Doctoral Dissertations

Date of Award

8-2006

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Biosystems Engineering

Major Professor

Paul D. Ayers

Committee Members

Alvin R. Womac, Eric C. Drumm, Jeffrey S. Freeman

Abstract

Terrain impact models were developed for both wheeled vehicles and tracked vehicles based on the analysis of vehicle dynamics, soil mechanics, and geometric relationships between vehicle parameters and the disturbed width. The terrain impact models, including both disturbed width models and impact severity models, were developed separately for tracked vehicles and wheeled vehicles.

The disturbed width models of both vehicle types were primarily based on the geometric relationship between vehicle contact width and vehicle dynamic parameters. For both vehicle types, the impact severity was defined as the ratio between soil shear stress and soil shear strength. The impact severity model of wheeled vehicles was based on the balance between the centrifugal force of the vehicle and the soil shearing force that was related to vehicle dynamic parameters. For tracked vehicles, the soil shear stress was primarily de- rived from the lateral displacement of the tracks, not the centrifugal force, thus the impact severity model of tracked vehicles was based on the relationship between soil shear stress and soil lateral displacement caused by the lateral movement of the tracks.

Field tests of both wheeled vehicles and tracked vehicles were conducted at different test sites with different soil types and soil strength. The wheeled vehicles included a High Mobility Multipurpose Wheeled Vehicle (HMMWV), and a Light Armored Vehicle (LAV). The tracked vehicles included an M1A1 tank, an M577 armored personal carrier (APC), and an M548 cargo carrier.

The field test data supported the prediction of terrain impact models. The average per- centage errors of the disturbed width model of the LAV and the HMMWV were 19.5 % and 8.6 %, respectively. The average percentage errors of the impact severity model for the LAV were 48.5 % and 34.2 % for the high-speed (9.6 m/s) test and low-speed (5.4 m/s) test, respectively. The average percentage errors of the disturbed width model for the M1A1, M577, and the M548 were 10.0 %, 27.3 %, and 8.5 %, respectively. The average percent- age errors of the impact severity model of the M1A1 and M577 were 25.0 % and 21.4 %, respectively.

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