Study On Combined Spinning-rolling Precision Molding Technology For Flexible Annular Metal Bellows

Metal bellows are cylindrical thin-walled elastic shells with transverse ripples,which have good bending and softness properties.The metal bellows are widely used in many industries,such as petrochemical industry,aerospace industry,automobile,steel industry,refrigeration temperature control and so on.At present,the commonly used methods include mechanical forming,hydraulic forming,mechanical bulging and so on.Among them,mechanical rolling forming and continuous forming technology have the advantages of high production efficiency and good product performance,however,it is limited to the production of small diameter bellows,and the development of molds for medium and above diameter products is dependent on others.Therefore,it is necessary to make clear the forming mechanism,solve the core technology of forming mold development,and then lay a theoretical foundation for the development of medium product specifications.In this paper,numerical simulation and experiment are combined to do the following work:The DN10 annular bellows formed by spinning-rolling combined precision molding in a domestic factory were studied,which introduced the technological process and forming principle of this forming method,analyzed the sliding phenomenon in the forming process,researched the elasto-plastic deformation of bellows in the new forming method,and deduced the minimum wall thickness condition when forming.The finite element model of shallow wave spinning process in precision forming was established by using finite element analysis software MSC.MARC.The influence of die rotation speed and friction force on this forming process was analyzed,and the influence of process parameters on springback in shallow wave forming was analyzed.The finite element model of the dense wave rolling forming process was established and the influence of the reduction amount on this forming process and the triangle effect in this forming process were analyzed,the suitable forming parameters were found out according to the results of the finite element analysis.The finite element model of rolling-spinning combined precision forming was established,the bellows forming process of combined roll-spinning precision forming was simulated by using the determined forming parameters,and the forming results of each pass were analyzed.The variation rule of wall thickness and waveform parameters in the whole forming process were obtained.By using the forming parameters optimized by finite element simulation,the actual precision forming experiments were carried out,and the actual formed bellows were obtained,and its wall thickness and waveform parameters were measured.Compared with the finite element analysis results,the correctness of the finite element simulation was verified,and the uniformity of the wall thickness,wave spacing,inner and outer diameter and waveform of the bellows under the forming parameters was verified.This study provides a guarantee for the process stability of the combined precision forming of bellows with spinning and rolling,and lays a foundation for the development of the production process of the mechanical forming of medium caliber products.