Speaker: Giacomo Po
Affiliation: Mechanical and Aerospace Engineering, UCLA

Plasticity in Materials for Extreme Environments

Current and future technologies in Electric Propulsion (EP) and Pulsed Power (PP) systems demand structural materials able to withstand extreme thermomechanical environments. Depending on the design functions, the range of materials of interest in EP and PP applications includes conducting refractory metals (e.g. W, W-Re, Mo, Ta, and Re), insulating dielectric ceramics (e.g. BN and Al2O3), and high-strength copper alloys as heat sinks. These materials typi-cally experience two types of degradation, namely erosive surface effects and mechanical damage in the form of localized plasticity and fracture. Micro-engineered surfaces, such as reticulated metallic or ceramic foams directly fac-ing the plasma, can mitigate these phenomena by protecting the underlying structural component.

Understanding the plastic behavior of these micro-scale structures is of fundamental importance for designing resilient materials in severe environments. In this talk, I present discrete and continuum dis-location-based computational models of plasticity in crystalline materials at the micro-scale. Formulated in the context of continuum irreversible thermodynamics, and informed by ab-initio and atomistic simula-tions, these models predict the collective behavior of crystal dislocations in micro-scale samples, and they are systematically compared to experiments carried out at the same length scales. Simulation results guide materials design by explaining phenomena such as the interplay between size and temperature effects in bcc metals subject to uniaxial loads, and the formation of characteristic geometrically-necessary disloca-tion (GND) structures under heterogeneous loading (e.g. indentation).

About the Speaker

Giacomo Po is a Research Scientist and a Lecturer in the Mechanical and Aerospace Engineering Depart-ment at the University of California, Los Angeles (UCLA). He received his Ph.D. in Mechanical Engineering from UCLA in 2011. His research interest focuses on the mechanics of materials defects in metals and ce-ramics, with emphasis on discrete and continuum models of dislocation-based plasticity. Giacomo is the main developer of the Mechanics of Defects Evolution Library (MoDELib), a high-performance, open-source, and multi-physics framework for plasticity used by several academic institutions around the world. Since 2011, he published more than 35 articles in international journals, including Physical Review Letters, the Journal of the Mechanics and Physics of Solids, the International Journal of Plasticity, Acta Materialia, Physical Review B, The Journal of Nuclear Materials, Physical Letters, the Journal of Applied Physics, Mate-rials Theory, Computational Materials Science, Philosophical Magazine, and others.

Date/Time:
Date(s) - Oct 13, 2017
10:30 am - 12:00 pm

Location:

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