Autofrettage and Shakedown Analysis of Strain-Hardening Cylinders under Thermo-Mechanical Loadings

Autofrettage and shakedown analysis of power law strain-hardening cylinders subjected to thermo-mechanical loads were performed in the present study. The closed form solution of the limit thermal load of autofrettage and the optimum autofrettage pressure under plane strain and open-ended conditions are investigated theoretically and validated by the finite element method (FEM). In addition, the effect of autofrettage on the shakedown behaviour of thick cylinders subjected to a constant internal pressure and cyclic thermal loading is discussed. Results reveal that the limit thermal load depends on the thickness ratio and operating pressure and the optimum autofrettage pressure relies on the thickness ratio, operating pressure, strain-hardening exponent, as well as the thermal load. The proposed solution of the optimum autofrettage pressure agrees very well with the FEM result. The theoretical solution of the optimum autofrettage pressure decreases in plane strain and can be used to estimate the case of open-ended conditions with good accuracy. Furthermore, autofrettage has no effect on the shakedown behaviour due to the rapid relaxation of autofrettaged residual stress of structures after several load cycles.