MACHINING OF CORTICAL BONE: SIMULATIONS OF CHIP FORMATION MECHANICS USING METAL MACHINING MODELS

Abstract

This paper investigates chip formation in the machining of cortical bone and the application of isotropic elastic-plastic material models with a pressure dependent yield stress and a strain path dependent failure strain law to finite element calculations to predict observed behaviour. It is shown that a range of models can be created that result in segmented chip formations and a range of specific cutting forces similar to those observed experimentally. Results from the simulations provide an explanation for differences in the ratio of thrust to cutting forces observed between previous experimental studies, namely that the cutting tools used may have had different edge sharpness or degree of damage induced by the material removal process. Measurements of edge profiles from one of these studies support that explanation and emphasize the importance of tool toughness in maintaining efficient cutting of bone.

Keywords:

• bone machining
• chip formation
• cutting edge breakdown
• finite elements

ACKNOWLEDGMENTS

The experimental measurements of cutting and thrust forces (the basis of Figure 2) were carried out by C. W. Yeager as part of his MSc thesis (Yeager, 2006).

Notes

*Ductility ranking (1 most ductile) from simulation results, Figure 4.