本文選題：冷等離子體 + 超聲橢圓振動�。� 參考：《大連理工大學》2017年博士論文

【摘要】：缺乏抑制刀具磨損的有效方法是制約黑色金屬金剛石超精密切削技術進步的瓶頸問題。論文提出利用冷等離子體射流的載能活性粒子比碳原子更易與鐵原子快速結合形成更強化學鍵和冷卻潤滑效果好的特點,將其施加于切削界面,實時降低刀-工界面的化學親和性和改善切削區(qū)的熱力作用,從而抑制金剛石切削黑色金屬時的刀具磨損,穩(wěn)定加工過程和提高加工質量。論文在分析金剛石刀具磨損及抑制磨損機理的基礎上,首先研制了冷卻潤滑效果好、易輸送至刀-工接觸界面進行特性調(diào)控的大氣壓冷等離子射流,然后采用分子動力學、熱分析、摩擦磨損等理論和試驗方法研究了冷等離子體射流輔助切削的作用機理,最后進行了基礎的切削試驗。論文的主要研究工作如下:為從降低刀-工界面化學親和性和改善切削區(qū)的熱力作用兩個方面抑制金剛石刀具的磨損,研制出溫度較低、易輸送至刀-工接觸界面、適用于輔助切削的大氣壓柔性冷等離子射流。研究發(fā)現(xiàn),氮氣作為工作氣體適合于裸電極放電產(chǎn)生冷等離子體射流,并且頻率對氮氣放電的伏安特性影響較明顯,而氣流量對氮氣放電的伏安特性影響較小。采用柔性等離子體射流方案可實現(xiàn)等離子體的有效輸送,柔性射流的長度隨驅動電壓和氣體流量的增大而增加,且與普通冷等離子體射流具有相似的伏安特性。渦流管對工作氣體預冷卻可降低等離子體射流的溫度,且流量越大射流溫度越低;而驅動電壓的升高會提高等離子體射流的總體溫度。因此,借助渦流管通過調(diào)節(jié)流量和放電電壓可得到溫度在一定范圍內(nèi)可控的等離子體射流。特別的,當驅動電壓為3.0 kV、流量為50 L/min時,柔性氮等離子體射流的整體溫度可低至-7 ℃。通過分子動力學模擬和熱分析試驗,得出氮冷等離子體可降低黑色金屬對金剛石的化學親和性。分子動力學模擬的結果顯示,金剛石石墨化的溫度在1200 ℃～1700 ℃之間,但在鐵原子的催化作用下,金剛石石墨化的溫度可降低至約773 ℃。熱分析試驗則證明,未經(jīng)氮冷等離子體處理的NAK80/金剛石接觸界面上金剛石石墨化溫度為882 ℃,而經(jīng)氮冷等離子體處理的試樣在1185 ℃時才出現(xiàn)明顯的石墨化。即鐵原子會降低金剛石的石墨化溫度,而氮冷等離子體處理后黑色金屬/金剛石界面上的金剛石石墨化溫度又會提高。結果表明,NAK80表面和晶界會吸附大量活性粒子,并與黑色金屬反應生成與金剛石化學親和性較低的氮化物,最終達到抑制金剛石石墨化磨損的目的。為驗證冷等離子體改善切削區(qū)熱力作用的效果,在空氣射流、氮氣射流和氮冷等離子體射流氛圍中進行了 NAK80/金剛石摩擦副的摩擦磨損試驗。結果表明,氮氣射流和氮冷等離子體射流氣氛的絕氧作用可減輕摩擦副的氧化磨損,氮冷等離子體氣氛有利于減輕摩擦副的粘著磨損,氮冷等離子體氣氛中NAK80/金剛石摩擦副的摩擦磨損性能最佳。轉速較低時,氮冷等離子體氣氛對NAK80/金剛石摩擦副沒有明顯的減摩作用。轉速較高時,NAK80/金剛石摩擦副在氮冷等離子體氣氛中的摩擦系數(shù)低于空氣氣氛。冷等離子體與固體表面作用時不會破壞工件表面的微觀形貌,且對潤濕性的改性在切削加工后也會逐漸恢復。利用自行研制的振動特性可控的超聲橢圓振動裝置,進行了切削試驗,分析了超聲橢圓振動的切削特性。刀具在超聲振動裝置的驅動下沿橢圓軌跡高頻振動,同時沿進給方向運動,兩種運動模式的復合使得刀具對工件進行周期性的分離式切削。當?shù)毒咭猿暀E圓振動切削時,在刀具耕犁作用形成的條狀結構上會生成"魚鱗"狀振紋,且切削速度越低,"魚淲"狀振紋越密集,并可明顯改善工件表面質量,冷等離子體和超聲橢圓振動共同作用時的工件表面粗糙度最低。超聲橢圓振動切削會增加工件表面的殘余應力,而冷等離子體對切削區(qū)潤滑冷卻有助于降低工件表面的殘余應力。為驗證冷等離子體抑制金剛石切削黑色金屬時的刀具磨損效果,開展了不同氣氛中的切削試驗。普通切削和超聲橢圓振動切削時刀具的磨損表現(xiàn)為切削刃磨損;冷等離子體實時調(diào)控時表現(xiàn)為輕微的前刀面磨損,且金剛石刀具的磨損量顯著下降。冷等離子體和超聲橢圓振動共同作用時,以切削刃輕微的粘附磨損為主,此時抑制金剛石刀具磨損的效果最佳。相比普通金剛石切削黑色金屬加工,冷等離子體輔助超聲橢圓振動切削可將刀具的有效切削距離提高10倍,并且工件的表面粗糙度最低,同時可將金剛石中的碳元素向工件和切屑中的擴散磨損分別降低68.49%和70.37%。
[Abstract]:The lack of effective method to restrain tool wear is a bottleneck to restrict the progress of ultraprecision cutting technology for black metal diamond. The paper proposes that the active particles of the cold plasma jet are more easily combined with the iron atom to form stronger chemical bonds and good cooling effects than the carbon atoms, and apply it to the cutting interface. In real time, the chemical affinity of the tool interface and the thermal effect of the cutting area are reduced, thus cutting tool wear, stabilizing the machining process and improving the machining quality of the diamond cutting black metal. On the basis of the analysis of the mechanism of diamond tool wear and the inhibition of wear and tear, the paper first developed a good cooling and lubrication effect and easy to transfer to the knife. The atmospheric pressure cold plasma jet is controlled by the contact interface, and the mechanism of the cold plasma jet assisted cutting is studied by the theory and test method of molecular dynamics, thermal analysis and friction and wear. Finally, the basic cutting tests are carried out. The main work of this paper is as follows: reducing the chemical interface chemistry from the tool tool interface. Two aspects of affinity and improving the thermal effect of the cutting area are used to suppress the wear of diamond cutting tools. The temperature is low, and it is easily transported to the tool contact interface. It is suitable for the air pressure flexible plasma jet in the auxiliary cutting. It is found that nitrogen is a working gas suitable for producing cold plasma jets from the bare electrode discharge. The effect of the gas discharge on the volt ampere characteristics of nitrogen discharge is less obvious. The effective delivery of the plasma can be achieved by the flexible plasma jet. The length of the flexible jet increases with the increase of the driving voltage and the gas flow, and it has a similar volt ampere with the ordinary cold plasma jet. Characteristics. The pre cooling of the working gas can reduce the temperature of the plasma jet, and the larger the flow rate is, the lower the jet temperature, and the increase of the driving voltage will increase the overall temperature of the plasma jet. Therefore, the plasma jet can be controlled by the flow and discharge voltage by the flow and discharge voltage. In addition, when the driving voltage is 3 kV and the flow rate is 50 L/min, the overall temperature of the flexible nitrogen plasma jet can be lower to -7 C. through molecular dynamics simulation and thermal analysis test, it is concluded that the nitrogen cold plasma can reduce the chemical affinity of the black metal to the diamond. The results of molecular dynamics simulation show that the temperature of the graphitization of the diamond is the result of molecular dynamics simulation. Between 1200 and 1700 C, the temperature of the graphitization of diamond can be reduced to about 773 C under the catalysis of the iron atom. The thermal analysis test shows that the temperature of the diamond graphitization at the NAK80/ diamond contact interface without nitrogen cold plasma is 882, and the sample treated by the nitrogen cold plasma appears at 1185. It is obvious graphitization. That is, the iron atom will reduce the graphitization temperature of the diamond, and the temperature of the diamond graphitization on the black metal / diamond interface after the nitrogen cold plasma treatment will increase. The results show that the NAK80 surface and grain boundary will adsorb a large number of active particles and react with the black metal to produce nitrogen with low chemical affinity of diamond. In order to verify the effect of the cold plasma to improve the thermal effect of the cutting zone, the friction and wear tests of the NAK80/ diamond friction pair were carried out in the air jet, nitrogen jet and nitrogen cold plasma jet atmosphere. The results showed that the nitrogen and nitrogen cold plasma jet atmosphere had been tested. The oxidation wear of the friction pair can be reduced by the anoxic action. The nitrogen cold plasma atmosphere helps to reduce the adhesion and wear of the friction pair. The friction and wear properties of the NAK80/ diamond friction pair in the nitrogen cold plasma atmosphere are the best. The nitrogen cold plasma atmosphere has no obvious antifriction effect on the NAK80/ diamond friction pair. The rotational speed is higher. The friction coefficient of the NAK80/ diamond friction pair in the atmosphere of nitrogen cold plasma is lower than that in the air. The effect of cold plasma on the surface of the solid will not destroy the microstructure of the workpiece surface, and the modification of wettability will be gradually restored after cutting. The cutting test is carried out. The cutting characteristics of ultrasonic elliptical vibration are analyzed. The cutting tool vibrate along the elliptical track under the drive of the ultrasonic vibration device and moves along the direction of the feed. The two kinds of motion modes make the tool make periodic separation cutting to the workpiece. When the tool is cutting with ultrasonic elliptical vibration, the tool plow is used. The "fish scale" pattern will be formed in the strip structure formed by the action, and the lower the cutting speed, the more dense the "fish" shape is, and the surface quality of the workpiece can be improved obviously. The surface roughness of the workpiece is the lowest when the cold plasma and ultrasonic elliptical vibration act together. The ultrasonic elliptical vibration cutting will increase the residual stress on the workpiece surface, and the cold is away from the cold. The lubricating cooling of the sub body helps to reduce the residual stress on the surface of the workpiece. In order to verify the tool wear effect of cutting the black metal by the cold plasma, the cutting experiments in different atmospheres have been carried out. The wear of the cutting tool in the ordinary cutting and ultrasonic elliptical vibration cutting is the wear of the cutting edge; the cold plasma is real-time in real time. The wear of the diamond cutting tool is slightly worn and the wear amount of the diamond cutting tool drops significantly. When the cold plasma and ultrasonic elliptical vibration are combined, it is the best to reduce the wear of the diamond cutting tool. The acoustic elliptical vibration cutting can increase the effective cutting distance of the tool by 10 times, and the surface roughness of the workpiece is the lowest. At the same time, the carbon element in the diamond can be reduced by 68.49% and 70.37%. to the workpiece and the chip respectively.
【學位授予單位】：大連理工大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TG506

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