CRACK-TIP OPENING DISPLACEMENT OF A GRIFFITH CRACK AT A BIMATERIAL INTERFACE

Abstract

The problem of a crack lying along the interface of two dissimilar materials is of practical importance. It is well known that crack-tip stress field near an interface crack has a typical oscillating square root singularity. In fact, crack opening displacement (COD) for an interface crack is also. of oscillating type leading to physically unrealizable conditions like crack- surface interpenetration. The interface crack is characterized by a complex Stress Intensity Factor (SIF) and hence a possible fracture criterion may be some unknown function of the real and imaginary parts of the complex Stress Intensity Factor. Inadequacy of Linear Elastic Fracture Mechanics (LEFM) in tackling these problems necessitates the use of models incorporating crack-tip plasticity. In the present work a Dugdale type of plastic zone has been assumed. The size of the plastic zone as well as crack-tip opening displacement (CTOD) for a Griffith crack at a bi-material interface have been obtained. The results have been presented for different commonly encountered bi-materials. The results have also been presented in terms of physically meaningful non-dimensional parameters. It is concluded that size of the plastic zone is quite insensitive to the bi-material properties whereas, CTOD is very sensitive to them. CTOD is expected to serve as a simple one parameter criterion as compared to the two parameter criterion in terms of Stress Intensity Factors.