MEASUREMENT OF CRACK CLOSURE POINTS DURING CYCLIC LOADING BY THE STRAIN INTERFERENCE METHOD

Effective stress intensity factor range DELTAK(eff) and J integral range DELTAJ, which are determined using the crack tip opening or closing point, have been considered as the reasonable parameters controlling crack propagation behavior. Therefore, the development of a simple and practical measurement method of crack tip opening and closing stress is considered to be important for the evaluation of crack propagation. In this study, for a center-cracked plate in the elastic-plastic condition, it is shown that the crack tip opening and closing points can be easily determined with the relationship between the nominal cyclic stresses and the local strains measured in the vicinity of the crack center. Then, this measurement method is compared with the results obtained by the finite element method calculation.