The swage autofrettage barrel is formed depending on the depth of plastic deformation since the diameter of the tool is slightly larger than the barrel inner diameter.The barrel forged in this way can withstand large internal pressures.In order to calculate the degree of autofrettage

the relation between the interference and the plastic radius must be accurately investigated.In loading process

the radial stress of cylindrical section of swage and thick-walled cylinder contact section is equal.By using this boundary condition

an elastic analysis for swage and a plastic analysis for thick-walled cylinder were conducted

and formulas were obtained for calculating excess and plastic radius.Knowing interference

the plastic radius could be calculated directly and the tight tolerance could be pre-estimated by using the plastic radius.To verify the accuracy of the formula

the process of mechanical autofrettage with ten kind different interferences were simulated.Calculated plastic radius agreed well with the results of numerical simulation.