Modelling and experimental investigation of geometrically graded NiTi shape memory alloys

Abstract

To improve actuation controllability of a NiTi shape memory alloy component in applications, it is desirable to create a wide stress window for the stress-induced martensitic transformation in the alloy. One approach is to create functionally graded NiTi with a geometric gradient in the actuation direction. This geometric gradient leads to transformation load and displacement gradients in the structure. This paper reports a study of the pseudoelastic behaviour of geometrically graded NiTi by means of mechanical model analysis and experimentation using three types of sample geometry. Closed-form solutions are obtained for nominal stress–strain variation of such components under cyclic tensile loading and the predictions are validated with experimental data. The geometrically graded NiTi samples exhibit a distinctive positive stress gradient for the stress-induced martensitic transformation and the slope of the stress gradient can be adjusted by sample geometry design.

Buckling analysis of functionally graded nanobeams based on a nonlocal third-order shear deformation theory

“…Using Eqs. (14), (15), and (26)-(28), the constitutive relations of the nonlocal FG Reddy nanobeam theory can be obtained as follows: …”

“…With the rapid development of nanostructures, FGMs are widely used in microstructures and nanostructures such as microswitches, micropiezoactuator, thin films [7][8][9][10][11][12][13][14][15][16][17][18][19][20], and micro/nanoelectromechanical systems (MEMS and NEMS) [21][22][23][24][25][26][27][28][29]. Jia et al [4] studied the forced vibration of nonhomogeneous FG microswitches under combined electrostatic, intermolecular forces, and axial residual stress.…”

Pseudoelastic behaviour of perforated NiTi shape memory plates under tension

“…During (1 ) t t σ α σ σ − ≤ < , section II is transformed to martensite with A→M transformation initiating at the middle and propagating toward the top and bottom ends of this section. [37,38], L ∆ during this period can be written as:…”

A Combined Analytic, Numeric, and Experimental Investigation Performed on NiTi/NiTiCu Bi‐Layer Composites under Tensile Loading

“…Furthermore, thermal hysteresis is also reduced due to its superior properties . So far, many investigations have been conducted on the analytical modelling of functionally graded NiTi‐based components as well as multilayer thin films . Generally, analytical models predict the global response of SMA components under tensile loading and bending.…”