【摘要】：在電火花加工過(guò)程中,蝕除物及氣泡在加工間隙中的運(yùn)動(dòng)及分布情況對(duì)電火花加工的加工效率、電極損耗以及表面質(zhì)量等具有非常重要的影響。若加工間隙內(nèi)的蝕除物不能及時(shí)有效地排出,間隙內(nèi)蝕除物和氣泡濃度增加,容易產(chǎn)生二次放電、拉弧、短路、放電集中等現(xiàn)象,不僅會(huì)增大電極損耗,影響成形精度,降低加工速度,嚴(yán)重時(shí)還會(huì)使加工無(wú)法繼續(xù)進(jìn)行。因此在電火花加工過(guò)程中應(yīng)該采取有效的措施來(lái)促進(jìn)蝕除物排出極間間隙內(nèi)流場(chǎng),抬刀運(yùn)動(dòng)作為一種有效的方式得到了廣泛地應(yīng)用。首先,本文基于電火花加工的機(jī)理,探索蝕除物和氣泡的產(chǎn)生和運(yùn)動(dòng)規(guī)律,建立電火花加工過(guò)程中間隙流場(chǎng)的三維的固-液-氣三相流模型。通過(guò)實(shí)驗(yàn)對(duì)放電參數(shù)進(jìn)行選擇,據(jù)此對(duì)放電間隙進(jìn)行估算,建立加工間隙流場(chǎng)的幾何模型;在對(duì)脈沖放電產(chǎn)生氣泡進(jìn)行實(shí)驗(yàn)觀測(cè)的基礎(chǔ)上,建立了脈沖放電氣泡的產(chǎn)生和運(yùn)動(dòng)模型;通過(guò)對(duì)電火花加工的加工速度的測(cè)量對(duì)脈沖放電產(chǎn)生的蝕除產(chǎn)物大小進(jìn)行計(jì)算并建立蝕除物的產(chǎn)生模型;確定了電火花單脈沖放電過(guò)程的仿真模型。其次,本文在建立單脈沖放電仿真模型基礎(chǔ)上,根據(jù)脈沖頻率建立無(wú)抬刀連續(xù)放電過(guò)程仿真模型,分析無(wú)抬刀連續(xù)放電過(guò)程蝕除物和氣泡在間隙中的分布狀態(tài),探究電火花連續(xù)放電過(guò)程中容易產(chǎn)生尖角損耗的原因。在無(wú)抬刀連續(xù)放電過(guò)程仿真模型基礎(chǔ)上,建立有抬刀連續(xù)放電過(guò)程仿真模型,研究抬刀運(yùn)動(dòng)對(duì)電極損耗和加工速度的影響。最后,進(jìn)行不同抬刀高度、抬刀頻率、抬刀速度、加工深度和電極直徑的加工實(shí)驗(yàn),通過(guò)實(shí)驗(yàn)和仿真結(jié)果對(duì)比,驗(yàn)證單脈沖放電仿真模型、無(wú)抬刀連續(xù)放電過(guò)程仿真模型和抬刀連續(xù)放電過(guò)程仿真模型。
[Abstract]:In the process of EDM, the movement and distribution of etches and bubbles in the machining gap have a very important influence on the machining efficiency, electrode loss and surface quality of EDM. If the etch in the machining gap can not be discharged in time and effectively, and the concentration of etch and bubble in the gap increases, it is easy to produce secondary discharge, arc drawing, short circuit, discharge concentration and so on, which will not only increase the electrode loss and affect the forming accuracy. Reduce the processing speed, serious will also make the processing can not continue. Therefore, effective measures should be taken to promote the flow field in the gap between electrodes in the process of EDM, and the movement of knife lifting has been widely used as an effective way. Firstly, based on the mechanism of EDM, the generation and movement of etches and bubbles are explored, and a three-dimensional solid-liquid-gas three-phase flow model of gap flow field in EDM is established. The discharge parameters are selected by experiments, and the discharge gap is estimated, and the geometric model of machining gap flow field is established. Based on the experimental observation of bubbles produced by pulse discharge, the model of bubble generation and motion in pulse discharge is established. By measuring the machining speed of EDM, the size of etched products produced by pulse discharge is calculated and the generation model of etched products is established, and the simulation model of EDM monopulse discharge process is determined. Secondly, on the basis of establishing the single pulse discharge simulation model, the simulation model of the continuous discharge process without lifting knife is established according to the pulse frequency, and the distribution state of the etch and bubble in the gap of the continuous discharge process without lifting knife is analyzed. To explore the reasons why sharp angle loss is easy to occur in the process of continuous discharge of EDM. On the basis of the simulation model of continuous discharge process without lifting knife, the simulation model of continuous discharge process with knife lifting is established, and the influence of knife lifting movement on electrode loss and machining speed is studied. Finally, the machining experiments of different lifting height, lifting frequency, lifting speed, machining depth and electrode diameter are carried out, and the monopulse discharge simulation model is verified by comparing the experimental and simulation results. The simulation model of continuous discharge process without lifting knife and the simulation model of continuous discharge process without lifting knife.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TG661

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