Numerical simulation of fracture of model Al-Si alloys
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I. INTRODUCTION
AL-SI alloys, among elastic-plastic materials, find wide applications in automotive and aircraft industries due to their good mechanical performance and excellent physical properties. These applications demand a high crack-growth resistance of components made of these alloys, since the crack-growth and fracture problems, which are unavoidable in service for engineering materials, concern the lifetime of components and even human safety in certain key applications. As a result, much research has been conducted in an attempt to improve their fracture properties.[1–5] Fracture resistance has been found to be largely dependent upon the alloy’s microstructure, especially the size, shape, and distribution of its constituents. Ductile materials can be studied with elastic-plastic fracture mechanics, provided that appropriate specimen dimensions are employed. Typical and feasible evaluation experiments include the measurement of the critical J-integral and critical crack tip opening displacement, which have been proven successful in materials science. With the rapid development of computer techniques, elasticplastic fracture mechanics, and materials science, a large number of investigations have been carried out, concentrated mainly on deformation behavior and stress and strain analyses of loaded materials by means of numerical approaches such as the finite-element and boundary-element methods.[6–10] Recently, numerical simulations have also been shown to be popular and powerful tools in modeling and understanding the fracture-related problems in engineering applications.[11–19] However, most of the numerical analyses for LIHE QIAN, Research Fellow, HIROYUKI TODA, Associate Professor, TOSHIKAZU AKAHORI, Research Associate, and MITSUO NIINOMI and TOSHIRO KOBAYASHI, Professors, are with the Department of Production Systems Engineering, Toyohashi University of Technology, Toyohashi 441-8580, Japan. Contact e-mail: [email protected] or dlhqian@ yahoo.com SEISHI NISHIDO, Assistant Manager, is with the Technical Centre, Aisin Takaoka Co. Ltd., Takaokashin-machi, Toyota 473-8501, Japan. Manuscript submitted April 3, 2005. METALLURGICAL AND MATERIALS TRANSACTIONS A
evaluation of crack problems were confined to brittle and small-scale-yielding elastic-plastic uniform materials.[11–15] When a real multiphase microstructure of the material is considered, the simulation of a continuous crack-growth path is even limited. Gao and Rice[16] and Bower and Ortiz[17] simulated the crack-growth behavior in particle-dispersed brittle composites using perturbation analysis. In their analysis, however, a self-similar crack-growth behavior was presumed, giving rise to a penetration of the crack into the particle whenever the crack meets a particle; it was assumed that when the fracture resistance of the particle is higher than that of the matrix, crack growth is retarded by the particle and crack trapping occurs. The assumption of crack growth in an in-plane manner should not be valid in most engineering materials. In a r
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