Rotary ultrasonic machining (RUM) is an effective approach to process carbon fiber reinforced polymer (CFRP) composites. However, the surface formation mechanisms in RUM for different fiber orientations have not been comprehensively investigated. In this research, ultrasonic vibration-assisted scratching (UVAS) and conventional scratching (CS) tests with invariant cutting depth were conducted innovatively to expose the material removal mechanism. Based on the kinematics analysis, the characteristics of material removal process have been compared between UVAS and CS, and dynamic changes of actual cutting angle with the addition of ultrasonic vibration have been studied for the first time. The groove morphologies and scratching loads were analyzed for different fiber orientations and scratching parameters. The experimental results revealed that the fracture mode of fiber was principally decided by cutting angle. And the surface crack propagation can be significantly inhibited in UVAS due to the intermittent cutting behavior, increase of instantaneous velocity and the dynamic alteration of direction and magnitude of actual cutting angles. This research will help enable an in-depth understanding of the material removal mechanism of CFRP composites in RUM, and is beneficial for the optimum utilization of vibration assisted processing for advanced composites.

旋转超声加工 (RUM) 是加工碳纤维增强聚合物 (CFRP) 复合材料的有效方法。然而，尚未全面研究 RUM 中不同纤维取向的表面形成机制。在这项研究中，创新地进行了超声振动辅助划痕（UVAS）和具有不变切削深度的常规划痕（CS）测试，以揭示材料去除机制。在运动学分析的基础上，比较了UVAS和CS的材料去除过程特性，首次研究了实际切削角在超声振动作用下的动态变化。针对不同的纤维取向和划痕参数分析凹槽形态和划痕载荷。实验结果表明，纤维的断裂方式主要由切割角度决定。由于断续切削行为、瞬时速度的增加以及实际切削角度的方向和大小的动态变化，UVAS中的表面裂纹扩展可以得到显着抑制。该研究将有助于深入了解 CFRP 复合材料在 RUM 中的材料去除机制，并有利于振动辅助加工在先进复合材料中的最佳利用。