SUBJECT: Ph.D. Dissertation Defense
BY: Matthew Siopis
TIME: Tuesday, December 9, 2014, 11:00 a.m.
PLACE: MARC Building, 201
TITLE: Wear at High Sliding Speeds and High Contact Pressures
COMMITTEE: Dr. Richard Neu, Co-Chair (ME)
Dr. Richard Cowan, Co-Chair (GTMI)
Dr. Jeffrey Streator (ME)
Dr. Scott Bair (ME)
Dr. Naresh Thadhani (MSE)


Metal on metal wear at high sliding speeds and high contact pressures results in the melting of one or both of the sliding solid bodies due to heat generated at the contact interface. Understanding the influence of sliding speeds, contact pressures and material properties on wear rates is important in developing predictive models for designing more efficient and effective engineering system components. Typical engineering applications subjected to these extreme conditions include ultrahigh speed machining, rocket sleds, large caliber cannon, and electromagnetic launchers. Sliding speeds on the order of 1,000 m/s and contact pressures in excess of 100 MPa are common in these applications and difficult to replicate in a laboratory environment. A unique wedge experiment using a minor caliber electromagnetic launcher has been developed and implemented to characterize wear deposition of a 6061-T6 aluminum sliding body on several different guider materials of varying mechanical and thermal properties at sliding speeds from 0 1,200 m/s and contact pressures from 100 225 MPa. Optical microscopy and 3D profilometry were used to characterize and quantify the slider wear. Three distinct wear regions, plasticity dominated, severe plastic deformation and melt lubrication were observed. Test results provided evidence that the aluminum slider contact interface was molten. Modeling of the experimental wear data showed a dependence on pressure and velocity and guider material properties, density and specific heat. A predictive wear model was developed for the melt lubrication region as a tool for designing components subjected to similar operating conditions.