球面滚子剪切增稠抛光优化实验

Optimization Experiment for Shear Thickening Polishing of Spherical Roller

目的研究球面滚子在剪切增稠抛光过程中,不同抛光参数对表面粗糙度的影响,获得滚子光滑滚动面,并优化抛光工艺参数。方法基于田口实验设计,以表面粗糙度Sa为评价指标,分析磨粒种类、磨粒浓度、抛光转速、抛光间距等4个抛光工艺参数对球面滚子剪切增稠抛光后表面粗糙度的影响。通过实验分析表面粗糙度Sa的信噪比结果,得出最优的参数组合,并通过摩擦磨损实验评价抛光表面的摩擦磨损性能。结果得到了优化的工艺参数,Al_(2)O_(3)与SiO_(2)混合磨粒的质量比为1∶1,磨粒的质量分数为10%,抛光转速为70 r/min,抛光间距为4 mm,抛光时间为30 min。在此优化的工艺参数下,球面滚子表面粗糙度Sa从(40±10)nm降至(8.51±2)nm。结论剪切增稠抛光可以有效地去除球面滚子的表面缺陷,且在抛光过程不会改变滚子的圆度,抛光后滚子表面的摩擦因数减小,表面不易发生氧化物堆积。采用剪切增稠抛光可以有效提高GCr15球面滚子的表面质量。

The work aims to study the effects of polishing parameters on the surface roughness in the shear thickening polishing(STP)process of spherical roller to obtain smooth surface of spherical roller and optimize the polishing parameters.The effects of four process parameters on the surface roughness of spherical were analyzed,including the types of abrasive,the abrasive concentration,the polishing speed and the polishing distance.Taguchi method was used in the experiment,and the surface roughness was used as evaluating indicator to analyze the influence of the four parameters.The signal-to-noise ratio(S/N)of experimental results was calculated to obtain an optimized combination of process parameters.The frictional wear properties of the polished surface were tested by friction and wear experiments.With the increase of the polishing speed,the polish efficiency increased firstly and then decreased,because the high centrifugal force caused by the high polishing speed resulted in a reduction of abrasive particles in the processing area.An increase in the concentration of abrasive can increase the number of abrasive particles involved in processing,but the concentration of abrasive particles also affected the rheological properties of the polishing slurry,the thickening effect of polishing slurry decreased with the increase of abrasive particle concentration,and the polishing effect was the best when the abrasive particle concentration was 10%.Polishing slurry with mixed abrasive of 1∶1 SiO_(2)/Al_(2)O_(3)can be more effective in removing workpiece surface defects compared with single Al_(2)O_(3)or SiO_(2)abrasive.On the one hand,nano-SiO_(2)enhanced the oxidation rate of the workpiece surface material in the acid polishing solution,and reduced the strength of the workpiece surface material.On the other hand,Al_(2)O_(3)abrasive grains and SiO_(2)abrasive grains further improved the mechanical removal rate of abrasive grains.The polishing distance affected the shear force of the polishing slurry in the processing area.When the polishing distance was 2 mm,the polishing slurry between the workpiece and the polishing tank was solid-like under the action of strong shear force,and cannot pass through the machining gap continuously,and the polishing slurry was completely blocked between the workpiece and the polishing tank.When the polishing distance was 6 mm,the shear force of the polishing slurry was weakened,and the shear thickening effect of the polishing slurry was reduced,resulting in a decrease in the polishing effect.Compared with the polishing distance of 2 mm and 6 mm,polishing slurry had better fluidity and thickening effect when polishing distance was 4 mm.Under the optimized polishing conditions with mixed abrasive of 1∶1 SiO_(2)/Al_(2)O_(3),abrasive concentration 10%,polishing speed 70 r/min,and polishing distance 4 mm,the surface roughness Sa of the spherical roller decreased from(40±10)nm to(8.51±2)nm in 30 minutes’polishing.STP can effectively remove defects on the roller surface and improve the surface quality,and the polishing process does not change the roundness of the roller.The friction coefficient of the roller surface after polishing is reduced,and less oxide layer is generated and accumulated on polished surface compared to the surface before polishing.The results show that STP method can improve the surface quality of spherical roller effectively.