气中电火花线切割加工有限元仿真和实验研究

发布时间：2018-07-09 23:51

本文选题：气中电火花线切割 + 有限元仿真分析　；参考：《哈尔滨理工大学》2017年硕士论文

【摘要】：Cr12MoV模具钢经过淬火处理后具有良好的耐磨性和抗腐蚀性,同时具有较高的硬度,利用传统方法很难进行加工,并且对刀具损伤较大。为了减小刀具损伤以及获得较好工件表面质量,通常采用气中电火花线切割工艺对Cr12MoV模具钢进行加工。因为该工艺与液中电火花线切割加工技术相比,不易产生有害气体和难分解的物质,并且具有较好成型特性。但由于受到现有实验条件的限制,气中电火花线切割加工技术还处于理论与实验研究阶段。通过气中电火花线切割加工机理的研究,本文建立了气中移动单脉冲火花放电传热模型,确定了温度场与应力场的初始与边界条件,并对传热模型的热传导方程、弹性塑性本构方程以及热应力与应变关系进行了求解。在有限元理论基础上,利用ABAQUS有限元软件,建立了气中移动单脉冲火花放电有限元仿真模型,并对其进行了仿真分析,揭示了气中移动单脉冲火花放电过程中Cr12MoV模具钢表面传热过程演化规律以及温度场、应力与应变场分布及变化规律。并对热源不同状态下的电蚀坑形貌进行分析,获得了动态下的单个电蚀坑几何模型为半双椭球形。根据实际加工情况,建立并修正了单个电蚀坑几何模型,并对其进行了体积计算,进而探讨了峰值电流、脉冲宽度等电参数对气中电火花线切割工件表面电蚀坑几何形貌的影响。在理论研究与仿真分析的基础上,制定了多次气中电火花线切割加工试验方案,并对Cr12MoV模具钢进行了电火花线切割加工试验,对气液电火花线切割工件表面形貌进行了分析。通过单因素法获得峰值电流、脉冲宽度、偏移量以及工作台进给速度等工艺参数下材料蚀除率与工件表面质量的变化规律。将仿真数据与实际数据进行对比,所得误差在允许范围内,从而验证所建模型的合理性。进而说明通过对该模型进行有限元仿真分析,来探讨工件表面电蚀坑几何形貌及其影响因素是有效的。这对预测电火花线切割加工速率和工件表面质量具有重要的意义。
[Abstract]:Cr12MoV die steel has good wear resistance, corrosion resistance and high hardness after quenching, so it is difficult to process by traditional method and has great damage to cutting tools. In order to reduce tool damage and obtain better surface quality of workpiece, gas WEDM is usually used to process Cr12MoV die steel. Compared with WEDM, it is difficult to produce harmful gas and difficult to decompose, and it has better forming characteristics. However, due to the limitation of the existing experimental conditions, the WEDM technology in gas is still in the stage of theoretical and experimental research. By studying the mechanism of WEDM in gas, the heat transfer model of moving single pulse spark discharge in gas is established, the initial and boundary conditions of temperature field and stress field are determined, and the heat conduction equation of heat transfer model is given. The elastoplastic constitutive equation and the relationship between thermal stress and strain are solved. On the basis of finite element theory, the finite element simulation model of moving single pulse spark discharge in gas is established by using Abaqus finite element software, and the simulation analysis is carried out. The evolution law of heat transfer on the surface of Cr12MoV die steel during moving single pulse spark discharge in gas and the distribution and variation of temperature field, stress and strain field are revealed. The morphologies of the etched pits in different states of the heat source were analyzed and the geometric model of the single etched pit was obtained as a semi-double ellipsoid. According to the actual machining conditions, the geometric model of a single electroetching pit is established and modified, and the volume of the model is calculated, and the peak current is discussed. The effect of pulse width and electrical parameters on the geometry of electroetching pits on the surface of WEDM workpiece in gas. On the basis of theoretical research and simulation analysis, the test scheme of WEDM in gas has been established, and the WEDM test of Cr12MoV die steel has been carried out, and the surface morphology of the workpiece of WEDM with gas-liquid EDM has been analyzed. The changes of material erosion rate and workpiece surface quality are obtained by single factor method under the process parameters such as peak current pulse width offset and feed speed of worktable. By comparing the simulation data with the actual data, the error is within the allowable range, which verifies the rationality of the model. It is proved that it is effective to study the geometric morphology of the surface of the workpiece and its influencing factors by the finite element simulation analysis of the model. It is of great significance to predict the WEDM rate and the surface quality of the workpiece.
【学位授予单位】：哈尔滨理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG484

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