Fatigue crack propagation analysis of surface cracks in pipe elbows

Piping elbows are one of the critical components of the cooling piping systems in power plants. This paper presents the details of fatigue crack propagation analysis based on code procedure and FEM and compares the results with experimental observations. The fatigue crack propagation was evaluated based on the inelastic range J integral, Js, which was obtained by applying the plastic correction factor (from RCC-MR code) to the elastic J-integral values obtained from the code as well as from the elastic finite element analysis. The fatigue crack propagation was also studied directly using the elastic–plastic J-integral value obtained from the finite element analysis. It was observed that the fatigue life calculated based on the modified Js-integral values was closer on the conservative side to the experimental results, than that from J-integral obtained directly from elastic–plastic finite element analysis.