The development of science and technology in the world has promoted the continuous progress of the manufacturing industry,and the processing requirements for the manufacturing industry are also getting higher and higher,especially for the aviation industry,which is not only reflected in the processing accuracy of parts,but also has higher requirements for the service life of parts.Aluminum alloy al7050-T7451 is widely used in aircraft manufacturing due to its high strength and easy processing.Milling,as a common processing method for subtractive manufacturing,residual stress will be generated on the surface of the processed aluminum alloy.As an important indicator to judge the quality of the surface,residual stress can effectively affect the fatigue strength,corrosion resistance and creep life of parts.Therefore,it is very important to study the distribution of residual stress caused by cutting on the surface of the material.In this paper,the surface quality of ultrasonic longitudinal torsional composite vibrating side-milled aluminum alloy mainly based on residual stress is studied.1.The traditional milling,unidirectional longitudinal vibration milling and ultrasonic longitudinal-torsional coupled vibration cutting edge paths and their cutting characteristics were studied.The ratio of chip separation time to period in a vibration period,namely duty cycle,is derived from the ultrasonic longitudinal-torsional coupled vibration track equation.The influence of the change of the spindle speed,helix angle and vibration frequency on the duty cycle were analyzed.2.Firstly,the theoretical model of ultrasonic longitudinal torsional milling residual stress of the traditional milling cutter and the variable helix milling cutter was established.Subsequently,based on the CEL grid technology,the ultrasonic elliptical vibration orthogonal cutting model was established,and the influence of ordinary cutting and elliptical vibration milling on milling force and residual stress were compared,and the influence of cutting parameters,vibration amplitude,tool geometry angle and cutting fluid on residual stress in vibration machining were studied.In order to realistically simulate the difference between variable helix milling cutter and common milling cutter,a three-dimensional vibration milling model was established.The simulation results show that the surface after machining with variable spiral cutter has larger surface residual stress.3.An ultrasonic machining test platform was set up to study the effect of longitudinal torsional coupled vibration side milling on the surface quality of aluminum alloy with variable helix milling cutter.Comparative experiments show that compared with ordinary milling cutters,the surface of the variable helix milling cutter after milling has lower surface roughness values.Subsequently,the orthogonal experiment and single factor experiment of ultrasonic machining with variable spiral milling cutter were carried out.The orthogonal test shows that the factors that have great influence on the surface roughness of the workpiece are the feed per tooth and the ultrasonic amplitude,and the factors that have great influence on the cutting force are the feed per tooth and the cutting depth.Finally,through a single factor test,the influence of cutting parameters on cutting force and surface roughness was analyzed in depth. |