PAMM
Internal erosion processes are of vital importance for the risk management of geotechnical structures as well as for the understanding of the macroscopic mechanical and hydraulic properties of the subsoil in various man‐made constructions. Here, a 4‐phase continuum model is presented and numerically applied to illustrative applications. The role of interfacial area and related microstructural parameters...
In order to model the sound insulation properties of porous plate‐like structures, an adequate poroelastic plate theory is needed. The approach used here to obtain such a theory consists in expanding the primal variables into power series in thickness direction. This allows an analytical integration over the thickness, thus reducing the dimension of the problem from 3d to 2d. The resulting out‐of‐plane...
In engineering practice, the assessment of sensitivity is utilized to detect influential parameters in order to facilitate subsequent numerical simulation techniques. As sensitivity analyses are preprocessing methods for sophisticated numerical simulation techniques, e.g. reliability based optimization procedures, their application is always linked to an increase of the computational expense. In result,...
Within the development process of piezoelectric sensor and actuator applications, numerical tools are essential. These tools solve approximately the electromechanical boundary value problems received from physical descriptions. Since many piezoelectric components are generally thin rod like structures, a piezoelectric finite beam element is presented in this contribution which can be used effectively...
Sharp interface material models can be related to phase field models by introducing an order parameter, whose value is assigned to the different phases of a material. The elastic material law is coupled to the evolution equation of the order parameter and cracking is addressed as a phase transition problem instead of a moving boundary value problem. A regularization parameter ϵ controls the width...
In the present paper, the problem of deformation and damage of composites with a porous isotropic matrix and transversally‐isotropic unidirectional fibers under compressive loading is considered when microdamages are accumulated in the fiber. Fractured micro‐volumes are modelled by a system of randomly distributed quasi spherical pores. The Shleicher‐Nadai fracture criterion is used as a condition...
The linear crack located at the bimaterial interface between dissimilar homogeneous linearly elastic materials under normally incident harmonic tension‐compression wave is considered in the study. The problem is solved by the method of boundary integral equations using an iterative algorithm. The dynamic stress intensity factors are computed as functions of the loading frequency taking the contact...
A finite element formulation within the framework of the Strong Discontinuity Approach suitable for the simulation of crack growth is presented. The formulation allows for intersecting discontinuities and similarly to classical interface elements, the cracks are introduced parallel to the element facets. However and in contrast to interface elements, the discontinuities are directly embedded in finite...
An essential property of biological tissues in vivo is the ability to adapt according to respective loading conditions‐‐for example by changing its mass, shape, or internal structure, the latter for instance being associated with fibre reorientation and often denoted as remodelling. In this contribution, a three‐dimensional micro‐sphere‐based constitutive model for anisotropic soft biological tissue...
In algebraic reconstruction of images in computerized tomography we are dealing with rectangular, large, sparse and ill‐conditioned linear systems of equations. In this paper we describe a two‐grid algorithm for solving such kind of linear systems, which uses Kaczmarz's projection method as relaxation. The correction step is performed with a special “local” aggregation / disaggregation type procedure...
Especially from dry sliding contacts between solids the description of the friction by the law of Coulomb is well‐known. This law describes the relation between normal force and tangential force via the proportional factor μ, the coefficient of friction. This coefficient has to be derived empirically by experiments and is considered as being dependent only on the solid bodies' materials and surfaces...
It is shown that a standard model in crystal plasticity for which only rigid body motions have finite elastic energy can be approximated in the sense of Γ‐convergence by models with more general elastic potentials. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Particle methods can be used for the simulation of large deformations under large deformation rates which are e.g. characteristic for massive forming processes. Particles' dynamics have to be carefully chosen in order to describe heat and heat flows in a correct thermodynamic way. In the following, mesoscopic particle systems are used, which solve this problem by using internal variables and in addition...
Axially loaded cylindrical continuous shells collapse either globally like a rod (Euler buckling), or locally (local shell wall buckling), depending on the ratio of the length of the shell over the diameter [1]. There are many published investigations, which show that this behaviour is also true for Carbon Nanotubes CNTs [2]. In this work a systematic analysis of the problem is given in the framework...
The paper is concerned with experimental and numerical investigations of the turbulent flow over dimpled surfaces. Shallow dimples distributed regularly over the wall of a plane channel with large aspect ratio are used to study their effect on the skin‐friction drag. The resulting pressure drop in the channel was measured for smooth and dimpled walls. In addition to these investigations on internal...
The combustion engine produces huge rotational periodic vibrations that could affect the acoustic comfort of the vehicle. An isolating device is placed after the engine and filters the oscillations in order to deliver a clean averaged torque to the rest of the drive train. The centrifugal pendulum is widely used even though its passive version can quench only one order of vibration.
We propose in...
Phase field methods are a widely accepted tool for the approximation of moving free interfaces in sharp interface problems. Topological changes in the solution, such as nucleation or vanishing of particles or merging or pinching of interfaces, lead to singularities in the free boundary. In the sharp interface model, these singularities cause both numerical and theoretical problems, whereas they are...
Non‐Uniform Rational B‐Splines (NURBS) are basis functions used in CAD software to describe exact geometric models. The implementation of these basis functions in the context of the Finite Element Analysis (FEA) is known as isogeometric analysis. The concept and definition of NURBS is briefly presented here. Since these functions are implemented as shape functions for the isogeometric analysis, the...
The solution of a time‐periodic flow problem is expanded into a discrete Fourier series. This yields a large nonlinear system of equations which can be solved in parallel. We show for a one‐dimensional model problem that this method for the parallelization of the time domain converges in a robust and efficient manner. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The paper addresses the problem of a conducting rectangular bar of square cross‐section which is moving with constant velocity in the field of an arbitrarily oriented magnetic dipole. The braking Lorentz force on the bar is obtained by FEM and compared with the analytical solution for a moving infinite plate in the field of a magnetic dipole [2]. The computation of the induced currents requires solution...