bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling and Quasi‐Static Trajectory Control of a Self‐Balancing Two‐Wheeled Vehicle
Authors: Kilian F. Johannes , Gattringer Hubert , Bremer Hartmut 
Published: December 2012

AbstractThis paper introduces the kinematical and dynamical model as well as a quasi‐static trajectory control of a self‐balancing two‐wheeled vehicle. The mobile robot is about 60cm tall, autonomous, unstable and driven by two wheels. Hence, it can be used for transport purposes. Due to the nonholonomic constraints only few modeling techniques are feasible. In this case, the modeling is based on the Projection Equation, followed by the derivation of various control strategies.In order to allow a desired velocity and to stabilize the inclination angle of the robot a partial feedback linearization in combination with a LQR controller is applied. The quasi‐static trajectory controller, which is based on the kinematical model, uses a flatness based approach in order to remain on the desired path. Continuous curvature paths, composed by clothoids, enable good performance results in simulation and experiment. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of regenerative tissue for replacing the Bruch's membrane
Authors: Willenberg Wolfgang , Stoffel Marcus , Weichert Dieter , Thumann Gabriele 
Published: December 2012

AbstractIn the present study the anisotropic mechanical properties such as elasticity and diffusion of bovine Bruch's membrane (BM) and a collagen foils (CF) are compared with each other. For this reason, a constitutive material law is developed and implemented into a FEM software. Based on tensile tests, the material parameters of both materials are identified. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal control simulations of human arm motion
Authors: Maas Ramona , Leyendecker Sigrid 
Published: December 2012

AbstractUsing multibody systems to represent bones and joints is a common way to simulate human motion. Often, this is done with inverse or forward dynamics (solving initial value problems). However, many simulation tasks in biomechanics lead to boundary value problems, like performing a motion from a given start to a prescribed end position, which could be performed in various ways. In this context, we suppose that human motion is controlled in order to perform an optimal motion. Hence we formulate an optimal control problem (OCP) and compare the results when using different physiologically motivated cost functions. A direct transcription method called DMOCC (see [1]) is used to solve the OCP, whereby we benefit from it's structure preserving formulation, as the resulting optimal discrete trajectories are symplectic‐momentum preserving. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Elastic Properties of Muscle Tissue: Comparison of an Inverse Finite Element Approach and Homogeneous Deformation
Authors: Kruse Roland , Weichert Christine , Böl Markus 
Published: December 2012

AbstractParameters of material models are commonly identified by fitting predicted stress‐stretch relations to experimentally derived ones, assuming homogeneous deformation. This approach has been compared with an inverse finite element strategy, where an FE model of the actual measurement set‐up is created to obtain stress‐stretch data. Compressive tests of skeletal muscle tissue have been conducted for different fiber orientations, with a stereo camera system capturing the geometry of the sample. The material exhibited an exponential increase in stiffness with increasing stretch, with large differences related to the fiber orientation; this behavior is described well by a model for arterial layers. Assuming homogeneous deformation led to significantly different stress‐stretch curves indicating that this assumption is unrealistic in this case. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vibrations Action of the Trilling Machine MA750 on the Human Operator Hand
Authors: Arghir Mariana , Rus Mariana , Macovescu Sorin Constantin 
Published: December 2012

AbstractThe Work includes identifying and analyzing vibrations produced by a trilling machine MA750 within space work. To identify vibration is used a special method, which has not been used so far in identifying vibrations, with the action on the human body. For obtaining a very good identification of the human body vibrations has been used the Moiré projection method. General conditions were applied to human hand operator during working hours on a trilling machine, with different speeds of main shaft. In the paper are presented successively two methods of measuring the vibrations: the Moiré projection method and conventional method of measuring the vibrometer. The results in the booth situation (classical measurements and Moiré projection method) were in the same order of the unit scale, and the optical method named Moiré projection method can be considered a valid method for the human vibrations measurements without touch of the surface. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A network model for the EPS matrix of microbial biofilms
Authors: Ehret Alexander E. , Bolea Albero Antonio , Böl Markus 
Published: December 2012

AbstractWe present a constitutive model for microbial biofilms with application to biofilms of Pseudomonas aeruginosa whose EPS contain large amounts of alginate. The EPS matrix is modelled as a transient network of worm‐like chains with different types of junctions. The implementation as a nearly incompressible material allows large strain finite element calculations. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Creep damage modeling of a polycrystalline material
Authors: Ozhoga‐Maslovskaja Oksana , Altenbach Holm , Naumenko Konstantin , Prygorniev Oleksandr 
Published: December 2012

AbstractA polycrystalline material is investigated under creep conditions within the framework of continuum micromechanics. Geometrical 3D model of a polycrystalline microstructure is represented as a unit cell with grains of random crystallographical orientation and shape. Thickness of the plains, separating neighboring grains in the unit cell, can have non‐zero value. Obtained geometry assigns a special zone in the vicinity of grain boundaries, possessing unordered crystalline structure. A mechanical behavior of this zone should allow sliding of the adjacent grains. Within the grain interior crystalline structure is ordered, what prescribes cubic symmetry of a material. The anisotropic material model with the orthotropic symmetry is implemented in ABAQUS and used to assign elastic and creep behavior of both the grain interior and grain boundary material. Appropriate parameters set allows transition from the orthotropy to the cubic symmetry for the grain interior. Material parameters for the grain interior are identified from creep tests for single crystal copper. Model parameters for the grain boundary are set from the physical considerations and numerical model validation according to the experimental data of the grain boundary sliding in a polycrystalline copper [2]. As the result of analysis representative number of grains and grain boundary thickness in the unit cell are recommended. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of gradient‐enhanced damage evolution in viscoplastic plates under propagating disturbance
Authors: Nguyen A.D. , Stoffel M. , Weichert D. 
Published: December 2012

AbstractThis work investigates gradient‐enhanced damage evolution by performing a parameter study for the authors's finite element shell model [1], in which the free energy function is enhanced phenomenologically in terms of a non‐local damage variable and its gradient on the mid‐surface of shell structures. This enhancement gives rise to an introduction of gradient parameters in terms of a substructure‐related intrisic length‐scale and a relationship between non‐local and local damage variable. Based on the global displacement‐force curves obtained from shock‐tube tests on aluminium plate specimens, the gradient parameters are determined to validate the proposed shell model. The influence of spatial gradient of loading on the material behaviour within a macroscopic continuum element will be discussed through several examples. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of Calving Events in Antarctic Ice Shelves Using Configurational Forces
Authors: Plate Carolin , Gross Dietmar , Humbert Angelika , Müller Ralf 
Published: December 2012

AbstractPrevious studies on the sensitivity of cracks in ice shelves with different boundary conditions, stress states and density profiles revealed the need for further analyses. As the transfer of boundary conditions from dynamic ice flow simulations to the linear elastic fracture analyses proved to be a critical point in previous studies, a new approach to relate viscous and elastic material behaviour is proposed. The numerical simulations are conducted using Finite Elements utilizing the concept of configurational forces. To show the applicability of the approach, a 2‐dimensional plane stress geometry with volume loads due to the ice shelf flow is analyzed. The resulting crack path is compared to available crack paths from satellite images. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A BEM for transient thermoelastic analysis of a functionally graded layer on a homogeneous substrate under thermal shock
Authors: Ekhlakov Alexander , Khay Oksana , Zhang Chuanzeng 
Published: December 2012

AbstractTransient thermoelastic analysis of isotropic and linear thermoelastic bimaterials, which are constituted by a functionally graded (FG) layer attached to a homogeneous substrate, subjected to thermal shock is presented in this paper. For this purpose, a boundary element method for transient linear coupled thermoelasticity is developed. The material properties of the FG layer are assumed to be continuous functions of the spatial coordinates. The boundary‐domain integral equations are derived by using the fundamental solutions of linear coupled thermoelasticity for the corresponding isotropic, homogeneous and linear thermoelastic solids in the Laplace‐transformed domain. For the numerical solution, a collocation method with piecewise quadratic approximation is implemented. Numerical results for the dynamic stress intensity factors are presented and discussed. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparative Study of Experimental and Simulated Buckled Shapes of Alternately‐Loaded Plates
Authors: Todres Russell , Stoffel Marcus , Weichert Dieter 
Published: December 2012

AbstractA circular plate is inelastically deformed by uniform pressure, unloaded and then alternately reloaded to the same peak level. For each iteration, snap‐through occurs at an increased pressure relative to the previous one, leading to additional plastic deformation. By repeating this process, the plate either fails or a limit state of deformation is reached under peak pressure without snap‐through. For the case of a limit state, the results of [1] are extended to numerically determine the pressure above the peak level causing the plate to snap‐through again. This is compared to the snap‐through pressure of an initially unloaded spherical cap whose radius corresponds to the maximum displacement achieved in the limit case. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of the lamination stack influence on the stiffness of stator active component
Authors: Luchscheider Vera , Willner Kai 
Published: December 2012

AbstractFor electric motors light weight construction is becoming increasingly important. Therefore the mechanical behavior of the lamination stack is necessary to be known for the simulation. The stacking of a lot of sheets has a relevant influence onto the behavior of the whole motor, because of the significant contact characteristics between the sheets. Quasi‐static tests are performed to identify this. In these tests an axial load, representing the packaging process, is applied onto the stacked sheets and thereafter a cyclic load is superposed. With these quasi‐static tests elastic and plastic effects and a hysteretic behavior are detected. For modeling this stiffness behavior nonlinear springs and frictional elements, containing the Coulomb's law, are assembled. The nonlinearities and the hysteresis are dependent on the sheet's roughness. Moreover the behavior of the stack is influenced by the coreplate varnish viscoelasticity. With modeling these effects, the measured values can be well simulated. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of nano‐particle interactions on the mechanical behavior of colloidal structures in polymeric solutions
Authors: Dargazany Roozbeh , Khiêm Vu Ngoc , Itskov Mikhail 
Published: December 2012

AbstractColloidal structures inside solutions are usually considered as rigid bodies or linear springs. However, recent experimental results show a strongly nonlinear mechanical response of large clusters. In this contribution, the nonlinear elastic behavior of the colloidal structures inside polymeric solutions is studied. So far, the influences of initial length and fractal dimension on the elastic response of colloidal structures have mostly been considered by scaling theory. Here, we additionally take into account a deformation induced evolution of the aggregate structure which is mainly influenced by inter‐particle interactions. To this end, central and lateral (non‐central) inter‐particle forces are considered separately. Next, the directional stiffness of the colloidal structure is evaluated by using the concept of a backbone chain. The backbone chain is a unique path between two ends of the colloidal structure that carries the main portion of load. The mechanical response of the backbone chain depends on aggregate geometry, deformation history and moreover, on the nature and the strength of the inter‐particle interactions. The aggregate geometry is described by means of the angular averaging concept. The so‐obtained model can further be generalized for all types of colloidal structures with central and lateral inter‐particle forces. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of heat treatment on the phase transformation in powder metallurgical multi‐functional coating
Authors: Kebriaei Reza , Vladimirov Ivaylo , Frischkorn Jan , Reese Stefanie 
Published: December 2012

AbstractHeat treatment is an important part of the manufacturing of metallic products, especially in powder coating processes. It provides an efficient way to improve the properties of the metal as e.g. hardness by controlling the rate of diffusion and the rate of cooling within the microstructure. The process‐integrated powder coating by radial axial rolling of rings is a new hybrid production technique which is introduced in [1]. The applied temperatures in hot rolling are within the range of austenitizing temperatures for the investigated steels [2]. Therefore, reasonably controlling the temperature is an important task [3]. The paper is concerned with the integration of heat treatment of the rolled ring into the subsequent cooling process. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A rheological model for arbitrary symmetric distortion of the yield surface
Authors: Shutov A. V. , Ihlemann J. 
Published: December 2012

AbstractA phenomenological model of metal viscoplasticity, which takes combined isotropic, kinematic, and distortional hardening into account, is motivated by a new rheological model. The distinctive advantage of the material model is that any smooth convex saturated form of the yield surface which is symmetric with respect to the recent loading direction can be captured. In particular, an arbitrary sharpening of the saturated yield locus in the loading direction combined with a flattening on the opposite side can be covered. Moreover, the yield locus evolves smoothly and its convexity is guaranteed at each hardening stage. The underlying two‐dimensional rheological analogy can be used to provide insight into the main constitutive assumptions. This rheological model is utilized as a guideline for the construction of phenomenological constitutive relations. The distortion of the yield surface is described with the help of a so‐called distortional backstress. Thus, 2nd rank tensors are utilized only. The resulting material model is thermodynamically consistent. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Accelerating constitutive modeling by automatic tangent generation
Authors: Rothe Steffen , Hartmann Stefan 
Published: December 2012

AbstractWithin the framework of finite elements the linearization within a Newton‐like method requires the computation of the so‐called consistent tangent operator. There are several possibilities to get these derivatives. Three methods, namely analytical, numerical and automatic differentiation, for tangent generation will be analyzed concerning the simulation time and applicability for three different constitutive models. These models are a finite strain hyperelasticity model, finite strain viscoplasticity model for metal powders and a small strain thermoviscoplasticity model. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the connection of dissipation and deviatoric stress in the continuum theory of defects
Authors: Schnepp Johannes 
Published: December 2012

AbstractIn a material space‐time manifold an expression for the entropy production is developed. It is based on a Lagrangian formulation for a hyperelastic solid. The material structure and heat transfer are represented by a tetrad field. The derivatives of the Lagrangian with respect to the time‐like vector of the tetrad yields entropy density and current. An identity for the divergence of this four‐current follows from the invariance of the Lagrangian and yields the entropy production due to heat transfer and defect movement. The latter part only depends on a kind of deviatoric stress if the conservation of mass is considered. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bituminous asphalt concrete: Aspects on scale‐bridging
Authors: Schüler Thorsten , Jänicke Ralf , Steeb Holger 
Published: December 2012

AbstractThis paper will give a short overview about a multi‐scale modelling approach for bituminous asphalt concrete. The goal is to describe the micro‐heterogeneous medium by a homogeneous surrogate medium, which has similar effective mechanical properties. Starting from the varying constitutive behaviour on the micro‐scale, our up‐scaling procedure is realised via volume averaging techniques. By use of a Finite‐Element model, the results for different types of boundary conditions (BCs) and their influence on the properties of the compund are investigated on the effective scale. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fracture toughness investigations of ferroelectric materials considering effects on macro‐ and micro‐scale
Authors: Gellmann Roman , Ricoeur Andreas 
Published: December 2012

AbstractIn the present work we study toughness variation of ferroelectric materials (PZT‐5H) considering different scales for different poling and loading conditions. On the macro‐scale we apply an extended theory of stresses at interfaces in dielectric solids. Further, on the micro‐scale, nonlinear effects are introduced by applying the small scale switching approximation. The analysis is done considering the full anisotropy and electromechanical coupling of the material. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fluid‐Structure‐Interaction‐Analysis concerning Damping Features of Viscous Fluids
Authors: Fuchs Vilmar , Wünsch Olaf 
Published: December 2012

AbstractThis work deals with Fluid‐Structure‐Interaction (FSI) concerning damping characteristics of viscous liquids, which are investigated to make the offshore structures more secure and efficient. On that account, we modeled a damping element prototype consisting essentially of an elastic cover that is attached to the cylindrical mono pile foundation at the height of waves. Within the framework of FSI, the impact of breaking waves on a three‐dimensional model of a damping element prototype corresponding to [1] is simulated. In order to measure the influence of different liquid properties on the damping of the impact, the calculations are set up using newtonian and non‐newtonian fluids with varying viscosity. For the non‐newtonian investigation verification is carried out with a CFD model. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational homogenization of materials with small deformation to determine configurational forces
Authors: Khalaquzzaman Md. , Xu Baixiang , Müller Ralf 
Published: December 2012

AbstractIn this work the mechanical boundary condition for the micro problem in a two‐scaled homogenization using a FE2 approach is discussed. The strain tensor is often used in the literature for small deformation problem to determine the boundary conditions for the boundary value problem on the micro level. This strain tensor based boundary condition gives consistent homogenized mechanical quantities, e.g. stress tensor and elasticity tensor, but the present work points out that it leads to unphysical homogenized configurational forces. Instead, we propose a displacement gradient based boundary condition for the micro problem. Results show that the displacement gradient based boundary condition can give not only the consistent homogenized mechanical quantities but also the appropriate homogenized configurational forces. The interpretation of the displacement gradient based boundary condition is discussed. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Viscoelastic effects and shrinkage as accompanying phenomena of the curing of polymers. Single‐ and multiscale effects
Authors: Klinge Sandra , Bartels Alexander , Hackl Klaus , Steinmann Paul 
Published: December 2012

AbstractThe contribution deals with the modeling of two phenomena that are characteristic of the curing of polymers, namely the increasing viscosity and the volume decrease known as autogeneous shrinkage. Both of these processes are caused by the crosslinking of polymer chains during polymerization. In order to model the viscoelastic effects, the free energy consisting of an equilibrium and a non‐equilibrium part is proposed. The former is related to the elastic processes and depends on total deformations. The latter is caused by the viscoelastic effects and only depends on the elastic part of deformations. In order to avoid volume locking effects typical of isochoric materials, both parts of the free energy density are furthermore split into a volumetric and a deviatoric part. A multifield description depending on the displacements, volume change and hydrostatic pressure is introduced as well. Different from the viscous process, the modeling of shrinkage effects does not require a new assumption for the free energy but a split of the total deformation gradient into a shrinkage and a mechanical part. The model suitable for simulating both of the mentioned phenomena is implemented in the single‐ and multiscale FE program. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite element simulation of deformation behaviour of cellular rubber components
Authors: Raghunath R. , Juhre D. 
Published: December 2012

AbstractThis paper presents a new prospect of investigating the mechanical behaviour of cellular rubber using porous hyperelastic material model. There are number of hyperelastic material models to describe the behaviour of homogeneous elastomer, but very few to characterise the complex properties of cellular rubber. The analysis of dependence of material behaviour on pore density using the new material model is supported with experiments to characterise the actual material behaviour. The new material model which is based on Danielsson et al [1] decouples the influence of porosity from the mechanical properties of the solid material by introducing volume fraction of the pores as an explicit scalar variable. The finite element simulations are then followed by experiments on complex model to validate the material model. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)