高速精密外圆磨削热及其监控方法的研究与应用

发布时间：2018-07-02 20:37

本文选题：速精密 + 外圆磨削　；参考：《东华大学》2015年博士论文

【摘要】：中国2006-2020年的《国家中长期科学和技术发展规划纲要》将极端制造技术列入国家重点支持的前沿技术领域。这不仅说明了极端制造的重要性,也反映出实现极高的磨削质量与磨削效率等极端制造问题还需要更加深入的科学研究与工程实践。正如德国磨削专家Konrad Giihring博士所言,高性能磨削从磨床、砂轮、冷却和安全装置、工件原始形状到极端切削条件等,整个磨削过程和磨削系统都面临着全新的挑战。高速磨削中砂轮与工件接触瞬间所发生的现象,涉及了力学、热学、化学、材料学等多个学科,其中,由磨削速度和磨削力产生的大部分功率转化为热能,热能引起的磨削表面热效应将直接影响工件的表面质量和磨削效率。本文以高速精密外圆磨削为对象,开展了磨削热及其监控方法的仿真与实验研究,主要研究成果及创新点如下： (1)通过单颗CBN磨粒磨削TC4钛合金的仿真研究,发现仿真给出的磨削弧区最高温度实际上发生在磨屑和接触剪切面上且其只有小于1μs级的短暂作用时间、工件磨削表面最高温度一般仅为磨削弧区最高温度的50-80%：实际的磨削弧区接触弧长约为传统几何弧长计算结果的2倍；随着砂轮线速度的提高,磨屑的断屑次数增加。以上发现,对高速磨削的相关仿真和实验研究具有一定的指导意义。 (2)提出了面向高速外圆磨削过程的磨削弧区多点温度同时测试方法,发明和研制了相应的温度传感器及测试系统,以同时采集磨削弧区多个位置的实时温度。通过考察TC4工件表面温度监测曲线的热冲击峰,可以有效的推算出外圆磨削时砂轮进出弧区的时间,据此,提出和构建了基于工件磨削表面实测温度曲线热冲击峰的实际磨削弧长计算方法。经过不同磨削工艺参数下TC4实验数据的统计,实际磨削弧长计算结果大约是传统几何弧长计算结果的1.5-2倍,充分表明了磨削过程中塑性变形和热变形对实际磨削弧长的重要影响。提出的实际磨削弧长计算方法可为预测磨削弧区温度分布提供计算依据。 (3)基于温度传感器工程实验所获得的工件表面温度及其分布规律,构建了相应的磨削弧区热流密度分布,发现了磨削弧区热流密度分布的非对称性,且与瑞利分布具有较高的拟合度。与二次曲线热源模型相比,基于瑞利分布的外圆磨削热源,热流最高点更偏向磨削弧区的砂轮入口处,其距砂轮入口处大约40%弧长的位置,这一发现为进一步改善高速外圆磨削的冷却条件提供了理论依据。基于磨削力实验、实测的工件表面温度和单颗磨粒仿真磨削中的磨屑平均温度,构建了高速外圆磨削弧区热分配比的计算模型。基于瑞利分布热源模型、磨削弧区热分配比的经验公式、实际磨削弧长的计算公式以及磨削力的测试,提出了工件表面温度的预测模型,为优化设计磨削工艺参数,控制磨削表面温度提供了理论基础。 (4)通过仿真与高速外圆磨削工程实验,掌握了磨削工艺参数对热力载荷的作用规律,以及它们对磨削质量的影响规律,发现了难加工材料高速磨削的相关特性如下： 1)对于TC4等塑性难加工材料,随着砂轮线速度提高,材料应变率提高、磨削温度提高,但应力下降、磨削力有所下降。其中,材料应变率的上升和应力的下降是导致TC4磨削表面发生塑脆转变、表面粗糙度得到改善的主要因素,同时也是断屑次数增多、有利于提高材料去除率的根本原因； 2)对于SiC等脆性难加工材料,随着砂轮线速度的提高,应变率上升,磨削力下降,而磨削温度在80m/s处出现拐点,即高于80m/s后工件表面温度有所下降。其中,较高的工件表面温度是导致工件表面脆塑转变的主要因素之一,即高速磨削工件表面温度有利于减少脆性材料磨削表面微裂纹等损伤层,改善表面粗糙度； 3)在提高砂轮线速度的同时,同比提高工件速度,可以降低工件表面温度、控制由于磨削热导致残余拉应力的生成比例、磨削烧伤等,改善和提高难加工材料的工件表面质量。
[Abstract]:The outline of China's 2006-2020 year plan for the development of science and technology in the middle and long term is to include extreme manufacturing technology in the frontier technology field, which is mainly supported by the state. This not only illustrates the importance of extreme manufacturing, but also reflects the need for further scientific research and work to achieve extreme manufacturing problems, such as high grinding quality and grinding efficiency. Practice. As said by Dr. Konrad Giihring, a German grinding expert, high performance grinding from grinding machines, grinding wheels, cooling and safety devices, the original shape of the workpiece to the extreme cutting conditions, the whole grinding process and the grinding system are facing new challenges. The phenomenon of the contact between the grinding wheel and the workpiece in high speed grinding involves mechanics, In many subjects, such as heat, chemistry, and material science, most of the power produced by grinding speed and grinding force is converted into heat energy. The surface heat effect of the grinding surface will directly affect the surface quality and grinding efficiency of the workpiece. In this paper, the simulation and experiment of grinding heat and its monitoring methods are carried out in high speed precision external grinding. The main research results and innovation points are as follows:
(1) through the simulation study of grinding TC4 titanium alloy by single CBN abrasive particles, it is found that the maximum temperature of the grinding arc area is actually on the grinding and contact shear surface and has only a short time of less than 1 s. The highest temperature of the grinding surface is only 50-80% of the highest temperature of the grinding arc region: the actual grinding arc area is connected. The arc length is about 2 times that of the traditional geometric arc length calculation. With the increase of the speed of the grinding wheel, the number of chip breakage increases. It has some guiding significance for the simulation and experimental research of high speed grinding.
(2) a multi point temperature simultaneous measurement method for grinding arc area for high speed cylindrical grinding process is proposed. The corresponding temperature sensor and test system are invented and developed to collect real-time temperature of multiple locations in the grinding arc. The external circle grinding can be effectively calculated by investigating the thermal shock peak of the surface temperature monitoring curve of the TC4 workpiece. The calculation method of actual grinding arc length based on the thermal shock peak of the measured temperature curve of the workpiece surface is proposed and constructed on the basis of the time of the grinding wheel in and out of the arc area. The actual grinding arc length calculation results are about 1.5-2 times that of the traditional geometric arc length calculation results under different grinding parameters. The important effect of plastic deformation and thermal deformation on the actual grinding arc length during grinding process. The calculation method of actual grinding arc length can provide the basis for predicting the temperature distribution in the grinding arc.
(3) based on the temperature and distribution of the surface of the workpiece obtained by the temperature sensor engineering experiment, the corresponding heat flux distribution in the grinding arc region is constructed, and the asymmetry of the heat flux distribution in the grinding arc region is found, and it has a higher fitting degree with the Rayleigh distribution. Compared with the two curve heat source model, the cylindrical grinding based on Rayleigh distribution is used. The heat source and the maximum heat flow point to the grinding wheel entrance at the entrance of the grinding wheel, which is about 40% arc length at the entrance of the grinding wheel. This discovery provides a theoretical basis for the further improvement of the cooling conditions of the high speed cylindrical grinding. Based on the Rayleigh distribution heat source model, the empirical formula of the heat partition in the grinding arc area, the calculation formula of the actual grinding arc length and the testing of the grinding force, the prediction model of the surface temperature of the workpiece is put forward, which provides the optimum design of the grinding process parameters and control the grinding surface temperature. Theoretical basis.
(4) through simulation and high speed round grinding engineering experiments, the law of grinding process parameters on the thermal load and their influence on the grinding quality are mastered, and the characteristics of high speed grinding of difficult processing materials are found as follows:
1) for TC4 and other plastic refractory materials, with the increase of the grinding wheel speed, the material strain rate increases and the grinding temperature increases, but the stress drops and the grinding force decreases. Among them, the rise of material strain rate and the decrease of stress are the main factors to improve the surface roughness of the TC4 grinding surface, and also the broken chip times. The increase of number is conducive to improving the material removal rate.
2) for SiC and other brittle hard materials, with the increase of the speed of the grinding wheel, the strain rate rises, the grinding force decreases, and the grinding temperature has a turning point at the 80m/s, that is, the surface temperature of the workpiece decreases after the higher than the 80m/s. The surface temperature is beneficial to reduce the surface damage of brittle materials such as micro cracks and surface roughness.
3) in order to improve the speed of the grinding wheel, the workpiece surface temperature can be reduced, the surface temperature of the workpiece can be reduced, the proportion of the residual tensile stress caused by the grinding heat and the grinding burn are controlled, and the surface quality of the hard working material is improved and improved.
【学位授予单位】：东华大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG580.63

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