Modeling and Experimental Validation of Forces in Low-Frequency Vibration-Assisted Drilling Considering Bone Anisotropic Effects

This study focuses on modeling and experimental validation of drilling forces in low-frequency vibration-assisted bone drilling (LVAD), with explicit consideration of bone anisotropic effects. A mechanistic force model is established by integrating contributions from the main cutting edges and chisel edge, and a direction-dependent anisotropic coefficient is introduced to characterize the anisotropic shear strength of cortical bone. The influences of feed rate, spindle speed, drill diameter, vibration amplitude, frequency, and drilling orientation on drilling forces are analyzed theoretically and experimentally. Results show that drilling forces increase with feed rate and drill diameter and decrease with spindle speed and vibration amplitude. LVAD reduces drilling forces by up to 16.52% compared with conventional drilling. Perpendicular drilling produces lower forces than oblique drilling, and forces in the yz-plane are higher than those in the xz-plane due to bone anisotropy. The proposed model is well verified by experiments, providing a theoretical basis for parameter optimization in clinical bone drilling.