Method and Mechanism of Beneficial Residual Stresses in Tubes

It is shown in this paper that residual stresses in a tube could be created in such a way that they are in tension in the middle region of the wall and in compression throughout the entire inside and outside surfaces of the tube. The method of treatment consists of applying an internal pressure and some appropriate alternating hot and cold thermal shocks to the tube. The mechanism of stress evolution in tube wall is demonstrated using elastic-perfectly plastic analysis of a generalized plane strain ID model subjected to a primary tension load σ_m, and an alternating linear temperature difference ΔT across the thickness. Theoretical combinations of loads (σ_m, ΔT) which give such residual stress configurations and formulas for predicted residual stresses are developed. A possible application of this treatment is for prolonging the life of U-bend region of heat exchanger tubes against stress corrosion cracking.