The TEHL analysis of involute spur gears is a non-stationary problem. In this case, it is not only the load that varies, but entrainment velocity and contact geometry also vary as the gear teeth come into action. Moreover, surface roughness of gear teeth, and high shear stress behavior of solid-liquid lubricant vary significantly along the line of action. So it is very hard to get all these effects into a transient thermo-elastohydrodynamic solution for an involute spur gear.Gear problem has historically been solved with different simplifications. The numerical solution of elastohydrodynamic lubrication (EHL) problems was described by Dowson and Higginson (1969). Many numerical solutions have been solved in the area ranging from thermo-elastohydrodynamic (TEHD) lubrication problems to transient TEHL problems. Wang and Cheng (1981) made a Grubin-type analysis of involute spur gear transmissions and obtained the minimum film thickness at several points along the line of action. Hua and Khonsari (1995) developed an isothermal full transient solution for involute spur gear by neglecting dynamic load in the model. Later, a full isothermal transient non-Newtonian EHL solution to the Reynolds equation was obtained by Larsson (1997). Wang, Tong and Yang (2004) presented the formulation of the transient TEHL problem in spur gears. The results showed that transient condition affects significantly the film temperature and film thickness of lubricant in the contact region. Mongkolwongrojn and Panichakorn (2012) studied TEHL rough surface spur gears under sudden overloads. The results showed that the effects of rough surface and sudden overloads are significant as well as friction coefficient, film temperature and film thickness of lubricant in the contact region. Sayles and Ioannides (1988) his study showed that particles larger than the oil film thickness and softer than the interacting surfaces would also hurt the surface, and reduce the life of the tribopair. Khonsari, Wang, and Qi (1989) Abstract This paper presents the performance characteristics of rough surface spur gears under thermo-elastohydrodynamic lubrication (TEHL) with non-Newtonian solid-liquid lubricant based on a Power law viscosity model. The bi-phase lubricant contains oil with Molybdenum disulfide particles. The time dependent modified Reynolds equation, elasticity equation, powder load carrying capacity, and energy equation with initial conditions were formulated and solved numerically using a multigrid multilevel with full approximation technique for an involute spur gear. In this analysis, the normal load and overloads are applied on either two pairs or one pair of gear teeth respectively. The transitions from two pairs to one pair and vice versa are modeled as a step variation of load. The effects of solid particle concentration, diameter of solid particle and surface roughness were examined in the region along the line of action of the meshing gear. The results show that both solid particle concentration and surface roughness affect significantly ...
