| Carbon fiber reinforced silicon carbide ceramic matrix composite(C/SiC)is an aerospace-grade composite material with high temperature resistance,wear resistance,oxidation resistance and mechanical properties.It is processed by traditional processing technology,which can not meet the needs of today's aerospace and other fields due to poor process ability,low precision and high processing cost.Rotary ultrasonic vibration assisted machining technology is used to introduce rotary ultrasonic vibration into the milling of C/SiC composites,which can effectively reduce milling force,cutting heat,reduce tool loss and improve processing quality.This paper mainly completed the following work:Based on the inverse piezoelectric effect of piezoelectric ceramic,a longitudinal vibration type ultrasonic vibrator which can be used for rotary ultrasonic milling is designed according to the design theory of sandwich piezoelectric ultrasonic transducer.PZFlex simulation software is used to simulate and analyze the factors that affect the ultrasonic oscillator resonance frequency.The results show that the resonant frequency of the ultrasonic oscillator decreases with the increase of the effective length of the tool and the length of the transition cylinder,and increases with the length of the pre-tightening bolt and the depth of the back cover hole.According to the simulation results,the longitudinal vibration type ultrasonic vibrator was processed and the impedance analysis was carried out.The resonance frequencies of the longitudinal vibration type ultrasonic vibrator in the presence or absence of the tool and the chuck nut were 17.41 kHz and 18.71 kHz,respectively.In the simulation results,the resonant frequencies of the model are 18.4762 kHz and 19.312 kHz,and the error rates are5.7636% and 3.1428%,respectively.Based on the resonant frequency of the ultrasonic vibrator,the amplitude output of the ultrasonic vibrator with the chuck nut and the tool state is measured.The results show that the amplitude of the output of the vibrator is proportional to the voltage at 100 V,140 V and 200 V,And the longitudinal amplitude is 2.016 um when excited at 200 V,meet the requirements of the auxiliary ultrasonic vibration rotation milling,The feasibility of the design of the longitudinal vibration type ultrasonic vibrator is confirmed,which provides a reference for the optimization design of the longitudinal vibration type ultrasonic oscillator.Designing the clamping device of the longitudinal vibration type ultrasonicvibrator,the bridge plate and the spindle connection of the machine tool to realize the connection between the ultrasonic vibrator and the spindle of the machine tool;designing the power transmission device to supply power to the longitudinal vibration type ultrasonic vibrator;designing the protective casing and installing the bolt device,etc,establishing rotating ultrasonic vibration assisted milling system;based on the system using single factor experiment method and orthogonal test method,studied the cutting force and machining surface of C/SiC composite material during milling and milling in different milling parameters under traditional milling.The influence of mass and the results of rotary ultrasonic vibration assisted milling results show that compared with traditional milling,rotary ultrasonic vibration assisted milling reduces the cutting force during milling and improves the surface quality;traditional milling and rotation in ultrasonic vibration milling,the spindle speed increases with the cutting force to reduce the surface quality.As the feed speed and milling depth increase,the cutting force increases.the surface quality decreases.In the rotary ultrasonic milling test,the milling depth is the most important factor affecting the cutting force and surface roughness;but in the traditional milling test,the feed speed is followed by the milling depth.In the milling hole test,when the feed speed and milling pitch are large,the advantages of rotary ultrasonic milling are not obvious. |
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