In this blog post, we investigate the relevant material models in the COMSOL Multiphysics software for analyzing thermomechanical fatigue. Experimental data from thermomechanical fatigue tests are used, along with material parameters from the referenced literature. Subsequently, a pressure vessel assumed to be operating at elevated temperatures is analyzed, and a nonlinear continuous fatigue damage model is used to assess the fatigue life.

One way to assess the fatigue capability at elevated temperatures is to use the stabilized (often midlife) stress-strain curve of a specimen at several temperatures to obtain a stress or strain amplitude and determine the hardening parameters governing the nonlinear stress-strain curve. One could then, in theory, conduct experiments with a particular set of combinations of applied load and temperature and attempt to estimate the fatigue life from experimental results. Thermomechanical fatigue testing, however, takes a relatively long time and is costly. A more convenient way of assessing the fatigue capability at elevated temperature is to use an analytic expression for the relation between stress levels and cycles to failure and correct it for temperature.




S N Curve Software 18