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  • Open Access

    ARTICLE

    On the Modelling of Rate-Dependent Domain Switching in Piezoelectric Materials under Superimposed Stresses

    A. Arockiarajan1, A. Menzel2

    CMES-Computer Modeling in Engineering & Sciences, Vol.20, No.1, pp. 55-72, 2007, DOI:10.3970/cmes.2007.020.055

    Abstract To study rate-dependent properties of piezoelectric materials a micro-mechanically motivated model is applied in this work. The developed framework is embedded into a coupled three-dimensional finite element setting, whereby each element is assumed to represent one grain and, moreover, possesses a random initialisation of the underlying polarisation direction. Furthermore, an energy-based criterion is used for the initiation of the onset of domain switching and the subsequent propagation of domain wall motion during the switching process is modelled via a linear kinetics theory. The interaction between individual grains is thereby incorporated by means of a probabilistic More >

  • Open Access

    ARTICLE

    Development of Heat Input Estimation Technique for Simulation of Shell Forming by Line-Heating

    N. Osawa1, K. Hashimoto1, J. Sawamura1, J. Kikuchi2, Y. Deguchi2, T. Yamaura2

    CMES-Computer Modeling in Engineering & Sciences, Vol.20, No.1, pp. 43-54, 2007, DOI:10.3970/cmes.2007.020.043

    Abstract A new hypothesis regarding heat transmission during line heating is proposed. It states that the distribution of the temperature of the gas adjacent to the plate, TG, and the overall local heat transfer coefficient, α, depend only on the distance from the torch. An identification technique for TG and α is developed. The validity of the employed hypothesis and the proposed technique is demonstrated by comparing the measured and identified TG during a spot heating test. The plate temperature calculated by direct heat conduction analysis closely approximates the one measured for the spot and line heating tests, More >

  • Open Access

    ARTICLE

    A Posteriori Error Estimation and Adaptive Node Refinement for Fast Moving Least Square Reproducing Kernel (FMLSRK) Method

    Chany Lee1, Chang-Hwan Im2, Hyun-Kyo Jung3, Hong-Kyu Kim4, Do Wan Kim5

    CMES-Computer Modeling in Engineering & Sciences, Vol.20, No.1, pp. 35-42, 2007, DOI:10.3970/cmes.2007.020.035

    Abstract In the present study, a residual-based a posteriori error estimation for a kind of meshless method, called fast moving least square reproducing kernel (FMLSRK) method is proposed. The proposed error estimation technique does not require any integration cells in evaluating error norm but recovers the exact solutions in a virtual area defined by a dilation parameter of FMLSRK and node density. The proposed technique was tested on typical electrostatic problems with gird or random node sets and the simulation results show that the proposed error estimation technique can be applied to adaptive node refinement process More >

  • Open Access

    ARTICLE

    The Trefftz Boundary Method in Viscoelasticity

    Berardi Sensale Cozzano1, Berardi Sensale Rodríguez2

    CMES-Computer Modeling in Engineering & Sciences, Vol.20, No.1, pp. 21-34, 2007, DOI:10.3970/cmes.2007.020.021

    Abstract In this paper, the Trefftz method is applied to solve linear viscoelasticity problems in the time domain, using Trefftz elastic series and considering the viscoelastic components in each time domain as fictitious body forces. The direct application of the Trefftz method to elastic problems is typically constrained to those cases in which the Navier equation is homogeneous. In the presence of body forces, the method of the particular solution or the method of the generalized particular solution should be used, depending on whether the body forces are constant or not inside the considered domain. Many More >

  • Open Access

    ARTICLE

    FEM Analysis of Knife Penetration through Woven Fabrics

    L. Wang1, S. Zhang, W. M. Gao, X. Wang

    CMES-Computer Modeling in Engineering & Sciences, Vol.20, No.1, pp. 11-20, 2007, DOI:10.3970/cmes.2007.020.011

    Abstract In this paper, the penetration of a knife through a plain woven fabric is simulated with the finite element method to understand the process of stabbing and the mechanism of fiber breakage. The model focuses on the study of the deformation of individual yarns, and the effects of their material properties and fabric structure on the stabbing resistant force. The performance of the fabric is analyzed as a response of stabbing and the stress distributions in yarn transverse and longitudinal directions. An equation derived from energy and momentum conservations of the knife is proposed to More >

  • Open Access

    ARTICLE

    On the Efficiency of the Parallel-in-Time Finite Volume Calculation of the Unsteady Navier-Stokes Equations

    J. M. F. Trindade1, J. C. F. Pereira2

    CMES-Computer Modeling in Engineering & Sciences, Vol.20, No.1, pp. 1-10, 2007, DOI:10.3970/cmes.2007.020.001

    Abstract In this paper, we discuss the efficiency and speed-up of parallel-in-time calculations of the unsteady incompressible Navier-Stokes equations in a PC-cluster. The parallel-in-time method is based on the alternate use of coarse global sequential solvers with fine local parallel ones in an iterative predictor-corrector fashion. Therefore, the efficiency of parallel calculations is strongly dependent on the number of iterations required for convergence. The one-dimensional scalar transport equation and the two-dimensional incompressible unsteady form of the Navier-Stokes equations were used to conduct numerical experiments to derive some conclusions concerning the accuracy and convergence of the iterative… More >

  • Open Access

    ARTICLE

    Fracture Analyses in Continuously Nonhomogeneous Piezoelectric Solids by the MLPG

    J. Sladek1, V. Sladek1, Ch. Zhang2, P. Solek3, L. Starek3

    CMES-Computer Modeling in Engineering & Sciences, Vol.19, No.3, pp. 247-262, 2007, DOI:10.3970/cmes.2007.019.247

    Abstract A meshless method based on the local Petrov-Galerkin approach is proposed for crack analysis in two-dimensional (2-D) and three-dimensional (3-D) axisymmetric piezoelectric solids with continuously varying material properties. Axial symmetry of geometry and boundary conditions reduces the original 3-d boundary value problem into a 2-d problem. Stationary problems are considered in this paper. The axial cross section is discretized into small circular subdomains surrounding nodes randomly spread over the analyzed domain. A unit step function is used as the test functions in the local weak-form. Then, the derived local integral equations (LBIEs) involve only contour-integrals More >

  • Open Access

    ARTICLE

    In Vivo/Ex Vivo MRI-Based 3D Non-Newtonian FSI Models for Human Atherosclerotic Plaques Compared with Fluid/Wall-Only Models

    Chun Yang1, Dalin Tang2, Chun Yuan3, Thomas S. Hatsukami4, Jie Zheng5, Pamela K. Woodard5

    CMES-Computer Modeling in Engineering & Sciences, Vol.19, No.3, pp. 233-246, 2007, DOI:10.3970/cmes.2007.019.233

    Abstract It has been recognized that fluid-structure interactions (FSI) play an important role in cardiovascular disease initiation and development. However, in vivo MRI multi-component FSI models for human carotid atherosclerotic plaques with bifurcation and quantitative comparisons of FSI models with fluid-only or structure-only models are currently lacking in the literature. A 3D non-Newtonian multi-component FSI model based on in vivo/ex vivo MRI images for human atherosclerotic plaques was introduced to investigate flow and plaque stress/strain behaviors which may be related to plaque progression and rupture. Both artery wall and plaque components were assumed to be hyperelastic,… More >

  • Open Access

    ARTICLE

    Improved Velocity Projection for the Material Point Method

    P. C. Wallstedt1, J. E. Guilkey1

    CMES-Computer Modeling in Engineering & Sciences, Vol.19, No.3, pp. 223-232, 2007, DOI:10.3970/cmes.2007.019.223

    Abstract The standard velocity projection scheme for the Material Point Method (MPM) and a typical form of the GIMP Method are examined. It is demonstrated that the fidelity of information transfer from a particle representation to the computational grid is strongly dependent on particle density and location. In addition, use of non-uniform grids and even non-uniform particle sizes are shown to introduce error. An enhancement to the projection operation is developed which makes use of already available velocity gradient information. This enhancement facilitates exact projection of linear functions and reduces the dependence of projection accuracy on More >

  • Open Access

    ARTICLE

    A Modified Method of Fundamental Solutions with Source on the Boundary for Solving Laplace Equations with Circular and Arbitrary Domains

    D.L. Young1, K.H. Chen2, J.T. Chen3, J.H. Kao4

    CMES-Computer Modeling in Engineering & Sciences, Vol.19, No.3, pp. 197-222, 2007, DOI:10.3970/cmes.2007.019.197

    Abstract A boundary-type method for solving the Laplace problems using the modified method of fundamental solutions (MMFS) is proposed. The present method (MMFS) implements the singular fundamental solutions to evaluate the solutions, and it can locate the source points on the real boundary as contrasted to the conventional MFS, where a fictitious boundary is needed to avoid the singularity of diagonal term of influence matrices. The diagonal term of influence matrices for arbitrary domain can be novelly determined by relating the MFS with the indirect BEM and are also solved for circular domain analytically by using More >

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