Abstract: BACKGROUND: Critical energy release rate is a global fracture parameter that could be measured during the failing process, and its value may change under different failure modes even in the same structure.
OBJECTIVE: To propose an approach to predict the critical energy release rate in the femoral cortical bone structure under different failure modes.
METHODS: Three-point bending and axial compression experiments and the corresponding fracture simulations were performed on the rat femoral cortical bone structures. Different critical energy release rates were repeatedly assigned to the models to perform fracture simulation, and the predicted load-displacement curves in each simulation were compared with the experimental data to back-calculate the critical energy release rate. The successful fit was that the differences in the fracture parameters between the predicted and experimental results were less than 5%.
RESULTS AND CONCLUSION: (1) The results showed that the cortical bone structure occurred tensile open failure under three-point bending load, and the predicted critical energy release rate was 0.16 N/mm. (2) The same cortical bone structure occurred shear open failure under axial compression load, and the predicted critical energy release rate was 0.12 N/mm, which indicates that the critical energy release rate of the same cortical bone structure under different failure modes was different. (3) A comprehensive analysis from the perspectives of material mechanical properties and damage mechanism was conducted to reveal the reasons for the differences in the critical energy release rate in the cortical bone structure under different failure modes, which provided a theoretical basis for the measurement of the energy release rate and the accurate fracture simulation.

Key words: critical energy release rate, cortical bone, failure mode, three-point bending, axial compression