# AAE 55900: Mechanics of Friction and Wear

 Description Introduction to tribology. Review of elasticity and Hertzian contact. Analytical and numerical methods for non-Hertzian contact, including frictional and elastic-plastic contact. Surface roughness. Friction laws and frictional heating. Wear models and wear testing. Lubrication. 3 hrs lecture per week 3 Elective, Structures Alternate Spring Semesters AAE 204 and MA 303 or equivalent None Prof. Farris Johnson, K.L., Contact Mechanics, Cambridge, 1985. ISBN 0-521- 25576-7 Weekly Homework (40%), Mid-term Exam 1 (20%), Mid-term Exam 2 (20%), Special Project (20%). Grading policy is an instructor option and may vary.

## Course Goal & Objective:

### Goal:

The goal of AAE 559 is to develop the underlying physical principles necessary for the understanding of friction and wear. This leads to the ability to analyze friction, lubrication and wear in aerospace and mechanical systems

Objectives include developing abilities to:

Describe the topography and mechanical properties of engineering surfaces

Develop and solve the equations of elasticity that relate loads applied to contacting bodies to the resulting stress and deformation

Characterize plasticity and shakedown of contacting solids loaded above the elastic limit

Relate contact induced deformation to friction and resulting frictional heating and wear

### Necessary Background:

1. Differential equations
2. Mechanics of materials and introduction to the elasticity

### Topics (number of 50 minute Lectures):

1. Introduction to friction and wear in aerospace engineering and modern experimental tools; History of tribology (2 lectures)
2. Elastic Contact: Equations of elasticity; Hertzian contact; Numerical approach to integral equations used to describe contacts (12 lectures)
3. Plasticity: Yield criteria; elastic-plastic deformation; shakedown of repeated contacts (6 lectures)
4. Surface topography: Statistical characterization; rough surface contact (4 lectures)
5. Friction: friction laws; frictional and fretting contacts; frictional heating (9 lectures)
6. Wear: wear models and wear testing (6 lectures)
7. Lubrication: Reynolds equation (3 lectures)

### Relationship of course to program objectives

This elective course supports AAE objective (1) by providing students with advanced concepts, theories and approaches used to analyze and design contacts in aerospace structures. Several homework assignments require students to use computers to address open-ended problems (2a). The final project generally has a research component that requires students to develop life-long learning skills (3) and requires both written and oral reports (2c). Examples of contact induced fatigue failures in airframes and aircraft engines emphasize the social impact of engineering solutions (4).

Prepared by: T.N. Farris

Date: March 20, 2001