On the J-Integral and Other Evaluation Methods of Elastic-Plastic Fracture Mechanics and on the Limits of Applicability of Linear-Elastic Fracture Mechanics

摘要

The critical stress intensity factor for the onset of crack extension was determined by means of linear-elastic fracture mechanics and the various methods of elastic-plastic fracture mechanics, with emphasis on the J-integral method. The specimens used varied in size and were prepared from three steels and two aluminum alloys. The investigations show that linear-elastic fracture mechanics are applicable to specimens far smaller than those stipulated in the standard. The J-integral can be used to determine the critical stress intensity factor for the onset of crack extension for even smaller specimens when crack propagation is ductile, regardless of specimen size. The other methods of elastic-plastic fracture mechanics used were the equivalent energy method and the Eftis and Liebowitz method. Both can also be used to determine the critical stress intensity for ductile crack propagation in small specimens.