scholarly journals Comparison of DOFS Attachment Methods for Time-Dependent Strain Sensing

Sensors ◽  
2021 ◽  
Vol 21 (20) ◽  
pp. 6879
Author(s):  
Shaoquan Wang ◽  
Erik Sæter ◽  
Kaspar Lasn
Keyword(s):  
Optical Fibers ◽  
Time Dependent ◽  
Tensile Creep ◽  
Great Promise ◽  
Strain Sensing ◽  
Monitoring Methods ◽  
Engineering Structures ◽  
Dependent Strain ◽  
Residual Strains ◽  
Distributed Optical Fiber

Structural health monitoring (SHM) is a challenge for many industries. Over the last decade, novel strain monitoring methods using optical fibers have been implemented for SHM in aerospace, energy storage, marine, and civil engineering structures. However, the practical attachment of optical fibers (OFs) to the component is still problematic. While monitoring, the amount of substrate strain lost by the OF attachment is often unclear, and difficult to predict under long-term loads. This investigation clarifies how different attachment methods perform under time-dependent loading. Optical fibers are attached on metal, thermoset composite, and thermoplastic substrates for distributed strain sensing. Strains along distributed optical fiber sensors (DOFS) are measured by optical backscatter reflectometry (OBR) and compared to contact extensometer strains under tensile creep loading. The quality of the bondline and its influence on the strain transfer is analyzed. Residual strains and strain fluctuations along the sensor fiber are correlated to the fiber attachment method. Results show that a machine-controlled attachment process (such as in situ 3-D printing) holds great promise for the future as it achieves a highly uniform bondline and provides accurate strain measurements.

The Study of On-Line Fiber Optic Monitoring for Pressure Component

2013 ◽  
Vol 330 ◽  
pp. 460-464
Author(s):  
Biao Xiao ◽  
Jun Si ◽  
Xiao Ming Luo ◽  
H.T. Wang ◽  
F.Z. Xuan
Keyword(s):  
Optical Fiber ◽  
Detection System ◽  
Fiber Grating ◽  
Piping System ◽  
Monitoring Methods ◽  
Engineering Structures ◽  
Advantages And Disadvantages ◽  
On Line ◽  
Implementation Method ◽  
Distributed Optical Fiber

The application of the distributed optical-fiber detection system and optical fiber grating detection system in the laboratory piping system leakage platform, was analyzed in this paper. Based on the on-line monitoring tests, the potential advantages and disadvantages of optical-fiber method using for engineering structures were summarized. The implementation method on the optical-fiber monitoring methods for pressure vessel and industrial piping system in service was proposed in the end.

CHARACTERIZING ANOMALIES IN DISTRIBUTED STRAIN MEASUREMENTS OF CAST-IN-SITU BORED PILES

2016 ◽  
Vol 78 (8-5) ◽  
Author(s):  
Hisham Mohamad ◽  
Bun Pin Tee ◽  
Koh An Ang ◽  
Mun Fai Chong
Keyword(s):  
Load Transfer ◽  
Load Test ◽  
Strain Sensing ◽  
Strain Profile ◽  
A New Technique ◽  
Optical Time ◽  
Distributed Optical Fiber ◽  
Non Destructive ◽  
Distributed Strain

This paper describes the method of identifying typical defects of bored cast-in-situ piles when instrumenting using Distributed Optical Fiber Strain Sensing (DOFSS). The DOFSS technology is based on Brillouin Optical Time Domain Analyses (BOTDA), which has the advantage of recording continuous strain profile as opposed to the conventional discrete based sensors such as Vibrating Wire strain gauges. In pile instrumentation particularly, obtaining distributed strain profile is important when analysing the load-transfer and shaft friction of a pile, as well as detecting any anomalies in the strain regime. Features such as defective pile shaft necking, discontinuity of concrete, intrusion of foreign matter and improper toe formation due to contamination of concrete at base with soil particles, among others, may cause the pile to fail. In this study, a new technique of detecting such defects is proposed using DOFSS technology which can potentially supplement the existing non-destructive test (NDT) methods. Discussion on the performance of instrumented piles by means of maintained load test are also presented

Process Monitoring of Fiber-Reinforced Polymer Composites

MRS Bulletin ◽  
2002 ◽  
Vol 27 (5) ◽  
pp. 370-380 ◽  
Author(s):  
B. Degamber ◽  
G. F. Fernando
Keyword(s):  
Optical Fibers ◽  
Process Monitoring ◽  
Fiber Reinforced Polymer ◽  
Specific Reference ◽  
Monitoring Methods ◽  
Mid Infrared ◽  
Reinforced Polymer ◽  
Fiber Reinforced Polymer Composites ◽  
Uv Visible ◽  
Areas Of Interest

AbstractThis article presents a review of optical-fiber-based process-monitoring techniques that can be used to track the chemical reactions that take place during the processing of materials, with specific reference to thermosetting resins. The techniques covered include quantitative process-monitoring methods based on near and mid-infrared, Raman, UV–visible, evanescent wave, and fluorescence spectroscopy. The basis for refractive-index-based process monitoring using optical fibers is also presented. The techniques described here can be readily applied to other classes of materials and other areas of interest such as aging and degradation. Recent advances in noncontact process monitoring are also presented.

Measurement of Residual Strains As a Parameter of Matrix Cracking in CFRP Laminates

2020 ◽  
Author(s):  
M. J. Mohammad Fikry ◽  
Shinji Ogihara ◽  
Vladimir Vinogradov
Keyword(s):  
Viscoelastic Behavior ◽  
Matrix Cracking ◽  
Time Dependent ◽  
Strain Gauges ◽  
Recovery Test ◽  
Cfrp Laminates ◽  
Matrix Cracks ◽  
Theoretical Predictions ◽  
Residual Strains ◽  
Good Agreement

Abstract Matrix cracking in CFRP laminates results in degradation of mechanical properties of the material and appearance of residual strains. In this study, the residual strains investigated are experimentally and analytically for CFRP [0/756]s laminates. The strain gauges were used in this study to measure the strains. Due to very small residual strains at the unloading condition, the residual strains were also measured at different stress levels for laminates with different crack densities and are compared with theoretical predictions. Time-dependent viscoelastic behavior of the material is also considered to accurately measure the residual strains due to the occurrence of matrix cracks. This was done by using the strain recovery test when the loads were stopped for 1–1.5 hours during unloading and the strain changes during these times were recorded. The experimental results of the residual strains are in reasonably good agreement with the theoretical predictions. The fiber non-linearity properties of the laminates may cause some experimental data to shift above the analytical line.

scholarly journals Truly Distributed Optical Fiber Sensors for Structural Health Monitoring: From the Telecommunication Optical Fiber Drawling Tower to Water Leakage Detection in Dikes and Concrete Structure Strain Monitoring

2010 ◽  
Vol 2010 ◽  
pp. 1-13 ◽  
Author(s):  
Jean-Marie Henault ◽  
Gautier Moreau ◽  
Sylvain Blairon ◽  
Jean Salin ◽  
Jean-Robert Courivaud ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Optical Fibers ◽  
Brillouin Scattering ◽  
Optical Fiber Sensors ◽  
Leakage Detection ◽  
Strain Sensing ◽  
Water Leakage ◽  
Fiber Sensors ◽  
Practical Applications ◽  
Water Leakage Detection

Although optical fiber sensors have been developed for 30 years, there is a gap between lab experiments and field applications. This article focuses on specific methods developed to evaluate the whole sensing chain, with an emphasis on (i) commercially-available optoelectronic instruments and (ii) sensing cable. A number of additional considerations for a successful pairing of these two must be taken into account for successful field applications. These considerations are further developed within this article and illustrated with practical applications of water leakage detection in dikes and concrete structures monitoring, making use of distributed temperature and strain sensing based on Rayleigh, Raman, and Brillouin scattering in optical fibers. They include an adequate choice of working wavelengths, dedicated localization processes, choices of connector type, and further include a useful selection of traditional reference sensors to be installed nearby the optical fiber sensors, as well as temperature compensation in case of strain sensing.

scholarly journals Comparative Experimental Study of a High-Temperature Raman-Based Distributed Optical Fiber Sensor with Different Special Fibers

Sensors ◽  
2019 ◽  
Vol 19 (3) ◽  
pp. 574 ◽  
Author(s):  
Ismail Laarossi ◽  
María Quintela-Incera ◽  
José López-Higuera
Keyword(s):  
Experimental Study ◽  
High Temperature ◽  
Optical Fiber ◽  
Optical Fibers ◽  
Optical Fiber Sensor ◽  
Time Domain Reflectometry ◽  
Fiber Sensor ◽  
Mechanical Resistance ◽  
Distributed Optical Fiber Sensor ◽  
Distributed Optical Fiber

An experimental study of a high temperature distributed optical fiber sensor based on Raman Optical-Time-Domain-Reflectometry (ROTDR) (up to 450 °C) and optical fibers with different coatings (polyimide/carbon, copper, aluminum and gold) is presented. Analysis of the distributed temperature sensor (DTS) measurements determined the most appropriate optical fiber to be used in high temperature industrial environment over long periods of time. To demonstrate the feasibility of this DTS for an industrial application, an optical cable was designed with the appropriate optical fiber and it was hermetically sealed to provide the required mechanical resistance and isolate the fiber from environmental degradations. This cable was used to measure temperature up to 360 °C of an industrial furnace during 7 days.

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