An evaluation of the fracture resistance of a stably growing crack by crack energy density. 5th report Comparison with the fracture resistances evaluated by CTOD and CTOA.

Abstract

In the previous reports, an experimental method to evaluate the fracture resistance of a stably growing crack by crack energy density was proposed, and its applicability and superiority were shown through the applications of the method to the stable crack growth problems of thin plates and the comparison with the fracture resistances evaluated by the J-integral. In this report, experiments on the stable growth fractures of thin plates are carried out, the fracture resistances evaluated by CTOD and CTOA are obtained, and they are compared with prior fracture resistances evaluated by crack energy density. The results are as follows : (1) Both show a similar tendency in their variations with crack extensions as was expected theoretically. (2) In comparison with the latter, the former are scattered because of the difficulty of the measurement of local deformation around a crack tip. Therefore, the proposed method is superior to the method based on CTOD and CTOA in the ease of the measurement of these quantities necessary for evaluation. The validity of the instability criterion on crack extension proposed before is also shown ion the Appendix.