Date of Award

7-2008

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Advisor

Mears, Laine M

Committee Member

Summers , Joshua D

Committee Member

Grimes , Lawrence W

Abstract

A new dimension of success in automotive supply is time-based competition. This especially comes to light in tire development, with companies striving to enhance the testing methodologies for reduction in development time. Modeling and development of off-road tires is particularly difficult due to a lack of quantitative descriptions of the operating environment for model validation. Off-road tire evaluation is subjective, expensive, site dependent, and testing of such tires is typically carried out under lower levels of control. The objective of this work is to create fundamental descriptions of pertinent composition based soil properties and to directly relate these properties to evaluate the tire performance. A major contribution of this research is to provide a quantitative measure of soil properties especially with respect to adhesion and plastic behavior. Two models are developed: one for soil strength and the other for adhesion, which are used to study the behavior of wet soil in a deformable channel.
For experimental testing, Geotechnical Engineering methods such as Sieve Analysis, Hydrometer Analysis, and Atterberg Limits Analysis are adapted on a smaller scale to evaluate fundamental soil properties such as texture, grain size distribution, composition and plasticity. Classical materials method such as compression testing is adapted in soil strength evaluation. Certain composition based properties for which no standard test exist, new testing methodologies are developed and prototyped.
The newly developed methodologies that are used to define the non-existing properties helped in validating the physics-based models. Statistical evaluation technique of multivariable regression is employed to find the best fit model applicable to a broad range of soil compositions.
These soil models can be combined with existing tire behavior models to better predict new off-road tire design performance, thus reducing prototype evaluation iterations, overall development time and development cost. An additional benefit of the new methodologies is the ability to quantitatively evaluate rapidly-manufactured tire tread samples rather than requiring full prototype production.

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