Prediction of failure under different stress states and loading conditions for shear-sensitive materials

Anticipating materials’ fracture in different operative scenarios is fundamental for a safe and robust design. This doctoral thesis is focused on investigating the fracture response of the aerospace aluminum alloy Al2024-T351, and it aims to propose a material model able to capture its behavior comprehensively. An extensive experimental campaign has been conducted to probe material failure under various loading conditions, from shear-dominant loadings to high stress triaxiality governed states. The material performance under extreme conditions involving high strain rates, high pressures, and variable temperatures has also been addressed by performing Taylor-anvil impact tests and Flyer-plate impact tests. The role of the microstructural features in determining the damage mechanisms has been examined by adopting SEM in-situ techniques and conducting post-mortem investigations on the recovered samples. An appropriate material model has been developed based on the experimental data to account for the material shear-sensitivity. The damage behavior of the alloy has been modeled with the recently proposed Plasticity Damage Self-Consistent (PDSC) model, which incorporates the effects of both stress triaxiality and the Lode parameter on damage. Although the model has been developed in the context of Continuum Damage Mechanics, it can predict the interplay of different damage mechanisms (void growth, intervoid sheeting, and shearing). The capability of the model to predict failure under various stress states and non-proportional loading paths has been exploited, and an extension of the model has been proposed to account for the competing effects of strain rate and temperature on damage rate evolution in dynamic loading. Moreover, the applicability of the PDSC model on additively manufactured materials has been addressed, exemplified by a case study on the L-PBF alloy AlSi10Mg.