Research On Milling Force In Ultrasonic Assisted Machining C/C Composites

Carbon / carbon composites have high thermal stability and impact resistance,mainly used in the manufacture of high-temperature aerospace-related structural components,such as missile head cap,the engine nozzle and other key parts.But because of the material anisotropy,low interlayer shear strength and other properties,parts manufacturing with poor machinability,material stratification,fiber extraction and other defects,it is a typical difficult to process materials.At present,the aero-engine manufacturing technology can't meet the needs of the development of the new generation aero engine for high precision manufacturing technology of carbon / carbon composites.The ultrasonic assisted machining technology has a significant advantage in reducing the cutting force and improving the surface quality of the workpiece,as an effective method for the processing of difficult materials,the milling force of ultrasonic milling of carbon / carbon composites was studied.The research is as follows:The microstructures of carbon / carbon composites were characterized by SEM and VHX-2000,and the constitutive model of carbon / carbon composites was established.According to the macroscopic properties of the material,the force required for the fracture of the composite element is calculated.The trajectory model of cutting edge during ultrasonic vibration milling is established,and the mechanism of ultrasonic milling of carbon / carbon composites is described.Compared with the ordinary milling,ultrasonic vibration machining is the application of high frequency vibration energy on the tool,changing the size and the direction of the cutting edge,so that ultrasonic vibration milling more easily cut off the carbon fiber,the material removal,processing efficiency higher.The milling model of carbon / carbon composites and the model of vertical milling cutter are established.The milling force of ultrasonic vibration assisted carbon / carbon composites was modeled by the theory of bevel cutting,equivalent plane and two-dimensional orthogonal machining circle,and the orthogonal test is carried out under the conditions of the conventional milling and ultrasonic vibration milling.The results show that,compared with the ordinary milling carbon / carbon composites,the ultrasonic vibration milling can effectively reduce the cutting force in the milling process;the milling force in the ultrasonic milling process is changed periodically with the change of the tool rotation angle ?,the milling force of x direction and y direction with a change in one cycle is decreased first and then increased,and the milling force in z direction with a change in one cycle is increased first and then decreased.The surface microscopic morphology of carbon / carbon composites for ultrasonic milling were analyzed.In the case of ultrasonic vibration milling,due to the high frequency vibration applied to the milling cutter,the high frequency vibration of the material is caused,resulting in stress concentration on the carbon fiber,then the material is easy to mash,reduce the milling force in milling,improve the processing surface quality.Compared with ordinary milling,ultrasonic vibration milling will lead to carbon fiber stress concentration,easy cutting,and the chip size is smaller and fine.