The assessment of defects in structures of strain hardening material

J-estimation procedures based on finite-element solutions are expressed in terms of the material stress-strain curve by using reference stress techniques common in creep analysis. The result is an exact representation of the estimation procedures for materials which strain harden according to the simple power law used in the finite-element calculations. For other materials, it is shown that an appropriate definition of the reference stress reduces the dependence of the results on the accuracy to which the strain hardening can be described by a simple power law. The resulting reference stress based estimation procedure is used to derive a failure assessment curve for use with the CEGB failure assessment route. Comparison is made with the modified failure assessment curve recently suggested by Milne and the implications of the results for defect assessments are discussed. (author)