Investigations On Springback Law Of Ultra High Strength Steel In Roll Forming Process

Springback defect of roll forming is an important factor that affect the accuracy of the products.Because of the high strength and poor plasticity of ultra high strength steel,the forming difficulty is greater than ordinary steel,and springback are more likely to occur.In this thesis,combined with experiments and finite element simulation,the influence of multiple forming process parameters on springback is comprehensively considered,and the springback regularity is carefully studied and summarized.On this basis,the springback mechanism of roll forming is described.To solve this problem,three roll forming experiments with different numbers of stages are designed,and forming angles are assigned to each experiment.By analysis the experimental data,the change trend of the springback angle is obtained.The change regularity of the springback angle is studied and elaborated from the aspects of forming angle,increment angle and number of stages,which provides a reference for subsequent theoretical research.On the basis of experiments,a finite element simulation model of ultrahigh strength steel roll forming is established,and the accuracy of the finite element model is verified based on forming experiments.The forming characteristics of V-shapes is analyzed,and the distributions of total strain,plastic strain and elastic strain in the transverse direction of the plate are analyzed.The results showed that the peaks of total strain,plastic strain and elastic strain occur at the bend zone,and the trend of elastic strain and springback angle are basically the same,and the ratio of the elastic and plastic strains is similar to the ratio of the springback angle and the forming angle.Therefore,it is concluded that the elastic strain is the decisive factor influencing the springback angle.Increasing the increment angle can effectively increase the plastic deformation of the corners,increase the equivalent plastic strain value,improve the material flow at the corners,reduce the thickness of the sheet,and reduce the springback angle.Increasing the number of stages is conducive to the accumulation of plastic deformation,so that the ultimate equivalent plastic strain increase,effectively reducing the springback angle,improve the forming accuracy.