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Optical Fiber Sensors for Aircraft Structural Health Monitoring.

García I, Zubia J, Durana G, Aldabaldetreku G, Illarramendi MA, Villatoro J - Sensors (Basel) (2015)

Bottom Line: Optical fiber sensors applied to the monitoring of aircraft structures provide some advantages over traditional sensors.Several practical applications for structures and engines we have been working on are reported in this article.With regard to engine condition evaluation, we present some results obtained with a reflected intensity-modulated optical fiber sensor for tip clearance and tip timing measurements in a turbine assembled in a wind tunnel.

View Article: PubMed Central - PubMed

Affiliation: Department of Communications Engineering, E.T.S.I. of Bilbao, University of the Basque Country UPV/EHU, Alda. Urquijo s/n Bilbao 48013, Spain. iker.garciae@ehu.eus.

ABSTRACT
Aircraft structures require periodic and scheduled inspection and maintenance operations due to their special operating conditions and the principles of design employed to develop them. Therefore, structural health monitoring has a great potential to reduce the costs related to these operations. Optical fiber sensors applied to the monitoring of aircraft structures provide some advantages over traditional sensors. Several practical applications for structures and engines we have been working on are reported in this article. Fiber Bragg gratings have been analyzed in detail, because they have proved to constitute the most promising technology in this field, and two different alternatives for strain measurements are also described. With regard to engine condition evaluation, we present some results obtained with a reflected intensity-modulated optical fiber sensor for tip clearance and tip timing measurements in a turbine assembled in a wind tunnel.

No MeSH data available.


Related in: MedlinePlus

Spectra of two FBGs bonded on the specimen before (black line) and after (blue line) aging for one month in a climate chamber.
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sensors-15-15494-f004: Spectra of two FBGs bonded on the specimen before (black line) and after (blue line) aging for one month in a climate chamber.

Mentions: The results of the tests on the specimens previously aged for one and two months are very similar and, unexpectedly, they show that the readings of the FBGs are about 50% higher than those obtained before the aging. Since the maximum working temperature of the FBG was never exceeded, this discrepancy in the readings must be caused by the effect of humidity. Its influence can make the refractive index vary, shifting the Bragg wavelength and yielding much higher strain values than expected, so in order to avoid this problem, it is necessary to properly insulate the FBG from humidity. The results for two FBGs of the specimen aged for one month for 200 kN traction stress tests are displayed in Figure 4. The traction stress was applied in steps of 20 kN. In most cases, FBGs are employed in SHM applications to detect strain or temperature variations in a quasi-static way. However, if FBGs are used to detect impacts in aircraft structures, vibrations at higher frequencies must be analyzed [48]. We developed a proof-of-concept system for impact detection in composites using FBGs [49]. The objective was to obtain the arrival times of the surface mechanical waves produced by an impact in different points of the structure. Using these times, the impact location could be determined by triangulation. Two arrays of five FBGs were instrumented on a piece of Carbon Fiber Reinforced Polymer (CFRP). In order to detect the mechanical waves due to the impacts in as many directions as possible, nine of the FBGs were placed following the arrangement given in [50]. The remaining FBG was insulated from the vibrations and employed to compensate the effect of the temperature. The final layout can be observed in Figure 5. The test procedure included five different impact points; each impact was repeated three times with increasing energies from 0.245 J to 29.4 J.


Optical Fiber Sensors for Aircraft Structural Health Monitoring.

García I, Zubia J, Durana G, Aldabaldetreku G, Illarramendi MA, Villatoro J - Sensors (Basel) (2015)

Spectra of two FBGs bonded on the specimen before (black line) and after (blue line) aging for one month in a climate chamber.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541841&req=5

sensors-15-15494-f004: Spectra of two FBGs bonded on the specimen before (black line) and after (blue line) aging for one month in a climate chamber.
Mentions: The results of the tests on the specimens previously aged for one and two months are very similar and, unexpectedly, they show that the readings of the FBGs are about 50% higher than those obtained before the aging. Since the maximum working temperature of the FBG was never exceeded, this discrepancy in the readings must be caused by the effect of humidity. Its influence can make the refractive index vary, shifting the Bragg wavelength and yielding much higher strain values than expected, so in order to avoid this problem, it is necessary to properly insulate the FBG from humidity. The results for two FBGs of the specimen aged for one month for 200 kN traction stress tests are displayed in Figure 4. The traction stress was applied in steps of 20 kN. In most cases, FBGs are employed in SHM applications to detect strain or temperature variations in a quasi-static way. However, if FBGs are used to detect impacts in aircraft structures, vibrations at higher frequencies must be analyzed [48]. We developed a proof-of-concept system for impact detection in composites using FBGs [49]. The objective was to obtain the arrival times of the surface mechanical waves produced by an impact in different points of the structure. Using these times, the impact location could be determined by triangulation. Two arrays of five FBGs were instrumented on a piece of Carbon Fiber Reinforced Polymer (CFRP). In order to detect the mechanical waves due to the impacts in as many directions as possible, nine of the FBGs were placed following the arrangement given in [50]. The remaining FBG was insulated from the vibrations and employed to compensate the effect of the temperature. The final layout can be observed in Figure 5. The test procedure included five different impact points; each impact was repeated three times with increasing energies from 0.245 J to 29.4 J.

Bottom Line: Optical fiber sensors applied to the monitoring of aircraft structures provide some advantages over traditional sensors.Several practical applications for structures and engines we have been working on are reported in this article.With regard to engine condition evaluation, we present some results obtained with a reflected intensity-modulated optical fiber sensor for tip clearance and tip timing measurements in a turbine assembled in a wind tunnel.

View Article: PubMed Central - PubMed

Affiliation: Department of Communications Engineering, E.T.S.I. of Bilbao, University of the Basque Country UPV/EHU, Alda. Urquijo s/n Bilbao 48013, Spain. iker.garciae@ehu.eus.

ABSTRACT
Aircraft structures require periodic and scheduled inspection and maintenance operations due to their special operating conditions and the principles of design employed to develop them. Therefore, structural health monitoring has a great potential to reduce the costs related to these operations. Optical fiber sensors applied to the monitoring of aircraft structures provide some advantages over traditional sensors. Several practical applications for structures and engines we have been working on are reported in this article. Fiber Bragg gratings have been analyzed in detail, because they have proved to constitute the most promising technology in this field, and two different alternatives for strain measurements are also described. With regard to engine condition evaluation, we present some results obtained with a reflected intensity-modulated optical fiber sensor for tip clearance and tip timing measurements in a turbine assembled in a wind tunnel.

No MeSH data available.


Related in: MedlinePlus