Numerical Simulation Of Ehl Problem Under Intermittent Condition

In this paper, the variations of the squeeze elastohydrodynamic lubrication(EHL) oil film in unidirectional and bidirectional intermittent motions are investigated theoretically using the multi-grid method and multilevel multi-integration technique firstly. It is found that the variations of the central pressure, central and minimum film thickness in intermittent motion which has a short cycle and a big deceleration resemble those in an impact-rebound process,an oil entrapment was formed in stopping period. But in long cycle interment motion with low deceleration, the variation of the oil film is very different.For the unidirectional intermittent motion, the effects of stop time, deceleration, elliptical ratio et al. are explored. The pressure increases with the increase of stopping time, and the corresponding film thickness decreases. The pressure and film thickness all decrease with the increase of the elliptical ratio, but increase with the increase of the entrainment velocity. For the same umax, the decrease of the time of deceleration makes the film does not have enough time to decay. Therefore, when the deceleration is bigger, the oil film is thicker, but the peaks of central pressure and maximum pressure are higher. And a second pressure peak appears when the deceleration is big. It is also found that the bidirectional intermittent motion is more detrimental to the contact metals so that special attention should be paid in the design.With numerical techniques, the effect of starvation on EHL characteristics in intermittent motion was studied. The pressure and oil film decrease with the increase of starvation. With the increase of the starvation, the influence on pressure increases,and the influence on oil film decrease following an obvious increase.At last,the effect of starvation on isothermal elastohydrodynamic lubrication(EHL) characteristics of a squeeze motion is explored. Compared with fully lubricated results, the values of central pressure, central film thickness and minimum film thickness are smaller. The trend of the central pressures of the two oil supplied conditions is similar, but with the effect of starvation, the variations of central film thickness and minimum film thickness are different. Moreover, the whole impact-rebound process is extended.The influence of the ball falling height and intial oil film thickness on oil characteristics in impact process under the two oil supplied condtions are explored at the same time. The increase of the initial film thickness makes the impact process longer. Under starved conditon, the values of pressure and film thickness increase following the increase of the initial oil film thickness. While they do not change their trend with the variation of the initial oil film thickness in fully lubricated results. The only change is the time when the oil characteristics vary obviously. The pressure and film thickness increase with the increase of ball falling hight when fully lubricated. But the central and minimum film thicknesses change little with the increase of ball falling hight under starved condition.