A Preliminary Assessment of the Use of the CTOD Criterion in Dynamic Fracture Mechanics

Summary

The use of dynamic fracture mechanics to predict unstable crack propagation and arrest is now well established for elastodynamic conditions. Advances in the technology are currently being made to cope with ductile and tough materials where the small-scale yielding assumption is not necessarily valid. The key element in this effort lies in identifying a crack tip parameter that controls a rapidly propagating crack. Because of its success in characterizing initiation and stable crack growth, the CTOD is an attractive candidate for use in analyses of unstable crack propagation as well. However, there are difficulties that make this usage more difficult in dynamic fracture mechanics than in the quasi-static regime. This paper first reviews the prior uses of the CTOD in elastic-plastic and dynamic fracture mechanics, with emphasis on the use of the collinear strip yield (Dugdale) model for crack tip plasticity. Then, some preliminary results obtained in a direct determination of this parameter for a fast propagating crack in 4340 steel are reported that illuminate some of the difficulties in dynamic-inelastic analyses.