Study On Mechanical Properties And Fracture Behavior Prediction Of AA6061-T6 Aluminum Alloy

Aluminum alloy has the characteristics of light gravity,high specific strength,low cost and easy processing,and has long been an indispensable key structural material in the field of lightweight.However,ductile fracture often occurs during the production and service of aluminum alloy due to dynamic loading.Therefore,it is a key issue in the field of lightweight to study the mechanical behavior and fracture failure behavior of aluminum alloy under dynamic loading.Based on the above background,this study took AA6061-T6 aluminum alloy sheet as the research object,carried out the material dynamic tensile property test and ductile fracture experiment respectively,analyzed the macroscopic mechanical behavior and the microscopic mechanism of fracture behavior,and established the dynamic constitutive model and dynamic ductile fracture model by combining experiment with finite element simulation.It provides theoretical guidance for accurately predicting fracture failure behavior of materials under quasi-static and dynamic loading.The main research contents and conclusions of this paper are as follows:First,a unidirectional high-speed tensile test was carried out on AA6061-T6 aluminum alloy sheet at different strain rates(0.1-1000/s)to study the effect of strain rate on the mechanical properties of the material.The results show that the tensile strength and fracture strain of AA6061-T6 aluminum alloy are more sensitive to the strain rate.The effect of strain rate on macro and micro fracture morphology was analyzed.The modified Johnson-Cook plastic constitutive model is established and the VUMAT subroutine of the model is developed,which can accurately predict the stress-strain relationship of AA6061-T6 aluminum alloy at different strain rates.Secondly,six samples with different stress states were designed for AA6061-T6 aluminum alloy plate,and the fracture time,fracture location and stress state distribution in section of each sample were determined by the combination of ductile fracture experiment and finite element simulation.Combined with the microscopic fracture morphology of the sample and the change of stress state in different paths on the cross section,the growth behavior of the cavity under different stress states was analyzed qualitatively and quantitatively.The results show that the hydrostatic stress mainly affects the volume change of the cavity,and the maximum shear stress mainly affects the shape change of the cavity.Finally,a dynamic DF2014 uncoupled ductile fracture model was constructed based on the mechanism of nucleation,growth and polymerization of the holes,combined with Johnson-Cook ductile fracture model.The modified Johnson-Cook constitutive model and dynamic DF2014 ductile fracture model are embedded in ABAQUS/Explicit finite element analysis software to predict the mechanical response and fracture behavior of AA6061-T6 aluminum alloy sheet in dynamic perforation,and verify the reliability of the model.