Finite element and analytical modelling of crack closure due to repeated overloads

In this paper, investigations of crack closure due to repeated overloads are presented using finite element (FE) and simplified analytical modelling approaches. In particular, attempts are made to study the effects of overload spacing on closure levels and the underlying physical mechanisms involved. Overload closure behaviour is functionally similar for both FE and analytical approaches used and is seen to be in reasonable accord with relevant available experimental observations. In the first instance, it is noted that for double overload interactions, crack closure influence of an initial overload upon the unloading conditions of a second overload can explain much of the observed enhancement in crack growth retardation; however, for successive (repeated) overloads in plane strain, a critical influence of in-plane constraint arises to attenuate closure interactions.