bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kopplung starrer und flexibler Strukturbereiche unter Verwendung üblicher Finit‐Elemente‐Diskretisierungen
Authors: Goettlicher B. , Schweizerhof K. 
Published: March 2011

AbstractTreten in Strukturen Bereiche stark unterschiedlicher Steifigkeiten auf, ist es im Hinblick auf transiente Berechnungen sehr effizient und insbesondere für Überschlagsuntersuchungen sinnvoll, auch bei bereits vernetzten FE‐Strukturen Bereiche relativ hoher Steifigkeit durch Starrkörper zu ersetzen. Mit dieser Maßnahme wird eine schlechte Konditionierung des FE‐Gleichungssystems vermieden und der Berechnungsaufwand in Abhängigkeit vom Anteil der Starrkörper reduziert.Die Kopplung von starren und flexiblen Teilkörpern erfolgt über Zwangsbedingungen, die auch für geometrisch nicht‐lineare Probleme Gültigkeit haben. Damit können beliebige Teile der FE‐Struktur mit geringen Aufwand als starr modelliert werden und beliebige Randbedingungen definiert werden. Hierbei ist die Problematik großer Rotationen gesondert zu beachten. An einem Schalentragwerk unter statischer Beanspruchung wird exemplarisch die funktionsfähigkeit des Verfahrens diskutiert. Damit steht für die Modellierung ein außerordentlich effizientes Werkzeug zur Verfügung.
Nonlinear Shell Theory in Convective Description
Authors: Herold M. , Ulbricht V. 
Published: March 2011

AbstractStarting from the basic equations of the three‐dimensional continuum a shell theory will be derived, considering geometrically and physically nonlinear effects, transverse shear strains and thickness stretching. Motion is described using a material description with convected coordinates. This means the independent variables are the material coordinates θi of the material points r and the time t. Due to the specifics of this description the shape of the coordinate lines, the base vector system and the metric are dependent on space and time. In this case a rate formulation of the field equations proves to be useful, which leads to a nonlinear initial‐boundary value problem.The nonlinearity is implied in the initial value problem whereas the boundary value problem is linear in terms of displacement rates.
An improved reduced basis method to solve nonlinear problems
Authors: Imazatene A. , Zahrouni H. , Potier‐Ferry M. 
Published: March 2011

AbstractMany works have established the efficiency of asymptotic numerical methods (direct computation of series, the use of Padé approximants, or the reduced basis technique) to solve nonlinear problems (see ]1[). It has been written (see ]2[ that the reduced basis technique (Rayleigh‐Ritz method) is the most efficient in term of step lenght. Nevertheless, as long as a cheaper algorithm to compute the coefficients of the reduced problem is not found, the most attractive technique remains the rational fictions. In this work is presented an attempt to reduce this computation time. The method consists an coupling Padé approximants with the reduced basis technique in order to obtain an efficient algorithm.
Numerical Simulation of Mechanical Behaviour of Textile Surfaces
Authors: Janński L. , Ulbricht V. 
Published: March 2011

AbstractThe paper presents a model which can be used for calculations of complex mechanical behaviour of textile surfaces e.g. surfaces obtained from a drapemeter. Fabric is treated an this model as a two‐dimensional continuum. As kinetic and kinematic measures are used these of the Cosserat continuum. Linear elastic, orthotropic constitutive equations which enable independent treatment of the in plane and out of plane deformations, describe material behaviour of the textile structure.
Randintegralgleichungsverfahren zur Berechnung der Fluid‐Struktur Interaktion
Authors: Nolte B. 
Published: March 2011

AbstractMit der numerischen Kopplung von Randintegralgleichungen kann man die akustische Fluid‐Struktur‐Interaktion be‐rechnen. Vorteil ist die automatische Erfüllung der Sommerfeldschen Ausstrahlbedingung in den Außenraumgebieten, da die Greenschen funktionen des Vollraumes der zugrundeliegenden partiellen Differentialgleichungen Verwendung finden. Eine klassische Finite‐Element Formulierung führte in diesen Fall zu artifiziellen Rändern mit physikalisch nicht existierenden Eigenlösungen im Außengebiet.
Numerical Efficiency of Different Partitioned Methods for Fluid‐Structure Interaction
Authors: Steindorf J. , Matthies H. G. 
Published: March 2011

AbstractThe numerical simulation of coupled problems is one of the great challenges in scientific computing. In this paper, we consider partitioned methods for unsteady fluid‐structure interaction, where different codes are used for the different physical domains. There are various procedures how to couple the fluid and structure part: the coupling conditions and the moving domain can be treated in a fully explicit or implicit or in a mixed explicit/implicit manner. Depending on the different coupling procedures, the numerical efficiency of the staggered partitioned methods is investigated.
Segmentation of Piezo‐Elements in Structural Vibration Control
Authors: Pietrzakowski M. 
Published: March 2011

AbstractThe paper is aimed at active damping of structural vibrations of a simply supported beam by using multiple piezoelectric patches as collocated sensors and actuators. The control concept is based on the velocity as well as proportional‐velocity feedback. Dynamic responses of the system are obtained by applying the static model of actuatorsubstructure coupling with perfect bonding. For the suppression of the low modes several arrangements of the sensor/actuator pairs are proposed and numerically investigated.
The Stability and Sensitivity Analysis of Structure Supporting Turbo‐generator with Regard to Parametric Effects
Authors: Wójcicki Z. , Grosel J. 
Published: March 2011

AbstractThe paper is continuation of the research presented in GAMM'98. The problem of the influence of an axial vibration (axial dynamic loads) of the columns which are parts of the structure supporting turbo‐generator on the lateral parametric vibration this structure is analysed. The general conclusion is that the axial vibration changes the parametric steady‐state lateral vibration very much and it is inadmissible to neglect its influence. Moreover, the dynamic instability regions can be observed, despite of it that the magnitude of the whole axial force is only about 30% of the Euler's critical value for the column. The dynamic stability and the first order sensitivity analysis in the time domain of the steel, spatial, orthogonal frame supporting small turbo‐generator structure ]1[ shown in Fig. 1 is carried out. One column is extracted from the original structure, Fig. 2. Dimensions, stiffness and mass parameters of the strut are the same as in the structure supporting turbo‐generator. Rotary inertia of mass element at the top of the column and rotary stiffness of spring fixed the column are chosen to fit particular eigenvalue of the original structure, The axial and lateral sinusoidal changing forces, periods of which are commensurable, load this elastic fixed column. The FEM is used to solve the dynamic model. Numerical and analytical calculations are supported by the computer system “Mathematics”, “COSMOS/M” as well as author's software.
Linear‐quadratic optimal control of high index singularly perturbed systems
Authors: Mikhailov S. A. , Müller P. C. 
Published: March 2011

AbstractWe consider singular singularly perturbed problems (SSPP) where the reduced DAE system has index > 1. Using terminology of descriptor systems literature, we will call these systems high index singularly perturbed systems. Tikhonov‐Levinson theory and standard time‐scale modeling do not apply for the SSPP. Therefore the related subjects have to be considered in the course of linear‐quadratic optimal control design. These difficulties can be alleviated by means of decoupling the slow and fast motions in SSPP. We analyse the general structure of optimal hear‐quadratic control design.
Stability of a rotor supported on journal bearings with piezoelectric elements
Authors: Przyblowiczm P. 
Published: March 2011

AbstractThe paper is concerned with stability analysis of a rotor supported on journal bearings with circular piezoelectric bush made of lead zirconate titanate (PZT). It is known that, apart from many other structural parameters, the oil gap in journal bearings constitutes one of the most important factors responsible for stability of such systems. The piezoelectric ring is capable of changing its radial dimension under a voltage applied to it. The voltage signal can be coupled with angular velocity of the rotor that makes the system adaptive to varying operational conditions. It means that increasing angular velocity slightly diminishes the oil gap what protects the rotor from self‐excited vibration that normally occurs at a certain critical rotation speed. The paper is 20 find the answer 20 what extent the method is effective, i.e. to evaluate quantitatively how far it can shift the critical threshold towards higher rotation speeds, enlarging this way the range of stable working of the rotor.
On the effective elasticity tensor of cellular materials obtained by an energetic homogenization procedure
Authors: Hohe J. , Becker W. 
Published: March 2011

AbstractAim of the present study is the determination of the effective elastic properties of cellular materials using two‐dimensional cellular structures which are common as core materials for structural sandwich panels as a model material. The cellular microstructure is homogenized by a strain‐energy based RVE‐procedure assuming that strain states, which are equivalent on the macroscopic level, lead to equal strain energy in a representative volume element whether the real microstructure or the quasi‐homogeneous “effective” medium is considered.
Bending of Beams in Superelasticity Domain
Authors: Kosel Franc , Bundara Borut 
Published: March 2011

AbstractThe paper deals with bending of beams made of shape memory material (SMM). The research is focused on the modelling of a bending process in the superelasticity region, which w one of the characteristics of SMM. On the basis of a chosen physical model, a computer program has been set up for numerical modelling of the stress‐strain and displacement state in a beam made of a SMM exhibiting superelasticity, subjected to bending load. The proposed physical model has been verified experimentally using specimens made of Ni‐Ti alloys. The shape‐memory effect is a unique property that some alloys possess according to which, after being deformed at one temperature, they recover their original shape upon being heated to another temperature. The built‐in memory is produced by the martensitic transformation. The effect was first discussed the Russian metallurgist G. Kurdjumov. In 1951, L. C. Chang and T. A. Read reported its occurrence in an Ni‐Ti alloy. However, application of this phenomenon came only after the development of the Ni‐Ti alloy by the Naval Ordnance Laboratory (NITINOL) in 1968. Many technical problems have been successfully solved using some of the features of SMM like one‐way shape memory, pseudoelasticity, two‐or multi‐way shape memory effect. However, designers encounter many problems trying to analytically determine stresses, strains and displacements of structural elements of SMMs. Two separate mechanical effects characterise the response of SMM, these are: strain‐memory effect and superelasticity. Both of these phenomena strongly depend on temperature. In some alloys both of these effects can appear but at a different temperature. In this paper our research is focused on studying the superelastic phenomenon of a SMM. The superelasticity phenomenon can appear in a SMM in the case when two conditions have to be fulfilled as follows: a.) The temperature in the SMM has to be between the finish austenite temperature Af and the pseudoelastic temperature Md; and b.) A value of stress state in the SMM has to be appropriate so that the stress martensite can appear.
The Method of Asymptotic Expansion for Plate Problem in the Linear Theory of Viscoelasticity
Authors: Lotfi A. , Molnárka G. 
Published: March 2011

AbstractThe method of asymptotic expansion originally developed for elasticity problems is generalized to linear stic problems. Three‐dimensional, unsteady problems corresponding to a class of viscoelastic plates are considy employing the Laplace transform, the original problem is converted to an equivalent elastic problem, where mptotic expansion method is used. An application of this method to the Maxwell model is also presented.
Design Sensitivity of the Beam with Periodically Variable Geometry under Harmonic Excitation
Authors: Mazur‐Jniady K. , Sniady P. 
Published: March 2011

AbstractThe paper presents an approach to the problem of testing the sensitivity of a structure to the change of its design parameters on the example of a beam. In the paper the dynamic responce of periodic‐like straight beam with variable cross section is analysed. The approach adapted in the paper is baaed on concepts of the dynamics of periodic‐like structure ]1[. In this way we are able to formulate the averaged equations of structured beams which describe the length‐scale effect.
A study to determine an adequate constitutive equation for the behaviour of beech wood
Authors: Silber G. , Benderoth G. 
Published: March 2011

AbstractLiving organisms are optimized by nature due to minimize the consumption of material and energy for building and maintaining themselves. Therefore all load bearing structures are weight minimized for resisting a particular load. Technical materials are still far away from load/weight relations adchieved by nature ]4[‐ It is worth while to examine these “natural experiments” to use the results for building more efficient structure with regard to materials. As an objekt of investigation wood stems were chosen because the load cases are quite simple (bending by wind forces and compression by the crown and stem 's own weight) and the internal structure of the composite material shows only transversal isotropy.
A Minimum Problem Defining Effective Isotropic Elastic Properties
Authors: Böhlke T. , Bertram A. 
Published: March 2011

AbstractThe paper discusses a special aspect of averages approximating the elastic properties of polycrystalline aggregates with a uniform orientation distribution. It is shown that the well known isotropic estimations by Voigt and Reuss and a recently suggested geometric mean of the local elasticity tensors minimize their distances to the single crystal elasticity tensors as well as to the corresponding volume averages. In this analysis, only the influence of the grain orientation distribution on the macroscopic response is considered.
Can Linear Potential Theory Predict Supersonic Jets?
Authors: Dillmann A. 
Published: March 2011

AbstractFifty years ago D.C. Pack presented his analytical series solution for a slightly over‐or underexpanded supersonic jet emerging from a circular nozzle. However, non‐uniform convergence, caused by singularities, makes direct numerical evaluation impossible. Therefore, Pack was unable to verify his solution, and during the following decades there was considerable doubt about its physical relevance. The present paper aims at answering the above question by a direct comparison of experimental Mach‐Zehnder interferograms with corresponding theoretical images computed from Pack's analytical solution.
Optimal path synthesis of the four‐bar mechanism
Authors: Iztok Ciglaric , Krasna Simon , Prebil Ivan 
Published: March 2011

AbstractFour‐bar mechanisms are widely used in different devices as leading mechanisms that have to provide desired and often complicate motion and sustain substantial forces, accelerations and jerks. As the four‐bar mechanism seems to be a simple device, it is well known that dimensional synthesis is an exacting piece of work. One has to determine the proportions of link lengths needed to accomplish the specified motion and force transformation. Paper discusses optimal synthesis of four‐bar mechanism. The objective of this approach is to determine the optimal values of the mechanism link lenghts, to minimize the difference between the trajectory “T” of the arbitrary point C on the mechanism coupler link and prescribed trajectory “P”, while hinge forces have to remain within the prescribed values.
Optimization of Patch Reinforcements around Circular Holes in Isotropic and Anisotropic Plates
Authors: Engels H. , Becker W. 
Published: March 2011

AbstractFor various technical reasons cutouts like holes in thin‐walled structures are often inevitable. Applied loads lead to an undesired stress concentration and respective strength degradation in the hole vicinity. In order to reattain the requested strength in practice a local hole reinforcement is applied. The techniques of mathematical structural optimization have been applied in order to determine an optimal design for the hole reinforcement.
Erweitertes Optimierungsverfahren für den Spritzgießprozess
Authors: Meckbach S. , Ehrenstein G. W. 
Published: March 2011

AbstractZur Prozessoptimierung beim Spritzgießen wird ein Betriebspunkt bestimmt, an dem vorgegebene Eigenschaften der Teile eingehalten werden und der Prozess unempfindlich gegen Störungen ist. Das vorgestellte Optimierungskonzept basiert auf Antwortflächen, welche durch Scattered Data Interpolation Methoden erzeugt werden. Probleme die im Zusammenhang mit der Wahl des geeigneten Interpolationsmodells auftreten werden diskutiert.
RSM Based Design Optimization
Authors: Rijpkema J. J. M. , Schoops A. J. G. , Etman L. F. P. 
Published: March 2011

AbstractResponse Surface Models (RSM) based on data from designed numerical experiments are useful as approximation models in Engineering Optimization. Their construction can be enhanced by the inclusion of design sensitivity data. In this short paper we discuss two strategies to accomplish this. We compare both strategies in a numerical example and draw some general conclusions regarding their practical value.
Distributed Dynamic Process Simulation
Authors: Ehrhardt K. , Borchardt J. , Grund F. , Horn D. 
Published: March 2011

AbstractIn chemical process industry a heterogeneous simulation concept is required which distributes the solution of a dynamic overall model to a computer network such that the submodels of the global process flowsheet can be solved independently of each other on subsequent time intervals. To this end a iteration technique is used which estimates the vector of input variables of the submodels, calculates the corresponding time behaviour of the output variables concurrently, and matches then the profiles of the interconnecting variables of the overall process model iteratively. For the common case that the submodels do not provide input‐output sensitivities a specific Broyden‐type acceleration of this waveform iteration method is considered.
Computing roots of matrix products
Authors: Fassbender H. , Benner P. 
Published: March 2011

AbstractThe problem of computing a kth root of a matrix product W = Πki=1 Ai is considered. The explicit computation of W may produce a highly inaccurate result due to rounding errors, such that the computed root W1/k is far from the actual root W1/k. An algorithm for computing the square root of W is presented which avoids the explicit computation of W by employing the periodic Schur decomposition and therefore yields better accuracy in the computed root W1/2. In principle, the techniques are applicable to k > 2 as well but lead to solving 2 × 2 polynomial matrix equations which are difficult to treat. The case k = 3 is also addressed briefly.
The generation of high quality difference and error formulae of arbitrary order on 3‐D unstructured grids
Authors: Adolph T. , Schónauer W. 
Published: March 2011

AbstractWe generate difference and error formulae of arbitrary consistency order on 3‐D unstructured grids for the finite difference method. Therefore we have to collect grid points so that we can determine the influence polynomials on which the generation of the formulae is based. The problem is to select the appropriate points so that we receive a well‐structured system of equations of the finite difference method and a good error estimate. We present an algorithm for this selection that is controlled by two parameters. The high quality of the formulae is shown by an example.
On the Numerical Solution of the Hyperbolic Evolution Problem on Closed Curve
Authors: Roman Chapko 
Published: March 2011

AbstractWe consider on evolution problem for a hyperbolic equation with the Dirichlet to Neumann operator. For the numerical solution we combine the Laguerre transformation with respect to the time variable and the boundary integral equation method. Then an infinite sequence of the integral equations of the second kind with a logarithmic singularity is obtained. The full discretization is realized by Nyström's method which is based on trigonometric quadrature rules.
Reichweitensteigerung bei Hyperschall‐Notflugbahnen durch Optimalsteuerung des Treibstoff‐Ablaßvorgangs
Authors: Sachs G. , Mayrhofer M. 
Published: March 2011

AbstractEin Missions‐Abbruchszenario von zweistufigen Raumtransportsystemen betrifft antriebslose Notflugbahnen der Orbitalstufe nach Trennung von der Trägerstufe. Hierfür wird dargelegt, daß die optimale Steuerung des Treibstoff‐Ablaßvorgangs eine Steigerung der erzielbaren Reichweite ermóglicht.
Rotating polyhedral flames
Authors: Class A. G. 
Published: March 2011

AbstractBy systematically changing the mixture composition of a flame on a Bunsen burner the conical shape of the flame can suddenly be transform into triangular cells forming a polyhedron. Often the polyhedron rotates rapidly about its vertical axis. We present a weakly nonlinear analysis which results in a Kuramoto‐Sivashinsky equation describing cellular flames, which is coupled to a heat equation modeling the temperature of the burner rim. Numerical computations of the coupled set of equations exhibit rapidly rotating polyhedral patterns, which show the typical saw‐toothed shape of the corrugations of the flame. In contrast to earlier considerations of this problem, where the rotation is explained as a result of mode interactions, we find a primary bifurcation to a rotating state, which may explain the high speeds of revolution.
A remark on second order methods in control of fluid flow
Authors: Hinze Michael 
Published: March 2011

AbstractWe present the functional analytic framework for a tracking‐type control problem of the instationary Navier‐Stokes equations. As solution methods for the control problem we comparatively discuss Newton's method as an example of the black box approach, and the SQP‐method as one of the all‐at‐once methods. It is argued that black box approaches in general outperform all‐at‐once methods since the numerical effort necessary to numerically solve linearizations of the instationary Navier‐Stokes equations compares to that of the nonlinear Navier‐Stokes system. We report a numerical comparison which illustrates our argumentation. For both approaches local convergence results are cited.
On the interaction of a 2‐dimensional transonic turbulent boundary layer with a localized 3‐dimensional disturbance
Authors: Kluwick A. , Kronberger R. 
Published: March 2011

AbstractIf a weak normal shock wave impinges on a fully attached transonic turbulent boundary layer, a three layer structure develops. In the outer defect region the solution of the interaction problem may be described as an irrotational perturbation to the oncoming stream. Hence a potential can be introduced, which is governed by a generalized transonic small‐disturbance equation. In the present study it is shown that, for a suitable scaled problem, the interaction of the incoming boundary layer with a small 3‐dimensional obstacle can be described by an equation of similar type. Numerical studies are carried out focusing on the formation of the local supersonic region within the defect region of the boundary layer.