Effect of prior deformation on creep behaviour of AISI 316H austenitic stainless steels

Analytical, numerical and experimental investigations on the influence of prior deformation on creep relaxation and creep crack growth behaviour of cracked austenitic steel specimens have been carried out in this work. The evolution of the creep characterising parameters in the presence of residual stress has been examined, initially for single edge notched bend, SEN(B), and tension, SEN(T), specimens and then for compact tension, C(T), specimens. The level of conservatism of available analytical expressions has also been examined in each case. Creep experiments on 316H pre-compressed (pre-stressed) and pre-strained C(T) specimens have been carried out under constant creep loads, and the creep data have been compared with the results from finite element (FE) analysis. Subsequent neutron diffraction measurements have been carried out to quantify the residual stress field within the specimens and useful discussions and comparison with the FE results have been provided. Creep crack growth simulations have also been carried out using the FE method and, after examining the effect of material and geometrical parameters, recommendations have been summarised to provide reasonable agreement with the experiments.