ME 383SLubrication, Wear Bearing Techn. （我383 slubrication,穿中欧和轴承。）.pdf

ME 383S-Lubrication, Wear Bearing Techn. M.D. Bryant January 17, 2006 1 Surfaces “If God created Solids, the Devil created Surfaces.” o Impression: surfaces flat simple o Reality: surfaces extremely complex o Surface properties depend on topography method history of surface formation surface bulk composition environment ME 383S-Lubrication, Wear Bearing Techn. M.D. Bryant January 17, 2006 2 Surface formation example o NaCl, FCC structure Bulk properties depend on crystal’s atoms Surface properties can depend on cleavage Cleavage plane influences surface properties: Short dashed (plane) exposes white atoms Long dashed (plane) exposes blue atoms Inclined (plane) exposes white blue atoms ME 383S-Lubrication, Wear Bearing Techn. M.D. Bryant January 17, 2006 3 Surface disrupts crystal structure ⇒ higher energy Unshared electrons Mechanical deformations o Bulk: large grains (single crystals) consistent with crystal structure lower energy levels o Smaller grains @ surface from intense deformations higher energy levels (1~100 µm) o Bielby amorphous layer (~100Å) from machining (work hardened, quenched, alloy mixtures) o Layer of compounds (~100Å): oxides, sulfides, etc. o Adsorbed layer via van der Waals forces: hydrocarbons, water, atmospheric impurities, etc. o Dust particles (~1 µm) ME 383S-Lubrication, Wear Bearing Techn. M.D. Bryant January 17, 2006 4 dust particle adsorbed, deposited layer