Xiaohong Jia

The Effect of Wear on the Performance of a Rotary Lip Seal

Theoretical analysis, combined with experimental verification, is used to study the effect of wear on the performance of a rotary lip seal as characterized by the pumping rate and friction torque. The performance of a rotary lip seal is determined by the sealing lip surface microscopic characteristics and contact characteristics at the sealing zone. The variation of the contact characteristics with wear has been established based on the variation of the sealing lip profiles measured by using a trilinear coordinate measuring instrument. The impression method is used to copy the lip surface microtopography at different wear times and then an optical interferometer is used to measure the impression surface microtopography to obtain the variation of roughness with wear. The variations of the roughness, contact characteristics, and approximate contact temperature with wear are inserted into a mixed lubrication model to obtain the variations of the pumping rate and friction torque. A comparison of the simulated results with those from experimental measurement verifies the validity of the theoretical analysis.

INFLUENCE OF SURFACE POLISHING ON THE FRICTION BEHAVIORS OF NBR

An experimental study on the tribology behavior and mechanism of NBR-Steel pair has been carried out. Abrasive paper was used to polish the NBR surface. The influences of surface topography on the friction coefficient were investigated based on the block-on-ring tribometer. Results show that polishing with abrasive paper is an effective method to reduce the friction coefficient of NBR on steel. Superlubricity was also found in the test. A new method to explain the superlubricity based on the contact angle and surface molecular structure was put forward in this work. Abrasive paper polishing changes the surface asperities, so affects the contact angle, so as to influence the boundary limiting shearing strength, and then causes the superlubricity. During the friction process the microstructure obviously changed, along with mechanical breaking of the molecular chain.