Abstract
Local strain measurements are considered as an effective method for structural health monitoring of high-temperature components, which require accurate, reliable and durable sensors. To develop strain sensors that can be used in higher temperature environments, an improved metal-packaged strain sensor based on a regenerated fiber Bragg grating (RFBG) fabricated in hydrogen (H2)-loaded boron–germanium (B–Ge) co-doped photosensitive fiber is developed using the process of combining magnetron sputtering and electroplating, addressing the limitation of mechanical strength degradation of silica optical fibers after annealing at a high temperature for regeneration. The regeneration characteristics of the RFBGs and the strain characteristics of the sensor are evaluated. Numerical simulation of the sensor is conducted using a three-dimensional finite element model. Anomalous decay behavior of two regeneration regimes is observed for the FBGs written in H2-loaded B–Ge co-doped fiber. The strain sensor exhibits good linearity, stability and repeatability when exposed to constant high temperatures of up to 540 °C. A satisfactory agreement is obtained between the experimental and numerical results in strain sensitivity. The results demonstrate that the improved metal-packaged strain sensors based on RFBGs in H2-loaded B–Ge co-doped fiber provide great potential for high-temperature applications by addressing the issues of mechanical integrity and packaging.
Highlights
As a result of the global energy deficit and environmental deterioration, most plants tend to be larger scale in operations at higher operating parameters in order to improve energy conversion efficiency and productivity with reduced environmental impact
Annealing at a high temperature is necessary for the fabrication of the regenerated fiber Bragg grating (RFBG), it usually leads to mechanical strength degradation of the silica optical fibers
In metal-packaged this paper, thestrain results of the development characterization a laboratorial prototype of sensor based on the use of and an RFBG
Summary
As a result of the global energy deficit and environmental deterioration, most plants tend to be larger scale in operations at higher operating parameters in order to improve energy conversion efficiency and productivity with reduced environmental impact. One- or two-layer metallic films are typically deposited on the bare RFBGs as an adhesive and/or conductive layer by low temperature processes such as electroless plating [16,18], physical vapor deposition (e.g., magnetron sputtering [17,19] and evaporation deposition [20]), and laser-assisted maskless micro-deposition [21] This occurs in order to achieve reliable bonding between glass and metal, in addition to allowing to electroplate nickel coating on the metallic films as a protective layer. The metal-packaged strain sensors based on the use of the RFBGs fabricated in standard telecommunication silica fibers (Corning Inc., SMF-28, Corning, NY, USA) can only be used up to 400 ◦ C [17], as the mechanical strength of the standard SMF-28 silica optical fibers in which the RFBGs require the regeneration temperature of around 900 ◦ C was observed to considerably degrade after annealing at 900 ◦ C [26]. Numerical simulation of the sensor is carried out based on the basic principle of strain measurements using FBGs and three-dimensional (3-D) finite element (FE) modeling to analyze the mechanical response of the metal-packaged strain sensor
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