bluuebunny/crossref_metadata_2025 huggingface dataset:
A fully variational algorithmic formulation for wrinkling at finite strains
Authors: Mosler J.
Published: February 2009

This contribution is concerned with an efficient novel algorithmic formulation for wrinkling at finite strains. In contrast to previously published numerical implementations, the advocated method is fully variational. More precisely, the parameters describing wrinkles or slacks, together with the unknown deformation mapping, are computed jointly by minimizing the potential energy of the considered mechanical system. Furthermore, the wrinkling criteria are naturally included within the presented variational framework. The presented approach allows to employ three–dimensional constitutive models directly, i.e., plane stress conditions characterizing membranes are variationally enforced by minimizing the potential energy with respect to the transversal strains. Since the proposed formulation for wrinkling in membranes is fully variational, it can be conveniently combined with other variational methods (based on energy minimization). As an example, a variationally consistent framework for finite strain plasticity theory is considered. More precisely, the minimization principle characterizing wrinkling in elastic membranes and that describing plasticity in inelastic solids are coupled leading to a novel variational approach for inelastic membranes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale modelling and structural characterization of Fe enriched Al alloy
Authors: Parashkevova Ludmila , Bontcheva Nikolina
Published: February 2009

Scale dependent modelling of inelastic behaviour of rapidly solidified Al Fe enriched powders subjected to cold compaction and subsequent hot extrusion is provided. The alloy is considered as a ductile “in situ” composite. The average elastic end plastic properties of bulk material depend on density evolution, temperature and matrix hardening. The model assumptions are based on microstructural observations. The microstructure characterization was carried out using Scanning Electro Microscopy (SEM) and Energy Dispersive X–ray (EDX) analysis. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asymmetric effects of polymers in finite thermoviscoplasticity
Authors: Shaban Ahmed , Mahnken Rolf
Published: February 2009

Glassy polymers such as polycarbonate exhibit different behaviours in different loading scenarios, such as tension and compression. For the simulation of these asymmetric effects we present a framework for thermoviscoplastic modelling of polymers at large strains. To this end a flow rule is postulated within a thermodynamic consistent framework in a mixed variant formulation which is decomposed into a sum of weighted stress mode related quantities. The different stress modes are chosen such that they are accessible to individual examination in the laboratory, where tension and compression are typical examples. The characterisation of the stress modes is obtained in the octahedral plane of the deviatoric stress space in terms of the Lode angle, such that stress mode dependent scalar weighting functions can be constructed. Furthermore the numerical implementation of the resulting set of constitutive equations is used in the finite element program ABAQUS to simulate the laser transmission welding process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Frequency characteristics of flexibly vibration discrete‐continuous mechatronic system
Authors: Buchacz A.
Published: February 2009

The purpose of this paper is formulating of problem of flexibly vibrating mechatronic system. The main approach of the subject was to formulate the problem in the form of set of differential equation of motion and state equation of considered mechatronic model of object. The considered flexibly vibrating mechanical system is a continuous beam, clamped at one of its end. Integral part of mechatronic system is a transducer, extorted by harmonic voltage. In the paper the linear mechanical subsystem and linear electric subsystem of mechatronic system has been considered. The methods of analysis and obtained results can be base on design and investigation for this type of mechatronic systems. The mechatronic system formed from mechanical and electric subsystems with electromechanical bondage has been considered. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lp‐Lq time decay estimate to the solution of the Cauchy problem of the system of equations for nonlocal model of hyperbolic thermoelasticity theory
Authors: Gawinecki Jerzy , Lazuka Jaroslaw , Rafa Jozef
Published: February 2009

The aim of this paper is to present a new system of equations describing nonlocal model of hyperbolic thermoelasticity theory. We used the Papkin and Gurtin approach based on the constitutive relations for internal energy e(x), and heat flux q(x), with integral terms. Such system of equations describes the propagation of thermal perturbation with finite velocity. Using the modified Cagniard–de Hoop's method we constructed the matrix of fundamental solutions for this system of equations in three–dimensional space. Basing on the constructed matrix of fundamental solutions in the explicit formula we represent the solution of the Cauchy problem to this system of equations in the form of some kind of convolutions. Next, applying the method of Sobolev spaces, we obtain the Lp−Lq time decay estimate to the solution of the Cauchy problem. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling of macroscopical transient frost processes and microscopical driving forces
Authors: Kruschwitz Jens , Setzer Max J.
Published: February 2009

The artificial saturation phenomenon due to freeze–thaw cycles is described by a multi–phase and multiscale model [1,2,3] formulated within the Theory of Porous Media, [4]. It represents partially saturated concrete as a mixture of 5 interacting constituents φα, namely the solid skeleton φs, the bulk water φl, the pore volume occupied by vapour φv, the ice φi and the gel water phase φp. Most relevant for the model is the distinction between two length scales and their characteristic time scales. The boundary is marked where macroscopic bulk conditions change to surface physics and chemistry. Surface physics and chemistry acting on the nano–scale affect fundamental properties of concrete and consequently the durability of concrete against freeze–thaw.

At the macroscopic scale the model describes transient conditions (i.e. water–uptake, heat transport, volume dilatation of 9%, phase change of first order considering hysteresis) which are characterized by a relatively long time period to reach equilibrium in contrast to the processes modelled on the microstructure. At the microscopic scale the model represents the nanoscopic CSH–gel system consisting of solid CSH and water as a linked system of both components basing on the concept of the “Solid–Liquid Gel System” [5]. In the constribution the numerical results of the model are presented with focus on the evaluation of the process zone during the penetration of the melting front into the matrix. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Error estimates for mixed finite element discretization of the Richards equation
Authors: Radu Florin A.
Published: February 2009

We present a numerical scheme based on the mixed finite element method (MFEM) for the Richards equation, a nonlinear, degenerate parabolic equation. Due to the degeneracy, the solution of the equation has low regularity and therefore only lower order finite elements are recommended. We review the main posibilities for proving the convergence of the scheme. Especially for the case without using the Kirchhoff transformation a new result is given. We also briefly discuss how to solve the nonlinear fully discrete problems appearing at each time step and refer to papers where the convergence of these methods is rigurously studied. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of powder metallurgical coating by radial axial ring rolling
Authors: Frischkorn J. , Reese S.
Published: February 2009

The process integrated powder coating by radial axial rolling of rings is expected to provide a new hybrid production technique to apply different kinds of powder metallurgical functional surfaces to ring–shaped work pieces. The main advantages compared with conventional manufacturing processes in this field can be found in lower costs, shorter process cycles and larger producible work pieces. In order to meet the requirements for an industrial application of this new process it is important to proof its capability particularly with regard to reproducibility and to investigate its boundaries. A reliable process simulation will provide a deeper insight into the governing parameters and reduce the money and time consuming experimental tests. Considering a numerical simulation using the FE method two challenges can be named. First one requires a material model to describe the compaction of metal powder at different elevated temperatures. As second the simulation of the ring rolling process itself is still very time consuming. A fine spatial discretization due to large deformations in the rolling gap and contact interaction between workpiece and rollers are the most prevailing factors in this context. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interpretation of parameters in phase field models for ferroelectrics
Authors: Schrade D. , Müller R. , Gross D.
Published: February 2009

Ferroelectric ceramics have a complex micro–structure which is responsible for their non–linear behavior on the macroscopic scale. The presented model treats the spontaneous polarization as an order parameter, for which a Ginzburg–Landau type evolution is postulated. Contrary to sharp interface models this allows for the simulation of evolving domain structures. The equations are solved via the Finite Element Method, employing an implicit time integration scheme. Numerical simulations show the physical interpretability of the phase field parameters. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pyramidal indentation into fcc single crystals and quasi‐isotropic polycrystals: similar phenomena, different driving mechanisms
Authors: Eidel Bernhard , Schürg Marco
Published: February 2009

Pyramidal microindentation into the (001) surface of an fcc single crystal made of the Ni–base superalloy CMSX‐4 has shown indent shapes which strongly depend on the azimuthal orientation of the pyramid. This observation is experimentally elucidated by digital surface models obtained from high resolution electron back–scatter diffraction (EBSD) technique along with digital image processing. Predictions of crystal plasticity finite element simulations agree with the experimental observations; the observed surface deformation patterns are due to pile–up formation, which is invariantly maximum in <110> directions thus being independent of the azimuthal orientation of the pyramid. The material pile–up is locally accommodated to the indenter faces leading to a convex, a concave contact rim at the faces of the indenter depending on the orientation. The result of maximum pile–up in <110> directions suggests that the driving mechanism for pile–up is purely crystallographic in that the influence of stress concentrations due to different indenter orientations and indenter shapes is negligible. The present findings for fcc single crystals are contrasted to well known observations for quasi–isotropic polycrystals. The different driving mechanisms resulting in phenomenologically similar material response are identified for both materials. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase‐field‐based modeling and simulation of solidification and deformation behavior of technological alloys
Authors: Gladkov Svyatoslav , Stiemer Marcus , Svendsen Bob
Published: February 2009

The purpose of this work is the formulation and application of a continuum field approach to the phenomenological modeling of the behavior of technological alloys undergoing phase transitions and attendant inelastic deformation. To describe the phase transition, a phase–field approach is utilized. For the fully coupled system, an algorithmic formulation is derived based on efficient finite element techniques. Applications will be discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Multi‐Scale Analysis of Textile Reinforced Concrete Structures
Authors: Lepenies Ingolf G. , Richter Mike , Zastrau Bernd W.
Published: February 2009

Textile reinforced concrete (TRC) is a composite of rovings (multi filament yarns) and fine grained concrete which is used in civil engineering to fabricate new structural elements and to strengthen existing constructions. The proposed multi–scale approach is based on a hierarchical material description on the micro, the meso and the macro scale. The paper deals with structural models of the macro scale, using the detailed information of the micro– and the mesoscopic models to simulate the behavior of typical structural members made of reinforced concrete. Due to the textile reinforcement in TRC the crack opening displacements are very small. This leads to the major influence of the post cracking behavior of concrete on the overall response of the structural member. In the case of a steel and textile reinforced concrete plate the simulated crack width of the meso model is used to capture this effect within the framework of a multi–scale analysis. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Sachs bound in stress‐induced phase transformations in polycrystalline scalar shape‐memory alloys
Authors: Schlömerkemper Anja , Bhattacharya Kaushik
Published: February 2009

We consider stress–induced transformations of polycrystalline shape–memory alloys which are so–called scalar materials. In this case the Sachs bound on the phase transformation yield stress turns out to be sharp. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Approaches to Model Nanotube‐Reinforced Polymers using Micromechanics and Finite Elements
Authors: Schmidt Ina
Published: February 2009

In this work, the applicability of new analytical methods for modeling polymer nanocomposites is examined. The influence of an interphase between nanotube and matrix could be captured by this modeling strategy. However, it is shown that there are some difficulties in calculation of composites including extremely weak fibers with stiff coatings. Furthermore, finite element calculations are shown for comparison. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale Coupling through Locally Enriched Finite Elements
Authors: Shan Wenzhe , Nackenhorst Udo
Published: February 2009

Multiscale modeling helps us to focus our limited computational power into those special places where traditional models based on continuum mechanics will fail while not losing the big picture of the macro scale behavior. An hourglass shaped development can be observed in today's simulation technologies. Simulation tools in the macroscale category and that for the micro phenomenons are both relatively well developed. Many algorithms and methods have been proposed in recent years to fill the gap between them. However, rather than trying to bridging different techniques, many tend to replace them completely and become independent simulation tools. Since many single–scale models have already been widely adopted by both the industry and the academy, it would be more beneficial to concentrate just on coupling techniques which can be applied without significant modifications of the original simulation framework. In this work, we present a multiscale idea of coupling the fine–scale model with the coarse–scale model through local enrichment within the elements at the coupling boundary. Higher order shape functions have been used to ‘enrich’ the coarse–scale model, allowing softer transition of the displacement field from the fine–scale model to the coarse–scale model. A least–square process has been used to fit the displacement gradients of different models at the coupling region. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Computation of the Macroscopic Tangent for Multiscale Volumetric Homogenization Problems
Authors: Temizer İlker , Wriggers Peter
Published: February 2009

For the computation of the macroscopic tangent that is required in multiscale volumetric homogenization techniques, two methods are summarized. First, a condensation approach is followed where the linearity of variational terms associated with the penalty enforcement of boundary conditions is explored in order to extract a macroscopic tangent at any stage of the Newton–Raphson iterations of a microstructural testing procedure. As an alternative approach, a second method is explored that requires only the knowledge of infinitesimally close macroscopic deformation states. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A study of effects of wall‐normal rotation on the turbulent channel flow
Authors: Mehdizadeh A. , Oberlack M.
Published: February 2009

The effects of the wall–normal rotation on the turbulence channel flow have been studied. A series of direct numerical simulations have been performed with various rotation rates for Reynolds number 180 based on the friction velocity in the non–rotating case. All remarkable changes are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental in‐situ investigations on fluid flow during High Pressure Processing by means of LDA and HWA
Authors: Song K. , Rauh C. , A.
Published: February 2009

In a tube injection system for High Pressure Processing (HPP) of foods and biomaterials, pressure transmitting medium is injected into the vessel to increase the pressure up to 1000 MPa generating a submerged liquid jet. The presence of a turbulent free jet during pressurizing and its positive influence on the homogeneity of the product treatment have already been examined by computational fluid dynamics investigations. However, up to now there is no experimental evidence, supporting the existence and properties of turbulence of a free jet during HPP due to difficulties in gaining in–situ insight into the high pressure vessel and the lack of high pressure withstanding probes. Hence, we developed two experimental setups: (1) HP–Laser Doppler Anemometry (HP–LDA), and (2) HP–Hot Wire Anemometry (HP–HWA). This paper presents first results of velocity profiles measured by LDA and HWA under high pressure conditions up to 300 MPa. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of the effect of the wall roughness and free stream turbulence on the boundary layer development
Authors: Jonáš P. , Mazur O. , Uruba V.
Published: February 2009

Development of a flat plate boundary layer (grad P = 0) was investigated in the closed type wind tunnel (0.5 × 0.9 × 2.7 m3). The plate was either aerodynamically smooth or covered with a thin plate (10 mm thick) with the surface made from the sand paper (grits 80). FST is generated by square mesh plane grids/screens set across the flow as to produce homogeneous, close to isotropy turbulence with various scales of velocity and length. The surface roughness was of transient type. The comparison is made of the effect of various grouping of the wall roughness and FST on the boundary layer development. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Modified Statistical Interparticle Collision Model For Colliding Particle Clouds
Authors: Kloss C. , Pirker S.
Published: February 2009

In this paper, a modified stochastical interparticle collision model is discussed and valdiated. A channel flow with a constriction serves as a test case. The simulation of the thereby colliding particle strands clearly shows that without the collision sub–model, the simulation with the standard Lagrangian model yields unreasonable results. After adding the stochastical collision sub–model, the Lagrangian model is able to describe the flow situation if the mass load is not too high. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The relationship between the vortical structure and the wall shear stress in a blind trough cavity subject to a jet impingement
Authors: Knob M. , Uruba V.
Published: February 2009

In a blind trough cavity subject to a jet– impingement, the jet switching phenomenon has been known for decades. The large vortices, formed by the Kelvin– Helmholtz instability play a crucial role in this phenomenon– they are the main cause of the fluid entrainment phenomenon, which consequently evoke the Coanda effect and finally results in the jet switch. As the jet swings, the vortical structure inside the cavity changes together with the impinigement point. The aim of this article is to describe the relationship between the wall shear stress, i.e. the motion of the impingement point, and the vortical structure.The analysed data were obtained using the TR PIV system, the caity aspect ratios 16:24 and 18:24, jet hydraulic diameter based Reynolds numbers 3000, 11200 and 19600, and the impingement angles 0°, 5°, 10° and 15°. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling of heat transfer and fluid flow in laser welding
Authors: Kotalík Pavel , Boeck Thomas
Published: February 2009

Axisymmetric 2D heat transfer including solid–liquid phase transitions coupled with surface tension driven flow of molten metals is studied numerically for pulsed laser welding. We show that the pulse modulation in time influences the temperature, melting front and flow velocity which, together with the expected undercooling, may explain the fine–grain structure of the resolidified welds that have better strength and, possibly, no cracks inside. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Solution of Newtonian and Non‐Newtonian Flows in Bypass
Authors: Prokop V. , Kozel K.
Published: February 2009

This paper deals with a numerical solution of laminar incompressible steady flows of Newtonian and non–Newtonian fluids through bypass of a restricted vessel. Blood flow is considered to be Newtonian in the case of vessels of large diameters as aorta. On the other hand, with decreasing diameter of a vessel the non–Newtonian behavior of blood can play a significant role. One could describe these problems using Navier–Stokes equations and continuity equation as a model. In the case of Newtonian fluids one considers constant viscosity compared to non–Newtonian fluids where viscosity varies and can depend on the tensor of deformation. In order to find numerical solution, the system of equations is completed using an artificial compressibility method. The space derivatives are discretised using a cell centered finite volume method and arising system of ordinary differential equations is solved using an explicit multistage Runge–Kutta method with given steady boundary conditions. The steady solution is achieved for time t→∞ and steady boundary conditions. The results can be used in the field of cardiovascular research. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Up‐scaled Dynamical Model of the Human Vocal Folds
Authors: Triep Michael , Klostermann Jens , Schwarze Rüdiger , Brücker Christoph
Published: February 2009

Flow and volume flow measurements are carried out through a driven 3:1 up–scaled glottis model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Propagation of Sound Waves in Partially Saturated Soils
Authors: Albers Bettina
Published: February 2009

We investigate the propagation of sound waves by means of a newly constructed model in a sandstone filled with two immiscible fluids. The speeds and attenuations of the four emerging waves (one transversal, three longitudinal) are illustrated in dependence on frequency and initial saturation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Diffraction of water waves by a slotted cylindrical breakwater
Authors: Basmat A.
Published: February 2009

Permeable and slotted breakwaters are becoming more popular, in order to reduce the drawback of rigid coastal structures: namely large reflections, forces and overtopping. The linearized theory of water waves is used to examine the diffraction of incident regular waves by a vertically slotted cylindrical breakwater that consists of a number of distinct rigid cylindrical panels. Under the assumption that the wavelength is much greater than the thickness, each segment is replaced by a thin structure and the permeability is modelled by suitable boundary conditions. The first condition is the matching pressure and normal velocity conditions between two internal and external fluid regions and the second condition is zero normal velocity on rigid panels. The mixed boundary–value problem is transformed to dual series relations and the least–square method is applied to get the forces on the structure. The results are presented to illustrate the effects of permeability. Numerical results compare well with McCamy and Fuchs predictions for the limiting case of an impermeable rigid cylinder. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Trapped‐mode and gap‐band effects in elastic waveguides with obstacles
Authors: Glushkova Natalia , Glushkov Evgeny , Golub Mikhail , Boström Anders
Published: February 2009

Traveling wave propagation in elastic waveguides with obstacles in the form of cracks, voids, inclusions or surface irregularities is considered. The investigation is focused on the trapped–mode phenomena featured by the time–averaged harmonic wave energy localization near the obstacles in the form of energy vortices. The latter results, in particular, in narrow gap bands in the frequency plots of transmission coefficients. The study is carried out using analytically based computer models relying on wave expressions in terms of path Fourier integrals, Green's matrices for the laminate structures, and asymptotics for body and traveling waves derived from those integrals. The connection between the resonance effects and natural frequencies (spectral points of the related boundary value problems) in the complex frequency plane is analyzed as well. Examples of spectral points touching the real axis in the course of varying crack size are presented. The eigenforms associated with such discrete spectral points lying in a continuous spectrum depict strong wave energy localization. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Damage detection in plates by wave propagation analyses
Authors: Meyfarth Daniel , von Ende Sven , Lammering Rolf
Published: February 2009

At locations with defects the propagation of elastic waves in solids is disturbed. This behaviour can be used for the development of new structural health monitoring and quality assurance systems. In the sense of adaptive structure systems actuators of piezo–electric materials [1] are implemented to generate high frequency waves (Lamb waves) in plate like structures, [2]. At flaws, imperfections of the structure and surface defects these waves show reflections, refractions and mode conversions. The observation of the wave propagation and the wave behaviour at possible flaws and surface defects is performed by an optical measurement system. Measurement data of the thin walled metallic plates are compared with numerical and analytical solutions. First results of the detection of the wave propagation in metallic plates are presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impedance eduction from energy dissipation measurements with flow
Authors: Richter Christoph , Thiele Frank , Busse Stefan , Heuwinkel Claus , Röhle Ingo , Enghardt Lars , Michel Ulf
Published: February 2009

An optimization method for the calculation of the wall impedance of a perforate from measurements under grazing flow conditions is presented. It is in particular characterized by the simultaneous eduction of the parameter set defining the impedance as function of frequency, which allows interpolation and extrapolation. The Extended Helmholtz Resonator is applied as impedance model and the simultaneous eduction is performed using a time–domain CAA method. Furthermore, the method uses processed energy data from experiments to define the objective function. The results give an insight in the effect of bias flow on the wall impedance under grazing flow conditions. It proves to be an important acoustic design parameter. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of Wave Propagation in Complex Structures with the Spectral Element Method
Authors: Schulte R. T. , Fritzen C.‐P.
Published: February 2009

In nondestructive testing, the use of ultrasonic elastic waves has proven as one of the most successful principles to detect structural damage like cracks, delaminations etc. Especially, Structural Health Monitoring (SHM) is characterized by permanently installed embedded or surface–mounted actuators and sensors (e.g. piezoelectric patches). The capability of most approaches strongly depends on adequate choice of parameters like excitation signals and actuator/sensor positions. For this reason there is a growing interest in efficient and accurate simulation tools to shorten time and cost of the necessary pretests. With respect to high frequency excitation a computationally efficient method is required. This contribution presents the theoretical background of the spectral element method including the electro–mechanical coupling of piezo elements. The spectral element method generates a diagonal mass matrix leading to significant savings of memory and to a crucial reduction of complexity of the time integration algorithm. Both in–plane and out–of–plane waves can be handled. Numerical examples for the propagation of waves in stiffened structures are presented. The effect of improper placement of actuators/sensors is shown. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inverse acoustic problems: theory and numerical methods
Authors: Kabanikhin Sergey , Shishlenin Maxim
Published: February 2009

We study the inverse problem for the acoustic equation. The several numerical methods are considered and investigated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vertical Vibrations of a Vehicle Excited by Real Road Profiles.
Authors: Borowiec Marek , Litak Grzegorz , Hunicz Jacek , Koszałka Grzegorz , Niewczas Andrzej
Published: February 2009

We analyze experimental acceleration data obtained from the delivery car vibration test in working conditions. The vertical components of unsprung and sprung mass accelerations have been analyzed by using the Fourier analysis. In particular we examine the response of the sprung mass on various road excitations and conclude the efficiency of the car suspension. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of flows over inclined wavy bottoms
Authors: Häcker Tobias , Uecker Hannes
Published: February 2009

We study the flow of an incompressible liquid film down a wavy incline. Starting from the Navier–Stokes equations we derive an integral boundary layer equation (IBLe) by applying a Galerkin method with a single test and ansatz function. In comparison with older models this approach has several advantages. First, a linear stability analysis for stationary solutions yields a critical Reynolds number which corresponds in the limit of a flat incline with results directly obtained by the Navier–Stokes equations. Second, the IBLe is consistent with the pertinent Benney equation. Finally, the velocity profile is not assumed to be parabolic, so that also parameter regimes with recirculations can be modelled. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The sensitivity analysis of the drawpiece response on the finite element shape parameter
Authors: Kaldunski Pawel , Kukielka Leon
Published: February 2009

On this paper the numerical analysis of the drawing process is presented. The sensitivity analysis of the drawpiece response on the finite element shape parameter is realized. The sensitivity of stresses field on the edge and the round edge of drawpiece on the change sizes of the finite elements is defined. Precisely proportion between height and length of the finite element is examined. The analysis with the explicit method in the ANSYS LS–Dyna system is passed. The die and the stamp as not deformable bodies are accepted and with the shell finite elements are discretized. The drawpiece with the solid finite elements are discretized. Examples results of computer simulations are presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analytical Solution for the Deformation of a Cylinder under Tidal Gravitational Forces
Authors: Scheithauer Silvia , Lämmerzahl Claus
Published: February 2009

Quite a few future high precision space missions for testing Special and General Relativity will use optical resonators which are used for laser frequency stabilisation. These devices are used for carrying out tests of the isotropy of light and of the universality of the gravitational redshift. As the resonator frequency not only depends on the speed of light but also on the resonator length, the quality of these measurements is very sensitive to elastic deformations of the optical resonator itself. As a consequence, a detailed knowledge about the deformations of the cavity is necessary.

In this note we derive for the first time an analytical solution for the problem of an elastic, isotropic, homogeneous free–flying cylinder in space under the influence of a tidal gravitational force. A detailed derivation can be found in [4]. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homogenization for contact problems with friction on rough interface
Authors: Orlik Julia , Nam Alexander
Published: February 2009

We consider a contact problem between a macroscopic solid with a smooth boundary and a technical textile, while the textile has a periodic microscopic structure and microscopically rough surface. Two–scale homogenization approach is applied to the problem. The microscopic solution is approximated in terms of macroscopic solution and some concentration factor, given as a solution of auxiliary boundary value or contact problems of elasticity on the periodicity cell. Local friction condition is represented as a continuous non–linear functional over the stress field. Two–scale convergence is used to prove the convergence of friction functional. The macroscopic initial frictional limit is found. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale analysis and reconstruction of time series of stochastic cascade processes
Authors: Nawroth Andreas , Wächter Matthias , Peinke Joachim
Published: February 2009

We propose a new method to generate synthetical time series of hierarchical stochastic processes. Based on the statistics of n–scale joint PDFs, the stochastic properties of a time series are modeled simultaneously on many scales. The application to a data set of turbulent velocities is demonstrated, showing the ability of the approach to reproduce the correct statistics of the original time series on all considered scales. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimization of the dynamic blanking process
Authors: Bohdal Lukasz , Kukielka Leon
Published: February 2009

In this paper an optimization of the dynamic blanking process with using E–PLANNER, ANSYS and MATLAB programmes was presented. The main aim of this work was to obtain the high quality of the cut surface in function of: the size of clearance between punch and die, value of fillet radius of the punch edge and the speed of blanking. Numerical analysis were conducted in Ansys LS–Dyna programme, with use of the explicit method and the experiment plan had been done before. Five levels rotary plan, was used. Unknown coefficients in mathematical model in the shape of quadratic equation with interactions were obtained. Obtained regression function was optimized in MATLAB programme, and determined optimal value of the process parameters. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On bounds for ratios of posterior expectations under asymmetric loss functions
Authors: Preda Vasile , Ciumara Roxana
Published: February 2009

We compute the bounds of the Bayesian premium when the prior distribution belongs to the ε‐contaminated class of priors and the loss function is weighted asymmetric Linex, by applying a result of Gomenz–Deniz et al [1]. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Genetic Algorithm Optimization of a Six Degree of Freedom Micro Parallel Robot
Authors: Stan S.‐D. , Mătieş V. , Bălan R.
Published: February 2009

In this paper a mono–objective optimum design procedure for a six–degree of freedom parallel micro robot is outlined by using optimality criterion of workspace and numerical aspects. A mono–objective optimization problem is formulated by referring to a basic performance of parallel robots. Additional objective functions can be used to extend the proposed design procedure to more general but specific design problems. A kinematic optimization was performed to maximize the workspace of the mini parallel robot. Optimization was performed using Genetic Algorithms. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Solving regularized total least squares problems via a sequence of eigenvalue problems
Authors: Lampe Jörg , Voss Heinrich
Published: February 2009

A computational approach for solving regularized total least squares problems via a sequence of eigenvalue problems has recently been introduced by Renaut and Guo. Combining this approach with thick starts using the nonlinear Arnoldi method lead to a very efficient method for large RTLS problems. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On a matrix associated to a matrix pair
Authors: Virnik Elena
Published: February 2009

For a c–stable matrix pair (E,A), i.e., all finite eigenvalues of (E,A) have negative real part, an associated c–stable matrix is provided. It has all finite eigenvalues of (E,A) as eigenvalues and an additional stable eigenvalue −α, where α may be chosen arbitrarily, which corresponds to the eigenvalue ∞ of (E,A). In the case of positive systems, this associated c–stable matrix is, in addition, shown to be a −M‐matrix. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
How residual bounds for restarted GMRES describe the real behaviour
Authors: Zítko Jan
Published: February 2009

Given a system of linear equations Ax=b with a nonsingular matrix A, new bounds for the norm of the residual vector are presented and shown by example. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Anisotropic mean curvature flow in higher codimension
Authors: Pozzi Paola
Published: February 2009

We present recent progress in the study of the anisotropic mean curvature flow in higher codimension. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Studies on molten bath and aluminium contamination with ceramic anodes corrosion products
Authors: Rodean Cristian Paul , Rodean Simona
Published: February 2009

Two types of tin oxide ceramic anodes with 3 different bulk densities are prepared and tested in a laboratory aluminium reduction cell. During normal electrolysis, the regular chemical dissolution process of anode material should be controlled by mass–transport and subsequent reduction of the corrosion products into the cathode metal. The content of Sn species from each experimental anode in the electrolyte reaches stable values and does not contribute to the time dependent corrosion. Their concentration in metal becomes linear with time, providing that the concentration in the electrolyte remains constant. The mass transport anode dissolution mechanism is experimentally confirmed and it becomes evident that the dissolution rate is largely dependent by the conditions at the cathode, which has a hundred times lower rate factor. The smallest aluminium contamination (under 0.2 wt %) and corrosion rate (under 1 cm/year) were obtained by testing the tin oxide anode, with Recipe 2 (2) – 96% SnO2+2%Sb2O3+2%CuO by our own sintering procedure and with bulk densities bigger than 6.5 g⋅cm−3 prepared. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the direct numerical methods for systems of integral equations with nonlinear delays
Authors: Tynda Alexander N.
Published: February 2009

In this paper we investigate the possibility of a construction of direct numerical methods for systems of nonlinear Volterra–type integral equations. One of the unknown functions of such systems is in the limit of integration. Two numerical schemes based on the piecewise constant and piecewise linear approximation of the exact solutions are suggested. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal Control of an Axisymmetric Conical Shell with a Unilateral Elastic Foundation and Rigid Supports
Authors: Bock Igor , Lovíšek Ján
Published: February 2009

We study an optimal control problem for an elastic conical shell. The displacement vector u=(u,v) is then a function of one variable s∈(a,b), 0<a<b<∞. Here u is the meridional and v the normal displacement. The shell is assumed to be simply supported. Moreover, we consider several unilateral obstacles and an unilateral elastic foundation of Winkler type i.e. the reaction force is proportional of the positive part of the normal displacement. The state problem is formulated in a form of variational inequality for u. The design parameter e=(t,z,F) includes the variable thickness of the shell, the stiffness characteristics of the foundation and the friction coefficient. The existence of the optimal control will be explained. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Active Vibration Damping and Model‐Based Control for an Adaptronic Actuator
Authors: Ast Alexandra , Eberhard Peter
Published: February 2009

The static and dynamic flexibility of a machine tool is often the major limiting factor for the machining quality, especially if high processing speeds as well as high accuracies are desired. Particularly parallel kinematic machines, which have been developed for high processing speeds and accuracy and which often use lightweight structures, can suffer from severe problems with vibrations of system components and the loss of accuracy due to deformations of machine parts. Introducing so–called adaptronic or smart components into the machine tool structure opens up new and interesting possibilities to actively control the deformations and vibrations of flexible machine parts. They allow to specifically target such undesired properties and to significantly reduce or even eliminate their influence on the system performance. Concepts of active vibration damping and model–based control are presented here for such an adaptronic actuator implemented in a machine tool with parallel kinematics. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Controlling chaotic discrete dynamical systems through fixed point iterative methods
Authors: Berinde Vasile , Pačurar Mădălina
Published: February 2009

A simple and natural technique for controlling chaos in discrete dynamical systems, originating in iterative approximation of fixed points, is developed. We show by numerical simulations that our technique of stabilizing unstable periodic points of chaotic discrete systems is effective and, moreover, compared to other stabilizing methods, has a extremely high speed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Approximation of Uncertain Nonlinear Systems
Authors: Gaull Andreas , Kreuzer Edwin
Published: February 2009

We address qualitative characteristics of dynamical systems and their approximation using set–valued numerical methods, where we aim at robust results. In this spirit, model uncertainties are incorporated into the problem formulation as outcomes of an external stochastic process. The systems under consideration are described in terms of finite state Markov chains. An example serves to illustrate the procedure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The application of robust control for vibration damping of working machines seat suspensions
Authors: Maciejewski Igor
Published: February 2009

The object of simulation is the seat with a visco–elastic active suspension, with improved vibro–isolation properties using the robust control. Based on the verified passive seat suspension model, the robust control possibilities in order to help the working machines operators against vibration is considered. As the viobro–isolation criteria, the seat effective amplitude transmissibility factor (SEAT) and maximum relative displacement between the working machine's cabin floor and the seat is chosen and evaluated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adaptive disturbance transmission decoupling in active vehicle suspensions
Authors: Readman Mark , Corless Martin , Villegas Carlos , Shorten Robert
Published: February 2009

With active vehicle suspension, one can tailor a vehicles response to load and inertial without affecting the vehicle response to road disturbances. This decoupling is achieved in [1] and [2] using a filtered combination of measured signals. These filters require exact knowledge of certain vehicle parameters including vehicle mass to achieve the desired decoupling. Here we propose a parameter adaptive version of these filters which does not require knowledge of vehicle parameters. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prooving Identities with Computer‐Algebra ‐‐ Example: Algebraic Time‐Derivative Estimation
Authors: Reger Johann , Jouffroy Jérôme
Published: February 2009

For the case of continuous–time systems, this note contributes a detailed proof relating the so–called algebraic approach to time–derivative estimation, as proposed by Fliess and co–workers, to classical results from linear estimation theory. The proof is based on a modern computer–algebra proof technique that, in the main, resorts to the celebrated algorithm by Wilf and Zeilberger in the multisum case. As a result of the proof, the algebraic approach to time–derivative estimation is traced back, equivalently, to state estimation using the reconstructibility Gramian of the dynamic system, here, with respect to a particular nilpotent time–invariant input–free linear system. Additionally, the close relationship of the algebraic approach with least–squares time–derivative estimation is pointed out. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Remark on Finite‐Time Hyperbolicity
Authors: Berger A. , Doan T. S. , Siegmund S.
Published: February 2009

We discuss two notions of hyperbolicity for finite–time linear differential equations. The first notion (D–hyperbolicity) is based on the dynamic (or EPH) partition, the second (M–hyperbolicity) is motivated by exponential dichotomies. We study conditions under which D–hyperbolicity implies M–hyperbolicity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Switching Stability of Automotive Roll Dynamics Subject to Interval Uncertainty
Authors: Solmaz Selim , Shorten Robert , Mason Oliver
Published: February 2009

In this paper we apply some recent results on the stability of switched systems with interval uncertainty for analyzing the roll stability of automotive vehicles subject to bounded parametric uncertainties and switching. The application is motivated by the fact that the roll dynamics of an automotive vehicle is affected in a significant and a nonlinear fashion due to possible sudden switches in the vehicle's center of gravity (CG) height, as well as the uncertainty in the suspension parameters. Utilizing a recent stability result, it is possible to model such parametric variations as bounded interval uncertainties for this problem, and obtain easily verifiable conditions for analyzing the stability of the resulting switched/uncertain system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)