Study On Rotary Ultrasonic Machining Of Carbon Fiber Reinforced Plastics

Carbon fiber reinforced plastic(CFRP)has a variety of attractive properties,including high stiffness-to-weight ratio;excellent wear and corrosion resistance;and high designability.Due to these superior properties,CFRP have been widely used in aerospace and commercial aircraft,automotive,sports good.Traditional processing methods on CFRP had many drawbacks including high tool wear,severe delamination,bad surface roughness,because of its physical properties and special pavement structure.Rotary ultrasonic machining(RUM)is a hybrid machining methods,which effectively reduces the cutting force and tool wear,and gradually becomes a hot research topic in machining of CFRP composite materials.Some developed countries abroad have developed a RUM machine,but research on such equipment is still less in our country.At present,common rotary ultrasonic machining equipment is mostly using brush-contact power supply,there are many drawbacks,such as brush wear serious,lost steps,and poor versatility.In order to solve these problems,this paper has done the following work:Firstly,a quarter-wave ultrasonic transducer and a horn are designed and fabricated.The transducer is simulated by Abaqus software to solve the resonant frequency,the nodal position and the end amplitude of the ultrasonic transducer.The influence of different size tool and different installation position on the resonant frequency of ultrasonic vibrator is analyzed.It is found that the resonant frequency of the ultrasonic vibrator decreases with the increase of the tool diameter,but the influence on the position of the joint is negligible.For the different mounting position of the tool,the longer the clamping length is,the lower the resonant frequency of the transducer.Secondly,the inductively coupled power transfer(ICPT)device of RUM is designed,the core and coil structure parameter design is completed.The device electromagnetic model is simulated by Maxwell software.The simulation results show that the designed core and coil meet the requirements of the ultrasonic energy of the ultrasonic transducer.In the process,the core air gap should be about 0.5mm,and the axial deviation is within 1mm to ensure that the transformer has high transmission efficiency.Thirdly,the ultrasonic transducer and the ICPT device are integrated on the standard BT40 tool holder,and the ultrasonic machining on the ordinary machine toolis realized.The performance of the inductively coupled power transfer device of rotary ultrasonic machining device and the compensation circuit is tested.The results show that the resonant frequency of the ultrasonic oscillator is 22.543 KHz and amplitude is 23.89?m when ultrasonic power is 30 W.The coupling coefficient of the ICPT device is 0.82 and transfer efficiency is 57%,when the air gap is 0.5mm;the coupling coefficient is 0.94 and transmission efficiency is 68%,when the axial deviation is 0.5mm.the oscillator amplitude has greatly improved after using the original-secondary series capacitor compensation,the maximum lifting ratio is 63%.Finally,a RUM test platform with ICPT device is built on the CNC machine tool.The axial and radial runout of the tool are tested.Comparisons between common drilling and RUM drilling on CFRP plate are conducted to study the mechanism of burr and tearing defects at the entrance and exit of the hole.The result shows that RUM drilling effectively reduces the occurrence of burrs and has better aperture consistency.The burrs at the exit of the hole are closely related to the cutting angle,mostly in areas where the cutting angle is acute.