Research On Characteristic Of Ultrasonic Assisted Milling On Titanium Alloy Sculptured Surfaces

Recently,with rapid development of high-end manufacturing,as a result of its advantages of high specific strength,extraordinary ability of corrosion resistance and excellent thermal stability and,titanium alloy is widely used in field of aerospace.Furthermore,heteromorphic surface and space sculptured surface exist in aero products widely.However,as a result of titanium alloy's disadvantage of weak thermal conductivity,high chemical activity and low elastic modulus,titanium alloy is a typical difficult-to-cut material.Therefore,it is urgently for manufacturing industry to find a method to enhance processing efficiency and machining precision in products of titanium alloy sculptured surface.In this thesis,a geometrical model of the ball-end mill based on axial position is presented,and the equation of cutting path of a certain point in cutter when the cutter is vibrated in different conditions is established.Instantaneous chip thickness is calculated according to cutting path,and substitute the chip thickness into model of mechanical linear micro-unit cutting force,and get a new cutting force model under the condition of longitudinal-torsional composite vibration.Longitudinal-torsional vibration horn is designed by manufacturing helical rectangular slots in body of longitudinal vibration horn.Orthogonal experiment is designed by controlling slots' quantity,helix angle and width.Using the part of modal analysis in ANSYS,the ratio of longitudinal and torsional amplitude in terminal output is calculated and impacts is acquired.The most optimal parameter of helical rectangular slots is gained in single factor experiment.Results show that helix angle is the most influential factor,and with the growth of helix angle,the ratio increase firstly and reach the maximum value when helix angle is 30°,and then the ratio decreased.As the horn is manufactured,an experimental platform of wireless longitudinal-torsional composite ultrasonic vibration is established.Based on theoretical analysis,an experiment on characteristic of ultrasonic assisted ball-end milling of titanium alloy sculpture surface is carried out on self-made experimental platform.Constant-curvature titanium specimen is chosen as the target of the experiment.An orthogonal experiment and four single factor experiments are arranged by picking the radium of the specimen,axial position of cutter,the amplitude of ultrasonic vibration,depth of cut and cutting speed as variable parameter.Data of cutting force and surface roughness is collected during and after the experiment,and machined surface and chip is examined.By analyzing these data,the influence of milling characteristic on process parameters and ultrasonic parameters.Research on experiment has verified the correctness of cutting force model,and shows that the radium of the specimen and axial position of cutter are the most influential factors on cutting force,and the amplitude of ultrasonic vibration and depth of cut are the least influential factors on cutting force.Furthermore,within certain amplitude,ultrasonic vibration assisted ballend milling of sculptured surface can improve surface quality and decrease surface roughness prominently.