Design And Simulation On Clamping And Positioning System For Full-station Underwater Stitch Welding Machine

Underwater friction stitch welding is a new type of solid-phase connection technology.Compared with other underwater connection technology,underwater friction stitch welding contains advantages as followed,such as insensitive to water depth,small welding deformation,good mechanical properties,high efficiency,etc.Aiming at diversity of underwater tubular repair and based on the previous study of the stitch welding principle prototype,this thesis focus on the design and simulation research of the clamping mechanism and spindle positioning and locking mechanism for friction stitch welding machine which can adapt to the underwater environment.Experiments have been done in the air and underwater to verify the reliability of the clamping mechanism and spindle positioning and locking mechanism,and also lay a foundation for further research and engineering application.Firstly,based on the analysis of the underwater stitch welding requirement,typical welding positions,clamping process and welding process,friction welding machine's technical requirements are proposed.According to the technical requirements,underwater friction stitch welding machine scheme and repairing system have been established.which provide the basis for designing the clamping mechanism and spindle positioning and locking mechanism.Secondly,pipeline structure which is used in the sea trial test is designed based on the typical pipes and representative welding positions are determined on the structure.Clamping structure of the welding machine is designed by improving the clamping structure of the principle prototype.And working pressure of three most dangerous position are calculated.Contact state analysis between clamping mechanism and pipe has been simulated through the finite element analysis software to verify the clamping mechanism's reliability.Once more,force analysis positioning mechanism and locking mechanism has been done under the dangerous conditions Enables the friction stitch welding machine spindle to move and lock in all the positions.Simulation and analysis of the system are been done through software AMESim to prove the system satisfying the underwater welding condition and positioning error of the spindle positioning mechanism are analyzed in the simulation.Finally,friction stitch welding machine is manufactured.Welding test for the pipe is carried out in the air and underwater,which provides realistic basis to the engineering application.Positioning accuracy and repeat precision experiment of three directions has been carried out to get the actual position error is larger than the simulation error.The clamping mechanism is tested to verify the reliability.It also validates the reliability of spindle locking mechanism.