Elastic-plastic fracture mechanics based prediction of crack initiation load in through-wall cracked pipes

In order to evaluate the structural integrity of power plants, it is required to know the load carrying capacity of a piping system. J-integral based elastic-plastic fracture mechanics (EPFM) has become a useful analytical technique for dealing with ductile materials. It is important to see how accurately we can predict the stages of leak-before-break demonstration using EPFM. Current efforts are focussed on verifying previously developed J-estimation schemes for through-wall cracked (TWC) straight pipes with the calculated elastic-plastic J-integral values that are obtained by conducting a rigorous 3D non-linear finite element analysis using advanced fracture analysis code WARP3D. This includes the validation and benchmarking of J-estimation schemes with the present 3D non-linear finite element analysis results and with the experimental results at crack initiation stage. The results corresponding to crack initiation results calculated by estimation schemes are too conservative. Thus, in order to perform J-integral based EPFM analysis more accurately and conveniently, there is a need to develop an efficient estimation scheme that can represent material behaviour closely. The crack initiation load calculated by the present finite element analysis results is shown to provide a more reasonable prediction.