bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biorthogonal wavelets and approximations of operators
Authors: Guichaoua M. , Liandrat J. 
Published: March 2011

AbstractWe present an explicit scheme, based on wavelets, for the approximation of evolution equations of type δU/δt/ + δ/δx (f(U)) = 0. It is constructed using a Taylor scheme for the time approximation and a wavelet method for spatial approximation. This scheme is shown to be stable and convergent under a specific stability condition and can be implemented fast on c‐structured wavelet spaces of approximation thanks to the introduction of scheme dependant biorthogonal multiresolution analyses.A scale dependent time step version is presented that allows a strong reduction of complexity. For discontinuous solutions, a non linear version has been proposed and numerically tested.
Friction and Wear at Tractive Rolling of Cylinders
Authors: Deters L. , Engel St. , Proksch M. 
Published: March 2011

AbstractBased on the fundamentals of tractive rolling contact mechanics, a method is described which is suited for calculating traction coefficients. Both the deformation and the adhesion component of friction are taken into consideration. It is demonstrated that the maximum traction coefficient is not a constant, but takes different values under various load conditions as a result of changes in the micro‐geometrical pattern. Using the load‐specific maximum traction coefficient it is possible to predict a fairly accurate value of the traction coefficient of the tractive rolling contact.In addition, the results of wear investigations are reported, and an approach to apply test results to the real wheel/rail system is described. The tests were carried out with materials common in railway design; in particular, R7 wheel material and standard‐grade 900A rail material were used. During the tests the normal force and the creep were varied. Wear investigations conducted on the test machine revealed that the relationship between friction work and wear volume is an almost linear function.
Solid Friction studied via Non‐Equilibrium Molecular Dynamics Computer Simulations
Authors: Kröger M. , Hess S. 
Published: March 2011

AbstractThe embedded atom method is adapted to study solid friction and the mechanical behavior of a model metal. The elastic properties of real metals are reproduced by a set of basic model potentials as revealed by analytic considerations. Non Equilibrium Molecular Dynamics NEMD computer simulations are performed to study the dynamics and structural changes of the model metal undergoing a process of solid friction and an uniaxial compression, in order to analyze, e.g. plastic yield and transient friction coefficients.
Numerical simulation of the formation of short pitch corrugation
Authors: Müller S. , Knothe K. 
Published: March 2011

AbstractThe formation of periodic wear patterns on the running surface of the rail has been observed for more than a hundred years. These wear patterns are the reason for unwelcome effects like noise and damage to the track. A high number of publications was concerned with the problem and most rail corrugation types can be explained to date [3]. Only the mechanism which leads to so called short pitch corrugation is not understood yet. Therefore, based on previous work [2] [5] a linear wheel‐track model has been developed to understand the formation of short pitch corrugation on tangent track. Numerical simulations have been undertaken with this model to analyse the corrugation process. Based on numerical results it is tried to explain why the corrugation pitch observed in practice vary little with train speed and it is shown how wheel‐rail parameters influence the proneness to corrugation.
Control of jets expansion by impeding jets
Authors: Denis S. , Delville J. , Garem J‐H. , Bonnet J‐P. 
Published: March 2011

AbstractThe principle retained to control the expansion of a jet, is bused here on the generation of streamwise vorticity by impeding jets. Experiments are performed in the mixing layer of two coaxial jets. The rectangular control jets arc placed all around the main jet. A parametric study is curried out, taking into account the number of control jets, their orientation, and the mass flow injected. The deformation of the, main jet is analyzed from velocity and temperature fields. A particular configuration is detailed, in terms of turbulence, by using four hot wires probe measurements.
Application of linear and nonlinear adaptive filters for the compensation of disturbances in the laminar boundary layer
Authors: Evert F. , Ronneberger D. , Grosche‐R F. 
Published: March 2011

AbstractIn order to delay the laminar‐turbulent transition in the boundary layer of airfoils the compensation of instability waves by artificially excited disturbances is studied. It turns out that also nonlinear processes occur in the spatial development of disturbances. This can be modeled by different types of nonlinear filter structures.
Trailing‐edge separation control on an aerofoil in low‐speed flow
Authors: Siller H. A. , Fernholz H. H. 
Published: March 2011

AbstractLow‐speed wind‐tunnel experiments have been performed with a laminar aerofoil. Loudspeakers mounted inside the wing generate an oscillating cross‐flow through a spanwise slot in the upper surface of the aerofoil. The interaction of the oscillating flow with the flow over the aerofoil generates spanwise vortices. They enhance mixing and thereby add momentum to the region near the wall, so that boundary layer separation can be delayed, or a separated flow can be forced to reattach. The experimental results show that the maximum angle of attack of the aerofoil can be increased and lift forces can be enhanced by 10%.
Reduction of the On‐line Measurement and Control Expenses by Adaptive Stochastic Path Planning
Authors: Marti K. , Aurnhammer A. 
Published: March 2011

AbstractIn the optimal control of dynamic systems, e.g., in the control of industrial or service robots, the standard procedure is to determine first off‐line an optimal open loop control, and correct then the inevitable deviation of the trajectory or performance of the system from the prescribed values by on‐line measurement and control actions which may be very expensive. By adaptive stochastic path planning and control (ASPPC), i.e. by incorporating the available a priori and statistical information on the unknown model parameters of the dynamic system and its working environment into the off‐line and on‐line control process by means of stochastic optimization methods, the deviation between the actual and prescribed trajectory can be reduced to a large extent.
Modelling of light weight porous metal materials
Authors: Ehlers W. , Droste A. 
Published: March 2011

AbstractThe low density related to the high strength of the structure and the special features of metal foams make it possible to develop special components. To design the properties of such components, for example, the finite element method offers a cheap possibility for simulations. This requires the development of a model for foamed materials. In contrast to a microscopic approach, the Theory of Porous Media (TPM) allows a macroscopic continuum mechanical description for metal foams on the the basis of a real or a virtual homogenisation over the microstructure. In particular, a gas‐filled solid material is taken into consideration including finite elastic and finite elasto‐plastic constitutive equations for the solid matrix combined with convenient constitutive relations for the viscous pore‐fluid and the respective interaction mechanisms between the constituents.
Asymptotics for Strongly Nonlinear Dynamical Systems
Authors: Awrejcewicz J. , Andrianov I. V. 
Published: March 2011

AbstractStrongly nonlinear dynamical systems are analysed using a new asymptotic approach. Periodic oscillations of the systems with a polynomial nonlinearity are considered and a period of strong nonlinear oscillations of the mathematical pendulum is estimated analytically.
Random vibrations of the frame foundation
Authors: Bryja D. , Mironowicz W. 
Published: March 2011

AbstractThe foundation for the machine in the form of the flat frame made of thick bars is examined in the paper. The frame is modelled by FEM with the application of the original Timoshenko beam element. The machine is treated as the nondeformable block viscoelastically supported on the frame. The dynamic load is random and has the form of the periodic series of short duration shocks. The solution of the problem is presented in the correlation theory sphere, using the influence response function of the multi‐degree‐of‐freedom system.
Freiheitsgradreduktion bei Finite Element Modellen mit Hilfe der dynamischen Steifigkeit
Authors: Eichel Dirk , Waller Heinz 
Published: March 2011

AbstractFür ein mat der dynamischen Kondensation berechnetes Gleichungssystem
equation image
ward durch Abspaltung eines Teils der Eigenwerte von F(δ) eine Formulierung mit vom Grad minimalen Polynommatrazen angegeben.
Total strain energy density parameter for fatigue analysis
Authors: Golos K. M. 
Published: March 2011

AbstractIn the paper a new damage parameter‐total strain energy density for fatigue analysis has been examined. The parameter can be applied to both Masing and non‐Masing material description. The relationships of the proposed damage parameters for both types of material description have been shown. The parameter has been applied to fatigue experimental data for carbon steel St5, A516 steel and titanium alloy W13–1. Comparison has shown to be in good agreement.
Application of a New Regularization Technique to Localized Failure
Authors: Lambrecht M. , Miehe C. 
Published: March 2011

AbstractThe simulation of localized failure, e.g. in the form of shear bands, yields the typical mesh‐dependent post critical results within standard finite element formulations. We here propose a new regularization technique based on a micromechanically motivated approach which overcomes this problem. The key idea here is the introduction of a micro‐structure at a typical Gauss‐point of the finite element mesh which befits in the form of an assumed fluctuation field when macroscopic localization occurs. A regularization effect is obtained when the size of the micro‐structure is scaled to the volume associated with a Gauss‐point of the finite element mesh.
Improvements for finite‐element implementation of the Gurson Model
Authors: Mahnken R. 
Published: March 2011

AbstractIn this contribution three modifications for the plastic potential of the Gurson model are proposed, which give, from the numerical point of view, some improvements for the finite‐element implementation. Firsty a linear representation is used, which shows superior convergence property in the local iteration procedure compared to the original quadratic representation. Furthermore the cosh‐function appearing in the original formulation is replaced by a modified Cosh‐function, thus avoiding the overflow effect in the local iteration procedure for in‐between values. Additionally a smoothing technique is applied to the modified void volume function f*]f[ introduced by Tvergaare & Needleman ]3[. A numerical example illustrates the advantage of the proposed approach.
Non‐local Strength Conditions Based on Generalized δc Cohesive Models
Authors: Mikhailov S. E. 
Published: March 2011

AbstractGeneralization of the Leonov‐Panasyuk‐Dugdale δc cohesive model applicable not only for cocks tips but also for any internal or boundary point is described. These models are interpreted also as non‐local strength conditions and can be used for description of strength small scale effects, for stress fields with stress singularities other than the usual crack tip square root singularity (e.g. for corner points), for bodies with smooth and singular stress concentrators.
Remeshing Techniques and Data Transfer in the Adaptive FEM
Authors: Ehlers W. , Ellsiepen P. , Ammann M. 
Published: March 2011

AbstractA major problem in using the finite element method (FEM) for solving numerous engineering problems is the assessment of discretisation errors and the design of a suitable mesh. To overcome this problem, adaptive finite element methods have been developed. In this paper, we illustrate a general h‐adaptive procedure and we present a comparison of the performance of three different density functions.
Elastically deformable mechanisms
Authors: Franitza D. , Landgraf G. , Modler‐H. K. 
Published: March 2011

AbstractA large number of applications in engineering of mechanisms are geometrically non‐linear. A theory which deals with a rate‐field‐problem using the transfer matrix procedure based on macro elements is them fore developed. Velocities in connection with the integration procedure according to Runge‐Kutta 4‐th order for state variables of a prismatic beam are calculated. Element crossings were included and sliding joints were considered.
Finite Element Analysis of Piezothermoelastic Smart Structures
Authors: Andreas Görnandt , Ulrich Gabbert 
Published: March 2011

AbstractIn many applications of piezoelectrically controlled smart structures, the functionality of the system has to be guaranteed in extremely hot and cold thermal environments. Consequently, the thermal effect is very important and must be taken into account in the design process of such structures. This results in a fully coupled formulation of piezothermoelastic material behaviour. Based on a weak formulation of the equilibrium conditions and the coupled constitutive equations of this three field problem a general finite element concept is presented. Static as well as dynamic responses of combined thermal, electric and mechanical excitations are considered. An iterative solution strategy is proposed to solve the coupled field problem in an effective way.
Dynamics of shear frames with tuned liquid column dampers
Authors: Hochrainer M. J. , Adam C. 
Published: March 2011

AbstractTuned liquid column dampers (TLCD) are passive energy absorbing devices to control vibrations of buildings placed e.g. in an earthquake environment. The objective of this paper is the study of the influence of TLCD on the response of shear frames. For the analysis the TLCD are modeled as SDOF oscillators. For the linear system an analytical optimisation is given, bared on a decomposition into substructure modes of the shear frame. To determine the quality of the analytical solution a numerical optimisation is performed The results indicate a good agreement between the outcome of both optimization methods and indicate as well that TLCD reduce the response of earthquake excited buildings quite effectively.
On the theory of fourth‐order tensors and their application in large strain elasticity
Authors: Itskov M. , Basar Y. 
Published: March 2011

AbstractThis paper briefly presents some important aspects of the theory of fourth‐order tensors proposed in ]I[. The theory involves an operation algebra, differentiation rules, eigenvalue problems, an application to isotropic tensor functions and some other relevant problems. A most important application field the theory finds in large strain elasticity, where fourth‐order tensors appear as elastic moduli.
Simulation of Sheet Metal Forming on the Basis of the Deformation Theory and Optimization Techniques
Authors: John R. , Ulbricht V. , Brummund J. 
Published: March 2011

AbstractThe basic approach for the simulation of the sheet metal forming in this paper is a reduction of the whole process to a mapping between the undeformed and the deformed configuration. One major aim consists in a fast code that can be used in the design stage of a workpiece. The approach has to permit first statements to the producibility of the workpiece. Since the configurations are given, the central question raises is the placement of a material points in the deformed configuration. In this approximation the necessary consideration of plastic material behaviour is possible only on the basis of the deformation theory of plasticity. The present paper is restricted, for simplicity, to the membrane stress state in the shell and to isotropic material behaviour.
On local error estimators for non—self‐adjoint boundary value problems
Authors: Steeb Holger , Cirak Fehmi , Ramm Ekkehard 
Published: March 2011

AbstractThe study focuses on an adaptive finite element method for the stationary convection‐diffusion problem with dominant convection. A short review of the standard and stabilised finite element method will be given. The adaptivity scheme is based on an a posteriori error estimator for local quantities. In this error estimation strategy for a non‐self‐adjoint boundary value problem we introduce duality techniques or in engineering words we use an influence function related to the reciprocal theorem of Betti & Mmaxwell to estimate the local errors. With this type of error estimator, the pollution effect in the domain Ω caused by shock fronts or boundary layers could be captured.
Transient free surface flows via a stabilized ALE finite element method
Authors: Schmidt J. , Wall W. A. , Ramm E. 
Published: March 2011

AbstractFree surface problems appear in a wide range of industrial and engineering applications, e.g. when modeling sloshing of fluid in a container or when tracking the free surface evolution in casting and molding processes. A finite element technique is presented to study time‐dependent large free surface motions of viscous, incompressible fluids. The approach is based upon an arbitrary Lagrangean‐Eulerian (ALE) representation of kinematics and field equations, i.e. continuum mechanical conservation laws. Both convective effects and equal‐order interpolation for velocities and pressure are stabilized in a Galerkin least‐squares sense. This leads to a fully stabilized finite element method (FEM) for the governing instationary incompressible Navier‐Stokes equations. The algorithmic setup is complemented by a combination of the stabilized FEM with direct time integration procedures and fixed point‐like iterative schemes. The performance of the overall algorithm is demonstrated with the help of selected two‐dimensional numerical examples.
Adaptive Mixed Finite Element Method for Reissner‐Mindlin Plates
Authors: Kerstin Weinberg , Carsten Carstensen 
Published: March 2011

AbstractWe use a modified mixed finite element method for the Reissner‐Mindlin plate model to study its numerical properties in practical use. We derive an a posteriori error estimate to control adaptive mesh‐refining algorithms and study the question of reliability. Numerical examples prove the new scheme efficient.
Transient Resonance Oscillations of a Turbine Blade with regard to Non‐Linear Damping Effects
Authors: Irretier H. , Balaschov D. 
Published: March 2011

AbstractTransient, forced vibrations of a turbine blade are modelled. Dissipative effects such as material damping, aerodynamic damping and damping at interfaces are taken into account. For the modelling of these effects the set of isolated weakly non‐linear single degree of freedom oscillators with slowly varying natural frequencies and small non‐linear damping is used. The non‐linear damping law considers as a sum of elementary power functions with respect to the modal velocity. The Krylov‐Bogoljubov asymptotic method is applied for the investigation of the transient resonance response which is induced by the sweep of the excitation frequency through the system natural frequency during run‐up or run‐down. Numerical calculations are provided to demonstrate the validity of the first asymptotic approximation.
Hopf Bifurcation Generated by Small Nonlinear Terms
Authors: Krasnosel'skii A. , Mennicken R. , Rachinskii D. 
Published: March 2011

AbstractWe study the problem of generation of small cycles from the equilibrium in autonomous quasilinear systems depending on a parameter. In contrast to the usual situations, the linearized equation is degenerate for all parameter values (not only for the bifurcation point). Therefore the existence of small cycles is determined by small nonlinear terms. The main example is an equation where the principal degenerate linear part is independent of the parameter. We suggest sufficient conditions for the existence and stability of small cycles for higher‐order scalar equations. The results are based on topological methods and methods of monotone operators.
Comfort and Stability of Vehicles with Stochastic Excitation
Authors: Mehl V. , Pfister F. 
Published: March 2011

AbstractAn efficient method to determine comfort and road holding stability of vehicles is discussed. By using the frequency spectrum of the vertical excitation, modeling of a stochastic road becomes superfluous. In the case of a linearized model, the frequency response yields the acceleration of the chassis and the dynamic wheel forces. They are used as measures for comfort and stability, if applied to the spectrum of the road excitation. In order to include buffer effects with nonlinear characteristics, an approximation method is discussed to determine the equivalent stiffness coefficient of a, linear spring.
Nichtlineare Oberflächenmodelle der Bremsscheibendynamik
Authors: Schmalfuss C. , Wedig W. , Ams A. 
Published: March 2011

AbstractDie KFZ‐Bremse wird als lineares, zeitvariantes Modell mit nur einem Freiheitsgrad und nichtlinearer Bremsscheibenoberflächen‐Formulierung betrachtet. Besondere Aufmerksamkeit wird den Richtungsänderungen der Normal‐und Reibungskräfte bei variablen Oberflächen gewidmet. Ein typischer Effekt ist die Instabilität des Systems Bremsscheibe‐Bremssattel, welche zu Bereichen kritischer Fahrgeschwindigkeiten führt. Untersucht werden stationäre, harmonische und stochastische Anregungen durch Taumelfehler bzw. Oberflächenrauhigkeiten der Bremsscheibe. Der Einfluß dieser Bauungenauigkeiten wird in Stabilitätskarten aufgezeigt.
Distributed Piezoelectric Vibration Absorbers
Authors: Tylikowski A. 
Published: March 2011

AbstractIn the paper the idea of passive vibration absorbers with variable stiffness or damping properties is extended by developing a tunable distributed piezoelectric vibration absorber of transverse vibrations of a circular plate. The problem of steady‐state vibration transmission through an aluminum plate placed in a duct is analysed. The frequency and space characteristics of transverse displacement and velocity in the plate for the open and short external circuits are presented.
Oscillatory Stochastic Systems with Nonlinear Dissipations
Authors: Wedig V. Walter. , Wagner Utz Von. 
Published: March 2011

AbstractAs an example for oscillators with nonlinear dissipation, we consider a piecewise linear and asymmetric damping characteristic which is typical for shock absorbers in wheel suspensions. For white noise excitations, associated Fokker‐Planck solutions are approximated assuming that displacements and velocities of oscillators are independent. To get even better approximations, analytical results of the expected values of the system are taken into consideration. Then, these stationary density approximations are applied to derive adapted orthogonal polynomials by which the stationary probability density is expanded. The analytical results obtained are checked by corresponding Monte‐Carlo simulations.
Nonlinear feedback control for a four‐steering‐wheel mobile robot
Authors: Blaimschein P. , Bremer H. 
Published: March 2011

AbstractA mobile robot with four steered and driven wheels moving on planar surfaces under nonholonmic constraints is considered. For this system the equation of motion is derived, which can be reduced to a model of a two‐steering‐wheel vehicle under certain assumptions. For reduced state‐space model a nonlinear state‐space transformation and a nonlinear input transformation is derived so that the model becomes exactly linearized. Additionally to the exact state‐space linearization, the systems for the two positions in the plane and the orientation of the mobile robot are decoupled. These three linear and noninteracting systems can then easily be stabilized by linear control theory.