The use of finite extension strain energy release rates in fracture of interfacial cracks

The existing solutions for interfacial cracks in bimaterial media obtained from the contact model and oscillatory model were compared. The oscillatory near tip stress field was found to agree very well with that of the contact model except for the extremely small contact zone. Using the oscillatory solution, Mode I and Mode II ''strain energy release rates'' for finite crack extensions were obtained in terms of the stress intensity factors and the assumed crack extension Delta a. Finite elements in conjunction with the crack closure method were used to calculate these ''strain energy release rates'' from which accurate stress intensity factors were obtained. An alternative and efficient method based on crack surface displacement ratio was also introduced to obtain stress intensity Factors. Non-oscillatory (Delta a-independent) Mode I and Mode II ''strain energy release rates'' were proposed to provide an alternate measure of fracture mode mixity or to be used as a fracture criterion for interfacial cracks. (C) 1997 Elsevier Science Ltd.