R. Springhetti¹, G. Novati¹, M. Margonari²

CMES-Computer Modeling in Engineering & Sciences, Vol.13, No.1, pp. 67-80, 2006, DOI:10.3970/cmes.2006.013.067

Abstract With reference to potential and elastostatic problems, a BEM-FEM coupling procedure, based on the symmetric Galerkin version of the BEM, is developed; the continuity conditions at the interface of the BE and FE subdomains are enforced in weak form; the global linear system is characterized by a symmetric coefficient matrix. The procedure is numerically tested with reference first to 2D potential problems and successively to 3D elastoplastic problems (with plastic strains confined to the FE subdomain). More >

G.A. Gravvanis¹, K.M. Giannoutakis¹

CMES-Computer Modeling in Engineering & Sciences, Vol.16, No.2, pp. 69-82, 2006, DOI:10.3970/cmes.2006.016.069

Abstract A new class of normalized explicit optimized approximate inverse finite element matrix techniques, based on normalized finite element approximate factorization procedures, for solving sparse linear systems resulting from the finite element discretization of partial differential equations in three space variables are introduced. A new parallel normalized explicit preconditioned conjugate gradient square method in conjunction with normalized approximate inverse finite element matrix techniques for solving efficiently sparse finite element linear systems on distributed memory systems is also presented along with theoretical estimates on speedups and efficiency. The performance on a distributed memory machine, using Message Passing More >

Taeyoung Ha¹, Sangwon Seo², Dongwoo Sheen³

CMES-Computer Modeling in Engineering & Sciences, Vol.14, No.1, pp. 57-76, 2006, DOI:10.3970/cmes.2006.014.057

Abstract We present nonoverlapping domain decomposition methods for the approximation of both electromagnetic fields in a three-dimensional bounded domain satisfying absorbing boundary conditions. A Seidel-type domain decomposition iterative method is introduced based on a hybridization of a nonconforming mixed finite element method. Convergence results for the numerical procedure are proved by introducing a suitable pseudo-energy. The spectral radius of the iterative procedure is estimated and a method for choosing an optimal matching parameter is given. A red-black Seidel-type method which is readily parallelizable is also introduced and analyzed. Numerical experiments confirm that the presented algorithms are faster than More >

D. H. Pahr¹, F.G. Rammerstorfer¹

CMES-Computer Modeling in Engineering & Sciences, Vol.12, No.3, pp. 229-242, 2006, DOI:10.3970/cmes.2006.012.229

Abstract Sandwich structures are efficient lightweight materials. Due to there design they exhibit very special failure modes such as global buckling, shear crimping, facesheet wrinkling, facesheet dimpling, and face/core yielding. The core of the sandwich is usually made of foams or cellular materials, e.g., honeycombs. Especially in the case of honeycomb cores the correlation between analytical buckling predictions and experiments might be poor (Ley, Lin, and Uy (1999)). The reason for this lies in the fact that analytical formulae typically assume a homogeneous core (continuous support of the facesheets). This work highlights problems of honeycomb core… More >

T. Fujimoto¹ and T. Nishioka¹

CMES-Computer Modeling in Engineering & Sciences, Vol.11, No.2, pp. 91-102, 2006, DOI:10.3970/cmes.2006.011.091

Abstract In the dynamic fracture of metallic material, some cracks propagate with the incidence of plastic deformation, and distinct plastic strain remains near the post-propagation area. In order to elucidate these dynamic nonlinear fracture processes, the moving finite element method is developed for nonlinear crack propagation. The T* integral is used as the parameter to estimate crack tip condition. First, the effect of material viscosity and crack propagation velocity have been discussed based on the numerical results for fracture under pure mode I high speed loading. Under mixed mode loading, numerical simulations for fracture path prediction More >

G.P. Nikishkov¹

CMES-Computer Modeling in Engineering & Sciences, Vol.11, No.2, pp. 81-90, 2006, DOI:10.3970/cmes.2006.011.081

Abstract This paper presents the object oriented approach to programming the finite element method using the Java language. The developed finite element code consists of ten Java packages. Three main methods are related to generation of finite element models, solution of elastic and elastic-plastic boundary value problems, and visualization of models and solution results. Object-oriented model of the code is described. It is demonstrated that Java 1.5 new features are useful in development of the finite element code. Java 3D is used for visualization of models and results. More >

G. Mishuris¹, A. Öchsner², G. Kuhn³

CMC-Computers, Materials & Continua, Vol.4, No.3, pp. 137-152, 2006, DOI:10.3970/cmc.2006.004.137

Abstract Nonclassical transmission conditions for dissimilar elastic structures with imperfect interfaces are investigated. The thin interface zone is assumed to be soft or stiff in comparison with the bonded materials and the transmission conditions for stiff interfaces are evaluated based on asymptotic analysis. The accuracy of the transmission conditions is clarified not only in terms of asymptotic estimate, but, which is especially important for users, also in values by accurate FEM calculations. The ranges of applicability of the conditions are discussed. More >

T. Nishioka¹, S. Tchouikov¹, T. Fujimoto¹

CMC-Computers, Materials & Continua, Vol.3, No.3, pp. 147-154, 2006, DOI:10.3970/cmc.2006.003.147

Abstract In this study, phenomena of multiple branching of dynamically propagating crack are investigated numerically. The complicated paths of cracks propagating in a material are simulated by moving finite element method based on Delaunay automatic triangulation (MFEM BODAT), which was extended for such problems. For evaluation of fracture parameters for propagating and branching cracks switching method of the path independent dynamic J integral was used. Using these techniques the generation phase simulation of multiple dynamic crack branching was performed. Various dynamic fracture parameters, which are almost impossible to obtain by experimental technique alone, were accurately evaluated. More >

Lingfei Gao¹, Xiaoping Zheng^1,2, Zhenhan Yao¹

CMC-Computers, Materials & Continua, Vol.3, No.1, pp. 25-36, 2006, DOI:10.3970/cmc.2007.003.025

Abstract A general numerical approach is developed to model the elastic behaviours and failure processes of heterogeneous materials. The heterogeneous material body is assumed composed of a large number of convex polygon lattices with different phases. These phases are locally isotropic and elastic-brittle with the different lattices displaying variable material parameters and a Weibull-type statistical distribution. When the effective strain exceeds a local fracture criterion, the full lattice exhibits failure uniformly, and this is modelled by assuming a very small Young modulus value. An auto-select loading method is employed to model the failure process. The proposed More >

I. Smojver¹, J. Sorić²

CMC-Computers, Materials & Continua, Vol.3, No.1, pp. 13-24, 2006, DOI:10.3970/cmc.2007.003.013

Abstract The paper addresses the problem of impact on layered fibre composites. The behaviour of composite laminates under impact loading is dependent not only on the velocity but also on the mass and geometry of the impactor. Using micromechanical Mori-Tanaka approach, mechanical properties of the laminate have been calculated utilizing the material constants of the fibre and matrix. General purpose FEM software ABAQUS has been modified by means of user written subroutines for modelling of composite laminate and rigid impactor. The kinematics of the impact has been simulated using transient dynamic analysis. Employing user defined multi More >