Addition of pulling force to pipe bending method using a floating expanding plug

摘要

Addition of pulling force at the exit in circular pipe bending using a floating expanding plug method is investigated both experimentally and theoretically. In the experiment, rotary draw bending using an eccentrically fixed expanding plug, which bears resemblance to the floating expanding plug method, is performed by varying the pipe expansion ratio, eccentricity, bend radius and pulling force ratio, and bending performance is examined in relation to the pulling force ratio. Draw bending using an eccentric plug fixed protrusionly produces a smaller bend radius and smaller flattened cross sections in pipes than using a concentric plug fixed normally at any pulling force ratio. However, draw bending using only pulling force produces large flattened cross sections compared with those using one-third or two-thirds of the pulling force, indicating that there is an optimum pulling force ratio. Based on the results, addition of pulling force is suggested for the floating expanding plug method. This suggestion is also supported by theoretical analysis using the slab method.