Abstract:

One of the holy grails of computational material science is to satisfactorily predict metal plasticity from fundamental dislocation physics. Currently, discrete dislocation dynamics (DDD) is still limited to small quantities of dislocations irrelevant to most engineering applications, and slip-system based crystal plasticity (CP) lacks details of dislocation physics. Continuum dislocation dynamics (CDD) has received considerable interests for bridging the gap at the meso-scale. Recently, an exact evolution equation for an “all-dislocation” density (ADD) that represents continuum dislocation quantities over both space and dislocation-character domains has been developed by the present author. For coarse-grained simulations, ADD is superior to the Nye tensor or other representations of geometrically necessary dislocations (GND), since the statistically stored dislocation (SSD) contents which are important for dislocation dynamics will be preserved. In this talk, this new approach of CDD based on ADD will be presented.

Biography:

Professor Alfonso Ngan is Kingboard Professor in Materials Engineering and Chair Professor of Materials Science and Engineering at the University of Hong Kong. His interests include novel stimuli-responsive materials, material defects and their modelling, and nanomechanics, including applications to biological systems. His main contributions include a method for correcting viscoelastic effects in nanoindentation measurements of soft materials which has been converted into a Chinese national standard, understanding of stochastic deformation behaviour in small crystals, an exact formalism of continuous dislocation kinematics, and the discovery of a novel class of metal hydroxides/oxides as stimuli-responsive actuating materials. His research-related honours include the Rosenhain Medal from the Institute of Materials, Minerals and Mining, UK (2007), Changjiang Professorship from the Chinese Ministry of Education (2019), and Guanghua Engineering Science and Technology Prize of the Chinese Academy of Engineering (2020). He is currently an associate editor of the International Journal of Plasticity, and an International Fellow of the Royal Academy of Engineering in the UK.

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