Inelastic Modelling for Engineering Design for High Temperature Conditions

Abstract

Modern power plants and processing equipment require increasingly higher operating temperatures in the continual effort to achieve higher efficiencies. During operation components undergo thermally induced stress and strain cycles, which, combined with dwell times, can induce significant amounts of inelastic strain. This inelastic strain plays a critical role in limiting component life and therefore must be accurately evaluated for the purposes of life assesment. At low temperatures the stress-strain history in a critical area of a component can be determined experimentally or simulated by straightforward elastic analysis. However at high temperatures and under conditions of steady or slowly varying loads, these methods become impractical. Instead the stress-strain history can be determined analytically using non-linear constitutive laws, based on temperature measurements and the theoretically predicted temperature distribution [1]. For such a technique to be successful more accurate material constitutive laws combined with modern methods of numerical structural analysis need to be used.