摩擦学原理-薄膜润滑.ppt

Thin film lubrication and mixed lubrication in nano scale Contents Introduction Testing technology Properties of thin film lubrication (TFL) Failure of fluid films Lubrication model & map Contact ratio in nano-mixed lubrication Conclusion 1. Introduction (2) 1.3 Jost’s questions (Tribology 2000): What’s the definition of boundary lubrication? 1.4 Granick’s questions (Science, 1991) What determines the effective viscosity of such ultra-thin film? What makes the film change into solid state from liquid when it is enough thin? Why dose the solid film can endue a continuous sliding？ 2. Testing technology (1) 3. TFL properties 3.1 Film thickness v.s. influencing factors 3.2 Film thickness v.s. solid surface energy 3.3 Effect of running time on TFL 3.4 Effect of external electric field on TFL 3.5 Effect of nano-particles on TFL 3.6 TFL viscosity 3.1 Film thickness v.s. parameters Film thickness curve 3.2 Effect of time 3.3 Film thickness with substrates 3.4 TFL under external electric field 3.5 Film with nanoparticles (1) 4. The failure of liquid film (1) 4. The failure of liquid film (2) (1) L=?kv0.69 (2) Lf =23.5?10-4Pf2 5 Lubrication model and map(1) 5 Lubrication model and map (2) (3) Effect of viscosity (4) Effect of surface roughness 6.3 Deformation of asperities 7. Conclusions (1) Thin film lubrication (TFL) is a new lubrication regime between boundary lubrication and EHL; In TFL, film thickness is not only related to fluid factors, but also to the physical and chemical properties of solid surface and lubricants; In TFL, electric voltage has influence on the film thickness in the nano scale. 7. Conclusions (2) The increase of lubricant viscosity and speed, the addition of polar additives, and the decrease of pressure will reduce the dynamic contact ratio. The contact ratio between the rough surfaces is larger than that between smooth surfaces at higher speed, but its varying rate is smaller than that of smooth surfaces. Collision of a particle