ORCID

0009-0009-8746-2761

Keywords

fracture toughness, micro-cutting, finite element method, Johnson-Cook damage model, Atkins model, orthogonal cutting

Abstract

Accurate determination of plane-strain fracture toughness is essential for structural integrity assessments of engineering components, yet conventional ASTM standardized testing methods require large, notched specimens that are impractical in many industrial and research contexts. This thesis presents a finite element method-based approach for estimating the mode I plane-strain fracture toughness of engineering materials from orthogonal micro-cutting simulations if the continuum damage mechanics-based fracture locus is calibrated. This method will eliminate the need for pre-cracked specimens while maintaining physically grounded fracture mechanics principles. The methodology applies to the Atkins energy-based cutting force model, in which the depth-independent intercept of the specific cutting force versus uncut chip thickness regression encodes the fracture energy per unit area of newly created surface. Simulations were performed in Abaqus/Explicit using a two-dimensional plane-strain thermomechanical framework with the Johnson-Cook constitutive and damage models for seven engineering materials: Al2024-T351, AISI 1045, Ti-6Al-4V, Al7075-T651, Al6061-T6, 316L stainless steel, and Inconel 718. A novel energy correction factor derived from global Abaqus output variables was introduced to isolate the fracture energy contribution from total external work, accounting for plastic dissipation and frictional work that do not contribute to new surface formation. The corrected fracture toughness values were computed using the Irwin plane-strain relation and compared against published reference values from peer-reviewed literature and standardized materials databases. Results show that six of seven materials produced fracture toughness estimates within the published ranges reported in the literature, with Al6061-T6 and Al2024-T351 achieving errors below seven percent relative to standard reference values. Discrepancies observed in Ti-6Al-4V and 316L stainless steel were attributed to Johnson-Cook damage parameter quality and reference value selection, respectively, rather than to fundamental limitations of the proposed methodology. These findings support the viability of micro-cutting finite element simulations as a small-scale, specimen-efficient alternative for fracture toughness characterization of metallic materials.

Completion Date

2026

Semester

Spring

Committee Chair

Bai, Yuanli

Degree

Master of Science in Mechanical Engineering (M.S.M.E.)

College

College of Engineering and Computer Science

Department

Department of Mechanical and Aerospace Engineering

Document Type

Dissertation/Thesis

Identifier

DP0053255

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