Model of a chip formation mechanism of cortical bone using a tool with a negative rake angle — analysis, modelling, and validation

Machining of bone tissue is a significant procedure in many surgical interventions. Due to the limited research on this topic, understanding the processes occurring during bone processing is crucial for designing tools that optimize the surgical process. This paper presents a model of machining cortical bone with a negative rake angle tool based on three cutting modes. The model was prepared based on experimental data from the orthogonal cutting of cortical bone tissue, numerical simulations, and theoretical models considering the presence of the stagnation zone. Special attention was given to the influence of bone anisotropy on chip formation, chip morphology, and the type and propagation of cracks depending on the orientation of osteons relative to the cutting edge. The analysis of crack morphology and chip structure revealed the mechanisms involved in the material’s destruction, which were incorporated into the prepared model. The experimental results confirm the consistency with the proposed model. Based on the prepared cutting model, it is possible to determine the threshold depths of cutting that allow for controlled processing of bone surfaces, predicting the milling machine and the type of formed chips. The model developed based on experimental data is the first for cortical bone tissue. This analysis holds significant theoretical and practical importance for developing innovative orthopedic tools and surgical methods.