Formality and influence of pre-strain on bake hardening behavior of DP900 steel
The forming limit diagram of DP900 steel for automotive structural components was tested and investigated,and the mathemati-cal model was used for prediction analysis.The influence of pre-strain on bake hardening value was studied from the microscopic view by means of internal friction instrument and transmission electron microscopy.The results indicate that the mechanical properties of DP900 steel at room temperature are the yield strength of 604 MPa,the tensile strength of 935 MPa,the uniform elongation of 14%and the lon-gation after fraction of 19%.The forming limit FLD0 is 0.245 during the stamping process,and the prediction error of the mathematical model of forming limit based on the Hollomon equation is 0.2%-13.5%with an average error of 5.87%.The value of pre-strain has great influence on BH value.As the pre-strain increases,the BH value first increases and then decreases,reaching the highest value of 45 MPa with pre-strain of 7%.The variation trend of the peak value of internal friction is consistent with the BH value.
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