Establishment of Non-Newtonian Thermal Elastohydrodynamic Lubrication Theory

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Isothermal elastohydrodynamic lubrication (EHL) theory has played an important role for improving the working performance, function and durability of machine elements having a concentrated contact between non-conforming surfaces. The basis of non-Newtonian thermal elastohydrodynamic lubrication theory has been established by reconsidering the isothermal EHL theory from the theoretical and experimental viewpoints which consider temperature distributions in all directions in the contact.1. The limitation of isothermal EHL analysis has been elucidated experimentally. It is also found that the EHL regime is divided into three types, i.e., over flooded, fully flooded and starved.2. By using transversely oriented ridges, the causes of surface failures have been discussed from experimental viewpoints. A non-Newtonian numerical analysis method for the thermal EHL problems in point contacts has been developed, and the effects of surface roughness on the film thickness profile, distributions of … More pressure and temperatures and the traction coefficient have been discussed. Furthermore, the effects of the surface roughness orientation and the ellipticity ratio of the contacts on surface failures have been discussed. Based on the oil film temperature measurements for rough-smooth surfaces, it has been proved that the oil in EHL contacts behaves as a non-Newtonian fluid.3. The film pressure distribution, which affects the rolling contact fatigue phenomenon, depends on the thermal conductivities of both contacting surfaces, slide-roll ratio and pressure-viscosity coefficient. The compressive heating plays a significant role on the traction coefficient at very low slide-roll ratios.4. The effects of impact loads under rolling/sliding conditions have been discussed.5. Tribo-characteristics under reciprocating motion have been discussed from experimental and theoretical viewpoints.6. Based on the results described in above, the mechanism of oil film breakdown of reciprocating seals, the mechanism of soot wear have been clarified, and a new device, which can detect the dielectric breakdown of the grease EHL film, has been developed. Less