Degree Type

Dissertation

Date of Award

1995

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

First Advisor

James E. Bernard

Abstract

Rollover of cars and light trucks in single vehicle accidents is of great interest to designers in the automotive industry and to regulators in government agencies. This thesis addresses metrics--the static stability factor, the tilt table ratio, the side pull test, and the critical sliding velocity--which are proposed measures of vehicle resistance to rollover;A notable finding is that the critical sliding velocity, CSV, is independent of the vehicle mass and roll moment of inertia and depends only on the track width and center of gravity height. Furthermore, while side pull testing and tilt table testing are mainly dependent on the ratio T/2h, CSV is shown to vary widely with h given constant T/2h;A furrow-trip analysis leads to the finding: that the length of the furrow and the characteristics of the vehicle are sufficient to determine the minimum lateral velocity for rollover. The particular force generation mechanism of the furrow/tire interaction does not appear to be important;In view of the fact that the literature indicates that most fatal rollover accidents are multiple-quarter-turn events, the curb-trip and furrow-trip analyses are extended to determine the minimum lateral velocity to elicit a two-quarter-turn rollover. Notable findings from this analysis are that (a) two-quarter-turn minimum velocities are about twice as high as one-quarter-turn velocities, (b) two-quarter-turn velocities may order vehicles differently than one-quarter-turn velocities, and (c) a key factor in two-quarter-turn velocities may be the roof height of the vehicle. This result should call into question the use of one-quarter-turn measures as the sole indicator of the likelihood of any particular vehicle being involved in a fatal single vehicle rollover accident;Finally, this thesis addresses the sensitivity of various measures of rollover resistance to small parameter changes. The analysis indicates, as expected, that changes in track width and center of gravity height are very important. These are followed by changes in the suspension damping, the overturning moment of the tires, and the roll gain of the suspension.

DOI

https://doi.org/10.31274/rtd-180813-10095

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Yvonne Irene Katherine Lund

Language

en

Proquest ID

AAI9531766

File Format

application/pdf

File Size

155 pages

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