Research On Springback Control And Compensation Of QP980 Steel Based On Arc Parts

QP steel is the latest third generation of ultra-high strength steel with good elongation and ultra-high strength,so it has broad application prospects.However,the problem of forming and springback of QP steel is still very serious because of the super high yield strength.Especially,the larger springback problem leads to the continuous repairing of the die,which wastes a lot of time and cost.In this paper,the springback problem of QP980 steel is studied based on self-designed arc parts,and a set of Springback Control and compensation process is put forward,which includes accurate prediction of springback,how to reduce springback,and compensation for springback.In the development stage of CAE,the advanced springback prediction model,Y-U material model,was used to predict the springback of arc parts,and compared with the two commonly used material models.The results show that the difference between the average rebound predicted by Hill+Y-U,Barlat+Y-U,Hill and Barlat material models and the actual value is 0.05 mm,0.1 mm,0.15 mm and 0.3 mm,respectively.Y-U material model can greatly improve the springback prediction accuracy of QP steel.In the process optimization stage,the central composite experimental design and response surface method are combined to analyze the process factors affecting the springback of arc parts,such as blank holder force,friction coefficient between lower die and sheet metal,and friction coefficient between blank holder and sheet metal.It is pointed out that the more fully formed the sheet metal,the smaller springback of arc parts.Then the process factors are optimized by multi-objective genetic algorithm based on response surface method,and the optimal process combination is obtained.With the optimized process parameters,the maximum springback of the simulated arc parts after trimming is reduced from 0.89 mm to 0.44 mm,which reduces by 50%.In the springback compensation stage,a set of springback compensation process is proposed to improve the springback compensation efficiency of arc parts.The first stage of this process is process optimization.Based on accurate prediction of springback and process optimization,springback of arc parts is minimized,which provides a good basis for springback compensation.The second stage is the robustness analysis before springback evaluation and springback compensation.Based on the virtual orthogonal experimental method,the robustness analysis of various process factors affecting springback is carried out.It is pointed out that due to the fluctuation of process parameters,the arc parts will produce about 30% unqualified products in the actual production process.The third stage is springback compensation.Based on the springback prediction results,the springback compensation of arc parts reduces the maximum deviation between the shape of the compensated product and the expected shape from 0.44 mm to 0.12 mm.The fourth stage is to analyze the springback and quality control of the compensated die.Based on the virtual orthogonal experimental method,the robustness of the process factors affecting springback and forming quality is analyzed.It is pointed out that the products stamped by the compensated die will fluctuate due to the friction coefficient and blank holder force fluctuation between the lower die and the sheet metal,and lubrication conditions will be increased in the production process.Appropriate reduction of blank holder force can improve the qualified rate of products.Finally,the forming quality of the arc parts obtained by experiments is good and the dimensional accuracy meets the requirements,which verifies the rationality of the Springback Control and compensation process of QP steel proposed in this paper.This process can not only improve the efficiency of springback compensation,but also improve the qualified rate of products.It has important practical significance in production.