A Method of Evaluating Creep Crack Growth Rate for Creep Ductile Steel Using Small Punch Specimens with a Surface Crack

Abstract

An experimental method is proposed for evaluating the creep crack growth (CCG) rate by using small punch (SP) creep test specimens with an elliptic surface crack at the center of the specimen. Expressions for high-temperature crack tip fracture parameter Ct were developed in full creep regime, from small-scale creep to extensive creep condition, for the crack model employed in the experiments. The Ct equation was derived by using the existing solution of the stress intensity factor K and the J-integral. A series of cracked SP creep tests were conducted for various levels of constant loads and testing periods. An SP specimen with a sharp notch was used instead of a precracked specimen. Preliminary results showed the feasibility of the suggested method for evaluating the CCG properties of materials. The CCG rate obtained from the precracked SP tests was significantly lower than that obtained from conventional compact tension specimens.