ORCID

0009-0009-5931-8746

Keywords

Fracture toughness; Ductile fracture locus; Crack tip analysis; Finite element analysis

Subject Categories

Materials Science and Engineering | Mechanical Engineering

Abstract

Traditional elastic-plastic fracture mechanics (EPFM) relies on crack-tip analysis, whereas continuum damage mechanics (CDM) is typically calibrated from uncracked bodies. This dissertation aims to bridge the gap between these two fundamental branches by explicitly linking fracture toughness with ductile damage models. Based on the assumptions regarding Mode I crack deformation, analytical solutions are derived to establish a novel relationship among Mode I fracture toughness, CDM-based ductile fracture strain, and material strain hardening capability. This theoretical framework is subsequently extended to encompass Mode II and Mode III loading conditions. To validate the proposed relationships, finite element (FE) models are developed in Abaqus, using compact tension (ASTM E399/E1820), compact tension shear, and circumferentially cracked cylindrical specimens. Before simulating the damage-driven crack propagation, a new mesh size dependence study is introduced. By integrating the equivalent plastic strain along the maximum strain gradient path ahead of the crack tip, this approach enables the accurate scaling of macroscopic damage models for micro-mesh domains. Using elastic-plastic properties and mesh-size-scaled Modified Mohr-Coulomb (MMC) fracture models, the Mode I, II, and III fracture toughness, evaluated by contour J-integral, is simulated for a wide range of metallic alloys. These numerical results show strong agreement with experimental data reported in the literature. Furthermore, the proposed relationships are rigorously corroborated through surface fitting, demonstrating high correlation coefficients, for example, R^2=0.965 for Mode I. This research provides a highly efficient and robust methodology for estimating fracture toughness directly from material properties and ductile fracture strain, offering significant potential for advancing the non-destructive evaluation (NDE) of structural integrity.

Completion Date

2026

Semester

Summer

Committee Chair

Bai, Yuanli

Degree

Doctor of Philosophy (Ph.D.)

College

College of Engineering and Computer Science

Department

Department of Mechanical and Aerospace Engineering

Format

PDF

Document Type

Dissertation

Language

English

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