PSI - Issue 6

M. Wang et al. / Structural Integrity Procedia 00 (2017) 000–000

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Mayao Wang et al. / Procedia Structural Integrity 6 (2017) 64–68

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The cracks in these models, which grew from the left-hand to the right-hand, propagated mostly along the cement lines - a weak interface between the osteons and the interstitial matrix. These crack deflections, which were also observed in Chan’s results, could protect osteons from crack destroying them and improve fracture resistance (Yeni & Norman 2000 and O’Brien et al. 2005). So, the zero-thickness cohesive element method is a powerful tool to investigate the effect of micro-morphology of osteonal structure on fracture toughness in human cortical bone. Importantly, the characteristic features of microstructure of young human cortical bone could resist crack penetrating osteons resulting in the best performance of the studied four types of human cortical bone.

Table 2. Fracture toughness initiation and slope of young group of human cortical bone

Slope, MPa(m) 1/2 /mm Porosity (%)

1/2

K 0 , MPa(m)

Group

Young1 Young2

1.38 1.52

1.16 1.16

5.96 5.31

Figure 2. Crack propagation path during fracture process in human cortical bone (the red circles indicate that crack propagate along cement line area)

Acknowledgement

Financial support of the FP7 IRSES project TAMER “Trans-Atlantic Micromechanics Evolving Research "Materials containing inhomogeneities of diverse physical properties, shapes and orientations” (Grant no. IRSES GA-2013-610547) is gratefully acknowledged.

References

ASTM, 1997. E399-90. Standard test method for plane-strain fracture toughness of metallic materials. 1991 Annual Book of ASTM Standards , 3, 451–485. Budyn, É. & Hoc, T., 2007. Multiple scale modeling for cortical bone fracture in tension using X-FEM. Revue Européenne de Mécanique Numérique , 16, 213–236. Chan, K.S., Chan, C.K. & Nicolella, D.P., 2009. Relating crack-tip deformation to mineralization and fracture resistance in human femur cortical bone. Bone , 45(3), 427–434. Koester, K.J. Iii, J. A., & Ritchie, R. O., 2008. The true toughness of human cortical bone measured with realistically short cracks. Nature Materials , 7(8), 672–677.