Finite element analysis of an interface crack with large crack-tip contact zones

There is considerable ambiguity regarding the limiting values of the strain energy release rate (SERR) components at the tips of a crack lying along the interface between two dissimilar isotropic media. In this paper this aspect is examined using finite element analysis and Modified Crack Closure Integral (MCCI) for a problem in which the material properties are chosen so as to cause a Large size crack-tip contact zone. By careful choice of this problem, interpenetration of the crack faces in the crack-tip contact zones is observed for the first time in the finite element analysis. Earlier solutions primarily on remote mode I loading reported that SERR components do not converge as the virtual crack extension Delta a-->0 and that these components show an oscillatory nature when Delta a is less than the contact zone size r(c). In the present work, multipoint constraints are imposed on crack face normal displacements in the contact zone and meaningful results are generated for both remote tension and shear loading cases. The apparent nonconvergence of the SERR components as Delta a-->0 can be explained if these components are considered as functions of Delta a, and Delta a is considered as the actual crack growth step size. Copyright (C) 1996 Elsevier Science Ltd.