Experimental Study On Ultrasonic Trepanning Of Nomex Honeycomb Core

Nomex honeycomb core material is widely used in the field of Aeronautics and Astronautics because of its excellent specific strength and specific stiffness.It is an important material to realize the functions of weight reduction,noise reduction and wave transmission of Aeronautics and Astronautics equipment.According to different requirements,honeycomb core materials need a lot of cutting to obtain the designed structure size and shape.However,Nomex honeycomb core material is a typical difficult-to-machining material.Honeycomb core material has high strength and rigidity along the axial direction of the cell,but its lateral expansion is large and the rigidity is low.In the cutting process,honeycomb core cell is easy to deform,and aramid fiber strength is high and difficultt to cut,which poses a greater challenge to the cutting process.In Nomex honeycomb core components,the contour boundary along the axis of the cell is a common typical feature structure,including the contour boundary of the honeycomb core component edge,the straight line and curve contour boundary of the sink and convex platform structure,which has the characteristics of large quantity and difficult to control the machining quality,but the common ultrasonic cutting and high-speed milling are difficult to meet the machining requirements.Trepanning is a new machining method for the contour boundary of Nomex honeycomb core component.Compared with other machining methods,it can effectively reduce machining defects and improve machining efficiency.However,common trepanning methods still have problems such as large cutting force,uneven machined surface,etc.,and at the same time,there are also problems such as difficulty in chip removal of honeycomb core,easy to block tools,etc.Therefore,based on the traditional trepanning,a new ultrasonic trepanning method is proposed in this paper.The main research contents are as follows:First of all,the kinematics analysis of ultrasonic trepanning is carried out,the ultrasonic trepanning methods of different types of contour boundary are studied,the theoretical contour errors in ultrasonic trepanning are analyzed,the characterization parameters of trepanning contour errors are proposed,and the selection of trepanning step length for different contour characteristics is studied respectively.Secondly,the development of special ultrasonic trepanning tool is carried out.The theoretical design of ultrasonic trepanning tool is carried out from the aspects of tool shape,tool material and ultrasonic vibration performance.The trial production and optimization of trepanning tool is completed,the design scheme of 90 mm long ultrasonic trepanning tool is determined,and the ultrasonic trepanning test platform was built.Then,the influence of trepanning parameters on the cutting force was studied through the ultrasonic trepanning experiment.The composition of cutting force in trepanning is analyzed,the influence of ultrasonic vibration on excision force and the front cutting surface pressure is further studied,and the reason for the reduction of the ultrasonic trepanning force is analyzed.Finally,the Nomex honeycomb core trepanning kerf was observed and the typical morphological features were summarized.The ultrasonic trepanning kerf and traditional trepanning kerf were compared.The characterization parameters of Nomex honeycomb core trepanning quality were proposed,and the effect of processing parameters on the ultrasonic trepanning quality of Nomex honeycomb core was quantitatively studied.