Date of Award

9-2006

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Shankar Mall, PhD

Abstract

Fretting fatigue is the surface damage that occurs at the interface between two components that are undergoing a small amplitude oscillatory movements. It results in a reduction of the material life as compared to the plain fatigue. Most of the previous works were accomplished under a constant applied normal load and a little effort was done under a variable contact load, while none of these studies has considered the phase difference between the axial load and the contact load. The primary goal of this study is to investigate the effect of phase difference between axial and contact loads on fretting fatigue behavior of Ti-6Al-4V alloy. The frequency of both axial and contact loads was the same. i.e. 10 Hz. Under variable contact load condition; only the axial stress range and the phase angle were varied. Cracks were always found to initiate at the contact surface and near the trailing edge in all tests. The software program, ABAQUAS, was used in Finite Element Analysis FEA to determine the contact region state variables such as stress, strain, and displacement. The fatigue parameters; such as the stress range, effective stress, and modified shear stress range (MSSR) were analyzed to predict the fatigue life. The fatigue life with in-phase variable contact load was almost same as that of constant contact load. The out of phase condition increased the fatigue life from 20% to 30% in the low cycle regime and up to 150% in the high cycle regime relative to its counterpart from in-phase loading. The MSSR parameter, a critical plane based fretting fatigue parameter, was very effective in predicting the fatigue life, crack initiation location, and the crack initiation orientation.

AFIT Designator

AFIT-GAE-ENY-06-S02

DTIC Accession Number

ADA456830

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