Mechanism And Experimental Study Of Ultrasonic Vibration Assisted Milling For SiCp/Al Composites

SiCp/Al composites have been widely used in many fields such as aerospace,transportation and electronic information because of their high specific strength,high specific stiffness,high thermal conductivity and good impact resistance.Traditional mechanical processing is difficult to achieve high precision and high efficiency for this material.Ultrasonic vibration-assisted milling is widely used for machining hard and brittle materials by applying ultrasonic frequency vibration to the tool or the object to be machined to obtain high frequency intermittent cutting processing,which has great advantages in reducing cutting forces,reducing surface defect formation and improving surface quality.In this paper,the ultrasonic vibration-assisted milling technology is investigated with respect to the cutting process,cutting force,cutting temperature,surface microformation and defect formation mechanism of ultrasonic vibration-assisted cutting of SiCp/Al composites,and the influence of each machining parameter on the machining process force,temperature and surface quality in ultrasonic vibration-assisted milling processing is analyzed to obtain the optimal machining process and machining parameters.The main work is as follows.(1)The mathematical models of tool tip motion under two different cutting methods,ordinary milling and ultrasonic vibration-assisted milling,were established.Using ABAQUS finite element analysis software,an orthogonal cutting model based on SiCp/Al composite material with 68% volume fraction was established,and the effect on milling force and milling temperature was investigated by combining the simulation comparison experiments of normal milling and ultrasonic milling.The simulation results showed that the surface forms of SiCp/Al composites after machining included fracture and crushing,plastic removal,and flaking and cratering;the cutting stresses were transmitted along the distribution direction of SiC particles;ultrasonic milling could reduce the milling cutting force by 42.95% and milling temperature by 38.2% compared with normal milling.(2)A comparison experiment between ordinary milling and ultrasonic milling was carried out for SiCp/Al composite with 68% volume fraction to study the effects of different cutting parameters on cutting forces.By designing orthogonal experiments with parameters such as cutting speed,cutting amount and feed,an exponential model of the empirical equation of milling forces was established and extreme difference analysis was performed for each component of the milling forces.The experimental results show that when the spindle speed,feed rate and milling depth are increased,the milling forces of both normal milling and ultrasonic vibration-assisted milling increase,and the cutting depth has a greater effect on the cutting forces.Under the same milling parameters,the milling fractional forces in three directions of ultrasonic vibrationassisted milling are much lower than those of ordinary milling.After calculation,it is found that the cutting force can be significantly reduced by 33.96% using ultrasonic machining,which is the same as the result of 42.95% cutting force reduction in the simulation,and the average error between the simulation value and the test value is 8.99%less than 10%,which is within the acceptable range and verifies the conclusion of the simulation.(3)For SiCp/Al composites with 68% volume fraction,the temperature variation analysis study of ultrasonic and conventional milling was conducted to explore the mathematical relationship between machining parameters and cutting temperature by using single factor analysis method.The results show that ultrasonic vibration-assisted milling can significantly reduce the milling temperature,and when the spindle speed,feed rate and milling depth increase,the cutting temperature also increases accordingly.Among them,the effect of spindle speed is the most significant,followed by feed rate,while the effect of milling depth is the least.(4)For the ultrasonic vibration-assisted cutting surface quality study,typical 2D(Ra and Rz)and 3D(Sa and Sq)surface roughness parameters were selected to evaluate the effect of milling parameters on the surface quality,and the machining process parameters were improved by using the multi-objective machining parameter optimization method,which showed that compared with 2D parameters(Ra and Rz),3D parameters(Sa and Sq)could more accurately describe the surface quality.The most influential factor on Ra,Rz,Sa and Sq is the ultrasonic amplitude A,followed by the feed rate Vf.The optimal combination of process parameters is: ultrasonic amplitude of3 μm,spindle speed of 6000 r/min,milling depth of 0.03 mm and feed rate of 60 mm/min.The surface roughness Ra is 0.237 μm,Rz is 1.123 μm,Sa is 0.255μm and Sq 0.359μm.