Reduced-Order Constitutive Modeling of Directionally Solidified Ni-Base Superalloys

Abstract

Temperature-dependent crystal viscoplasticity models are ideal for modeling largegrained, directionaiiy solidified Ni-base superalloys but are computationally expensive. This work explores the use of reduced-order models that are potentially more efficient with similar predictive capability of capturing temperature and orientation dependence. First, a transversely isotropic viscoplasticity model is calibrated to a directionaiiy solidifled Ni-base superalloy using the response predicted by a crystal viscoplasticity model. The unifled macroscale model is capable of capturing isothermal and thermomechanical responses in addition to secondary creep behavior over the temperature range of 20-1050°C. A second approach is an extreme reduced-order microstructure-sensitive constitutive model that uses an artificial neural network to provide a set of parameters that depend on orientation, temperature, and strain rate to give a flrst-order approximation of the material response using a simple constitutive model. This simple relationship is then used in a Neuber-type fatigue notch analysis to predict the local response.

Thermomechanical Fatigue of Mar-M247: Extension of a Unified Constitutive and Life Model to Higher Temperatures

“…Because of this, it is necessary to perform separate TMF tests in order to accurately predict life under TMF loading conditions. There are many possible temperature and load combinations possible for TMF tests; however, there are two that are the most common: in-phase and out-of-phase loading [22]. An example of these load histories is shown in Figure 2.1.…”