Exploring effect of spinning gap on forming quality of second pass spinning of large-sized complicated thin-walled shell

Aim. The introduction of the full paper reviews a number of papers in the open literature and, in its last paragraph, proposes exploring the effect of spinning gap. Section 1 explains the method of our exploration, whose core consists of: (1) by introducing the shape size of a workpiece and its field variables after the first pass of spinning and springback, we establish the 3D finite element simulation model for the second pass which includes springback analysis and annealing operation; (2) using the simulation model, we investigate the effect of spinning gap on the forming quality of the second pass of spinning of large-sized complicated thin-walled metallic shell. Section 2 presents the simulation results and experimental results and their analysis. Its simulation results, given in Figs.7 through 14 and Figs.16 and 17, and their analysis show preliminarily that: (1) the forming height first increases and then decreases with increasing spinning gap, and there is a local wall-thickness reduction in the small cone angle segment of large-sized biconical workpiece; (2) the circumferential compression stress and tangential tensile stress both decrease with increasing spinning gap, thus reducing the possibility of fracture and wrinkle. Section 2's experimental results, given in Figs.18, 19 and 20, and their analysis show preliminarily that: (1) during the multi-pass of spinning of large-sized complicated thin-walled metallic shell, the wall-thickness of its workpiece should be reduced as much as possible in the first pass of spinning; (2) after the first pass, the shape of workpiece should be close to that of the next pass so that the spinning process can go on smoothly. Finally, through our exploration, we believe we have succeeded in making the shape of workpiece after the second pass of spinning meet the requirements for the final pass of spinning of large-sized complicated thin-walled metallic shell.