Gear Thermal Elastohydrodynamic Lubrication Based On Non-Newtonian Fluid

Taking into account thermal and non-Newtonian effects of the lubricant, this paper has theoretically investigated Elastohydrodynamic Lubrication of involute spur gears, and achieved the pressure distribution, film shape, temperature distribution and the values of the friction coefficient and its varying law along the line of action of gear transmission.By means of C-language, the paper has developed a large-scale computer program, in which the combination of both the Newton iteration and the gradient method is introduced to solve Reynolds equation and film thickness equation, and the march method is used to solve the energy equation and heat interface equations, The satisfactory results are obtained. This program is applicable in the following ranges: dimensionless velocity parameterU being from 10-12 to 10-10 , dimensionless load parameter W from 10-5 to 10-3, and the rate of slide to roll S less than 0.1, which, except for S, can involve the practical applications of industry gear drives. So, thismethod has cured the chronic disease--the problem of theconvergence being difficult when Newton method is used to solve the EHL problems under the conditions of the high speed and heavy load. It is one of the main achievements of this paper.Applying the computer program developed by this paper, and choosing the real values of the gear transmission, this paper has completed more than 50 sets of calculations of the thermal Elastohydrodynamic Lubrication based on the non-Newtonian fluid. The following conclusions can be drawn according to the computational results:1, When the gear teeth are engaged at the pitch point, the changes of both the gear rotational speed and the load have little influence on the pressure distribution and the film shape, but they have large influence on the film temperature distribution. Given the rotational speed of thedriving wheel, the temperature in the contact zero rises evidently as the load is increased. Given the load, however, this temperature rises faintly as the rotational speed of the driving wheel increases. When the modulus is small and rational rate is high, the change of the rational speed and load have the apparent influence on the temperature distribution, but when the modulus is larger and rational rate no larger than 1.0, the above changes have negligible influence on the temperature distributions.2, The friction coefficient at the pitch point is not a monotonic quantity of the rational speed or the load, instead of having a maximum value. And the value of the friction coefficient is very small, its order of magnitude only being 10-3. So, it is reasonable that the friction force on teeth surfaces are ignored when the gear-driven contact fatigue strength is designed.3, During the process of the gear teeth meshing, the film shape and pressure distribution have little difference. But, the temperatures have the distinctive changes as the engaged position is varied, which means that thetemperatures as the increase in the rate of slide to roll. The friction coefficient is up to its maximum value of 0.08, at two points where the transitions from two pairs of gear teeth to one pair and vice versa take place. It means that the maximum friction force is at the positions of neither the approach nor the recess point, which is an original conclusion of this paper.This paper has the following deficiencies:1, The dynamic load of the gear transmission isneglected in the numerical calculations; 2, The results of this paper are in need of being verified by the experiments.