Application of Direct Current Potential Drop for the J-Integral vs. Crack Growth Resistance Curve Characterization

摘要

The dc potential drop (DCPD) technique has been applied to derive the J-integral versus crack growth resistance curve (J-R curve) for fracture toughness characterization of structural materials. The test matrix covered three materials including type 316LN stainless steels, Ni-based alloy 617, and one ferritic-martensitic steel, three specimen configurations including standard compact, single edge bend, and disk-shaped compact specimens, and temperatures ranging from 20 to 650°C. When compared with baseline J-R curves derived from the ASTM E1820-13 normalization method, the original J-R curves from the DCPD technique yielded much smaller J_Q values due to the influence of crack blunting, plastic deformation, etc., on potential drop. To compensate these effects, a new procedure for adjusting DCPD J-R curves was proposed. After applying the new adjustment procedure, the average difference in J_Q between the DCPD technique and the normalization method was only 5.2 % and the difference in tearing modulus was 7.4 %. These promising results demonstrate the applicability of the DCPD technique for J-R curve characterization especially in extreme environments, such as elevated temperatures, where the conventional elastic unloading compliance method faces considerable challenges.