| Aluminum alloy, as a kind of structural material, is widely used in construction, traffic, sports activities, packaging, transportation and aerospace industries. Material, here is the aluminum alloy, will deform at a high speed during the rapid prototyping and structural collision, and the material parameters, such as the yield stress at high-speed deformation, ultimate strength and elongation, will change with the strain-rates and temperatures. The effects of wide range of strain, strain-rate and temperature on the flowing stress of the material must be considered when the dynamic mechanical property of the material is researched under the conditions of large strain, high strain-rate and high temperature. Therefore, it is of great significance for the analysis of impact problems and design of engineering structure to analyze the response of engineering structure under the impact loading and to study the strain-rate dependent mechanical properties of aluminum alloy.In this paper, the mechanical properties of5083H111aluminum alloy, under the quasi-static tensile and shock compressive and tensile conditions, are researched experimentally by MTS testing machine, split Hopkinson impact testing system and INSTRON dynamic material testing machine. In addition, the impact mechanical properties of6005aluminum alloy are also carried out by some experimental studies. The tensile and compressive stress-strain curves of5083H111and6005aluminum alloys over a wide range of strain rates, obtained by experiments, are used to discuss the effect of the change of strain-rate on the mechanical properties of aluminum alloy. Experimental results of INSTRON dynamic testing show that5083H111aluminum alloy exhibits a certain strain-rate sensitivity, V-typed rate-dependence and dynamic toughening at the prescribed range of strain rates. It is concluded that the V-typed rate-dependence of5083H111aluminum alloy is caused by the collective contributions of damage and thermal softening (which can be taken as softening factors), and viscous drag and strain rate hardening (which can be taken as hardening factors).The strain-rate and strain dependence of the logarithmic strain rate sensitivity coefficient λ and the tangent modulus E, are analyzed by combining with the INSTON tensile test data of5083H111aluminum alloy at a range of strain-rate2×10-4～4×102s-1. And then a dynamic constitutive model (VJC model), modified from the Johnson-Cook model, is established to describe reasonably the dynamic tensile behavior of5083H111aluminum alloy at a wide range of strain-rate. In the VJC model, the flow stress σ(ε,ε) is composed of two parts called as the strain-rate dependency σ(ε) and strain dependency σ(ε). The model reflects reasonably the V-typed rate-dependence of5083H111aluminum alloy over a lower range of strain-rate, and the predicted and experimental results are consistent. Moreover, the model can be applied to describe the Hopkinson tensile and compressive mechanical behavior under the impact at medium and high strain-rates. In addition, combined with the logarithm strain-rate sensitivity coefficient β of failure strain, the prediction equation of tensile failure strain is provided, and the predicted results are basically consistent with the experimental results.Referred to the UMAT subroutine compiled by Lu Jianfeng about the Johnson-Cook model, applied for ABAQUS finite element software, the UMAT subroutine of the VJC model herein is wrote out by the Fortran language, and imported into the ABAQUS finite element software. And then, in this paper, the INSTRON dynamic tensile experiment and Hopkinson impact tensile and compressive experiments of5083H111and6005aluminum alloys are simulated by the ABAQUS finite element software, and the results show that the finite element simulations agree with the experimental data, which illustrates that the dynamic (impact) mechanical behavior of aluminum alloy can be described very well by the VJC model obtained in this paper. |
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