Optimization of multilayer thick-walled cylinders with simultaneous internal pressure and radial temperature gradient

Abstract

A method has been developed for optimizing the radius and interference design parameters of a multilayer, thick-walled cylinder with independently applied or combined internal pressure and steady-state, radial, thermal gradient loadings. The capabilities are included to permit a set of fixed tangential stresses in each layer to simulate autofrettage, or other residual stresses as well as to allow a fixed, arbitrary, uniformly applied load on the ends of the inner cylinder. The method developed also permits constraining the tangential stress in the inner cylinder to be less than any chosen value. Shrink interferences may be treated as variables or may be fixed at any arbitrary percent of their respective interface radii. Pressure and thermal stresses used in the analysis are from classical elasticity solutions; elastic breakdown is defined by the distortion energy (Mises) yield criterion. Independent material properties ore permitted for all layers. Optimization is carried out using a constrained, nonlinear, gradient projection technique whereby design parameters are systematically varied moving from a starting point to the optimum solution in discrete steps along the steepest gradient which does not result in constraint violations.