Issue 50

M.R.M. Aliha et alii, Frattura ed Integrità Strutturale, 50 (2019) 602-612; DOI: 10.3221/IGF-ESIS.50.51 608 different locations of bones was straight and along the initial crack with no significant curvature. A typical fracture surface (with magnification of 60x) observed for one of the bone samples has also been shown in Fig. 9. The microstructure of the investigated bone exhibits a rather smooth pattern that demonstrates dominantly tensile and brittle type of fracture for the tested SENB specimens made of bovine femur bone. Indeed, the fracture patterns of the tested bovine bone are very similar to cleavage fracture in brittle materials in which the micro cracks propagate through the weak paths of cement line leading a tensile type brittle fracture. In addition, despite many engineering and industrial materials that have continuum and homogenous structure, the micro structure of bone materials shown in Fig. 9 consists of different parts including osteons, vascular and volkmann canals and secondary osteons [75,76] which results in non-continuum and non-homogenous micro structure for the bone as natural material. Due to random distribution of such parts inside the bone and also difference in the size and number of these particles (that some of them like vascular canals and secondary osteons act as stress concentrations or weak points), a significant and noticeable scatter in their fracture and cracking behavior might be inevitable and expected as shown via the several fracture experiments of this research for a same bovine femur bone material. Figure 8 : Relationship between the fracture toughness and fracture energy of tested bone samples. Figure 9 : Typical fracture surface of tested SENB specimens under pure mode I loading condition. C ONCLUSIONS  Fracture toughness ( K Ic ) of two fresh femur bones of the same bovine was measured experimentally using single edge notch bend beam (SENB) specimen. ( K Ic ) 2 = 1106.2 J - 4.5478 R² = 0.9576 0 20 40 60 80 100 120 140 0 0,02 0,04 0,06 0,08 0,1 0,12 K Ic 2 ((MPa) 2 m) Fracture Energy (J)