As an important advanced machining process, in Wire Electrical Discharge Machining (WEDM) certain fundamental issues remain need to be studied in-depth, such as the effect of part surface roughness on heat transfer mechanisms. In the WEDM process, roughing cut wire goes into the workpiece to do the first shaping and in trim cut the wire sweeps on the outer surface to improve the surface roughness. In both of these two cases, the generation of sparks depends on the passing surface roughness. Therefore, with AISI D2 material and brass wire, this paper presents a study of the influence of part surface roughness on heat partition and the radius of the plasma channel in the WEDM process. Through extensive single discharge experiments, it is shown that the removal capacity per discharge can increase if the discharge occurs on a smoother surface. A Finite Element thermal model was then used for inverse fitting of the values of heat partition and radius of the plasma channel. These parameters completely define the characteristics of the heat conduction problem. The results indicate a strong correlation between an increase in heat partition ratio and a decrease in part surface roughness. The values of plasma channel radius show an increase in this value when discharging on rougher surfaces. It means that with the increasing of plasma channel radius, the heat source goes into the workpiece more dispersed. In the case of rougher surface, although the there is more area that affected by the heat source, finally the temperature of most area cannot reach to the melting point and it causes the smaller crater radius and volume, while the metal removal rate decreases. These results contribute towards a more complete understanding of the influence of surface roughness to the spark occurring.

中文翻译：

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电火花线切割工艺中AISI D2工件粗糙度对热分配和等离子通道半径的影响

作为一种重要的先进加工工艺，在电火花线切割加工（WEDM）中，仍然需要深入研究某些基本问题，例如零件表面粗糙度对传热机理的影响。在WEDM工艺中，粗加工的切割丝进入工件以进行第一次成型，并在修整时切割外表面上的丝条，以改善表面粗糙度。在这两种情况下，火花的产生都取决于通过的表面粗糙度。因此，本文采用AISI D2材料和黄铜线，研究了电火花加工过程中零件表面粗糙度对热分配和等离子通道半径的影响。通过大量的单次放电实验表明，如果放电发生在较光滑的表面上，则每次放电的去除能力会提高。然后使用有限元热模型对热量分配值和等离子通道半径进行反拟合。这些参数完全定义了导热问题的特征。结果表明，热分配比的增加与零件表面粗糙度的减少之间有很强的相关性。当在较粗糙的表面上放电时，等离子通道半径的值显示该值增加。这意味着随着等离子通道半径的增加，热源进入工件时会更加分散。在表面较粗糙的情况下，尽管存在更多受热源影响的区域，但最终大多数区域的温度无法达到熔点，从而导致较小的弹坑半径和体积，同时金属去除率降低。