Abstract: The process of multi-pass offset tube neck-spinning is simulated by MARC, the 3D elasto-plastic finite element software. 6061T1 aluminum alloy (annealed) is taken as the the material investigated. The simulation result of the distribution of stress and strain is verified by experimental result based on mesh circle method and variation of microstructure of workpiece. It shows that the distribution of strain and stress is non-uniform due to oblique; the equivalent stress distributes along axial direction section by section, and the equivalent stress reaches the maximum at the opening end of the spun workpiece. Along circumferential direction, the equivalent strain decreases gradually from 0° area, where the biggest oblique amount exists, to 180° area, where the smallest offset amount exists; and reaches the maximum at 0° area and the minimum at 180° area. Along axial direction, the equivalent strain increases gradually at 0° area and decreases gradually at 180° area. During multi-pass neck-spinning, the thickness at the middle section of spun workpiece increases due to the remarkable thickening effect in the backward path spinning. The simulation result of the thickness distribution at the middle section of spun workpiece during multi-path neck-spinning conforms well to the experimental result with maximum deviation less than 10%, indicating the validity of the FEA model. The automobile exhaust pipe with oblique tube end has been produced successfully based on the theoretical analysis and experimental research.

Key words: Multi-pass spinning, Neck-spinning, Numerical simulation, Oblique tube