Microstructure-sensitive creep-fatigue interaction crystal-viscoplasticity model for single-crystal nickel-base superalloys
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Estrada Rodas, Ernesto Alejandro
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Abstract
An enhanced generation temperature-dependent crystal viscoplasticity (CVP) model targeting the creep-fatigue interactions in Ni-base superalloys single-crystals is developed. The model is fitted to experimental data obtained on superalloy CMSX-8. At the microstructure level of interest, superalloys are comprised of an ordered and a disordered face-centered cubic phase. However, few models explicitly account for the deformation mechanisms active on each phase. In this work, a novel approach is used to model both material phases and to bridge several length scales. To this end, a physically-based approach is utilized to model the microstructure morphology, the distinct deformation mechanisms that become active on each material phase, and the evolution of dislocation densities. This increased fidelity leads to challenges in implementation which are addressed by developing a new quasi Newton-Raphson algorithm. The algorithm enables application in commercially-available displacement-based Finite Element codes. The CVP model can help designers predict component response using realistic geometries and boundary conditions. This model is also a first step toward an Integrated Computational Materials Engineering (ICME) tool that could be used to enhance current understanding of superalloys and alloy design.
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2017-04-06
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Dissertation