电火花加工蚀除物和气泡在间隙中分布状态仿真研究

发布时间：2019-05-29 23:40

【摘要】：在电火花加工过程中,蚀除物及气泡在加工间隙中的运动及分布情况对电火花加工的加工效率、电极损耗以及表面质量等具有非常重要的影响。若加工间隙内的蚀除物不能及时有效地排出,间隙内蚀除物和气泡浓度增加,容易产生二次放电、拉弧、短路、放电集中等现象,不仅会增大电极损耗,影响成形精度,降低加工速度,严重时还会使加工无法继续进行。因此在电火花加工过程中应该采取有效的措施来促进蚀除物排出极间间隙内流场,抬刀运动作为一种有效的方式得到了广泛地应用。首先,本文基于电火花加工的机理,探索蚀除物和气泡的产生和运动规律,建立电火花加工过程中间隙流场的三维的固-液-气三相流模型。通过实验对放电参数进行选择,据此对放电间隙进行估算,建立加工间隙流场的几何模型;在对脉冲放电产生气泡进行实验观测的基础上,建立了脉冲放电气泡的产生和运动模型;通过对电火花加工的加工速度的测量对脉冲放电产生的蚀除产物大小进行计算并建立蚀除物的产生模型;确定了电火花单脉冲放电过程的仿真模型。其次,本文在建立单脉冲放电仿真模型基础上,根据脉冲频率建立无抬刀连续放电过程仿真模型,分析无抬刀连续放电过程蚀除物和气泡在间隙中的分布状态,探究电火花连续放电过程中容易产生尖角损耗的原因。在无抬刀连续放电过程仿真模型基础上,建立有抬刀连续放电过程仿真模型,研究抬刀运动对电极损耗和加工速度的影响。最后,进行不同抬刀高度、抬刀频率、抬刀速度、加工深度和电极直径的加工实验,通过实验和仿真结果对比,验证单脉冲放电仿真模型、无抬刀连续放电过程仿真模型和抬刀连续放电过程仿真模型。
[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.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG661

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