Efficient Methodologies for Determining Temperature Dependent Parameters of a Ni Base Superalloy Crystal Viscoplasticity Model for Cyclic Loadings

Abstract

The prediction of temperaturedependent fatigue deformation and damage in directionally solidified and singlecrystal nickelbase superalloy components used in the hot section of gas turbine engines requires a constitutive model that accounts for the crystal orientation in addition to the changing deformation mechanisms and rate dependencies from room temperature to extremes of the use temperature (e.g., 1050 آ°C). Crystal viscoplasticity (CVP) models are ideal for accounting for all of these dependencies. However, as the models become more physically realistic in capturing the true cyclic deformation mechanisms, increases the requirements to achieve an accurate model calibration. As a result, CVP models have yet to become viable for life analysis in industry. To make CVP models an industry relevant tool, the calibration times must be reduced. This paper explores methods to reduce the calibration time. First, a series of special calibration experiments are conceived and conducted on each relevant orientation and microstructure. Second, a set of parameterization protocols are used to minimize parameter interdependencies that reduce the amount of iteration required during the calibration. These experimental and calibration protocols are exercised using the CVP model of Shenoy et al. (2005, “Thermomechanical Fatigue Behavior of a Directionally Solidified NiBase Superalloy,â€‌ ASME J. Eng. Mater. Technol., 127(3), pp. 325–336) by calibrating a directionally solidified Nibase superalloy across an industry relevant temperature range of 20 آ°C to 1050 آ°C.