| Carbon fiber reinforced composite(CFRP)and titanium alloy are more and more widely used in the aerospace field based on their special properties.Because both of them are difficult to machine materials and the properties of the two materials are greatly different,there are problems such as poor machining quality and short tool life in the integrated drilling process of CFRP/titanium alloy laminated structure.According to the advantages of ultrasonic vibration drilling and low frequency vibration drilling,this paper puts forward the processing method of high and low frequency compound vibration drilling.A kind of integrated high and low frequency compound vibration drilling device is developed and the drilling experiment is carried out.Based on the kinematic model of high and low frequency compound vibration drilling,the overall design scheme of high and low frequency compound vibration drilling device is determined.The low-frequency system mainly includes the double Sinusoidal end cam,the slider mechanism,the ring flexure hinge and the fixed part.The high-frequency system mainly consists of ultrasonic power supply,wireless transmission device,transducer and horn.The main structure of low-frequency vibration system of the device was designed by chip breaking theory,elastic mechanics theory and mechanical vibration theory.The high-frequency(longitudinal-torsional ultrasonic)vibration system of the device was designed by theoretical calculation of the frequency equation of the integrated horn with spiral groove.The theoretical design and strength check of the main connecting parts are carried out by material mechanics.On the basis of the theoretical analysis,the finite element simulation and test of the low frequency system and the high frequency system structure of the high and low frequency compound vibration drilling device are carried out.Considering its working performance and service life,the specific design size of the device is determined.The vibration performance of the high and low frequency compound vibration drilling device after machining and assembling is tested.The results show that the device can be easily mounted and dismounted with the machine tool spindle,and can achieve independent and compound vibration of ultrasonic and low frequency.The vibration performance of the device is stable and reliable,which can meet the processing requirementsThe drilling experiment of CFRP/titanium alloy laminated structure was carried out by using the developed high and low frequency compound vibration drilling device.The drilling force,drilling temperature,titanium alloy chip morphology and the hole processing quality of CFRP are analyzed and compared under four drilling modes:conventional drilling,ultrasonic vibration drilling,low frequency vibration drilling and high and low frequency compound vibration drilling.The results show that: 1.Compared with conventional drilling,whether it is drilling CFRP or titanium alloy,vibration-assisted drilling all reduce the average drilling axial force to a certain extent,but increase the peak value of the axial force.2.When drilling titanium alloy,compared with conventional drilling,the mode of high and low frequency compound vibration drilling has the most significant effect on reducing cutting temperature.3.The titanium alloy chips in the low frequency vibration drilling and the high and low frequency compound vibration drilling are discontinuous C-shaped chips.The chip size of the high and low frequency compound vibration drilling is smaller than that of the low frequency vibration drilling.4.The overall tearing factor at the entrance of CFRP is the smallest in the mode of high and low frequency compound vibration drilling. |
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