Finite element analysis of circle-to-rectangle roll forming of thick-walled rectangular tubes with small rounded corners

A novel circle-to-rectangle roll forming finite element model of thick-walled rectangular tubes was proposed in this paper. Circle-to-rectangle roll forming is usually used to manufacture thick-walled rectangular tubes. For thick-walled rectangular tubes with small rounded corners (the ratio of outer rounded corner radius to thickness less than 1.5), due to the limitation of measurements of rounded corner stresses, finite element model of the manufacturing process are alternative approaches for predictions of both von Mises stress and equivalent plastic strain in circle-to-rectangle roll forming. In this paper, the finite element model was built based on elastic–plastic finite element method. The simulation results of roll forming were compared with the experimental results to verify the accuracy of the finite element model. Von Mises stress and equivalent plastic strain at the rounded corners were analyzed, the possible crack position of thick-walled rectangular tubes during circle-to-rectangle process was predicted. In addition, the influence of three forming parameters (feeding speed, friction factor, rolling space) for the rounded corners were discussed by the equivalent plastic strain of the inner and outer surfaces. The finite element model of circle-to-rectangle roll forming could provide manufacture guide while manufacturing the rectangular tubes with small rounded corner.