PAMM
Piezoelectric ceramics are often used in active structures for shape and vibration control. Since the operation range is not limited to small signals the nonlinear behaviour of the actuator under high electric loads has to be known. There are several approaches in literature to model the hysteretic effects, each having its assets and drawbacks. When a model is able to reproduce the minor loops of...
We present an improved stochastic model concerning the lay‐down of fibers on a conveyor belt in the production of nonwovens. The model is based on stochastic differential equations describing the resulting position of the fiber on the belt having regard to its motion in the deposition region under influence of turbulent air flow. Our aim is to generalize an existing model to 3D. By introducing a parameter...
In this paper we consider the Aifantis' theory of consolidation with double porosity and we prove the uniqueness and existence theorems of solutions of basic boundary value problems (BVPs) of statics for the two‐dimensional finite and infinite domains. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Articular cartilage is a very resilient material which lines the bony ends in synovial joints and has a gel‐like hydrated structure reinforced by a collagen fibre network. Despite its high load‐bearing and almost frictionless low‐wear capabilities, the high dynamical contact loads acting on cartilage can cause degenerative changes inside the tissue, whose internal structure hardly regenerates due...
This contribution discusses the numerical analysis of timber structures by means of the Finite Elements Method. As a naturally grown and fibrous material, wood shows distinctive material directions, which are captured by a cylindrically anisotropic model. Due to the growth conditions of a tree, the fiber course in wooden structural parts can differ. Especially branches, leading to knots, affect the...
The concept of adaptive error control for finite element Galerkin discretizations has more recently been extended from the pure treatment of the discretization errors [1], [2] also to the control of modelling errors [4], [5]. These techniques can be employed for a rigorous justification of the local choice of the model out of a given hierarchy with increasing complexity. In the present paper the concept...
Analytical criteria for risk assessment of ships in random seas are important for the development of new intact stability criteria and also for the first design stage, where many ship designs have to be compared. The analysis is performed by Stochastic Averaging. The results are compared to those obtained by Monte Carlo simulations. We use extended wave modeling by means of two independent stochastic...
We consider robust parameter estimation problems in which either the l1 norm or the Huber function of a measurement error vector used as cost functionals. In order to avoid high computational effort of computing exact derivatives needed for the solution of these problems with the Gauss‐Newton method, we suggest to use approximations of the derivatives in the occurring linearized subproblems. We show...
The linearized theory of water waves is used to examine the diffraction of incident regular waves by a slotted dual cylindrical caisson breakwater. The breakwater consists of a vertically slotted outer cylinder circumscribing an impermeable inner cylinder. Under the assumption that the wavelength is much greater than its thickness, each panel is replaced by a thin structure and the permeability is...
The flow through a double channel membrane pump is modeled by a time dependent potential flow. The total forces on the fluid are determined as a function of the position of the lateral pistons. It turns out that the total force and thus the pressure gain is very sensitive to the position of the excitation. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Freak or rogue waves on the ocean seemingly appear from nowhere, cause severe damage to ships and offshore structures due to their large crest heights, and disappear at once. Since the Draupner wave measured on New Year's day 1995 finally confirmed the existence of freak waves, different models were developed to describe them. One deterministic model to investigate their occurrence is the nonlinear...
In the Ekman‐Couette‐System, where the usual Couette‐System is additionally rotated about its normal axis, localized single roll solutions have been known for some time. By varying different system parameters, a new localized solution emerging by saddle‐node bifurcations from these known solutions has now been found. This new solution is of the same localized nature like the old solution but with...
We present a novel approach to treat fluid‐structure interactions in a closed variational setting. The standard model is the so‐called ‘arbitrary Lagrangian‐Eulerian’ (ALE) framework. Here, the fluid is transformed into an artificial coordinate system, which fits with the Lagrangian structure system. In the fully Eulerian framework, which is the reverse to ALE, the fluid is left in its natural coordinates...
Due to the growing interest in determining the macroscopic material response of inhomogeneous materials, computational methods are becoming increasingly concerned with the application of homogenization techniques. In this work, two‐scale classical (first‐order) homogenization of electro‐mechanically coupled problems using a FE2‐approach is discussed. We explicitly formulated the homogenized coefficients...
In der Mikroelektronik spielen die Gruppe der Lotwerkstoffe eine wichtige Rolle. Sie stellen zwischen einzelnen Komponenten, wie beispielsweise Chip und Platine, nicht nur die elektronische, sondern auch die mechanische Verbindung her. Ihre Stabilität ist deshalb zur Lebensdauervorhersage mikroelektronischer Bauteile von besonderer Bedeutung. Die unterschiedlichen verwendeten Legierungen weisen dabei...
The effect of polyvinyl chloride (PVC) foam filler on elastic properties of a regular hexagonal aluminum honeycomb core is studied. The unit cell strain energy homogenization approach based on the finite element method (FEM) within ABAQUS code is applied for prediction of effective material constants of the foam‐filled honeycomb core. The developed FE model is then used to observe a three‐dimensional...
In this work, a non‐conforming three‐dimensional finite element coupled with direct methods and homogenization technique is presented for the limit analysis of periodic metal‐matrix composites. Using this element, which is constructed from bilinear shape functions and enriched by internal second‐order polynomials, limit analysis of composite material can be efficiently carried out. Accuracy and overall...
This paper is about the numerical implementation of a known, but advanced model with a projected Newton algorithm and a residual including only two vectors of unknowns. In a complex stress driven example the superelastic behavior is investigated. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Flexible channels conveying fluid may loose stability by divergence or flutter, thus leading to undesirable dynamic behaviour. A lot of investigations have already been done on this subject, each involving structural models expressing a specific type of stiffness. The aim of this contribution is to investigate and compare systematically the influence of various types of structural stiffness on the...
Filler‐reinforced rubber‐like materials demonstrate deformation induced softening, known as the Mullins effect. This softening can be reversible in a certain range (healing).
The previously introduced concept of network evolution (NE) explains the Mullins effect as the result of a filler‐polymer network rearrangement [1]. It is assumed that debonding of polymer chain segments from rigid aggregates...