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Study on strain rate dependent constitutive and low stress triaxial fracture behavior of 6005 aluminum alloy

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Document pages: 14 pages

Abstract: In order to study the dynamic and fracture behavior of 6005 aluminum alloy under different strain rates and stress states, various tests (tensile test under different strain rates and tensile shear test under five stress states) were carried out by mechanical test and simulation (MTS) and split Hopkinson pull rod (SHTB). The numerical simulation based on finite element method (FEM) is carried out by ABAQUS standard to obtain the actual stress triaxial and fracture equivalent plastic strain. The tensile test results of 6005 aluminum show that the strain rate is obviously dependent on the rate. The simulation results show that there is a non monotonicity between fracture strain and stress triaxiality. The equivalent plastic strain decreases to a minimum and then increasesin the stress triaxiality range from 0.04 to 0.30. A simplified Johnson-Cook (JC) constitutive model is proposed to depict the relationship between the flow stress and strain rate. What is more, the strain-rate factor is modified using a quadratic polynomial regression model, in which it is considered to vary with the strain and strain rates. A fracture criterion is also proposed in a low stress triaxiality range from 0.04 to 0.369. Error analysis for the modified JC model indicates that the model exhibits higher accuracy than the original one in predicting the flow stress at different strain rates. The fractography analysis indicates that the material has a typical ductile fracture mechanism including the shear fracture under pure shear and the dimple fracture under uniaxial tensile.

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