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An Improved Metal-Packaged Strain Sensor Based on A Regenerated Fiber Bragg Grating in Hydrogen-Loaded Boron – Germanium Co-Doped Photosensitive Fiber for High-Temperature Applications

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Weibull plot of the tensile strengths of the bare silica optical fibers annealed at 500 °C and 900 °C respectively and tested at room temperature (26 °C), compared with those of the bare fibers without annealing tested at room temperature (26 °C), 300 °C and 540 °C, as well as the as-received fibers tested at room temperature (26 °C) [26]. RT: room temperature
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sensors-17-00431-f004: Weibull plot of the tensile strengths of the bare silica optical fibers annealed at 500 °C and 900 °C respectively and tested at room temperature (26 °C), compared with those of the bare fibers without annealing tested at room temperature (26 °C), 300 °C and 540 °C, as well as the as-received fibers tested at room temperature (26 °C) [26]. RT: room temperature

Mentions: Annealing at a high temperature is necessary for the fabrication of the RFBGs, although it usually leads to mechanical strength degradation of the silica optical fibers. It is thus essential to quantify the effects of annealing on the tensile strength of silica optical fibers. A summary of the results from the tensile tests of the silica optical fibers reported in our previous work [26] is shown in Figure 4. The fracture stress of all annealed fibers decreases precipitously after annealing at 500 °C and 900 °C. The mean tensile strengths determined by the fracture stresses collected from the tensile testing from 15 samples are shown in Figure 5. The results show that the annealing treatment leads to a significant reduction in the strength of the silica optical fibers after annealing at high temperatures. A particularly interesting result is that the strength of the annealed fibers is not only very much lower than that of the samples without annealing tested at room temperature, but it is also much lower than those of the samples tested at the temperatures of 300 °C and 540 °C, which is very similar to the behavior observed by others [24,27]. Figure 5 also shows that the higher temperature of annealing at 900 °C could lead to a larger reduction in strength of the fibers compared to those annealed at 500 °C. Silica fibers were found to become mechanically weaker after being annealed in air but the cause of such weakening was not well defined. Very recently, it was found that surface crystallization is probably responsible for the mechanical weakening observed in silica glass fiber surface after annealing at temperatures in excess of around 800 °C, while water diffusion-controlled virtual pitting of the glass surface is likely the source for the strength degradation at lower temperatures [27].


An Improved Metal-Packaged Strain Sensor Based on A Regenerated Fiber Bragg Grating in Hydrogen-Loaded Boron – Germanium Co-Doped Photosensitive Fiber for High-Temperature Applications
Weibull plot of the tensile strengths of the bare silica optical fibers annealed at 500 °C and 900 °C respectively and tested at room temperature (26 °C), compared with those of the bare fibers without annealing tested at room temperature (26 °C), 300 °C and 540 °C, as well as the as-received fibers tested at room temperature (26 °C) [26]. RT: room temperature
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5375717&req=5

sensors-17-00431-f004: Weibull plot of the tensile strengths of the bare silica optical fibers annealed at 500 °C and 900 °C respectively and tested at room temperature (26 °C), compared with those of the bare fibers without annealing tested at room temperature (26 °C), 300 °C and 540 °C, as well as the as-received fibers tested at room temperature (26 °C) [26]. RT: room temperature
Mentions: Annealing at a high temperature is necessary for the fabrication of the RFBGs, although it usually leads to mechanical strength degradation of the silica optical fibers. It is thus essential to quantify the effects of annealing on the tensile strength of silica optical fibers. A summary of the results from the tensile tests of the silica optical fibers reported in our previous work [26] is shown in Figure 4. The fracture stress of all annealed fibers decreases precipitously after annealing at 500 °C and 900 °C. The mean tensile strengths determined by the fracture stresses collected from the tensile testing from 15 samples are shown in Figure 5. The results show that the annealing treatment leads to a significant reduction in the strength of the silica optical fibers after annealing at high temperatures. A particularly interesting result is that the strength of the annealed fibers is not only very much lower than that of the samples without annealing tested at room temperature, but it is also much lower than those of the samples tested at the temperatures of 300 °C and 540 °C, which is very similar to the behavior observed by others [24,27]. Figure 5 also shows that the higher temperature of annealing at 900 °C could lead to a larger reduction in strength of the fibers compared to those annealed at 500 °C. Silica fibers were found to become mechanically weaker after being annealed in air but the cause of such weakening was not well defined. Very recently, it was found that surface crystallization is probably responsible for the mechanical weakening observed in silica glass fiber surface after annealing at temperatures in excess of around 800 °C, while water diffusion-controlled virtual pitting of the glass surface is likely the source for the strength degradation at lower temperatures [27].

View Article: PubMed Central - PubMed

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.

No MeSH data available.