Reconstruction of Heat Sources Induced in Superelastically Loaded Ni-Ti Wire By Localized Deformation Processes
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RESEARCH PAPER
Reconstruction of Heat Sources Induced in Superelastically Loaded Ni-Ti Wire By Localized Deformation Processes A. Jury 1,2,3,4 & X. Balandraud 4 & L. Heller 1,2 & P. Šittner 1,2 & M. Karlik 3,5 Received: 22 October 2019 / Revised: 10 July 2020 / Accepted: 23 July 2020 # Society for Experimental Mechanics 2020
Abstract Background Shape memory alloys (SMAs) are phase transforming materials featuring strong thermomechanical couplings. Infrared thermography and heat source reconstruction (HSR) enable to track the calorific signature of deformation processes. Objective The objective was to characterize the transformation processes in a superelastic nickel-titanium SMA wire subjected to a force-controlled superelastic tensile cycle. Methods In-situ recorded thermographs were converted into spatiotemporal maps of heat sources using an in-house developed post-processing method based on the heat diffusion equation resolved numerically for unknown heat sources. Results Sequentially appearing patterns of localized transformation events of four types were identified and associated with martensite bands nucleations and their subsequent merging upon tensile loading. Analogically, the events associated with austenite bands nucleations and their subsequent merging were identified upon unloading. In addition, weak heat sources observed before and after the localized transformation events were associated with the homogeneous martensitic transformation. Conclusions The intrinsic dissipation heat associated with the nucleation and merging events is estimated to be ~ 25% of the released/absorbed latent heat. Keywords Infrared thermography . Heat effect . Material characterization . Shape memory alloy . Superelasticity . Thermal diffusivity
Introduction Shape memory alloys (SMAs) are smart materials that exhibit several attractive thermomechanical properties such as shape
* X. Balandraud [email protected] 1
Nuclear Physics Institute of the CAS, Rež 130, 250 68 Husinec, Czech Republic
2
Institute of Physics of the CAS, Na Slovance 1992/2, 18221 Prague, Czech Republic
3
Faculty of Nuclear Sciences and Physical Engineering, Department of Materials, Czech Technical University in Prague, Trojanova 13, 120 00 Prague 2, Czech Republic
4
Université Clermont Auvergne, CNRS, SIGMA Clermont, Institut Pascal, Campus Universitaire des Cézeaux, F-63000 ClermontFerrand, France
5
Faculty of Mathematics and Physics, Department of Physics of Materials, Charles University, Ke Karlovu 5, 121 16 Prague 2, Czech Republic
memory effects, superelasticity and high damping capacity [1–3]. These macroscopic properties originate from a diffusionless solid-solid phase transition that is induced thermally or mechanically. Near-equiatomic nickel-titanium (NiTi) alloys, and more generally NiTi-based SMAs, are the most frequently selected in engineering applications. Moreover, good resistance to corrosion and fatigue makes these alloys excellent candidates to biomedical applications [4, 5]. For polycrystalline specimens,
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