D.W. Wang

Microparticle entrapment for drug release from porous-surfaced bone implants.

Abstract Metallic bone implants face interfacial concerns, such as infection and insufficient bone formation. Combination of drug-loaded microparticles with the implant surface is a promising approach to reducing the concerns. The present study reports a simple method for this purpose. Drug-loaded chitosan and alginate microparticles were separately prepared by emulsion methods. Dry microparticles were introduced into porous titanium (Ti) coatings on Ti discs, and induced to agglomerate in pores by wetting with water. Agglomerates were stably entrapped in the pores: 77–82% retained in the coating after immersion in a water bath for 7 d. Discs carrying drug-loaded microparticles showed a rapid release within 6 h and a subsequent slow release up to 1 d. After coculture with Staphylococcus epidermidis for 24 h, the discs formed inhibition zones, confirming antibacterial properties. These suggest that the microparticle entrapment-based method is a promising method for reducing some of the bone–implant interfacial concerns.

Improving Dynamic and Tribological Behaviours by Means of a Mn–Cu Damping Alloy with Grooved Surface Features

In this work, the effect of the damping component with/without individual grooved surface features on the friction-induced vibration and noise (FIVN) and surface wear performance is studied experimentally and numerically. The experimental results show that introducing a grooved damping component in the system has a significantly improved capability in suppressing the generation of FIVN. In addition, it is observed that the friction system with a grooved damping component suffers slighter wear. Numerical results show good agreement with the FIVN events observed in the experimental test. Through analysing the deformation behaviour of damping component and the contact behaviour of the friction system during friction process, it is speculated that the deformation behaviour of damping component plays a significant role in affecting the contact pressure and FIVN behaviour. In addition, linking the vibration performance and wear evolution, the connection between damping, and vibration and wear behaviour is discovered, which can further explain why the friction system with a grooved damping component shows improved capability in suppressing the FIVN of friction system.

The influence of the angular distribution of a grooved surface texturing on the generation of friction-induced vibration and noise:

This study experimentally investigated the influence of angular distribution of a grooved surface on wear properties as well as friction-induced vibration and noise characteristics. The surfaces of brake disc material were modified by cutting grooved surfaces with different angular distributions. The differences between the grooved and smooth surfaces in friction and wear and friction-induced vibration and noise were evaluated. This was performed via a pad-on-disc test configuration where the brake pad material was used as a counterface. The test results indicated that all the grooved surfaces with different angular distributions had significant potential in improving friction and wear behaviors of the contact surfaces and also in reducing the amplitudes of high-frequency vibration accelerations and noise pressure levels. Additionally, the results indicated that the ability of the grooved surfaces to suppress the generation of noise is closely related to the angular distribution of the grooves and the interference length of the grooved surfaces on the contact interface. The grooved surface allowed for entrapping and exhausting wear debris from the contact interface, which improved the wear status, and this was one of the reasons for the noise reduction of the grooved surface to a certain extent. Meanwhile, another reason was that the grooved surface interrupted the concentrated contact pressure and changed the contact pressure distribution on the leading edge of the contact surface.

Study on the Correlation Between Dynamical Behavior and Friction/Wear Mechanism Under the Effect of Grooves

In this work, the interfacial friction and wear and vibration characteristics are studied by sliding a chromium bearing steel ball (AISI 52100) over both multi-grooved and single-grooved forged steel disks (20CrMnMo) at low and high rotating speeds in order to reveal the effect mechanism of groove-textured surface on tribological behaviors. The results show that the grooves modify the contact state of the ball and the disk at the contact interface. This consequently causes variations in the normal displacement, normal force, and friction force signals. The changes in these three signals become more pronounced with increasing groove width at a low speed. The collision behavior between the ball and the groove increase the amplitude of vibration acceleration at a high speed. The test results suggest that grooves with appropriate widths could trap wear debris on the ball surface while avoiding a strong collision between the disk and the ball, resulting in an improvement in the wear states.

Experimental and Numerical Study of Friction-Induced Noise of Brake Pad Materials Having Grooved Surface

An experimental and numerical study was performed in this work to predict the squeal instability when pad specimens having different surfaces rotating on a brake disc specimen. The numerical results were consequently compared with the experimental results to investigate the effect of surface modification of pad materials on squeal generation. It was shown that surface modification of pad materials had a significant influence on the squeal instability. Diagonal grooved surface was found to be able to efficiently reduce squeal generation, which can be mainly attributed to its relatively smaller contact pressure distribution area compared to that of the smooth surface.