基于静电喷雾的金刚石磨粒微表面均布特性研究

目的改善精密/超精密成形磨削中砂轮存在磨粒分布不均匀的问题。方法仿真分析针-环电极空间电场强度的分布特性,以及喷嘴轴线上场强随喷嘴直径、环状电极直径、电极间距的变化规律。金刚石磨粒均匀分散在静电喷雾溶液中,在高压电场和压力泵的作用下将喷出形成微表面。通过网格分析法和截距法定量分析金刚石颗粒微表面分布的均匀性。结果针-环电极产生的空间电场是对称分布的,电场线集中分布在喷嘴附近,其电场强度沿轴线向外急剧降低。由于尖端效应,喷嘴直径减小,其尖端处的电场强度明显增大;电极间距增大,喷嘴处的场强降低。网格计数法中,网格划分得越细,微表面颗粒分布偏差越大,即分布均匀性越差,但更能反映真实的颗粒整体分布情况,且各偏差曲线分布的趋势基本相同,仅在液体流量20 m L/h处出现了与理论的变化规律不符合的情况。截距法中,当液体流量增大时,颗粒间距离偏差值逐渐降低,且在液体流量20 m L/h处明显下降。结论在金刚石颗粒微表面分布的定量化分析中,网格计数法只能体现区域分布的均匀性,而对某块区域内颗粒的距离不敏感,无法区分颗粒聚集的情况,导致计算结果出现偏差。截距法则对颗粒的间距比较敏感,因此有效地结合网格计算法和截距法可以对金刚石磨粒的分布情况做出准确分析。

Uniform Distribution Characteristic of Fine Diamond Abrasive Particles Based on High Voltage Electrostatic Spraying

The work aims to improve uneven distribution of abrasive particles in grinding wheel duringprecision/ultra- precision forming grinding. Distribution characteristic of space electric field intensity was simulatedforneedle-ring electrode. Variationof field strength on axis with the nozzle diameter, diameter of annular electrode and electrode gapwasanalyzed. The diamond abrasive particleswereevenly dispersed in electrostatic spraying solution, which wouldform a micro surface under the action of high voltage electric field and pressure pump. The micro-surface distributionuniformity of diamond particles was quantitatively analyzedingrid analysismethod and intercept method. Theelectric field produced by needle-ring electrode was symmetrical, and electric field line was concentratedly distributed near the nozzle. Its electric field intensity decreased sharply outward along the axis. Because of tip effect, the nozzle diameter decreased, and the electric field intensity at the tip increasedobviously. The electrode gap increased and field strength at the nozzle decreased. In grid counting method, when the grid wasfine, particle distribution deviation of micro surface was greater, and the distribution uniformity wasworse. However, the method could reflect real situation of overall particledistribution, and distribution trends of deviation curveswerebasically the same. The situation appeared at the liquid flow of 20 mL/h wasnot consistent with theoretical variation. In intercept method, when the liquid flow rate increased, the distance deviation between particles decreasedgradually, and decreased obviously at the liquid flow rate of 20 mL/h. According to quantitative analysis of diamond particles micro surface distribution, grid counting method can only reflect regional distribution uniformity, but itis not sensitive to particle spacingina certain region and cannotdistinguish¬particle segregation, which leads to deviation in results. The intercept method is sensitive to particle spacing.The distribution of diamond particles can be accurately analyzedinthe combination of grid counting method and intercept method.