Capturing the stochastic mechanical behavior of micro and nanopillars

Experimental evidence has illustrated that micropillar deformation is highly stochastic, as the stress-strain curves are manifested by multiple strain bursts. Although initial theoretical works employing gradient plasticity can predict the stress-strain response of individual pillars, they cannot capture the stochastic effects observed for multiple same diameter specimens. This article presents simulations that are not only in precise qualitative and quantitative agreement with experimental stress-strain curves for varying diameter pillars, but can also account for the observed stochasticity in same diameter micropillars. This is accomplished by implementing gradient plasticity within a cellular automaton, while allowing the yield-stress to randomly vary within the micropillar. In concluding, it is shown that the aforementioned numerical code can also capture the stress drops and size dependent strengthening observed in metallic glass nanopillars.