Measurement and prediction of residual stresses in autofrettaged high pressure tubing incorporating temperature and bauschinger effect

High pressure tubing for polyethylene production is autofrettaged to improve its resistance to fatigue and stress corrosion cracking. For an accurate assessment of the integrity of the tubing it is essential to have an accurate knowledge of the residual stresses. In this paper the results of a combined experimental and numerical (finite element) investigation are presented. Results were obtained from the tube immediately after autofrettage and after exposure to temperature typical for polyethylene production. The conventional Sachs boring method was employed to measure residual stress distributions. Finite element results are shown to be in good agreement with the experimental results and demonstrated the influence of reverse yielding on the residual stresses close to the bore was important. Measurements following exposure to high temperature revealed that there was local relaxation of the residual stresses near to the inner wall of the tube. At other points through the wall thickness only small changes were found.