Influence of U-O bending process parameters on the friction coefficient

The U-O bending process is a manufacturing method for the production of pipes with large diameters and its manufacturing operations comprised of C forming, forming the plate into U shape, forming U into O shape, welding and expansion. With regard to the forming mechanism at O forming step, friction and wear influence the process. In this study, the effect of friction on the forming load has been studied. For this purpose, the influence of factors such as bending radius in the U forming step and the quality of surface roughness for several plate thicknesses on the forming load have been investigated by means of analytical and numerical modeling. Based on the results, proper selection of the initial bending radius in the U forming step is one of the most effective factors in reducing the friction force. Also, the reduction of the friction factor between the workpiece and the die has a significant impact on decreasing the pressing force. The results of the numerical modeling based on the finite element method and the analytical analysis have been compared, and the maximum error obtained was 8.6 %.