Rotary Ultrasonic Elliptical Machining Research Articles

Delamination formation and suppression during rotary ultrasonic elliptical machining of CFRP

As a superior hole manufacturing process, rotary ultrasonic elliptical machining (RUEM) has been successfully employed for drilling carbon fiber reinforced plastics (CFRPs) recently. The delamination of CFRP during drilling is generally considered as the most undesirable form of damage and the most challenging failure mode. In order to reduce the delamination in this novel process, it is important to understand the formation and suppression mechanisms during RUEM of CFRP. In this study, the delamination formation in both core drilling (CD) and RUEM was observed and analyzed. The variation trend of delamination factor with feed speed as well as cutting speed was obtained. The experimental results show that, compared with CD, RUEM method can effectively reduce hole exit delamination by 5.4%–19.3% between 1/2 plies and 0.7%–8.4% between 2/3 plies at the feed rates from 50 to 100 μm/rev. Moreover, the delamination suppression mechanism in RUEM was fully analyzed and verified. In a word, in the industry practice, RUEM can be considered as a competitive and promising technique to drill CFRP compared to other delamination suppression techniques.

Effects of tool vibration on surface integrity in rotary ultrasonic elliptical end milling of Ti–6Al–4V

Titanium alloys have been applied in aerospace, biomedical, and chemical industries due to their superior mechanical properties. As a novel machining method, rotary ultrasonic elliptical machining has been successfully introduced into high-speed side milling of Ti–6Al–4V recently. However, the surface integrity in end milling of titanium alloy using this method is still unclear. In this study, a comprehensive experiment on surface integrity in rotary ultrasonic elliptical end milling of Ti–6Al–4V was conducted at various vibration amplitudes and cutting speeds. Results show that regular substantial micro-vibration textures in the form of separated ridges are obtained on the machined surfaces in RUEEM. Surface roughness values rise from Ra 0.160 μm to Ra 0.758 μm with the increasing cutting speed and vibration amplitude. Both the thickness of subsurface deformed layer and the value of surface micro-hardness increase with rising amplitude at low cutting speeds, while the hardening effect gradually weakens as the cutting speed increases to 160 m/min. Besides, the values of surface compressive residual stress gradually decrease with vibration amplitudes at low cutting speeds, while opposite trends show at the high cutting speed (160 m/min). This study can provide a new method for the effective control of the surface integrity for high-speed end milling of titanium alloy.

Investigation of the Effect of Vibration Amplitude on the Surface Integrity in High-speed Rotary Ultrasonic Elliptical Machining for Side Milling of Ti-6Al-4V

Investigation of the Effect of Vibration Amplitude on the Surface Integrity in High-speed Rotary Ultrasonic Elliptical Machining for Side Milling of Ti-6Al-4V

Research on the Characteristics of Chips and Tool Flank Wear in High-speed Rotary Ultrasonic Elliptical Machining for Side Milling of Ti-6Al-4V

Research on the Characteristics of Chips and Tool Flank Wear in High-speed Rotary Ultrasonic Elliptical Machining for Side Milling of Ti-6Al-4V

Effects of rotary ultrasonic elliptical machining for side milling on the surface integrity of Ti-6Al-4V

Ultrasonic elliptical vibration-assisted milling methods have recently attracted attention since they can be applied to difficult-to-cut materials. In this study, the effects of rotary ultrasonic elliptical machining parameters for side milling on Ti-6Al-4V titanium alloy machined surface integrity were investigated and compared with conventional machining for side milling. To determine the effects of rotary ultrasonic elliptical machining for side milling, roughness, topography, residual stress, microstructure, and microhardness of machined surface and subsurface were examined. Results show that rotary ultrasonic elliptical machining for side milling significantly improves the integrity of machined surfaces as a result of induced compressive residual stress, more pronounced plastic deformation, and work hardening of the machined surface. It was found that higher cutting speeds of up to 120 m/min and lower feed rates of approximately 0.02 mm/z achieve higher compressive residual stresses on the surface (− 221.21 MPa vs. 2.82 MPa), greater plastic deformation below the surface (up to 40 μm vs. less than 20 μm), and moderate surface work hardening (HV 425.85 vs. HV 414) using rotary ultrasonic elliptical machining for side milling compared to conventional machining for side milling. Finally, in relation to surface roughness (Ra), rotary ultrasonic elliptical machining for side milling was found to cause a slight deterioration of surface characteristics. The results of this study provide a better understanding of rotary ultrasonic elliptical machining for side milling of titanium alloy Ti-6Al-4V.

Cutting temperature and resulting influence on machining performance in rotary ultrasonic elliptical machining of thick CFRP

Abstract As a novel non-conventional machining process, rotary ultrasonic elliptical machining (RUEM) has been successfully used for drilling thick carbon fiber-reinforced plastics (CFRPs) recently. In order to reduce the thermal damage, the measurement of cutting temperature is important when RUEM of CFRP. In this research, the cutting temperatures in both RUEM and grinding drilling (GD) were measured by an infrared camera under dry condition. Temperature trends as functions of feed rate and cutting speed were obtained and the results showed that compared to GD, RUEM can effectively reduce the maximum temperature by 18.8% and 13.1% at the feed rate of 75 and 150 μm/rev respectively. Both mechanisms of temperature reduction and chip adhesion prevention in RUEM were analyzed. In addition, SEM observation of the machined surface revealed that better microstructure was obtained in RUEM compared to GD under the same cutting condition.

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.

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.

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 the rotary ultrasonic elliptical machining of carbon fiber reinforced plastics (CFRP)

Carbon fiber reinforced plastics (CFRP) are used for various aircraft structural components because of their superior mechanical and physical properties such as high specific strength, high specific stiffness, etc. However, when CFRP are machined, rapid tool wear and delamination are troublesome. Therefore, cost effective and excellent quality machining of CFRP remains a challenge. In this paper, the rotary ultrasonic elliptical machining (RUEM) using core drill is proposed for drilling of holes on CFRP panels. This method combines advantages of core-drill and elliptical tool vibration towards achieving better quality, delamination free holes. The cutting force model and chip-removal phenomenon in ultrasonic elliptical vibration cutting are introduced and analyzed. The feasibility to machine CFRP for RUEM is verified experimentally. The results demonstrate that compared to conventional drilling (CD), the chip-removal rate has been improved, tool wear is reduced, precision and surface quality around holes is enhanced, delamination at hole exits has been prevented and significant reduction in cutting force has been achieved.