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Strain gradient plasticity: Numerical modeling and fracture assessment

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Abstract Experiments have consistently shown that metallic materials display strong size effects at the micro and sub-micron scale, with smaller being harder. As a result, a significant body of research has been devoted to model this size-scale dependent plastic phenomenon. At the continuum level, phenomenological strain gradient plasticity (SGP) formulations have been employed to extend plasticity theory to small scales. Grounded on the physical notion of geometrically necessary dislocations (GNDs, associated with non-uniform plastic deformation), SGP theories relate the plastic work to both strains and strain gradients, introducing a length scale in the constitutive equations. In this talk, particular attention will be paid to the impact of GNDs in a specific field beyond small-scale applications: fracture and damage modeling. Thus, independent of the size of the cracked specimen, gradient-enhanced modeling of crack tip deformation appears imperative as the plastic zone adjacent to the crack tip is – generally – physically small and contains strong spatial gradients of plastic deformation. By means of different SGP theories and their ad hoc numerical framework, the influence of GNDs is examined in a wide range of areas where they are expected to play a major role: crack tip fields characterization, cohesive zone modeling of crack propagation, hydrogen diffusion towards the fracture process zone, environmentally assisted cracking or probabilistic assessment of cleavage fracture, among others.

About the speaker Emilio Martínez Pañeda earned a 5 year B. Eng. & M. Eng. degree in Industrial Engineering from the University of Oviedo (Spain) in 2011 and an MSc degree in Structural Engineering from the University of Granada (Spain) in 2012. He is currently a research engineer and PhD candidate at the University of Oviedo working under the supervision of Prof. Betegón. Martínez Pañeda carries out research activities in the fields of mechanics of materials and computational solid mechanics, with particular emphasis on the modelization of size effects in metal plasticity and fracture and damage assessment. He has held visiting scholar positions at several Universities such as the Technical University of Denmark (host: C. Niordson), the University of Luxembourg (host: S. Bordas) or the University of Cambridge (host: N. Fleck) and he is actively involved in many international collaborations. Martínez Pañeda is currently a member of the European Structural Integrity Society (ESIS), the European Community on Computational Methods in Applied Sciences (ECCOMAS) and the International Association for Computational Mechanics (IACM). He has delivered several invited talks and seminars in various international conferences and research institutions. He is author or co-author of several scientific publications in international referred journals in the field of solid mechanics.

This talk is part of the Engineering Department Bio- and Micromechanics Seminars series.

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