorded data. Essential for the correct determination of the material parameters is the precise measurement of the actual indentation depth of the indenter. The indenter measures the current depth by means of a Wheatstone bridge which correlates the indentation depth to a change in voltage. A possible tool for the verification of the recorded indentation depths is Atomic Force Microscopy (AFM). AFM is able to scan an area of indents for almost any surface. The deflection of the tip is measured by a laser spot reflected from the surface of the cantilever. The difference in height between the surface and the indent can directly be read off from the plotted image. However, using an AFM only allows us to measure the depth of the permanent indentation depth after unloading the indenter. Nevertheless, correlation between the remaining indentation depths measured by the explained methods allows for a first assessment of the correctness of the online recorded depth‐data by the nanoindenter. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermo‐mechanical description of material diffusion during an ultrasonic wire bonding process
Authors: Müller Wolfgang H. , Sbeiti Mohamad , Schneider‐Ramelow Martin , Geissler Ute 
Published: December 2011

AbstractThe volume diffusion during an ultrasonic wire bonding process leads to a material transport between the wire and the material of the substrate and thus creates an intermetallic phase between them. In order to investigate this process, the thermal and mechanical mechanisms occurring during wire bonding should be studied. For this purpose, finite element simulations based on coupled thermo‐mechanical equations are performed to study the temperature and stress distribution in and around the interface. The final objective of the model is to develop a growth law for the intermetallic phases by considering the mechanical work applied to the wire in addition to the temperature increase at the interface. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimization of elastic material parameters of sheet metal with FEMU and DIC
Authors: Schmaltz Stefan , Willner Kai 
Published: December 2011

AbstractIn this paper a deep‐drawing sheet steel is characterized through tensile tests with samples taken in different angles to the rolling direction. The displacement field is recorded with an optical full‐field measurement system and the deformation field is calculated by Digital Image Correlation (DIC).The orthotropic elastic material parameters are identified through an iterative parameter optimization via Finite Element Model Updating (FEMU). In this procedure the material parameters are modified in every iteration so that the numerically computed deformation field and forces match the measured values as well as possible.Depending on the objective function and the input values used in the optimization routine, global or only local minima exist. To show the convergence of the applied technique, two different optimization algorithms, one gradient‐based and one gradient‐free with different initial starting points were used. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An isoclinic elasto‐plasticity model at finite strains with the notion of plastic spin
Authors: Ulz Manfred H. 
Published: December 2011

AbstractIn forming processes metal sheets undergo large deformations. The crystallographic texture changes and preferred directions in the macroscopic behaviour are introduced as a result. This yields an anisotropic behaviour in plastic deformations and, furthermore, these preferred directions may rotate with evolution of plasticity. A phenomenological model for the description of orthotropic elasto‐plastic solids with the notion of plastic spin is developed. The latter is the spin of the continuum relative to the material substructure. A multiplicative decomposition of the deformation gradient tensor into an elastic and a plastic part serves as the basis for the formulation and computational implementation. The resulting incompatible intermediate manifold is identified in the model as an isoclinic configuration. Moreover, the described rate‐independent constitutive model is capable of modelling isotropic elastic and orthotropic plastic material behaviour. The latter is dominated by pre‐existing preferred orientations in the material and is described by a Hill‐type yield criterion. These orientations are allowed to rotate by introduction of the plastic spin into the model. Finally, numerical simulations demonstrate the performance of the model. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Plastic slip patterning through rate dependent non‐convex gradient‐enhanced plasticity
Authors: Yalçinkaya Tuncay , Brekelmans W. A. M. , Geers M.G.D. 
Published: December 2011

AbstractThe paper presents a non‐convex rate dependent strain gradient plasticity framework for the description of plastic slip patterning in metal crystals. The non‐convexity is treated as an intrinsic property of the free energy of the material. Departing from explicit expressions for the free energy, the non‐convex strain gradient crystal plasticity model is derived in a thermodynamically consistent manner, including the accompanying slip law. For the numerical solution of the problem, the displacement and the plastic slip fields are considered as primary variables. These fields are determined on a global level by solving simultaneously the linear momentum balance and the resulting slip evolution equation. The slip law differs from classical ones in the sense that it naturally includes a contribution from the non‐convex free energy term, which enables patterning of the deformation field. The formulation of the computational framework is partially dual to a Ginzburg Landau type of phase field modeling approach. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FE‐modeling of ideal grain growth based on preprocessed EBSD data
Authors: Gladkov Slawa , Kayser Tobias , Svendsen Bob 
Published: December 2011

AbstractThe purpose of this work is to show the use of experimentally measured micrograph data in the context of ideal grain growth simulation which is modeled with a help of finite element method. In this regard the micrograph data is considered as initial condition for a grain growth simulation. General remarks on preparation (preprocessing) of the micrographs and staggered algorithmic formulation are presented. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carbon dioxide storage in the subsurface: an approach including solid deformations and phase transition.
Authors: Häberle Kai , Ehlers Wolfgang 
Published: December 2011

AbstractCO2 is supposed to be one of the major greenhouse gases. Thus, the idea arose to capture and store CO2 in the subsurface. Besides other geological formations, CO2 can be injected into deep saline aquifers, where its upward migration is blocked by an almost impermeable cap‐rock layer. It is crucial to guarantee the safety of this storage and to eliminate possibilities of leakage. Therefore, deformation processes of the rock matrix and the cap‐rock layer, which might be induced by the high pressure injection of CO2, must be investigated. The deformations may lead, on the one hand, to an increase in porosity and permeability and thereby improve the storage capacity of the reservoir. On the other hand, the increase in stress results in solid deformations of the rock matrix and may cause crack development in the cap‐rock layer. Additionally, phase transition processes between supercritical, liquid and gaseous CO2 have to be taken into account when the pressure or the temperature in the reservoir changes. The phase transition can cause an increase of CO2 volume and, hence, an increase in pressure and stress.A continuum‐mechanical description of multiphasic flow including solid deformations is derived, which is based on the Theory of Porous Media (TPM). An elastic‐plastic material law is applied to account for the behaviour of the solid skeleton. Numerical examples are used to investigate the injection of CO2. Regions with high stresses can be identified and considered for crack initiation. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)