<title>Cyclic fatigue behavior of silica fiber</title>

Abstract

The mechanical reliability of optical fiber is critically important for many engine sensor applications where the fiber is subjected to cyclic loading, high temperature, and oily, acidic environments. We have investigated the effect of buffer coatings on the cyclic fatigue behavior of fused silica fibers. Aluminum, polyimide, uvcurable epoxy acrylate, and Tefzel coated fibers were tested at room temperature and after exposure to heat and oil. Cyclic fatigue was measured using a test fixture that simulates the motion of a piston in an internal combustion engine. The results indicate that the selection of buffer coating is an important consideration in determining mechanical reliability of optical fibers in this application.

<title>Cyclic fatigue of high-strength optical fibers in bending</title>

“…Rogers 6 attached optical fibers to a crank to simulate a fiber sensor attached to the piston in an internal combustion engine. The fibers were flexed at 28.8 Hz under relatively low stress.…”

Enhanced transverse wavelength tuning of fiber Bragg gratings for sensing applications

“…The cyclic nature of the stresses for repeated tuning also brings in the need for fatigue life evaluation. Even though the reliability of FBGs subjected to axial loading has extensively been studied by various researchers [118][119][120][121][122][123][124][125], no work has been done addressing the reliability upon transverse loading. It is necessary to ensure that the required performance of the laterally loaded FBG sensors is achievable at stress levels and frequencies well below the critical limit for immature failure.…”

“…Number of loading cycles is yet another factor which could affect the time to failure besides the magnitude of the applied stress. However, it is already established by various studies [115][116][117][118][119][120][121][122][123][124] that silica fiber do not exhibit cyclic fatigue though failure still occurs by stress corrosion cracking. Therefore, for the purposes of making reliability estimates for optical fibers, the service stress can be modeled as a static stress.…”