Research On Side Rolling Symmetrical Thickening Forming Of 2219 Aluminum Alloy Sheets

With the rapid development of aerospace technology,the size of aviation components is gradually increasing.As one of the largest and most important structural members of the rocket body,the rocket propellant tank is limited by the existing forming technology and still needs to be manufactured by the method of tailor welding.The existence of welds will inevitably reduce the load carrying capacity of the tank,so how to improve the quality of the weld has become the main research object.The rocket propellant tank is a large-scale thin-walled structural member,and the material strength of the welding heat-affected zone is often reduced during welding,compensation can be obtained by pre-thickening the welded edges of the sheet to maximize the reliability of the tailor welded structure.In addition,the sheet less than the ultimate thickness(2mm)cannot be friction stir welded,and the local thickening can meet the requirements of the thickness of the sheet for welding.This topic proposes a new process of multi-pass molding to cause side-side symmetric thickening deformation of the welded edge of the sheet.The process uses a roller with a specific groove to contact the sheet and deform the welded edge of the sheet,and then the roller rolls along the edge to locally thicken the sheet.Because of the need for multi-pass molding,a variety of roller-type groove parameters and forming schemes are designed for each pass according to the deformation requirements,the finite element simulation software ABAQUS 6.14 was used to simulate the various schemes and parameters and compare the simulation results to select the optimal parameters and forming scheme of each roller type groove.The simulation results show that for a sheet with a thickness of 2.5 mm,the sheet can be locally thickened to 5 mm by three passes,and the sheet having a thickness of 2 mm and 1.5 mm can be locally thickened to 5 mm by four passes,the thickness ratios are 2.0,2.5,and 3.3,respectively.The local thickening forming experiment was carried out on the 2219 aluminum alloy sheet,and the deformation force was applied to the sheet in the vertical direction,and the displacement was applied in the horizontal direction to determine whether the defects such as instability,fracture,and the thickening ratio after each pass were measured.Through multi-pass multiple feed forming,the plate with thickness of 2.5mm was successfully thickened to 5.2mm by two or three passes,and the thickening ratio was 2.08;the plate with thickness of 2mm was passed through three paths.The secondary forming was locally thickened to5.22 mm and the thickening ratio was 2.61.The feasibility of the process was also verified while obtaining qualified local thickened sheets.The forming limit,forming law and forming defects in the forming process were studied.The numerical simulation and experimental results show that The single maximum feed of the roller in the vertical direction decreases with the increase of the deformation zone height of the sheet,and the two are linear in a certain range;the main defects appear as instability,distortion and fracture in the thickness of the sheet.When it is small,there is a defect that the deformation zone is curled and folded.