Tham khảo tài liệu 'volume 18 - friction, lubrication, and wear technology part 16', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Fig. 6 Variation in wear of carbon brake from taxi to RTO energies Each of the three energy ranges has its own wear mechanism. The taxi region exhibits the highest wear and mechanical abrasion predominates. In the mid-energy service energy region wear is lowest because a thin film protects the substrate. The third region occurs when temperatures are sufficiently high to produce oxidation of any debris or substrate fiber or matrix . Oxidation usually occurs during overload and RTO conditions. PAN-base fibers wear differently than pitch-base fibers these differences are associated with fiber processing as well as composite processing. A harder matrix will wear less than a softer one. Studies have shown that circumferentially oriented fibers have high wear and a high coefficient of friction. Wear Mechanism and Wear Debris Analysis. The worn surfaces of the carbon materials have bands of different reflectance when observed via macro examination. Debris material occurs in both bright and dull bands. The observed banding on the wear surface of the composite is related to variations in reflectance these variations are thought to be related to differences in the character of the wear debris. The bright bands consist of a thin film of debris with a polished appearance that produces a high reflectance. The dull bands have a high number of fissures or shallow grooves and scratches in the longitudinal fiber bundles both of which are indicative of fiber removal caused by abrasion. The debris material in the dull bands does not produce a high reflectance and appears less dense more porous than the bright bands. The debris in the dull bands is particulate and is comprised of fibers and matrix. This debris does not form a film but fills in the original porosity mainly in the matrix and is found primarily under low-energy conditions. The debris in the bright band consists of a thin film up to a few micrometers thick that is smeared over fibers and matrix and also fills in the .
