Issue 50

M.R.M. Aliha et alii, Frattura ed Integrità Strutturale, 50 (2019) 602-612; DOI: 10.3221/IGF-ESIS.50.51 605 Figure 2 : Geometry and loading conditions of the SENB specimen used for fracture experiments on bone material. Figure 3 : Test setup used for bone fracture toughness testing. E XPERIMENTAL RESULTS AND DISCUSSION typical load-displacement curve for one of the tested SENB specimens has been presented in Fig. 4, demonstrating linear elastic fracture behavior of tested bovine bone cut along the longitudinal direction. Thus the framework of LEFM was used to study the fracture behavior and obtain the fracture toughness value of tested bone samples. The calculated fracture results including the fracture toughness values and fracture energies for the tested bovine bone have been presented in Figs. 5 to 7. According to Figs. 5 and 7, a natural scatter is seen for fracture behavior of tested bone samples that such observation is inevitable for bone materials that have orthotropic nature in general. According to the fracture toughness results, the mode I fracture toughness value in the tested bone femur varies from minimum value of 4.9 MPa√m to maximum value of 10.4 MPa√m. Similarly, the lower and upper limits for the fracture energy value are 0.023 J and 0.113 J, respectively. Variations of measured fracture toughness ( K Ic ) for different SENB specimens given from different locations of left and right femurs (i.e. from top and bottom of bone or frontal or lateral side of the bone) are shown in Fig. 5. This Figure demonstrates that the average value of K Ic obtained from the left femur bone is nearly identical with the right femur of the same bovine. The average fracture toughness was obtained approximately equal to 6.8 MPa√m for the whole samples. Tab. 1 presents and compares the mode I fracture toughness value of bovine bone material reported by different researchers. It can be seen from Tab. 1 that the corresponding value of K Ic determined in the current research is quite in good agreement with previous data obtained for the K Ic of bovine bone. However, the fracture toughness K Ic value depends noticeably on the orientation and location of sample extraction from the bone. Generally, it is seen from Fig. 6 that the lateral or side parts of the bone are approximately 20 to 30 % weaker than the frontal part (i.e. along the marked line shown in Fig. 1) of the bovine femur bone. A