Nickel-base superalloys (NBSAs) are widely used in engineering applications for many turbomachinery component designs. Superior material properties at high temperatures such as high tensile strength, superior fatigue strength, excellent resistance to thermal shocks, and strong corrosion resistance are primarily responsible for their extensive application. This proposal focuses on modeling generic single crystal (SX) and directionally solidified (DS) Ni-base superalloy. Compared to polycrystal superalloys, SX superalloys exhibit superior thermal fatigue and creep resistance which is attributed to the absence of grain boundaries in the SX crystalline structure. Directional solidification procedures enable the solidification structure of the materials to be comprised of columnar grains in aligned with the  direction. Grain boundaries are locations where failure is initiated hence the reduction of grain boundaries in comparison to polycrystals and the alignment of grain boundaries in the normal to stress axis increases the strength of the material at high temperatures. A physically based material model that can accurately simulate the cyclic deformation behavior is essential to facilitate component life predictions. A framework that combines theoretical mechanics, experimental mechanics, and numerical simulations are required to support the mechanical design process. For a method to be viable, it must capture material response for monotonic, low cycle fatigue (LCF), thermomechanical fatigue (TMF), and creep under a variety of conditions. At high temperatures, material deformation is mostly attributed to the evolution of the microstructure due to crystallographic slip along the crystallographic slip planes. A crystal viscoplastic (CVP) modeling framework is developed to simulate the physical characteristics to accurately model the material behavior. In doing so the approach presented in this dissertation establishes a framework to readily model any SX and DS material.
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Doctor of Philosophy (Ph.D.)
College of Engineering and Computer Science
Mechanical and Aerospace Engineering
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Wijeyeratne, Navindra, "Crystal Viscoplastic Modeling of Single crystal and Directionally solidified Nickel-base Superalloys" (2022). Electronic Theses and Dissertations, 2020-. 1306.