Date of Award

3-26-2002

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Shankar Mall, PhD

Abstract

Effects of Shot-peening on High Cycle Fretting Fatigue behavior of Ti-6Al-4V were investigated. Experiments were performed with 6.35 mm thick specimens which provided S/N curves. After the tests, it was observed that the specimens failed near the trailing edge of contact. Scanning Electron Microscopy showed that cracks initiated on the contact surface for 6.35 mm, and at the depth of specimen ranging from 200 to 300 microns for 3.81 mm thick specimens. Initial crack orientation was around 37 and 42 degrees respectively for 6.35 and 3.81 mm thicknesses. Finite Element Analysis (FEA) was conducted, and using FEA results, Smith-Watson-Topper, Findley, Shear Stress Range and Modified Shear Stress Range parameters were evaluated. Stress relaxation was observed after the failure of the specimens, and evaluations were repeated for different percentages of stress relaxation. Based on specific assumptions about stress relaxation. Modified Shear Stress range parameter was determined to be the only appropriate fatigue parameter that could meet all the required conditions for shot-peened fretting fatigue specimens. Also thickness effects on shot-peened specimens were investigated and discussed in this study.

AFIT Designator

AFIT-GAE-ENY-02-12

DTIC Accession Number

ADA401223

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