Springback Prediction And Control Of Stainless Steel Sheet Of Bright Trim

Automotive window bright trims usually made of stainless steel,aluminum alloy and other materials,are the forming products.The geometric shape of the window bright trims contains many free-form surfaces.The springback control of the window bright trims is the core of the forming process.In this dissertation,the SUS430 stainless steel sheet material was selected as the study object.Aiming at the control of forming springback of SUS430 stainless steel sheet material,the key problems including the solution and the selection of the yield criterion and the hardening model,the final decision of manufacturing parameters,and the control and predictions of the springback were deeply investigated.The specific studies was as follows,(1)The yield criterion and the hardening model of SUS430 stainless steel sheet material were established.The key mechanical property parameters of SUS430 stainless steel sheet material were obtained by the methods of DIC,tensile tests and shear tests.Then the parameters of three yield criteria of plastic forming were solved by the mechanical property parameters.The parameters of the isotropic hardening model equation were also solved by the software fitting.(2)The influence of different constitutive models on the springback of SUS430 stainless steel sheet material was studied.The influence of different hardening models on the springback of U-shaped parts was analyzed.The influence of different yield criteria on the springback prediction of free-form surface parts was studied.The results showed that the hardening models of Power and Voce could well predict the springback of U-shaped parts,and the average errors between the predicted results and the measured values were 0.08% and 0.26%,respectively.The results also indicated that the springback value predicted by YLD2000-2d was less than 0.398 mm,which was closer to the measured value less than 0.31 mm.The predicted values of other yield criteria were in great error with the measured values.(3)The influence of key forming parameters on the springback of free-form surface parts of SUS430 stainless steel sheet material were investigated.The forming test method of free-form surface parts was designed,and the experiments of different speeds and holding times were carried out by the servo press.The results showed that when the holding time was 5s,the average springback of free-form surface work pieces was the smallest,and the value was 0.13 mm.The results also indicated that when the forming speed was 77mm/s,the average springback of free-form surface work pieces was the smallest,and the value was 0.14 mm.All the experimental results were in accordance with the permitted scope of actual production.(4)The accuracy of forming springback prediction of window bright trim of SUS430 stainless steel sheet material was analyzed comprehensively.With the employment of the eatablished finite element numerical model of window bright trim,the established of SUS430 stainless steel sheet material by two yield criteria and hardening models,and the smallest springback manufacturing parameter,the springback of the bright trim was calculated.The results showed that the springback distance of the bright trim in local areas was changed from 0.4mm to 0.7mm,and in most areas were less than 0.5mm.After the actual trial production and measurement,the theoretical calculation was basically consistent with the springback of the actual products.The results revealed that the established constitutive model and the selected forming parameters can provide technical basis for the actual production and processing.