Research On Large-size Press-bending Process Of Bimetal-thick Composite Plate

Bimetal-thick composite plates with good strength,rigidity and corrosion resistance are more and more widely used in petrochemical industry,shipbuilding,aerospace and other industries.However,due to the discrepancies in material properties and thickness characteristics of the Bimetal-thick composite plates,compared with single-layer sheet and thin composite board,the thinning defects,surface wrinkling and springback control are more difficult to be guaranteed.At present,there is no mature theoretical method to guide the stamping process of Bimetal-thick composite plates.This paper takes copper / steel composite thick plate as the research object,uses finite element simulation,theoretical analysis and experimental verification to solve the optimal process parameters and predict the springback of the sheet.The main research contents of the thesis include the following aspects:(1)Fit the real stress-strain curve of the copper / steel composite plate material according to ASME standard,adpot a symmetrical model design,and a temperaturedisplacement coupling analysis step was selected to establish a complete thermal-mechanical coupling model of Bimetal-thick composite plates and solved using a display dynamics solver.Combining the results of finite element analysis,the correctness of the thermo-mechanical coupling model is verified by comparing the energy relationship in the quasi-static theory and the temperature field distribution after stamping,which provides a basis for the research of stamping forming process parameters on forming quality.(2)The method of numerical simulation combined with experiment is used to explore the influence law of the process parameters such as sheet heating temperature,die fillet,die gap and friction factor.The maximum thinning rate,maximum thickening rate and maximum stress of the composite board after forming are evaluated Index,using entropy weighting method and response surface model to establish a comprehensive evaluation model of hot stamping products of bimetal-thick composite plates,and using genetic algorithm to multi-objective optimization of the evaluation model to solve the optimal process parameter combination.Guide the actual production and processing according to the optimal combination of process parameters,and verify the correctness of the proposed method.(3)Based on the thick-walled theory and considering the effect of shear deformation,the characteristics of the analytical expression are analyzed,the undetermined coefficients are set,and the results of the finite element analysis are combined to determine the value of the undetermined coefficients in the analytical formula to calculate the theoretical springback amount after compression-bending forming.The theoretical springback calculation results are compared with the finite element analysis springback results to verify the correctness of the springback prediction method.The research work provides theoretical basis for the selection of heating temperature of Bimetal-thick composite plates,fillet of die,die clearance,friction factor and prediction of springback after stamping,and provides reference for the selection of optimal stamping process parameters.