Date

5-20-2026

Department

School of Engineering

Degree

Doctor of Philosophy in Engineering (PhD)

Chair

Mark Atwater

Keywords

Surface Mechanical Attrition Treatment, Position and Energy Controlled Surface Mechanical Attrition Treatment, Shot Peening, Single-Site Impacts, Chemistry-Process-Structure-Property-Performance Relationship, Inelastic Deformation, Coupled Discrete-Finite Element Modeling, Compressive Residual Stresses, Internal State Variables, Bammann Plasticity, Horstemeyer Damage, Cho Grain Growth and Recrystallization, Isotropic Hardening, Kinematic Hardening, Grain Growth, Recrystallization, Microstructural Strengthening, Stress Strengthening, Analytical Modeling, High-Speed Footage, Crank-Slider Mechanisms, Numerical Methods, Julia, Parallel Processing, Abaqus, High-Performance Computing

Disciplines

Mechanical Engineering | Philosophy

Abstract

This work adds insight to the physical phenomena of microstructural and stress strengthening of metal components by the inelastic deformation from Surface Mechanical Attrition Treatment (SMAT). Impact behaviors observed by high-speed footage of a Crank-Slider Mechanism (CSM) are examined in the context of analytically moving rigid bodies in spacetime and resolving kinematics upon impact until restitution via Finite Element Analysis (FEA). A Coupled Discrete-Finite Element Model (CDFEM) leverages Bammann plasticity, Horstemeyer damage and void nucleation, growth, and coalescence and Cho recrystallization Internal State Variable (ISV) models to show the localization of plastic strain and onset of recrystallization under any single impact. This emphasizes using the current state of ISVs and their constitutive rate equations to represent the deformation history. This CDFEM model is also used to study the entire treatment history and effects on material properties from Position and Energy Controlled SMAT (PECSMAT) indenting. A material point simulator using the same constitutive material models as the CDFEM is employed to calibrate material model constants for the given range of expected strain rates under any single-site impact and whether the same constants hold accurate to the post-processed properties of Oxygen Free, High-Conductivity copper (OFHC) subjected to some pattern and intensity of PECSMAT indentation and a tensile test. This work shows that there exists some threshold of strain rate such that the onset of recrystallization does not immediately cause significant grain refinement. At moderate strain rates, SMAT treatments relying on shot impingement enhance material properties by creating localized, severe plastic deformation zones to activate stress strengthening and imbue a spatial distribution of sub-surface residual stresses as well as isotropic and kinematic hardening independent of recrystallization.

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