应毛军红教授邀请，香港城市大学Patrick Wong教授将来机械学院进行一场学术交流。

标题:Solutions to the lubrication problem of zero-entrainment-velocity (ZEV) contacts

时间：2016年10月21日 下午4:00 – 6:00

地点：机械学院第三会议室

Abstract:

The current design of rolling ball bearings does not deviate too much from the striking design of Leonard da Vinci that was made more than 500 years ago. The basic structure of a rolling ball bearing consists of three major components namely (i) balls, (ii) raceways and (iii) a retainer (or cage). While the rolling balls and raceways are indispensable, the retainer may be not. The function of retainer is to evenly space out the balls. Taking away the retainer provides benefits including more rolling balls being able to be installed in the raceways i.e. providing a stronger and much simplified bearing structure. In fact, retainerless bearings (termed as full complement bearings) are available in the market for specific applications. The hindrance of its extensive application is the serious friction and wear problem created at the direct contact between the adjacent rolling balls. Kinematics at the ball contact is under the zero-entrainment-velocity condition (ZEV), wherein the two surfaces run with the same speed but in opposite direction. Theoretically, it creates serious lubrication problem. While one of these surfaces drags oil into the contact, the opponent surface moves the oil out. The resultant supply of oil to the ball contact is null. There is no effective solution about that. The current complement bearings only attenuate such problems with boundary lubricating film, hard surface treatment or using ceramic balls. However, these limit their use in low speed conditions. Recently, we have proposed two possible solutions to the problem. The talk will present the two ideas. One of them is based on the lubricant/solid boundary slip phenomenon and the other is the use of liquid lubricants with micro-nano-spherical particles.