The electro-mechanical control of element NiTi shape memory alloy strip while bending, based on thermal analysis evidenc
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The electro‑mechanical control of element NiTi shape memory alloy strip while bending, based on thermal analysis evidence Sonia Degeratu1 · G. E. Subțirelu1 · A. Rotaru2,3 · N. G. Bîzdoacă4 · P. Rotaru5 Received: 12 April 2020 / Accepted: 4 August 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract This paper presents an experimental investigation of a commercial shape memory alloy strip consisting of nickel and titanium (NiTi SMA), which correlates the thermal properties (phase transitions) with the electrical and mechanical properties of the material, allowing to be used for control applications in engineering. The bending performances of the SMA strip at different values of the activation electric current, during heating process, are also investigated. By using the differential scanning calorimetry (DSC) experiments, the thermal characteristics of the SMA strip were identified. The results of this thermal analysis were the basis for determining the equilibrium temperature, entropy and force developed by the SMA strip during the phase transformation. For the study of the SMA strip, the authors have developed an experimental platform, which uses a portable reconfigurable I/O (RIO) device and LabVIEW graphical programming environment for the measurement, testing and rapid control of parameters, and a piezo-film sensor for controlling of SMA strip movement. The real-time measurements and acquired waveforms are displayed on a PC screen, and the data associated with these waveforms are stored for later use, i.e. for applications in safety engineering like the fire extinguishing control, where very short response/activation times are required. Keywords NiTi alloy · DSC · Piezoelectric sensor · SMA strip · Virtual instrumentation
Introduction
* A. Rotaru [email protected]; [email protected] 1
Department of Electromechanics, Environment and Applied Informatics, Faculty of Electrical Engineering, University of Craiova, Blvd. Decebal, Nr. 107, 200440 Craiova, Romania
2
Department of Biology and Environmental Engineering, Faculty of Horticulture, University of Craiova, Str. A.I. Cuza, Nr. 13, 200585 Craiova, Romania
3
Department of Chemical Thermodynamics, Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, Str. 202 Independentei, Nr. 202, 060021 Bucharest, Romania
4
Department of Robotics and Mechatronics, Faculty of Automatics, Computers and Electronics, University of Craiova, Blvd. Decebal, Nr. 107, 200440 Craiova, Romania
5
Department of Physics, Faculty of Sciences, University of Craiova, Str. A.I. Cuza, Nr. 13, 200585 Craiova, Romania
NiTi shape memory alloys (SMAs) are functional materials characterized by a thermoelastic martensitic transformation between two distinct solid phases: B2 structured austenite (A) and B19′ structured martensite (M). The low-temperature phase, the martensite, is the relatively soft and easily deformable phase with a twinned molecular structure, while the high-temperature parent phase, the austenite, is the stronger phase with an orde
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