Research Of Flange Defects In Flexible Roll-forming

Flexible roll-forming is a new kind of roll forming technology which can form variable cross section profiles by servo motor drove rollers. The variable cross section profiles are widely used in many fields such as car manufacturing and construction industry because they are light but stiff.Compared with common fixed cross section profiles, the strain and stress condition of the variable cross section profiles are usually more complex. During the forming process, the variable cross section profiles not only suffers all the problems which the fixed cross section profiles own, but also have to bear extra deformation caused by the special curve of its profile. To reveal the law of the variable cross section profiles forming process, the flange springback and the flange edge-wave phenomenon were deeply studied in this research.For the springback phenomenon of the flange:by setting different technological conditions such as flange height, flange forming radius, sheet thickness and material property, the single-axis flexible roll-forming FE model was built to simulate the springback phenomenon of the flange, some experimental tests was carried out. The results demonstrate that the flange height, which is not easy to be interference, plays a dominate roll in flange springback of flexible roll-forming. The flange forming radius also has a strong influence on the flange springback. Compared with flange height and flange forming radius, sheet thickness and material property have much less effect on flange springback angle. During flexible roll-forming, the flange height suffers a greater deformation compared with conventional roll-forming. The large longitudinal residual stress in the flange leads to serious springback.For the edge-wave phenomenon of the flange:by establishing dual-axis flexible roll-forming FE model, setting different technological conditions such as flange height, flange forming radius, sheet thickness and material property, the strains, stresses and the deformation displacement were studied. By study the formation process of the flange edge-wave of variable cross section, the results demonstrate that the edge-wave would get heavier with smaller flange forming radius and bigger flange height, this is because the longitudinal strain of the flange is getting bigger. Thicker flange would get larger longitudinal strain which does not necessarily lead to heavier edge-wave, choosing proper sheet thickness can improve forming property.