Abstract
The vertical surface is a common and typical characteristic structure among Nomex honeycomb core components. However, the conventional high-speed milling and ultrasonic cutting struggle to meet the high-quality machining requirements of a vertical surface. In this study, an ultrasonic trepanning method is proposed and a special ultrasonic trepanning tool is developed, aiming to improve the machining quality of the vertical surface. The trepanning quality of the vertical surface is further studied from the aspects of dimensional error and trepanning incision quality. Based on the kinematic characteristics of ultrasonic trepanning, a theoretical model of dimensional error in trepanning is established. Meanwhile, the influence of ultrasonic vibration on the trepanning process is analyzed, and the result shows that ultrasonic vibration significantly improves the equivalent elastic constant of the honeycomb core material. The theoretical model is proposed to predict the trepanning dimensional error, which is verified by experiment. The effectiveness of the ultrasonic vibration on the incision quality is verified by several experiments, and the quantitative analysis results demonstrate that ultrasonic vibration significantly improves the trepanning quality of the vertical surface.
Highlights
As the core of the honeycomb sandwich structure, the Nomex honeycomb core is widely used in fields of aviation, aerospace, transportation and so on, for its excellent specific strength, specific stiffness, impact resistance, corrosion resistance and vibration absorption performance [1,2,3,4,5]
In order to study the influence of ultrasonic vibration and other process parameters on the trepanning quality of the Nomex honeycomb core, the chip is removed, and the trepanning incisions on the side of the workpiece are observed by KEYENCE VHX-600E microscope
The LPT of the ultrasonic trepanning with a vibration amplitude of 20 μm was reduced by 40% compared with non-ultrasonic trepanning, and the LPT of the ultrasonic trepanning with a vibration amplitude of 10 μm was reduced by 30% on average
Summary
As the core of the honeycomb sandwich structure, the Nomex honeycomb core is widely used in fields of aviation, aerospace, transportation and so on, for its excellent specific strength, specific stiffness, impact resistance, corrosion resistance and vibration absorption performance [1,2,3,4,5]. The conventional machining method of the vertical surface, which is formed by shredding the honeycomb core by the hogger tool, is the high-speed milling. Compared with high-speed milling, the trepanning method, that uses the trepanning tool to approximately form the vertical surface can improve the quality of the machined surface. It suffers from many problems such as uneven machined surface, large cutting force and easy clogging of the tool with chips. Trepanning is difficult to meet the high-quality machining requirements of the vertical surface in honeycomb core components. The current studies on the ultrasonic cutting of Nomex honeycomb core mainly focus on cutting force modeling, cutting quality, finite element simulation and new processing methods. When the trepanning tool is fed to the set depth, the trepanning tool quickly returns and feeds to the position to carry out the step of ultrasonic trepanning
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