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

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 epsilon(qf) was determined by measuring the reduction in thickness of SP specimens. A linear dependence of J(IC) on epsilon(qf) was found for these new materials. Regression analysis of experimental data produced the linear relation: J(IC) = 1304.1epsilon(qf) + 8.09 (kJ m(-2)). An analysis of the correlation was pursued on the basis of material properties and evaluation method of J(IC). The results Showed that the slope value was influenced by the J(IC) evaluation method. This linear relation enables the prediction of J(IC) to be made from the equivalent fracture strain epsilon(qf) 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 heataffected zones in welded components. (C) 2002 Elsevier Science Ltd. All rights reserved.