Comparison between hot surface stress and effective stress acting at notch-like defect tip in a pressure vessel

Abstract

In this study, we have compared effective stress obtained by the Volumetric Method (VM) and hot surface stress (HS) obtained by linear or quadratic extrapolations for a longitudinal or transversal surface defect stress distribution in a pressure vessel. It appears clearly that the definition of hot surface stress through linear extrapolation characterises the gross stress distribution affected by stress concentration. It has been found that effective stress and hot surface stress are close. This is due to the fact that the tested pressure vessel is made with a thin pipe of ductile material where plastic relaxation induced a smooth peak stress distribution. Prediction of stress distribution at the deepest point of a surface defect from stress distribution at surface tip of the defect exhibits some difficulties due to modification of stress intensity and stress gradient.