Residual Stress Calculation of Hydraulic Autofrettage Thick-Walled Tube Based on a Revised Kinematic Hardening Model

Abstract

The current theoretical calculation methods for autofrettage of thick-walled tube do not adequately consider the change in the stress-strain relationship of the material with the maximum loading strain. This deficiency has an adverse impact on the accuracy of the residual stress calculation after autofrettage. In this paper, the revised kinematic hardening model is adopted to take change of the stress-strain relationship of the material in the compression section after different maximum tensile strains into consideration. Furthermore, power function is used to express the stress-strain relationship in the plastic section in both the tensile and compressive plastic parts. A new calculation method for the autofrettage residual stress of the hydraulic thick-walled straight tube is came up with through this method. This method enhances the precision of autofrettage residual stress calculations without undue increase of the computational burden. In comparison to the finite element method results utilising identical material data, the proposed model exhibits enhanced calculation precision, particularly with regard to the stress distribution on the inner surface, surpassing by at least 5% in terms of calculation accuracy than existing calculation methods. Furthermore, the accurate autofrettage residual stress on the inner surface of thick-walled straight tubes obtained through theoretical calculations is of paramount importance for fatigue design of autofrettage thick-walled vessels.