Damage evolution around shear loaded inter-void ligaments

The dimpled fracture surfaces observed in a post-mortem investigation of the ductile fracture indicates that the fracture formed through coalescing voids that originated at the microstructural level. The damage process is commonly described by the nucleation and growth of those voids, thinning the inter-void material ligaments, ultimately leading to final fracture. The final stages of the ductile fracture process will be discussed, with emphasis on the local plastic deformation field in the void's surroundings. This study considers dominant shear loading as the driving force for plastic deformation, using periodic cell calculations and the GTN model modified for shear damage. We systematically investigate plane strain and plane stress configurations, as a realization of the ligament thinning as part of the ductile fracture process. We suggest that the void surroundings and the intervoid ductile ligament undergoes an idealized gradual transition from plane strain to plane stress as the ligament gets increasingly thinner. While the present study addresses quasi-static failure, it is believed that the framework presented here can be extended to dynamic loading situations as well.