The Mechanism And Surface Quality Study Of Radial Ultrasonic Vibration Milling Of Titanium Alloy

Titanium alloy is a kind of materials that commonly used in aviation and aerospacefields.It has a variety of advantages performance, such as small density, hightemperature resistant, and high strength. However, there are some disadvantages at thesame time.The poor thermal conductivity, low elastic modulus and the high chemicalactivity, which makes it become a type of difficult-to-machine materials. Nowadaysmilling is the most commonly used method in the titanium alloy processing. Ordinarymilling titanium alloy has large cutting force, high cutting temperature and severelycutting tool wear, which leads to low process stability and control-less machiningquality. Ultrasonic vibration aided cutting introduced the ultrasonic signal to ordinarycutting. an impressive body of literature have shown that ultrasonic vibration turning,drilling and boring can reduce the cutting force, improve the processing quality.Butbecause of the complexity of the milling process, vibration milling study is less, andthey focus on the study of axial vibration mostly, radial ultrasonic vibration milling isstill in its initial stage.In order to explore the feasibility in ultrasonic vibration milling titanium alloyprocessing, this study is carried out based on the principle of ultrasonic vibration cutting.The research runs as follows:First, radial ultrasonic vibration milling titanium alloy experiment platform isdesigned and set up independently. Through the theoretical calculation and the modalanalysis, the size of workpiece and the resonance frequency are determined. Throughtheoretical calculation and the tip trajectory simulation, the kinematics mechanism ofvibration milling was studied. The cutting speed is less than the maximum vibrationvelocity, named vibration milling speed characteristics; Each tooth feeding less than2times of amplitude, called the vibration milling of feed characteristics. They are thevibration milling knife-crumbs necessary conditions of periodic separation.Secondly, ordinary and vibration milling experiments are carried out guided by thetwo necessary conditions. The single factor experiments content the change rules ofcutting force by cutting speed, feed, cutting depth and the vibration amplitude.Changing rule curves showed that the radial ultrasonic vibration milling can decreasethe average cutting force within a certain scope, reduce volatility and increase thesystem stability, but for the different directions of the cutting force the degree is different. Overall data shows that within the knife-chip separation conditions, vibrationmilling increase relatively slowly and decrease the cutting force obviously; Outside ofthe knife-chip separation conditions, there is still a small improvement, but the degreebecome weak.After that, the surface roughness changing rules of vibration milling Ti-6Al-4V issummarized. The Ra surface roughness is studied through cutting experiment, contentsthe relationship to cutting speed, feed and cutting depth and the vibration amplitudechanges, and then explained the cause of the change.Finally, the workpiece and chip micro morphology changes is studied by scanningelectron microscopy. Artifacts SEM analysis shows that the radial ultrasonic vibrationmilling is mainly on the improvement of the surface roughness in scratches groovedlighter and more uniform and so on. Chips macro contrast shows that chip becomeshomogenize and scrawl along with the increase of amplitude. They are more likely toleave the cutting zone and not easy to wrap knife.Theoretical and experimental analysis proved that the ultrasonic vibration millingtitanium alloy can decrease the cutting force, reduce the surface roughness, is a kind ofpractical and feasible processing method.