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The influence of carbon content on cyclic fatigue of NiTi SMA wires
Author(s) -
Matheus T. C. U.,
Menezes W. M. M.,
Rigo O. D.,
Kabayama L. K.,
Viana C. S. C.,
Otubo J.
Publication year - 2011
Publication title -
international endodontic journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.988
H-Index - 119
eISSN - 1365-2591
pISSN - 0143-2885
DOI - 10.1111/j.1365-2591.2011.01864.x
Subject(s) - materials science , nickel titanium , carbon fibers , high carbon , metallurgy , composite material , scanning electron microscope , content (measure theory) , shape memory alloy , alloy , mathematical analysis , mathematics , composite number
Matheus TCU, Menezes WMM, Rigo OD, Kabayama LK, Viana CSC, Otubo J. The influence of carbon content on cyclic fatigue of NiTi SMA wires. International Endodontic Journal , 44 , 567–573, 2011. Abstract Aim To evaluate two NiTi wires with different carbon and oxygen contents in terms of mechanical resistance to rotary bending fatigue (RBF) under varied parameters of strain amplitude and rotational speed. Methodology The wires produced from two vacuum induction melting (VIM) processed NiTi ingots were tested, Ti‐49.81at%Ni and Ti‐50.33at%Ni, named VIM 1 and VIM 2. A brief analysis related to wire fabrication is also presented, as well as chemical and microstructural analysis by energy dispersive spectroscopy (EDS) and optical microscope, respectively. A computer controlled RBF machine was specially constructed for the tests. Three radii of curvature were used: 50.0, 62.5 and 75.0 mm, respectively, R 1 , R 2 and R 3 , resulting in three strain amplitudes ε a : 1.00%, 0.80% and 0.67%. The selected rotational speeds were 250 and 455 rpm. Results The VIM 1 wire had a high carbon content of 0.188 wt% and a low oxygen content of 0.036 wt%. The oxygen and carbon contents of wire VIM 2 did not exceed their maximum, of 0.070 and 0.050 wt%, according to ASTM standard (ASTM F‐2063‐00 2001). The wire with lower carbon content performed better when compared to the one with higher carbon content, withstanding 29 441 and 12 895 cycles, respectively, to fracture. Conclusions The surface quality of the wire was associated with resistance to cyclic fatigue. Surface defects acted as stress concentrators points. Overall, the number of cycles to failure was higher for VIM 2 wires with lower carbon content.