bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling of reinforced‐concrete structures providing crack‐spacing based on X‐FEM, ED‐FEM and novel operator split solution procedure
Authors: Ibrahimbegovic Adnan , Boulkertous Amor , Davenne Luc , Brancherie Delphine 
Published: March 2010

AbstractIn this work, we present a novel approach to the finite element modelling of reinforced‐concrete (RC) structures that provides the details of the constitutive behavior of each constituent (concrete, steel and bond‐slip), while keeping formally the same appearance as the classical finite element model. Each component constitutive behavior can be brought to fully non‐linear range, where we can consider cracking (or localized failure) of concrete, the plastic yielding and failure of steel bars and bond‐slip at concrete steel interface accounting for confining pressure effects. The standard finite element code architecture is preserved by using embedded discontinuity (ED‐FEM) and extended (X‐FEM) finite element strain representation for concrete and slip, respectively, along with the operator split solution method that separates the problem into computing the deformations of RC (with frozen slip) and the current value of the bond‐slip. Several numerical examples are presented in order to illustrate very satisfying performance of the proposed methodology. Copyright © 2010 John Wiley & Sons, Ltd.
A stable explicit fractional step procedure for the solution of heat and fluid flow through interfaces between saturated porous media and free fluids in presence of high source terms
Authors: Arpino F. , Massarotti N. , Mauro A. 
Published: March 2010

AbstractIn this paper, porous medium‐free fluid interface problems in the presence of high source terms are studied for the first time by using a stable, accurate and efficient Artificial Compressibility (AC) Characteristic‐Based Split (CBS) algorithm. The interest in the AC‐CBS scheme has increased, as its matrix‐inversion free procedure offers the possibility of an easy and efficient parallelization. The present algorithm, recently introduced for the solution of porous media flows, presented some difficulties in solving complex interface problems. In this paper, the AC‐CBS scheme has been specifically developed to overcome such difficulties and produce an accurate, stable, and efficient solution for the generalized porous medium flow equations for forced, free, and mixed convection through interfaces. In order to obtain the present results, a stability analysis for the AC‐CBS scheme for the solution of problems with high source terms is carried out for the first time. The efficiency and the accuracy of the AC‐CBS algorithm are verified through comparison with analytical, numerical, and experimental data available in the literature. The authors consider three different types of interface benchmark problems: (i) forced convection in a horizontal channel; (ii) mixed convection in a vertical channel; and (iii) natural convection in a vertically divided cavity. Copyright © 2010 John Wiley & Sons, Ltd.
Simulation of transient heat conduction using one‐dimensional mapped infinite elements
Authors: Motley M. R. , Prévost J. H. 
Published: March 2010

AbstractMany engineering problems exist in physical domains that can be said to be infinitely large. A common problem in the simulation of these unbounded domains is that a balance must be met between a practically sized mesh and the accuracy of the solution. In transient applications, developing an appropriate mesh size becomes increasingly difficult as time marches forward. The concept of the infinite element was introduced and implemented for elliptic and for parabolic problems using exponential decay functions. This paper presents a different methodology for modeling transient heat conduction using a simplified mesh consisting of only two‐node, one‐dimensional infinite elements for diffusion into an unbounded domain and is shown to be applicable for multi‐dimensional problems. A brief review of infinite elements applied to static and transient problems is presented. A transient infinite element is presented in which the element length is time‐dependent such that it provides the optimal solution at each time step. The element is validated against the exact solution for constant surface heat flux into an infinite half‐space and then applied to the problem of heat loss in thermal reservoirs. The methodology presented accurately models these phenomena and presents an alternative methodology for modeling heat loss in thermal reservoirs. Copyright © 2010 John Wiley & Sons, Ltd.
An improved cohesive element for shell delamination analyses
Authors: Yang Q. D. , Fang X. J. , Shi J. X. , Lua J. 
Published: March 2010

AbstractIn this paper, an improved cohesive element is proposed for accurate quantification of delamination in laminar composites. The improved cohesive element employs a mixed Gaussian and sub‐domain integration scheme for cohesive stress integration. Level set description of crack front geometry is used to accurately track the evolving delamination crack front. The new element offers significant improvement in solution accuracy and numerical stability, as compared with conventional cohesive elements using either Gaussian integration or Newton–Cotes integration. The much enhanced numerical accuracy and stability permit the use of bonded structural element size as large as 1∼1.5 times the cohesive zone size without significantly compromising numerical accuracy and efficiency. This greatly alleviates the strict mesh size requirement imposed by conventional cohesive elements that require the bonded structural element size be smaller than \documentclass{article}\footskip=0pc\pagestyle{empty}\begin{document}$\frac{1}{3}\sim\frac{1}{5}$\end{document} of the cohesive zone size. Furthermore, the new element offers the benefit of easy insertion of arbitrary initial crack geometry for a structured mesh. Copyright © 2010 John Wiley & Sons, Ltd.
Numerical aspects associated with the implementation of a finite strain, elasto‐viscoelastic–viscoplastic constitutive theory in principal stretches
Authors: Holmes D. W. , Loughran J. G. 
Published: March 2010

AbstractThis paper treats the numerical implementation of a finite strain, elasto‐viscoelastic–viscoplastic constitutive model for semi‐crystalline polymers, written in principal stretches. A parallel configuration of the three model elements is used that enables the decoupled algorithmic treatment of each response within a stress update numerical scheme. The numerical aspects associated with the use of principal stretch constitutive expressions in a tensor space numerical environment are initially developed for the general cases of any elastic or inelastic constitutive element. Included is the formulation of the closed‐form, consistent tangential modulus tensor. The principal space algorithmic treatments of the elastic, viscoelastic and viscoplastic elements are then used as specific examples. Of particular importance is the development of a principal space, closest point projection return mapping algorithm for viscoplasticity including isotropic strain hardening. Preliminary numerical examples are presented to illustrate the versatility of the model. Copyright © 2010 John Wiley & Sons, Ltd.
Evaluation of Green's function derivatives for exponentially graded elasticity
Authors: Sallah Omar M. , Gray L. J. , Nintcheu Fata S. 
Published: March 2010

AbstractEffective formulas for computing Green's function of an exponentially graded three‐dimensional material have been derived in previous work. The expansion approach for evaluating Green's function has been extended to develop corresponding algorithms for its first‐ and second‐order derivatives. The resulting formulas are again obtained as a relatively simple analytic term plus a single double integral, the integrand involving only elementary functions. A primary benefit of the expansion procedure is the ability to compute the second‐order derivatives needed for fracture analysis. Moreover, as all singular terms in this hypersingular kernel are contained in the analytic expression, these expressions are readily implemented in a boundary integral equation calculation. The computational formulas for the first derivative are tested by comparing with results of finite difference approximations involving Green's function. In turn, the second derivatives are then validated by comparing with finite difference quotients using the first derivatives. Published in 2010 by John Wiley & Sons, Ltd.
Algebraic multigrid for finite element elasticity equations: Determination of nodal dependence via edge‐matrices and two‐level convergence
Authors: Karer E. , Kraus J. K. 
Published: March 2010

AbstractWe study an algebraic multigrid (AMG) method for solving elliptic finite element equations of linear elasticity problems. In this method, which has been proposed in (Kraus, SIAM J Sci Comput 2008; 30: 505–524), the coarsening is based on the so‐called edge‐matrices, which allows to generalize the concept of strong and weak connections, as used in the classical AMG, to ‘algebraic vertices’ that accumulate the nodal degrees of freedom in case of vector‐field problems. The major contribution of this work is related to the investigation of a measure for the nodal dependence and on the generation of the edge‐matrices, which are the basic building blocks of this method. A natural measure is the cosine of the abstract angle between the two subspaces spanned by the basis functions corresponding to the respective algebraic vertices. Another original contribution of this work is a two‐level convergence analysis of the method. The presented numerical results cover also problems with jumps in Young's modulus of elasticity and orthotropic materials. Copyright © 2010 John Wiley & Sons, Ltd.
Coupling of finite element and boundary integral methods for a capsule in a Stokes flow
Authors: Walter J. , Salsac A.‐V. , Barthès‐Biesel D. , Le Tallec P. 
Published: March 2010

AbstractWe introduce a new numerical method to model the fluid–structure interaction between a microcapsule and an external flow. An explicit finite element method is used to model the large deformation of the capsule wall, which is treated as a bidimensional hyperelastic membrane. It is coupled with a boundary integral method to solve for the internal and external Stokes flows. Our results are compared with previous studies in two classical test cases: a capsule in a simple shear flow and in a planar hyperbolic flow. The method is found to be numerically stable, even when the membrane undergoes in‐plane compression, which had been shown to be a destabilizing factor for other methods. The results are in very good agreement with the literature. When the viscous forces are increased with respect to the membrane elastic forces, three regimes are found for both flow cases. Our method allows a precise characterization of the critical parameters governing the transitions. Copyright © 2010 John Wiley & Sons, Ltd.
Subdomain radial basis collocation method for fracture mechanics
Authors: Wang Lihua , Chen Jiun‐Shyan , Hu Hsin‐Yun 
Published: March 2010

AbstractThe direct approximation of strong form using radial basis functions (RBFs), commonly called the radial basis collocation method (RBCM), has been recognized as an effective means for solving boundary value problems. Nevertheless, the non‐compactness of the RBFs precludes its application to problems with local features, such as fracture problems, among others. This work attempts to apply RBCM to fracture mechanics by introducing a domain decomposition technique with proper interface conditions. The proposed method allows (1) natural representation of discontinuity across the crack surfaces and (2) enrichment of crack‐tip solution in a local subdomain. With the proper domain decomposition and interface conditions, exponential convergence rate can be achieved while keeping the discrete system well‐conditioned. The analytical prediction and numerical results demonstrate that an optimal dimension of the near‐tip subdomain exists. The effectiveness of the proposed method is justified by the mathematical analysis and demonstrated by the numerical examples. Copyright © 2010 John Wiley & Sons, Ltd.
Imposing Dirichlet boundary conditions with Nitsche's method and spline‐based finite elements
Authors: Embar Anand , Dolbow John , Harari Isaac 
Published: March 2010

AbstractA key challenge while employing non‐interpolatory basis functions in finite‐element methods is the robust imposition of Dirichlet boundary conditions. The current work studies the weak enforcement of such conditions for B‐spline basis functions, with application to both second‐ and fourth‐order problems. This is achieved using concepts borrowed from Nitsche's method, which is a stabilized method for imposing constraints on surfaces. Conditions for the stability of the system of equations are derived for each class of problem. Stability parameters in the Nitsche weak form are then evaluated by solving a local generalized eigenvalue problem at the Dirichlet boundary. The approach is designed to work equally well when the grid used to build the splines conforms to the physical boundary of interest as well as to the more general case when it does not. Through several numerical examples, the approach is shown to yield optimal rates of convergence. Copyright © 2010 John Wiley & Sons, Ltd.
Stochastic simulations based on mixed finite elements for solute transport in groundwater
Authors: Radu Florin A. , Suciu Nicolae 
Published: March 2010

AbstractAn accurate mixed finite element method to solve both flow and transport is developed for stochastic simulations of transport in saturated aquifers characterized by random log‐hydraulic conductivity fields. The main advantage of the mixed finite element is that it is local mass conservative. Unlike in stochastic finite element methods, this approach yields concentration fields and concentration moments for samples of the random field. In this way, it will be possible to analyze the behavior of different ensemble average observables of the transport process as well as the behavior of their fluctuations. Results of the stochastic simulations described here can be used to assess the reliability for real cases of the ensemble average quantities provided by stochastic modeling of transport in groundwater. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A constitutive model for continuous fiber reinforced polymer plies
Authors: Flatscher Thomas , Schuecker Clara , Pettermann Heinz E. 
Published: March 2010

AbstractIn the present paper a constitutive model is reviewed which can be used to predict the non‐linear behavior of continuous fiber reinforced laminates with polymeric matrix materials. The constitutive model considers stiffness degradation and plastic strain accumulation at the length scale of the individual plies (laminae). These effects are modeled via two different phenomenological approaches, however, their interaction is considered when the constitutive equations are solved by an implicit integration scheme. To demonstrate the predictive capabilities of the individual model parts, examples are given where the above mentioned effects are decoupled. This way, their impact on the laminate's response can be studied independently. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A multiphase finite element simulation of biological conversion processes in landfills
Authors: Ricken Tim , Robeck Markus , Widmann Renatus 
Published: March 2010

AbstractWorldwide, landfills are the most common way to dispose of waste, but have an impact on the environment as a result of harmful gas and leachate production. Estimating the long‐term behaviour of a landfill in regard to this gas production and organic degrading, as well as to settlement and waste water production, is of high importance. Therefore, a model has been developed to simulate these processes. This constitutive model is based on the multiphase Theory of Porous Media. The body under investigation consists of an organic and an inorganic phase as well as a liquid and a gas phase. The equations of the model are developed on the basis of a consistent thermo‐mechanical approach including the momentum balance for the solid phase and the mixture, the energy balance for the mixture and the mass balance for the gas phase. All interactions between the constituents such as mass transfers, interaction forces and energy fluxes are taken into consideration. The strongly coupled set of partial differential equations is implemented in the finite element code FEAP. The theoretical framework and the results of meantime successfully performed simulation of a real landfill body will be shown. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inverse dynamics of underactuated multibody systems
Authors: Quasem Mahmud , Uhlar Stefan , Betsch Peter 
Published: March 2010

AbstractThe present work deals with controlled 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 governing equations of motion can be written in the form of differential‐algebraic equations (DAEs) with a mixed set of holonomic and control constraints. The rotationless formulation of multibody dynamics will be considered [1]. 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 [2]. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Research about moving restrictions of cervical spine under the action of mechanical vibrations
Authors: Truţa Aurica , Arghir Mariana 
Published: March 2010

AbstractThe cervical spine is very important human body part, because it sustains the head and it has a higher mobility than the other parts of human spine. The vibration could influence the work performance but also could have a negative influence on human body health. There are many elements, which could be damaged: eyes, ears, brain, mandible, neck's muscle, C1 to C7 vertebras. When the operator is exposed to vibrations for a long time, he can fill a strong pain at the neck. Injuries to the cervical spine are common at the level of the second cervical vertebrae, but neurological injury is uncommon. If it does occur, however, it may cause death or profound disability, including paralysis of the arms or legs. We purpose in this study to develop a biomechanical model for the cervical vertebras and identify the influence of mechanical vibrations on human cervical spine and human head. For this study is necessary to compute the entire moving system of the neck‐head. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mathematical study of a tissue‐implant connection in a ventral hernia repair in a context of the system's parameters
Authors: Lubowiecka I. , Szymczak C. , Tomaszewska A. , Śmietański M. 
Published: March 2010

AbstractVentral hernia repair is nowadays a well recognized matter in surgery and advanced techniques of operating are developed. However, mechanical properties of the system after an operation are not known so recurrences of the illness happen. The paper describes a simple mathematical model of a human fascia‐synthetic implant system. The synthetic mesh is modeled by a cable structure and its elastic supports simulate the human fascia. The junction force in the fascia‐implant system is sought. A relation of the force change to variations of some parameters of the system is also studied by applying a sensitivity analysis. The authors conclude that a crucial role for the junction force and a patient's comfort plays the implant's elasticity modulus and initial tension of the mesh is the least important factor. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Visualization of the Motion of the Human Spine in the Context of Gait Analysis through Splines
Authors: Rosenthal Dietmar , Kecskeméthy Andrés 
Published: March 2010

AbstractThe present paper describes an approach for the reconstruction of the motion of the human spine based on marker tracking. The approach uses a spline curve of fifth degree to reproduce the contour of the central marrow line and a set of virtual sliders along the spline with fixed offset distances which model external markers including skin motion. The fitting process is formulated as an optimization problem minimizing the quadratic error between the tips of the sliders and the measured marker positions. The paper also discusses some simplifications of this approach. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of stage I‐crack growth using a 3D‐model
Authors: Köster Philipp , Fritzen Claus‐Peter , Knobbe Helge , Christ Hans‐Jürgen , Krupp Ulrich 
Published: March 2010

AbstractA three‐dimensional model for stage I‐short crack propagation on a single slip plane is presented. It considers elastic plastic material behaviour by allowing sliding on the active slip plane in a defined slip direction. A crack propagation law based on the crack tip slide displacement is implemented to simulate crack propagation. The model is solved numerically using the dislocation loop technique. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Closed‐form analysis of a higher‐order composite box beam theory
Authors: Kroker Andreas M. , Becker Wilfried 
Published: March 2010

AbstractA higher‐order theory is developed for composite box beams with rectangular, closed cross‐sections. Each cross‐section is therefore divided into two flanges and webs. Displacement representations are chosen for each part separately. The in‐plane kinematics is 2nd order for the flanges and even 3rd order for the webs. The kinematics of the four parts is interconnected with the help of geometric coupling. All in‐plane stress components can be obtained directly by using a reduced stiffness matrix for each single layer. The layups of the laminates for the flanges and webs are independent from each other. Only a symmetric layup with balanced angles is necessary. The determined differential equation system of 2nd order including four independent functions can be solved completely in a closed‐form analytical manner. As an actual example a cantilever beam under combined bending moment and transverse force is considered. The results obtained by this new theory are compared with the results of a FEM‐model with a very fine shell element discretization. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Load Monitoring of Impacted Carbon‐Fibre‐Reinforced Plastic Plates
Authors: Ungethuem Andy , Lammering Rolf 
Published: March 2010

AbstractThis work deals with a new wave migration model for the determination of an impact location for non‐isotropic plates. The method is based on the wave propagation after the impact. The evaluation and processing of the signals of at least four sensors allow for the calculation of the impact location from the runtime of the signals. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The rotating elastic‐plastic hollow shaft heated at its inner surface
Authors: Arslan Eray , Mack Werner , Eraslan Ahmet N. 
Published: March 2010

AbstractBased on Tresca's yield criterion and the flow rule associated with it, the behaviour of a rotating linearly strain‐hardening elastic‐plastic hollow shaft heated at its inner surface is studied. Moreover, the residual stresses at stand‐still are depicted. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)