Shear Stress Analysis and Fillet Curvature Optimization of Cylindrical Indenter in Indentation Test of Bio-Tissue

• Main Authors: Hans Su, 蘇翰飛
• Other Authors: Wen-Fang Wu
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/j6c47v

碩士 === 國立臺灣大學 === 機械工程學研究所 === 107 === The supply of organ donation is far below its demand now. Only with the help of regenerative medicine to reconstruct organs or body tissues can the demand be satisfied. The reconstruction, in general, requires the appropriate selection of material that has similar mechanical properties to human tissues. Before that, the mechanical properties of human tissues must be understood and studied in advance. Since a large portion of human tissues is made of protein, it is worth paying attention to the fact that human soft tissues have low resistance against shear stress. Large shear stress could damage tissues of the specimen and should be avoided. It has been pointed out that shear stress distribution of a tested specimen is influenced by both the geometry and the elastic modulus of the indenter, and so using indentation to test human tissues or equivalent biomaterials to understand their mechanical properties is necessary. Therefore, the relation between the elastic modulus of the indenter and shear stress of the specimen had better be known beforehand. Based on the above considerations, this thesis intends to find the appropriate shape of an indenter that results in small shear stress in specimens during indentation test. The relation between the elastic modulus of the indenter and shear stress of the specimen will also be investigated. The study begins with the finite element simulation of the indentation test carried out by a spherical and a cylindrical indenter, respectively. The results are compared with those obtained directly from the Hertz contact theory for justifying the simulation model including its mesh size. By using the same model, the best fillet curvature of a cylindrical indenter leading to the smallest shear stress in tested specimens is found. The relation of elastic modulus of the indenter and shear stress of the tested specimen is also found. All results are nondimensionalized for future use by other researchers. The major findings of this study are that, for cylindrical indenters used in indentation test of biomaterials, a fillet having 0.1 mm radius of curvature would result in the least shear stress in specimens; and the shear stress decreases along with the decrease of elastic modulus of the indenter.