Selection of materials to be used for components experiencing extreme conditions is a critical process in the design phase. Nickel-base superalloys have been frequently used for hot gas path components in the turbomachinery industry. These components are required to withstand both fatigue and creep at extreme temperatures during their service time. In general, the extreme temperature materials mostly embody polycrystalline, directionally solidified, and single crystal superalloys. It is essential for design engineers to predict accurate damage behavior and lifespan for these components to prevent catastrophic failures. This dissertation presents a new framework to represent mechanical behavior of Nickel-base superalloys under variety of loading conditions. A set of constitutive and lifing models that can be applied broadly are developed based on observed trends. Despite the development of over 30 variations of single crystal and directionally solidified Nickel-base superalloys, the behavior of these alloys nominally follows similar trends with respect to temperature and orientation. Temperature-, rate-, and orientation- dependence of these materials are studied. The goal is to eliminate extensive time and cost of experiments by creating parameters to be used in strength and life calculations for generic single crystal and directionally solidified Nickel-base alloys. In order to apply generic constants to deformation modeling, a crystal-plasticity model is modified to create stress-strain hysteresis loops. Strain, stress and multi-axial life models are developed to represent the lifing behavior of the candidate alloys under uniaxial and multiaxial environments. Tensile and low-cycle fatigue experiments are conducted to measure the accuracy of these models. Parameters for the models are built on regression fits in comparison with a comprehensive material database. This database includes elastic, plastic, creep, and fatigue properties.
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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)
Irmak, Firat, "Generic Behavior Framework of Sx and Ds Nickel-Base Superalloys with Applications to Constitutive and Life Prediction Modeling" (2022). Electronic Theses and Dissertations, 2020-. 1222.