Study On Fretting Wear Of Involute Spline Coupling Used In Low Floor Transmission Gear Box

Low floor transmission gear box is the core component of modern urban rail and metro,and plays the role of traction and torque transmission in the operation of railway vehicles.Involute spline couplings are mechanical components used to transmit torque and rotatinal motion, and it is widely used in mechanical transmission system of low floor transmission gear box. Due to the compact structure of low floor transmission gear box, it is not convenient for routine maintenance, and the part of low floor transmission gear box connectted by involute spline coupling will harm the safety of the transmission system due to the influence of the fretting wear. Therefore, the study on fretting wear of involute spline coupling used in low floor transmission gear box is of great significance in understanding the fretting wear,spline coupling optimization design and improving the fretting wear resistance properties of spline couplings; at the same time, it is very important to improve the reliability and safety of low floor transmission gear box. The research content of this paper comes from Hunan province strategic emerging industries project “the development of 100% low floor transmission gear box” subproject "study on the fretting wear of involute spline coupling".This paper, based on finite element method, analyzed the fretting parameters of involute spline coupling used in low floor transmission gear box, and investigated the effects of different kinds of misalignment on involute spline coupling, and discussed the effect of tooth profile modification. As well as, the fretting wear test was carried out on the basis of the fretting parameters of the involute spline coupling in the angular misalignment. The main research contents of this paper are as follows:(1)The fretting frictional contact behavious of involute spline coupling were investigated, and the contact pressure and relative slip distributions were obtained, and the tooth surface frictional contact state and wear was analyzed and forecasted, as well as the influences of frictional coefficient on contact pressure, relative slip, frictional contact state and Ruiz parameter were analyzed. The contact pressure and relative slip distributions are uneven, and the maximum contact pressure and maximum relative slip decreases when frictional coefficient increases. The frictional coefficient has a significant effect on the tooth surface frictional contact state, and the Ruiz parameter increases with the increase of frictional coefficient.(2)The load distribution of spline coupling with angular misalignment, parallel misalignment and those two combined misalignment were investigated. The amount of angular misalignment increasing makes the load distribution less uniform between teeth, andthe contact stress concentration position changes. Load distribution among teeth exhibits a trigonometric functions under parallel misalignment, and the load concentration increases when the amount of parallel misalignment increases. In the presence of angular misalignment and parallel misalignment, the effect of parallel misalignment on load distribution is more obvious and angular misalignment affects less.(3)The profile modification of involute spline coupling was analyzed, and the effects of modified quantity and modified position were investigated, and the effect of profile modification on angular misalignment of involute spline coupling was considered. The contact pressure and contact length of modified spline coupling increases with the increase of applied torque. The maximum contact pressure first decreases and then increases when both of modified quantity and modified position increases, and the best modified quantity making the maximum contact pressure minimum increases with the increase of the amount of angular misalignment. The profile modification of involute spline coupling can effectively reduce the maximum contact pressure and the phenomena of concentrated contact stress, and improve the tooth surface contact pressure distribution, and mitigate the adverse effects caused by angular misalignment.(4)In order to study the effect of fretting parameters on the wear of the spline pair, the fretting wear test rig was designed on the basis of the fretting parameters of the involute spline coupling in the angular misalignment, and the fretting wear of involute spline coupling was studied by studying the fretting wear behavior of the materials on a simplified fretting wear apparatus. When the normal force is increased, the friction force becomes larger, the fretting displacement decreases, and the fretting wear is reduced. Nitriding, carburizing and lubrication can improve the fretting wear resistance properties of the materials.