Linking Quantum and Continuum Mechanics to Study Mechanical Response of Materials: Stressed, Shocked, and Embrittled Metals

Emily A. Carter, California NanoSystems Institute, University of California

Mechanical properties of bulk solids are affected not only by macroscopic external loads, but also by chemical reactions, typically at surfaces and interfaces. For example, impurities in metals often coalesce at grain boundaries, leading to weakening of the sample under stress. Atmospheric corrosion is another example that, when combined with external loads, leads to stress-corrosion cracking. These are inherently multiscale phenomena, where the chemistry occurring at the atomic scale profoundly affects the mechanical properties at the micron to millimeter scale. We are developing two basic strategies of multiscale modeling, which differ in how the coupling between scales is accomplished: either one generates atomic scale information in advance, which then is used to provide the constitutive laws that determine the materials response at the higher-length scale (microns to mm), or one directly couples both scales, where on the fly the needed information from the atomic scale is provided to the macroscopic model, which, in turn, provides real-time feedback to the atomic scale. Thus far, we are coupling various forms of periodic density functional theory (DFT) at the atomic scale to a finite element continuum mechanics description of the coarser scale. We will discuss the following applications of our multiscale simulation algorithms: (i) nanoindentation of aluminum, predicting the onset of plasticity; (ii) shock-induced phase transformations in iron that produce a complex microstructure; and (iii) environmentally-induced cracking of steel due to hydrogen embrittlement.

This work is done in collaboration with Robin Hayes, Matt Fago, Kyle Caspersen, Adrian Lew, Santiago Serebrinsky, De-en Jiang, and Michael Ortiz and is funded by the U.S. Department of Defense Multidisciplinary University Research Initiative, the U.S. Army Research Office, and by the U.S. Department of Energy Accelerated Strategic Computing Initiative.

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