Investigation on compliance method used for compact tensile specimens in fracture toughness tests of ductile materials

摘要

Rotation correction method of unloading compliance for a compact tensile (CT) specimen in the current test standards of ductile fracture toughness Jic (Chinese GB,ASTM and ISO) was under suspicion by tracing its source,and a new rotation correction of the compliance for the CT specimen was given by redefining measured compliance Cm and corrected compliance Cc.The rotation radius R of the specimen was investigated in detail by elasto-plastic finite element analysis,and it was found that the rotation center of the specimen is closed to the crack tip and does not locate at the center of the remaining ligament recommended by the standards.Due to little effect of the material constitutive relationship on R,a polynomial formula between R and a/w was given.Furthermore,a new formula with better accuracy to predict the crack length of the CT specimen was presented.