Photograph showing the complete setup of the in situ bending rotation fatigue test rig. (1) BRF base plate, (2) wire specimen, (3) working electrode, (4) inductive sensor, (5) tachometer/counter, (6) flexible motor shaft, (7) reference electrode, (8) electrochemical cell, and (9) DC motor.
Details of the electrochemical cell. (a) Front plate with rubber seal (1), cell base plate (2), provision for reference electrode (3), U shaped cavities for inserts (4), electrolyte outlet (5). (b) Cell base plate with inserts (6) for different bending radii, mounted insert (R = 60 mm) (7), electrolyte reservoir (8), wire sample (working electrode) (9).
Comparison of the linear polarization behavior of an as-received and a pre-fatigued NiTi wire. The pre-fatigued wire was subjected to 5120 BRF cycles.
(a) Comparison of the in situ open circuit potential transient behavior for NiTi wires under static bending conditions and subjected to cyclic rotational loading. (b) OCP as a function of log (t) for a wire under BRF loading.
In situ polarization behavior of a NiTi wire subjected to bending rotation fatigue. Structural failure occurred after 2944 cycles.
SEM micrographs of a NiTi wire after in situ linear polarization experiments showing damage due to localized corrosion. (a) Wire surface showing pits indicated by arrows. (b) Fracture surface featuring large pits on the outer edges leading to corrosion assisted fatigue failure.
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