The Effect of Infrequent Thermal Overloads on the Behavior of Plates Subjected to Cyclic Thermal Loading

Abstract

Many components in high-temperature plant experience steady mechanical loads combined with cyclic thermal loads due to routine shutdowns. Less frequent but more severe thermal loads due to unplanned shutdowns may interrupt this routine loading pattern. This paper presents the results of computer calculations on the effect of such thermal overloads on the behavior of a “Bree plate.” Particular attention is given to the creep and plastic ratchetting deformation properties of the system. It is shown that the plate material properties are an important factor in the problem. With an elastic-perfectly plastic plate material, behavior can be predicted from an appropriate linear combination of the results for each type of thermal cycle, multiplied by an enhancement factor in certain cases. With a bilinear kinematic hardening, material behavior is generally determined by the properties of the overload thermal cycle. These results are relevant to many high-temperature design problems.