大面积钛合金电火花加工放电产物运动规律研究  

Study on the Movement Rule of Discharge Products in Large Area Titanium Alloy Machining by Electrical Discharge Machining

作　　者：李东[1] 刘志刚[1] 王伊卿[1] 洪军[1] 卢秉恒[1] 

机构地区：[1]西安交通大学机械制造系统工程国家重点实验室,西安710049

出　　处：《机械工程学报》2017年第21期200-208,共9页Journal of Mechanical Engineering

基　　金：陕西省工业攻关资助项目(2014K06-03)

摘　　要：在大面积钛合金电火花加工过程中,容易造成电蚀产物聚集且不易冷却从而产生集中放电、拉弧及短路现象,严重的甚至会烧伤工件的表面。因此,为了实现持续稳定的正常火花放电,在放电过程中放电点的位置分布必须均匀。电火花放电产生的气泡及加工屑是影响放电点分布均匀性的关键因素。为此,首先通过计算流体动力学软件Fluent对气泡的运动规律进行了仿真分析,然后通过高速摄像机拍摄透明电极下气泡的运动规律验证仿真的可靠性。结果表明气泡在间隙内的运动经过了膨胀、收缩及破裂的过程。通过试验对脉冲放电产生的加工屑颗粒的直径分布及数量进行了研究,并对加工屑在放电瞬间的抛撒机理做出了合理的假设,建立了电火花加工过程中放电间隙流场的气液固混合相三维模型,仿真分析了气泡运动对加工屑运动的影响规律。研究发现加工屑在气泡内部时,由于空气对加工屑的阻力小于工作液对气泡膨胀的阻力,加工屑快速向气泡的边界靠近。而当加工屑穿透气泡的边界进入工作液中后其速度迅速降低,且随着气泡的收缩逐渐靠近放电发生的位置。因此可以通过改变脉冲间隔实现控制气泡的大小及加工屑的分布,从而可以有效避免集中放电提高放电点分布的均匀性。In a large area titanium alloy machining by electrical discharge machining, the discharge products are easily to gather together and not easily cooling. It will generate concentrated discharge, arc discharge, short circuit phenomenon, and even burn the surface of the work piece. In order to achieve sustained and stable normal spark discharge, the location of the discharge point in the process must be evenly distributed. Bubble and debris produced by the discharge is a key factor influencing the distribution uniformity of discharge point. Therefore, the law of bubble motion is analyzed by computational fluid dynamics software Fluent, and then its reliability is verified by observing the EDM gap phenomena through a transparent electrode from the direction normal to the machining surface using a high-speed video camera. The result shows that the bubble motion in the gap goes through the process of expansion, contraction and rupture. The diameter distribution and quantity of processed debris generated by the pulse discharge are studied through experiments, and a reasonable assumption about the scatters mechanism of debris particles in the discharge moment is made. The three-dimensional model of gas-liquid-solid mixed phase in the inter-electrode gap flow field is established, and then the influence of the bubble on the debris movement is analyzed by simulation. The study finds that the bubble in the initial stages promotes the motion of the debris and the debris gradually are far from the discharge location while the bubble expanding. Velocity of the debris fall rapidly after through the boundary of the bubble into the working liquid, and the debris gradually are close to the discharge location while the bubble contracting. Therefore, the size of the bubble and the distribution of debris particles could be controlled by changing the processing parameters, which can effectively avoid the concentration of discharge and finally improve the uniformity of the discharge.

关 键 词：钛合金 电火花加工 高速摄像机 放电产物 放电点分布均匀性 

分 类 号：V261[航空宇航科学与技术—航空宇航制造工程]