Residual Stress Measurement around Outer Cortical Bone in Bovine Femur Using the X-ray Sin ² ψ Method

Abstract

Bone continuously adapts to mechanical environment by reconstructing its structure. This property is called bone remodeling. One of the mechanical factors of remodeling is internal stress. Since internal stress remains in bone tissue for a relatively long period of time, it is a kind of residual stress. Bone tissue is a composite material composed of hydroxyapatite (HAp) and collagen fiber. The interplanar spacing of HAp crystals can be noninvasively measured using the X-ray diffraction method because HAp is a crystalline structure. The residual stress of bone tissue can then be calculated from the interplanar spacing. In this work, the sine squared psi method was applied to bone tissue and the residual stresses on eight regions of bone axial and circumferential direction in a specimen were calculated. The cortical bone specimen was cut out from the diaphysis of bovine femur. As a result, it was confirmed that the residual stress existed in bone. The residual stresses of the bone axial direction were different according to the circumferential region.