Dynamic Fe Analysis On High-strength Steel Variable Section Roll Forming With Protrusion And Hole

To realize "ligtweighting" in automotive manufacturing field, more high-strength variable section profiles are needed for body structure in automotive field. This kind of parts for car usually has complex cross-section and is difficult to mold. Some of these parts are with protrusion and hole. This is meaningful to the development of variable section roll forming. In this study, Dynamic/Explicit finite element algorithm is used to simulate the variable section roll-forming process based on the bottom stiffener with protrusion and hole of B70vehicle B-pillar.In this paper, based on the roll-forming process made by COPRA RF, the FE model of a twelve-step variable section roll forming of the profile with protrusion and hole is established to analyze the mechanics and the deformation characteristics of the forming procedure. Firstly, the geometric models for the rollers and the original steel are established by CATIA and the assembly is finished. Secondly, these geometric models are imported by HyperMesh to mesh the rollers and the original steel and to choose the unit type for all the elements. Then some inp profiles would be exported. In the end, ABAQUS receives these inp profiles, and establishes the FE modle of the twelve-step roll-forming process.The FE model is mainly for steels of which the initial yield strenth are600MPa and1200MPa. According to the results of the simulation, the mechanics and the deformation characterstics of the forming procedure are summaried preliminarily. The results point out that corners at cross-sections of the profile, especially at the cross-section changed all of a sudden, are most prone to rupture, and that springback is mainly happened at the longitudinal length direction. Finally, equivalent stress, equivalent strain, and sheet thickness are extracted from the simulation results and studied comparatively. The results of this simulation show us that these is no obvious strss concentration near the edge of the protrusion and hole, and that the change-rates in diameter of the protusion and hole are within reasonable limits. In this paper, the impact of intensity on the simulation results is analyzed. The results point out that the intensity has little effect on the distribution law of stress and strain, the thinning trend when the sheet bends and the law of spingback, but with the yield strength’s increasing, the extremum values of the stress and strain increase, the strss concentration is more obvious at the corners, the maximum thinning amout of the steel’s thickness decrease at the corners of the profile, the springback amount increase and the maximum forming load and torque increase too. In the end of this paper, the effect of the movements of rollers is studied as well. The results point out that this kind of movements has little effect on the distribution law of stress and strain, the thinning trend when the sheet bends and the law of spingback, but it makes the ultimate stress and strain distribution more uniform, and it slightly increase the springback amout at the longitudinal length direction and slightly decrease the maximum forming load.In this study, the feasibility of using flexible roll forming to produce high-strength steel with protrusion and hole is verified through simulation method. The design of the rollers and the parameters used in the simulation are tested to be reasonable as well. These are of great importance to understand the appearance of the forming defects. In addition, the forming load and torque of the rollers are also obtained to guide the design of the variable section roll forming product line. A series of patents has already been applied based on this paper.