Correlationship between JIC and equivalent fracture strain determined by small-punch tests in JN1, JJ1 and JK2 austenitic stainless steels Original Research Article

Small-punch (SP) and fracture toughness tests were conducted at 4 and 77 K on newly developed cryogenic austenitic stainless steels after isothermal aging. Equivalent fracture strain εqf was determined by measuring the reduction in thickness of SP specimens. A linear dependence of JIC on εqf was found for these new materials. Regression analysis of experimental data produced the linear relation: JIC=1304.1εqf+8.09 (kJ m−2). An analysis of the correlation was pursued on the basis of material properties and evaluation method of JIC. The results showed that the slope value was influenced by the JIC evaluation method. This linear relation enables the prediction of JIC to be made from the equivalent fracture strain εqf by conducting small punch tests. Thus, it is expected that the SP testing method provides a useful basis for assessing the degradation of fracture toughness in small areas, such as heat-affected zones in welded components.