Research On Ultrasonic-assisted Multi-point Stretch-bending Forming Technology Of Aluminum Profiles

As the main material for lightweight structures,aluminum alloys are widely used in highspeed railway trains,aerospace,and automobile manufacturing due to their advantages of easy recycling,low density,and high stiffness.At present,many traditional two-dimensional stretch-bending aluminum profiles can no longer meet the needs of the industrial market.In this paper,a new type of forming process is proposed,that is,the ultrasonic-assisted multipoint stretch-bending process.The ultrasonic-assisted multi-point stretch-bending forming process is the product of the combination of ultrasonic vibration forming,stretch-bending forming,and flexible multi-point manufacturing concepts,which not only reduces the time and cost of planning,processing,and modulation of traditional stretch-bending dies but also improves the quality of the parts.Indentation,creases,and other local defects,to obtain highprecision,high-quality parts.The main research contents and conclusions of this paper are as follows:To explore the influence of the ultrasonic vibration process on traditional multi-point stretch-bending parts,the ultrasonic-assisted multi-point stretch-bending model of AA6082 aluminum alloy was established by ABAQUS finite element software.The material parameters,ultrasonic process parameters,tensile and bending trajectories,constitutive equations,meshing,element types,and boundary conditions were determined.In this way,the ultrasonic-assisted multi-point stretch-bending forming process of aluminum profiles is simulated.In this paper,the drawing and bending parts of the traditional roll-type multi-point mold and the ultrasonic-assisted multi-point mold are compared,and it is found that the thicknessdirection stress,thickness-direction strain,height thinning and thickness thinning change of the forming results of the two are consistent,but the ultrasonic-assisted local stress and local strain of the multi-point mold parts were lower,and the average thickness reduction rate of the part thickness was found to be lower for the ultrasonic-assisted multi-point mold parts.The ultrasonic vibration-assisted forming process can effectively reduce the local stress concentration and local deformation of the profile,and effectively suppress the thinning defect of the profile.In this paper,the effects of elastic modulus,friction coefficient,ultrasonic vibration frequency,and ultrasonic amplitude on the macro stress,strain,and spring back accuracy of profiles are studied by the controlled variable method.The results show that as the elastic modulus increases,the stress-strain distribution of the profile becomes more and more nonuniform,while the spring back of the profile decreases with the increase of the elastic modulus.As the friction coefficient increases,the stress and strain distribution become more and more uneven,and the greater the spring back of the profile after unloading,the worse the forming accuracy.When the ultrasonic vibration-assisted forming is introduced,the stress and strain distribution of the profile is more uniform than that of the traditional stretch-bending forming,and the spring back of the profile is reduced after unloading.When the ultrasonic vibration frequency is 20 k Hz and the ultrasonic amplitude is 0.02 mm,the profile spring back is suppressed.The elastic effect was the best,which was 20.6% lower than that without the application of ultrasound.A flexible multi-point tensile bending test was carried out on the "L"-shaped aluminum profile,and the reliability test of the simulation was explored through the comparison between the test and the simulation.The results show that the test results are consistent with the simulation results,and the spring back deformation trend of the profiles is consistent.Therefore,the stretch-bending forming process can be improved with the help of finite element simulation technology,the test production efficiency can be improved,and the production time and cost can be reduced.In this paper,the elastic modulus,friction coefficient,ultrasonic vibration frequency,and ultrasonic amplitude are used as test factors,and an orthogonal test with four factors and five levels is designed,and the data is analyzed by the range analysis method.The results show that the order of influence of each process parameter on the spring back accuracy of ultrasonicassisted multi-point stretch-bending is: elastic modulus,friction coefficient,ultrasonic amplitude,ultrasonic vibration frequency.The optimal level test combination is: the elastic modulus is 71000 MPa,the friction coefficient is 0.05,the ultrasonic vibration frequency is20 KHz,and the ultrasonic amplitude is 0.01 mm.Based on the simulation results of the orthogonal test,the ultrasonic-assisted multi-point bending test was carried out on the "L"-shaped aluminum profile.The test results show that the experimental results are consistent with the simulation results.