Effects Of Oil Distribution On Thermal Non-Newtonian Lubricating State Of Cylindrical Roller

Based on the starved lubrication in cylindrical roller bearings,investigation was carried out from theory and experiment.With the Elrod method,a thermal starvation model of elastohydrodynamic lubrication(EHL)line contact with Carreau rheological model was established and solved.Effects of the subsurface stress of thermal EHL starvation under high rotating velocity and extensive load were analyzed.Effects of oil-supply layer thickness on the lubricating properties were investigated with special oil-supply models.Starvation of the roller contact pair under the fixed amount of the oil-supply condition was studied experimentally.Firstly,based on the Elrod algorithm,a starved thermal EHL numerical model of infinitly-long line contact with Carreau rheological model was established.Effects of the inlet oil-supply thickness,the load and the rotating speed on the film pressure,the film thickness,the position of meniscus,and the temperature distribution of the film and the surface were studied.Results show that,with the decrease in the oil-supply thickness,effects of the load and the velocity on the film thickness weaken.In addition,in severe starved lubricantion,the film thickness is mainly determined by the inlet oil-supply thickness,and is not affected by the load and the velocity.Secondly,considering the subsurface stress,a starved thermal EHL numerical model of infinitely long line contact was established.Effects of the load,the inlet oil-supply thickness,and the slide-roll ratio on the maximum film temperature and the friction coefficient were investigated.Moreover,effects of the oil-supply thickness on the subsurface stress with different load were analyzed.Results show that,when the slide-roll ratio is small,effects of the load on the temperature and the friction coefficient are different.The subsurface stress is affected by the inlet oil-supply layer thickness.The subsurface stress under severe starvation condition is larger than that under fully-flooded condition.Compared to the heavy-load condition,the inlet oil-supply layer thickness has much more influence on the distribution of the subsurface stress under light-load condition.Thirdly,with three oil-supply models,i.e.,the constant oil-supply layer thickness,the overrolling effect of the roller,and the “end-high middle-low” oil supply distribution,the starved finite line thermal EHL model for the cylindrical roller contact pair was built.And the starved lubrication performance in the middle part and at the end part of the roller was investigated.Results show that,with the increase in the rolling number,the inlet oil-suply layer thickness decreases,the film thickness decreases,and the end effect weakens.In addition,the film pressure,especially the end pressure increases obviously.The mid-layer film temperature and the surface temperature increase,respectively.For the “end-high middle-low” model,the additional oil-supply layer thickness has an influence on the lubricating properties at the end part of the roller,however,it has almost no effect on the middle part of the roller.With the increase in the additional oil-supply layer thickness,the end film temperature increases and the end surface temperature decreases.Finally,the starvation experiment was carried out on the optical interference rig.Under starvation condition,the influence of the load and the rotating speed on the film thickness was analyzed.When the load and the velocity are fixed,effects of the oil-supply amount on the film shape and the meniscus position were carried out.Moreover the starved properties were compared between the middle and the end part of the roller with various lubricants.Results show that,under a certain amount of the oil supply,starvation is generated easily in the contact area with higher rotating speed,heavier load,and larger viscosity.When the contact area is already in starved lubrication,the velocity and the load have almost no effects on the film thickness,and the film thickness mainly depends on the amount of the oil supply.Different from the end part of the roller,starvation is generated early in the middle part of the roller because of the squeeze effect.In conclusion,the experimental results are coherent with the theoretical results.