Gregory F. Simmons

Tribological behaviour of polymeric materials in water-lubricated contacts

This study aims at investigating the tribological behaviour of several unfilled polymer materials sliding against 316L stainless steel in distilled water. The tests were carried out in a unidirectional pin-on-disc configuration with an initial apparent contact pressure of 5 MPa at room temperature. The worn surfaces were examined using scanning electron microscopy and energy dispersive spectroscopy techniques and the wear mechanisms were discussed. These studies indicate the occurrence of tribocorrosion of stainless steel during sliding against polypropylene. It is inferred that the frictional behaviour of the polymers is determined by both their wettability and solubility in water, where generally an increased hydrophobicity and relative energy difference with regard to water results in lower friction. The results from friction and wear tests show overall superior tribological performance of ultrahigh molecular weight polyethylene compared with the other polymeric materials in water.

Steady state and dynamic characteristics for guide bearings of a hydro-electric unit

Experiments are conducted using a 10-MW Kaplan hydropower machine which is outfitted with an extensive array of sensors to determine oil film thickness, pad load and oil temperature in all three guide bearings as well as motion of the shaft in relation to both the bearing housings and the concrete foundation. Test results for all journal bearings are compared to a commercial rotor dynamics model and results for the central journal bearing are compared to a multi-physics model to provide insight into the machines steady state and dynamic characteristics and their variations during normal operation.

POWERPLANT LUBRICANT SELECTION FOR IMPROVED EFFICIENCY AND ENVIRONMENTAL IMPACT REDUCTION

Computational models were used to optimize bearing per-formance by adjusting a number of lubricant properties. Thiscomputational optimization showed that the most beneficialcharacteristics to hydro ...