Design Of Ultrasonic Assisted Cutting Vibration System For Machining Of Carbon Fiber Composites

Carbon fiber reinforced composites have excellent properties and are widely used in aerospace and other fields.Traditional machining methods can not meet the requirements of high-quality processing.The introduction of ultrasonic vibration-assisted cutting method based on traditional machining methods can achieve high-quality and high-efficiency processing of carbon fiber composites.However,in actual processing,it is found that under high-frequency or large-amplitude ultrasonic vibration,due to the existence of stress concentration problem,the whole carbide tool rod is liable to fracture or fragmentation at the joint of the tool rod and the ultrasonic horn.In view of the above problems,this paper proposed a scheme to solve the stress concentration problem at the joint of the tool bar and the ultrasonic horn by using the modification technology,studied the modification design method of the joint,and designed a set of ultrasonic-assisted cutting vibration system of carbon fiber composites using the modification technology.The specific research contents and results are as follows:(1)According to the processing quality requirements of carbon fiber composites,the design requirements of ultrasonic assisted cutting vibration system were analyzed,and the design scheme of using half wave length for ultrasonic vibration system was determined.After analyzed,the concrete structure forms of the ultrasonic horn and transducer were determined,and the appropriate design methods were selected to design the ultrasonic horn and transducer in detail.The finite element simulation of the ultrasonic vibration system was carried out.The modal analysis verified the correctness of the design method of the ultrasonic horn and the harmonic response analysis verified that the longitudinal resonance of the ultrasonic vibration system can occurred near the design frequency of 30 kHz.(2)According to the requirement of the connection performance between tool and ultrasonic horn,the advantages and disadvantages of common connection methods between tool and horn were compared and analyzed,and the optimum connection method using thermal interference connection was determined.The design parameters for the interference connection between tool and ultrasonic horn was carried out.The tolerance of the interference connection between tool rod and ultrasonic horn is ?6(S6/h5).The heating temperature needed for the hot assembly is 410?.The reliability of the heating temperature was verified.The finite element model of interference connection between tool and ultrasonic horn was established,and the validity was verified.The stress distribution of tool rod and ultrasonic horn at the joint was analyzed.The stress at the flat part is about 240 MPa,while the stress concentration is as high as 955 MPa.(3)The modification design requirements of interference connection between tool and ultrasonic horn was analyzed,and the modification design scheme of the connecting part between tool and ultrasonic horn was determined.The corresponding modification curve equations of the whole arc,arc-straight line and logarithmic curve modification methods were deduced,and the finite element analysis model after modification was established.The stress distribution of the tool rod at the joint of the tool rod after each modification method was studied with the variation of modification parameters.After further analysis and optimization of the above modification methods,the optimal modification method was finally determined,which combines the 6-micron modification of the full arc bus with the logarithmic bus modification with the load optimization coefficient of 0.2.