Abstract：Significant strain burst phenomenon is observed during the plastic deformation of microscale metal. This work aims to develop the strain burst criteria and judging conditions for different deformation stages of microscale metal, taking single-crystal Ni micro-pillar under force loading and Au nano-pillar under displacement loading as examples. Based on the classical Hill’s stability condition in continuum plasticity theory, the criteria for the occurrence and termination of the strain burst are proposed according to the variations of kinetic energy during the deformation process of small pillars. Furthermore, the internal energy evolution of pillars during the deformation process is analyzed. Based on the simultaneous changes of kinetic energy and internal energy, the judging conditions for different deformation stages of pillars are established. Then, these theoretical developments are verified by comparing their finite element outputs with the experimental and theoretical results in literature. It is found that the proposed strain burst criteria using kinetic energy increment can effectively identify the occurrence and termination of the strain burst events, and the judging conditions based on energy changes are capable of distinguishing different deformation stages of micro- and nano-pillars. The applicability and merits of the newly proposed criteria are discussed at the end of the paper.
2019, Vol. 40 
