Daxi Geng

Rotary ultrasonic elliptical machining for side milling of CFRP: tool performance and surface integrity.

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.

Comparison of drill wear mechanism between rotary ultrasonic elliptical machining and conventional drilling of CFRP

Carbon fiber-reinforced plastic (CFRP) is widely used as aircraft structural components for its superior mechanical and physical properties. Meanwhile, the rotary ultrasonic elliptical machining (RUEM), as a new drilling method in which an elliptical ultrasonic vibration is imposed on the end of the drill, can reduce tool wear effectively. In this paper, we firstly presented an investigation on the wear mechanism of diamond core drill in RUEM of CFRP in comparison with the conventional drilling (CD). A series of drilling experiments were performed including the drilling force measurement, the observation of drill topographies, and machined hole surface. The experiment results indicated that the drill performance in RUEM of CFRP was improved significantly in comparison with that in CD. Because the length of steady region rised by 39% and the tool life increased by 28% in RUEM than those in CD, respectively. With the observation of drill surface under a microscope, it was validated that less chip adhesion and more grain micro-fracture appeared in RUEM, which had a positive effect on the better drilling performance, such as lower drilling force, smoother hole surface.

Feasibility study of ultrasonic elliptical vibration-assisted reaming of carbon fiber reinforced plastics/titanium alloy stacks

HighlightsA drilling method by ultrasonic elliptical vibration‐assisted reaming (UEVR) is proposed.Both of hole accuracy and surface quality were greatly improved in UEVR.The factors for the cutting force reduction in UEVR were revealed.The reason for closer hole tolerances for CFRP and Ti were theoretically analyzed. 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 3 &mgr;m vs. 12 &mgr;m), 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.

Effect of speed ratio in edge routing of carbon fiber-reinforced plastics by rotary ultrasonic elliptical machining

Edge routing carbon fiber-reinforced plastic structures is the first and mandatory operation after demolding. In order to solve the problems such as tool clogging and mechanical damages at the machined surface in edge routing of carbon fiber-reinforced plastics by grinding tools, the rotary ultrasonic elliptical machining technique was used in edge routing carbon fiber-reinforced plastics for the first time. First, the rotary ultrasonic elliptical machining principle and an analysis of the effect of the speed ratio, Rs (i.e., the ratio of the nominal cutting speed to the maximum tool vibration speed in the cutting direction), on the relative motion of the tool and workpiece were presented as the speed ratio greatly influences the rotary ultrasonic elliptical machining performance. Then, the edge routing experiments by rotary ultrasonic elliptical machining were conducted to study the machining quality at different speed ratios. The results showed that the grinding forces at Rs 0.1 decreased about 19% (normal grinding force) and 17% (tangential grinding force) than that at Rs 0.8 after cutting 100min. The tool diameter reduction at Rs 0.1 was 34% lower than that at Rs 0.8 after cutting 100min and the machined surface integrity at Rs 0.1 was also modified at the end of the experiments. The experimental findings suggest that the optimal integrated surface could be achieved by applying the rotary ultrasonic elliptical machining method with the fine size diamond grinding tool and the low speed ratio.

Improving anti-adhesion performance of electrosurgical electrode assisted with ultrasonic vibration

HighlightsA novel ultrasonic vibration‐assisted (UV‐A) electrosurgical electrode was firstly proposed.The adhesion force with UV‐A was decreased 60–75% without affected by load.The mass of adhesion tissue was decreased by 80% with UV‐A.The underlying mechanism with UV‐A for soft tissue anti‐adhesion was revealed. 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.

Removal analyses of chip and rod in rotary ultrasonic-assisted drilling of carbon fiber-reinforced plastics using core drill

Carbon fiber-reinforced plastics (CFRP) have been widely applied in aerospace industry as structural components due to their excellent mechanical and physical properties. Meanwhile, the drilling process is indispensable for machining the assembly holes of CFRP. However, in the conventional drilling process of CFRP, it is prone to produce the defects including delamination, spalling, fuzzing, and tool wear. In recent years, the rotary ultrasonic-assisted drilling (RUAD) with diamond core drill, as a novel machining method, has been employed to reduce the defects. But this is few reported investigations on chip adhesion of tool surface and machined rod jamming into core drill tool during RUAD of CFRP. Therefore, this paper detailedly reported a study on removal analyses of chip and rod in RUAD of CFRP using core drill under no cooling condition for the first time. To begin with, the principle analysis on RUAD of CFRP was presented to illustrate the removal process of chip and rod. And then, the experiment analysis on RUAD of CFRP was carried out to observe the removal effects of chip and rod. The experimental results indicated that compared with the common drilling of core drill, when the vibration amplitude reached 5.0 and 7.5 µm in RUAD, the cutting ability of core drill tool was greatly enhanced, excellent removal effects of chip and rod were obtained, which obviously reduced the chip adhesion, rod jamming, rod fragmentation, thrust force, cutting temperature, and surface roughness, improved the dimensional accuracy of machined hole and rod diameter, prolonged the tool life, as well as acquired superior surface integrity of machined hole and flat fibers fracture surfaces. Furthermore, the experimental results also validated the accuracy of the principle analysis.

Feasibility study on the rotary ultrasonic elliptical machining for countersinking of carbon fiber–reinforced plastics

Carbon fiber–reinforced plastics have been widely applied in aerospace industry as aircraft structural components due to their excellent mechanical and physical properties. The countersinking process of the carbon fiber–reinforced plastic hole is indispensable for the assembly of countersunk head screw. In conventional countersinking process of carbon fiber–reinforced plastics, it is prone to produce the delamination, fiber pullout, poor surface levelness and dimensional accuracy of countersunk hole. As a new technology, the rotary ultrasonic elliptical machining for countersinking of carbon fiber–reinforced plastics is employed, which is a non-traditional process that can effectively improve the surface levelness, surface integrity and machining accuracy of carbon fiber–reinforced plastic countersunk hole. This article reported a feasibility study on the rotary ultrasonic elliptical machining for countersinking of carbon fiber–reinforced plastics without coolant for the first time. The processing principle of rotary ultrasonic elliptical machining for countersinking was illustrated according to the countersinking models and the equations of motion locus. Based on the principle analysis, the surface levelness, tool blades’ path and countersunk hole surface morphology in rotary ultrasonic elliptical machining of the separated and unseparated types were analyzed compared to that in conventional countersinking. In addition, the rotary ultrasonic elliptical vibration transducer was designed and fabricated, as well as the experimental platform was set up. The experimental results demonstrated that the rotary ultrasonic elliptical machining achieved much better results than that in conventional countersinking, such as lower thrust force, torque, cutting temperature, better surface levelness, hole dimensional accuracy, surface integrity and chip-removal effect. The experimental results also verified the feasibility of rotary ultrasonic elliptical machining for countersinking of carbon fiber–reinforced plastics.