Assessment of SMA Electrical Resistance Change during Cyclic Stretching with Small Elongation

Abstract

In this article, changes in NiTi alloy (Flexinol) electrical resistance during cyclic stretching with small elongation were investigated. A dedicated test stand consisting of motorized vertical test stand, force gauge, and electric resistance measuring device with an accuracy of 0.006 Ω was developed. A dedicated control algorithm was developed using LabVIEW software. Changes in electrical resistance were investigated for the 0.1 mm Flexinol wire with length of 120 mm. Testing was performed in the elongation range between 0.25% and 1.5% in martensite phase. Tested samples were subjected to 30 stretching cycles with a movement speed of 10 mm/min. Obtained results show that the cyclic stretching of Flexinol wire reduces its electrical resistance with each stretching cycle. Moreover, it was noted that changes in Flexinol electrical resistance during cycling stretching depend on the assumed elongation and number of the already performed stretching cycles. The observed electrical resistance change decreases with each stretching cycle. Thus, the observed changes are greater during the first stretching cycles. For elongations exceeding 1%, the Flexinol electrical resistance in the first stretching cycle increases. In each subsequent cycle, electrical resistance decreases, as in the case of the smallest value of assumed elongation. In almost all tested cases (except in the case with 1.5% of assumed elongation), Flexinol electrical resistance after 30 stretching cycles was smaller than before the test.

Determination of Thin NiTi Wires’ Mechanical Properties during Phase Transformations

“…There are three main crystal structures in NiTi alloys: twinned martensite, detwinned martensite and austenite; in some commercially produced alloys, a rhombohedral (R) phase may also be observed [ 22 , 23 ]. The crystal structures existing in NiTi alloys are different for their mechanical and physical properties, including their electrical resistance [ 24 ]. This makes it possible to identify phase transformations occurring in NiTi alloys, due to the fact that the electrical resistance is an easily measurable [ 25 ].…”

Accurate sensorless displacement control based on the electrical resistance of the shape memory actuator

“…These studies focus on a SMA that undergoes a constant stress value. SMA electrical resistivity is affected by several factors such as stress, deformation, temperature, and phase transformation (Barati et al, 2017;Nakshatharan and Dhanalakshmi, 2014;Nova´k et al, 2008;Ra ˛czka et al, 2013;Raparelli et al, 2002;S1awski et al, 2021). The models representing the relationship between the SMA electrical resistance and SMA displacement are presented in Kumar and Lagoudas (2008), Lynch et al (2016), andDutta Ghorbel (2005).…”

The Application of Microelectromechanical Systems (MEMS) Accelerometers to the Assessment of Blast Threat to Armored Vehicle Crew

“…The conditions in which the research takes place can lead to wires within the equipment becoming disconnected, resulting in the disruption of signal canvassing and loss of data. In addition, research objects and measuring systems can be destroyed [ 1 , 2 , 3 , 4 , 5 , 6 , 11 , 12 , 13 , 14 , 15 ].…”