On modelling of cutting force and temperature in bone milling

Cutting force and temperature are the key factors to be controlled during the orthopaedic surgery which could result in mechanical damage and necrosis of the bone tissue. Mechanistic modelling of the bone cutting process is expected to be an efficient method to understand and control these process challenges. However, due to the special structure and properties of the bone tissue (consist of osteon fibres and interstitial lamellae matrix), the conventional metal cutting models are not applicable in bone cutting process. This paper presents a novel cutting force and temperature mechanistic models for milling of bone. A cutting stress model of bone material was developed which takes into account its anisotropic characteristics based on the orthogonal cutting data. The cutting force coefficients are predicted incorporating the osteon orientation, tool geometry and edge effect with unified mechanics of cutting approach. Furthermore, a model of the induced cutting temperature based on heat flux developed during the process was proposed to predict the temperature distribution on bone cut surface. The experimental results showed a better consistency with the proposed model compared with the conventional Johnson-Cook model under different cutting conditions. A necrosis (potential cell injury from thermal effect) penetration depth was also proposed to evaluate the extent of thermal damage of bone tissue by the developed models. The proposed model can be used to assist the robotic surgery, to optimize the cutting parameters as well as to guide the orthopaedic tool design.