ABSTRACT
Drilling of high-strength T800 carbon fiber reinforced plastic (CFRP) are widely employed in current aviation industry. Drilling-induced damages frequently occur and affect not only the load carrying capacity of components but also the reliability. As one of effective methods to reduce the drilling-induced damages, advanced tool structures have been widely used. Nevertheless, it is still difficult to realize high machining accuracy and efficiency by this method. This paper compared three different drill bits to evaluate the drilling performance of T800 CFRP composites and the results showed that the dagger drill was a good choice to drill T800 CFRP considering the lowest thrust force and damages. On this basis, ultrasonic vibration was successfully imposed on dagger drill to further improve the drilling performance. The experimental results showed that ultrasonic vibration reduced the thrust force and surface roughness with a maximum decrease of 14.1 % and 62.2 % respectively. Moreover, the maximum hole diameter errors were decreased from 30 µm in CD to 6 µm in UAD. Besides, the mechanisms of force reduction and hole quality improvement by ultrasonic vibration were also revealed. The results suggest that the combination of ultrasonic vibration and dagger drill is a promising strategy for high performance drilling CFRP.
ABSTRACT
The electrosurgical electrode currently stands out as one of the most commonly used tools in minimally invasive surgery. In order to facilitate tissue cutting and accelerate wound healing, tissue adhesion to the electrosurgical electrode is considered as an extremely urgent problem to be solved. In this paper, a novel ultrasonic vibration assisted (UV-A) electrosurgical electrode is firstly proposed to overcome the problem of tissue sticking. The anti-adhesion effects were evaluated by measuring the adhesion force and the weight of tissue adhesion using the electrosurgical electrode with and without UV-A comparatively. Experimental results show that the average adhesion force and the tissue adhesion mass with UV-A were decreased by approximately 60% and 70% respectively, accompanied by smaller thermal injury area compared with that without UV-A. Moreover, the underlying mechanism of anti-adhesion effect with UV-A was revealed by investigating the influence of ultrasonic vibration on electric current, tissue removal and spark discharge. This research suggests that UV-A is a promising and practical method for improving the anti-adhesion performance of electrosurgical electrode.
ABSTRACT
The production of high quality bolt holes, especially on the carbon fiber reinforced plastics/titanium alloy (CFRP/Ti) stacks, is essential to the manufacturing process in order to facilitate part assembly and improve the component mechanical integrity in aerospace industry. Reaming is widely used as a mandatory operation for bolt holes to meet the strict industry requirements. In this paper, the ultrasonic elliptical vibration-assisted reaming (UEVR) which is considered as a new method for finish machining of CFRP/Ti stacked holes is studied. The paper outlines an analysis of tool performance and hole quality in UEVR compared with that in conventional reaming (CR). Experimental results show that the quality of holes was significantly improved in UEVR. This is substantiated by monitoring cutting force, hole geometric precision and surface finish. The average thrust forces and torque in UEVR were decreased over 30% and 60% respectively. It is found that, during first 45 holes, better diameter tolerance (IT7 vs. IT8), smaller diameter difference of CFRP and Ti holes (around 3µm vs. 12µm), better geometrical errors were achieved in UEVR as compared to CR. As for surface finish, both of the average roughness and hole surface topography in UEVR were obviously improved.
ABSTRACT
The rotary ultrasonic elliptical machining (RUEM) has been recognized as a new effective process to machining circular holes on CFRP materials. In CFRP face machining, the application of grinding tools is restricted for the tool clogging and the machined surface integrity. In this paper, we proposed a novel approach to extend the RUEM process to side milling of CFRP for the first time, which kept the effect of elliptical vibration in RUEM. The experiment apparatus was developed, and the preliminary experiments were designed and conducted, with comparison to conventional grinding (CG). The experimental results showed that when the elliptical vibration was applied in RUEM, a superior cutting process can be obtained compared with that in CG, including providing reduced cutting forces (2-43% decrement), an extended tool life (1.98 times), and improved surface integrity due to the intermittent material removal mechanism and the excellent chip removal conditions achieved in RUEM. It was concluded that the RUEM process is suitable to mill flat surface on CFRP composites.
