Abstract: In order to compute the strength and fatigue life of autofretted barrel exactly, a constitutive model which can reflect the material characteristics of gun steel, including Bauschinger effect and the nonlinear relationship between stress and strain, is constructed for improving the calculating accuracy of residual stress. On the basis of a nonlinear kinematic hardening model, a nonlinear combined hardening model which is used to describe the mechanical properties of autofretted barrel and calculate the residual stress distribution is proposed. According to the proposed constitutive model and the elastic-plastic relationship among parameters, a tensor-form consistent tangent modulus related to the constitutive model is derived for increasing the convergence speed of numerical calculation. To verify the constitutive model, the material parameters are determined by combining the tension compression tests and optimization algorithm. The residual stress of autofretted barrel is calculated by utilizing these parameters and FEA method. The difference between the calculated and experimental results is small. The results show that the proposed constitutive model can reflect the residual stress distribution of autofretted thick-walled cylinder effectively. Key

Key words: barrel, autofrettedthick-walledcylinder, residualstress, constitutivemodel, consistenttangentstiffnessmatrix, parameteroptimization