Life Prediction Feasibility in TMF via Stress/Strain Data From a Viscoplasticity-Based Numerical Model

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 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 load history. This research chronicles the update and integration of Miller’s original viscoplasticity model with ANSYS finite element analysis software. Elevated temperature strain-controlled LCF and strain-controlled TMF loadings were applied to single-element, uniaxial simulation runs and the results were then compared to data from duplicate experimental testing. Initial findings indicate that the model maintains significant accuracy through several cycles, but longer tests produce varying error in hysteretic response. A review of the modernized implementation of Miller’s viscoplasticity model is presented with a focus on modifications that may be used to improve future results.