The effects of the roller tip radius of curvature on defect formation in the nosing of a SUS409 tube were investigated using finite element simulations. For a roller tip radius of curvature of 6.0 mm, a large inwardly convex bending deformation occurs and the tube end becomes wrinkled. A smaller roller tip radius of curvature is associated with a larger axial elongation and a smaller wall thickness ratio. The wall thickness ratio is smallest when the tip curvature radius is 8.0 mm, where cracks occur. The damage value obtained from the ductile fracture criterion becomes maximum at the tapered corner. That maximum value decreases as the roller tip radius of curvature increases.
