Industrial validation of strain in cold roll forming of UHSS

Abstract

Cold roll forming is a highly productive sheet metal forming process capable of producing an exceptional range of profile geometries. Over the last few years customers have increased the demand for high value components, through the specification of complex profiles, tighter tolerances and/or use of high strength materials. In particular, there has been a high interest by the automotive industry in utilising ultra-high strength steels (UHSSs) within the roll forming process. These steels are ideal for the forming of lightweight products, which possess increased material performance when compared to traditional low strength steels. The industry’s attraction towards the roll forming process may be due to the increased deformation capabilities it can provide and due to the formability limitations of UHSS when using traditional stamping or press braking processes. This investigation aimed to determine an appropriate approach to simulating the cold roll forming process using UHSSs for future industrial applications. Currently a large volume of research can be found on the material characterisation and formability of UHSS using traditional processes. While the interest in roll forming is rapidly increasing over time, there remains a large research gap in this field. Hence, a dual phase steel (DP1000) and complex phase steel (CP1000) provided by TATA Steel were analysed using a five pass roll forming assembly to form the following two profiles: (a) V-section; and (b) flat strip with rib feature. The principal strains along the outer radius of each specimen were analysed using a GOM Argus photogrammetry system. A circle grid analysis was the method used to complete these measurements. The strain analyses were compared with corresponding strains along the surface of the finite element (FE) analysis model results. The non-linear FE simulations were carried out using COPRA® FEA RF 2017. Correlations in the results were achieved, setting a foundation for further investigations on the formability of UHSSs.