A Monte Carlo model for the intermittent plasticity of micro-pillars

Earlier compression experiments on micrometre-sized aluminium pillars, fabricated by focused-ion beam milling, using a flat-punch nanoindenter revealed that post-yield deformation during constant-rate loading was jerky with interspersing strain bursts and linear elastic segments. Under load hold, the pillars crept mainly by means of sporadic strain bursts. In this work, a Monte Carlo simulation model is developed, with two statistics gathered from the load-ramp experiments as input, to account for the jerky deformation during the load ramp as well as load hold. Under load-ramp conditions, the simulations successfully captured other experimental observations made independently from the two inputs, namely, the diverging behaviour of the jerky stress-strain response at higher stresses, the increase in burst frequency and burst size with stress and the overall power-law distribution of the burst size. The model also predicts creep behaviour agreeable with the experimental observations, namely, the occurrence of sporadic bursts with frequency depending on stress, creep time and pillar dimensions.