Bending of shape memory alloy nanobeams incorporating surface effects based on the Euler-Bernoulli beam model

Abstract

Shape memory alloys (SMA) are widely used in micro-electro-mechanical systems due to shape memory effect and hyperelasticity. The surface effects on mechanical properties cannot be ignored because of their small structure size. Based on Euler Bernoulli beam theory and Gurtin-Murdoch surface elasticity theory, the influence of tension-compression asymmetry factors on SMA beams is considered, and a phase transformation mechanical model of SMA nanobeams considering surface effects is established. The effects of surface effects on load, curvature and neutral axis displacement are investigated The study demonstrates that regardless of whether considering the surface effect, the neutral axis displacement initially increases and subsequently decreases with the growth of the dimensionless bending moment. The neutral axis displacement of nanobeams can be significantly affected by taking surface effects into account. When considering the surface effect, the difference in neutral axis displacement of the nanobeam increases as the nanobeam’s size diminishes. Neglecting surface effects will underestimate the bending stiffness of the microbeam.