Computational Viscoplasticity-Based Modeling of Stress/Strain Response in Thermomechanical Fatigue Loads

Contemporary computing packages handle a wide variety of stress analysis types, but are yet to provide an optimal way to handle certain load cases and geometries. Blades in gas turbine propulsion systems, for instance, undergo repetitive thermal and mechanical load cycles of varied shape and phasing. Complexly-shaped airfoils create non-uniform stress paths that exacerbate the problem of FEA software attempting to determine the correct states of stress and strain at any point during the loading. This research chronicles the modernization and integration of Miller’s 1976 viscoplasticity model with ANSYS finite element analysis software. Non-isothermal fatigue loadings of various types were applied to smooth specimen geometries and the results were compared to data from duplicate mechanical testing experiments. Findings indicate that this and other certain constitutive models can be integrated with software like ANSYS to handle load types that previously could not be accurately evaluated. Accurate stress-strain response via computational methods is a first step toward reliable fully-automated life prediction of parts. Such methods are powerful tools capable of helping providing safe and efficient turbine operation without the need for conservative service intervals.