Proof-testing and probabilistic lifetime estimation of glass fibers for sensor applications

Abstract

The mechanical reliability of sensing glass fiber is one of the important problems in the practical use of fiber-optic sensors. To ensure long-term reliability on a mass-production level, a method of proof-testing is applied to a sensing glass fiber that will be subjected to mechanical deformation in its service situation. We propose to employ a higher strain level (screening level) in the proof-testing with a fiber-recoating technique that can suppress excessive damage during the testing. We consider a standard lifetime of 15 years of automotive applications and ensure a practical level of failure probability by a model calculation by using the strength data of a prototype fiber with the method of fracture-mechanics theory.

<title>Fiber Bragg grating accelerometer for buildings and civil infrastructures</title>

“…The fatigue constant n and a characteristic parameter m describing a distribution of the crack size are determined from tests and are given as 23.9 and 4, respectively, for a single-mode glass fiber 6) . The number of failures per kilometer N p is experimentally determined.…”

Strain and temperature sensitivity of a single-mode polymer optical fiber

“…However, fused-silica fibers have an upper strain limit of approximately 3-5% and in general are reliable only to ϳ1% strain after selection of fibers by proof testing. 2 In highly loaded engineering structures such as highway bridges, buildings, and aircraft wings, transverse loading can result in large bending strains, which can induce locally high strains, so monitoring structural strain is becoming increasingly important. With the advent of new engineering materials, such as composites, the acceptable range of applied strain can exceed the breaking strain of fused-silica fiber, precluding the use of standard fiber-based strain gauges.…”

Experimental and numerical study of a shunt structure for large dynamic strain measurement

“…In addition to metallic foil and fibre optical strain gauge, novel strain-sensitive material [9] and image processing based methods are developed for large strain measurement. Strain-sensitive material like polymer optical fibre has the potential to measure large strain, surpassing the intrinsic maximum strain level (approximately 4%) of silicon fibre optical FBG sensors limited by the failure strain of silica [10]. Piezoelectric strain sensor has excellent sensitivity and performance for highly dynamic strain, but the zero-drift issue makes it for unsuitable for static strain measurement [11].…”