Thermal and misalignment effects on the operation of railroad bearings are examined. In the thermal analysis a finite-element model is being developed to examine the seizure process in railroad bearings as a function of speed, load, and lateral play. Maps will be developed that indicate seizure thresholds as a function of these variables. How adapter wear affects bearing life is also being examined through modeling of the adapter/bearing/axle assembly. Obtaining both linear and angular stiffness of these components is a major part of the modeling process.

Using a high-pressure tribometer, friction and wear behavior of various tribocontacts lubricated by a number of oil/refrigerant mixtures are examined. The main emphasis is on the friction characteristics at start-ups from rest. A dynamic model of the tribometer is being developed to examine what effects, if any, the flexibility of the spindle has on the observed friction behavior. The results obtained will be used to select contact materials and lubricants that give both low start-up and steady-state friction torques.

The main objective of the proposed research program is to identify effective methods for lubricating compressors of refrigeration systems using ozone-safe refrigerants. In working toward this objective, a number of candidate materials, especially aluminum, are experimentally investigated to determine their tribological behavior in fully or partially miscible oil-refrigerant mixtures under environments simulating compressor operation. Possible friction, wear, and seizure models will be examined to determine their usefulness in predicting tribological behavior of these mixtures.

Labyrinth seals are widely used to protect spindle bearings of machine tools from the ingression of metal chips and caustic coolants. With increasing spindle speeds, bearing failures have also increased due to seal failures. This project addresses the reliability of labyrinth seals through an experimental program in which both leakage and differential pressure across the seal are measured as a function of speed and temperature. The project will specifically focus on (1) understanding the failure mechanism(s) of current labyrinth seal designs, (2) exploring modifications to the present design to improve sealing, and (3) developing practical design guidelines for high-speed labyrinth seals.

A test stand is used to examine the performance characteristics of a visco-seal/face seal combination. The stand is capable of simulating conditions in the spindle cavity of production machine tools. The performance characteristics are based on the amount of coolant vapor in the test chamber obtained by measuring the relative humidity, chamber temperature, and chamber pressure relative to the lab atmosphere. Among the parameters examined include radial clearance, helix angle, length and groove depth of the visco-seal, and spindle speed.

Graduate student Richard Dessenberger and Professor Charles Tucker conduct an experiment to measure the maximum deformation in a glass-fiber mat used to reinforce composite materials. (Photo courtesy of the department.)

Research in Professor N. V. Sahinidis' lab emphasizes the development of new methods for discrete and continuous optimization aimed at solving fundamental problems in the sciences and engineering. Shown here (right to left) are Sahinidis with graduate students Joe Shectman, Ming-Long Liu, and Hong Ryoo.