A Model Of Energy Dissipation In The Post-Yield Deformation Of Bone

INTRODUCTION Bone fracture is a major concern for elderly because the toughness of aged bone becomes more susceptible to impact load.(6) It has been well documented that the post-yield behavior of bone determines the major part of the toughness of bone.(3,4) As a natural composite material, bone primarily comprises a hard mineral phase (mainly hydroxyapatite crystals) and a more compliant collagenous matrix (90% type I collagen).(5) From composite materials perspectives, the biomechanical properties of bone may be the function of the quality and spatial arrangement of its constituents. Some of previous studies have suggested that microcrack accumulation is a major mechanisms in energy absorption during the post-yield deformation of bone.(2,7-9,11-13) On the other hand, some studies indicate that the age-related changes in the collagen network may contribute significantly to the toughness of bone.[Wang, 2001 #101; Wang, 2002 #244; Zioupos, 1999 #253] Moreover, in a recent study Thomason et al. reported that a recoverable bond in the collagen molecules may contribute to the energy dissipation in the post-yield deformation of bone.(10) To elucidate the role of collagen in the postyield deformation of bone, we proposed in this study that the microdamage accumulation leads to the surface energy dissipation during the post-yield deformation of bone, whereas the degradation and deformation in the collagen network are the major mechanisms in the inelastic and viscoelastic energy consumption.