The precise control of end flare with residual stresses of UHSS thin-walled component in roll forming process

To control precisely end flare of UHSS thin-walled component, FEA (finite element analysis) model of multi-pass RF (roll forming) process is established. Numerical simulations with developed FEA model considered Young's modulus variation and RF tests are conducted to explain the origin of end flare with residual stresses. It's found that the overlap of bending moment caused by residual longitudinal stress and twisting moment caused by residual shear stress in transversal-longitudinal direction leads to opening deformation in front end and back end for hat channel steel. End flare will decrease with the increase of flange length and increase with the increase of material strength. The effect of forming parameters on end flare is analysed that end flare can be reduced with UDT-type (USTB-Durable T) method, constant-arc-length method and appropriate forming parameters. The findings are applied to control end flare of hat channel steel in actual RF process to meet high-precision requirements.