Impact fracture analysis of functionally gradient bi-material interface with weak/micro-discontinuity
功能梯度双材料弱/微间断界面的冲击断裂分析

The concepts are clarified and a classification is suggested with respect to the strong-discontinuous, weak-discontinuous, micro-discontinuous and all-continuous interfaces. A mechanical model is estabhshed for impact fracture problems of functionally gradient elastic bi-material interfaces with weak discontinuity. Integral transform is used to derive Cauchy singular integral equation for the crack, and the allocation method is used to obtain numerical solutions. It is indicated that, the weak discontinuity and the micro-discontinuity have significant effects on stress intensity factors, and the micro-discontinuity is a kind of connection of interfacial mechanical property better than the weak discontinuity. By assuming the mechanical property of the FGM at one side of the interface to be the lower-rank terms of Taylor series with respect to that at the other side, the interface will become micro-discontinuous. The first rank micro-discontinuity is enough to reduce the stress intensity factors notably, however, the higher-rank terms, which are equal to or higher than the second rank, have less effect on stress intensity factors. To reduce the weak discontinuity or to make the interface microdiscontinuous are all beneficial to the enhancement of the capacity of the FGMs interface to resist impact fracture, i.e. to the enhancement of the interfacial toughness.