Electronic Theses and Dissertations

Samira Ghadar

Date

2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

Committee Chair

Ali Fatemi

Committee Member

Ali Fatemi

Committee Member

Gladius Lewis

Committee Member

John Williams

Committee Member

José Alexander Araújo

Committee Member

Yue Guan

Abstract

Fretting fatigue, a critical failure mechanism in structural assemblies, occurs due to small-amplitude relative motion between contacting surfaces under cyclic loading, significantly compromising fatigue life. Despite extensive studies, the understanding of coupled influences of mechanical, material, and environmental factors remains incomplete, motivating the need for integrated experimental and predictive modeling approaches. This dissertation first provides a comprehensive literature review and synthesis of experimental studies of key fretting fatigue parameters including contact pressure, slip amplitude, frequency, surface roughness, contact geometry, and environment. Then the fretting fatigue life modeling approaches used in the literature are reviewed and their strengths and limitations are discussed. A critical plane approach combining the Fatemi–Socie (FS) parameter with the Theory of Critical Distances (TCD) was selected and validated against extensive fretting fatigue literature data on aluminum and titanium alloys. The FS parameter accounts for the complex non-proportional multiaxial stresses, the interaction between tangential-to-normal stress, and the mean stress effects. TCD accounts for the steep gradients at contact interfaces. The life prediction framework utilized accurately predicted crack initiation at the trailing edge, crack orientations within the observed ranges, and fatigue lives within relatively narrow scatter bands. The study also presents a comprehensive analytical investigation into the fretting fatigue behavior of cold-sprayed ZE41A-T5 cast magnesium alloy, with particular emphasis on the influence of contact pressure, slip amplitude, and loading frequency. The data were generated with a custom-designed fretting fatigue test rig at the Army Research Laboratory enabling decoupled application of slip amplitude and axial loading to replicate service-relevant multiaxial stress states. A computationally efficient life prediction methodology was developed by integrating the stress concentration concept for local stresses used in the FS parameter. The modeling framework offers a practical and efficient tool for life prediction, reducing reliance on computationally intensive nonlinear analyses for each test scenario. The methodology used demonstrates strong correlation of the experimental data with observed fatigue life under diverse experimental fretting fatigue conditions, with all test data falling within ±1.5x scatter bands on life.

Comments

Data is provided by the student.”

Library Comment

Dissertation or thesis originally submitted to ProQuest.

Notes

Open Access

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