Research On Multi-point 3D Stretch Bending Technology Of Roller-type Die

At present,3D aluminum alloy profiles are widely used in transportation fields such as automobiles,rail transit,and airplanes.The demand for 3D stretch-bent parts in other manufacturing fields is also increasing.However,most of the stretch-bending forming technology also use traditional integral dies,which can only be used for 2D forming.For 3D deformed parts,it is necessary to perform plane deformation first,and then perform torsional deformation under unloaded state.Roller-type die body multi-point stretch-bending forming technology combines stretch-bending and multi-point forming ideas.It can stretch and bend the profile in different dimensions without unloading to form 3D parts at one time.In the process of multi-point 3D stretch-bending forming of the roller-type die,there are contact and non-contact areas between the profile and the die part due to the discrete of the die,and the profile and the die are not fully bonded.The shape and surface of the roller-type die will affect the stress and strain distribution of the formed part and the forming accuracy.At present,the research on the multi-point stretch-bending parts of the roller-type die seldom involves the influence of the die on the stress and strain of the part.The main research contents and conclusions of this paper are as follows:We establish a multi-point bending model of roller-type die for aluminum profiles according to the combination of the process characteristics of the multi-point stretch-bending of the roller mold and the finite element theory.The material properties,mesh division and element properties were determined,and reasonable contact rules and boundary conditions were set.In order to carry out the multi-point 3D stretch-bending forming of the roller-type die,we select the L and T cross-section profiles as the research objects.And use the finite element simulation software ABAQUS to simulate and analyze the entire forming process.The forming stress and strain of the traditional stretch-bending and roller-type die multipoint stretch-bending parts were compared,the results show that the formed parts using the two forming processes have the same changing trend.The multi-point stretch-bending forming stress-strain curve of the roller-type die had obvious fluctuations,and the multi-point stretchbending forming part of the roller-type die had stress concentration and local deformation.Experimental studies had shown that product quality fluctuations were acceptable for engineering applications.Compared with the adjustable die and the extremely convenient control of part spring-back,this technology had obvious technical advantages.The finite element simulation of the multi-point stretch-bending of the roller-type die was carried out on the two cross-section profiles.The stress and strain of different layers at different positions of the formed part were analyzed,and it was found that the stress and strain distributions of different layers were different.The closer to the die layer,the greater the stress and strain fluctuations.To optimize the design of the roller-type die,the influence of the roller-type die profile and shape on the stress and strain distribution and the forming quality of the formed part was studied.The results show that the closer the curved surface formed by the roll-type multi-point die is to the traditional die,the more uniform the stress and strain distribution and the better the forming quality.For roll-type multi-point 3D forming,a different die combination for each die unit should be selected,and a die profile with a large contact area with the profile should be selected for testing.The optimized die is selected for the tensile and bending test,and the same conclusion was reached.The influence of the number of die heads,the amount of pre-stretching,the amount of supplementary drawing and the friction coefficient on the forming accuracy in the multi-point bending of the roller-type die was analyzed by orthogonal experiments.Using the results of orthogonal experiments,the optimal combination of process parameters was determined,and experiments were conducted to verify its effectiveness.The result shows that for a 6-meterlong part,the primary and secondary order of the influence of various process parameters on the forming accuracy is: The number of dies is greater than the amount of pre-stretching and greater than the amount of complementary stretching and greater than the coefficient of friction.The optimal level test combination is that the number of dies are 20,the pre-stretching amount is 0.6%,the supplementary drawing amount is 0.6%,and the friction coefficient is 0.1.