The titanium alloy artificial knee joint is used extensively in the current medical industry due to its distinct characteristics and properties that are like the real human knee joint, but it does need to be polished to improve its performance and service life before it can be used. Due to the complicated surface profile, the traditional abrasive flow machining technique cannot achieve a good surface finish offering uniformity and quality. Thus, in this paper, a proper constrained flow channel is designed to conduct the abrasive flow machining of the titanium alloy artificial knee joint surface to overcome these issues. A numerical study is first conducted to explore the distribution of abrasive flow velocity and pressure near the target surface in the constrained flow channel by using the COMSOL Multiphysics software, and it is found from the distribution of the dimensionless material removal rate on the target surface that the exchange of the abrasive flow inlet and outlet during the machining process is recommended to improve the surface finish uniformity. Then, the corresponding experiments are conducted to analyze the surface morphology before and after the abrasive flow machining process. It is found that the surface roughness of the target surface decreases from approximately 394 nm to 171 nm with good uniformity as well. Therefore, the proposed abrasive flow machining method with a properly designed constrained flow channel is useful for the rough polishing and fine finishing of the titanium alloy artificial joint.

To improve medical device hole inner wall quality and overcome issues of traditional abrasive flow methods—limited fluidity in small holes causing deformation due to high inner wall pressure, and slow processing with low viscosity abrasives—a new method called shear thickening abrasive flow polishing is suggested. It uses shear thickening fluid as the medium. By leveraging the Preston equation and fluid dynamics theory, this study establishes both an abrasive flow dynamics model and a material removal model for the shear thickening abrasive flow machining of small titanium alloy hole workpieces in medical instruments. Utilizing the COMSOL software, the flow field state of shear thickening fluid within small holes is examined under varying flow behavior indexes and flow velocities. The findings demonstrate that shear thickening fluid yields superior polishing effects compared to Newtonian fluid. Elevating the flow behavior indexes facilitates a higher material removal rate on the inner wall surface; however, excessively large flow behavior indexes diminish the uniformity of material removal, thereby hindering the attainment of a high-quality polished surface. Furthermore, excessively large flow behavior indexes can reduce fluidity and consequently lower the efficiency of the polishing process. Conversely, while maintaining a constant flow behavior index, increasing the flow velocity contributes to an enhanced material removal rate and improved polishing efficiency. Nevertheless, as the flow velocity rises, the uniformity of inner wall surface roughness diminishes, posing challenges in achieving a high-quality polished surface.

The wear of artificial joints can lead to joint noise and tissue pathology within the human body, which is a primary factor affecting their service life. In response to the issue of wear in ceramic–titanium alloy artificial hip joints, this study employed hip joint wear simulations and experimental wear testing on hip joint specimens to investigate the impact of different contact surface parameters on the wear of ceramic–titanium alloy articulating surfaces. The objective was to provide guidance for joint surface treatment to minimize wear. The simulation results demonstrated that the contacting surfaces of the articulating components exhibited a crescent-shaped surface composition before and after wear. The initial variation in the surface friction coefficient had minimal influence on the wear rate after stabilization, whereas excessively high friction coefficients led to erratic changes in wear depth. Based on the simulation results, experimental research was conducted to compare the wear results of different surface roughness values ranging from 60 to 550 nm. The findings revealed that a surface roughness of 150 nm exhibited the least amount of wear and the best anti-wear performance. Furthermore, an exploration of the mechanism behind the influence of different surface friction coefficients on the wear of the articulating surfaces provided valuable insights for surface processing and wear analysis of artificial joints.