bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modellierung der Pfahlrammung mit der Discrete Element Method
Authors: Heesen E. , Kreuzer E. 
Published: February 2009

AbstractBei der Pfahlinstallation wird der Eindringwiderstand aus dem Bruch– und Verformungsverhalten des umgebenden Bodens sowie der Kraftübertragung an der Grenzschicht von Pfahl zu Boden bestimmt. In der Grenzschicht zwischen Pfahl und Boden sind die Effekte von großen Verformungen, Scherbandbildung, Kornrotationen und Strukturänderungen besonders stark ausgeprägt, so dass in diesem Bereich eine Kontinuumsmodellierung an ihre Grenzen stößt, während hier die Stärken der Discrete Element Method (DEM) zum Tragen kommen. In der DEM werden Böden als Granulat betrachtet, das aus einem System einzelner Partikel besteht, die über Kontaktkräfte miteinander in Wechselwirkung stehen und sich gegeneinander verschieben können. In dem hier verwendeten zweidimensionalen Modell werden die Partikel als konvexe, unregelmäßige Polygone modelliert. Die DEM ist in der Lage, durch die Anwendung einfacher mechanischer Gesetze auf der Ebene der Kornkontakte das komplexe Bodenverhalten zu erfassen. Als Kontaktgesetz wird die Formulierung nach Tillemans und Herrmann [1] verwendet. Die Bewegungsgleichungen werden mit Hilfe des in der DEM üblichen Predictor–Corrector–Verfahrens fünfter Ordnung nach Gear ausgewertet, das für die Berechnung von kurz–reichweitigen Kräften mit steilen Gradienten besonders geeignet ist. Untersucht wird die Bodenmechanik im Nahfeld der Pfahlinstallation, das Fernfeld wird nicht modelliert. Es wird eine Randbedingung vorgestellt, die das Verhalten der Fernfelds adäquat wiedergibt. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical integration of differential‐algebraic equations with mixed holonomic and control constraints
Authors: Quasem Mahmud , Uhlar Stefan , Betsch Peter 
Published: February 2009

AbstractThe present work aims at the incorporation of control (or servo) constraints into finite–dimensional mechanical systems subject to holonomic constraints. In particular, we focus on underactuated systems, defined as systems in which the number of degrees of freedom exceeds the number of inputs. The corresponding equations of motion can be written in the form of differential–algebraic equations (DAEs) with a mixed set of holonomic and control constraints. Apart from closed–loop multibody systems, the present formulation accommodates the so–called rotationless formulation of multibody dynamics. To this end, we apply a specific projection method to the DAEs in terms of redundant coordinates. A similar projection approach has been previously developed in the framework of generalized coordinates by Blajer & Kołodziejczyk [1]. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Statistical investigation of the nonlinear dynamical behavior of offshore structures
Authors: Reimers Jürgen , Ellermann Katrin 
Published: February 2009

AbstractThe increasing amount of reports concerning damages of ships, structures and loss of cargo due to wave structure interaction demand the development of systems to predict critical situations in the offshore environment. Within the last years, research has been done to predict encounter with critical wave or wave groups such as “rogue waves” or the so–called “three sisters”. The aim of such research is to develop programs that predict dangerous incidents and possibly alert the crew in time. The dangers of such extreme wave situations are severe, but occurrence of them is rather rare. Additionally and more often, structures are endangered because of fluid–structure–interaction leading to critical dynamical system behaviour in a wave environment that shows no extreme wave heights. The severeness of these incidents then depends on the experience and correctness of decision concerning the evasive actions of the master and his crew. Taking nonlinear effects into account, the statistical investigation of structures in waves shows critical behaviour of ships and structures without the absolute necessity of heavy sea conditions or the occurrence of dangerous sea phenomena. This paper describes the development of a program that uses a Monte–Carlo–Simulation technique based on a common panel–method for the creation of added masses and added dampings to predict the behaviour of the structure in several wave conditions. It shows possible ways to prevent the occurrence using similar early warning systems to those in development for critical wavegroups. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Geometrically exact shells in a flexible multibody framework
Authors: Sänger Nicolas , Betsch Peter 
Published: February 2009

AbstractThe present work deals with the extension of contemporary finite element methods for nonlinear structural dynamics to the realm of flexible multibody dynamics. In particular, we aim at the incorporation of geometrically exact shell formulations into a multibody framework. Geometrically exact shell formulations are capable of dealing with finite deformation problems. In particular we focus on (i) a finite element discretization in space which inherits the frame–indifference of the nonlinear strain measures from the underlying continuous shell formulation, and (ii) a discretization in time which leads to an energy and momentum conserving scheme or an energy decaying variant thereof. In nonlinear structural dynamics energy–momentum schemes have proven to be well–suited for the stable numerical integration of large deformation problems.We show that semi–discrete formulations emanating from the finite element discretization of geometrically exact shell theories can be regarded as discrete mechanical systems subject to holonomic constraints. Accordingly, the corresponding equations of motion can be written as differential–algebraic equations (DAEs) with index three. In particular, this viewpoint fits perfectly well into the framework of a rotationless description of rigid bodies [1] and geometrically exact beams [2]. Thus the DAEs provide a uniform framework for flexible multibody systems. Moreover, the DAEs turn out to be beneficial to the design of energy–momentum schemes [3–5]. Indeed our shell formulation can be shown to be equivalent to the previous work by Simo & Tarnow [6]. The newly established DAE framework facilitates the use of geometrically exact shells in flexible multibody dynamics. Representative numerical examples will demonstrate the capability of the proposed methodology. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical integration of rigid body dynamics in terms of quaternions
Authors: Siebert Ralf , Betsch Peter 
Published: February 2009

AbstractUnit–quaternions (or Euler parameter) are known to be well–suited for the singularity–free parametrization of finite rotations. Despite of this advantage, unit quaternions were rarely used to formulate the equations of motion (exceptions are the works by Nikravesh [1] and Haug [2]). This might be related to the fact, that the unit–quaternions are redundant, which requires the use of algebraic constraints in the equations of motion. Nowadays robust energy consistent integrators are available for the numerical solution of these differential–algebraic equations (DAEs). In the present work a mechanical integrator for the quaternions will be derived. This will be done by a size–reduction from the director formulation of the equations of motion, which also has the form of DAEs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A uniform discretization approach to flexible multibody systems
Authors: Uhlar Stefan , Betsch Peter 
Published: February 2009

AbstractThe present contribution deals with a unified approach to the discretization of flexible multibody systems. We present a rotationless description of rigid body motions, augmented by the incorporation of additional rotational coordinates, as presented in [1,2]. Accordingly, the motion of rigid bodies is governed by differential–algebraic equations (DAEs) which are amenable to the design of energy–momentum conserving integration schemes. The comparatively large number of unknowns due to the presence of redundant coordinates and Lagrange multipliers can be reduced by applying specific reduction techniques, such as the discrete null space method [3].In nonlinear elastodynamics, conserving schemes have been under investigation for several years. Recent works [4,5] turn out to be especially well suited for accurate and robust long term simulations. The underlying finite element discretization in space makes possible the use of arbitrary constitutive laws.In essence, the present approach leads to a uniform algorithmic treatment of translations and rotations which turns out to be especially beneficial to the simulation of multibody systems. Moreover, the underlying DAE structure of the discrete equations of motion facilitates the straightforward connection of flexible and rigid components belonging to a specific multibody system. In addition to that, the design of conserving schemes can be accomplished easily. Representative numerical examples will demonstrate the advantageous behavior of the proposed uniform discretization approach to flexible multibody systems. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Decentralised Control Design of Lateral and Vertical Vehicle Dynamics using Passivity
Authors: Villegas Carlos , Corless Martin , Shorten Robert , Readman Mark , Solmaz Selim 
Published: February 2009

AbstractIn this paper, we present a novel methodology to design block–diagonal stable decentralised controllers based on the Kalman–Yakubovich–Popov lemma. The approach yields closed–loop systems that are robust with respect to parameter uncertainty and structural perturbations. We demonstrate the methodology by designing controllers for the lateral and vertical subsystems of a vehicle emulator; namely, a test vehicle that can mimic the behaviour of a wide range of vehicles. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Aufbau eines elastischen Mehrkörpermodells für die Flügelhinterkante von Transportflugzeugen
Authors: Winter Evelyn , Woernle Christoph , Heyden Thomas 
Published: February 2009

AbstractModerne Transportflugzeuge mit hohen Reisegeschwindigkeiten erfordern die Variation des Auftriebsbeiwerts mittels der Hochauftriebssysteme, um bei Start und Landung geringere Fluggeschwindigkeiten zu erzielen. Zu den Hochauftriebssystemen zählen die Vorflügel (Slats) an der Vorderkante und die Landeklappen (Flaps) an der Hinterkante des Flügels. Die modellierte Flügelhinterkante besteht aus zwei Landeklappen, welche auf insgesamt vier Tracks drehbar gelagert sind und durch Koppelgetriebe bewegt werden. Die äußere Landeklappe wird außerdem in einer Führungsschiene abgestützt. Der Antrieb erfolgt durch eine zentrale Antriebseinheit, ein Wellensystem und hoch untersetzende Getriebe. Die Landeklappen und einzelne Komponenten der Tracks werden flexibel als FE–Modell aufgebaut, da die eingeprägten Luftlasten zu signifikanten Verformungen führen. Die elastischen Körper werden in ein Mehrkörpermodell des Gesamtsystems implementiert, welches zusätzlich das als starr angenommene Wellensystem enthält. Die Luftlasten werden als Resultierende an der Klappenvorderkante aufgebracht, wobei der Versatz der Lastangriffspunkte durch Korrekturmomente berücksichtigt wird. Die Deformation des Flügels unter den Luftlasten wird als rheonome Bindung beschrieben. Hierdurch können Wechselwirkungen zwischen dem Landeklappensystem und den Flügelverformungen untersucht werden. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation der Dynamik des Vorflügelsystems von Transportflugzeugen mit Hilfe elastischer Mehrkörpermodelle
Authors: Zierath János , Woernle Christoph , Heyden Thomas 
Published: February 2009

AbstractBei Flugzeugen wird der Auftriebsbeiwert der Tragflächen in der Start– und Landephase durch Hochauftriebssysteme vergrößert, wodurch die Fluggeschwindigkeit reduziert werden kann. Zu den Hochauftriebssystemen zählen neben den Landeklappen (Flaps) auch die Vorflügel (Slats) an der Vorderkante des Flügels.Das Vorflügelsystem besteht aus mehreren Vorflügelkörpern, die jeweils durch mindestens zwei in Rollen gelagerte Bogensegmente geführt werden. Die Bogensegmente sind als gebogene Zahnstangen ausgeführt, in welche durch ein Wellensystem angetriebene Ritzel eingreifen. Das Antriebssystem umfasst eine zentrale Antriebseinheit, ein Wellensystem und hoch untersetzende Getriebe. Für die Simulation des dynamischen Verhaltens unter Luftlasten wird ein elastisches Mehrkörpermodell aufgebaut. Die Vorflügelkörper unterliegen größeren Deformationen und werden mit Hilfe der Methode der Finiten Elemente elastisch modelliert. Die Rollenführungen der Bogensegmente werden durch kinematische Ketten beschrieben. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Visualization of Patient Specific Arterial Geometries Using the Virtual Histology
Authors: Brands Dominik , Klawonn Axel , Rheinbach Oliver , Schröder Jörg 
Published: February 2009

AbstractThe simulation of a balloon–angioplasty (clinical treatment of atherosclerotically degenerated arteries) requires information of the anatomical and physiological composition of the arterial wall. The intravascular ultrasound and the interpretation by a virtual histology provide cross–sectional images of the diseased arterial walls where the different components are characterized by color–coding. Using these information and the reconstruction of the vessel path from biplane angiography the patient specific data are visualized and discretized. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effective parameters of cancellous bone
Authors: Ilic Sandra , Hackl Klaus , Gilbert Robert 
Published: February 2009

AbstractCancellous bone is a two–component structure consisting of the bone frame and interstitial blood marrow. In the scope of this presentation, the multiscale finite element method is used for its modeling. This method results from a combination of homogenization theory and the theory of finite elements and is based on the calculation of effective material parameters by investigating representative volume elements (RVEs). For the particular kind of material considered here, a cubic two–phase RVE is assumed where the dry skeleton is modeled in different ways. Apart from the variations of the geometry, the influence of the usage of different types of finite elements is studied in this context. Note that the presence of a liquid phase requires dynamic investigation including the viscous phenomena. To this end, acoustic excitation and an analysis in the complex domain are chosen. The method permits calculation of the effective material parameters such as Young's modulus, bulk modulus and Poisson's ratio and furthermore the simulation of the behaviour of the complete bone or of its parts. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Control and stability of the complex inverted pendulum models in application to postural sway analysis of the vertical human stance
Authors: Kizilova Natalya 
Published: February 2009

AbstractMechanism of balance control is investigated on computerized posturography data on the vertical two–legged and one–legged stances measured on healthy subjects and the patients with osteohondrosis and coxarthrosis. Oscillations of the center of mass over 30 s of keeping the quiet stance and the trajectories for a step forward off the force platform have been computed. It was shown that during the one–legged stance the balance control strategy includes ‘scanning’ of the larger area with bigger sway amplitudes in the vicinity of the stable state as compared to the two–legged stance. A generalized model of the body as a multi–link system is proposed. Mass and inertia of each body segment and torques in joints are taken into consideration. The calculated own and forced frequencies of the model correspond to the spectral analysis of the posturography data. One–legged stance is proposed as a proper test for revealing the balance disorders. It is shown that investigation of the oscillations and trajectories of the center of mass for the step forward off the force platform is perspective for medical diagnostics to distinguish between the spine and joint pathologies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite Element Modelling of Bioactive Contact in Bone‐Implant Interface
Authors: Lutz André , Nackenhorst Udo 
Published: February 2009

AbstractFinite element simulation for the prediction of bone remodelling caused by implants is a powerful method to improve or to rate implant designs even before they will be evaluated in clinical studies. But the bone–implant interaction is often modelled as ideal bonding in the interface. This approach is not suitable to describe the interrelation of both parts in a physiological manner. To correct these insufficiencies a 3D bioactive contact element has been developed. This contact element describes on the one hand the pure mechanical interaction and on the other hand the mechanical stimulated bone ingrowth in porous surfaces. The benefits of the use of the bioactive contact element regarding the standard method will be presented in this contribution. A comparison of both methods based on clinic results regarding a hip prosthesis with mixed surface textures will be shown. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An atomic interaction‐based rod formulation for modelling Gecko adhesion
Authors: Sauer Roger A. 
Published: February 2009

AbstractWe present a nonlinear rod model which describes the adhesion mechanism used by the Gecko to cling to inclined and overhanging surfaces. The rod formulation is used to model the fine, hair–like setae, which form the microstructure of the Gecko toes. A simple geometric representation, based on hyperbolas, is used to capture the branching of the seta. The adhesion between seta and surface is modelled by an atomic interaction potential. The seta model is cast into a nonlinear finite element framework, which is used to simulate and study the pull–off behavior of a single seta. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Methods and CFD Techniques for Drug Application in Brain Tumor Treatment
Authors: Shcherbinina Elena , Turek Stefan 
Published: February 2009

AbstractIn our work, the governing system of equations consists of a mass conservation equation, a momentum equation and an equation for the drug concentration in the brain tumor. This system describes the penetration of drugs into the brain tumor (there is a cavity after surgical removal of a cancer tumor), which fill up the cavity after a surgery. We use techniques of computational fluid dynamics (CFD) to get a solution of the derived partial differential equations (Navier–Stokes equation with additional scalar equations and force terms) and obtain a saddle point problem after discretization of the governing system of equations with finite elements such that we can use modern CFD tools and software like FEATFLOW to get numerical solutions of this problem. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanical modelling and experimental validation of meniscus replacement material
Authors: Stoffel Marcus , Weichert Dieter , Müller‐Rath Ralf 
Published: February 2009

AbstractIn the present study a condensed collagen gel is investigated for its application as a cartilage replacement material. For this reason, the strength and damping properties are examined experimentally and a theoretical model for predicting specimen deformations and stresses is proposed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Porous Media Model to Describe the Behaviour of Brain Tissue
Authors: Wagner Arndt , Ehlers Wolfgang 
Published: February 2009

AbstractThe human brain is a very sensitive organ. Even small changes in the cranium cavity can cause life–threatening effects. In case of medical intervention, biomechanics can assist the therapy decisions by simulating the physical behaviour of brain tissue, e.g., the coupled interaction of the fluid motion and the deformation of the brain tissue. In the context of the Theory of Porous Media (TPM), a convenient model of the brain is introduced, which is able to simulate essential mechanical effects in the porous structure of the brain material. The fluid–saturated brain can be treated as an immiscible binary mixture of constituents. In this macroscopic biphasic model, the mixture consists of a solid phase (brain tissue) and a fluid phase (interstitial fluid or blood plasma). Both constituents are assumed to be materially incompressible. The resulting set of coupled partial differential equations is then spatially discretised using mixed finite elements with a backward Euler time integration. Numerical examples are presented illustrating the fundamental effects on the brain tissue under heart–rate dependent pulsative pressure variations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A definition of eddy current penetration depth useful for flaw detection and conductivity measurement
Authors: Dziczkowski Leszek 
Published: February 2009

AbstractThe proposed definition of the penetration depth of eddy currents, more convenient for tests with defectometers, is based on the model: measuring coil placed above non–magnetic conductive foil. The designated penetration depth is equivalent to the penetration depth of a measuring device and is subject of practical observations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of silicon reinforcement on load‐capacity of porous nanofilters
Authors: Kovács Ádám , Kovács András 
Published: February 2009

AbstractSquare–form microfilters consisting of a two–layer porous membrane with nano–size pores and reinforced by silicon columns have been investigated. The change of layer thicknesses and reinforcement geometry modify the load–capacity of the device through the variation of strength properties. A simple thin plate model was constructed by substituting the effect of silicon columns by an equivalent third layer. Estimates for the load–capacity were made by finite element calculations. These estimates have been verified by experimental results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fracture and Damage Analysis of Crimped Glass Fibre Truss Type Elements
Authors: Kreikemeier Janko , Gabbert Ulrich 
Published: February 2009

AbstractThe paper deals with the damage behaviour of special glass fibre reinforced plastic truss type elements, called Polystal profiles, which are widely used as load bearing cables. To connect these profiles with other structural elements steelmade hulls are crimped onto the profiles. The challenge is to detect the optimal crimping ratio (CR) to realize maximum longitudinal loads in restraint systems. By using scanning electron microscopy (SEM) several damage states like fibre pullout and matrix cracking could be observed. To describe the failure behaviour within the rod during crimping a 3D strain based fracture criterion was developed and implemented within the commercial finte element package Abaqus. The verification of this criterion is done by simulating the crimping process followed by tensile tests. The numerical results are compared with the experiments and with the results obtained by SEM. An outlook on further work to improve the failure prediction is given. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Elastodynamic Problem of an Interface Linear Crack under Harmonic Loading
Authors: Mykhailova Iryna I. , Menshykov Oleksandr V. , Guz Igor A. 
Published: February 2009

AbstractThe present work is devoted to application of boundary integral equations to the 2D problem for a linear crack located on the bimaterial interface under harmonic loading. The system of linear algebraic equations is derived to solve the problem numerically. The distribution of the displacements and tractions at the bonding interface and the surface of the crack are obtained for the case of the tension–compression wave which propagates normally to the interface. The results are compared with those obtained for the static case. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)