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- 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.
- Magnesium alloy elastoplastic behaviour under multiaxial loading conditionsPublication . Anes, Vitor; Moreira, Rogério; Freitas, Manuel; Reis, LuísThe 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.
- The damage scale concept and the critical plane approachPublication . Anes, Vitor; de Freitas, M.; Reis, L.Critical plane criteria seek the plane in which their damage parameter has its maximum value. On this plane, the fatigue damage of both normal and shear stresses is updated to the same damage scale by a constant, typically based on material normal/shear fatigue limits. This paper focuses on the damage scale concept under a stress-based critical plane standpoint, and the main objective is to evaluate its performance. To perform this study, data from the high strength steel 42CrMo4 were considered. Five proportional loading paths with different stress amplitude ratios and stress levels were analysed using 2 different multiaxial fatigue criteria, namely, the Findley critical plane model and the stress scale factor equivalent shear stress. Results show that the damage scale between normal and shear stress components varies accordingly to the loading plane direction considered.