bluuebunny/crossref_metadata_2025 huggingface dataset:
Research about moving restrictions of cervical spine under the action of mechanical vibrations
Authors: Truţa Aurica , Arghir Mariana
Published: March 2010

The cervical spine is very important human body part, because it sustains the head and it has a higher mobility than the other parts of human spine. The vibration could influence the work performance but also could have a negative influence on human body health. There are many elements, which could be damaged: eyes, ears, brain, mandible, neck's muscle, C1 to C7 vertebras. When the operator is exposed to vibrations for a long time, he can fill a strong pain at the neck. Injuries to the cervical spine are common at the level of the second cervical vertebrae, but neurological injury is uncommon. If it does occur, however, it may cause death or profound disability, including paralysis of the arms or legs. We purpose in this study to develop a biomechanical model for the cervical vertebras and identify the influence of mechanical vibrations on human cervical spine and human head. For this study is necessary to compute the entire moving system of the neck‐head. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mathematical study of a tissue‐implant connection in a ventral hernia repair in a context of the system's parameters
Authors: Lubowiecka I. , Szymczak C. , Tomaszewska A. , Śmietański M.
Published: March 2010

Ventral hernia repair is nowadays a well recognized matter in surgery and advanced techniques of operating are developed. However, mechanical properties of the system after an operation are not known so recurrences of the illness happen. The paper describes a simple mathematical model of a human fascia‐synthetic implant system. The synthetic mesh is modeled by a cable structure and its elastic supports simulate the human fascia. The junction force in the fascia‐implant system is sought. A relation of the force change to variations of some parameters of the system is also studied by applying a sensitivity analysis. The authors conclude that a crucial role for the junction force and a patient's comfort plays the implant's elasticity modulus and initial tension of the mesh is the least important factor. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Visualization of the Motion of the Human Spine in the Context of Gait Analysis through Splines
Authors: Rosenthal Dietmar , Kecskeméthy Andrés
Published: March 2010

The present paper describes an approach for the reconstruction of the motion of the human spine based on marker tracking. The approach uses a spline curve of fifth degree to reproduce the contour of the central marrow line and a set of virtual sliders along the spline with fixed offset distances which model external markers including skin motion. The fitting process is formulated as an optimization problem minimizing the quadratic error between the tips of the sliders and the measured marker positions. The paper also discusses some simplifications of this approach. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of stage I‐crack growth using a 3D‐model
Authors: Köster Philipp , Fritzen Claus‐Peter , Knobbe Helge , Christ Hans‐Jürgen , Krupp Ulrich
Published: March 2010

A three‐dimensional model for stage I‐short crack propagation on a single slip plane is presented. It considers elastic plastic material behaviour by allowing sliding on the active slip plane in a defined slip direction. A crack propagation law based on the crack tip slide displacement is implemented to simulate crack propagation. The model is solved numerically using the dislocation loop technique. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Closed‐form analysis of a higher‐order composite box beam theory
Authors: Kroker Andreas M. , Becker Wilfried
Published: March 2010

A higher‐order theory is developed for composite box beams with rectangular, closed cross‐sections. Each cross‐section is therefore divided into two flanges and webs. Displacement representations are chosen for each part separately. The in‐plane kinematics is 2nd order for the flanges and even 3rd order for the webs. The kinematics of the four parts is interconnected with the help of geometric coupling. All in‐plane stress components can be obtained directly by using a reduced stiffness matrix for each single layer. The layups of the laminates for the flanges and webs are independent from each other. Only a symmetric layup with balanced angles is necessary. The determined differential equation system of 2nd order including four independent functions can be solved completely in a closed‐form analytical manner. As an actual example a cantilever beam under combined bending moment and transverse force is considered. The results obtained by this new theory are compared with the results of a FEM‐model with a very fine shell element discretization. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Load Monitoring of Impacted Carbon‐Fibre‐Reinforced Plastic Plates
Authors: Ungethuem Andy , Lammering Rolf
Published: March 2010

This work deals with a new wave migration model for the determination of an impact location for non‐isotropic plates. The method is based on the wave propagation after the impact. The evaluation and processing of the signals of at least four sensors allow for the calculation of the impact location from the runtime of the signals. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The rotating elastic‐plastic hollow shaft heated at its inner surface
Authors: Arslan Eray , Mack Werner , Eraslan Ahmet N.
Published: March 2010

Based on Tresca's yield criterion and the flow rule associated with it, the behaviour of a rotating linearly strain‐hardening elastic‐plastic hollow shaft heated at its inner surface is studied. Moreover, the residual stresses at stand‐still are depicted. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A finite element framework for continnua with boundary potentials
Authors: Javili Ali , Steinmann Paul
Published: March 2010

This contribution deals with the implications of the anisotropic boundary potential energies on deformational mechanics in the framework of the two‐dimensional finite element method at finite strains. In the first part of this work ([6])) only the isotropic boundary potentials were considered, however, in this contribution we allow for the anisotropic contributions from the boundary energies, too. The boundary effects sometimes play a dominant role in the material behavior, e.g. surface tension in fluids. The boundary potentials, in general, are allowed to depend not only on the boundary deformation gradient but also on the spatial curve‐tangent, as well. For the finite element implementation, a suitable curvilinear coordinate system attached to the boundary is defined and corresponding derivations are carried out. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Failure Analysis on Shell‐like Composite Laminates Using the Puck Criteria
Authors: Lauterbach Stefan , Balzani Claudio , Wagner Werner
Published: March 2010

Due to their high specific strength and stiffness, carbon fibre‐reinforced polymers (CFRP) are widely used in several fields of engineering, e.g. aerospace engineering. A new design scheme aims for the exploitation of material reserves. Since design is always linked to expensive experimental investigations, reliable simulation procedures are required to lower the related costs. In terms of detecting ply failure several criteria have been proposed. In this work those of Hashin [1] and Puck [2] are applied to several numerical models and compared to experimental results [3]. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An asymmetric Least‐Squares Mixed Finite Element for Elasto‐Plasticity at Small Strains
Authors: Schwarz Alexander , Schröder Jörg
Published: March 2010

We present a mixed finite element based on a modified least‐squares formulation for rate‐independent elasto‐plasticity. Due to kink‐like points in the least‐squares functional, the first variation is not always continuous and a standard Newton method could fail in order to minimize the least‐squares functional. In order to keep the availability of the Newton method, we introduce a modified least‐squares approach, which guarantees the continuity of the resulting weak form. Finally, a numerical example is presented to show the applicability and performance. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Elastic‐plastic stress analysis of cracked structures using the boundary element method
Authors: Weber Wilhelm , Steinmann Paul , Kuhn Guenther
Published: March 2010

The application of the boundary element method (BEM) for the 3D‐stress analysis of cracked structures considering elastic‐plastic material behavior is presented. For separating the coincident crack surfaces the DUAL‐BEM is utilized. The relevant boundary integral equations (BIE) – the strongly singular displacement BIE and the hypersingular traction BIE – are evaluated in the framework of a collocation procedure. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental study on the behaviour of steel columns under seismic‐induced axial impact load
Authors: Migda W. , Jankowski R.
Published: March 2010

It has been observed during major earthquakes that the so called soft‐storey failure of an upper floor of a structure results in large impact load acting on structural members of the lower storeys. It may further lead to progressive collapse of the whole structure substantially intensifying human and material losses. Therefore, the aim of this paper is to investigate experimentally the behaviour of columns under bending (observed during an earthquake) that are additionally subjected to an axial plastic impact load. Steel columns with high slenderness ratio were considered in the study. In the experiment, impact load was created by a weight that was dropped onto the top of the column and stayed on it. The weight with the shape of a ball was made of clay so as to simulate more plastic impact. The results of the experiment show that the value of the permanent horizontal deformation of the column observed after impact depends much on the initial relative displacement between the base and the top of the column. As the initial displacement increases the values of the permanent deformation increases significantly indicating the significant reduction in the critical buckling force. The results obtained in the study can be utilized at the design stage of the structures in order to enhance their seismic resistance. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the heat transfer in a two‐phase hollow cylinder with piecewise continuous boundary conditions
Authors: Ostrowski Piotr
Published: March 2010

This consideration concern heat transfer in two‐component composite with a deterministic microstructure, which is Δ‐periodic along the angular axis and has slowly varying effective properties in the radial direction (Fig.1). Therefore, we deal here with a special case of functionally graded materials, FGM, c.f. Suresh, Mortensen (1998). The main aim of this consideration is to capture effect of the discontinuous boundary conditions on the thermal field. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reduction of Periodic Torsional Vibration using Centrifugal Pendulum Vibration Absorbers
Authors: Pfabe Mathias , Woernle Christoph
Published: March 2010

New developments of more environmentally friendly combustion engines cause high fluctuating torques acting on the crankshaft, drive train and auxiliary units. Those result in noise and vibration that are unintentional, especially in automotive engineering. Dual flywheels to damp the vibration are reaching their limits and alternatives have to be found. Centrifugal pendulum vibration absorbers (CPVA) are a long known, energy saving tool to compensate non‐uniform torques. Their main advantage is that they are tuned to a specific order instead of one fixed frequency and therefore they are rotational speed adaptive. This paper presents the fundamentals of CPVA, as well as the equation of motion (EOM), and it shows an analysis for all relevant design parameters. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling of a pyroshock test device
Authors: Lacher Alexander , Juengel Nikolas , von Wagner Utz
Published: March 2010

Pyroshocks are transient motions of structural elements due to explosive loading induced by the detonation of ordnance devices incorporated into or attached to the structure. In space programs the simulation of pyroshocks is a fixed part of the test requirement for instruments and equipments of space vehicles. Therefore, by the use of various test devices such as hammer pendulums the excitation of a pyroshock has to be reproduced which, so far, has led to rather empirical knowledge. In the current work a better predictability of pyroshocks is focussed in order to reduce the duration of test periods. As an approach numerical and analytical calculations are used for the simulation of in‐plane wave propagation in rods and rectangular disks due to mechanical impacts. Furthermore, the results obtained from different mathematical and mechanical theories are compared with data received from conducted experiments. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A surveillance of structural oscillations of industrial robots using optimal control at energy performance index
Authors: Kaliński Krzysztof J. , Jasiński Krzysztof
Published: March 2010

Here is considered vibration of non‐stationary carrying system of the IRb‐6 robot. For a use of vibration surveillance an algorithm of modal control at energy performance index in the frequency domain has been applied. Purpose of the algorithm proposed is to minimise vibration amplitude of manipulating ends, and thus – to increase capacity of modern robot lines as well as, improve accuracy and repeatability of robot positioning. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the bending and tension of thermoelastic shells undergoing phase transitions
Authors: Eremeyev Victor A. , Pietraszkiewicz Wojciech
Published: March 2010

Applying the general non‐linear theory of shells undergoing phase transitions, we derive the balance equations along the singular surface curve modelling the phase interface in the shell. From the integral forms of balance laws of linear momentum, angular momentum, and energy as well as the entropy inequality we obtain the local static balance equations along the curvilinear phase interface. We also derive the thermodynamic condition allowing one to determine the interface position on the deformed shell midsurface. The theoretical model is illustrated by the example of thin circular cylindrical shell made of two‐phase material subjected to tensile forces and bending couples at the shell boundary. The elastic solution reveals the existence of the hysteresis loop whose size depends upon values of several loading parameters. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Formulation of Additive Finite Anisotropic Thermo‐Plasticity in Logarithmic Lagrangean Strain‐Entropy Space
Authors: Ulz Manfred H.
Published: March 2010

A phenomenological model of rate‐independent thermo‐plasticity at finite strains is discussed. The formulation is based on an additive decomposition of the strain measure into an elastic and plastic part as proposed by Green and Naghdi. A constitutive model in the logarithmic Lagrangean strain‐entropy space is developed capable of modelling isotropic elastic and anisotropic plastic material behaviour. The staggered solution scheme for coupled thermo‐mechanical problems employs an isentropic phase for the deformation and an iso‐geometrical phase for the thermal field. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effective Flow Potentials for Anisotropic Polycrystals
Authors: Tsotsova Rumena , Böhlke Thomas
Published: March 2010

In this paper a micromechanically based flow potential for anisotropic fcc polycrystals is derived that takes into account the crystallite orientation distribution function (codf) in terms of tensorial texture coefficients. The effective flow potential is based on a representation theorem for anisotropic scalar functions depending on a 2nd‐order tensor. A priori unknown functions in the representation are determined by defining and solving explicitly a minimization problem over SO(3). Important analytical properties of the coefficient matrix of the minimization problem are discussed. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Material behaviour of filler‐reinforced rubber materials under cyclic loading processes, experiments and FEM‐simulations based on finite viscoelasticity.
Authors: Rendek Martin , Lion Alexander
Published: March 2010

A threedimensional constitutive model of finite viscoelasticity will be presented. It considers the amplitude dependence and is based on a Maxwell chain with intrinsic time scales. This type of viscoelasticity is thermodynamically consistent and provides a basis for modelling other effects (e.g. temperature dependence). The parameter identification for this model is possible in both the frequency and the time domain. Some finite element implementation and simulation results in the time domain are presented. The numerical simulation of multifrequent and other more complicated loading processes is possible only in the time domain. A very interesting loading process is a cyclic deformation with changing amplitudes in order to simulate the transient dynamic behavior of the Payne‐effect. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Analysis of Strains and Stresses in Stretched Specimens at Microstructure Level
Authors: Malag Leszek , Kukielka Leon
Published: March 2010

In the paper an incremental methodology was proposed for the determination of the states of stresses and strains in specimens while taking into account the strain history and the strain rate history during a tension stress, and a new methodology to determine mechanical characteristics of metal materials. An equation of motion and deformation of the specimen was introduced while using a variational formulation and the finite element method. The results of numerical simulations which illustrate the methods proposed, were presented. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐linear elastic behavior of filler aggregates
Authors: Dargazany Roozbeh , Itskov Mikhail
Published: March 2010

A filled rubber network consists of polymer chains which are suspended between filler aggregates. In this contribution, the nonlinear elastic behavior of the aggregated filler particles inside the rubber matrix is investigated. Previously, by using scaling theory, the influence of initial length and fractal dimension of aggregates on the elastic response of aggregated structures was studied. Here we additionally take into account a deformation induced evolution of the aggregate structure. To this end, the directional topology of the aggregate structure is represented by its backbone chain. Thus, the analytical approach proposed describes not only the geometrically but also the physically non‐linear behavior of aggregates. Our solution can further be generalized for colloidal structures as for example granular materials or suspended solid structures. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microstructural changes and material parameter development
Authors: Müller W. H. , Brandmair A. , Sheshenin S.V. , Savenkova M.
Published: March 2010

At previous GAMM‐meetings the first two authors reported on the spinodal decomposition and coarsening in lead‐containing as well as lead‐free solders. They derived an extended diffusion equation for the corresponding computer modelling on the basis of a multi‐component theory of mixtures. Consequently, they performed numerical studies that are capable of predicting quantitatively the development of SnPb and AgCu microstructures. Knowing this development is quite important from a technological point‐of‐view in order to quantify the current joining capability of the solder material (“Resteigenschaften”). On the basis of these results this paper now attempts to predict the corresponding change of the materials properties, in particular of the elastic constants. This is done by means of a homogenization technique developed by the last two authors. In this paper we will briefly summarize the results related to the extended diffusion equation, present numerical simulations of the coarsening process, outline the theory underlying the homogenization and, finally, show how the material properties behave over time. Wherever possible, alternative analytical solutions for the homogenized constants are also presented (e.g., by laminate theory). (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
2D modelling of thin skeletonal elastic shallow shells
Authors: Michalak B. , Woźniak Cz.
Published: March 2010

The subject of this contribution is a certain thin skeletonal elastic shallow shell. The aim of analysis is to derive and apply a 2D‐macroscopic model for shallow shells with the non‐uniformly oscillating microstructure. The main feature of the proposed mathematical model is that the microstructure length parameter λ is similar compared to thickness δ of the shell (λ ≃ δ). The formulation of approximate mathematical model of these shells is based on a tolerance averaging approximation [5]. The general results of the contribution will be illustrated by the analysis of a specific problem. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of Active Noise and Vibration Control with Finite Elements and Boundary Elements
Authors: Ringwelski Stefan , Gabbert Ulrich
Published: March 2010

A recently developed coupled finite element‐boundary element modeling scheme for the design of active noise and vibration control of multi‐coupled structural‐acoustic systems is presented. The approach allows the computation of structural vibrations and resulting sound fields. By means of an example, the paper describes the theoretical background of the coupled approach. In order to show the performance of the developed approach, test simulations are carried out in the frequency domain. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of passive and active elements of reduction of vibrations
Authors: Białas K.
Published: March 2010

The main aim of this work is the introduction of analysis and synthesis of mechanical systems including passive and active elements reducing vibrations. In results of synthesis were received structures and parameters of a discrete model meeting the defined requirements concerning the dynamic features of the system, in particular, the frequency spectrum. In this work is also comparison of these two kind of elements, passive and active, of reduction of vibrations. The approach adopted makes it possible to undertake actions aiming at the elimination of phenomena resulting in the unwanted operation of machinery or generation of hazardous situations in the machinery environment. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The numerical simulation of a typical fluid‐structure interaction problem
Authors: Stoia‐Djeska Marius , Frunzulică Florin
Published: March 2010

To determine the dynamic response of a structure under the influence of the fluid flow one must solve a coupled computational fluid dynamics (CFD) and computational structural dynamics (CSD) mathematical problem. This paper presents the comparison of two methods for the calculation of the fluid‐structure interaction. The first one is of explicit‐implicit type and uses a staggered time advancement of the fluid and structure problems. The second uses a fully implicit discretization in the physical time of the fluid‐structure equations and an explicit advancement in the dual‐time. The physical fluid‐structure problem is accompanied by the equations of the mesh motion, which are written as for a pseudo‐structural system with its own dynamics. Representative numerical results are presented for the two degrees of freedom tipical section in unsteady transonic flow. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Notes on the Computation of Effective Electro‐Mechanical Moduli
Authors: Keip Marc‐André , Schröder Jörg
Published: March 2010

The present work deals with the computational determination of effective material properties of electro‐mechanically coupled materials. In this context, a two‐scale homogenization ansatz for piezoelectric ceramics based on an FE2‐approach is utilized. In this way we are able to compute the overall macroscopic material moduli for microheterogeneous structures. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of diffusional processes from the microscopic and macroscopic point of view
Authors: Ilic Sandra , Hackl Klaus
Published: March 2010

Within this contribution, the modeling of diffusional processes will be elucidated by the example of solution‐precipitation creep. This deformation process occurs in polycrystalline and granular materials exposed to high temperatures and moderate stresses. The presence of water facilitating the material transport in the intercrystalline space especially intensifies the process. The continuum‐micromechanical model presented here considers the velocities of the material transport and the grain‐boundary motion caused in this way to be the main contributions to the dissipation term characteristic for this process. Simulating the real macrostructures in addition requires coupling with homogenization techniques. To this end, our particular choice pertains to the multiscale FE method with the advantages that it is adapted to the case of finite deformations and that it is applicable in the limit case when the ratio of the characteristic lengths of the micro‐ and macroscale tends to zero. As a final result, application of the mentioned method gives information on the time dependency of macroscopic deformations. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic Stall Measurements
Authors: Schneemann Jörge , Wolken‐Möhlmann Gerrit , Peinke Joachim
Published: March 2010

Forces acting statically on an airfoil in laminar flow are well known. Under turbulent conditions dynamic effects (like dynamic stall) take place. There are different theoretical models to describe dynamic stall, but very little experimental data. We present dynamic stall measurements using an FX 79‐W‐151A airfoil in a closed test section of a wind tunnel with laminar inflow. Dynamic stall was induced by pitching the foil sinusoidally. Lift forces were measured using the pressure distribution on the wind tunnel walls. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Proposal for an Invariant Nonlinear Eddy Viscosity Model based on a Consistent 4D Turbulence Modelling Approach
Authors: Frewer Michael
Published: March 2010

The aim of this new approach is to demonstrate that modelling on a 3D spatial manifold is not equivalent to modelling on a true 4D space‐time manifold within Newtonian physics. In the framework of turbulence modelling it will be shown that by geometrically reformulating the averaged Navier‐Stokes equations on a 4D non‐Riemannian manifold without changing the physical content of the theory, additional modelling restrictions will naturally emerge which are absent in the usual Euclidean (3 + 1)D formulation. By proposing a non‐linear eddy viscosity model within the k − ϵ family for high turbulent Reynolds numbers the new invariant modelling approach will demonstrate its clear superiority over current (3 + 1)D modelling techniques. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Measurements with a 2D Laser‐Cantilever‐Anemometer compared to an x‐wire probe
Authors: Puczylowski Jaroslaw , Hölling Michael , Peinke Joachim
Published: March 2010

The 2D Laser‐Cantilever‐Anemometer (2D‐LCA) was developed to measure flow velocities in two dimensions. A sensitive meausuring principle adopted from atomic force microscopes allows a spatial and temporal resolution comparable to modern x‐wire anemometry. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling electrospinning of nanofibres
Authors: Kowalewski Tomasz A. , Barral Serge
Published: March 2010

Electrospinning is based on so‐called bending instability which results in an erratic spiralling motion of the liquid jet as it proceeds towards a collecting electrode, where it is eventually deposited as a mat of micro/nanosized fibres. Most electrospinning models formulated within the slender approximation rely, however, on an inconsistent description of electrostatic interactions which renders them grossly inappropriate whenever the discretization is either too coarse or too fine. The present work aims at proposing a discrete slender model which is numerically consistent (allowing use of arbitrary fine meshes) and remains accurate even for coarse meshes. At the same time, efficient numerical techniques based on hierarchical charge clustering are introduced that drastically decrease computational times. Finally, a versatile boundary value method is implemented to enforce fixed‐potential boundary conditions, allowing realistic electrode configurations to be investigated. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Solitary Roll Vortices in the Mixed Convection of a Vertical Fluid Layer
Authors: Hoffmann Norbert P. , Withalm Martin
Published: March 2010

Some earlier experimental and numerical findings from convection in vertical channels suggest that localized convection rolls could play a role in the transition process of free or mixed convection. In the present work solitary convection roll vortices for a vertical fluid layer with stable stratification, differential shear and differentially heated side‐walls have been obtained numerically for a fluid of unit Prandtl number. The solutions appear through saddle‐node bifurcations and in certain parameter ranges they do also exist for linearly stable basic flow. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transient inviscid flow in a passive linear model of the cochlea
Authors: Obrist Dominik
Published: March 2010

Detailed knowledge of the fluid dynamics within the cochlea is important for a complete understanding of the physiology of this complex organ. We present a numerical simulation in the time domain for the inviscid two‐dimensional flow in a passive cochlea. Numerical results are presented for a click stimulation and an impulsively started tone. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The method of lines for the computation of incompressible viscous flows
Authors: Kosma Z.
Published: March 2010

A common approach to finding numerical solutions of the time‐dependent incompressible Navier‐Stokes equations is considered within the method of lines framework [1]. For the determination of viscous incompressible flows the stream‐function formulation for the fourth‐order equation [2, 3], an artificial compressibility method [4], and a modified velocity correction method [5] are designed. Some improved and extended results of numerical simulations obtained by the author in the previous works are presented. Test calculations have been done for various flows inside square, triangular and semicircular cavities with one moving wall, the backward‐facing step, double bent channels and for the flow around an aerofoil at large angle of attack. An alternative and practical methodology for resolving the Navier‐Stokes equations in arbitrarily complex geometries using Cartesian meshes is proposed. Some of complex geometrical configurations can be decomposed into a set of subdomains. The simplest approach for specifying boundary conditions near curved or irregular boundaries is to transfer all the variables from the boundaries to the nearest grid knots. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical investigation of laminar fluid flow in an oscillating sphere
Authors: Stein Anika , Rütten Markus , Wünsch Olaf
Published: March 2010

The paper deals with the numerical simulation of three dimensional oscillating fluid flow of filled and partial filled hollow spheres. We use a program based on finite volume method developed by the DLR. Our main interest is on the secondary flow in the middle plane. Results are presented for Newtonian fluids in dependence of different boundary conditions which are compared with analytical and experimental investigations. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hybrid, numerical solutions, for three‐dimensional, compressible Navier‐Stokes layer
Authors: Nastase A.
Published: March 2010

The author proposes new hybrid solutions for the three‐dimensional, compressible Navier‐Stokes layer (NSL) over a flying configuration (FC), which use the analytical potential solutions, of the same FC, two times, namely: to reinforce the numerical solutions by multiplying them with these analytical solutions and as outer flow (instead of the parallel flow, used by Prandtl in his boundary layer theory). These hybrid solutions fulfill the last behavior, have correct jumps along the singular lines (like subsonic leading edges, junction lines wing‐fuselage, etc.), are split, accurate and rapid convergent. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Sensitiveness of Absorption Coefficient to Changes in Material Parameters
Authors: Langer Sabine , Al‐Kharabsheh Dina , Wulkau Meike
Published: March 2010

An essential property of porous absorbers is the resistance to the incident sound wave, resulting in a damping effect. Damping results from the friction between air molecules and absorber pore‐walls. In practice, the known dependencies of the sound absorption coefficient are used in the design of absorbers. But not every material can be characterized by a one‐parameter model. The reliability of prediction can be improved by using detailed material models. Hence, additional material parameters, especially the pore geometry are needed. Since in practice the effort for determining material parameters must be minimized, this paper discusses the sensitivity of prediction of absorbers' performance depending on the influence of material parameters that are input for the prediction model chosen. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recent progress on contactless inductive flow tomography
Authors: Wondrak Thomas , Stefani Frank , Gundrum Thomas , Gerbeth Gunter
Published: March 2010

The contactless inductive flow tomography (CIFT) is a technique to reconstruct the velocity in electrically conducting melts using magnetic fields. One of its application could be the velocity reconstruction in the mould of the continuous casting process. In this paper, we present the numerical investigation and first measurements of the induced magnetic field taken in our lab on a small model of a continuous casting mould. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal wireless sensors' location for monitoring of structures in randomly disturbed environment
Authors: Dunajewski I. , Kotulski Z.
Published: March 2010

In the paper we present the specific conditions that appear in structures' monitoring by means of Wireless Sensor Networks (WSN). First, we introduce the problem of optimal sensors' location for structures monitoring and its specific constraints if one uses WSN. We formulate the conditions that must be taken into account during optimization. Then, we give an example of temperature measurements and formulate the procedure that leads to finding optimal wireless sensors locations. Finally, we present the experimental observations of wireless sensors in the network that strongly affect on the temperature estimation on a basis of the collected measurements. We conclude with remarks concerning WSN practical design for permanent structures' monitoring to obtain exact and reliable results. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of stochastic point processes in mechanics
Authors: Iwankiewicz Radoslaw
Published: March 2010

Stochastic point processes are the mathematical tools relevant to all problems where the phenomena have the nature of a random train of events. Applications may be found in structural dynamics where some stochastic excitations may be adequately idealized as random trains of impulses or general pulses. An example of application in mechanics of materials is the stochastic model of the grain growth processes in polycrystalline nanomaterials. Based on the stochastic differential equations formulation, analysis methods such as the moment equations method or the method of equation for the response probability density are dealt with. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An introduction to nonlinear problems with random parameters by the Stochastic perturbation‐based FEM
Authors: Kamiński M.M.
Published: March 2010

The main aim of this paper is to present an algorithm and the solution to the nonlinear problems with random parameters. The methodology is based on the generalized nth order stochastic perturbation method and, on the other hand, on the Finite Element Method adjacent to the physical and geometrical nonlinearities. The perturbation approach resulting from the Taylor series expansion with uncertain parameters is proposed in two different ways – thanks to the straightforward differentiation of the initial incremental equation and, separately, using the modified Response Function Method. This approach is illustrated with the analysis of the simply supported elastoplastic beam loaded centrally with the concentrated force, where the probabilistic moments for the limit load and the reliability indices are determined via the stochastic symbolic computations. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal Design of Plane Frames under Uncertainty: A Comparison of Two Approaches
Authors: Zier Simone
Published: March 2010

Using the first collapse theorem, the necessary and sufficient survival conditions of an elasto‐plastic structure consist of the yield condition and the equilibrium condition. In practical applications several random model parameters have to be taken into account. This leads to a stochastic optimization problem which cannot be solved using the traditional methods. Instead of that, appropriate (deterministic) substitute problems must be formulated. Here, the design of plane frames is considered, where the applied load is supposed to be stochastic. In the first approach the recourse problem will be formulated in the standard form of stochastic linear programming (SLP). In order to apply efficient numerical solution procedures (LP‐solvers), approximate recourse problems based on discretization (RPD) and the expected value problem (EVP) are introduced. In the second approach – based on the yield condition – a quadratic cost function will be introduced. After the formulation of the stochastic optimization problem, the expected cost based optimization problem (ECBOP) and the minimum expected cost problem (MECP) are formulated as representatives of appropriate substitute problems. Subsequently, comparative numerical results using these methods are presented. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adaptive solution of elliptic PDE‐eigenvalue problems.
Authors: Mehrmann Volker , Międlar Agnieszka
Published: March 2010

In this paper we introduce a new adaptive algorithm (AFEMLA) for elliptic PDE‐eigenvalue problems. In contrast to other approaches the algebraic eigenvalue problem does not have to be solved to full accuracy. We incorporate the iterative solution of the resulting finite dimensional algebraic eigenvalue problems in the adaptation process in order to balance the cost with the costs for the iterative eigenvalue method. We present error estimates that incorporate the discretization errors, approximation errors in the eigenvalue solver and roundoff errors. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Optimal Control Using Particle Methods
Authors: Marburger Jan
Published: March 2010

Mesh‐based methods like finite elements and finite volumes enjoy limited use in deforming domain and free surface applications due to exorbitant computational demands. Instead, particle methods are very suitable for simulating such problems. However, they have not been used for optimisation yet. We therefore derive optimisation strategies using this kind of methods. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Model Predictive Control for Nonlinear Parabolic Differential Equations Based on a Linear Quadratic Gaussian Design
Authors: Benner Peter , Hein Sabine
Published: March 2010

We consider optimal control problems for semilinear parabolic partial differential equations where process and measurement noise can occur. If we apply a Model Predictive Control (MPC) scheme we obtain optimal control problems on small time intervals. The resulting “smaller problems” can be linearized around a reference and solved by using a Linear Quadratic Gaussian (LQG) design. We present some theoretical background of the strategy above as well as results of a numerical implementation for a 3D problem. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling of working machines seat suspension with an air‐spring and hydraulic shock‐absorber
Authors: Maciejewski Igor
Published: March 2010

For the purpose of this paper, an exemplary seat suspension system is modelled and simulated numerically. The system consists of a shear guidance mechanism of a suspended seat, an air‐spring, a hydraulic shock‐absorber and end‐stop buffers. As results of computer simulations, the power spectral densities of acceleration and the transmissibility functions of seat suspension are evaluated with respect to results measured experimentally. The verification of simulation model is performed in the basis of Seat Effective Amplitude Transmissibility factor (SEAT) and the maximum relative displacement of suspension system. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimisation of pneumatic circuit aimed at improving the vibro‐isolation properties of seat suspension
Authors: Maciejewski Igor , Kiczkowiak Tomasz , Krzyzynski Tomasz
Published: March 2010

The object of a numerical simulation and optimisation is the seat with a visco‐elastic passive suspension, with improved vibro‐isolation properties by means the multi‐criteria optimisation. Basing on the verified passive seat suspension model, a modification of the pneumatic circuit in order to help the working machines operators against vibration is considered. The root mean square (RMS) acceleration measured at the seat and the maximum relative displacement of the seat suspension are minimised as the chosen vibro‐isolation criteria. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of molecular water models on Molecular Dynamic simulation of nanoflows
Authors: Bytnar J. , Kucaba‐Piętal A. , Walenta Z.
Published: March 2010

We study an influence of the effect of water molecular models and thermostats on approaching equilibrium in Molecular Dynamics simulation of the nanoflows of water. Out of large number of existing models of water we present the results for four selected ones, i.e.: TIP4P, PPC, TIP4P‐2005, TIP5P, and for two thermostats ‐ Gaussian and Nosé‐Hoover. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Definitizability of a Class of J‐Selfadjoint Operators with Applications
Authors: Behrndt Jussi , Philipp Friedrich , Trunk Carsten
Published: March 2010

We formulate an abstract result concerning the definitizability of J‐selfadjoint operators which, roughly speaking, differ by at most finitely many dimensions from the orthogonal sum of a J‐selfadjoint operator with finitely many negative squares and a semibounded selfadjoint operator in a Hilbert space. The general perturbation result is applied to a class of singular Sturm–Liouville operators with indefinite weight functions. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Singular Indefinite Sturm‐Liouville Operators with a Spectral Gap
Authors: Behrndt Jussi , Möws Roland , Trunk Carsten
Published: March 2010

Singular Sturm‐Liouville operators with the indefinite weight sgn(·) and a symmetric potential which has a positive limit at ∞ have a gap in the essential spectrum. Under an additional condition it is shown that in this gap are no eigenvalues. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Applying the Zigbee technology for the enhancing the remote objects control
Authors: Wojnarowski Józef , Borowik Bohdan
Published: March 2010

The paper presents the monitoring and measurement processes for the remote object vibration in the plain space. Wireless, RF communication in Tx/Rx duplex mode provides transfer of data with ZigBee transceivers. Presented ZigBee technology operates in many various modes on frequency 2.4 GHz allowing the coordinator node to select certain path and data. ZigBee technology can be alternative for other vibration research techniques. The vibration displacement is processed further by DSP Digital Signal Processing, made with the microcontroller. Accelerometer applications due to embedded control and I/O digital signal processor DSP play the crucial role in determining vibration and machines fatigue strength testing. It registers, among other, the temporary industrial parameters and monitors plant system parameters such as vibration and/or pressure. The paper presents diagnostic procedure and measurements process of the vibration in the plain space. Role of the node play ZigBee transceivers. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of a Hybrid‐Forming Process using Temperature‐ and Rate‐Dependent Viscoplastic Material Models
Authors: Sauerland Kim‐Henning , Schneidt Andreas , Mahnken Rolf
Published: March 2010

Hybrid‐forming processes for graded structures are quite innovative methods for the production of components with tailored properties, particularly tailored material properties and geometrical shape. In this contribution a hybrid‐forming process based on the utilization of locally varying thermo‐mechanical effects is investigated [1]. For process optimization and improvement of the resulting work piece the simulation of the entire forming process is necessary in modern engineering. The main topics of this contribution are the simulation of the cyclic thermal loaded forming tool and the simulation of the work piece treated at large deformations with phase transformations. For both materials temperature‐ and rate‐dependent viscoplastic material models are applied and parameter identification using cyclic tensile‐compression tests for the forming tool material and phase transformation tests for a low‐alloy steel similar to the work piece material is presented. For validation of finite‐element‐calculations for the forming tool thermal shock experiments are performed with optical deformation measurements. For validation of finite‐element‐calculations for the work piece numerical results of geometry and structure after heating, forming and cooling are compared to experimental micro sections. Results concerning the forming tool will be used for future lifetime prediction and results concerning the work piece will be used for future specific setting of graded material properties. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stability and free vibrations of discrete frame subjected to the generalised load by the force directed towards the positive pole
Authors: Podgórska‐Brzdękiewicz Iwona
Published: March 2010

The work refers to stability and free vibrations of discrete, two‐part planar frame with three degree of freedom. For the considered frame the total mechanical energy is determined on the basis of the external load of the structure, whose direction of action depends on geometry of loading and receiving head. Adequate relationships describing stability of the considered frame are obtained taking into account potential energy of the system (static criterion) or total mechanical energy (kinetic criterion). An influence of geometrical parameters of loading head and rigidity of rotational springs modelling the finite stiffness of structural constraints on the critical load is analyzed. The courses of natural vibration frequencies in relation to the external loads are determined for the assumed values regarding geometry and physical constants of the system. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)