Abstract Structural integrity assessment of flawed pipes, as required by ASME B&PV Code Section XI, relies on failure stress calculated by the Limit Load Criterion (LLC). The failure stress is derived from flow stress, which depends on yield and ultimate tensile strengths. Instrumented indentation technique (IIT) is a nondestructive alternative to the conventional tensile testing. A large amount of studies related to IIT reported that IIT is capable to assess the yield strength and the ultimate tensile strength with 10 % accuracy compared to the tensile testing. The benefit of instrumented indentation technique (IIT) for the analysis of allowable flaw sizes is critically assessed in this study based on experimental data and Code calculations. Intrinsic standard deviations of yield and ultimate tensile strengths for Type 304 stainless steels are discussed in this paper. As a result, IIT method is capable to estimate the flow stress for Type 304 stainless steel within 3.2 % deviation from the result of conventional tensile tests. Then, the allowable circumferential flaw sizes for pipes subjected to tensile loading are obtained based on strength properties assessed by IIT. In addition, the allowable flaw sizes are compared to the allowable flaw sizes derived from the flow stress tabulated in the ASME B&PV Code Section II, Materials. The conclusion is drawn that IIT yields sufficiently accurate estimates of the flow stress on austenitic stainless steel piping. Therefore, IIT is a beneficial method for the Limit Load Criteria analysis LLC.
Ha et al. (Thu,) studied this question.