Study On Properties And Numerical Simulation Of Aluminum/Steel Continuous Drive Friction Welding In Conical Joint

The aluminum/steel composite structure makes full use of light weight,good electrical and thermal conductivity of aluminum and steel's high strength,high rigidity,creep resistance and other advantages,and is widely used in automotive manufacturing,energy,aerospace and other fields.As a high-quality solid-state bonding technology,continuous drive friction welding has significant advantages in the advanced bonding of dissimilar metals;However,in the welding process,due to the different flow characteristics of base metal and radial friction torque distribution,the oxides and impurities on the interface are difficult to discharge,and the uneven distribution of heat generation power and IMCs on the interface,will adversely affect the performance of joint.The structural design of the joint is an important technological measure for continuous drive friction welding,which plays a significant role in improving the inhomogeneity of the interface IMCs and improving the mechanical properties of the joint.In this paper,1060 pure aluminum and Q235 low carbon steel rod as the research object,and designs the taper angle?of 5°,10°,15°,20°,and 25°on the end face of the steel rod to carry out welding experiments.The influence of different taper size on the macroscopic forming and mechanical properties of the joint was analyzed,and the change trend of interfacial friction torque,energy input and characteristic point temperature is obtained.In order to understand the plastic metal forming and temperature distribution in the welding process,this paper uses the ABAQUS finite element software to establish a thermo-mechanical coupling three-dimensional model of the welding process,and analyzed the influence rules of the taper size on the joint forming,the plastic metal forming and evolution,the joint temperature field and the stress and strain field.The main research content and results are as follows:The dynamic torque and interface temperature of the welding process were calculated by stator voltage-current of main motor method and thermocouple method.With the increase of taper angle,the initial peak torque decreases,the steady-state torque and the post-peak torque first increase and then decrease.There are three peaks in the torque curve of the 25°joint,which reflects the instability of the contact surface.In the first stage,the proportion of energy input in the total energy input increases gradually;with the increase of taper angle,the initial friction position moves,and the platform region disappears at 15°in the sliding friction stage.The conical structure makes the concentrated area of heat generation at the interface move.Before 15°,the peak temperature of the joint is at the 2/3R position,and after 20°,it is at the 1/3R position.The taper Angle increases and the overall temperature of the joint decreases,the temperature curve of the joint at 10°and 15°tends to be flat.Through the examination of the mechanical properties of the welded joints,it is found that the joints with a taper angle?=15°have better comprehensive mechanical properties.The mechanical properties of the interface in different areas are different under different taper degrees.The strength of the joint at 10°and 15°tends to change gently along the radius direction.At 15°,the average tensile strength is 77.5MPa,which is 96%of the aluminum base material.The maximum impact energy of the samples in the 0?1/2R region is 15.2J/cm~2 at 20°,and the impact energy of the samples in the 1/2R region decreases.The deformation bearing capacity of 15°specimen is obviously better than that of other degrees.The conical structure design can play a role in the uniform radial mechanical properties of different degrees.The CEL model was used to complete the numerical simulation of aluminum/steel welding process,and the accuracy of the model was verified by comparing with the experimental data.As the degree of taper increases,the stress at the same time also increases.Under the taper structure,the axial friction force is decomposed into normal pressure and tangential pressure,which makes the local stress increase and the stress is concentrated in a small area.The larger the taper is,the more obvious this phenomenon is.At 0°,the plastic state expands from both sides to the center,while in the taper structure,the plastic region expands from the center to both sides.The light gray layer rings with different widths and slight protrusion were produced at the joint interface,and the 15°joint was torn obviously.With the increase of the degree of taper,the heat production concentration area of the interface moves toward the center,and is located at 0.69R at 0°and 0.55R at 25°.As the degree of taper increases,the width of the high temperature region narrows,which is located at 0.45R at 0°and reduced to0.20R at 25°.The position and width of the plastic ring are in good agreement with the calculated temperature field.