Materials like Bone are considered to be verycomplex ones due to their heterogeneous and anisotropicnature. Bone material also has a hierarchical structure thatchanges from nano-scale to macro-scale. Bone contains goodamount of non linearity during deformation. This nonlinearitymay be due to several toughening mechanisms and presence ofwater in the bone material. Many researchers used linearelastic fracture mechanics approaches such as critical stressintensity factor, critical energy released rate and crack growthresistance curve etc. for examining toughness of bone. Theseapproaches are inadequate to characterize fracture in presenceof substantial nonlinearity preceding fracture. Crack tipopening displacement (CTOD) approach based on elasticplastic fracture mechanics has been applied in the presentwork to provide an estimate of fracture toughness of buffalocortical bone for longitudinal as well as transverse orientationof cracking. Fractured surfaces of buffalo cortical bone arealso examined with the help of scanning electron microscopefor both longitudinal and transverse orientation of cracking inorder to classify micro-mechanics of cracking of such bones. Itis noticed that this bone is having plexiform character. In thispaper average CTOD toughness (δc) values are measured forbuffalo cortical bone in both longitudinal and transverseorientation of cracking. The equivalent K-fracture toughnessand J-toughness values are also calculated employing thecorresponding δc values in the two orientations of cracking andcompared with the values available in the literature. It issuggested that the CTOD (δc) and J-toughness are betterparameters to predict the realistic fracture resistance of bone.
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