Research On Composite Flow Forming And Equipment Structure Design Of Thin-walled Cylindrical Parts With External Ribs

The thin-walled cylindrical part with longitudinal external ribs on the outer surface has the characteristics of thin wall thickness,large aspect ratio,and complicated structure.And it has important applications in the aerospace,defense industry and other fields.Traditional cutting,casting,extrusion and other methods have the defects of low material utilization,poor product performance,and high cost.It is difficult to guarantee both the quality of the product and the processing cost.The flow forming process represented by ball spinning has significant advantages in processing thin-walled cylindrical parts with ribs,but there is a problem of insufficient rib height.Therefore,in order to solve the existing problems,this these proposes a composite flow forming process based on flow forming.The composite flow forming process is divided into preforming and final forming.The ball is fed axially in the preforming stage to complete the partial forming of the outer ribs.During the final forming stage,the ball is moved axially and circumferentially to reduce the thickness of the blank and eliminate the depression,while transferring the non-ribbed zone metal to the ribbed zone,completes the forming of the external rib.By comparing the process principle and metal flow characteristics of the new process with the ball spinning technique and verifying with simulation and experiments,it is found that the composite flow forming process can greatly improve the filling effect of the external ribs,and the filling rate is increased from 63% to 97%.In order to reveal the flow trend in the process of metal deformation,the paper studies the stress and strain of the material and the metal flow velocity during the deformation process.It is found that the new process can change the stress state of the metal through the preforming process,thereby changing the metal flow trend.The circumferential flow of the metal is promoted,and the tangential strain is increased by33%.At the same time,the axial flow of the metal is suppressed,and the axial elongation is reduced from 2.7 mm to 1.0 mm,indicating that more metal flows to the outer rib zone.The research shows that the process parameters such as the reduction of preform,the distribution ratio of the pass reduction,and the ball diameter have a greater impact on the effect of rib filling.A larger filling rate of the ribs requires a larger spinning pressure.In order to ensure that when the filling rate of external ribs is good,a combination of process parameters with small rotational pressure is selected.The external rib filling rate and rotational pressure are used as optimization indicators.Through the orthogonal test,the optimal process scheme of composite flow forming of thin-walled tube with longitudinal external ribs on the outer surface is obtained.The results show that two passes are used,the pass ratio is 3,the relative reduction of preform is 50%,and the ball diameter is 18 mm.Under the conditions of such process parameters,the external rib filling rate of the composite flow forming process was increased by 30%,and the feed force was only increased by 12%.The feasibility of the composite flow forming process was verified by experiments.Aiming at the characteristics of the composite flow forming process,a three-beam four-column structure was adopted to design the overall structure of the composite flow forming equipment for the thin-walled cylindrical parts with longitudinal external ribs on the outer surface.The virtual prototype design was realized through theoretical calculations and three-dimensional solid modeling.Further promotion of the composite flow forming process provides an important reference.