Fracture in forming

The formation of cracks in metalworking processes is considered from both the metallurgical and mechanics points of view. Stress and strain states are shown to be important, and hydrostatic stress figures prominently in the coalescence of voids initiated at inclusions or hard second phases. Changes of stress or strain ratio during an operation can have a profound effect on cracking, as illustrated by fracture following neck formation in sheet materials. Conditions for cracking in triaxial stress states will be of interest to those requiring fracture criteria for large-deformation finite-element calculations.