Date of Completion

10-29-2018

Embargo Period

4-27-2019

Keywords

high cycle fatigue, corrosion fatigue, short fatigue crack, probabilistic, polycrystalline microstructure, transgranular, intergranular, variable amplitude load, time-deteriorate component

Major Advisor

Wei Zhang

Associate Advisor

Michael L. Accorsi

Associate Advisor

Jeongho Kim

Associate Advisor

Ramesh B. Malla

Field of Study

Civil Engineering

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Many catastrophic failures of metallic structures were found to originate from fatigue damages in local details. Meanwhile, the associated environmental effects such as corrosion and high uncertainties from many aspects including material microstructure also make it difficult to quantify the fatigue life of the components or structures. Partially overcoming the limitation of current experimental means and custom fatigue assessment methods, this dissertation develops a probabilistic multi-scale fatigue damage modeling framework to comprehensively analyze the short fatigue crack behavior in mesoscale microstructure and propagate the damage to component level and structural level analysis.

For statistical volume element (SVE) in mesoscale, a 2D short crack growth framework is proposed based on the microstructure-sensitive model and crystal plasticity based fatigue indicator parameters. A transgranular crack growth method under constant amplitude load is developed and applied to weld microstructure. To incorporate the variable amplitude load, a nonlinear grain-based fatigue damage model is superposed. Then, the simulation algorithm evolves to Integrated Transgranular and Intergranular Crack Growth Method (ITICGM) and further to Corrosion-informed ITICGM. As the natural linkage between short crack growth variability and long crack growth analysis of structural components, the time distribution to initial long crack is quantified by Deterministic Monte Carlo Simulations with order reduction techniques on mesoscale SVEs. The framework has been demonstrated by applying for failure assessment of pressure vessel (single-site damage approach) and T-joint (multi-site damage approach), the latter together with the surrogation of the time-deteriorated component with specific and damage-equivalent member for subsequent structural analysis.

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