| CFRP/titanium alloy laminated structure is widely used in aerospace and other fields based on its special properties.Because CFRP and titanium alloys are both difficult-to-machine materials and the properties of the two materials are greatly different,resulting in CFRP/titanium alloy laminated structure integrated hole making has poor processing quality and short tool life and so on.It is of great significance to drill CFRP/titanium alloy lamination structure with high efficiency and low damage to obtain high quality holes.Based on the advantages of ultrasonic vibration drilling and low-frequency vibration drilling,this paper puts forward the processing method of high and low frequency composite vibration drilling,and the axial force model of drilling is established and related experimental research is carried out.The kinematic models of low-frequency drilling,ultrasonic drilling and high-low frequency composite vibration drilling were established respectively,and their specific machining parameters and spatial motion trajectories under vibration parameters are analyzed.According to the two-dimensional expansion diagram of the tool space trajectory,the chip thickness of ordinary drilling and ultrasonic longitudinal vibrationlow frequency combined vibration drilling are analyzed and compared.The axial forces on the main cutting edge and the horizontal cutting edge are analyzed and calculated respectively,and the drilling force model of CFRP/titanium alloy laminated structure is established.The drilling experimental system of combined axial high and low frequency vibration is built,and the drilling parameters of combined axial high and low frequency vibration are determined by theoretical system analysis,reasonable selection of components of each part of the system,acoustic system detection and system vibration test,combined with the requirements of the test.The mechanical and thermal tests of CFRP/titanium alloy lamination structures were carried out respectively for conventional drilling,ultrasonic vibration drilling,low frequency vibration drilling and high-low-frequency composite vibration drilling.The results show that: 1.The average axial force of CFRP and titanium alloy does not change obviously with the increase of rotational speed,but increases with the increase of feed per revolution.2.In ultrasonic drilling,the mean axial force of CFRP and titanium alloy drilling decreases with the increase of ultrasonic amplitude.In low-frequency drilling,when the low-frequency frequency is less than 30 Hz,the average axial force of titanium alloy is smaller than that of titanium alloy under ordinary drilling,while the average axial force of CFRP is generally larger than that of titanium alloy under ordinary drilling,and it also increases with the increase of low-frequency frequency,but for both CFRP and titanium alloy,the instantaneous drilling axial force is increased.3.In high and low frequency compound vibration drilling,the average axial force of CFRP and titanium alloy varies with the low frequency frequency in the same way as that of low frequency drilling.When the low frequency frequency is determined,the average axial force of high and low frequency compound vibration drilling decreases compared with that of low frequency drilling.4.The highest temperature of low-frequency drilling and high-low-frequency composite drilling of titanium alloy is obviously lower than that of ordinary drilling and ultrasonic drilling.Ultrasonic drilling,low-frequency drilling and high-low-frequency composite drilling can reduce the drilling temperature to a certain extent,among which,the cooling percentage of low-frequency drilling is the largest.Finally,the hole making quality of CFRP/titanium alloy laminated structure drilled by four different machining methods is analyzed.The results show that:1.In ordinary drilling,the tearing area of CFRP inlet increases with the increase of feed per revolution and decreases with the increase of rotation speed.In ultrasonic and low-frequency drilling,the tearing area of CFRP inlet decreases with the increase of ultrasonic amplitude and increases with the increase of low-frequency frequency.2.when drilling CFRP/titanium alloy laminated structure with high and low frequency composite vibration,the chip breaking effect of titanium alloy is the best,the tear degree of CFRP inlet is the lowest,the quality of outlet is the best,the roughness value of hole wall is the minimum,and the quality of hole wall is the best. |
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