钻削CFRP的双顶角钻头磨损及抑制新方法

Wear of One-shot Drill Bit in Drilling CFRP and Novel Method for Tool Wear Reduction

为满足高性能碳纤维增强复合材料(CFRP)结构件的高质量制孔需求,现阶段广泛采用双顶角钻头钻削CFRP,但因其“钻、扩、铰”一体的结构形式,双顶角钻头第二主切削刃的磨损程度和状态是决定钻削孔壁质量的关键因素.此外,由于CFRP中碳纤维磨蚀性强,制孔中钻头快速磨损,切削刃严重钝化,极易导致孔壁损伤.通过引入切削刃钝圆半径,揭示双顶角钻头第二主切削刃钝化后,在严重的后刀面磨损作用下,第二主切削刃刃口钝圆半径又减小的磨损机制,在此基础上,结合不同纤维切削角下CFRP成屑机制,详细探究了双顶角钻头第二主切削刃钝化状态对钻削孔壁损伤的影响规律;最后创新性地在钻头第二主切削刃末端开设内冷孔,利用微量冷却润滑(MQL)工艺,实现了钻头第二主切削刃钝化磨损的有效抑制,显著提升了高性能碳纤维增强复合材料的制孔质量,为高质量复合材料制孔工艺和工具研究奠定了重要基础.

In order to satisfy high quality requirements of drilled holes on high strength carbon fiber reinforced plastics(CFRP) structural parts, one-shot drill bit is currently utilized in drilling CFRP. However, due to the special step-drilling(including pre-drilling, chambering and reaming) geometry of the one-shot drill bit, the wear status of secondary cutting edges determines the final hole surface quality. Also on account of high abrasiveness of carbon fibers, the drill bit suffers quick tool wear and the cutting edges usually encounter edge dulling, which leads to subsequent serious hole surface defects. By applying cutting edge rounding to characterize the dullness of the cutting edge, the results show the secondary cutting edge is prone to dulling at initial drilling stage, and then it is reground and re-sharpened. On the basis of tool wear analysis, the paper investigates the impacts of edge dulling on drilled hole surface defects under different fiber cutting angles. Finally by creatively designing internal coolant holes at specific position on the secondary cutting edge and applying minimum quantity lubrication(MQL), the dulling wear of secondary cutting edge is effectively reduced and hole surface quality is greatly improved. The study paves the way for the research on tools and processes of drilling CFRP with high quality.