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Title:The topological derivative and its applications to fracture-based analysis and design
Author(s):Alidoost, Kazem
Director of Research:Tortorelli, Daniel A; Geubelle, Philippe H
Doctoral Committee Chair(s):Tortorelli, Daniel A; Geubelle, Philippe H
Doctoral Committee Member(s):James, Kai; Masud, Arif
Department / Program:Mechanical Sci & Engineering
Discipline:Theoretical & Applied Mechans
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Asymptotic Analysis
Computational Mechanics
Edge Cracks
Energy Release Rate
Surface Cracks
Shape Optimization
Topological Derivative
Abstract:This thesis discusses the topological derivative and its application to fracture-based analysis and design. The topological derivative describes the variation of a response functional with respect to infinitesimal changes in topology, such as the introduction of an infinitesimal crack or hole. In a previous work, Silva et al. [1] developed a first-order approximation of the energy release rate field in a two-dimensional domain associated with a small edge crack at any boundary location and any orientation. In this thesis, we extend this work. We first develop higher-precision approximations of the energy release rate field using higher-order topological derivatives, which allow the analyst to accurately treat longer cracks and determine the crack lengths for which the first-order approximation is accurate. These higher-order topological derivatives are calculated using the so-called topological-shape sensitivity method [2]. We next propose an approximation of the energy release rate field in a three-dimensional domain associated with a small surface crack of any boundary location, direction, and orientation combination using the topological derivative. This approximation is computationally attractive because it only requires a single analysis. By contrast, current boundary element and finite element based methods require an analysis for each crack length-location-direction combination. Furthermore, this approximation is evaluated on the non-cracked domain, obviating the need for refined meshes in the crack tip region. We conclude by leveraging the efficiency and simplicity of the proposed approximation to develop a fracture- and gradient-based shape optimization scheme for the design of fracture-resistant linearly elastic structures. A key characteristic of the shape optimization scheme presented in this thesis is that the domain and its boundary are defined implicitly using level-set functions constructed with the aid of R-functions, which allow for the use of differentiable Boolean operations to combine the level-set functions of predefined simple geometries. This adoption of R-functions has the dual impact of (i) allowing shapes to merge and/or separate and (ii) simplifying the computation of the shape velocity fields.
Issue Date:2020-09-15
Rights Information:Copyright 2020 Kazem Alidoost
Date Available in IDEALS:2021-03-05
Date Deposited:2020-12

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