Strain-Rate Equations for Calculation of Secondary Creep Deformation of Thick-Walled Tubes with Internal or External Pressure.

Tubular structures such as heat exchangers and fuel-pin cladding may be operated at temperatures and stress levels such that creep occurs during normal operation for long lifetimes. Equations are presented relating the strain rate for secondary creep in thick-walled tubes at constant temperature with static internal pressure. Stress equations and strain-rate equations are given for the compressive secondary creep of thick-walled tubes at constant temperature with constant external pressure. The equations given are applicable in designing tubes undergoing secondary creep for long lifetimes with limited deformation.