Herbert Baaser

Herbert Baaser
University of Applied Sciences Bingen · Mechanical Engineering

Prof. Dr.-Ing. habil.

About

114
Publications
20,136
Reads
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314
Citations
Introduction
* implementation of anisotropic extension of "exponentiated Hencky-logarithmic model (Comp.Mech., Nov. 2017)" into DAEdalon.org and ABAQUS * modeling of elastomer-hysteresis and ampl. dependency * simulation of polygon connections (shaft-hub-connections)
Additional affiliations
September 2015 - present
Bingen University of Applied Sciences
Position
  • Professor
Description
  • Engineering Mechancis & Finite Element Analysis
October 2013 - present
Technische Universität Darmstadt
Position
  • Professor (Associate)
Description
  • nonlinear material modeling & parameter calibration within ABAQUS, ANSYS and/or MSC.MARC
September 2003 - August 2015
Bingen University of Applied Sciences
Position
  • Lecturer
Description
  • Mechanics, basic course, FEM

Publications

Publications (114)
Chapter
We reconsider anti-plane shear deformations of the form φ(x) = (x1 , x2 , x3 + u(x1, x2)) based on prior work of Knowles and relate the existence of anti-plane shear deformations to fundamental constitutive concepts of elasticity theory like polyconvexity, rank-one convexity, and tension-compression symmetry. In addition, we provide finite element...
Article
This article describes the simulation setup and the development of a simulation method for modeling the self-heating of cyclic-loaded rubber components within the well-known ABAQUS FE environment. ln this context, well-founded knowledge about the mechanical and thermal behavior of elastomers can be obtained , so that technically specific statements...
Poster
Full-text available
Task: Modeling of a rubber body of a conical spring in Abaqus, which is loaded by a cyclic load. Subsequent consideration of the local amplitudes of the shear strain. Automation of the process. Excel output of selected shear strain components. Analysis of the amplitudes of the shear strains. Analysis of the component behavior regarding stiffness FF...
Poster
Full-text available
The modeling of linear viscoelasticity is prepared for simple shear and implemented in PYTHON including a GUI - to gamble with. A special focus of the work is on the self-heating of cyclically loaded rubber components ... and the dependence on the amplitude, which we are now investigating (again) in more detail. We provide the PYTHON program as * ....
Poster
Full-text available
As an example, we examined M8 screw heads with regard to their possibility of torque transmission from the tool. We would be grateful for your feedback and information on similar results.
Presentation
Full-text available
We show recent results as summary of our FEM project within the last winter term: We combined "FreeCAD" (as preproc.), "DAEdalon" (as solver) and "ParaView" (as postproc.) within a Python environment controling the procedure in order to obtain an easy-to-use FE appliction. See github for download and collaboration.
Presentation
Full-text available
We won a small prize in an internal competition: The online monitoring of a life-cycle testing machine for elastomers is now transferred to an info monitor. With this, we practice and show a bit of 'predictive maintanance' in the context of "Industry 4.0".
Article
Full-text available
We reconsider anti-plane shear deformations based on prior work of Knowles and relate the existence of anti-plane shear deformations to fundamental constitutive concepts of elasticity theory like polyconvexity, rank-one convexity and tension–compression symmetry. In addition, we provide finite element simulations to visualize our theoretical findin...
Article
This article describes the design, construction and operation of an experimental testing machine as part of student works, and deals with the sequence and results of a series of elastomer samples. ln the course of these experiments, data is collected on the fatigue behavior under swelling, harmonic tensile load. The phase shift between input and ou...
Presentation
Full-text available
GAMM expert meeting on "experimental mech.": Construction and application of simple dynamic tension test on uniaxial rubber specimens. Discussion of test rig and educational aspects to students.
Conference Paper
Full-text available
We reconsider anti‐plane shear deformations of the form ϕ(x) = (x1, x2, x3 + u(x1, x2)) based on prior work of Knowles and relate the existence of anti‐plane shear deformations to fundamental constitutive concepts of elasticity theory like polyconvexity, rank‐one convexity and tension‐compression symmetry. In addition, we provide finite‐element sim...
Presentation
Full-text available
Rheological models consisting of an arbitrary arrangement of springs, dampers and friction elements are often used to motivate and explain advanced constitutive models for specific material behavior. In the uniaxial case, this procedure results in differential equations of higher order whose solution describe the proposed constitutive behavior. Man...
Conference Paper
Full-text available
Experimental findings on material samples often show a nonlinear behavior that can not be classified immediately. Depending on the experiment, different phenomena occur, which must be classified. For example, only by a unloading process, it becomes clear whether one would call a (non–linear) curve as ”plastic”, ”viscous”, or even ”elastic”. Futherm...
Presentation
Full-text available
Implementation of (extended) hyperelastic material models by automatic code generation; here: simulation of stress softening
Article
Full-text available
We investigate a finite element formulation of the exponentiated Hencky-logarithmic model whose strain energy function is given by W eH (F) = µ k e k dev n log U 2 + κ 2 ˆ k e ˆ k[tr(log U)] 2 , where µ > 0 is the (infinitesimal) shear modulus, κ > 0 is the (infinitesimal) bulk modulus, k andˆkandˆ andˆk are additional dimensionless material parame...
Article
Full-text available
The complex mechanical behaviour of filled elastomers comprises several nonlinear and dissipative effects, one of them is stress softening. Previous model approaches to stress softening show difficulties both in their representation of the stress behaviour of filled elastomers and their complexity with respect to an FE implementation. These problem...
Presentation
Full-text available
We discuss the FEM implementation of typical hyperelastic material models into commercial FE codes by the help of automatic code generation tools resulting in stable and efficient steps. The application is shown on three representative examples.
Presentation
Full-text available
Overview - modeling & simulation of rubber behaviour - application to FEM
Article
Full-text available
We reconsider anti-plane shear deformations of the form $\varphi(x)=(x_1,\,x_2,\,x_3+u(x_1,x_2))$ based on prior work of Knowles and relate the existence of anti-plane shear deformations to fundamental constitutive concepts of elasticity theory like polyconvexity, rank-one convexity and tension-compression symmetry. In addition, we provide finite-e...
Negative Results
Full-text available
We demonstrate an error in the implementation of the popular commercial Finite-Element-System Abaqus by an explicit and simple example. This error has previously been brought to attention by Ba\v{z}ant et al. who, in a series of papers, pointed out that the umat user interface subroutine returns erroneous results for nonlinear elastic models of hig...
Presentation
Full-text available
The basic open problem of nonlinear elasticity theory is to find a meaningful formulation for the basic elasticity for describing the material behavior of elastomer components in order to obtain reasonable parameter calibrations in the range of large deformations. The exponential HENCKY energy based on the logarithmic strain tensor ε = log λ combin...
Conference Paper
Full-text available
The basic open problem of nonlinear elasticity theory is to find a meaningful formulation for the basic elasticity describing the material behavior of elastomer components in order to obtain reasonable parameter calibrations in the range of large deformations. The exponentiated HENCKY energy in (Neff, Ghiba, & Lankeit 2015) based on the logarithmic...
Chapter
The article shows the basics and the fundamental procedure for solving nested calculations of a multistage sequence, taking the example of a compressed O-ring seal influenced by diffusion processes and the ageing of the elastomer component. The mathematical structure of the descriptive equation of diffusion is the same as that of heat transfer. On...
Conference Paper
Full-text available
We present the training of artificial neural networks (ANN) on elastomer compounding using the MATLAB ANN toolbox. The results for two compounding series are shown as first examples. The first series is based on an EPDM rubber and varies eight input variables (2 coagents, 2 crosslinkers and 4 fillers) whereas the second ACM based series uses 9 inpu...
Article
Fabric or continuous fiber reinforced rubber components (e.g. tires, air springs, industrial hoses, conveyor belts or membranes) are underlying high deformations in application and show a complex, nonlinear material behavior. A particular challenge depicts the simulation of these composites. In this contribution we show the identification of the st...
Conference Paper
Full-text available
We apply an endochronic plasticity model on technical rubber components in order to describe quasi-static elastomeric inelasticity such as MULLINS effect, hysteresis and remaining strains by a finite element model. Kernel idea of that model is the introduction of an internal time scale (”endochron” - Greek), which is increased by the deformation of...
Conference Paper
Full-text available
As a rule, for the preliminary design of a sealing system which, in this case, consists of an O-ring as a rod seal and housing, designs are created which can be considered as a compromise from the imposed customer requirements. Such customer requirements can relate to the installation space, the system pressure, the media to be sealed and general t...
Article
Full-text available
What is the Young's modulus and the Poisson ratio of vulcanized rubber? These questions related to the desire to simulate elastomer components by the finite element method are obvious for over three decades. The importance of these issues has increased with increasing customer requirements on simulations during the development of rubber components...
Article
Full-text available
These questions related to the desire to simulate elastomer components by the finite element method are obvious for over three decades. The importance of these issues has increased with increasing customer requirements on simulations during the development of rubber components by further increasing opportunities in hardware and software. Here are s...
Article
Full-text available
The finite element method (FEM) has been established for the design of elastomer components and is today used in practice in the development process of such components. Similarly, fibre- and fabric-reinforced rubber components are designed to meet increased loads. The simulation of these components poses a challenge and is an object of research. Th...
Article
Full-text available
The description of (quasi-)incompressible materials such as elastomers is well established in modern continuum mechanics for many years now as well as from a theoretical background as in the numerical implementation in commercial software packages in the context of finite elements. Nevertheless, some questions arise in the practical application of...
Article
Full-text available
In this contribution we compare the results of a jumping rubber ball experiment to FE-simulations. For this purpose we apply two formulations of finite strain viscoelasticity. The experiment is observed by a high speed camera to catch the time range in between two floor contacts. The FE-formulations are based on an integral formulation and on a dif...
Conference Paper
Full-text available
Shortening product life-cycle times, the demand for more intense loading and at the same time for more reliable operation call for generally applicable tools for the evaluation of the life-time of dynamically loaded rubber products. Today, engineers apply more or less sophisticated procedures to estimate the life-time of components. All of these pr...
Article
Full-text available
For the efficient dimensioning of elastomer parts the structural simulation by means of Finite Element Analysis (FEA) has developed to be an indispensable tool. For the calibration of these models often only uniaxial tensile tests are conducted to estimate the material parameters. However since technical elastomer parts are usually multiaxially loa...
Article
Full-text available
In der Automobilzulieferindustrie kann die Simulation von Elastomerbauteilen einen erheblichen Kosten- und Zeitgewinn bedeuten. Dabei interessieren die Lebensdauervorhersage bei bestimmten Funktionen wie der Dichtigkeit von Radialwellendichtringen und O-Ringen oder das dynamische Verhalten von Lager und Dämpfer. Neue Entwicklungen bei Freudenberg e...
Article
In the automotive supply industry, the simulation of elastomer components offers major savings in costs and time. One area of interest is the lifetime prediction for certain functions, such as the tightness of radial shaft seals and O-rings or the dynamic behaviour of bearings and dampers. New developments from Freudenberg make this work easier.
Chapter
In this section we describe the usage of the general purpose 2d- or 3d-truss element as described before in Sec. 4.6.4 for small strain regime by a real-sized engineering example. Obviously, the following model of a building site crane is very simplified, but it shows quite impressively the capacity of the finite element method in order to obtain n...
Chapter
Starting this chapter, where we describe the realization of DAEdalon within the Matlab environment, we quickly itemize the main features of Matlab operating on vector and matrix representations, respectively. This list can not substitute a deeper study of the printed Matlab manuals or any tutorial obtained from the internet or even the built-in hel...
Chapter
Some years ago, in 2000, as we started with the basic concept and architecture of DAEdalon, along with the main, first focus of the FE system — namely the numerical treatment in the sense of a global system of Differential Algebraic Equations, see Eckert et al. [2003] and Ellsiepen & Hartmann [2001] — we intend to find a senseful name, which was al...
Chapter
The description of any material behavior within a finite element simulation requires a clearly structured interface within an element formulation. As stated before in (2.36), in Sec. 2.6.4 and in (2.53), the (local) material behavior is respected and needed for at the integration points while the integration loop on element level. According to the...
Chapter
We quickly resume the mathematical and mechanical preliminaries of modern textbooks like Holzapfel [2000] in order to describe positions and motions of material points within any body of consideration. Further on, this enables us to define as well strains and stresses as gives finally a representation of mechanical equilibrium.
Chapter
The latest and stable version of DAEdalon is provided for download at the URL http://www.DAEdalon.org in order to obtain a tar-file, which can be unpacked with any usual archive program. Doing so, one gets a folder and file structure with ../DAEdalon_v2.00 as kernel followed by a substructure which is necessary for a run of the system. Please set y...
Book
The intention of this booklet is a brief but general introduction into the treatment of the Finite Element Method (FEM). The FEM has become the leading method in computeroriented mechanics, so that many scienti?c brancheshavegrownup besides overthelastdecades. Nevertheless,theFEM today is a question of economy. On the one hand its industrial applic...
Article
Full-text available
A challenging task for future developments in the rubber industry is a virtual material design based on computer simulations. In this paper, we are presenting a basic study of polymer-filler interaction by modeling adhesion behavior through constitutive-like assumptions for the interface. We treat EPDM with glass spheres as a filler and examine agg...
Conference Paper
Full-text available
In this article, we summarize the fundamental deformation modes for incompressible elastomer materials and point out suitable attempt guidance. The at first arbitrary choice of a material model in form of a strain energy function gives the form and number of material parameters, which are to be adapted by a suitable approximation method in the best...
Article
A material model is presented to describe inelastic effects in elastomeric components. In static cases, stress softening and permanent deformations are identified as cause of inelasticity. Both effects are covered separately in the constitutive law. This permits the largely modular design of a material description on the basis of user interfaces in...
Article
Brake hoses are one of the most safety relevant parts in a motor vehicle. They conduct the information of a breaking event from the brake pedal to the breaking devices at the wheels by oil pressure. At the same time, the brake hose is very flexible in bending behaviour to follow the wheels movement depending on the steering and on the spring system...
Article
Brake hoses are one of the most safety relevant parts in a motor vehicle. They conduct the information of a breaking event from the brake pedal to the breaking devices at the wheels by an increasing pressure of the brake fluid. This requires a lifelong impermeability and an absolute pressure stability in such a way as no pressure leakage occurs in...
Article
When describing elastic-plastic material behavior with the finite element method (FEM), a system of differential-algebraic equations (DAE) has to be solved. In contrast to the classical ‘elastic predictor–plastic corrector’ method, a unified approach is applied, where all unknowns are treated as global quantities. Therefore the DAE-system has to be...
Article
The exponential update formalism is applied to an integration algorithm for rate–independent single crystal plasticity to fulfill the compelling constraint of plastic incompressibility. The exponential function of a non–symmetric tensor valued argument is expressed in terms of the Padé–approximation, which is capable to approximate the matrix expon...
Article
Simulating elastic-plastic material behavior with the finite element method (FEM), two different types of equations appear. The spatial discretization of the considered domain leads to a system of nonlinear equations for the unknown displacements, whereas the time-evolution of the internal variables describing the inelastic state is governed by fir...
Book
This book is devoted to the deformation and failure in metallic materials, summarizing the results of a research programme financed by the "Deutsche Forschungsgemeinschaft". It presents the recent engineering as well as mathematical key aspects of this field for a broad community. Its main focus is on the constitutive behaviour as well as the damag...
Article
The growth of microvoids in a ductile material is analysed in front of a crack tip loaded by a remote KI field. For this purpose, a circular region with radius R around the crack tip containing statistically distributed initially circular microvoids of radii r is discretised. The material behaviour is described by classical J2 plasticity with power...
Article
The aim of this contribution is a demonstration of a new iterative approach for the algorithmic treatment of a nonlocal damage formulation in the scope of the finite element method. The damage model of Rousselier is used in a finite strain formulation to represent the material behaviour in the specimens of interest. The new method uses a set of con...
Chapter
Full-text available
Ductile crack initiation and growth is investigated by applying a three— dimensional finite element analysis in conjunction with a nonlinear damage model. This numerical procedure is formally restricted by the so—called loss of ellipticity due to a type change of the differential equations. A time—independent finite strain formulation is applied, b...