Unconventional Applications of Electrical Discharge Machining

电火花加工（EDM）是一种精密的材料去除工艺，它利用在介电流体存在的情况下，在工具和工件电极之间产生的受控快速电火花放电产生的热量。传统上，电火花加工的应用领域涉及难切削材料的加工，因为材料去除的热机制不受工件材料的硬度和韧性的限制，与需要塑性变形的切削加工相反。电火花加工已进一步应用于具有尖角的内腔等几何特征的加工。由于刀具和工件之间没有物理接触，相关的力相对可以忽略不计，因此该工艺也用于加工薄/易碎的工件。由于电火花加工中的材料去除需要在微观尺度上进行局部熔化和汽化，因此生成的表面包含大量微观的重叠凹坑。因此，电火花加工是极少数能够产生正偏度表面的制造工艺之一。这意味着该表面由散布在相对较宽的山谷中的峰组成，使得高度分布向右倾斜，这使得该表面理想地倾向于将在拟议的研究中研究的新应用。EDM还提供了定制特征凹坑的尺寸和纵横比的灵活性，这些凹坑共同构成了面向特定应用的纹理。这提供了一个令人兴奋的前景，即使是相互冲突的功能需求，如减少或增加摩擦，在相同的过程中，通过适当地调整脉冲参数。在上述背景下，提出的研究目标主要是探索创新的、非常规的电火花加工应用，其中材料去除本身不是主要目的，而是实现表面形貌工程的一种手段，以实现特定的功能属性。特别是，拟议的工作将涉及以下方面的科学调查：(1)电火花加工织构在为气泡提供成核位置以增强沸腾传热方面的作用，应用于发电和电子工业；(2)汽车活塞环的织构，以增强润滑剂的进入和保留，以减少摩擦，提高发动机性能和燃油效率；(3)在金属生物医学植入物上赋予适当的织构，以促进其融入骨骼结构。(4)使用电火花加工制造防水、自清洁表面，应用于航空航天、船舶和汽车工业。该研究将进一步研究电火花加工在加工工具表面的应用，以增强基材与涂层之间的附着力，探索电火花加工纹理对移动流体阻力的影响，并研究电火花加工纹理可以增加表面牵引力的机制。

Electrical discharge machining (EDM) is a precision material removal process that utilizes the heat generated from controlled, rapid electrical spark discharges struck between the tool and workpiece electrodes, in the presence of a dielectric fluid. Traditionally, the application domain of EDM has referred to the machining of difficult-to-cut materials, as the thermal mechanism of material removal is not limited by the hardness and toughness of the workpiece material, in contrast to cutting processes that entail plastic deformation. EDM has further been applied in the machining of geometric features such as internal cavities with sharp corners. The process is also used to machine thin/fragile workpieces, on account of the associated forces being relatively negligible due to there being no physical contact between the tool and the workpiece. As material removal in EDM entails localized melting and vaporization at the micro-scale, the generated surface comprises a large number of microscopic, overlapping craters. Accordingly, EDM is one of the very few manufacturing processes with the capability to generate surfaces with a positive skewness. This means that the surface comprises peaks interspersed among relatively wide valleys such that the height distribution is skewed to the right, which makes the surface ideally predisposed towards the novel applications that will be investigated in the proposed research. EDM further offers the flexibility to tailor the size and aspect ratio of the characteristic craters that collectively constitute the texture towards a specific application. This offers the exciting prospect of achieving even conflicting functional requirements, such as a reduction or enhancement of friction, in the same process by appropriately tuning the pulse parameters. In the context above, the objective of the proposed research is primarily to explore innovative, unconventional applications of EDM wherein material removal is not the primary intent per se, but rather a means to the end of engineering the topography of a surface towards realizing a specific functional attribute. In particular, the proposed work will refer to scientific investigations into: (1) the role of an EDM texture in providing nucleation sites for bubbles towards enhancing boiling heat transfer, with applications in the power generation and electronics industries, (2) texturing of automotive piston rings so as to enhance lubricant ingress and retention for reducing friction towards enhanced engine performance and fuel efficiency, (3) imparting an appropriate texture on metallic biomedical implants with a view to facilitating their integration into the bone structure, and (4) the use of EDM for the fabrication of water-repellent, self-cleaning surfaces with applications in the aerospace, marine and automotive industries. The research will further examine the application of EDM in texturing tooling surfaces in order to enhance adhesion between the substrate and a coating, explore the effect of an EDM texture on the drag against a moving fluid, and investigate the mechanism by which an EDM texture could be engineered to increase surface traction.