Study On The Constitutive Model Of Al-Li Alloy And Its Secondary Development In ABAQUS

Finite element method,the FEM,is a powerful tool for simulating the thermoplastic forming process of materials.And the accuracy of the finite element simulation results is closely related to the accuracy of the constitutive model.In order to obtain high quality analysis results in the finite element analysis of Al-Li alloy,it is necessary to construct a more accurate constitutive model according to the thermal deformation behavior of Al-Li alloy.In this paper,based on the existing isothermal tensile test of 2099 Al-Li alloy,the flow behavior of 2099 Al-Li alloy in the temperature range,120?160C°,and at the single strain rate,?=0.0003ss-1,is analyzed.On the analysis results of flow characteristics,five constitutive models are selected and constructed.The three phenomenological constitutive models are Johnson-Cook model,Modified Johnson-Cook model and Voce equation whose model parameters are connected with Kocks-Mecking model.And two physical constitutive models are Modified Zerilli-Armstrong model and Kocks-Mecking model.Then,Voce analysis of 2099 Al-Li alloy was carried out using model parameters of Voce equation.According to the analysis results,the microcosmic mechanism of the alloy during plastic deformation is preliminarily determined.In order to evaluate the predictive power of the model for material flow behavior the fitting accuracy of the above model to the experimental data is analyzed.The results indicate that the prediction ability of Voce equation,Modified ZA model and KM model are good.The prediction accuracy of the KM model is the highest,but the MZA model is more suitable for the second development calculation of the constitutive model.The JC model and MJC model are not predict the flow behavior of the alloy accurately.In addition,the results of the Voce analysis show that the interaction of long-range stress fields plays a dominant role in low-medium temperature region,and dislocation slip is the main deformation mechanism.Besides,there are other microcosmic mechanisms related to softening mechanism that cannot be ignored.Based on the constitutive relationship of 2099 Al-Li alloy,the subroutine programs of ABAQUS software were used to redevelop the constitutive model.On the basis of summarizing of implicit algorithm,the UMAT subroutine programs of JC constitutive model and MZA constitutive model are written preliminarily.