Study On Finite Element Simulation Of Ultrasonic Vibration Metal Cutting

Titanium alloy is widely used in aerospace and other fields for the low density,high specific strength,high heat strength.However,the deformation coefficient of titanium alloy is small,so is the coefficient of thermal conductivity while the chemical properties are very large which can lead to the very high temperature in the traditional titanium alloy cutting.Thus the fatigue strength of materials is getting smaller,and the workpiece may deformed and the material sticks on the tool which can greatly reduce the service life of the tool.Titanium alloy is kind of difficult-to-machine material.In order to improve the titanium alloy in the processing of the above problems,improve the efficiency of titanium alloy processing and reduce tool wear,this study introduced the ultrasonic vibration cutting.The ultrasonic vibration cutting technology realizes the periodic contact between the tool and the workpiece by applying the high frequency and small amplitude vibration on the tool.Thus reducing the cutting temperature and cutting force,weaken the sticky phenomenon,restraining the formation of the built-up edge and improving the surface quality and cutting efficiency.First of all,introduce the basic theory of ultrasonic vibration cutting metal,including ultrasonic vibration cutting mechanism,classification and kinematic characteristics.Expounds the ideas of the finite element analysis and solving steps,and choose the material model,the heat conduction model,friction model,separation criterion and material fracture criterion according to the actual processing.Secondly,the Lagrange Euler finite element method(Arbitrary Lagrange-Euler,ALE)is used to establish a two-dimensional simulation model of titanium alloy cutting,and the simulation of metal cutting under ultrasonic vibration conditions is carried out.Selected Johnson-Cook material constitutive model,modified Kulun friction model and physicalgeometry separation criterion for simulation.The effects of cutting speed and back engagement of the cutting edge on cutting force,stress field,strain field and temperature field in cutting area are discussed and verified by experiments.The results show that,at the middle speed stage,the built-up edge will appear at the front of the tool,and with the increase of the velocity,the cutting force will decrease and increase with the formation and disappearance of the built-up edge.As the speed increases,the cutting force decreases gradually.The cutting force increases with the increase of the back engagement of the cutting edge.The cutting temperature increases with the increase of cutting speed and the back engagement of the cutting edge.The effect of cutting speed on temperature is more significant than the back engagement of the cutting edge.Finally,the simulation of unidirectional ultrasonic vibration cutting and elliptical ultrasonic vibration cutting of titanium alloy was carried out and compared with ordinary titanium alloy cutting process.The results show that ultrasonic vibration cutting has obvious advantages over ordinary cutting in reducing cutting force and stress,reducing cutting temperature and inhibiting the formation of scraps.And with the increase of amplitude and frequency,cutting force and cutting temperature is further reduced.Therefore,the ultrasonic vibration plays a positive role in improving the machined surface quality,prolonging the service life of the tool and improving the stability of the system.The advantage of elliptical ultrasonic vibration cutting is more obvious than that of unidirectional ultrasonic vibration cutting.