Study on twisting and bowing of roll formed products made of high strength steel

• Published in: International journal of precision engineering and manufacturing Vol. 14; no. 9; pp. 1527 - 1533
• Main Authors: Cha, Wan-gi, Kim, Naksoo
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2013
• Subjects: Engineering; Industrial and Production Engineering; Materials Science; Elastic-plastic FEM; Bowing; Roll forming; Twisting; High strength steel
• ISSN: 2234-7593; 2005-4602
• DOI: 10.1007/s12541-013-0206-8

Steel has been developed to have higher strength than ever before, especially for use of the lightweight structures of automobile. It needs to confirm spring back defects of cold roll forming of high strength steel, in which a sheet metal strip is gradually and successively bent into a desired profile. We developed a numerical analysis program based on the elastic-plastic finite element method to simulate roll forming of arbitrary cross sections. We applied augmented Lagrangian technique to solve contact problem between rolls and strip. Cross sections with different flange heights passing through three passes of roll stands have been experimented. The amounts of twisting and bowing occurred after roll forming were measured for both products made of mild steel and high strength steel, respectively. The performance of the developed FEA tool has been verified with measurements in terms of accuracy. The product of high strength steel showed more degrees of twisting and bowing than those of mild steel. We proposed a method to reduce the defects by compressing the web in thickness direction. It is confirmed using the verified FEA tool that the proposed method can reduce twisting and bowing of roll formed products significantly.