Tham khảo tài liệu 'volume 18 - friction, lubrication, and wear technology part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Fig. 16 Systems approach for analyzing friction and wear problems In Fig. 16 important losses include vibration elastic deflections heating surface alteration galling and even seizure. Vibration as an output of a sliding system often indicates that stick-slip behavior is prevalent. Noise is often the result of stick-slip behavior but a system that exhibits such behavior does not necessarily emanate noise. Although vibration may not be apparent on friction force traces it may show up on deflection or displacement transducers. This type of behavior from a sliding system is usually undesirable. Accurate measurement of vibration may require the use of accelerometers on one of the members of the sliding system. Likewise elastic deflection which can occur at a sliding interface may not show up on the friction force recordings this deflection may mean that the couple under study has unacceptable frictional characteristics. For example when several elastomers that were undergoing friction tests were slid on a paper counterface they bent over in the direction of motion the contact geometry was changed from the point contact of a hemispherical rider to a line contact of a bent hemispherical-ended rod. The friction force was apparently high enough to cause this deflection. Although heating is an obvious result of friction between sliding members it is often not measured. The temperature rise is often significant and it is easy to measure. The mechanical properties of plastics are susceptible to degradation by heating to relatively low temperatures. The temperature rise at a sliding interface is the result of the properties of the materials in contact in addition to the sliding conditions. It will be different for different couples that may have the same friction coefficient. Therefore for sliding systems that may be affected by frictional heating of the interfaces a valid friction test should record the temperature rise. Surface alteration is another important aspect of many
