THE USE OF FINITE EXTENSION STRAIN-ENERGY RELEASE RATES IN FRACTURE OF INTERFACIAL CRACKS

The existing solutions for interfacial cracks in bimaterial media obta ined from the contact model and oscillatory model were compared. The o scillatory near tip stress field was found to agree very well with tha t of the contact model except for the extremely small contact zone. Us ing the oscillatory solution, Mode I and Mode II ''strain energy relea se rates'' for finite crack extensions were obtained in terms of the s tress intensity factors and the assumed crack extension Delta a. Finit e elements in conjunction with the crack closure method were used to c alculate these ''strain energy release rates'' from which accurate str ess intensity factors were obtained. An alternative and efficient meth od based on crack surface displacement ratio was also introduced to ob tain stress intensity Factors. Non-oscillatory (Delta a-independent) M ode I and Mode II ''strain energy release rates'' were proposed to pro vide an alternate measure of fracture mode mixity or to be used as a f racture criterion for interfacial cracks. (C) 1997 Elsevier Science Lt d.