Research On Polishing And Friction And Wear Properties Of TC4 Artificial Joint Ball Head

At present,the field of biomaterials has become a crucial field.Titanium alloy(TC4)is widely used in biomedical implants due to its good mechanical comprehensive performance and biocompatibility,but the mechanical processing performance of titanium alloy is poor.It is still a difficult problem to obtain high surface quality and dimensional accuracy.In this paper,the experimental machine is designed to study the contact mechanical characteristics of the ball and socket,the friction and wear of the spherical tool,and the fluid characteristics of the polishing fluid film.First of all,because the surface polished by the titanium alloy ball head is a spherical surface,the polishing experiment machine is designed independently.The polishing experiment machine can realize the compound motion of rotation and swing to process the workpiece.The reliability of the test bench mechanics,and during the polishing process,it can effectively avoid the resonance phenomenon,and at the same time can realize the real-time collection of friction torque during the polishing process,and analyze the friction and wear characteristics during the polishing process.Then,using the experimental machine model as a prototype,a ball head-tool ball and socket model was established,and the effects of load,tool ball and socket thickness on the contact mechanics were explored.After the load is applied,the maximum value of the stress is distributed in the subsurface layer of the ball head and the ball socket;as the load increases,the stress distribution area of the ball head and ball socket gradually increases,and the maximum contact pressure also continues to increase,but the load and the contact stress The relationship is not nonlinear;as the thickness of the ball socket increases,the maximum stress at the crosssection continues to decrease and gradually smooth;When considering the friction between the ball head and ball socket,the contact pressure is increasing with the increase of the friction coefficient,but the increase is not significant;the ball head-ball socket gap has a greater influence on the cross-sectional stress and contact stress.The larger,the smaller the contact area,the more concentrated the stress distribution,and the larger the shape change of the ball socket.Next,explore the speed change,pressure change and relative wear change of any point on the tool during the polishing process,and select the appropriate ratio of rotation speed to pendulum speed.For different points at the same latitude and different longitudes,during the polishing process,their speed and pressure change trend is basically the same,mainly slightly different in phase,their relative wear is basically the same;for different points at the same longitude and different latitudes In the polishing process,the higher the latitude and the higher the speed,the greater the normal pressure.The relative wear increases first and then decreases as the latitude increases;Based on the difference in the relative wear at the same point at different speeds and pendulum speeds,observe the density of the polishing trajectory at six points at the same longitude and find that the density is not a monotonous change.Comprehensive experimental machine parameters Considering that the ratio of tool rotation speed to swing speed i is 37.Finally,CFD simulation was used to study the effects of compound motion,fluid film thickness and perforated polishing pad on flow field characteristics.Under compound motion,the velocity of the flow field near the bottom of the ball socket is small,and the pressure in the film flow field exists both in the case where the pressure is greater than zero and the pressure is less than zero,where the negative pressure is mainly concentrated in the lower half of the fluid film Area;as the thickness of the fluid film increases,the change trend of the fluid velocity is basically the same,but the fluid velocity rises or falls more smoothly,there is a certain hysteresis in the velocity change,and within a certain range,the smaller the fluid film thickness,the fluid pressure The smaller;when considering the polishing pad with holes,it is found that after adding small holes,the fluid velocity is slightly reduced,the maximum negative pressure of the fluid at the same reference point is slightly reduced,and a positive pressure appears at some reference points,which makes the flow The change of pressure in the field becomes more complicated,which is beneficial to the polishing.