Mechanism And Key Technologies Of Ultrasonic Cutting Aramid Honeycomb Core

Honeycomb sandwich components have high specific strength and specific stiffness and excellent impact resistance,vibration reduction,noise elimination,wave penetration,heat insulation,and other properties;thus,they which are widely used in the aerospace field.The honeycomb sandwich components is made of a honeycomb core bonded with upper and lower panels.To meet the manufacturing requirements of honeycomb sandwich components,the bonded surface of the honeycomb core needs to be processed.At present,most of the honeycomb cores used are aramid honeycomb cores.Because aramid honeycomb is the cellular composite material with low stiffness,machining damages such as cell deformation,burring,and tearing easily occur when using the traditional high-speed milling method,and the processing quality of the honeycomb core is not easy to guarantee,which affects the performance of the honeycomb sandwich components produced.In addition,high-speed milling of honeycomb core will generate chip dust,and the processing environment is harsh.Ultrasonic cutting is a machining method for cutting honeycomb core with special tools under the action of ultrasonic vibration.It has the advantages of small cutting force,good machining quality,and environmental friendliness and has been widely studied in recent years.As an advanced machining method for honeycomb core,ultrasonic cutting is significantly different from high-speed milling in material removal,machining mechanism,and processing technology.At present,there is a lack of in-depth research on the theory and key technologies of ultrasonic cutting of honeycomb core at home and abroad.In this paper,based on the analysis of the ultrasonic cutting process of honeycomb core,tool-in-hand system and tool-in-use system of tools are established,and the influences of cutting motion,tool attitude,and ultrasonic vibration parameters on the working angles of tools are studied.The ultrasonic cutting mechanism of the aramid honeycomb core is revealed,and the damage control method is studied.By breaking through the key technologies of ultrasonic cutting of honeycomb core,the vibration system,a series of tool holders,and a CNC machine tool for ultrasonic cutting of honeycomb core are developed.According to typical honeycomb core characteristics,ultrasonic cutting processing technologies are developed,and machining verification of test parts with typical features and aeronautic honeycomb core components is realized.The main research contents and conclusions are as follows:(1)Tool-in-hand systems of straight blades and disc cutters used in ultrasonic cutting of honeycomb core are established.Considering the cutting motion,tool attitude,and ultrasonic vibration in the ultrasonic cutting process,a tool-in-use system is established.The influences of the ultrasonic cutting motion,tool attitude,and ultrasonic vibration parameters of the straight blade and disc cutter on the working angles are analyzed.On this basis,the influence mechanism of the change in the working rake angle,working clearance angle,and working wedge angle on the deformation of the chip and machining surface during ultrasonic cutting of honeycomb core is revealed.The reasons for machining damage,such as surface crushing and burring,in machining honeycomb core are expounded,and the technological methods of largeamplitude cutting,blade-inclined cutting,and inclination cutting are proposed to control the machining damage of honeycomb core during ultrasonic cutting.(2)According to the instantaneous contact characteristics of the cutting tool and material in the ultrasonic cutting process of straight blades and disc cutters,the contact states of the cutting tool and material in the ultrasonic cutting process of honeycomb core are analyzed,and tool-workpiece contact rate models are established considering the geometric parameters of the cutting tool,tool attitude,and ultrasonic cutting parameters.The influence of ultrasonic cutting parameters on the tool-workpiece contact rate is revealed.According to the principle of energy conservation,the energy relationships of the cutting material in the ultrasonic cutting process are analyzed.The energy balance equations of the material cutting process are established considering the geometric parameters of the tool and ultrasonic cutting parameters.Finite element models of the fracture force for ultrasonic cutting of honeycomb materials with a straight blade and disc cutter are established,and the influence of ultrasonic cutting parameters on stress intensity factors is studied.Based on the modeling and analysis above,the cutting mechanism of the ultrasonic cutting honeycomb materials is revealed.(3)Aiming at the requirements of a large-amplitude output and frequency consistency of the vibration system in the ultrasonic cutting of honeycomb core,an integrated design method of a horn is proposed considering the influence of the cutting tool on ultrasonic vibration.A large-amplitude horn with a cylindrical Bezier compound profile is designed and optimized using a nondominated sorting genetic algorithm.The large-amplitude vibration output of an ultrasonic cutting tool is realized at 20 kHz frequency,and the amplitude is greater than 20 μm.(4)A series of ultrasonic cutting tool shanks for straight blades and disc cutters are developed.The mechanical and electrical integration technology of the ultrasonic cutting system and the CNC machine tool are studied.A honeycomb core ultrasonic cutting machine tool is developed to meet the ultrasonic cutting requirements of honeycomb core components.(5)Using a series of ultrasonic cutting tool shanks and ultrasonic cutting machine tools for honeycomb core,ultrasonic cutting process tests of aramid honeycomb core are carried out systematically.Ultrasonic cutting processing technologies for typical honeycomb core features,such as planes,inclined planes,arc surfaces,convex tables,grooves,and curved surfaces,are developed,and machining verification of typical characteristic test parts and aviation honeycomb core components is realized.