Study On Anti-friction And Anti-stick-slip Performance Of Textured Sliding Guide Surface

Sliding guide is the key moving support part of machine tools.Its easy-wearing property and stick-slip phenomenon at low speed always affect working efficiency in application.To improve the lubrication condition and the anti-stick-slip performance of sliding guide,laser surface texturing(LST)technology for sliding guide surface is presented in this dissertation.Several types of micro-textures were fabricated by laser on the surface of sliding guide to improve the friction and lubrication characteristics of sliding guide surface,and to enhance anti-stick-slip performance of sliding guide under low-speed and heavy-duty working conditions.A new high performance laser micro-textured sliding guide has been developed.The main research contents and innovative results of this paper are concluded as follow:(1)Study on stick-slip mechanism of sliding guide.Based on the physical model of machine tool dynamic system,combined with the micro friction state of surfaces of the sliding guide and the Stribeck friction effect,the stick-slip phenomenon of sliding guide was analyzed theoretically.It is found that the stick-slip phenomenon caused by the change of friction force can be divided into two states: "move-stop-move" motion and "slow-fast-slow" motion.The "move-stop-move" motion is mainly caused by the sudden change in friction force.During the starting phase,the sliding part overcomes the static friction force of the adhesive state,and the difference of static and kinetic friction results in the stick-slip phenomenon.Another cause for the "move-stop-move" motion is the solid contact force.The solid contact force generated by the contact between the rough peaks on the upper and lower surfaces slows down the slding speed of the sliding guide until it stops,and then the elastic potential energy stored by the system drives the guide to move again.The "slow-fast-slow" motion is also caused by the increase of the solid contact force.The solid contact force generated by the contact between the rough peaks on the upper and lower surfaces slows down the movement of the slider,and then the elastic potential energy accelerate the slider.Therefore,the sliding guide can be divided into five phases from static to smooth motion state.Phase?is the "move-stop-move" stick-slip motion caused by the difference of static and kinetic friction.Phase?is the "movestop-move" stick-slip motion caused by furrows effect.Phase ? is the "slow-fast-slow" crawling motion caused by solid contact force.Phase ? is the smooth motion of the mixed lubrication region between the critical point of creep and the critical point of hydrodynamic lubrication rigeem.Phase?is the smooth motion of the hydrodynamic lubrication region.(2)Experimental study on stick-slip and tribological properties of surfaces with different micro-textured morphologies.On the Rtec Multi-Function Tribometer,AHRS IMU sensor was installed to simulate the starting process of the machine under low-speed and heavy-load condition.The creep behaviorsof the samples with different textured morphology were tested.The experimental results show that the occurance probability of stick-slip phenomenon is the smallest for the dimple sample.According to the actual sliding velocity variation,the severity of stick-slip phenomenon for different morphologies is ranked as follows: untextured sample >grooves mesh sample > bulge sample > dimple sample.In the wear test,the wear of the untextured sample was the severest which showed obvious spalling.The three textured samples showed different degrees of scratching.The area of the scratching area on different samples was ranked as follows: bulge sample > grooves mesh sample > dimple sample.According to the analysis of the time for different textures surface to enter the fluid lubrication regime,the micro-pit textured sample enter the hydrodynamic lubrication regime earlier than other samples,which indicates that the dimple-textured sample is more likely to generate hydrodynamic lubrication to inhibit stick-slip phenomenon.Therefore,considering comprehensively,the dimple-textured surface of sliding guide is optimal.(3)Numerical simulation of lubrication performance on the surface of a dimple-textured sliding guide.A theoretical model of surface lubrication of textured sliding guide was established to study the lubrication characteristics of slider in themovement.The influence of dimple texture on lubrication characteristics and the critical hydrodynamic lubrication point was studied by simulation.The influence of dimple texture on the critical point and average oil film thickness in the hydrodynamic lubrication phase is analyzed by numerical calculation of the hydrodynamic lubrication model of dimple-textured sliding guide in low-speed and full oil film state.(4)Experimental study on anti-stick-slip performance of dimple-textured sliding guide.According to the parameters of numerical simulation,the friction and wear tests were carried out to verify the results of numerical calculation and the anti-stick-slip performance of dimpletextured sample.It is found that the dimple-textured surface helps to move left the critical hydrodynamic lubrication point on the Stribeck curve significantly,which expands the range of the hydrodynamic lubrication regime.The slider can work in the hydrodynamic lubrication regime at a lower speed for a longer time.The dimple-textured sample improves the lubrication condition in the low-speed region.The fluctuation range of the friction force of the dimple-textured sample is lower than that of the untextured sample,and the maximum fluctuation difference of the friction force of the dimple-textured sample is reduced by 75%compared with that of the untextured sample.Compared with the untextured sample,the duration of fluctuation state of the dimple-textured sample significantly reduced.The stickslip duration reduced by 66.6%,and the continuous vibration time reduced by 60%,which improves the stability of COF.At the same time,the wear test shows that the wear grooves width of the dimple-textured sample is larger than that of the untextured sample,and the grooves depth of the untextured sample is significantly larger than that of the dimple-textured sample.Under the same working conditions,the surface wear resistance of dimple-textured sample has improved obviously.(5)Study on lubrication properties of dimple-textured surface of sliding guide.The oil film lubrication model of the dimple-textured hydrodynamic sliding guide is used for numerical simulation.The influence of topography parameters of dimple on the hydrodynamic characteristics of sliding guide is analyzed.Samples with different micro-dimple parameters were prepared,and the tribological characteristic tests were carried out to verify the numerical simulation results.The oil film pressure and oil film stiffness were taken as the performance index to analyze the influence rules of micro-dimple depth,area ratio and surface roughness parameters on them.It is found that the oil film pressure and oil film stiffness both increase first and then decrease with the increase of texture depth,and the optimal textured depth is approximately equal to the initial film thickness.The influence of the area ratio of microdimple on the hydrodynamic lubrication effect is closely related to the oil film thickness,and the optimal area ratio of dimple-texture should be selected from 10% to 15%.At the initial phase of hydrodynamic lubrication,the oil film pressure decreases with the increase of surface roughness Ra.And the longitudinal texture is beneficial to the formation of oil film pressure and the maintenance of oil film stiffness.(6)Experimental study on application of dimple-textured sliding guide.In order to verify the anti-friction and anti-stick-slip performance of the dimple-textured surface of sliding guide,a sliding guide performance test equipment was developed.By using the test equipment,comparative tests were carried out on the untextured sliding guide and the dimple-textured sliding guide at the speeds of 6mm /s,8mm /s,10mm/s and 12mm/s,respectively.It is found that under low-speed and heavy-load conditions,the dimple-textured sliding guide still keeps a relatively uniform oil film.At the same speed,the average COF of the untextured sliding guide is higher than that of the dimple-textured sliding guide.At the three test speeds,the dimple-textured sliding guide has no obvious stick-slip phenomenon,while the untextured shows stick-slip phenomenon.The average COF of the dimple-textured sliding guide decreases with the increase of speed.To sum up,by combining theoretical analysis,numerical simulation and experimental research,this paper systematically studied the anti-stick-slip and tribological properties of dimple-textured sliding guide,which provided theoretical support for the development of a new type of low-speed and heavy-load sliding guide.