Fiber Bragg Gratings Sensors for Aircraft Wing Shape Measurement: Recent Applications and Technical Analysis

In this paper, a new damage feature, spectral area, was extracted to effectively detect crack location by studying the deformation mechanism of fiber Bragg grating (FBG) reflection spectra. In order to verify the robustness and reliability of spectral area to detect crack location, the following work was carried out: Firstly, the strain information was extracted by extended finite element method (XFEM) with fatigue crack propagation. The transmission matrix method (TMM) was used to simulate FBG reflection spectra using numerical results. Secondly, the fatigue crack growth monitoring experiment based on FBG sensors was carried out, and the digital image correlation (DIC) method was used to measure the strain values at the placement of FBG sensors with crack propagation. The temperature characteristic test of FBG was carried out to investigate the influence of temperature variation on the spectral area. The results presented that the spectral area was insensitive to temperature variation and experimental noise, and was greatly sensitive to the complex non-uniform strain field cause by crack damage. Moreover, compared with the 5 mm FBG sensor, the 10 mm FBG sensor showed a larger critical detection range for crack damage. Therefore, the spectral area can be used as a reliable damage feature to detect the crack location quantitatively based on the simulated and experimental results.

Section: The Analysis Of Fbg Strain and Temperture Featurementioning

confidence: 99%

The Location Monitoring of Fatigue Crack Damage by Using the Spectral Area Extracted from FBG Spectra

Zhao

Zhang

et al. 2020

“…Fiber Bragg grating (FBG) sensors have been used for three decades now [ 1 ], in applications as varied as aircraft wing shape measurements [ 2 ], temperature monitoring in medical treatments [ 3 ], pressure and temperature sensing in oil wells [ 4 ], or strain sensing in biomechanics [ 5 ]. FBG sensors have traditionally been measured either with a combination of a broadband optical source and a spectrometer, or a wavelength-swept source and a photodiode [ 1 ].…”

Section: Introductionmentioning

confidence: 99%

Dual Wavelength Differential Detection of Fiber Bragg Grating Sensors with a Pulsed DFB Laser

Ouellette

2020

We show how dual wavelength differential detection can be used to measure fiber Bragg grating sensors using nanosecond pulses from a single DFB laser diode, by taking advantage of its dynamic chirp. This can be performed in two ways: by measuring the reflected power from two separate pulses driven by two different currents, or by taking two delayed digitized samples within a single pulse. A prototype instrument using fast digitizing and processing with an FPGA is used to characterize the chirp, from which the performance can be optimized for both measurement schemes.

“…Significant improvements have also been made to FBGs to improve strength and versatility [ 4 , 5 , 6 ] while also improving sensitivity [ 7 , 8 ]. Such measurements have been used in industry for many years, for example, in testing strain in airplanes [ 9 ] and bridges [ 10 ] or automotive traffic [ 11 ]. These relatively slow measurements are able to be made with off-the-shelf spectrometers and software packages to achieve readouts of up to a few kHz [ 12 ].…”

Section: Introductionmentioning

confidence: 99%

High Speed, Localized Multi-Point Strain Measurements on a Containment Vessel at 1.7 MHz Using Swept-Wavelength Laser-Interrogated Fiber Bragg Gratings

Gilbertson

Pickrell

Castano

et al. 2020

Dynamic elastic strain in ~1.8and 1.0 m diameter containment vessels containing a high explosive detonation was measured using an array of fiber Bragg gratings. The all-optical method, called real-time localized strain measurement, recorded the strain for 10 ms after detonation with additional measurements being sequentially made at a rate of 1.7 MHz. A swept wavelength laser source provided the repetition rate necessary for such high-speed measurements while also providing enough signal strength and bandwidth to simultaneously measure 8 or more unique points on the vessel’s surface.The data presented here arethen compared with additional diagnostics consisting of a fast spectral interferometer and an optical backscatter reflectometer to show a comparison between the local and global changes in the vessel strain, both dynamically and statically to further characterize the performance of the localized strain measurement.The results are also compared with electrical resistive strain gauges and finite element analysis simulations.