Regenerative Chatter Monitoring And Ultrasonic Vibration Cutting Suppression Based On Time La

With the development of machining technology,titanium alloy materials are more widely used in aerospace and other fields.Due to the characteristics of titanium alloy such as low heat conductivity and severe work hardening,chatter is easy to occur during the cutting process.The tool will leave irregular chatter lines on the workpiece surface with harsh noise,which will affect production efficiency and processing quality.Chatter poses great harm to workpieces,cutting tools,and machine equipment,and the development of detection and control technologies for cutting chatter is crucial for machining titanium alloys.Firstly,the mechanism of regenerative chatter generated during external circular cutting of TC4 titanium alloy is studied,and a regenerative chatter kinetic model with the tool system as the main vibration system is established,and the kinetic parameters are identified experimentally and stability leaflet diagrams are drawn.In order to study the effect of time delay on chattering,a time delay-backlash stability limit leaflet diagram is drawn by introducing the time delay factor,and cutting simulations and experiments are carried out for different time delays.The results show that when cutting in the non-stable region,reducing the time delay can reduce the vibration generated by regenerative cutting,but the spindle speed increases,the vibration generated by spindle rotation will become the main vibration,at T=0.17 s,the vibration generated by regenerative effect decreases,the vibration of spindle rotation is smaller,and the cutting effect state is the most stable.In the stability region,the main source of vibration displacement is the self-excited vibration of the machine tool,and as the time delay decreases and the spindle speed increases,the self-excited vibration during cutting becomes larger,and the fluctuation range of the tool tip displacement time series graph during cutting increases.Secondly,based on the different characteristics of cutting during chattering outbreak and conventional cutting,a feature extraction method based on wavelet node energy is proposed,using three-layer wavelet transform first,sixth and seventh frequency bands and time domain signal polar difference and variance to compose feature vectors,and using support vector machine for pattern recognition.The chattering monitoring classifier was trained with a recognition speed of 3700 obs/sec and a comprehensive recognition accuracy of 91.6%.Again,for the regenerative chatter phenomenon generated when cutting TC4 titanium alloy,ultrasonic vibration cutting technology is adopted to suppress it.A two-dimensional cutting finite element model was established using ABAQUS to simulate conventional cutting and radial and tangential ultrasonic vibration cutting with different amplitudes,and the optimal ultrasonic vibration cutting scheme was selected for testing based on the simulation results to study the effect of ultrasonic vibration cutting on the vibration signal and surface structure of the machined surface during cutting.The results show that: the advantage of radial ultrasonic vibration cutting at an amplitude of 10 μm is obvious,the maximum Mises stress is reduced by 6%,and the average main cutting forces is reduced by 11%.The radial ultrasonic vibration cutting reduces the vibration generated by the spindle rotation by about 24% and the vibration at the intrinsic frequency by about 32%.Finally,in order to verify the effect of cutting chatter monitoring system with ultrasonic vibration system on chatter suppression,the cutting TC4 titanium alloy chatter monitoring and suppression test was designed.According to the study of chattering mechanism,the limit prediction system of external cutting chattering stability is developed,and suitable cutting parameters are selected to excite chattering by changing the time delay.Improve the chatter monitoring system,add ultrasonic vibration cutting to the training set,retrain the classifier,and improve the comprehensive correct rate of chatter recognition to 93.3%.A cutting test platform was established to identify the occurrence of chatter using the chatter monitoring system and suppress chatter with ultrasonic vibration.The results showed that the chatter recognition was basically correct except for a few error points when chatter was about to occur.Ultrasonic vibration cutting can effectively suppress the chatter caused by time delay change and improve the surface quality.