Spandan Maiti¹, Philippe H. Geubelle¹

CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.2, pp. 91-102, 2004, DOI:10.3970/cmes.2004.005.091

Abstract The dynamic propagation and branching of a mode I crack in polycrystalline brittle materials like ceramics are investigated numerically using a 2-D explicit grain-based cohesive/volumetric finite element scheme. The granular microstructure of the ceramics is taken into account and the crack is restricted to propagate along the grain boundaries. Special emphasis is placed on studying the effect of grain size and cohesive parameters on the crack branching instability. More >

A. Rama Chandra Murthy¹, G.S. Palani¹, Nagesh R. Iyer¹

CMC-Computers, Materials & Continua, Vol.1, No.4, pp. 289-300, 2004, DOI:10.3970/cmc.2004.001.289

Abstract In this paper an improved Wheeler residual stress model has been proposed for remaining life assessment of cracked plate panels under variable amplitude loading (VAL). The improvement to the Wheeler residual stress model is in terms of the expressions for the shaping exponent, which is generally obtained through experiments. Simple expressions for the computation of shaping exponent have been proposed for compact tension (CT) specimen and plate panels with a center crack or an edge crack. The remaining life assessment has been carried out by employing linear elastic fracture mechanics (LEFM) principles. In the present… More >

S. Tchouikov¹, T. Nishioka¹, T. Fujimoto¹

CMC-Computers, Materials & Continua, Vol.1, No.2, pp. 191-204, 2004, DOI:10.3970/cmc.2004.001.191

Abstract Phenomena of dynamic crack branching are investigated numerically from a macroscopic point of view. Repetitive branching phenomena, interaction of cracks after bifurcation and their stability, bifurcation into two and three branches were the objectives of this research. For the analysis of dynamic crack branching, recently we developed moving finite element method based on Delaunay automatic triangulation [Nishioka, Furutuka, Tchouikov and Fujimoto (2002)]. In this study this method was extended to be applicable for complicated crack branching phenomena, such as bifurcation of the propagating crack into more than two branches, multiple crack bifurcation and so on. More >

Tong-Yi Zhang¹

CMC-Computers, Materials & Continua, Vol.1, No.1, pp. 107-116, 2004, DOI:10.3970/cmc.2004.001.107

Abstract The present work presents a strip Dielectric Breakdown (DB) model for an electrically impermeable crack in a piezoelectric material. In the DB model, the dielectric breakdown region is assumed to be a strip along the crack's front line. Along the DB strip, the electric field strength is equal to the dielectric breakdown strength. The DB model is exactly in analogy with the mechanical Dugdale model. Two energy release rates emerge from the analysis. An applied energy release rate appears when evaluating J-integral along a contour surrounding both the dielectric breakdown strip and the crack tip, whereas More >

E. Ferretti¹

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.3, pp. 227-244, 2004, DOI:10.3970/cmes.2004.006.227

Abstract Defining the crack path in brittle and non-brittle crack is not easy, due to several unknowns. If the direction of crack propagation can be computed by means of one of the existing criteria, it is not known whether this direction will remain constant during crack propagation. A crack initiation leads to an enhanced stress field at crack tip. During propagation, the enhanced tip stress field propagates into the solid, locally interacting with the pre-existing stress field. This interaction can lead to modifications of the propagation direction, depending on the domain and crack geometry. Moreover, trajectory… More >

J. A. Nairn¹

CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.6, pp. 649-664, 2003, DOI:10.3970/cmes.2003.004.649

Abstract A new algorithm is described which extends the material point method (MPM) to allow explicit cracks within the model material. Conventional MPM enforces velocity and displacement continuity through its background grid. This approach is incompatible with cracks which are displacement and velocity discontinuities. By allowing multiple velocity fields at special nodes near cracks, the new method (called CRAMP) can model cracks. The results provide an ``exact'' MPM analysis for cracks. Comparison to finite element analysis and to experiments show it gets good results for crack problems. The intersection of crack surfaces is prevented by implementing More >

Ch. Zhang², A. Savaidis³

CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.5, pp. 603-618, 2003, DOI:10.3970/cmes.2003.004.603

Abstract A novel non-hypersingular time-domain traction BEM is presented for three-dimensional (3-D) transient elastodynamic crack analysis. The initial-boundary value problem is formulated as a set of non-hypersingular time-domain traction boundary integral equations (BIEs). To solve the time-domain traction BIEs, a time-stepping scheme based on the convolution quadrature formula of Lubich (1988a,b; 1994) for temporal discretization and a collocation method for spatial discretization is adopted. Numerical examples are given for an unbounded solid with a penny-shaped crack under a tensile and shear impact loading. A comparison of the present time-domain BEM with the conventional one shows that More >

E. Ferretti¹

CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.1, pp. 51-72, 2003, DOI:10.3970/cmes.2003.004.051

Abstract A numerical code for modeling crack propagation using the cell method is proposed. The Mohr-Coulomb criterion is used to compute the direction of crack propagation, and the new crack geometry is realized by an intra-element propagation technique. Automatic remeshing is then activated. Applications in Mode I and Mixed Mode are presented to illustrate the robustness of the implementation. More >

R. C. Batra¹, H.-K. Ching¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.6, pp. 717-730, 2002, DOI:10.3970/cmes.2002.003.717

Abstract The Meshless Local Petrov-Galerkin (MLPG) method is used to analyze transient deformations near either a crack or a notch tip in a linear elastic plate. The local weak formulation of equations governing elastodynamic deformations is derived. It results in a system of coupled ordinary differential equations which are integrated with respect to time by a Newmark family of methods. Essential boundary conditions are imposed by the penalty method. The accuracy of the MLPG solution is established by comparing computed results for one-dimensional wave propagation in a rod with the analytical solution of the problem. Results… More >

Z. D. Han¹, S. N. Atluri¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.6, pp. 699-716, 2002, DOI:10.3970/cmes.2002.003.699

Abstract As shown in an earlier work, the FEM-BEM alternating method is an efficient and accurate method for fracture analysis. In the present paper, a further improvement is formulated and implemented for the analyses of three-dimensional arbitrary surface cracks by modeling the cracks in a local finite-sized subdomain using the symmetric Galerkin boundary element method (SGBEM). The finite element method is used to model the uncracked global (built-up) structure for obtaining the stresses in an otherwise uncracked body. The solution for the cracked structural component is obtained in an iteration procedure, which alternates between FEM solution More >