An FEA Investigation Into Ratchetting Induced Purely by Cyclic Thermal Loading

Abstract

A detailed finite element investigation of the cyclic elastic-plastic response of three model structures subject to thermal and mechanical loading is presented within the context of ASME B&PV Code Section VIII Division 2 design requirements. The model structures are a thin tube subject to constant internal pressure and a cyclic throughthickness linear temperature gradient (the Bree problem), a three bar system subject to cyclic thermal loading only and an intermediate thickness tube subject to internal pressure and an axially moving cyclic temperature wave. Incremental elastic-plastic finite element analysis assuming an elasticperfectly-plastic material model and small deformation theory is performed for each model structure and ratchet and shakedown boundaries determined by application of a bisection method. Results are compared with ASME VIII ratcheting assessment procedures. The results show that in the Bree problem ratcheting does not occur under thermal loading alone, as expected, however for the two other sample structures it is shown that ratchetting can occur under thermal loading for structures subject to specific deformation constraints. The lead author is an MS level student at the University of Strathclyde.