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Magnesium alloy elastoplastic behaviour under multiaxial loading conditions

Publication . Anes, Vitor; Moreira, Rogério; Freitas, Manuel; Reis, Luís

The reduction of pollution and fuel consumption is an important goal to the transportation industry. The weight reduction of vehicles has a strong effect on the reduction of greenhouse gas emissions and on the fuel consumption. Nowadays magnesium alloys tend to replace steels and aluminium alloys in order to go further in the structural weight reduction. Magnesium alloys are greatly appreciated due to their high strength-to-weight ratio, stiffness, and low density. However, magnesium alloys can exhibit complex types of cyclic plastic deformation, like twinning and de-twinning effect. Recent researches indicate that these type of plastic deformation cannot be fully characterized using the typical tools used in steels, thus it is required a new approach to fully capture their fatigue cyclic deformation and plasticity. This research aims to obtain a phenomenological cyclic elastic-plastic model that captures the cyclic deformation of magnesium alloys under multiaxial loading conditions. In order to validate the achieved model, the numeric estimates were correlated with the experimental data and with the estimates of the Jiang & Sehitoglu plasticity model. The results show that the developed model estimates are in agreement with the experimental data.

2018-07Conference object

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Evaluation and numerical modeling of phenomenological approach for AZ31B-F magnesium alloy under multiaxial fatigue

Publication . Moreira, R.; Anes, Vitor; Freitas, M. De; Reis, L.

Magnesium alloys have been attractive to use in structural components due to their high strength to weight ratio, low density and high damping capacity. However, magnesium alloys show peculiar plastic deformation mechanisms under cyclic loads (twinning and de-twinning) that causes the asymmetric material behaviour and limits their use in structural components. Recent researches indicate that this type of plastic deformation mechanism cannot be fully characterized using the typical tools used in steels. Therefore, the phenomenological Hypo-strain (HYPS) model has been developed to capture the asymmetric behaviour of magnesium alloys under uniaxial and multiaxial loadings. This study aims to evaluate the phenomenological Hypo-strain approach for AZ31B-F magnesium alloy and to implement the HYPS model on an external subroutine (UMAT) to run on Abaqus. The goal is to reach a numerical tool that can be used to accurately describe the cyclic elastic-plastic behaviour of magnesium alloys in synergy with finite element packages. In order to characterize the cyclic behaviour of AZ31B-F magnesium alloy, experimental tests were performed considering proportional and non-proportional loadings. To evaluate the implemented model in UMAT, these results were correlated with the experiments and with the analytical HYPS approach. Moreover, the estimates were also correlated with the Armstrong-Frederick model available on Abaqus/Standard 6.14 library. The results have shown that the HYPS model was successful implemented on the UMAT subroutine with a good correlation between experimental tests and the HYPS model. Some remarks between the HYPS and Armstrong-Frederick models are drawn.

2020Conference object

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