Research On Ultrasonic Vibration Assisted Drilling Technology For Carbon Fiber Composite/aluminum Alloy Laminated Components

With the rapid development of aviation and aerospace industry in China,carbon fiber reinforced plastic(CFRP)are more and more widely used for their superior material properties.However,CFRP has low interlayer strength and poor thermal conductivity.In conventional machining CFRP process,it is difficult to achieve high-efficient and high-quality machining,especially CFRP parts stacked with metal materials.Therefore,ultrasonic vibration assisted drilling(UVAD)technology is introduced to improve the drilling quality of CFRP/Al alloy stacks.The basic theory and the feasibility of UVAD on CFRP/Al alloy stacks are studied through the research of thrust force,drilling temperature and drilling quality.The work conducted in this paper is as follows:(1)This paper presents a mathematical model for thrust force in UVAD of CFRP/Al alloy stacks.First,the dynamic uncut chip thickness and average uncut chip thickness are obtained based on studying the characteristics of UVAD.Besides,the thrust force of the cutting lip and the chisel edge are calculated combining orthogonal cutting model and Hertz contact theory.Because functions of the cutting lip and the chisel edge in the drilling are different.Afterwards,a mathematical model is proposed to predict the thrust force in UVAD of CFRP.Pilot experiments are carried out to validate the rationality and effectiveness of the model.The results show that the experimental values and theoretical values have similar trends.(2)Based on the study of drilling temperature theory and the analysis of drilling process,the mechanism of heat generation and transmission during drilling is expounded.In addition,the drilling temperature measurement experiment was designed and carried out.The interaction of the two materials in terms of drilling temperature was analyzed.The experimental results show that UVAD slightly increases the drilling temperature of CFRP/Al alloy stacks,which is not enough to cause thermal damage of the material.(3)The experimental research on the drilling quality in UVAD of CFRP/Al alloy stacks was carried out by using orthogonal experiment design method.Then the mechanism of chip formation and delamination are studied in UVAD of CFRP/Al.And the orthogonal experiments are designed for analyzing the effects of both vibration parameters and cutting parameters on the drilling performance of hole roughness,burr length and height.The results show that ultrasonic vibration is beneficial to fracture the chip and avoid the generation of continuous chip.Besides,it can improves the roughness of the hole,reduce the delamination of CFRP and the size of burr length and height.