Study On The Quality Of Products Formed By Rotary Draw Bending For Ribbed Rectangular Profile

The protective beam of commercial vehicle with ribbed rectangular cross-section is made of B700 L high-strength steel and is produced by roll bending process and rotary draw bending forming process.Due to the unique cross-sectional shape,the protective beam not only ensures excellent anti-collision performance,but also meets the need of lightweight design for automobile.In order to achieve the installation requirement,both ends of the protective beam need to be bent to a certain angle.However,owing to the high strength and poor plasticity of high-strength steel and the complexity of the cross-sectional shape,the protective beam is prone to defects such as section distortion,internal thickening,external thickness reduction or even cracking during the bending process,which affect the anti-collision performance.For the purpose of eliminating or mitigating the forming defects,it is necessary to study the forming quality of the profile after rotary draw bending.In this paper,the effect of different parameters on distortion of section,variance of wall thickness and fracture of outer wall are studied by carrying out numerical simulation of the rotary draw bending process combined with bending experiment of ribbed rectangular profile.The main research content and results are as follows:(1)The finite element model of rotary draw bending for the ribbed rectangular profile is established.The model of profile and forming dies are established and the key parameters of the model are determined based on the platform of ABAQUS.Finally,a finite element model of rotary draw bending which is consistent with actual forming process is established.(2)The distortion of section and the variance of wall thickness of the profile after rotary draw bending are studied.The reliability of the finite element model is verified by bending test and the section deformation and the thickness variance are defined by formulas.The numerical simulation results are discussed and the effect of mandrel properties,die clearance,forming speed and profile thickness on the distortion amount and wall thickness variance rate are analyzed.The results show that the forming quality achieves the best when the self-locking flexible mandrel is used.With the increase of the clearance between profile and die,the section distortion gradually increases while the wall thickness variance rate first decreases and then increases.With the bending speed increasing,the section deformation first decreases and then increases while the variance rate of the wall thickness gradually decreases.The section deformation decreases but the wall thickness variance rate increases as the profile thickness increases.(3)The bending limit of ribbed rectangular profile is studied.The distributions of stress and strain of the profile are analyzed and the external fracture is chosen as the evaluation criterion for bending limit.Simulation results are discussed to analyze the fracture limit under different bending speeds,frictions and profile thicknesses.The results show that the minimum bending radius decreases as the bending speed increases and increases with the increase of friction coefficient and thickness.The reliability of the law is verified by bending test.