Energy and Thermodynamically Based Approaches for Analysis of Damage in Contact Problems

<p>A novel methodology for analysis of damage in contact problems in presented. Two important categories of contact damage are studied, namely crack nucleation and adhesive wear. The proposed methodology is primarily based on the laws of energy and thermodynamics, and as such offers great advantages by unifying the analysis of damage in a variety of contact configurations. Crack nucleation is the first damage type analyzed. For this purpose, the line-contact fretting configuration is chosen. A thermodynamically-based continuum damage mechanics (CDM) approach is employed. Intense stress gradients in the contact region are found to be highly influential in the crack nucleation process. A methodology is proposed that identified the averaging zone as a function of the contact and loading parameters. The predicted crack nucleation lives are verified by comparing against the published experimental data for two different alloys. The utility of the proposed methodology is also investigated for the case of rough surface contact. The deterministic approach is employed to investigate the effect of roughness on the surface tractions and contact stresses. A special averaging technique, proposed for the case of smooth surface, is adopted. The predictions of the crack nucleation life for different roughness values are compared with relevant experimental data in literature, and confirm the validity of the analysis. Adhesive wear is another type of contact damage investigated. The study is carried out for three different contact conditions. These include disk-on-disk unidirectional dry sliding, pin-on-flat reciprocating dry sliding and pin-bushing grease-lubricated oscillatory sliding. It is shown that the wear rate is linearly related to the power dissipation as well as the entropy generation rate. The linear correlations are verified experimentally. Degradation coefficient is obtained and a simple approach is proposed for prediction of wear in dry sliding configuration. The proposed technique can be employed for prediction of wear in circumstances where the direct measurement of power dissipation is encumbered by practical limitations. Also investigated are the relationship between the system’s wear rate, power dissipation and thermal response. The wear-energy dissipation coefficient (WED) is identified as an important property of tribo-systems. The methodology relies on measurement of temperature rise in the sliding system. It is shown that the correlation between the frictional power dissipation and temperature rise can be obtained through thermal analysis of the system. The proposed methodology is shown to be capable of predicting the wear rate under a wide range of loading conditions.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

Mechanical Engineering

Year dc:date.available

2014

Author dc:creator

• Babaie Aghdam, Afshin

• friction
• energy approach
• thermodynamic approach
• entropy generation
• contact mechanics
• wear
• crack nucleation
• fretting
• surface roughness

Statement dc:rights

• withheld
• Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.

Identifier

etd-04042014-165531
https://repository.lsu.edu/gradschool_dissertations/1438

OAI identifier oai:identifier

oai:repository.lsu.edu:gradschool_dissertations-2437