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Multiscale modelling of material failure

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Date: Thursday 28 September
Venue: EN405 Hawthorn Campus

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A solid specimen subject to a sufficiently high mechanical load will eventually fail resulting in fragmentation. A complete understanding of material fragmentation is extremely challenging, involving the creation of new surfaces, plastic flow, thermal conductivity, and non-equilibrium thermodynamics.

Numerical simulation is the most promising method for analysing these processes. Molecular Dynamics (MD), which is essentially exact for a prescribed forcelaw, provides useful pseudo-experimental data with which to gain mechanistic understanding of failure and can provide improved constitutive relations. However, studying failure in materials of interest to the engineer is inherently a continuum problem; an atomistic approach would require an impossibly large number of particles. Continuum mechanics in turn is incomplete – surface tension for example, must be added in. Furthermore, standard tools such as Finite Element Modelling run into numerical problems once failure is reached (mesh entanglement etc.).

Smooth Particle Applied Mechanics (SPAM) uses particles to solve the conservation laws of continuum mechanics and thus contains its own failure mechanism (the separation of particles)[1]. It appears to be a highly useful tool for analysing material failure (solids and liquids), particularly when used in conjunction with MD.

In this presentation a prototypical model of material fragmentation - the penetration of a plate by a fast moving ball in 2 dimensions – is explored using both SPAM and MD. MD is used to generate pseudo-experimental data for comparison with the continuum model, which is carefully parameterised (equation of state, bulk and shear moduli, yield strength and tensile strength) from the atomistic pair potential using statistical mechanical methods.

[1] W. G. Hoover, Smooth Particle Applied Mechanics, Advanced Series in Nonlinear Dynamics, Volume 25, (World Scientific, Singapore, 2006).


About the Speaker

Dr. Travis joined the Department of Materials Sceince and Engineering at Sheffield University in 2003 from the University of Bradford, where he was the A. H. Marks Lecturer in Physical Chemistry 2000-2. Before that he undertook postdoctoral appointments at Imperial College (with Dr David Nicholson), North Carolina State and Cornell Universities (with Prof Keith Gubbins) and the Australian National University (with Prof Denis Evans). He obtained both his PhD and BSc in Chemistry from UMIST, where he also won the Reynolds Prize, UMIST´s premier undergraduate prize.

Contact Information: Dr. Federico Frascoli