Browsing by Author "Freitas, M. De"
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- Evaluation and numerical modeling of phenomenological approach for AZ31B-F magnesium alloy under multiaxial fatiguePublication . 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.
- Evaluation of a phenomenological elastic‐plastic approach for magnesium alloys under multiaxial loading conditionsPublication . Anes, Vitor; Reis, Luis; Freitas, M. DeMagnesium alloys are greatly app reciated due to their high strength to weight ratio, stiffness, and low density; however, they can exhibit complex types of cyclic plasticity like twinning, de‐twinning, or Bauschinger effect. Recent studies indicate that these types of cyclic plastic deformations cannot be fully characterized using the typical tools used in cyclic characterization of steels and aluminium alloys; thus, it is required new approaches to fully capture their cyclic deformation and plasticity. This study aims to propose and evaluate a phenomenological cyclic elastic‐plastic approach designed to capture the cyclic deformation of magnesium alloys under multiaxial loading conditions. Series of experimental tests were performed to characterize the cyclic mechanical behaviour of the magnesium alloy AZ31BF considering proportional loadings with different strain amplitude ratios and a nonproportional loading with a 45° phase shift. The experi mental results were modulated using polynomial functions in order to implement a cyclic plasticity model for the AZ311BF based on the phenomenological approach proposed. Results show good correlations between experiments and estimates.