Longitudinal-torsional Resonance Ultrasonic Generator Design And Simulation Research On Auxiliary Milling Process

Because the hard,brittle and difficult to machine materials have excellent properties like high temperature resistance,oxidation resistance and corrosion resistance,they are suitable for many advanced scientific and technological fields such as aviation,aerospace,and ship building,weak rigidity and large-scale mechanical structures including thinwalled parts,elongated shafts,deep and small holes play a crucial role in these fields.The traditional mechanical processing method has the problems of single energy,severe tool wear,and sub-damage on the workpiece surface when processing hard and brittle materials.Processing weak rigidity mechanical structures is prone to instability,and processing errors sometimes is out of control,which cannot meet the processing requirements.This article focuses on the longitudinal torsional ultrasonic milling cutter with three-dimensional vibration trajectory,and also studies the hardware structure and frequency tracking algorithm of the ultrasonic generator.At the same time,based on the Abaqus software,a three-dimensional finite element model of longitudinal torsional ultrasonic milling is built to analyze how different cutting parameters influence cutting force,cutting temperature and stress distribution on workpiece surface during longitudinal torsional milling processes.In order to improve manual frequency adjustment of traditional ultrasonic generators and cannot accurately track the resonant frequency of the transducer in real time that results in unstable processing.The hardware structure of ultrasonic generator is firstly designed.This article uses the MOSFET full-bridge inverter circuit,AD9850 direct digital synthesis chip,dead zone circuit,IR2110 drive circuit to form a high-frequency inverter module to achieve the high-frequency output of the ultrasonic generator and the frequency adjustment of the processing process.To realize the function of frequency search and frequency tracking in the whole process,the transducer loop current effective value detection circuit,voltage and current phase difference detection circuit and signal processing circuit are designed.For achieving constant amplitude control,a Buck chopper and an uncontrolled full-bridge rectifier bridge stack are used to form a power regulation rectifier module.In order to improve the frequency tracking accuracy of the ultrasonic generator and speed up the output response speed,this paper builds a mathematical model of the ultrasonic vibration system based on the Matlab/Simulink software,and uses the trial and error method to set the traditional PID control parameters.The simulation of PID control algorithm with voltage and current phase difference as feedback signals are completed.Two-dimensional fuzzy PI controller is designed,and the simulation of phase difference fuzzy PI control algorithm is completed.The results show that the fuzzy PI control has better output response characteristic.Finally,according to the impedance characteristics of longitudinal torsion resonant transducer and the simulation results,global frequency search algorithm,frequency tracking algorithm and constant amplitude control algorithm are compiled.Based on Abaqus software to carry out three-dimensional finite element simulation of the longitudinal torsional ultrasonic milling process In order to ensure that the longitudinal torsional ultrasonic vibration milling process proceeds steadily and obtains ideal workpiece quality.At first,a three-dimensional simplified model of the workpiece and the milling cutter is established.The cutting force,cutting temperature and stress distribution of the workpiece under three cutting methods of longitudinal torsional resonance ultrasonic milling,pure longitudinal vibration ultrasonic milling and traditional milling are completed according to the model.Secondly,single-variable analysis that are mainly related to ultrasonic vibration amplitude,spindle speed and radial cutting depth for longitudinal torsional ultrasonic milling is completed to obtain the optimal machining conditions.The finite element simulation results can not only be used as a reference for the longitudinal torsional resonance ultrasonic milling test,but also provide a theoretical basis for the subsequent researches on longitudinal torsional resonance cutting.