本文選題：速精密 + 外圓磨削�。� 參考：《東華大學(xué)》2015年博士論文

【摘要】：中國2006-2020年的《國家中長期科學(xué)和技術(shù)發(fā)展規(guī)劃綱要》將極端制造技術(shù)列入國家重點(diǎn)支持的前沿技術(shù)領(lǐng)域。這不僅說明了極端制造的重要性,也反映出實(shí)現(xiàn)極高的磨削質(zhì)量與磨削效率等極端制造問題還需要更加深入的科學(xué)研究與工程實(shí)踐。正如德國磨削專家Konrad Giihring博士所言,高性能磨削從磨床、砂輪、冷卻和安全裝置、工件原始形狀到極端切削條件等,整個(gè)磨削過程和磨削系統(tǒng)都面臨著全新的挑戰(zhàn)。高速磨削中砂輪與工件接觸瞬間所發(fā)生的現(xiàn)象,涉及了力學(xué)、熱學(xué)、化學(xué)、材料學(xué)等多個(gè)學(xué)科,其中,由磨削速度和磨削力產(chǎn)生的大部分功率轉(zhuǎn)化為熱能,熱能引起的磨削表面熱效應(yīng)將直接影響工件的表面質(zhì)量和磨削效率。本文以高速精密外圓磨削為對象,開展了磨削熱及其監(jiān)控方法的仿真與實(shí)驗(yàn)研究,主要研究成果及創(chuàng)新點(diǎn)如下： (1)通過單顆CBN磨粒磨削TC4鈦合金的仿真研究,發(fā)現(xiàn)仿真給出的磨削弧區(qū)最高溫度實(shí)際上發(fā)生在磨屑和接觸剪切面上且其只有小于1μs級的短暫作用時(shí)間、工件磨削表面最高溫度一般僅為磨削弧區(qū)最高溫度的50-80%：實(shí)際的磨削弧區(qū)接觸弧長約為傳統(tǒng)幾何弧長計(jì)算結(jié)果的2倍；隨著砂輪線速度的提高,磨屑的斷屑次數(shù)增加。以上發(fā)現(xiàn),對高速磨削的相關(guān)仿真和實(shí)驗(yàn)研究具有一定的指導(dǎo)意義。 (2)提出了面向高速外圓磨削過程的磨削弧區(qū)多點(diǎn)溫度同時(shí)測試方法,發(fā)明和研制了相應(yīng)的溫度傳感器及測試系統(tǒng),以同時(shí)采集磨削弧區(qū)多個(gè)位置的實(shí)時(shí)溫度。通過考察TC4工件表面溫度監(jiān)測曲線的熱沖擊峰,可以有效的推算出外圓磨削時(shí)砂輪進(jìn)出弧區(qū)的時(shí)間,據(jù)此,提出和構(gòu)建了基于工件磨削表面實(shí)測溫度曲線熱沖擊峰的實(shí)際磨削弧長計(jì)算方法。經(jīng)過不同磨削工藝參數(shù)下TC4實(shí)驗(yàn)數(shù)據(jù)的統(tǒng)計(jì),實(shí)際磨削弧長計(jì)算結(jié)果大約是傳統(tǒng)幾何弧長計(jì)算結(jié)果的1.5-2倍,充分表明了磨削過程中塑性變形和熱變形對實(shí)際磨削弧長的重要影響。提出的實(shí)際磨削弧長計(jì)算方法可為預(yù)測磨削弧區(qū)溫度分布提供計(jì)算依據(jù)。 (3)基于溫度傳感器工程實(shí)驗(yàn)所獲得的工件表面溫度及其分布規(guī)律,構(gòu)建了相應(yīng)的磨削弧區(qū)熱流密度分布,發(fā)現(xiàn)了磨削弧區(qū)熱流密度分布的非對稱性,且與瑞利分布具有較高的擬合度。與二次曲線熱源模型相比,基于瑞利分布的外圓磨削熱源,熱流最高點(diǎn)更偏向磨削弧區(qū)的砂輪入口處,其距砂輪入口處大約40%弧長的位置,這一發(fā)現(xiàn)為進(jìn)一步改善高速外圓磨削的冷卻條件提供了理論依據(jù)�；谀ハ髁�(shí)驗(yàn)、實(shí)測的工件表面溫度和單顆磨粒仿真磨削中的磨屑平均溫度,構(gòu)建了高速外圓磨削弧區(qū)熱分配比的計(jì)算模型�；谌鹄植紵嵩茨Ｐ�、磨削弧區(qū)熱分配比的經(jīng)驗(yàn)公式、實(shí)際磨削弧長的計(jì)算公式以及磨削力的測試,提出了工件表面溫度的預(yù)測模型,為優(yōu)化設(shè)計(jì)磨削工藝參數(shù),控制磨削表面溫度提供了理論基礎(chǔ)。 (4)通過仿真與高速外圓磨削工程實(shí)驗(yàn),掌握了磨削工藝參數(shù)對熱力載荷的作用規(guī)律,以及它們對磨削質(zhì)量的影響規(guī)律,發(fā)現(xiàn)了難加工材料高速磨削的相關(guān)特性如下： 1)對于TC4等塑性難加工材料,隨著砂輪線速度提高,材料應(yīng)變率提高、磨削溫度提高,但應(yīng)力下降、磨削力有所下降。其中,材料應(yīng)變率的上升和應(yīng)力的下降是導(dǎo)致TC4磨削表面發(fā)生塑脆轉(zhuǎn)變、表面粗糙度得到改善的主要因素,同時(shí)也是斷屑次數(shù)增多、有利于提高材料去除率的根本原因； 2)對于SiC等脆性難加工材料,隨著砂輪線速度的提高,應(yīng)變率上升,磨削力下降,而磨削溫度在80m/s處出現(xiàn)拐點(diǎn),即高于80m/s后工件表面溫度有所下降。其中,較高的工件表面溫度是導(dǎo)致工件表面脆塑轉(zhuǎn)變的主要因素之一,即高速磨削工件表面溫度有利于減少脆性材料磨削表面微裂紋等損傷層,改善表面粗糙度； 3)在提高砂輪線速度的同時(shí),同比提高工件速度,可以降低工件表面溫度、控制由于磨削熱導(dǎo)致殘余拉應(yīng)力的生成比例、磨削燒傷等,改善和提高難加工材料的工件表面質(zhì)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.
【學(xué)位授予單位】：東華大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TG580.63

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本文編號：2090843