| Along with the wide application of 5083 aluminum alloy in manufacturing, especially the development of high-speed train and ship industry,5083 aluminum alloy must has good mechanical properties under the condition of the high speed collision and large plastic deformation. At the same time, materials parameters, such as yield stress and work hardening rate, are bound to change under different loading rates and temperatures, and so on. So, the research and analysis of mechanical properties of 5083 aluminum alloy under dynamic loading has important significance at the design of engineering structure and the numerical calculation of collision problem.In this paper, aiming at 5083 aluminum alloy, the stress-strain curves have been obtained by wide strain rates (2×10-4/s～7×103/s) under quasi-static, middle and high strain rates loading in tensile and compression experiments, through the MTS material testing machine, dynamic INSTRON materials tester and split Hopkinson test system. The experimental results show that the material have the same stress-strain curves in the same experimental conditions. But in the strengthening stage, tensile curves are always lower than compression curves. The yield stresses under different tensile and compression strain rates are basically same, and the yield stress along with the change of strain. When the loading strain rate is less than 10/s, the yield stress show negative strain rate effect, then with the increasing of strain rate, the yield stress present positive strain rate effect. In the yield stage, there is an obvious form of strain hardening of power rate regulation, strain hardening rate decreases with strain rate, presenting the typical characteristics of FCC metals.Based on the conclusions of experiment, this paper summarized a variety of 5083 aluminum alloy used to describe the constitutive relation model under the impact loading in recent years. Aiming at the most commonly Johnson-Cook (JC) model, describing the dynamic constitutive relation for 5083 aluminum alloy, is improved. Because the model does not consider the damage mechanism of the microscopic level, by analysis the dynamic damage mechanism, and combining the study of the fracture mechanism of ductile metal damage theory and micro aspects, the dynamic softening is reasonable explained by theoretical mechanism of 5083 aluminum alloy. By comparing of the experimental curves and the model curves, the fitting is good. It shows that the proposed model has good applicability. The research can provide effective science basis, the analysis model and the necessary reference for the engineering application of 5083 aluminum alloy.During the research process, although the Johnson-Cook constitutive model has been found that the form is simple and less physical parameters, but this model belongs to a half experience and half physical constitutive model. The disadvantage of the model is that lack of description of mechanical behavior of work hardening rate changes with strain and strain rate. So, by the system analysis of plastic flow behavior of the FCC polycrystalline materials under wide strain rates, this paper discusses the experimental phenomenon of abnormal yield behavior and strain hardening rate reduces of 5083 aluminum alloy. The deformation mechanism has been produced to be the competition of two phase alloy element under different strain rates. Based on the dislocation dynamics concept and thermal activation theory, Copley and Kear intensive model is introduced that shows the strengthening mechanism of metal. At last, reconstructing the Zerilli-Armstrong constitutive model, through the comparison of the experimental results and the fitting curves, this model has been proved a better fitting effect than Johnson-Cook constitutive model. Compared with the experimental curves and the model curves, the fitting is good. It shows that the model has better prediction of the plastic flow stress ability of 5083 aluminum alloy. |
PDF Full Text Request