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

摘要

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) = 1304.1 epsilon_(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 ~ 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 heat-affected zones in welded components.