Experimental T_(33)-stress formulation of test specimen thickness effect on fracture toughness in the transition temperature region

摘要

This paper describes a study of the test specimen thickness effect on fracture toughness of a material, in the transition temperature region, for CT specimens. In addition we studied the specimen thickness effect on the T_(33)-stress (the out-of-plane non-singular term in the ser-ies of elastic crack-tip stress fields), expecting that T33-stress affected the crack-tip triaxi-ality and thus constraint in the out-of-plane direction. Finally, an experimental expression for the thickness effect on the fracture toughness using T_(33)-stress is proposed for 0.55% car-bon steel S55C. In addition to the fact that T_(33) (which was negative) seemed to show an upper bound for large B/W, these results indicate the possibility of improving the existing methods for correlating fracture toughness obtained by test specimen with the toughness of actual cracks found in the structure, using T_(33)-stress.