Combined macroscopic and microscopic approach to the fracture of metals. Technical annual progress report, 1979-1980

The following results are reported: (1) extremely good theoretical-experimental correlation was found between our theoretical predictions based on asymptotic analysis with numerical finite element studies and the experimentally monitored crack growth for a large range of stable crack growth in 4140 steel; (2) a theoretical model was developed for the critical conditions of crack initiation at rigid particles as a precursor of ductile rupture in steels; (3) as part of environmentally sensitive fracture mechanisms, it was found that hydrogen can promote a ductile-to-brittle fracture transition with increasing charging current density in low carbon steel; and (4) a new variational principle has been established for the combined processes of plastic creep flow and grain boundary diffusion and has been constructively applied to the problem of cavity growth under creep conditions.