| The Nomex honeycomb composites is widely used in the aerospace industry,high-speed train,construction and other fields with its high specific strength,high specific rigidity and other excellent performances.However,because of its anisotropic mechanical properties and weak stiffness characteristics,the honeycomb is very easily deformed when it is processed.Traditional grinding and milling processes are difficult to achieve high efficient and high quality processing,forming poor surface quality or even scrapping.The ultrasonic machining technology aims at reducing cutting force,enhancing heat dissipation and improving tool wear with intermittent impact cutting characteristics.In order to explore the efficient processing method and technology of Nomex honeycomb composites,ultrasonic machining technology is applied to cut honeycomb composites.In this paper,under the ultrasonic assisted cutting and traditional cutting,a combination of theoretical analysis and experimental research is used to study the cutting of the Nomex honeycomb composites by a straight blade cutter and a disc cutter.The specific research contents are as follows:1.Through the kinematics analysis of ultrasonic assisted cutting honeycomb composite to the straight blade cutter and the disc cutter,the motion equation of cutter was established,and the displacement,velocity and acceleration equation of the straight blade cutter under the ultrasonic assisted cutting were obtained.Thus the cutting length and effective cutting time of the cutter during each vibration cycle are calculated.The rule of ultrasonic cutting path and cutting angle of disc cutter changing with tool speed is obtained by MATLAB simulation.The contact between the tool and workpiece is a periodic intermittent impact contact.The simple mechanics model of cutting honeycomb composite with the straight blade cutter and the disc cutter was established.Using the principle of sliding shear to explain the process of ultrasonic assisted cutting,it can separate the material easily,reduce cutting force,improve the surface quality,which reflected the ultrasonic assisted cutting processing advantages.2.In the existing CNC machining center in the laboratory,a set of work fixture for cutting Nomex honeycomb composite was designed and improved.The ultrasonic assisted cutting test acoustic system was construct.Single-factor,orthogonal test of straight blade cutter and single-factor of the disc cutter were designed.The ultrasonic-assisted cutting and traditional cutting of the two kinds of tools were compared respectively.3.The influence degree of each process parameter on the cutting force of the three directions,the change of the machining surface quality with the cutting rake angle of the cutting tool,and the changing law of the cutting force with the rake angle of the cutter,the tool swing angle,the tool amplitude and the feed speed are studied.The variation of the machined surface quality with the tool rake angle and the variation of the cutting force with the straight blade cutter rake angle,tool swing angle,tool amplitude and feed rate were studied.The research summarizes the variation of disc cutter cutting force and machining surface quality with feed speed,tool rotation speed,cutting depth and tool swing angle.The experimental results show that the tool rake angle has the greatest influence on the cutting force;the ultrasonic assisted cutting force is less than the ordinary cutting force,no matter the straight blade cutter or the disc cutter cutting the NOMEX honeycomb composites,which effectively verifies the correctness of the ultrasonic cutting mechanics model.Compared with ordinary cutting surface,the surface of ultrasonic assisted cutting has the advantages of low burr rate,smooth incision and small deformation of honeycomb wall,which fully demonstrates the superiority of ultrasonic assisted cutting.The experimental results provide a reference basis for the reasonable selection of the process parameters of ultrasonic assisted cutting Nomex honeycomb composites. |
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