Design And Analysis Of An Automcatic Folding And Tensioning Device For Fuel Tank's Closed Girth Welding In The Vertical Assembly

Friction stir welding has been widely used in the aerospace field due to its excellent technical characteristics,but the corresponding internal support and external pressure auxiliary tooling is required during the welding process.Our country has matured the production technology of 3.35m-class fuel tanks.It adopts the horizontal assembly process.When realizing the last closed girth welding,technicians are required to enter the fuel tank through the manhole to install the internal support device,which is extremely inconvenient and time-consuming.The new generation of 5m-class launch rocket propellant fuel tank has a large diameter and thin wall panels,which will cause serious dead weight deformation when placed horizontally in a horizontal assembly.The traditional manual disassembly of the internal support device is no longer applicable.In this paper,an auxiliary tooling with automatic folding and tensioning device is designed for fuel tank' closed girth welding in the vertical assembly.First of all,according to the design requirements and the current status of the use of existing internal support devices at home and abroad,the structure design of the automatic folding and tensioning device is completed.It is divided into three parts: the central column,the unfolding organization,and the support platform,and the details are introduced.The details and design basis are displayed using three-dimensional modeling software,and the key components such as screw jacks and hydraulic cylinders are selected;then the positive kinematics models of the two unfolding organizations are established using the complex vector method,and the motion law of the original moving parts is set,Draw the mechanism motion diagram,obtain the motion characteristic curve of the output member,compare the formula curve with the motion curve obtained by the ADAMS software motion simulation,and obtain the motion characteristics that are relatively in line with the real motion situation;finally,the finite element software ANSYS Workbench Analyze the shape requirements and stress conditions of the internal support device.Friction stir welding has strict requirements on the parallel seam and dislocation of the workpiece.The internal support device needs to compulsorily adjust the shape of the bottom of the fuel tank and the cylinder section during the unfolding process,and the stirring head is in When it is pushed into the interior of the workpiece,it will produce a huge upsetting force,which will affect the support strength and stability of the device.It is necessary to check the force and displacement state of the inner support device under these two conditions.The research results of this paper have completed the structural design,kinematics analysis and statics analysis of the automatic folding and tensioning device,and provided a new auxiliary tooling for fuel tank' closed girth welding in the vertical assembly.