A Comparative Study of Crystal Viscoplastic Modeling of Directionally Solidified Nickel-Base Superalloys

Abstract

Nickel-base superalloys (NBSAs) are a group of materials that are used in high-temperature applications. This work primarily focuses on directionally solidified (DS) NBSAs. Directionally solidified materials are comprised of columnar grains which are parallel to the 〈001〉 direction. Crystal viscoplastic (CVP) models can simulate the effects of temperature and orientation dependence under a variety of loading conditions such as tensile, low cycle fatigue (LCF), and thermomechanical fatigue (TMF). The CVP model is initially developed for a single crystal (SX) material and then adapted to DS material to represent the columnar grain structure. In past studies, the development of CVP models for DS materials was mainly accomplished by applying the SX CVP model to the DS materials implicitly or explicitly. Both of these modeling approaches require the application of the SX CVP model to multiple grains resulting in them being highly computationally expensive. A crystal viscoplastic model for DS materials that circumvents the modeling of individual grains was presented by the authors at turbo-expo 2021. The primary objective of this work is to utilize the three types of DS-CVP models for the same materials to investigate their performance. Comparisons will be performed at various temperatures and orientations. The models are compared to analyze their pros and cons and applicability, etc. Comparisons of these three types of modeling approaches applied to the same material have not been presented before in the literature and will provide an excellent insight into the usability of these constitutive models.