Research On Roll Forming And Springback Of Hat-shaped Based On Boundary Condition Forming Angle Distribution Function

The hat-shaped part is an economic section profile with high structural strength,high economic efficiency and low energy consumption,and thus is widely used in industries such as automobile,aviation,construction and civil.At the present stage,the roll forming technology mainly relies on the production experience to randomly distribute the roll forming angle of each pass,and lacks the scientific theory guidance of dividing the forming angle.so that stress concentration often occurs in the forming process,leading to the defects such as springback and reducing the forming precision and quality of products.In this paper,the hat-shaped roll forming parts with small section are taken as the research object in industrial production.Firstly,the five-boundary condition forming angle distribution function is proposed to determine the forming angle of cap parts.Copra finite element software is used to simulate the peak longitudinal strain in the forming process,and the optimal forming angle distribution interval is confirmed by experiment.Then,using ABAQUS finite element software simulation and experimental contrast five-boundary condition forming angle,four-boundary condition forming angle,forming angle increment 10° three sheet stress and strain in the forming process and springback.Based on the optimal forming angle,the effects of forming angle,sheet thickness and material yield strength on the stress and strain distribution and springback of sheet during roll forming were studied to evaluate the forming angle distribution method and obtain the forming law of process parameters on roll forming process.Finally,the change of the grain in the sheet angle zone in the roll forming process was studied from the microscopic perspective,and the effect of the forming angle,sheet thickness and material yield strength on the transverse strain of sheet in the roll forming process was further analyzed.The results show that the stress,strain and springback of the forming angle based on the five-boundary condition is smaller than those of other forming methods,which shows its forming superiority.The stress and plastic strain in the sheet forming corner zone are much higher than the web zone and the flange zone,and the transverse strain in the forming corner zone is higher than the longitudinal strain.With the increase of sheet thickness,the stress and strain of sheet forming zone increase correspondingly.The peak longitudinal strain increases with the increase of forming angle.In the case of a certain roll forming angle radius,the springback decreases with the increase of the sheet thickness,and the springback amount basically has a linear relationship with the sheet thickness.The springback amount of the sheet also increases with the increase of the forming angle and the yield strength.but increase the pass or increase the correction roller can effectively reduce the springback.The maximum stress and strain load are reduced(after springback)by 3Mpa and 0.01,based on the five-boundary conditions,resulting in a 1.40° springback,but the springback is the slightest compared to other forming methods.The springback is only 0.14° after adding 1° correction roller compensation.Simultaneously,it is proved from the microscopic point that the stress and strain(transverse strain)of the forming corner of the sheet increase with the increase of the sheet thickness,and increase with the increase of the forming angle.However,in the direction of sheet thickness,the tensile strain of the outer grain in the forming corner is greater than the compressive strain in the inner layer,which indicates that the reduction of the thickness in the forming corner zone is inevitable.