Biotribology最新文献

Functionally graded materials (FGMs) have found extensive applications in the biomedical industry, due to their excellent mechanical and tribological properties. However, new FGM fabrication techniques are yet to be examined for possible enhancements in their properties. This study investigates the tribological properties of Titanium/Hydroxyapatite (Ti-HA) and Titanium/Silicon oxide (Ti-SiO₂) FGM samples fabricated by three die compaction techniques for the application of dental implants. The constituting powder particles were functionally dispersed and mixed using a newly-designed mixer and consolidated by hot dynamic and quasi-static compaction techniques at three different strain rates. Microstructure, hardness, wear resistance, wear penetration depth, and friction coefficient of the FGM samples were then studied in this work. Optical microscopy images exhibited smooth dispersion of powders conforming to a linear grading function. Vickers hardness values of the FGM samples was found to be directly proportional to the strain rate and inversely proportional to the content of the reinforcing phase (HA or SiO₂). Higher strain rate also resulted in higher wear resistance and lower wear penetration depth in all FGMs, with the highest wear resistance being observed in the samples prepared using the Split Hopkinson Bar. Similarly, the coefficient of friction was also shown to be the lowest in Ti-HA samples prepared using Split Hopkinson Bar. Further, microscopic observations revealed that adhesion, delamination and abrasion as the dominant wear mechanisms in all FGM samples. It was concluded that the Ti-HA sample produced by the SHB method enjoyed superior tribological properties, being comparable to that of natural human teeth.

Finite Element wear predictive modelling is a powerful tool that can replace or support costly and time-consuming wear tests. Despite the lively research in this field, particularly in applications to hip replacements, some issues are still open, such as the role of friction in numerical simulations. Indeed, in most wear models, frictionless contact conditions are assumed and wear routines are independent from f. However, the effect of friction on contact and wear modelling of metal-on-plastic hip replacements has never been fully explored in the literature.

In this study we analyse how the friction coefficient affects both the contact features (nominal contact point trajectory, components of the contact force and contact pressure) and the wear parameters, (wear volume and linear wear distribution). A case study of a 32 mm implant was simulated under two different loading and kinematic conditions, considering both vertical and 3D load, and varying the friction coefficient f within the range 0–0.3, for a given k value. Results show that a frictional contact has longer and wider trajectories of the nominal contact point, but slightly lower normal force and contact pressure values, with respect to a frictionless solution. Consequently, contact pressure maps are shifted with respect to the frictionless case but values remain almost the same changing f. The wear volume slightly decreases with f whilst wear maps are very sensitive to it. Results suggest that for f ≤ 0.1 the frictionless hypothesis can be adopted achieving accurate results with the advantage of reduced computational costs.