Investigation of the creep of fuel-element cans under internal pressure using a damage-function creep theory

Abstract

The creep deformation of an internally pressurized fuel-element can in the presence of superposed cyclic thermoelastic stresses is investigated. The period of significant primary creep is comparable with that of the cycle. Hence it is necessary to develop a more complex theory than that of time or strain hardening. The simplest of such theories based on dislocation behaviour but in which the material parameters occurring may be determined from simple experiments was chosen. For an austenitic steel this theory gave good agreement with both creep and relaxation tests. It was applied therefore to the problem of the fuel-element can. It was found that in practice the increased damage caused by the cycling over-compensated for the effect of the increased stress so that the material did not deform as much as when there was no cycling.