本文選題：激光燒蝕 + 青銅金剛石砂輪　； 參考：《湖南大學(xué)》2016年博士論文

【摘要】：金剛石砂輪是超硬磨料砂輪的一種,相比于立方氮化硼(CBN)超硬磨料砂輪具有制造成本低,經(jīng)濟(jì)效益好等優(yōu)勢。因其進(jìn)行精密的整形和修銳困難,限制其優(yōu)異磨削性能的發(fā)揮。由于金剛石硬度極高,傳統(tǒng)的單一的修整方法是基于“硬碰硬”的加工修整,不適應(yīng)于青銅金剛石砂輪。激光修整技術(shù)集激光技術(shù)、材料加工技術(shù)、傳感器技術(shù)、精密磨削技術(shù)及計(jì)算機(jī)技術(shù)于一體,是一門多學(xué)科交叉的邊緣學(xué)科和新興的先進(jìn)修整技術(shù),具有廣泛的應(yīng)用。該技術(shù)其實(shí)質(zhì)是基于脈沖激光燒蝕機(jī)理,將聚焦后的高能脈沖激光束輻照于勻速轉(zhuǎn)動的砂輪表面,實(shí)現(xiàn)修銳與整形的合二為一,但目前仍有眾多問題急需解決。本文在國內(nèi)外研究的基礎(chǔ)上,結(jié)合青銅金剛石砂輪的本質(zhì)特點(diǎn),采用脈沖光纖激光對青銅金剛石砂輪進(jìn)行修整,深入的研究其機(jī)理,并對修整過程中出現(xiàn)的物理現(xiàn)象包括相爆炸效應(yīng)、蒸發(fā)效應(yīng)、等離子體特性以及傳熱效應(yīng)等進(jìn)行理論分析,在此研究基礎(chǔ)上,提出一種新型單切向液柱流脈沖光纖激光修整工藝方法,為燒蝕青銅金剛石砂輪提供理論指導(dǎo)與工藝優(yōu)化。首先,在現(xiàn)有的激光修整系統(tǒng)基礎(chǔ)上,使用脈沖光纖激光器作為修整中的加熱光源,搭建脈沖光纖激光燒蝕青銅金剛石砂輪試驗(yàn)修整平臺,闡述脈沖光纖激光修整砂輪系統(tǒng)及運(yùn)行工作流程,修整系統(tǒng)主要包括脈沖光纖激光器、外光路傳輸裝置、激光器控制器、二維移動平臺等組成。其次,脈沖光纖激光具有脈沖時間短、能量強(qiáng)等特點(diǎn),采用脈沖光纖激光修整青銅金剛石砂輪會出現(xiàn)一些新的物理現(xiàn)象,包括蒸發(fā)效應(yīng)、等離子體屏蔽效應(yīng)和相爆炸等物理過程,分析相爆炸對激光修整青銅金剛石砂輪產(chǎn)生的不利影響,并對相爆炸進(jìn)行理論研究；對脈沖光纖激光修整青銅金剛石砂輪表面形成等離子體機(jī)制進(jìn)行理論分析,提出脈沖光纖激光燒蝕青銅材料表面等離子熱電離和碰撞電離機(jī)制布居概率模型,得到二種電離機(jī)制作用下,形成等離子體布居數(shù)率,數(shù)值結(jié)果表明碰撞電離是脈沖光纖激光修整青銅金剛石砂輪形成等離子體的主要機(jī)制,電離的銅離子會形成黑色氧化物粒子,覆蓋在青銅金剛石砂輪表面；應(yīng)用等離子體氣體方程模型,數(shù)值分析等離子體膨脹速度與線度、吸收效應(yīng)及反沖壓力效應(yīng),結(jié)果表明等離子體吸收效應(yīng)小、反沖壓力低,實(shí)際激光修整中可以不考慮其影響,為脈沖光纖激光燒蝕青銅金剛石砂輪提供了理論指導(dǎo)。隨后,針對實(shí)際燒蝕青銅金剛石砂輪過程中,多脈沖激光修整青銅金剛石砂輪傳熱模型與單脈沖的基礎(chǔ)上建立的傳熱方程有著本質(zhì)區(qū)別,建立多脈沖光纖激光修整青銅金剛石砂輪傳熱物理模型,并對燒蝕青銅和金剛石分別進(jìn)行傳熱數(shù)值計(jì)算,得出相關(guān)條件下修銳青銅和整形金剛石各自激光功率范圍。依據(jù)傳熱數(shù)值結(jié)果,開展相關(guān)試驗(yàn),觀察多脈沖光纖激光修整青銅金剛石砂輪的地形地貌和測量修整后其表面凹坑深度值。理論與試驗(yàn)表明多脈沖光纖激光對青銅金剛石砂輪可實(shí)現(xiàn)整形和修銳的合二歸一,為多脈沖光纖激光燒蝕青銅金剛石砂輪工藝參數(shù)優(yōu)化提供理論指導(dǎo)。最后,應(yīng)用多脈沖光纖激光修整青銅金剛石砂輪傳熱物理模型,得到不同激光功率與青銅金剛石砂輪表面溫度演化曲線。試驗(yàn)觀察修整后青銅金剛石砂輪地形地貌,并對金剛石磨粒表面進(jìn)行拉曼光譜檢測,數(shù)值分析與試驗(yàn)結(jié)果一致表明脈沖光纖激光修整青銅金剛石砂輪表面會形成石墨化變質(zhì)層等缺陷。為克服青銅金剛石砂輪激光修整技術(shù)的不足和缺陷,提出一種新型單切向液柱流輔助脈沖激光修整青銅金剛石砂輪方法,在砂輪修整中首次運(yùn)用液流冷卻效果。采用單切向液柱流方法后,能避免脈沖高功率激光修整下金剛石出現(xiàn)熱傳導(dǎo)產(chǎn)生石墨變質(zhì)層等缺陷,修整后砂輪表面質(zhì)量高、地形地貌好,金剛石石墨化變質(zhì)層程度降低,為脈沖光纖激光修整青銅金剛石砂輪提供指導(dǎo)與工藝優(yōu)化。
[Abstract]:Diamond grinding wheel is a kind of super hard abrasive wheel. Compared with cubic boron nitride (CBN) super hard abrasive grinding wheel, it has the advantages of low manufacturing cost and good economic benefit. Because of its precision shaping and repairing, it restricts its excellent grinding performance. Because of the high hardness of diamond, the traditional single dressing method is based on "hard collision". The processing and trimming is not suitable for the bronze diamond grinding wheel. Laser dressing technology integrates laser technology, material processing technology, sensor technology, precision grinding technology and computer technology. It is a multidisciplinary interdisciplinary frontier subject and a new advanced trimming technology. The technology is based on pulse laser. The mechanism of ablation is to irradiate the focused high-energy pulsed laser beam to the surface of a uniform rotating grinding wheel to achieve the combination of cutting and shaping, but there are still many problems to be solved at present. On the basis of the research at home and abroad, this paper combines the essential characteristics of the bronze diamond grinding wheel, and uses the pulse fiber laser to carry out the bronze diamond grinding wheel. On the basis of the theoretical analysis of the physical phenomena including phase explosion effect, evaporation effect, plasma characteristics and heat transfer effect, a new single tangent liquid column flow pulse fiber laser dressing technology is proposed, which provides the ablation bronze diamond grinding wheel. Theoretical guidance and process optimization. First, on the basis of the existing laser dressing system, the pulse fiber laser is used as the heating source in the dressing. The experimental dressing platform of the pulsed optical fiber laser ablation of the bronze diamond grinding wheel is set up, and the pulse optical fiber laser dressing wheel system and the operating process are expounded. The dressing system mainly includes the pulse. Fiber laser, external optical path transmission device, laser controller, two-dimensional mobile platform and so on. Secondly, pulsed optical fiber laser has the characteristics of short pulse time, strong energy and so on. Using pulse fiber laser to repair the bronze diamond grinding wheel will appear some new physical phenomena, including evaporation effect, plasma shielding effect and phase explosion. The adverse effects of the phase explosion on the laser dressing of the bronze diamond grinding wheel are analyzed, and the phase explosion is theoretically studied. A theoretical analysis is made on the formation of the plasma mechanism on the surface of the bronze diamond grinding wheel by the pulse fiber laser. The plasma thermal ionization and collision ionization on the surface of the pulse fiber laser ablation of the green bronze material are proposed. The number rate of plasma population is formed by two kinds of ionization mechanisms. The numerical results show that collisional ionization is the main mechanism of shaping the plasma of the bronze diamond grinding wheel with pulse fiber laser. The ionized copper ions will form black oxide particles and cover the surface of the bronze diamond grinding wheel. The plasma gas equation model is used to numerically analyze the expansion velocity and linear degree of plasma, the absorption effect and the effect of the recoil pressure. The results show that the absorption effect of the plasma is small and the recoil pressure is low. The actual laser dressing can not take into account its influence, which provides theoretical guidance for the ablation of bronze diamond grinding wheel with pulse fiber laser. In the process of etching bronze diamond grinding wheel, the heat transfer model of the bronze diamond grinding wheel with multi pulse laser dressing is essentially different from the heat transfer equation established on the basis of the single pulse. The physical model of the heat transfer of the bronze diamond grinding wheel is set up by the multi pulse fiber laser, and the heat transfer of the ablation bronze and the diamond is calculated and the phase is calculated. According to the numerical results of heat transfer, experiments are carried out to observe the topography and geomorphology of the multi pulse fiber laser trimming the bronze diamond grinding wheel and the depth of the surface. The theoretical and experimental results show that the multi pulse fiber laser can be realized for the bronze diamond grinding wheel. The combination of plastic and repair is two, which provides theoretical guidance for the optimization of the process parameters of the multi pulse fiber laser ablation of the bronze diamond grinding wheel. Finally, the physical model of the heat transfer of the bronze diamond grinding wheel is repaired by multi pulse fiber laser. The surface temperature evolution curve of the different laser power and the bronze diamond grinding wheel is obtained. The experimental observation of the bronze after the dressing is made. The diamond grinding wheel is topographic and geomorphic, and the surface of diamond abrasive particles is detected by Raman spectrum. The numerical analysis and experimental results show that the surface of the bronze diamond grinding wheel will form the graphitized metamorphic layer on the surface of the bronze diamond grinding wheel. In order to overcome the defects and defects of the laser dressing technology of the bronze diamond grinding wheel, a new type of single cut is put forward. The liquid column flow assisted pulse laser is used to repair the bronze diamond grinding wheel. The liquid flow cooling effect is first used in the dressing of the grinding wheel. After the single tangential liquid column flow method, the defects of the diamond in the high power laser dressing can be avoided. The surface quality of the grinding wheel is high, the terrain and the geomorphology are good, and the diamond is good. The degree of graphitization deterioration decreases, providing guidance and process optimization for pulse fiber laser dressing of bronze diamond wheels.

【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TG743

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