bluuebunny/crossref_metadata_2025_split huggingface dataset:
A qualitative exploration of nurses leaving nursing practice in China
Authors: Zhu Junhong , Rodgers Sheila , Melia Kath M. 
Published: December 2014

AbstractAimThis paper reports a theoretical understanding of nurses leaving nursing practice by exploring the processes of decision‐making by registered nurses in China on exiting clinical care.BackgroundThe loss of nurses through their voluntarily leaving nursing practice has not attracted much attention in China. There is a lack of an effective way to understand and communicate nursing workforce mobility in China and worldwide.DesignThis qualitative study draws on the constant comparative method following a grounded theory approach.MethodIn‐depth interviews with 19 nurses who had left nursing practice were theoretically sampled from one provincial capital city in China during August 2009–March 2010.ResultsThe core category ‘Mismatching Expectations: Individual vs. Organizational’ emerged from leavers’ accounts of their leaving. By illuminating the interrelationship between the core category and the main category ‘Individual Perception of Power,’ four nursing behaviour patterns were identified: (1) Voluntary leaving; (2) Passive staying; (3) Adaptive staying and (4) Active staying.
Coupling‐based methods to design feedback controllers and observers for nonlinear descriptor systems
Authors: Labisch Daniel , Konigorski Ulrich 
Published: December 2014

AbstractThis paper presents a new approach for analysis and controller design for nonlinear descriptor systems. Thereby, we assume that the descriptor system is given in semi‐explicit form and has a continuously differentiable solution, which are very mild assumptions and are fulfilled for most practical applications. Based on the known coupling controller design we transfer the analysis and synthesis from the descriptor system to an equivalent system in state‐space form. Methods like dynamic and static input‐output decoupling, input‐output linearization, model‐based feedforward‐controller design, zero dynamics, exact descriptor linearization, linear time variant Riccati control, and causal observer design have been introduced based on the coupling procedure [9]. In the following, we summarize the new approach and an algorithm to compute the required state‐space system. Additionally, a short introduction how to use it for decoupling control, Riccati control, and causal observer design is given. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Parametric Reduction of FE Models with Variable Mesh Topology
Authors: Mohring Jan 
Published: December 2014

AbstractDesigning whole machines or processes you may need both, an integrated dynamic simulation of all components on system level and a detailed analysis of how the macroscopic behavior of a component depends on geometry and material parameters. The former analysis is usually based on systems of differential algebraic equations representing a component by not more than a few hundred states and requires tools like Matlab‐Simulink® or Dymola®. The latter analysis solves discretized partial differential equations with several 100,000 degrees of freedom using finite element software like Ansys® or Comsol®. Model reduction bridges the gap between the two worlds providing small state space models with approximately the same input‐output behavior as the original large finite element models. Building systems from generic components, e.g. a gas transport network from pipeline models with variable length, or optimizing the design of a device with respect to mechanical or thermal properties, we need parametric reduced models. The idea is to reduce FE models offline for selected parameter sets and to generate models for new parameters by cheap interpolation rather than expensive reduction. The different approaches to parametric linear model reduction may be divided into three classes [1]. Interpolation of transfer functions is well suited for parabolic or highly damped hyperbolic problems. However, poles are duplicated rather than shifted, which is unacceptable for weakly damped hyperbolic problems like in mechanics. The second class of methods look for a basis of state space covering system behavior over the full range of parameters. They share the critical assumption that number and meaning of states do not change with the parameters. In terms of finite elements this means that the meshes for different design parameters are morphed variants of the same reference mesh.This may become a severe restriction in practice when automatic meshing is to be applied to complicated geometries. Therefore, we propose a method from the third class, which is based on interpolating reduced system matrices [2]. Only those parts of the mesh need to share a constant topology where nodal inputs are applied and outputs are collected. The inner mesh, however, may change for different parameters. The main challenges arise from the fact that state space representations of a system are unique only up to a change of basis and that interpolating matrices which refer to non‐fitting bases may cause arbitrary errors. In the article we will show how problems like leaving and entering modes or eigenvalue crossing can be overcome by using normal forms and eigenvalue tracking in parameter space. The method, which is implemented in the Fraunhofer Model Reduction Toolbox, is applied to a parametric model of a mechanical device the eigenfrequencies of which have to be kept away from some dominant excitation frequencies. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Higher order Trefftz‐like Finite Element Method on meshes with L‐shaped elements
Authors: Weißer Steffen 
Published: December 2014

AbstractIn 2009, the BEM‐based FEM was introduced as an numerical approach for the treatment of boundary value problems. It is a Finite Element Method (FEM) that uses Trefftz‐like basis functions which are defined to fulfil the underlying differential equation locally and which are treated by means of Boundary Element Methods (BEM). Due to the implicit definition of basis functions, this approach is applicable on general polygonal and polyhedral meshes and yields conforming approximations. The elements of the discretization do not necessarily have to be convex. After a review of the recent development of higher order basis functions the method is applied to a model problem on a sequence of meshes with L‐shaped elements. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Error analysis for co‐simulation with force‐displacement coupling
Authors: Arnold Martin , Hante Stefan , Köbis Markus A. 
Published: December 2014

AbstractCo‐simulation is a simulation technique for time dependent coupled problems in engineering that restricts the data exchange between subsystems to discrete communication points in time. In the present paper we follow the block‐oriented framework in the recently established industrial interface standard FMI for Model Exchange and Co‐Simulation v2.0 and study local and global error of co‐simulation algorithms for systems with force‐displacement coupling. A rather general convergence result for the co‐simulation of coupled systems without algebraic loops shows zero‐stability of co‐simulation algorithms with force‐displacement coupling and proves that order reduction of local errors does not affect the order of global errors. The theoretical investigations are illustrated by numerical tests in the novel FMI‐compatible co‐simulation environment SNiMoWrapper. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Limitations of computing time savings in variational multirate integrations
Authors: Gail Tobias , Leyendecker Sigrid , Ober‐Blöbaum Sina 
Published: December 2014

AbstractFor systems that contain slow and fast dynamics, variational multirate integration schemes are used. These schemes split the system into parts which are simulated using a time grid consisting of micro and macro nodes. This leads to computing time savings, however not unlimited, for a certain number of micro steps per macro step the computing time is minimal. To find a relation between this minimum computing time and the number of variables in the system, the computing time for the Fermi‐Pasta‐Ulam problem (FPU) is measured for different numbers of masses and different numbers of micro steps. In addition, the numerical convergence of the variational multirate integration is shown for the FPU. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the history of lateral vehicle dynamics
Authors: Schiehlen Werner 
Published: December 2014

AbstractThe lateral motion of vehicles on tracks and roads is characterized by the rolling contact between wheels and guideway. Railway vehicles feature passive lateral guidance while road vehicles are operated by steering. Lateral dynamics is an extremely complex problem but the fundamental behaviour can already understood by strongly simplified mechanical models. In this paper the historical development of modelling approaches for lateral dynamics is reviewed what is very helpful for benchmarking and checking more complex problems, too. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A structure preserving approach to the simulation of non‐smooth dynamics
Authors: Koch Michael W. , Leyendecker Sigrid 
Published: December 2014

AbstractThe investigated multibody dynamics involve perfectly elastic, partially elastic and perfectly plastic contacts and a structure preserving approach is used in forward dynamics and optimal control simulations. The applied mechanical integrator is based on a constrained version of the Lagrange‐d’Alembert principle and it represents exactly the behaviour of the analytical solution concerning the consistency of momentum maps and symplecticity: it is called symplectic momentum scheme. To guarantee the geometric exactness during the establishing or releasing of contacts, the non‐smooth problem is solved including the computation of the contact configuration, time and force, instead of relying on a smooth approximation of the contact problem via a penalty potential. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New forms of the equations of the attitude kinematics
Authors: Mladenova Clementina D. , Brezov Danail S. , Mladenov Ivaïlo M. 
Published: December 2014

AbstractIn the present paper, a new formalism for obtaining the kinematical equations of a rigid body motion is proposed. It is based on an alternative parameterization of the Lie group SO(3). Here we provide a new description of attitude kinematics by means of decomposing an arbitrary rotation into a pair of successive rotations about a fixed axis û and a varying one v̂, which is perpendicular to û. Then û, v̂ and û × v̂ constitute a basis, in which it is most natural to obtain the kinematic equations. The latter appear to be quite simple when they are expressed in terms of the vector‐parameter provided that the rotation about the fixed axis is applied first (in the body reference frame). The procedure is illustrated in different situations, in which explicit solutions are available. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling the Physiological Behavior of Arterial Walls – Comparative Study Regarding the Viscoelastic Response
Authors: Fausten Simon , Balzani Daniel , Schröder Jörg 
Published: December 2014

AbstractThis contribution deals with the modeling of the physiological behavior of arterial walls, in order to enable a reliable calculation of the transmural stress distribution including also the active response of arterial tissue. Therefore, a simple viscoelastic model, which only requires few material parameters, is considered. Furthermore, a comparative study, investigating the influence of viscoelasticity on the mechanical behavior of arterial walls, is presented. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Remodeling of soft tissues due to cell activity
Authors: Yi Jeong‐Hun , Stoffel Marcus , Weichert Dieter , Rath Björn , Markert Bernd 
Published: December 2014

AbstractThe continuum mechanical modeling of collagenous biological tissues is of interest in the field of biomedical engineering. Particularly, the change of material properties as a result of cell activity is of great interest, as chondrocyte (cartilage cell) implantation yields significant functional improvement.The aim of the contribution is to present the remodeling phenomenon of a cellular material due to cell activity, which results in synthesis of collagen type‐II fibers. For the experimental study, cellular condensed gel is mechanically stimulated in a bioreactor for four weeks. The change of the stiffness of the gel is measured in a compression test. The remodeling process is theoretically derived by an appropriate evolution law in the framework of continuum mechanics. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Multi‐Component Description of Osmotic Driven Deformations in Articular Cartilage
Authors: Albrecht Daniel , Ricken Tim , Pierce David M. 
Published: December 2014

AbstractThis study focuses on a formulation within the theory of porous media (TPM) for continuum multicomponent modeling of osmotic driven deformation in articular cartilage. The cartilage consists of porous solid matrix (extracellular matrix(ECM)),which is reinforced by collagen fibers and saturated by a fluid phase. The solid and fluid phases are considered as immiscible constituents occupying spatially their individual volume fraction. However, both phases include electrolytes, which are responsible for the osmotic pressure. The collagen fiber induce both, a transverse‐isotropic stress and permeability behavior which is represented in the modal approach by an invariant‐based description for the stress and anisotropic permeability tensor for the fluid flow, respectively. The osmotic pressure is captured by considering the electro‐chemical potential of the electrolytes. After discussing the main details of the large‐strain coupled poro‐osmotic‐hyper‐elastic model approach, a brief numerical example is given. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental and numerical investigation of a degradable collagen foil
Authors: Willenberg Wolfgang , Stoffel Marcus , Markert Bernd 
Published: December 2014

AbstractA collagen foil, which plays an important role for cultivating and investigating tendon cells, is investigated experimentally and numerically: The foil, which should later serve as a scaffold for tendon cells in a custom made bioreactor, is stimulated periodically in an in situ experiment. Additionally, a material model to describe the anisotropic structure and the relaxation behaviour of the collagen foil is used to simulate the material response. By comparing the measurements and simulations, the stress and strain states in the foil can be determined. Hence, the material parameters for the presented experimental set up are identified. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experiments and numerical simulations on damage behavior of biaxially loaded specimen
Authors: Brenner Daniel , Gerke Steffen , Brünig Michael 
Published: December 2014

AbstractThe paper deals with the effect of stress state on damage and failure behavior of isotropic ductile metals. In the continuum damage model the damage behavior of ductile metals is adequately described by a generalized damage condition and an anisotropic damage rule. The damage criterion is based on series of uniaxial experiments with differently notched specimens and corresponding numerical simulations as well as on various numerical calculations on the micro‐scale. Different branches of the damage criterion depending on stress triaxiality and Lode parameter are considered. To be able to validate the proposed stress‐state‐dependent functions new experiments with two‐dimensionally loaded specimens have been developed. Corresponding numerical simulations show that these shear‐tension and shear‐compression tests cover a wide range of stress triaxialities and Lode parameters. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling and Simulation of Damage Processes based on a Gradient‐Enhanced Free Energy Function
Authors: Schwarz Stephan , Junker Philipp , Hackl Klaus 
Published: December 2014

AbstractTaking into account softening effects in connection with conventional inelastic material models can cause ill‐posed boundary value problems. These problems can be established by obtaining no unique solution for the resulting algebraic system or by having a strong mesh dependence of the numerical results. This is the consequence of losing ellipticity of the governing field equations. A possible approach to solve these problems is to introduce a non‐local field function in the model which includes an internal material length scale. For this purpose a gradient‐enhanced free energy function is used for the current continuum damage model from which two variational equations are resulting. Calculations with less effort can be achieved due to the enhancement of the free energy function in comparison to other approaches. The mentioned model is applied to a material with locally varying damage properties (yield limits). Furthermore, the model is able to describe crack propagation in cases of completely damaged material. Therewith, a matrix material including precipitates, such as carbides, is modeled. This allows to investigate ship screws, which usually exhibit the mentioned composition, with regard to the influence of cavitation. Cavitation describes the implosion of risen vapor bubbles, whereby the impact on screws causes heavy damages which can lead to a complete destruction. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micro‐mechanical analyses of the effect of stress triaxiality and the Lode parameter on ductile damage and failure
Authors: Hagenbrock Vanessa , Gerke Steffen , Brünig Michael 
Published: December 2014

AbstractThe paper deals with the effect of different stress states on plastic deformations, damage and fracture of ductile materials. To be able to model these effects a continuum damage model has been introduced taking into account the dependence of stress‐state on the constitutive equations. The model is based on the introduction of damaged and fictitious undamaged configurations. All parameters appearing in the constitutive equations are stress‐state‐dependent which can be characterized by the stress intensity, the stress triaxiality and the Lode parameter. Only experiments are not adequate enough to determine all constitutive parameters. Thus, additional series of three‐dimensional micro‐mechanical simulations of representative volume elements have been performed to get more insight in the complex damage mechanisms. These simulations cover a wide range of stress triaxialities and Lode parameters in tension, shear and compression domains. After all, the results from the micro‐mechanical simulations are used to suggest the damage equations and to identify corresponding parameters. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of deformation‐induced phase transformation during very high cycle fatigue (VHCF) using the boundary element method
Authors: Hilgendorff P.‐M. , Fritzen C.‐P. , Grigorescu A. , Zimmermann M. , Christ H.‐J. 
Published: December 2014

AbstractA microstructural simulation model is proposed which accounts for damage accumulation in shear bands and deformation‐induced martensite formation in a metastable austenitic stainless steel (AISI304). The model is numerically solved using the two‐dimensional (2‐D) boundary element method. By using this method, sliding displacements can be directly evaluated in shear bands and austenite grains as well as generated martensite domains with their individual mechanical properties and shape deformation can be considered. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strategies for the Computation of Configurational Forces in Dissipative Media
Authors: Kuhn Charlotte , Lohkamp Richard , Müller Ralf , Schneider Frank , Aurich Jan C. 
Published: December 2014

AbstractConfigurational forces can be interpreted as driving forces on material inhomogeneities such as crack tips. In dissipative media the total configurational force on an inhomogeneity consists of an elastic contribution and a contribution due to the dissipative processes in the material. For the computation of discrete configurational forces acting at the nodes of a finite element mesh, the elastic and dissipative contributions must be evaluated at integration point level. While the evaluation of the elastic contribution is straightforward, the evaluation of the dissipative part is faced with certain difficulties. This is because gradients of internal variables are necessary in order to compute the dissipative part of the configurational force. For the sake of efficiency, these internal variables are usually treated as local history data at integration point level in finite element (FE) implementations. Thus, the history data needs to be projected to the nodes of the FE mesh in order to compute the gradients by means of shape function interpolations of nodal data as it is standard practice. However, this is a rather cumbersome method which does not easily integrate into standard finite element frameworks. An alternative approach which facilitates the computation of gradients of local history data is investigated in this work. This approach is based on the definition of subelements within the elements of the FE mesh and allows for a straightforward integration of the configurational force computation into standard finite element software. The suitability and the numerical accuracy of different projection approaches and the subelement technique are discussed and analyzed exemplarily within the context of a crystal plasticity model. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computation of crack propagation in 3‐dimensional anisotropic solids
Authors: Steigemann Martin , Specovius‐Neugebauer Maria 
Published: December 2014

AbstractThis contribution presents ideas, how crack propagation in three‐dimensional solids composed of anisotropic materials can be predicted using the Griffith energy principle. Since the work of Irwin the change of potential energy caused by a straight elongation of a crack in an isotropic two‐dimensional homogeneous structure can be expressed in quadratic terms of the stress intensities at the crack tip. This result was generalized in the last decades using methods of asymptotic analysis by many authors [1] to more complicated geometries, to anisotropic and inhomogeneous materials. With the energy release rate at hand, quasi‐static scenarios of crack propagation can be simulated for plane problems [2], but this is still a complicated task for three‐dimensional problems [3]. We show an idea how the change of energy caused by propagation of a crack surface in a fully three‐dimensional solid of nearly arbitrary shape can be computed in anisotropic materials. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Solution of the Consistently Linearized Eigenproblem by Means of a Finite Difference Expression for Approximation of a Directional Derivative in MSC.MARC
Authors: Pavlicek Stefan , Xia Jin , Mang Herbert A. 
Published: December 2014

AbstractMore recently, a concept of energy‐based categorization of buckling was proposed. It represents a symbiosis of mechanics of solids and spherical geometry. The fundamental mathematical background of this concept is the so‐called consistently linearized eigenproblem. The numerical solution of this eigenproblem by means of the finite element method is a key issue of the mentioned concept. This solution is obtained with the help of the commercial finite element software MSC.MARC. An iterative process, involving the programming lanuages PYTHON and FORTRAN 77 and the software MATLAB, is devised, making use of the available element library, of different types of solvers, and of further modeling tools. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)