Research On The Influence Of Multi-point Die And Process Conditions On Forming Quality For Aluminum Profile Of Multi-point Stretch-bending

For the plastic forming of aluminum profile,the flexible multi-point stretch-bending,as an advanced manufacturing technology,combines the idea of multi-point forming with stretch-bending process.A series of discrete multi-point dies replace the traditional solid bengding die,which can realize the die surface reconstruction and can be applied to a variety of cross-section profiles.Unlike traditional stretch-bending process,in the flexible multi-point stretch bending forming process,because profile does not completely contact with the multi-point die,but there are contact area and the contact area,so the structure of the multi-point die surface will influence the stress and strain distribution,the shape accuracy after forming and springback after unloading.Meanwhile the recent research object of flexible multi-point stretch-bending is still the single curvature parts,and there are not enough researches on the springback of the variable curvature forming parts.The purpose of this paper is to control the shape accuracy of multi-point stretch-bending forming parts.The main research contents and conclusions are as follows:Firstly,the finite element simulation model is established according to the process characteristics of flexible multi-point stretch-bending.The material parameters of 6005 A aluminum alloy,the method of component unit selection and mesh division,the setting of interaction and boundary conditions,and the representation and measurement method of springback were determined.The effect of the curvature and width of the multi-point die surface on the stress and strain distribution,the shape error before unloading and the springback were studied.The results show that the closer the curvature of the multi-point die is to the target shape,the more uniform the distribution of stress and strain are,and the smaller the shape error and springback are.The wider the width of the multi-point die is,the closer the formed whole die surface will be to the target shape.The uniform stress and strain distribution will reduce the shape error before unloading and springback.However,too wide multi-point die will inevitably increase the manufacturing cost,suitable MPD width is 150 mm.The test results are similar to the results of finite element analysis.The results show that using the optimized multi-point die can reduce the shape error and springback of aluminum profile after forming.For the forming parts of rectangular profile with variable curvature,firstly,the moving track of clamp with variable curvature is designed.Then,using the control variable method,the influence law of different process parameters on the springback of bending parts with variable curvature was studied.The springback of the forming parts with variable curvature decreases with the increase of the amount of pre-stretch and the amount of post-stretch,but the excessive amount of post-stretch will lead to the quality defects such as neck shrinkage.Process parameters affecting the variable curvature springback parts(MPD distribution density,amount of pre-stretch,amount of post-stretch and coefficient of friction)was carried out on the influence of variable curvature springback parts orthogonal experiment analysis,to determine the optimal process parameters combination,the results show that the effect of technical parameters on the springback of variable curvature progression for MPD distribution density,amount of pre-stretch,amount of post-stretch and coefficient of friction.The optimal horizontal combination of factors in the orthogonal test was obtained as follows: the horizontal clearance of the MPD body was 200 mm,amount of pre-stretch was 1.2%,amount of post-stretch was 1.0%,and the friction coefficient was 0.075.