bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of measurement data metrics on the identification of Interval Fields for the representation of spatial variability in finite element models
Authors: Faes Matthias , Cerneels Jasper , Vandepitte Dirk , Moens David
Published: October 2016

Due to the exponential growth in computing power, numerical modelling techniques method have gained an increasing amount of interest for engineering and design applications. Nowadays, the deterministic finite element (FE) method, an efficient tool to accurately solve the Partial Differential Equations (PDE) that govern most real‐world problems, has become an indispensable tool for an engineer in various design stages. A more recent trend herein is to use the ever increasing computing power incorporate uncertainty and variability, which is omnipresent is all real‐live applications, into these FE models. Several advanced techniques for incorporating either variability between nominally identical parts or spatial variability within one part into the FE models, have been introduced in this context. For the representation of spatial variability on the parameters of an FE model in a possibilistic context, the theory of Interval Fields (IF) was proven to show promising results. Following this approach, variability in the input FE model is introduced as the superposition of base vectors, depicting the spatial ‘patterns’, which are scaled by interval factors, which represent the actual variability. Application of this concept, however, requires identification of the governing parameters of these interval fields, i. e. the base vectors and interval scalars. Recent work of the authors therefore was focussed on finding a solution to the inverse problem, where the spatial uncertainty on the output side of the model is known from measurement data, but the spatial variability on the input parameters is unknown. Based on an a priori knowledge on the constituting base vectors of the interval field, the simulated output of the IFFEM computation is compared to measured data, and the input parameters are iteratively adjusted in order to minimize the discrepancy between the variability in simulation and measurement data. This discrepancy is defined based on geometric properties of the convex sets of both measurement and simulation data. However, the robustness of this methodology with respect to the size of the measurement data set that is used for the identification, as yet remains unclear. This paper therefore is focussed on the investigation of this robustness, by performing the identification on different measurement sets, depicting the same variability in the dynamic response of a simple FE model, which contain a decreasing amount of measurement replica. It was found that accurate identification remains feasible, even under a limited amount of measurement replica, which is highly relevant in the context of a non‐probabilistic representation of variability in the FE model parameters. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Development and experimental validation of a patient‐specific lumbar spine FE model to predict the effects of instrumentations
Authors: Beckmann Agnes , Mundt Marion , Herren Christian , Siewe Jan , Kobbe Philipp , Sobottke Rolf , Stoffel Marcus , Markert Bernd
Published: October 2016

A lumbar spine model without instrumentations was created using CT data and validated with experimental results of the same specimen. The specimen was loaded with pure moments in a spine test rig. The material parameters were taken from literature and adapted for better simulation of the experiments. The results show that further calibration of the material parameters and the implementation of additional ligamentous structures are necessary to simulate the spine's motion reliably. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experiments and numerical simulations of new biaxially loaded specimens to characterize the behavior of thin metal sheets
Authors: Gerke Steffen , Schmidt Marco , Brünig Michael
Published: October 2016

The paper deals with the development of new biaxially loaded specimens to study the damage behavior of ductile metals under different loading conditions.

Based on numerical simulations newly designed biaxial specimens are developed and numerically studied while an experimental program has been realized in continuation. The experimental results have been evaluated by digital image correlation (DIC) and compared with the results of finite element simulations. By concideration of different biaxial loading conditions it is possible to cover a wide range of stress triaxialities and Lode parameters in tension, shear and compression domains and consequently the newly proposed specimens facilitate a controlled study of damage and fracture at different stress states. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale damage analyis for steel structures
Authors: Heinrich Sven , Kowalsky Ursula , Dinkler Dieter
Published: October 2016

An approach to model the deterioration of steel structures is presented by transferring the results of a continuum damage mechanics analysis to an extended beam model which can account for the loss of structural integrity.

Damage starts at the microscopic level by the initiation, growth and coalescence of voids with decreasing material resistance followed by the formation of microcracks at the mesoscale. Nevertheless, the material behavior can be sufficiently modelled on a phenomenological basis taking into account viscoplasticity, hardening effects and damage evolution. The associated model parameters are identified with the help of an evolutionary algorithm adapting numerical to experimental results. Using the finite element method a nonlocal formulation of the damage variable is required to obtain mesh‐independent results by structural analysis. The maximum element size is limited by the small magnitude of the internal length. Therefore, numerical analyses of large scale 3D steel structures are computationally expensive.

To reduce the effort a beam element is proposed to account for the plastic hinges and the loss of resistance in the course of damage evolution. The corresponding relationship of bending moment and curvature bases on the continuum damage mechanics model. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental characterization of dynamic properties of honeycomb sandwich joints and plates
Authors: Khosravani Mohammad Reza , Weinberg Kerstin
Published: October 2016

In lots of lightweight applications, constructions are also made by honeycomb sandwiches but little is known about failure and dynamic behavior of sandwich plate connections. In this research, an experimental and simulation study of the mechanical and failure behavior of honeycomb sandwich plates and joints are performed. In detail, series of tensile test have been conducted under quasi static conditions and failure behavior and resistance of the specimens are investigated. The specimens are made by phenolic resin‐impregnated aramid paper as core and two different layers of glass fiber reinforced plastic as face sheets in each side. In addition to the experimental tests, numerical simulation with finite element models are performed in Abaqus. Failure modes are investigated and finally a good agreement between test data and simulation results is achieved. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Poiseuille‐Type Fluid Transport in Poro‐Elastic Solids at Fracture
Authors: Kienle Daniel , Mauthe Steffen , Miehe Christian
Published: October 2016

Hydraulic fracturing has led to controversial public debates about its risks due to environmental issues, such as increased seismic activity or drinking water contamination. The technique is primarily used to gain crude oil or natural gas from unconventional wells. To this end, a high pressurized fracking fluid is injected into a wellbore to fracture deep‐rock formations, leading to growing cracks, a subsequent increase of permeability in these formations and thus to an increased flow of natural gas and crude oil. To weight the risks and the perspectives of hydraulic fracturing a profound understanding of the involved processes is crucial. Numerical simulations are the most cost efficient way for the required studies, but demand a reliable model with a stable implementation.

We propose a canonical minimization principle for the Biot‐type fluid transport in porous media based on only two constitutive functions, that is the free energy function
$\hat{\psi}$,
and a dissipation potential
$\hat{\phi}$,
[1]. This formulation is coupled to a phase‐field approach for fracture which characterizes an intuitive and descriptive regularization of a crack surface that converges for vanishing length‐scale parameter to a sharp crack. The crack phase‐field allows for a distinct incorporation of an extra fluid flow within cracked regimes of the solid [2]. This extra fluid flow is modeled according to Poiseuille law for laminar flow, yielding an implementation via a change of the permeability tensor, i. e., making it a function of the crack opening width, formulated itself in terms of the strain and the gradient of the crack phase field. © 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prediction of fracture in grain boundaries of nano‐coatings using cohesive zone elements
Authors: Rezaei Shahed , Wulfinghoff Stephan , Reese Stefanie
Published: October 2016

A cohesive zone element technique (CZ) is applied to study grain boundary fracture in nano coating layers (see [1]). This goes along with the investigations of the delamination and fracture behavior of the coatings and the substrate interface. The main motivation is to investigate antiadhesive and wear resistant properties of coatings made of ceramics produced by the High Power Pulsed Magnetron Sputtering (HPPMS) technique [2]. Different physical conditions in HPPMS result into different grain morphologies with different mechanical properties. Therefore prediction of fracture and damage in such systems can lead to the optimum choice of process parameters in order to gain the best fracture resistance properties for the coatings. To illustrate the applicability of the model, several simulations with different mechanical and structural properties are performed. The developed CZ element model is capable of modeling the separation, the contact and also the irreversible reloading conditions in different directions [3]. The model is further developed to be applicable for geometrically complex interfaces including different bonding behaviors, with a high robustness. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Assessment of asymmetric crack initiation in open‐hole plates using a coupled stress and energy criterion
Authors: Rosendahl Philipp L. , Weißgraeber Philipp , Stein Nicolas , Becker Wilfried
Published: October 2016

An application of the finite fracture mechanics concept to open‐hole plates subject to combined tensile and bending loading is presented. In finite fracture mechanics, the simultaneous satisfaction of both, a stress and an energy criterion, is enforced as a condition for crack initiation. Efficient modeling and closed‐form expressions for the dependence of the stress and energy quantities on governing structural and material parameters allow for a comprehensive numerical analysis of the onset of asymmetric crack patterns. The obtained failure load predictions are found to agree well with a cohesive zone model and experimental data from literature. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A coupled stress and energy failure model for crack initiation in arbitrarily shaped adhesive lap joints
Authors: Stein Nicolas , Weißgraeber Philipp , Becker Wilfried
Published: October 2016

In this work, crack initiation in adhesive lap joints of arbitrary joint configuration is studied by means of a finite fracture mechanics approach. The analysis is based on a general stress solution for adhesive joints combined with a coupled stress and energy criterion. The instantaneous formation of a crack of finite size is predicted if a stress and energy criterion are satisfied simultaneously. The closed‐form analytical solution of the stress field allows for an efficient evaluation of the crack initiation load and corresponding finite crack length. A comparison to experimental results from literature and to numerical results obtained with a cohesive zone model approach shows a good agreement. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient numerical integration of arbitrarily broken cells using the moment fitting approach
Authors: Hubrich Simeon , Joulaian Meysam , Di Stolfo Paolo , Schröder Andreas , Düster Alexander
Published: October 2016

The finite cell method is based on a fictitious domain approach, providing a simple and fast mesh generation of structures with complex geometries. However, this simplification leads to intersected cells where the standard Gauss quadrature does not perform well. To perform the numerical integration of these cells, we use the moment fitting approach that generates an individual quadrature rule for every broken cell. In this paper, we will perform a non‐linear optimization approach to find the optimal position and number of the integration points. The findings show that the proposed method leads to efficient quadrature rules that require less integration points than other existing integration methods. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Post‐critical behaviour of delaminated composite struts
Authors: Köllner Anton , Völlmecke Christina
Published: October 2016

Postbuckling responses of delaminated composite struts are semi‐analytically modelled. The model used allows to describe the postbuckling behaviour beyond the state where delamination growth is initiated. In the current work, a multi‐layered composite strut of differently stacked transversally isotropic unidirectional layers is investigated. A pre‐existing delamination is assigned in between two layers. By using only four generalized coordinates postbuckling responses incorporating delamination growth are determined. © 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The stresses in single lap joints with a functionally graded adhesive bondline: an efficient modelling approach
Authors: Mardani Houman , Stein Nicolas , Becker Wilfried
Published: October 2016

In this work, an efficient analytical model for the stress analysis of single lap joints with a functionally graded adhesive bondline is proposed which considers peel as well as shear stresses in the adhesive. The model takes into account the nonlinear geometric characteristics of a single lap joint under tensile loading and allows for the analysis of various adhesive Young's modulus variations. The obtained stress distributions are compared to results of detailed Finite Element analyses and show a good agreement for several single lap joint configurations. In addition, different adhesive Young's modulus distributions and their effect on the peel and shear stresses are studied and discussed in detail. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient nonlinear reanalysis for structural modifications
Authors: Materna Daniel
Published: October 2016

In this paper an approach for nonlinear reanalysis based on residual increment approximations (RIA) is presented. The method requires only the evaluation of residual vectors, which can be done very fast and efficient. Moreover, the results are improved by using a rational approximation method. The approach is general and can be applied to linear and nonlinear problems with different kind of design modifications. Furthermore, the proposed method is very efficient and easily to implement in existing finite element programs. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
p‐version finite elements and finite cells for finite strain elastoplastic problems
Authors: Taghipour Aliakbar , Parvizian Jamshid , Heinze Stephan , Düster Alexander
Published: October 2016

In this paper, the p‐version finite element method and its fictitious domain extension, the finite cell method, are extended to the finite strain J2 plasticity. High‐order shape functions are used for the finite element approximation of volume‐preserving plastic dominated deformations. The accuracy and efficiency of p‐version elements and cells in the finite plastic strain range are evaluated by the computation of two benchmark problems. It is shown that they provide locking free behavior and simplified meshing. These results are verified in comparison with the results of h‐version elements in F‐bar formulation. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Subspace‐Based Reduced‐Order Modeling Methods for Structural Dynamic Systems
Authors: Tegtmeyer Stefanie , Nackenhorst Udo
Published: October 2016

Computational costs for detailed Finite Element approximations can be reduced by using reduced‐order models instead. In this contribution, four subspace‐based reduced‐order modeling methods are compared. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Eigenpath analysis of rotating mechanical systems based on ALE formulation
Authors: Weidauer Tim , Willner Kai
Published: October 2016

When bodies rotate they are subjected to velocity‐dependent gyroscopic and inertia effects, which alter the dynamic behaviour of the structure. Analysing its eigenpairs consisting of eigenvalues and eigenvectors, these parameter‐dependent changes can be tracked as eigenpaths by means of a continuation algorithm as in [1]. For rotationally symmetric structures an ALE approach (ALE = Arbitrary LAGRANGIAN‐EULERIAN) for the finite element method as described in [2] can be employed. It allows simulating rotational influences on the body without actually having to rotate the mesh of the structure itself. This still‐standing mesh facilitates further steps like coupling of other, static components with the rotating body. The combination of ALE with eigenpath analysis including an example is described in the following. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of stiffness analysis of rubber material applied in resilient wheel
Authors: Zhang Le , Markert Bernd
Published: October 2016

Resilient wheels are well‐known for their contribution to prevent squealing, impact noise and dynamic stresses on unsprung masses. In this study, a FE model is established in ABAQUS to analyze the stiffness of resilient wheels based on the Mooney‐Rivlin hyperelastic material theory. The modes of each part in the resilient wheel and the whole wheel are calculated. The static and dynamic stiffness of the resilient wheel are analyzed. The simulation shows that the resilient wheel can reduce the dynamic loads both in the lateral and vertical directions between the vehicle and the track. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Self‐Resonant System ‐ Experimental Investigations of Boundary and Operating Conditions
Authors: Aboulfotoh Noha , Krack Malte , Twiefel Jens , Wallaschek Jörg
Published: October 2016

This contribution introduces the setup of a self‐resonating system consisting of a freely‐sliding mass over a vibrating elastic beam under harmonic excitation. Under specific operating regime, the slider shows tendency to move and adapt its position to where the whole system resonates. The behavior of the slider during that motion is investigated. Experimental observations of the operating regime dependency on some parameters are provided. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Approximation of quasi‐periodic solutions of a rotor in two‐lobe bearings with time‐varying geometry
Authors: Becker Kai , Seemann Wolfgang
Published: October 2016

Improving the dynamic behaviour of rotor systems in journal bearings represents an ongoing topic of research. The pressure distribution within journal bearings is described by the Reynolds equation, whereby unwanted oscillations can be caused by the fluid‐solid interaction within the bearings. An approach of a two‐lobe bearing with time‐varying geometry is suggested to suppress or at least to reduce occurring oscillations. In order to systematically analyse the system, a spectral reduction is performed, allowing to handle also quasi‐periodic behaviour by means of numerical continuation algorithms. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the rotordynamic stability of two‐pole synchronous electric machinery considering different load cases
Authors: Boy Felix , Hetzler Hartmut
Published: October 2016

This paper discusses stationary rotordynamics of synchronous electric machinery, considering different load cases. The model comprises the electrical operation in a rigid network and in an isolated condition. The mechanical part is modelled as a Laval Rotor (Jeffcott Rotor) with a noncircular shaft, accounting for both static‐ and dynamic rotor eccentricities. The results show, that the machine's electrical operation may influence the occurence of mechanical vibrations significantly and therefore demonstrate the importance of analysing the electromechanical interaction. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamics of a rotor partially filled with a viscous incompressible fluid
Authors: Kern Dominik , Jehle Georg
Published: October 2016

A rotor partially filled with a viscous incompressible fluid is modeled as planar system. Its structural part, i. e. the rotor, is assumed to be rigid, circular, elastically supported and running with a prescribed time‐dependent angular velocity. Both parts, structure and fluid, interact via the no‐slip condition and the pressure. The point of departure for the mathematical formulation of the fluid filling is the Navier‐Stokes equation, which is complemented by an additional equation for the evolution of its free inner boundary. Further, rotor and fluid are subjected to volume forces, namely gravitation. Trial functions are chosen for the fluid velocity field, the pressure field and the moving boundary, which fulfill the incompressibility constraint as well as the boundary conditions. Inserting these trial functions into the partial differential equations of the fluid motion, and applying the method of weighted residuals yields equations with time derivatives only. Finally, in combination with the rotor equations, a nonlinear system of 12 differential‐algebraic equations results, which sufficiently describes solutions near the circular symmetric state and which may indicate the loss of its stability. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sensitivity of Computational Rotor Dynamics Towards the Empirically Estimated Lubrication Gap Clearance of Foil Air Journal Bearings
Authors: Leister Tim , Baum Christoph , Seemann Wolfgang
Published: October 2016

This contribution is concerned with the computational analysis of a rigid rotor supported by means of two self‐acting foil air journal bearings. Even though the overall equation system is thereby typically written in a nondimensional form, prior knowledge about realistic value ranges of occurring dimensionless numbers is required in order to parameterize and interpret such simulations correctly. Unlike all other quantities, the nominal lubrication gap clearance between the rotating journal and the undeformed foil structure is reported to be only poorly known. Thus, even in the light of an advanced understanding of the bearing rotor system's fundamental behavior, the quantitative reproduction and prediction of experimental results by means of computational analysis need to be viewed critically. In this study, the sensitivity of numerical results towards the assumed nominal lubrication gap clearance will be investigated. To this end, the stability of the system is considered and the characteristics of occasionally observed equilibrium points and limit cycles are addressed. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Grenzen numerischer und experimenteller Modelluntersuchungen am Beispiel Regen‐Wind induzierter Schwingungen
Authors: Seidel Christian
Published: October 2016

An schlanken, geneigten Zylinderstrukturen wie Kabeln von Schrägkabelbrücken und Hängebrücken, Hängern von Bogenbrücken oder an Abspannseilen kann bei gleichzeitigem Auftreten von Regen und Wind das hydroaeroelastische Phänomen der Regen‐Wind induzierten Schwingungen beobachtet werden. Die komplexen Strömungsvorgänge des Phänomens bedingen die Entwicklung eines hybriden Modells. Diese halbanalytischen/halbnumerischen und halbexperimentellen Verfahren zeigen Grenzbereiche zwischen Numerik und Experiment, deren physikalisch sinnvolle Beschreibung und Erklärung nur mit Hilfe der Kombination von numerischen und experimentellen Untersuchungen gelingt. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Minimization‐ and Saddle‐Point‐Based Modeling of Diffusion‐Deformation‐Processes in Hydrogels
Authors: Böger Lukas , Nateghi Aref , Miehe Christian
Published: October 2016

Hydrogels have gained importance during the last years due to their wide range of synthetically fabricable elastic properties as well their increasing meaning in biomedical applications. Future exploitation of the vast prospects of hydrogels is however only feasible by establishing reliable material models that precisely capture their behavior in different environments. To this end, we propose a consistent variational framework for deformation‐diffusion processes, offering a canonically compact approach to the chemo‐mechanical coupling of hydrogels via a saddle‐point as well as a new minimization formulation. The work depicts the construction of rate‐type potentials for the chemo‐mechanical evolution problem and their transformation into time‐discrete incremental potentials. In terms of spatial discretization, the finite element method is employed, benefiting from the intrinsic symmetric structure of the variational foundation. While the saddle‐point formulation yields the well‐known LBB condition as a constraint for finite element interpolations, on the part of its minimizing counterpart H(Div, ℬ︁)‐conforming elements have to be chosen. We illustrate appropriate solutions to both challenges, using mixed Taylor‐Hood for the saddle‐point and Raviart‐Thomas elements for the minimization formulation and discuss advantages of the new approach. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A numerical framework for rheological models based on the decomposition of the deformation rate tensor
Authors: Donner Hendrik , Ihlemann Jörn
Published: October 2016

In this contribution, the rheological models based on the decomposition of the deformation rate tensor, as proposed by Palmow (1984), is combined with the numerical solution of objective tensorial ODEs as published by Rashid (1993). The resulting framework is suitable to model the complex inelastic properties of many materials at large strains. As an example, the Schwedoff model, which is appropriate for the simulation of metal forming processes, is analyzed within a cyclic simple shear test. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some Basic Ideas for the Simulation of Wave Propagation in Microstructures using Proper Orthogonal Decomposition
Authors: Fangye Yannick F. , Weber Wolfgang E. , Zastrau Bernd W. , Balzani Daniel
Published: October 2016

For the modeling of micro‐heterogeneous materials, models are required that take into account the microstructure. More and more, computational homogenization is used to quantify the effective macroscopic response. The large number of resulting microscopic boundary value problems need to be solved efficiently. To reduce the computational effort and simulation time, model reduction methods may be applied. In this contribution the performance of the proper orthogonal decomposition is analyzed for the wave propagation in fiber reinforced materials. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of a chassis bushing with regard to strain induced softening of filled rubber
Authors: Gelke Sören , Ihlemann Jörn
Published: October 2016

A material model is presented, which describes the material behavior of rubbery materials in the case of uniaxial tension/compression. It includes the characteristic nonlinearity of rubber at large strains as well as strain induced softening called Mullins effect. The generalization to arbitrary deformations is done with the concept of representative directions, published by Freund & Ihlemann [2] utilizing a numerical integration on a unit sphere. An FE simulation of a chassis bushing shows that the Mullins effect is reproduced appropriately, verifying the preceding material characterization. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Loss of ellipticity in additive logarithmic finite strain plasticity and related results on Hencky‐type energies
Authors: Ghiba Ionel‐Dumitrel , Neff Patrizio , Martin Robert J.
Published: October 2016

The aim of this paper is to present some results regarding the Legendre‐Hadamard ellipticity and loss of ellipticity of some energies depending on the logarithmic strain tensor. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the composites consisting of randomly distributed fibers
Authors: Ilie Ruxandra
Published: October 2016

The results highlight and interpret the testing and properties of natural fibre composites including, non‐destructive and high strain rate testing. The potential of this material for noise enclosures is investigated by using a coupled method cnoidal – Extended Finite Element Method (XFEM). XFEM enables the accurate approximation of solutions with jumps, discontinuities or general high gradients across interfaces. The dissipation of the sound power into a plate/cavity system shows the efficiency of this composite to achieve noise reduction better to that obtained at low and higher frequencies with traditional foams. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A general modelling framework and specific mechanical approaches to simulate curing phenomena in polymers
Authors: Landgraf Ralf , Ihlemann Jörn
Published: October 2016

Polymers are employed as adhesives, filling or sealing materials, among others. Within these applications, a chemical reaction (e.g. polymerization) leads the materials to cure from a liquid to a solid. In this contribution, first a general continuum mechanical modelling framework for the simulation of curing phenomena is highlighted. It takes into account the main chemical, thermal and mechanical phenomena of polymeric curing processes. Secondly, different mechanical models to capture the mechanical behaviour of polymeric curing processes are regarded. It is shown that elastic, viscoelastic and viscoplastic models at large deformations can be employed. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational Excavation Analysis of a Single Cutting Tool using a Hypoplastic Constitutive Model
Authors: Leon Abdiel Ramon , Dang Thai Son , Meschke Günther
Published: October 2016

We propose a computational model for the numerical analysis of the dynamic interaction between a single excavation tool and the surrounding soil. An incremental non‐linear (hypoplastic) constitutive model is employed to capture the complex response of soft soils. Large displacements and deformations are handled by an Updated Lagrangian formulation, the particle finite element method (PFEM). (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Localized modes at defects in sonic composites
Authors: Moşneguţu Valerica
Published: October 2016

The paper discusses a sonic composite consisting of an array of silicone rubber coated hollow steel cylinders embedded in an epoxy matrix, with linear defects. Such structures allow localization of modes in the vicinity of the line defect with propagation along this line. The material in the vicinity of the line behaves like frequency‐specific mirrors. The mirrors localize waves within a finite region of the line defect, and modes are quantized into discrete frequencies. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the non‐periodic multilayer films
Authors: Munteanu Ligia
Published: October 2016

The non‐periodic multilayer film is studied in order to discern some of the most important features of periodic sonic composites, such as the full band‐gaps and modes that are localized around defects. The band‐gap for different number of Cantor elements into the film is analysed by taken into account the role of the fracton and phonon vibration regimes in the wave propagation. The film can prohibit the propagation of Lamb waves in the Ox1 direction. The band‐gap is generated in the band structure of the structure, meaning that the surface waves are forbidden to propagate with certain frequencies in the Ox1 direction. The structure of the band‐gaps for different number of Cantor elements into the film is analysed. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Extended balance of linear momentum from higher gradient stress field theory
Authors: Münch Ingo , Wöhler Franziska
Published: October 2016

We present the equation of linear momentum considering higher gradients for stress and body force. Both are approximated via Taylor series expansion within a finite Cauchy cube of dimensions Lc. Whereas linear terms of the series expansion result to the classical balance of linear momentum, terms up to third order yield an extended balance equation. The extension includes an internal length scale L2c caused by surface integrals on the cube. The approach makes use of Cauchy's theorem and standard Newtonian mechanics but constitutive assumptions are not applied. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constitutive modeling of ferromagnetic and ferroelectric behaviors and application to multiferroic composites
Authors: Avakian Artjom , Ricoeur Andreas
Published: October 2016

In this paper, the constitutive modeling of nonlinear multifield behavior as well as the finite element implementation are presented. Nonlinear material models describing the magneto‐ferroelectric or electro‐ferromagnetic behaviors are presented. Both physically and phenomenologically motivated constitutive models have been developed for the numerical calculation of principally different nonlinear magnetostrictive behaviors. Further, the nonlinear ferroelectric behavior is based on a physically motivated constitutive model. On this basis, the polarization in the ferroelectric and magnetization in the ferromagnetic and magnetostrictive phases, respectively, are simulated and the resulting effects analyzed. Numerical simulations focus on the calculation of magnetoelectric coupling and on the prediction of local domain orientations going along with the poling process, thus supplying information on favorable electric‐magnetic loading sequences. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time‐adaptive non‐linear finite‐element computations for thermo‐mechanically coupled analysis in inelastic dynamical systems
Authors: Grafenhorst Matthias , Hartmann Stefan , Rang Joachim
Published: October 2016

In structural dynamics the initial boundary‐value problem has to be solved in the space and time domain. The spatial discretization is done using finite elements yielding systems of differential equations of second‐order. Incorporating inelastic material properties, thermo‐mechanical coupling and particular Dirichlet boundary conditions essentially changes the underlying mathematical problem. The main goal is to provide higher‐order time integration schemes using diagonally‐implicit Runge‐Kutta methods (DIRK) and the Generalized α‐method consistently applied to the semi‐discretized ODE‐system comprising the semi‐discretized equations of motion, the unsteady semi‐discrete heat equation and constitutive equations of evolutionary‐type. Furthermore, we want to show the applicability of time‐adaptivity by embedded schemes so that step‐sizes are chosen automatically. The inelastic constitutive equations are given by a thermo‐viscoplasticity model of Perzyna/Chaboche‐type with non‐linear kinematic hardening. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magneto‐Structural analysis of rotating electrical machines
Authors: Haas Stefan , Mair Mathias , Ellermann Katrin
Published: October 2016

The vibrations of the stator core of a rotating electrical machine induce acoustic noise. These oscillations of the stator yoke are excited of the force density due to the magnetic field in the air gap. This requires a transient magnetic field analysis coupled with a dynamic mechanical analysis. Coupling these two different physical fields results in a high numerical effort and usually one direction of the interaction is disregarded. This paper presents a method to calculate the vibrations of a stator core under design operating conditions. For this purpose, harmonic electromagnetic excitation forces have been calculated in a linear magnetic field analyses using the finite element method. The resulting forces have been applied to a linear structural dynamic FE model in the frequency domain. The results of the calculations are harmonic velocities specified by amplitude and phase from the structural surface of the stator core. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A ternary phase bi‐scale FE‐model for diffusion‐driven dendritic alloy solidification processes
Authors: Henning Carla , Moj Lukas , Ricken Tim
Published: October 2016

It is of high interest to describe alloy solidification processes with numerical simulations. In order to predict the material behavior as precisely as possible, a ternary phase, bi‐scale numerical model will be presented. This paper is based on a coupled thermo‐mechanical, two‐phase, two‐scale finite element model developed by Moj et al. [2], where the theory of porous media (TPM) [1] has been used. Finite plasticity extended by secondary power‐law creep is utilized to describe the solid phase and linear visco‐elasticity with Darcy's law of permeability for the liquid phase, respectively. Here, the microscopic, temperature‐driven phase transition approach is replaced by the diffusion‐driven 0D model according to Wang and Beckermann [3]. The decisive material properties during solidification are captured by phenomenological formulations for dendritic growth and solute diffusion processes. A columnar as well as an equiaxial solidification example will be shown to demonstrate the principal performance of the presented model. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of Multifield Processes Regarding the Life‐Cycle of Concrete Structures
Authors: Kowalsky Ursula , Cramer Friedhelm , Dinkler Dieter
Published: October 2016

The presented model allows for the description of the most important coupled processes in porous media, whereby focus is laid on concrete structures. It can be employed for a consistent numerical analysis within a monolithic solution algorithm. Mechanical processes are coupled with transport processes, e.g. of energy and humidity, as well as with chemical processes like depassivation due to chloride penetration, carbonation or dehydration. The coupled model enables the predictive analysis of the behaviour of concrete structures over their whole life cycle. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Smoothed Particle Hydrodynamics modelling of poroelastic media
Authors: Osorno Maria , Steeb Holger
Published: October 2016

Numerical modelling of poroelastic properties in porous media allows widely varied investigations at low costs and relatively short times. The study of porous media is of high interest at different scales, in this case we focus our analysis at meso‐ and macroscale which is highly relevant e.g. in geothermal explorations. We model a biphasic poroelastic media assuming incompressible fluid and solid grains and a large solid‐fluid density ratio.

Meshfree methods are nowadays more widely used due to the advantages that present in the simulation of large deformations. In this case we choose to employ the Smoothed Particle Hydrodynamics method (SPH), a Lagrangian method where the domain is discretized in particles. The solution is computed in parallel, which allows to simulate large domains more representative of the scale of our study cases.

We validate our implementation with a classical consolidation problem and compare the simulated diffusion process with Terzaghi's analytical solution. Future work includes simulation of fractures initiation and propagation in the porous media at reservoir scale. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Continuum modeling of the swelling behavior of concrete when modified through superabsorbent polymers
Authors: Sauerwein Malte , Jänicke Ralf , Steeb Holger
Published: October 2016

The main purpose of our investigation is to model the physical solidification process of a concrete mixture, involving water absorbing constituents, i. e. Superabsorbent Polymers (SAP). In order to model the chemo‐mechanical swelling process, the system is described within the framework of the Theory of Porous Media (TPM). The swelling process is accounted for by including mass exchange terms between free and absorbed water. The chemo‐mechanical driving forces are deduced from non‐equilibrium thermodynamics while constitutive relations are motivated by appropriate micro‐models of the swelling process. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical investigation of vacuum‐assisted resin transfer moulding (VARTM) within deformable fibre fabrics
Authors: Schenke Maik , Ehlers Wolfgang
Published: October 2016

The VARTM procedure is a manufacturing step in the production line when building parts made of fibre‐reinforced plastics (FRP), such as glass‐ or carbon fibre‐reinforced plastics acronymed GFRP or CFRP, respectively. In the VARTM process, an initially dry (gas‐saturated) fibre‐fabric is gradually impregnated by resin, where the flow process is, besides the driving injection pressure, governed by the mutual interactions between the fabric, the resin and the ambient air. To predict the mechanical properties of the manufactured structure, simulations are vital.

Within the present contribution, the simulation model proceeds from the macroscopic Theory of Porous Media (TPM), which intrinsically accounts for the interplay between the individual components, in particular, the fibre‐network, the ambient air and the resin, where the latter two simultaneously percolate through inter‐fibrous pore space. The underlying holistic modelling approach allows, on the one hand, for a continuous transition from the fully gas‐saturated towards the fully resin‐saturated state and, on the other hand, the consideration of the so‐called spring‐back effect. The presented simulation example investigates the model behaviour within a practically relevant application scenario. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two accuracy improvements on nonuniform transformation field analysis for plasticity coupled to softening
Authors: Ju Xiaozhe , Mahnken Rolf
Published: October 2016

A reduced order homogenization scheme for the case of plasticity coupled with softening effects is proposed. This is based on a straightforward extension of the so‐called nonuniform transformation field analysis (NTFA, [2]). Two related new methods, denoted as uneven NTFA and adaptive NTFA accounting for accuracy improvements, are also presented, which are based on the ideas of parameter identification and adaptive modeling, respectively. A complementary numerical study is given. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Linking macroscopic deformation processes to microstructure evolution using an FE‐FFT‐based micro‐macro transition and non‐conserved phase‐fields
Authors: Kochmann Julian , Ehle Lisa , Wulfinghoff Stephan , Svendsen Bob , Reese Stefanie
Published: October 2016

The purpose of this work is the multiscale FE‐FFT‐based prediction of macroscopic material behavior, micromechanical fields and bulk microstructure evolution in polycrystalline materials subjected to macroscopic mechanical loading. The macroscopic boundary value problem (BVP) is solved using implicit finite element (FE) methods. In each macroscopic integration point, the microscopic BVP is embedded, the solution of which is found employing fast Fourier transform (FFT), fixed‐point and Green's function methods. The mean material response is determined by the stress‐strain relation at the micro scale or rather the volume average of the micromechanical fields. The evolution of the microstructure is modeled by means of non‐conserved phase‐fields. As an example, the proposed methodology is applied to the modeling of stress‐induced martensitic phase transformations in metal alloys. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improving the convergence behavior of hierarchical atomistic‐to‐continuum multiscale models using stochastic approximation
Authors: Wurm Patrick , Ulz Manfred H.
Published: October 2016

The aim of this work is to provide an improved information exchange in hierarchical atomistic‐to‐continuum models by applying stochastic approximation (SA) methods. A typical hierarchical two‐scale model is chosen and enhanced. Due to very high computational cost, the microscale of this model may not be sufficiently sampled in practical calculations; a problem, which was recently investigated in [1]. As a consequence, the microscale produces noise‐corrupted output due to thermal effects. The thermal noise creates a setting that shows remarkable resemblance to the Robbins‐Monro iteration scheme known from SA. This resemblance justifies the use of two averaging strategies known to improve the convergence behavior of SA schemes under certain, fairly general, conditions. No additional computational cost is introduced by this approach. The proposed strategies implemented in the multiscale model are tested on a numerical example. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of Effective Properties of MMC by Computational Homogenization
Authors: York Duran José L. , Kuhn Charlotte , Müller Ralf
Published: October 2016

On the macrolevel Metal Matrix Composites (MMCs) resemble a homogeneous material. However, on the microlevel they show an inhomogeneous microstructure. This paper will have how heterogeneities affect the overall properties and the behaviour of a material (i. e. the effective properties). This is done using computational homogenization techniques. Finite element (FE) simulations were conducted in ABAQUS in connection with MATLAB, using material parameters for aluminium alloy AA2124 and SiC to develop a representative volume element (RVE) of the MMC AMC217xe. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transient contraction flow of a nonlinear viscoelastic fluid
Authors: Descher Stefan , Wünsch Olaf
Published: October 2016

The unsteady behavior of a Phan‐Thien‐Tanner fluid in a pressure driven contraction flow is investigated. Calculations are performed using the log‐conformation reformulation and block coupled pressure correction. Studies are carried out for the Deborah number De of the process and the model's extension parameter α. It is shown that for very small and very large De the fluid responds newtonian whereas for moderate De damped oscillations of the volume flux can be observed. The studies for α show that the flow is shear dominant despite the extensional flow character of contractions. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)