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Series on BIOMECHANICS   ISSN 1313-2458
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The influence of hydrogen diffusion in the structure of NiTi wires on their behavior during the cyclic loading
R. Sarrajorcid, T. Hassine, F. Gamaounorcid
Abstract: Objectives: This article aimed to investigate the influence of hydrogen diffusion in the structure during cyclic loading on the superelastic behavior of NiTi alloys. Materials and Methods: To predict these effects, a commercial Ni-Ti archwire from Forestdent company has been charged by hydrogen in 0.9% NaCl solution with a current density of 10 A/m2 during 6h. Results: Residual strain, dissipated energy, critical start stress and end stress of the martensite transformation evolves during cyclic loading-unloading. This evolution becomes more significant with hydrogen charging rather that without it. Moreover, an embrittlement has been detected for the archwire charged during 6h which absorbed the bigger amount of hydrogen. Discussion: Nickel-titanium arc wires have been used in orthodontic clinics which show an embrittlement of wires after few months of use in oral cavity of the patient. In fact, the embrittlement can be owing to the expansion in the subsurface of the parent phase of an internal stress during hydrogen charging, which acts as a barrier for the growth of the martensite bands. The hydrogen is due to the presence of fluoride in the toothpaste. Conclusions: The present study suggests that the amount of hydrogen absorbed by the structure leads to SMA embrittlement.

Series on Biomechanics, Vol.38, No.1 (2024), 57-62

Keywords: cyclic loading; hydrogen; martensite variants; Shape memory alloys; superelastic
References: (click to open/close)
DOI: 10.7546/SB.06.01.2024
Date published: 2024-04-23
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