Computational micromechanics analysis of cyclic crack-tip behavior for micro structurally small cracks in dual-phase Al-Si alloys

Cracks were simulated to grow through the Al-rich matrix and around silicon particles. The results showed that as the crack approached the particle, t he maximum plastic shear strain range at the crack-tip reduced due to the b lockage mechanism proposed by microstructural fracture mechanics. However, as the crack advanced even nearer to the particle, the plastic shear strain range increased rapidly. The latter has been interpreted in terms of geome trically necessary dislocation plasticity. Although the crack-tip opening d isplacement (CTOD) for a long initial crack length was much greater than th at of an initially short crack, once both cracks engaged 2-3 silicon partic les, the difference in CTOD was reduced; and they followed a common retarda tion pattern. This phenomenon has been explained by the strong shielding ef fects of particle clusters on the fatigue crack propagation. These results offered additional insight into commonly observed small crack behavior. (C) 2001 Elsevier Science Ltd. All rights reserved.