Study On Integral Forming Process Of Thin-walled Unequal-thickness Seamless Gas Cylinder Liner

The thin-walled unequal-thickness seamless gas cylinder liner is wound with high-strength carbon fiber reinforced composite material,and the cylinder as a whole has the characteristics of light weight,high strength,better gas tightness and sufficient safety performance,which can be widely used as a high-pressure storage container in the process of clean energy storage and transportation.In order to realize the overall lightweight of gas cylinders,thin-walled unequalthickness seamless gas cylinder liners need thin cavities in their structural design so as to reduce weight,while the mouths need to be thickened to meet the strength requirements of the threads,however,due to the large wall thickness difference between their mouths and cavities,the existing manufacturing process is difficult to meet their production requirements.To solve this problem,this paper investigates the integral forming process of thin-walled unequal-thickness seamless gas cylinder liner.The main research of this paper is as follows:(1)According to the structural characteristics of thin-walled unequalthickness seamless gas cylinder liner,two new process solutions are proposed,and a process route for thin-walled unequal-thickness seamless gas cylinder liner is drawn up by discussing the advantages,disadvantages and feasibility of the two process solutions.(2)Simulation of the whole process of forming thin-walled unequalthickness seamless gas cylinder liner by ABAQUS finite element software was carried out to further analyze the feasibility of the process.A finite element model of thinning spinning and push forming was established to analyze the stress-strain distribution pattern and changes of the workpiece surface after thinning spinning and push forming of seamless pipe billets,and the effects of two spinning methods,forward and reverse spinning,on the forming results and the effects of different lubrication conditions on the results of push forming were discussed.(3)The stress-strain distribution and geometric dimensional changes of the gas cylinder liner during necking and spinning were discussed by finite element simulation,and the distribution laws of three-way strain and equivalent effect variation between different thickness layers in the bottle mouth area were analyzed;and the effects of different process parameters on the maximum stress and minimum wall thickness of the bottle mouth were analyzed by response surface methodology(RSM).The NSGA-II algorithm was also used to optimize the response surface model with multiple objectives,and a set of optimal process parameters was derived.(4)Experiments on necking and spinning of billets as well as measurements on the formed workpiece were carried out to verify the correctness of the simulation and optimization results by comparing the wall thickness distribution and internal and external profile curves,and the expected geometry and optimal strain state of the gas cylinder liner were obtained,and the actual results met the expectations that the new process method has some potential in producing thinwalled unequal-thickness seamless gas cylinder liners.