Seminars

Abstract: This work investigates the impact of microinertia on plastic localization, void growth, and coalescence in ductile porous materials subjected to high strain rates. For that purpose, we have performed finite element calculations on a flat double-notched specimen subjected to dynamic plane strain tension. The simulations employ three distinct approaches to model the mechanical behavior of the porous aggregate: (1) discrete voids within a matrix material governed by von Mises plasticity; (2) homogenized porosity represented using standard quasi-static Gurson-Tvergaard plasticity; and (3) homogenized porosity described with Gurson-Tvergaard plasticity extended by Molinari and Mercier (2001) to account for microinertia effects. The porous microstructures used in the simulations are representative of additive manufactured metals, featuring initial void volume fractions varying between 0.5% and 4%, and pore diameters ranging from 30 μm to 150 μm (Marvi-Mashhadi et al., 2021). The applied tensile velocities ranged from 100 m/s to 1000 m/s, producing strain rates between 105 s−1 and 106 s−1, and stress triaxiality values spanning from 4 to 30. The simulations with discrete voids validate the calculations performed using homogenized porosity and microinertia effects, demonstrating that higher strain rates and larger pore sizes lead to slower void growth and a delayed, regularized plastic localization. Conversely, the standard Gurson-Tvergaard model shows notable mesh sensitivity and fails to describe the influence of the loading rate on plastic localization. Ultimately, the comparison between finite element models with discrete voids and those with homogenized porosity illustrates the stabilizing effects of porous microstructure and multiscale inertia on dynamic plastic flow, while also highlighting the strengths of the constitutive model introduced by Molinari and Mercier (2001) for simulating engineering problems involving porous ductile materials subjected to high-velocity impacts.

Bio: José A. Rodríguez-Martínez is an Associate Professor in the Department of Continuum Mechanics and Structural Analysis at Universidad Carlos III de Madrid and the head of the Nonlinear Solid Mechanics research group. He holds a PhD in Mechanical Engineering from Universidad Carlos III de Madrid and a PhD in Mechanics of Materials from Université Paul Verlaine de Metz. His research on the flow and fracture behavior of ductile materials under high strain rates has secured several million euros from national and international agencies, including the European Research Council and the Spanish Ministry of Science and Technology, which supported the establishment of Spain’s first hypervelocity center at Universidad Carlos III de Madrid. Dr. Rodríguez-Martínez has authored over 90 peer-reviewed articles in international journals and has delivered numerous invited lectures and seminars at international conferences, universities, and research centers. He is an Associate Editor of Mechanics of Materials and the Journal of Dynamic Behavior of Materials and serves on the Editorial Advisory Board of the International Journal of Plasticity. Furthermore, he is the secretary of the Spanish Society of Applied and Theoretical Mechanics, a member of the Advisory Board of EUROMECH, and the coordinator of the Spanish Network on Multiscale Mechanics of Innovative Engineering Materials.