No abstract

Artificial hip joint surgery is one of the most successful methods used to restore the functioning of damaged hip bones. But there are obstacles to the use of artificial hip bone, which is the amount of friction occurring and wears. To overcome these obstacles, a surface of the artificial hip joint is modified by adding dimples in order to minimize the contact pressure of solid and to reduce friction and wear. The purpose of this study is to determine a better of lubrication performance with the variations of the dimple arrangements under the normal walking condition. Simulation results have already exited the point of convergence studies, and the obtained results are such as hydrodynamic pressure, contact pressure, and the film thickness of the lubricant with the variations of the number and pitch dimples. The results of the CSM method under dry condition, it shows that the addition of surface with dimples has a positive effect to reduce the contact pressure and indirectly reduce wear. The maximum surface contact pressure is 54.84 MPa with dimple and 94.22 MPa without a dimple. The results of the FSI method under lubrication condition, it was found that the variation of 7 dimples with a dimple pitch of 500 μm has the best lubrication performance. The hydrodynamic pressure is 0.73 Pa, the contact pressure is 0.42 Pa, and the film thickness of the lubricant is 29.59 μm. The increase of film thickness that occurs due to hydrodynamic pressure will cause the fluid lift force to withstand the loading of the solid structure.

This paper proposes the replacement of artificial hip joints which is one of the successful methods used to restore the movement of damaged hip bones. The main contribution of this work is to reduce wear caused by contact pressure between the femoral head and acetabular cup surfaces, where the average wear rate is very high. This can be achieved through the use of dimple on the femoral head surface from the artificial hip joint and subsequently computed by using the Archard equation. To validate the contact pressure accuracy of the proposed model, mesh sensitivity that used with 3 levels of mesh size are 1.2, 1.1 and 1.0. In this study for more accurate result, the mesh sensitivity used is with the mesh size of 1.0. The performance calculation results from wear are shown that in a hip joint using dimple the maximum contact pressure and the wear depth are decreased compared to the hip joint without dimple which are 67.25 MPa and 1.064 x10−10 mm from the previous value of 77.44 MPa and 1.185 x10−10 mm. Therefore, based on differences in the distribution of contact pressure that occurs shows volumetric wear on the hip joints using a dimple lower than without a dimple.

This paper proposes a modeling approach for biodegradation of implant-bone scaffolds. A Computer simulation was performed to determine the wall shear stress (WSS) and permeability of simulated body fluid (SBF) with a constant flow rate of 0.025 ml/min. In this study, four morphological samples were used to immersion time from 0 to 72 hours. Each specimen was given a different bone strain (1000-3500 μstrain) which created a variation of displacement in the bone scaffold. The method used in the simulation was the fluid-structure interaction (FSI). The pressure drop through the specimen decreases linearly, the permeability increases as the porosity increases, and the mean wall shear stress decreases due to the length of the immersion time. It was obtained that the permeability values of the implant-bone scaffold increases from 7.79×10-10 m2 to 1.09×10-9 m2 and the mean shear stress values decrease from 2.86×10-3 Pa to 1.38×10-3 Pa.