Simulation of thermal fatigue damage in a 316L model pipe component

To contribute to the development of improved methods for assessing possible thermal fatigue damage in nuclear plant piping systems, a unique set of crack growth data has been generated for tubular test pieces in 316L(N) stainless steel subjected to cyclic thermal loads in a specially designed rig. By accurate modelling of the thermal loads and non-linear material behaviour using the finite element method, it was possible to reliably estimate the number of cycles to initiation, using standard isothermal fatigue life curves. To simulate crack growth, an engineering method was applied using published K solutions for semi-elliptical surface cracks and via 3-D elastic–plastic cracked-body analysis of selected scenarios. It was established that conservative estimates of the thermal fatigue crack growth can be obtained using the engineering model in conjunction with an upper bound fatigue crack growth law.