N. Ramakrishnan¹, P. Rama Rao²

CMC-Computers, Materials & Continua, Vol.2, No.3, pp. 163-176, 2005, DOI:10.3970/cmc.2005.002.163

Abstract Ductile fracture is initiated by void nucleation at a characteristic distance (I_c) from the crack tip and propagated by void growth followed by coalescence with the tip. The earlier concepts expressed I_c in terms of grain size or inter-particle distance because grain and particle boundaries form potential sites for void nucleation. However, Srinivas et al. (1994) observed nucleation of such voids even inside the crack tip grains in a nominally particle free Armco iron. In an attempt to achieve a unified understanding of these observations, typical crack-tip blunting prior to ductile fracture in a standard C(T) specimen… More >

J. Li, Z. H. Xiang, M. D. Xue¹

CMC-Computers, Materials & Continua, Vol.2, No.2, pp. 139-150, 2005, DOI:10.3970/cmc.2005.002.139

Abstract This paper investigates the buckling response of honeycomb sandwich composite shells with cutouts under axial compression. The Wilson's incompatible solid Finite Element (FE) is used around cutouts to obtain the detail stress distribution there. While to reduce the computational expense, a special multilayered relative degrees-of-freedom (DOF) shell FE is used to model the regions far from the cutouts. The efficiency and accuracy of this modeling scheme are illustrated by two benchmarks. Then parametric studies are carried out to reveal how the buckling response is influenced by the area, the shape and the orientation of cutouts. More >

D.S. Liu^1,2 , C.Y. Chen² , D.Y. Chiou³

CMES-Computer Modeling in Engineering & Sciences, Vol.9, No.2, pp. 179-192, 2005, DOI:10.3970/cmes.2005.009.179

Abstract A three-dimensional heterogeneous infinite element method (HIEM) for modeling inclusions with interphases in composite materials is presented. This special element is formulated based on the conventional finite element method (FEM) using the similarity stiffness property and matrix condensation operations. An HIE-FE coupling scheme is also developed and implemented using the commercial software ABAQUS to conduct the elastostatic analysis. The proposed approach was validated first to study heterogeneous material containing one spherical inclusion. The displacement and stress variations around the inclusion vicinity are verified against conventional FEM. The proposed approach was next applied to analyze the effective More >

H. Okada ¹, T. Kamibeppu ¹

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.3, pp. 229-238, 2005, DOI:10.3970/cmes.2005.010.229

Abstract In this paper, a three-dimensional VCCM (Virtual Crack Closure-Integral Method) for evaluating the energy release rate and the stress intensity factor is presented. Many engineers and researchers believe that hexahedral finite elements should be used to perform three-dimensional fracture analyses. Previous VCCM formulations assume the use of hexahedral finite elements. In present study, the authors have been developing a VCCM that works with tetrahedral finite elements. In the field of large-scale computation, the use of tetrahedral finite elements has becoming very popular as high performance mesh generation programs became available. Therefore, building a large and More >

Toshihisa Nishioka ¹,

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.3, pp. 209-216, 2005, DOI:10.3970/cmes.2005.010.209

Abstract Recent Advances in Numerical Simulation Technologies for Various Dynamic Fracture Phenomena are summarized. First, the basic concepts of fracture simulations are explained together with pertinent simulation results. Next, Examples of dynamic fracture simulations are presented. More >

J. Bielak¹, O. Ghattas², E.-J. Kim³

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.2, pp. 99-112, 2005, DOI:10.3970/cmes.2005.010.099

Abstract We present a parallel octree-based finite element method for large-scale earthquake ground motion simulation in realistic basins. The octree representation combines the low memory per node and good cache performance of finite difference methods with the spatial adaptivity to local seismic wavelengths characteristic of unstructured finite element methods. Several tests are provided to verify the numerical performance of the method against Green's function solutions for homogeneous and piecewise homogeneous media, both with and without anelastic attenuation. A comparison is also provided against a finite difference code and an unstructured tetrahedral finite element code for a More >

G. Mishuris¹, A. Öchsner², G. Kuhn³

CMC-Computers, Materials & Continua, Vol.2, No.4, pp. 227-238, 2005, DOI:10.3970/cmc.2005.002.227

Abstract FEM-evaluation of imperfect transmission conditions has been performed for a modelling problem of an elastic structure with a thin intermediate interface. Very good correlations with theoretical results have been obtained. Additionally, the possible error connected with introducing the transmission conditions instead of the intermediate zone has been estimated depending on mechanical properties of the zone. More >

C. Tapp¹, W. Hansel, C. Mittelstedt, W. Becker²

CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.6, pp. 563-574, 2004, DOI:10.3970/cmes.2004.005.563

Abstract A heuristic algorithm for the weight minimization of sandwich plates is presented. The method is based on a preexisting algorithm for the layerwise topology optimization of symmetric laminates under in-plane loads. The presented algorithm uses structural analyses based on finite elements and explicitly accounts for the special sandwich situation. During the optimization procedure the algorithm adds or subtracts material from the layers of the face sheets and the core of the sandwich plate in regions of high or low stresses respectively. The orientation angles of the layers of the sandwich facings are not varied inorder More >

Peter W. Chung¹, Raju R. Namburu², Brian J. Henz³

CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.1, pp. 45-62, 2004, DOI:10.3970/cmes.2004.005.045

Abstract A method is developed based on an additive modification to the first Lagrangian elasticity tensor to make the finite element method for hyperelasticity viable at the atomic length scale in the context of lattice statics. Through the definition of an overlap region, the close-ranged atomic interaction energies are consistently summed over the boundary of each finite element. These energies are subsequently used to additively modify the conventional material property tensor that comes from the second derivative of the stored energy function. The summation over element boundaries, as opposed to atom clusters, allows the mesh and More >

N. Chandra¹ and C. Shet

CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.1, pp. 21-34, 2004, DOI:10.3970/cmes.2004.005.021

Abstract Cohesive Zone Models (CZMs)\ are increasingly being used to simulate fracture and fragmentation processes in metallic, polymeric, ceramic materials and composites thereof. Instead of an infinitely sharp crack envisaged in linear elastic fracture mechanics, CZM assumes the presence of a fracture process zone where the energy is transferred from external work both in the forward and the wake regions of the propagating crack. In this paper, some of the mechanistic and computational issues in the application of CZM \ to model failure and fracture in real materials are discussed. In specific we address the issue More >