Static And Dynamic Analysis Of Gantry Milling And Welding Equipment At The Bottom Of Storage Tank Of Super Large Diameter Launch Vehicle

High-thrust heavy-duty launch vehicle is one of the inevitable trends in the development of aerospace delivery technology.The tank is a very critical component in the development of heavy-duty launch vehicles.Nowadays,the most advanced tank integration process in the world is "friction stir welding and vertical assembly." There is a clear gap between China and foreign countries in the development of corresponding equipment.The static / dynamic mechanical characteristics of a large-scale gantry milling and welding equipment at the bottom of a rocket tank have been analyzed,aiming to improve the mechanical properties of the equipment and improve the welding accuracy of the bottom of the tank.The main research contents of this article are as follows:(1)Combined with the technological process of friction stir welding for the gantry milling and welding equipment at the bottom of the tank,the force models of the mixing head in the penetration and stable welding stages with / without included angle of the axis of the mixing head and the normal at the bottom of the tank are established respectively.The rule of the influence of the angle between the axis of the mixing head and the normal of the bottom of the tank on the working load of the mixing head during the penetration and the stable welding process is obtained,laying the foundation for the finite element analysis of the milling and welding equipment of the bottom of the tank.Based on the mechanical transmission path,the mechanical model of the milling and welding equipment of the bottom of the tank is established.(2)The static finite element analysis model is established to analyze the influence of the angle between the mixing head axis and the tank bottom normal under the action of the welding load on the static mechanical characteristics of the equipment,and the equipment is also analyzed.The strength is checked to lay a foundation for optimal design.(3)Based on the mechanical model of the tank bottom gantry milling and welding equipment,the constraint mechanism of the bolt connection,the gear transmission and the contact surface of the rolling guide is analyzed,and combined with the Lagrange equation,the dynamic mathematical model of the tank bottom gantry milling and welding equipment is constructed,and the first ten natural frequencies of the equipment are obtained by analyzing the dynamic model through MATLAB programming.(4)The box bottom gantry milling and welding equipment finite element analysis model is established.The function of the relevant contact surface is set to the joint stiffness model and TIE constraints,and the first ten natural frequencies of the equipment are obtained by finite element analysis.The results show that the natural frequency of the gantry milling and welding equipment at the bottom of the tank based on the joint stiffness model is closer to the analytical solution.Based on this,a harmonic response analysis is carried out,and the results show that the equipment is more prone to resonance when it is at the third natural frequency.The research results are of great significance for expanding the productivity of China's launch vehicle tank industry,improving the welding accuracy of the rocket tank,reducing its power-to-weight ratio,and improving the overall mechanical properties of the tank.