Study On Mechanical Characteristics And Forming Limits Of Aluminum-lithium Alloy Sheets

Aluminum-lithium alloys are widely used in the aerospace field due to low density,high elastic modulus,high specific strength and high specific rigidity.The mechanical characteristics and forming limit from the perspectives of yield behavior,hardening law and local limit strain capacity of 5A90 aluminum-lithium were investigated.Uniaxial tensile test,forming limit test and deep drawing test were carried out.Based on the anisotropy coefficient and yield stress of the result obtained from the unidirectional tensile test,the parameters of the Hill48,Hill90 and Barlat89 yield criteria were calibrated.Then,the finite element simulation method was used to verify and modify the hardening model.In additon,the Hill-Swift,Keeler,MMFC and M-K models were established.At last,the material model was verified and applied.The uniaxial tensile test results showed that the strain rate influenced the anisotropy of the 5A90 aluminum-lithium alloy.Under these strain rates,the overall anisotropy distribution index are:η_{0.0 01}=42.32%,η_{0.0 1}=45.21%,η_0.1=58.31%.The overall accuracy coefficients of Hill48,Hill90 and barlat89 are:β_{Hill4 8}=11.36%;β_{Hill 90}=7.29%;β_Barlat89=18.47%.The finite element simulation method was used to verify and modify the hardening model under large strain conditions.It is found that different hardening models show large differences in their ability to predict hardening laws under large strain,and the modified Voce model is the best.By calculating the theoretical prediction models of Hill-Swift,Keeler,MMFC,and M-K forming limits,and comparing the prediction capabilities of different models for ultimate strain,it is found that M-K model displays the highest prediction accuracy.The friction coefficient is determined to be 0.2 by comparing the FE simulation and experimental results of the diameter 70 mm.By comparing the simulation and experimental results with the diameter of 80 mm,it is find that R_Hight is 0.9997 and R_Thickness is 0.9996.The shape and position of the crack are same in the 90 mm results.Figure 53;Table 18;Reference 62...