Multistep-forming Numerical Simulation And Experimental Investigation On The Swing Arms For Automotive Torsion Beam

As a forming method for hollow components, multi-step forming process has gradually become an effective way for the lightweight of automotive. In this paper, the forming process of swing arms with different cross-sectional shapes and 3D bending curve was explored by using the methods of theoretical analysis, numerical simulation and experiments. In detail, some influence factors such as bending radius, mandrel, bending springback, loading paths and friction coefficient were analyzed. In addition, the closing force, strain distribution and defects control were paid high attention to in the optimization process. Eventually, swing arms with high dimensional and shape accuracy were manufactured successfully.Firstly, a comprehensive analysis of structure features of swing arms was carried out to obtain the forming plan, and the whole process included bending, preforming and hydroforming. Moreover, two-cavity in one mould was selected as the optimal forming method. Simultaneously, some process parameters were calculated, and the length of the original tube, outer diameter, thickness, yield pressure, calibration pressure and closing force would be of 120 mm, 60 mm, 4 mm, 69.82 MPa, 199.5 MPa and 11774.6 k N, respectively.Secondly, the material parameters and constitutive relation of Qste460 were obtained using tensile test. Subsequently, simulations of bending, preforming and hydroforming were conducted and optimized. The results showed that the minimum thinning rate of bent tube was 10.902% when the bending radius was 120 mm without mandrels in bending simulation. In the preforming process, displacement of upper die was set to 77 mm, a preformed part without crushing defects could be founded in thickness distribution nephogram. In the hydroforming simulation, as the optimization results, a hydroformed part with high quality could be manufactured through the combination of loading path 7 without feeding and friction coefficient 0.02, and the results showed that maximum thinning rate and thickening rate was 16.525% and 28.537%, respectively. Furthermore, the deformation and stress distribution of die were investigated under different loading ways of closing force. The results indicated that, compared to the constant closing force loading way, the total deformation, displacement in Z direction and equivalent stress of linear loading way were lower in value.Finally, the experimental research of swing arms was conducted based on the simulation results, moreover, strain distribution in typical positions was studied using mesh analysis method. The results proved that the hydroformed part with high thickness uniformity and fittingness could be obtained by optimization. In addition, wrinkle, fracture and undercut defects of part could be avoided to meet the working demands, which verified the consistency between numerical simulation and experiment.