Impacts of mandrel parameters on forming quality of tube bending with small bending radius

To enhance the quality of tube bending with a small bending radius, a three-dimensional finite element (FE) model was developed to simulate numerically controlled (NC) bending of stainless steel tubes made from 21-6-9 alloy. Subsequently, an analysis was conducted to examine the influence of mandrel parameters on the forming quality in terms of the rate of wall thickening, rate of wall thinning, and ovality of cross-section. The findings indicate that increasing the mandrel axial feed or mandrel diameter leads to a slight decrease in wall thickening rate, a noticeable increase in wall thinning rate, and a significant reduction in cross-section ovality. Optimal values for the mandrel axial feed and mandrel diameter are determined to be 0.5 mm-1.5 mm and 5.23 mm-5.43 mm, respectively. These results have important implications for guiding the design of mandrel parameters and enhancing the forming quality of NC bending for stainless steel tubes made from 21-6-9 alloy with a small bending radius.