Research On Ultrasonic Mechanism For Ultrasonic Assisted Magnetic Abrasive Finishing Of Titanium Alloy

Titanium alloys have excellent physical and chemical properties,so have been widely used in various industries.Especially used in aerospace field,the complex surface of complicated structural parts are required to finish precisely.However,because of characteristics of high strength,high viscosity,it is difficult to be processed.Due to weak rigidity,the work-piece is easily deformed.In addition,machining quality and efficiency are put forward high requirements.Aiming at these problems,ultrasonic assisted magnetic abrasive finishing(UAMAF)has great advantages.At present,the mechanism of magnetic abrasive finishing(MAF)applied to axial ultrasonic vibration has not been revealed.In this paper,the movement process and force of magnetic abrasive are analyzed.The test-bed of UAMAF is set up.The variation of cutting force,finishing performance of magnetic abrasive and surface integrity are discussed.The ultrasonic mechanism of ultrasonic assisted abrasive finishing is revealed.The main research content and results are summarized as follows:(1)According to the requirements and characteristics of UAMAF,the main circuit and the frequency tracking circuit were set up.The component modules of ultrasonic power were designed,and the prototype preparation of ultrasonic power was completed.An ultrasonic vibration system was designed,which includes energy-transmission system,piezoelectric transducer and ultrasonic horn.Finally,test-bed of UAMAF was set up by integrating ultrasonic vibration system on a three axis CNC engraving machine.(2)A comparative study of UAMAF and common MAF of titanium alloy was conducted to research respectively variation of the cutting force and finishing performance of magnetic abrasive.The influence of processing parameters on cutting force was obtained in two processing methods through a single factor experiment,including ultrasonic amplitude,machining gap,feed rate,and spindle speed.The results indicated that the cutting force could be increased by 2-4 times in the same processing parameters.If the ultrasonic amplitude increases,the cutting force increases linearly.A comparative study of the changing trend of density and distribution of diamond abrasives on the surface of magnetic abrasive with processing time was conducted.It could be seen that impact and cavitation of ultrasonic energy speeded up the rolling and replacement rate of the abrasive,effectively improved the overall utilization of abrasive,(3)A linear scanning comparative experiment study of UAMAF and common MAF of Titanium alloy was conducted.The variation of surface integrity was discussed in two processing methods,including surface roughness,surface morphology,micro hardness and surface residual stress.The difference between the processing microscopic characteristics and the formation mechanism of the surface material was analyzed,and the ultrasonic mechanism was revealed.The results indicated that ultrasonic assisted magnetic abrasive finishing surface roughness could be reduced by 60 percent at most,and reached 74.6nm.The processing efficiency was increased by 4 times.Surface morphology was more uniform.The surface grain was refined.Surface micro hardness was increased from 392.2HV to 450.6HV,and surface residual stress was changed from +68Mpa to-34.1Mpa.