STUDY ON THE МЕCHANICAL PROPERTIES OF FUNCTIONALLY GRADED SHAPЕ MEMORY ALLOY NANOBЕAMS

Abstract

Functionally graded shape memory alloys (FG-SMA) have the properties of both functionally graded materials and shape memory alloys (SMA), so they have been widely used in aerospace, biomedical, and micro electro mechanical systems(MEMS). The influence of surface effects on the mechanical properties of microstructure is very significant when the scale reaches the nanometer scale. In order to study the effect of surface effects on the mechanical properties of FG-SMA, based on the bending theory and Gurtin-Murdoch surface elasticity theory, the phase transition mechanical model considering the effects of tensile and compressive asymmetry and temperature on FG-SMA nanobeams was developed considering the surface effects. The influence of functionally graded index, load, temperature, and tensile-compression asymmetry coefficient on the mechanical properties of FG-SMA nanobeams was analyzed. It is shown that bending moment and functionally graded index have significant effects on the cross-sectional response, while temperature and tensile asymmetry coefficient have fewer effects on them. Ignoring the influence of surface effect will underestimate the flexural resistance of FG-SMA nanobeams. When the bending moment reaches a certain range, the neutral axis deflection of FG-SMA nanobeams is not much affected by surface effects. The results of the study provide a basis for the design and application of FG-SMA nanobeams in the field of MEMS.

Keywords

• Functionally graded shape memory alloys
• Micro electro mechanical system
• Surface effect
• Gurtin-Murdoch surface elasticity theory
• Phase transition