软骨之黏弹特性 - 机械工程学系.ppt

Bone Cartilage Prof. M.S. Ju Dept. of Mechanical Eng. NCKU 12.1 Introduction Bone works in small strain range, biology sensitive to strain (stress) Anisotropic, stress-strain strain-displacement are linear Cartilage related to bone (calcified cartilage); small friction coefficient, Lubrication shock absorption, multi-phasic structure (fluids, ions, solids) triphasic theory 12.1.1 Anatomy of a long bone Shaft (diaphysis), expansion (metaphysis), for immature, metaphysis surmounted by epiphysis united to metaphysis via growth plate (epiphyseal plate) Coefficient of friction between articulate cartilage ~ 0.0026! Growth plate- place where calcification of cartilage occur. For matured, epiphyses fused with metaphyses Diaphysis: hollow tube, wall dense cortex (compactum) Medulla or medullary cavity: central space, contains bone marrow Periosteum: covering external surface of long bone, except articulation Inner layer, active cells enlargement remodeling; osteogenic layer Outer layer, fibrous comprised almost entire periosteum Over most of diaphysis, periosteum is tenuous loosely attached blood vessels are capiliary; At expanded ends, ligaments are attched firmly can convey large size blood vessels; Same at ridges along diaphysis. Note: mechanical properties depend on which part of bone is considered. Table 12.1:1 Notes cortical region of diaphysis Specimens taken from compactum Microscopic observation Composite material Basic unit: Haversian system (osteon) Artery or vein at center Blood vessels connected by Volkmann’s canals (transverse) Weight % 2/3 inorganic material, mainly hydroxyapatite, 3Ca3(PO4)2. Ca(OH)2 small quantity of other ions Tiny crystals 200 A long, area 2500 A2, Collagen, HA crystals arranged along length of collagen fibrils. Arrangement in fibers Woven-fiber bone Lamallae in osteons: concentric Lamallae in surface: parallel to surface 12.1.2 Bone as a Composite Material Collagen hydroxyapatite Young’s modulus of fluorapatite ~ 165GPa Stee