bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Stochastic Approach for Helicopter Handling Qualities Assessment in Turbulence
Authors: Perhinschi M. G. 
Published: March 2011

AbstractA general procedure for analysis of helicopter handling qualities in turbulent atmosphere is formulated based on a linear model of the vehicle, on a simple representation of the turbulence field and on a mathematical model of the human pilot for quantitative evaluations. The approach leads to a linear system with part of the input random. Results from the theory of linear systems with random input, as well as simulation, can be used to predict helicopter handling qualities in turbulence.
Application of the J2 Plastic Flow Theory in Stability Analysis of an Elastic‐Plastic Open Sandwich Cylindrical Shell under Shear Forces and External Pressure
Authors: Jerzy Zielnica 
Published: March 2011

AbstractThe paper deals with linear and nonlinear stability analysis of a free‐supported sandwich cylindrical panel loaded by shear forces and external pressure. The faces of the shell are assumed to be made of an isotropic, compressible material with stress hardening and these are of the same thickness. The core, of the lightweight type, resists transversal forces only. The constitutive relations of the J2 plastic flow theory are assumed in the analysis. Stability equations are derived on the basis of strain energy approach. With the use of Shanley concept the problem is reduced to a set of partial differential equations with the following unknown functions: stress function F, displacement function Ψ and deflection function w. In nonlinear approach the two parametrical deflection function is accepted in the solution and the equilibrium equation is solved by Galerkin method. Finally, a nonlinear stability equation is obtained which makes possible to determine the equilibrium paths and critical loads for the considered shell. Numerical calculations are performed by a special iterative procedure.
Mode Expansion of Viscous and Viscoelastic Taylor‐Couette Flow in Finite Gaps
Authors: Berger Hans‐Reinhard 
Published: March 2011

AbstractThe Taylor‐Couette flow of viscous and viscoelastic second‐order fluids is examined by a low‐dimensional truncated expansion of trigonometric functions. Tie influence of gap width between the cylinders is included up to second order. By comparing the results for the critical Taylor number, obtained from the series expansion, with numerical results from linear stability calculation the truncation is validated with an error of less than two percent.The dynamics of the truncated system of ordinary differential equations describe well the transition from laminar to Taylor‐vortex flow, but no further bifurcations to more complex flows are found. The reason for this behaviour is assumed to be due to the omission of non‐axisymmetric disturbances.
Sensitivity analysis of the human body mechanical model
Authors: Ciglaric I. , Prebil I. 
Published: March 2011

AbstractThe mechanical model of human body is introduced. Model consists of rigid segments connected with joints. Articulated rigid‐multibody model is used as a tool for investigation of the injury mechanism during the car crush event. The sensitivity analysis of proposed mechanical model of human body is discussed. Modified direct approach to the sensitivity analysis is introduced, which enables calculation of the sensitivity coefficients in a straightforward way. The approach is semi‐analytical and is baaed on symbolic derivatives of the differential equations of motion. The results of a case study are presented. They illustrate the intrisinct effect of human body geometry and other influential parameters on head acceleration. It is shown that the sensitivity analysis allows for a deeper insight into human body injury criteria.
Mehrkriterienoptimierung bei der globalen Bahnplanung für elastische Handhabungssysteme
Authors: Frik M. , Markus B. 
Published: March 2011

AbstractBei der globalen Bahnplanung für elastische, kinematisch redundante Handhabungssysteme können wahlweise mehrere Randbedingungen, Optimierungskriterien und Suchstrategien (A*, Dijkstra) vorgegeben werden. Alle Lösungen sind bei gleichzeitiger Optimierung von mehreren Kriterien nach dem Konzept der Skalarisierung Edgeworth‐Pareto‐optimal. Ein Planungsbeispiel zeigt, welches Optimierungapotential, gemessen an den Einzelkriterien, vorhanden sein kann. Die Methode der gewichteten Kriterien und die Dietanzmethode werden angewendet.
Some Comparisions of Least‐square and Chebyshev Approximation Techniques Applied for Synthesis of Straight‐Line Generating Mechanisms
Authors: Ibrayev S. M. 
Published: March 2011

AbstractThe experience on the application of least‐square and Chebyshev approximation (LSA and CA) based techniques for synthesis of path generating mechanisms examplified by Chebyshev's “ljambda‐mechanism” is summarized in this article.
Virtuelle Montage von Mechanismen
Authors: Kübler R. , Schiehlen W. 
Published: March 2011

AbstractMechanismen sind durch geschlossene kinematische Schleifen gekennzeichnet. Bei ihrer Montage werden häufig vorgefertigte Baugruppen von verschiedenen Herstellern verwendet. In zunehmendem Maße liefern die einzelnen Hersteller nicht nur die Hardware, sondern auch die Software, so daß die Möglichkeit einer virtuellen Montage des Gesamtproduktes während der Entwicklungsphase entsteht. Die Kopplung verschiedener Simulationsprogramme kann jedoch zu numerischen Instabilitäten führen. In diesem Beitrag wird die Stabilisierung gekoppelter Simulatoren auf Mehrkörper‐systeme mit kinematischen Schleifen angewandt. Als Beispiel dient die Radaufhängung eines Automobils mit einer Doppelquerlenkerachse.
Modellbasierte Positions‐ und Kraftregelung eines Schreitfahrwerks
Authors: Schneider M. , Müller J. 
Published: March 2011

AbstractFür das Schreitfahrwerk ALDURO wird ein nichtlineares Regelungskonzept auf der Basis einer exakten Ein‐/Ausgangslinearisierung vorgestellt. Aufgrund des modellbasierten Ansatzes unter Verwendung der nichtlinearen kinematischen und dynamischen Gleichungen können alle auftretenden Nichtlinearitäten kompensiert werden.
Stochastic Transient Resonance of a Plate Under Rotating Machine
Authors: Sniady P. , Sieniawska R. , Zukowski S. 
Published: March 2011

AbstractAn approach for obtaining the probabilistic characteristics of the plate response due to the excitation caused by rotating machine standing on it is presented. Some method for solving the problem of transient resonance applying the Ito differential formula and a set of Ito type differential equations is proposed.
Konzept zur Bestimmung makroskopischer Moduli von Verbundmaterialien
Authors: Bayreuther C. , Miehe C. , Schröder J. 
Published: March 2011

AbstractDie Berechnung makroskopischer Moduli ist ein wesentliches Ziel bei der makroskopischen Beschreibung von Verbundmaterialien mit linear elastischem Materialverhalten. Zunächst werden Grundlagen zur Konstruktion analytischer Schätzer für makroskopische Moduli aufgezeigt und ein neues verzerrungsbasiertes nNon‐Dilute Distribution Model” vorgestellt. Anschließend wird basierend auf einer Diskretisierung der Fluktuationen des Verschiebungsfeldes auf der Mikrostruktur eine geschlossene Darstellung der makroskopischen Moduli für beliebige Mikrostrukturen hergeleitet.
Buckling of Shear Loading Plates with Strengthenings
Authors: Kosel Franc , Petrišič Jože 
Published: March 2011

AbstractThe paper treats the influence of either weakening or strengthening of rectangular plates on the critical external buckling load. The plate geometry was chosen so that the buckling process takes place in the elastic range. The simply supported plate is loaded with shear forces per unit length which act on its edges. The results present the buckling coefficient as a junction of the ratio between the thickness of the weakening or strengthening and the initial plate. The buckling coefficient is analyzed as a function of the ratio between the weight of the weakened or strengthened plate and the initial plate weight without weakening or strengthening too.
A General Refined Plate Theory
Authors: Johannes Meenen , Holm Altenbach 
Published: March 2011

AbstractStarting from the principle of virtual displacements, a plate theory is formulated which includes most classical and refined plate theories as special cases. The force and moment equilibrium and the correct formulation of the boundary conditions is obtained by introducing a certain virtual displacement field, and it w shown that generalized Kirchhoff edge forces are present in some types of higher‐order theories.
A Constitutive Law for Anisotropic Stress Adaptive Bone Remodeling
Authors: Nackenhorst U. , Krstin N. , Lammering R. 
Published: March 2011

AbstractA constitutive theory for stress adaptive bone remodeling based on energetic and thermodynamic considerations is presented. The constitutive theory leads to important conclusions about unknown model parameters, such as the relationship between the bone density and the Young modulus of bones tissue. The isotropic theory is extended to anisotropy by use of a fabric tensor description and a strategy for the numerical computation of anisotropic bone remodeling is suggested.
Transmission problem for viscoelastic aging
Authors: Julia Orlik 
Published: March 2011

AbstractA multi‐phase composite with jumps on the interface is analyzed. The composite components are aging linear viscoelastic (described by the integral Volterra operator of non‐convolution type) and are subjected to isotropic shrinkage (or thermoelastic deformation). First, the theory of Volterra operators is extended to the Bochner‐ Volterra integral operators. Then these results are used to prove existence and uniqueness of the weak solution to the general transmission problem of viscoelasticity with mixed boundary conditions in the class of continuous Sobolev‐valued functions.
Crossover in the dynamics of jerky flow in AlMg polycrystals
Authors: Ananthakrishna G. , Brechet Y. , Fressengeas C. , Kubin L. P. , Lebyodkin M. 
Published: March 2011

AbstractJerky flow in A1‐Mg alloys is investigated through the statistics of the stress drops size, and through a dynamic analysis of the stress vs. time records. At low applied strain rate levels, peaked distributions are associated with chaotic dynamics, while at higher strain rates, the unstable behavior is characterized by power law distributions reminiscent of a critical dynamics. In addition, the bands of localized plastic deformation shift from stationary to propagating. This crossover is discussed in terms of a nonlocal model of jerky flow, with a range of negative strain rate sensitivity and spatial interactions of varying strength.
On microstructures occuring in a model of finite‐strain elastoplasticity involving a single slip—system
Authors: Carstensen C. , Hackl K. 
Published: March 2011

AbstractStarting from a novel variational principle the flow theory of elastoplasticity can be formulated as a minimization problem with respect to the total deformation and the update of the plastic deformation gradient. For a specific model involving a single slip‐system the latter quantity can be eliminated. The resulting minimization problem with respect to the total deformation only turns out to be not quasiconvex, thus giving rise to the occurrence of layered microstructures. Finite element calculations indeed show these layers. The results are, however, mesh‐dependent. To overcome this effect a partial rank one convexification of the potential given is performed.
Determination of Mechanical Parameters of Solder Materials using the Miniature Measuring Method “Small Punch Test” and an Appropriate FE‐Simulation
Authors: Hemann K. P. , Müller W. H. , Nguyen V. S. 
Published: March 2011

AbstractIn order to model the aging of SMT (Surface Mount Technology) solder materials, which is a prerequisite for lifetime predictions of microelectronic joints as well as of the microelectronic package as a whole, it is necessary to know the current mechanical parameters of the solder as accurately as possible.In fact, the material behavior of solders is strongly affected by a repeated change of the temperature and the associated thermal loads. Consequently, the current, i.e., “remaining” properties of in‐service solders are of special interest. SMT applications use only very small amounts of solder. Therefore, the Small Punch Test (SPT) can preferably be used to secure materials data. The SPT is essentially a miniature version of a deep‐drawing test during which a load‐deflection curve is obtained. In combination with an FE‐simulation the uniaxial stress‐strain behavior and the fracture toughness of the solder material can be determined. It seems worth pointing out that by virtue of this methodology use of standard size specimens, which are not always available, is avoided a priori.
Micro‐mechanical Modelling of a Bi‐crystal Lamellar Composite's Behaviour at Large strain: A Double Scaled Transition Method
Authors: Krummeich R. , Sabar H. 
Published: March 2011

AbstractNanoscaled lamellar structures involve complex deformation behaviour at finite strain due to the preserve of a large number of interfaces. The aim of the work is to develop a micromechanical approach based on interfacial operators in the context of statistical continuum mechanics. Using Hill's formalism, constitutive equations at mesoscale (1 μm) are derived from Nemat‐Nasser's finite elastic‐plastic deformation model ]3,5[ and solved numerically by a self‐consistent method ]1[. At micro‐scale (O.1 μm), a thermodynamical process may be defined to describe intrinsic hardening mechanism found to be linearly dependent with the interlamellar spacing's inverse ]4[. Specific crystal plasticity of both phases may then be introduced in the micromechanical approach to obtain a double scale model describing global and local behaviour of a pearlitic ilot under an imposed loading.
Upper‐Bound Solutions for Rock Slope Stability
Authors: Megueddem M. , Siad L. , Zeghloul A. 
Published: March 2011

AbstractThis communication deals with the stability analysis of jointed rock slope under its own weight. The rock mass is crossed by two sets of unfilled joints. The stability analysis is based on the upper‐bound kinematic approach of the yield design theory. It is carried out directly by considering failure surfaces along particular joints and also going through the intact rock. The simple failure mechanism considered yields improvement of known results.
Plastic design of porous elements with statically admissible stress fields
Authors: Mostowski R. , Mieliczuk J. , Dudziak M. 
Published: March 2011

AbstractPlastic extremum principle (lower bound) of the plasticity theory for porous materials may be wed for effective design of complex shape elements. Basing on properties of earlier determined systems of discontinuity lines the method of statically admissible stress fields was assumed. The method may be usefully employed in engineering practice for plastic design of porous elements.
Simulation des elasto‐plastischen Verhaltens dünner Metallschichten
Authors: Schotte J. , Miehe C. , Schröder J. 
Published: March 2011

AbstractBei der numerischen Berechnung von plastischen Deformationen in dünnen Metallfilmen auf Substratträgern, wie sie beispielsweise in der Mikroelektronik in Form von Kupfer‐Leitungsbahnen eine entscheidende Rolle spielen, sind verschiedene Größeneffekte zu berücksichtigen. Hierzu sind aufgrund der speziellen geometrischen Eigenschaften (z. B. Korndurchmesser, Filmdicke) solcher Schichten weitreichende Modifikationen der bekannten Material‐ und Verfestigungsmodelle für Massiv‐Materialien erforderlich. Es werden verschiedene mikromechanisch motivierte Ansätze miteinander kombiniert und die durchgeführten FE‐Simulationen experimentellen Untersuchungen gegenübergestellt.
Strange—Mode Instabilities in Luminous Stars
Authors: Chernigovski S. , Glatzel W. , Fricke K. J. 
Published: March 2011

AbstractIf radiation pressure contributes significantly to the total pressure in models for the envelopes of hot and luminous stars, such as massive objects and Wolf—Rayet stars, strange—mode instabilities with growth rates in the dynamical range do occur. The properties of these mechanical instabilities are reviewed and an intuitive model of the underlying instability mechanism is discussed. Adopting spherical geometry the evolution of the instabilities has been followed into the nonlinear regime by numerical simulation. Multiple shocks are formed and velocity amplitudes above 102 km/sec are reached which can imply direct mass loss of the objects.
Comparison of Several Numerical Methods for Internal Transonic Flow Problems
Authors: Dobeš J. , Fořt J. , Fürst J. , Halama J. , Kozel K. 
Published: March 2011

AbstractThis contribution summarizes results of several numerical methods developed at our department. Presented methods are based on central TVD schemes, upwind TVD schemes with or without Riemann solver, ENO schemes and Lax‐Wendroff type schemes. The results of 2D methods, computed on either structured quadrilateral grids or unstructured grids composed of triangles and quadrilaterals, are compared on 2D axial and radial turbine cascade and 2D axial compressor cascade. A comparison of results, obtained on structured hexahedral grids, is shown for 3D axial turbine cascade of Škoda Pilsen enterprise.
A Field‐Panel Method For Subsonic And Transonic 3D Wing Calculation
Authors: Fokin D. , Wagner S. 
Published: March 2011

AbstractThe development of fast numerical methods for calculating sub‐and transonic flow over 3D configurations is important for numerical optimization purposes. One efficient approach, namely field panel method, is based on the boundary‐element methods solving the full potential equation (see e.g. ]1[). The algorithm incorporates panel methods for calculating the basic incompressible flow and compressible field iterations. The purpose of the present work is to develop a mathematically well based and efficient numerical field‐panel method for the analysis of transonic flow over 3D wings, that could be further used for design and optimisation of transonic wings in a given range of free stream Mach numbers.
Low‐Dimensional Approximations of Random Vibration Systems
Authors: Wunderlich R. , Vom Scheidt J. , Starkloff H.‐J. 
Published: March 2011

AbstractThe paper considers the computation of moment functions of the response of large‐scale randomly excited vibration systems. Since standard methods fail because of enormous computational problems dimension reduction techniques are applied. We find approximations of the desired response characteristics of the large‐scale system by solving a suitable reduced‐order system.
Spatial Friction as Standard NLCP
Authors: Glocker Christoph 
Published: March 2011

AbstractCoulomb friction problems can be stated as quasi‐variational inequalities. These are variational expressions of certain non‐smooth pseudo‐potentials which have to be minimized in the sense of a two‐person non‐cooperative constrained game, consisting of the normal and the tangential player. In this paper we show that spatial Coulomb friction applied to the rolling contact problem in rigid body dynamics may be formulated as a nonlinear complementarity problem in standard form, i.e. as 0 ≤ x f(x) ≥ 0 with continuous and differentiable x → f(x).
Weight‐Minimal Laminate Structures Under Stress Constraints
Authors: Hansel W. , Becker W. 
Published: March 2011

AbstractThe determination of weight‐minimal laminate structures requires the well‐aimed employment of structural optimization. In contrast to the common parameter optimization in which the design variables fiber orientation and layer thickness are varied continuously, a layerwise topology optimization offers more flexibility. Starting from an initial laminate lay‐up with sufficient strength, the topology of each individual ply is varied by removing unnecessary material. The final design is well adapted to the local load fluxes.
Optimal Rendezvous with Constraints on Circular and Elliptical Orbits
Authors: Istratie V. 
Published: March 2011

AbstractThis work studies the optimum rendezvous with minimum fuel consumption two space vehicles on circular and elliptical orbits, the surveyor vehicle being equipped with a low thrust installation, their motion equations being written in the three‐dimensional space, in relative motion; the space origin being the target vehicle. Optimal controls to be determined being the acceleration due to thrust, related to the minimum fuel consumption. By means of the Legendre‐Clebsch condition it is demonstrated that the formulated optimization problem is, indeed, a minimum problem.
An efficient shape parameterization concept for structural optimization
Authors: Kegl M. 
Published: March 2011

AbstractThis paper describes a shape parameterization concept that may be used efficiently in structural shape optimization. It relies on the assumption that the finite element mesh is defined as a convective mesh, following automatically the shape changes of a conveniently parameterized body. Suitable parameterization of the body is achieved by combining the design element technique and a convenient design element. The design element in turn is defined as a rational (tensor‐product) Bézier body. It represents a general‐purpose design element, serving as the geometrical data provider for the response and sensitivity analysis for virtually any finite element type.
Structural optimization in nonlinear mechanics
Authors: Schwarz St. , Kemmler R. , Ramm E. 
Published: March 2011

AbstractIn the present study geometrically and materially nonlinear response is considered in topology and shape optimization in order to introduce more realism into the structural design. Typical objectives are to minimize the weight or to maximize the structural ductility or the critical load factor of a construction. The crucial point of the optimization procedure is the sensitivity analysis. In case of path‐dependent problems, such as elastoplasticity the sensitivities are also path‐dependent and have to be determined after each incremental step. With respect to the specific features of either topology or shape optimization different methods of sensitivity analysis are applied. The entire optimization procedure is verified by several design problems.
On a numerical method for the regularization of descriptor systems
Authors: Benner P. 
Published: March 2011

AbstractWe discuss a numerically stable algorithm, originally proposed in ]3[, that computes a regularizing output feedback for descriptor systems. In ]3[, the system is transformed to a condensed form via a sequence of singular value decompositions (SVDs). We show that the expensive SVDs can be replaced by reliable, more efficient orthogonal decompositions. Moreover, we demonstrate how the feedback is obtained from our slightly different condensed form.
Enge Schranken für den Effektivzinssatz nach der PAngV bei einem Annuitätenproblem
Authors: Detmers F. , Herzberger J. 
Published: March 2011

AbstractEin spezielles Problem stellt die Ermittlung des Effektivzinssatzes einer geänderten Annuität gegenüber der ursprünglichen Annuität dar. Daraus ergibt sich die Aufgabe, eine formelmäßige Abschätzung des Zusammenhangs zwischen den eindeutigen positiven Wurzeln zweier zugeordneter Polynome zu finden. In unserem Modell wird diese Aufgabe bei Anwendung der deutschen Preisangabeverordnung (PAngV) mathematisch gelöst.
Multigrid Simulation of Electromagnetic Actuators
Authors: Schinnerl M. , Langer U. , Lerch R. 
Published: March 2011

AbstractA recently developed multigrid simulation scheme for coupled magneto‐mechanical systems is presented. This scheme allows the efficient calculation of 3D dynamic motions of elastic ferromagnetic materials in a magnetic field. The 3D mechanical problem is discretized with nodal elements and the 3D magnetic problem with edge elements. Both meshes may be chosen independently and therefore, they can be adapted to the physical requirements of the mechanical and magnetic field. By applying fast multigrid solution techniques, very short solution times can be achieved even for large scale 3D problems. Using the developed scheme the transient behavior of a solenoid valve is calculated.