Date of Award

12-15-2011

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Anthony N. Palazotto, PhD.

Abstract

This research has been aimed at developing methods to predict mechanical wear of sliding bodies at high velocities. Specifically, wear of test sled slippers at the Holloman High Speed Test Track at Holloman AFB, NM, is being considered. Developing a numerical model to represent the velocity range achieved at the test track is infeasible, so numerical modeling techniques must be adopted. Previous research has made use of finite element codes to simulate the high velocity sliding event. However, the extreme velocities at the test track can create numerical errors in the finite element codes. To avoid the numerical errors, an Eulerian-Lagrangian hydrocode called CTH has been used to allow for a velocity range of 200 to 1,500 meters per second. The CTH model used in this research performs plane strain analysis of a slipper colliding with a 6 μm radius semi-circular surface asperity. The slipper-asperity collision event creates pressure waves in the slipper which leads to failed cells and worn material. Equations have been derived to represent the onset of plasticity and elastic wave speed through a material under plane strain conditions. These equations were validated using the CTH model. Several failure criteria were evaluated as possible methods to estimate damaged material from the sliding body. The Johnson and Cook constitutive model was selected because of its ability to handle high strains, strain rates, and temperatures. The model developed in this thesis calculates total mechanical wear between 49.31% and 80.87% of the experimental wear from the HHSTT January 2008 test mission.

AFIT Designator

AFIT-GAE-ENY-11-D01

DTIC Accession Number

ADA554187

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