Numerical simulation and experimental research on the multi-pass neck-spinning of non-axisymmetric offset tube

The process of multi-pass offset tube neck-spinning is simulated by adopting MARC, the 3D elasto-plastic finite element software. 6061T1 aluminum alloy (annealed) is taken as investigating material. The distribution of stress and strain, the dimensional accuracy, such as thickness reduction, linearity, ellipticity and axial elongation in different spinning passes during multi-pass offset tube neck-spinning are simulated theoretically and studied experimentally. It shows that the distribution of strain and stress is non-axisymmetric; the equivalent stress distributes and varies along axial direction section by section, and reaches the maximum at the opening end of the spun workpiece. The thickness reduction at the opening end, and the ellipticity and axial elongation of the spun workpiece increase with increasing spinning passes; the linearity of the forward path spinning is significantly smaller than that of the backward path spinning. The simulation result of the thickness distribution of the workpiece conforms well to the experimental result with maximum deviation less than 10%. It indicates that the FEA model established in this paper is reasonable and reliable. The automobile exhaust pipe with offset tube end is produced successfully based on theoretical analysis and experimental research.