A J-integral estimation procedure for Swift-type stress–strain curves

A new J-integral estimation procedure, referred to as the reference plastic slope method, was developed in order to provide J-integral solutions for cold worked and non-cold worked stainless steels. In the reference plastic slope method, J-integrals for bi-linear stress–strain curves were used to derive J-integrals for a material having stress–strain curves fitted well by the Swift-type constitutive equation. The validity of the reference plastic slope method was shown for a two-dimensional through-wall crack and three-dimensional surface cracks. Then, J-integral solutions were tabulated for a circumferential surface crack on a straight pipe under a bending moment for various geometrical and material conditions. It was shown that the error in the allowable load assessments using the obtained solutions was less than 5% at the worst case.