Applications of Isochronous Data in Creep Analysis

This paper evaluates the use of isochronous stress-strain material data for the creep analysis of metals in high temperature applications. Performing an inelastic analysis using isochronous stress-strain data is a simplified approach for computing time dependent behavior using an implicit time embedded method. This method has been widely used as an effective means to evaluate the creep behavior of complex components without performing a detailed time dependent creep analysis. In order to examine the effectiveness and limitations of this method, isochronous stress-strain material data was numerically constructed from a time dependent creep law at various temperatures, sustained stress levels, and time durations. Component stresses and strains are compared from results obtained by running both the isochronous time embedded inelastic and time dependent creep analyses for some example problems. The effectiveness and limitations of this method under different loading conditions, such as primary and secondary stresses, are demonstrated and explained. It is recognized that this method was not intended to apply to thermal stress problem, and the thermal problem was studied to understand constraint effects.