Experimental and Numerical Study of Rotational Draw Bending Process of SS-304 Thin-walled Pipes Using Polyurethane and NBR Mandrels

Abstract

One of the methods of forming pipes is the rotary draw bending process. Today, the bending of thin-walled pipes with a low radius of curvature is widely used in the automotive, military, and aerospace industries. This process is used to bend high-strength pipes. In this paper, at first, the necessary models were created to simulate the bending process of the rotary pipe. Then, the mechanical and physical properties of stainless steel 304 and elastomers were determined. Then, the forming force and changes in pipe wall thickness were experimentally and numerically measured. The process simulation was analytically performed by polyurethane elastomeric and nitrile rubber mandrels in ABAQUS finite element software. The results show a good agreement between simulation and experimental results. Finally, the effects of process parameters including mandrel type, pipe diameter, and bending radius were analyzed on the maximum forming force by factorial analysis. The results showed that the maximum forming force for both types of mandrel materials obtain for pipes with small diameter and high curvature radius. Also, the bending forces increase 5 times by 30% increasing the bending radius, for pipes with smaller diameters. In addition, in equal diameter and radius of bending, the bending forces in the case of using polyurethane mandrel are 25% more than nitrile mandrel.