PROCESS ZONE FRACTURE CRITERIA FOR CRACK TIPS

The further development of the local stress, strain or energy density criteria is considered necessary in respect of the crack initiation in a process zone outside the original crack or slit tip. Specific crite ria are proposed for brittle and ''ductile'' crack initiation. The rel evant limit value formulae are developed and the results shown for sup erimposed K-I- and K-II-loading. The curves designating critical K-I-K -II-conditions including process zone angles and cracking angles are c ompared with the curves from conventional criteria. A simplified versi on of the process zone criteria may be used in engineering application s without major loss of accuracy. The results are finally compared wit h those from the ASME Code procedure of crack assessment.