Study On Springback Prediction And Evaluation Of Automotive Aluminum Alloy Structure

Under the trend of lightweight vehicles,the proportion of aluminum alloy sheets used in car bodies has been increasing year by year.Springback defects that are prone to appear in the stamping process are one of the main reasons that hinder its large-scale use in car body manufacturing.The primary task in solving the springback problem is to accurately predict springback.Finite element analysis is an important tool for predicting springback.Choosing the appropriate constitutive model for finite element simulation can make the springback prediction results more accurate.Study the influence of different constitutive models on the accuracy of springback prediction,and analyze the stamping and springback of parts through a reasonable springback evaluation method to improve the production and development efficiency of aluminum alloy stamping parts and accelerate the aluminum alloy in lightweight body Application is important.This paper studies the springback prediction and evaluation of AA5754-O aluminum alloy structural parts.The main contents and conclusions are as follows:(1)Designed uniaxial tensile test,cyclic shear test and hydraulic bulging test respectively to study the mechanical properties of AA5754-O sheet under different stress states,analyzed and compared the mechanical properties of unidirectional stretching under different orientations.It shows that AA5754-O does not have obvious anisotropy;its shear modulus gradually decreases with the increase of the number of cycles during cyclic loading,the shear stress gradually saturates,and it will show a significant Bauschinger effect;Under the condition of equal biaxial tensile stress state,the yield stress of AA5754-O is 86.87 Mpa.(2)The binocular DIC data processing system was developed based on MATLAB and applied to the data processing of hydraulic bulging experiment.The system is based on the linear triangle method to achieve three-dimensional reconstruction of the sample,based on the finite strain theory to achieve the calculation of different types of strain tensor,in addition to data visualization.(3)Based on the experimental data,the parameters of AA5754-O constitutive model were calibrated,and the yield criterion and yield value of AA5754-O in different orientations were predicted using the yield criterion.Couple different constitutive models to the finite element model of aluminum alloy structural parts stamping springback through user material subprograms,and compare the springback prediction accuracy of different yield criteria by analyzing and comparing the displacement of each point on the part surface before and after springback.The results show that the Yld2000?2d yield criterion has a stronger ability to describe the mechanical properties of AA5754-O,and can also more accurately predict the stamping springback of AA5754-O aluminum alloy structural parts.In addition,the accuracy of springback prediction will be further improved after considering the influence of variable elastic modulus.(4)Analyze the shortcomings of the existing springback evaluation methods,and propose a curvature-based springback evaluation method,which includes the main processes of point cloud acquisition,surface fitting,curvature and curvature difference calculation,etc.The difference in curvature across the surface is used as an indicator for springback evaluation.In order to verify the feasibility of this evaluation method,the evaluation method was used to analyze the springback of an aluminum alloy structural component during the shaping process,and to achieve springback compensation based on the evaluation results.