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CSME 2019/08
Volume 40 No.4
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375-383
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Transient Elastohy Drodynamic Lubrication of Artificial Hip Joints with Non-Newtonian Synovial Fluids
Li-Ming Chua, Chang-Jian Cai-Wanb and Yuh-Ping Changc
aDepartment of Applied Science, National Taitung University, Taitung City 95092, Taiwan, ROC
bDepartment of Mechanical and Automation Engineering, I-Shou University, Kaohsiung City 84001, Taiwan, ROC
cDepartment of Mechanical Engineering, Kun Shan University, Tainan City 71070, Taiwan, ROC
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Abstract:
This paper analyzes that the ball (femoral head) squeeze to the ultra-high molecular weight polyethylene (UHMWPE) acetabulum component gradually under constant load condition with non-Newtonian synovial fluid by using the constrained elastic deformation mode. This phenomenon belongs to hard-on-soft transient elastohydrodynamic lubrication (EHL) problem. The Newton-Raphson method (NRM) and the Gauss-Seidel iteration method are used to solve the transient modified Reynolds equation, the elasticity deformation equation, and the load balance equation simultaneously in spherical coordinates to obtain the transient pressures (P) and film thicknesses (H). The simulation results reveal that the pressure becomes concentrated toward the center gradually with decreasing film thickness. In order to maintain mass conservation, a necking phenomenon of the joint synovial fluid film thickness would occur at the outlet, so the minimum film thickness occurs at the outlet instead of the central area. As the characteristic length (L) increases, the synovial fluid film thickness increases, the central pressure decreases, but pressure increases outside the central area. The necking phenomenon would increase with decreasing the characteristic length. This study not only has academic innovation but also provides information to the biomedical industry for design artificial hip joints, so it has great potential for biomedical industrial application.
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Keywords: Artificial hip joints,EHL, non-Newtonian Synovial fluids
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©
2019
CSME , ISSN 0257-9731
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