Surface morphology generation mechanism of cortical bone longitudinal-torsional ultrasonic vibration assisted micro-milling

Bone ultrasonic vibration micro-milling has an advantage of low cutting damage, and it potentially applied in minimally invasive medical surgery. However, cortical bone is a quasi-brittle biological material, and its cutting surface morphology generation mechanism are complex. Hence, this paper reveals the surface morphology generation mechanism of bone micro longitudinal-torsional ultrasonic assisted milling (LTUAM). The surface morphology generation of different cutting parameters in LTUAM was simulated. The bone ultrasonic vibration micro-milling experiments were carried out considering the bone transverse, across and parallel cutting directions. The surface morphology generation mechanism of cortical bone tissue in LTUAM was discussed. The experimental results indicated the crack propagation is strongly influenced by the micro-milling direction. The crack tends to propagate in parallel milling direction due to cement line cracking. The surface of bone in LTUAM has less damage and more smoother surface morphology. The bone LTUAM method effectively suppresses brittle fracture cutting, and reduces surface damage defects. This research provides efficient minimally invasive cutting methods and technical support for minimally invasive interventional surgical medical equipment.