A Study On The Steady Thermal EHL Design And Transient Iso-thermal EHL Characteristics Of Profiled Rollers

The widely used line contact friction pairs work mostly under lubrication conditions. The pressure, film thickness, and temperature distributions play important role in the performance and service life of such friction pairs. Therefore, crowning design is necessary to increase their load capacity and improve lubrication condition. In this dissertation, the line contact EHL of finite length is studied. Crowning designs based on steady thermal and transient isothermal EHL of profiled rollers are discussed. The effects of lubricants, applied load, velocity as well as crowning parameters on pressure, film thickness and temperature distributions are investigated. The pressure distribution and oil film structure of several types of non-steady state motion, including acceleration/deceleration, stop/start, rapid deceleration and oscillation are obtained. The main work is as follows:1. An effective, robust and stable algorithm is established based on the multi-level multi-integration technique and several numerical skills: introducing additive items to construct the temperature matrix, constricting the pressure and temperature in a reasonable range during the calculation process, and using the solutions of some similar operating conditions as the initial values for more severe operating conditions. Numerical trials show that convergent solutions could be obtained under severe working conditions (the contact pressures exceed 2.0 GPa and the length-width ratio of contact area is over 100). Using this algorithm, systematic and complete numerical simulations of the classical interferometry experiments by Wymer's group are carried out. The numerical and experimental results agree quite well with each other. Therefore, the reliability of the calculation program is verified.2. The steady thermal EHL behavior for cylindrical rollers with crown-profiled ends at heavy load is systematically analyzed, including the following aspects: the effects of crowning length and crowning radius; the effects of velocity, applied load and slip-slide ratio; and the effects of the Eyring non-Newtonian fluids. Moreover, the similarity of the pressure and temperature distribution is investigated to discover the influence of the crowning design on the temperature distribution. It has been concluded that, if the crowning parameters are suitable, such rollers could establish two times of constriction in the cylindrical direction, the...