【作者】 刘雪峰；

【导师】 白基成；

【作者基本信息】 哈尔滨工业大学 ， 机械工程（专业学位）， 2021， 硕士

【摘要】 随着多场辅助电火花加工技术的发展,超声辅助电火花加工在微小孔加工领域得到了广泛的应用。其具体方法是对电极施加超声运动使得电极对孔内工作液产生高频搅动效果以提高孔内工作液流速。与传统电极做旋转运动相比,超声辅助电火花微小孔加工具有加工效率快、表面质量高、电极损耗小等优点,但是随着加工的进行,不断累积的电极损耗仍然会导致微小孔的尺寸和形状精度下降。因此,定量分析超声辅助电火花微小孔加工的电极损耗规律,建立电极损耗预测模型,无论是对保证单个微小孔的加工质量,还是对保证微细群孔的孔径一致性,都具有十分重要的意义。为此,本文进行的主要研究及工作如下:为了从流速角度验证电极做超声平动运动的优势,建立了无冲液条件下的电火花微小孔加工过程间隙流场仿真模型,分析总结了电极做超声平动运动和常用的旋转运动时孔内间隙流场分布情况和差异,探究了超声振动频率、超声振动幅值、电极转速和加工深度对工作液流速的影响规律;为了能够模拟更真实的工况,建立了施加外部冲液的仿真模型,得出了冲液流速对介质流体流速的影响规律。为了得到较为合适的加工参数设定范围,本文开展了TR脉冲电源模式下的超声辅助电火花微小孔加工单因素实验研究,研究了TR脉冲电源参数和超声振动参数对电极损耗、加工时间、放电间隙和孔口毛边的影响规律,发现合理的参数设置可以获得更好的加工性能。同时开展了正交实验,针对四种不同的加工指标,分别得到了实验参数变化对四种加工指标影响的显著程度。为了探究加工参数对电极损耗的影响,本文开展了超声辅助电火花微小孔加工电极损耗实验,得出了电极直径和工件厚度变化对电极损耗及电极损耗区尺寸的影响规律;为了从电极损耗的角度验证电极做超声平动运动的优势,进行了电极做旋转运动的对比实验,结果表明特别是微小孔深径比较大时,电极做超声平动运动比旋转运动在电极损耗方面有明显改善;为了预测电极损耗并对其进行补偿,根据电极损耗实验收集的数据,建立了基于电极直径、工件厚度和加工孔数的超声辅助电火花微小孔加工电极损耗预测神经网络模型,并且使用此模型得出的数据进行了验证实验。经过测量,加工的微小孔出口直径一致性得到了提高。更多还原

【Abstract】 With the development of multi-field assisted EDM technology,ultrasonic assisted EDM has been widely used in the field of micro-hole machining.The specific method is to apply ultrasonic motion to the electrode to make the electrode produce high frequency agitation effect on the working liquid in the hole to improve the flow rate of the working liquid in the hole.Compared with the traditional electrode rotating motion,the ultrasonic assisted EDM micro-hole machining has the advantages of fast processing efficiency,high surface quality and small electrode wear,but with the progress of processing,the continuous accumulation of electrode wear will still lead to the decline of the size and shape accuracy of the micro-hole.Therefore,it is of great significance to quantitatively analyze the rule of electrode wear in ultrasonic assisted EDM micro-hole machining and establish a prediction model for electrode wear,not only to ensure the machining quality of single micro-hole,but also to ensure the uniformity of pore size of micro-hole group.Therefore,the main research and work of this paper are as follows:In order to verify the advantages of ultrasonic translational movement of electrode from the perspective of flow velocity,a simulation model of gap flow field in EDM micro-hole machining process without flapping was established,and the distribution and difference of gap flow field in the process of ultrasonic translational movement of electrode and common rotary movement were analyzed and summarized.The effects of ultrasonic vibration frequency,ultrasonic vibration amplitude,electrode speed and machining depth on the flow rate of working liquid were investigated.In order to simulate more real working conditions,a simulation model of external flushing was established,and the influence law of flushing velocity on medium fluid velocity was obtained.Range in order to obtain a suitable processing parameter setting,this paper has carried out the TR pulse power supply mode of ultrasonic assisted edm small hole machining single factor experiment,studies the TR pulse power and ultrasonic vibration parameters on electrode wear,the processing time,discharge gap and the influence law of orifice burrs,found a reasonable parameter Settings can gain better processing performance.At the same time,orthogonal experiments were carried out,aiming at four different processing indexes,and the significant degree of influence of experimental parameters on the four processing indexes were obtained respectively.In order to explore the influence of machining parameters on electrode wear,an experiment of ultrasonic assisted EDM micro-hole machining electrode wear was carried out in this paper.The influence rules of electrode diameter and workpiece thickness on electrode wear and size of electrode wear area were obtained.In order to verify the advantages of ultrasonic translational movement of the electrode from the perspective of electrode wear,a comparative experiment was carried out on the rotating movement of the electrode.The results show that the ultrasonic translational movement of the electrode improves the electrode wear obviously compared with the rotating movement,especially when the depth of the tiny hole is relatively large.In order to predict and compensate the electrode wear,a neural network model for predicting the electrode wear in micro-hole EDM machining was established based on the electrode diameter,workpiece thickness and number of machining holes,and a verification experiment was carried out using the data obtained from the model.Through measurement,the consistency of the outlet diameter of the micro-hole is improved.更多还原