Analysis of stress-strain in the partial heating roll forming process of high strength square hollow steel sections

The demand for roll-formed high strength steel square hollow sections has extensively increased by automotive and construction industries due to their excellent structural performances and attractive appearances. However, due to their low ductility and demand for large forming tool loads, high-strength steels are challenging to be roll-formed at room temperature. Partial heating roll forming is a recently proposed manufacturing technique aiming to overcome these difficulties by applying temperature on bend areas. In this study, the finite element software LS-DYNA was utilized to predict effective plastic strain and stress developments and associated residual stresses induced during the partial heating roll forming method. Furthermore, comparisons were made between cold roll forming and partial heating roll forming methods. The results indicate that the effective stress value during the partial heating roll forming method was lower than the cold forming method. In addition, the product manufactured by the partial heating roll forming method had smaller and uniform residual stress distributions along the section perimeter and across the section thickness than the cold-formed counterpart. Further investigations on corner geometry showed that high strength steel square hollow sections with a minimum bend radius could be successfully manufactured using the partial heating roll forming method.