Optics-Based Strain Sensing System

An optics-based strain sensing system is being developed for quazi-distributed strain sensing in locations and environments that are not accessible to conventional strain sensors. The system comprises an Optical Interrogator that has been designed and constructed by Southern Photonics [1], and optical fibre coupled Bragg grating strain sensors. It has been tested using commercial fibre Bragg gratings [2] that were attached to 2 samples of 316 grade stainless steel and cycled in strain and temperature using an Instron mechanical testing machine and temperature controlled cabinet. The results have been compared to the performance of conventional electrical resistance strain gauges. Pairs of fibre Bragg gratings were simultaneously interrogated at 1540 and 1550 nm centre wavelengths to demonstrate the ability of the system to use multiple sensors for quazi-distributed sensing and temperature compensation. The Optical Interrogator resolution is approximately 4 microstrains, accounting for longer term temperature drift, and it is capable of resolving dynamic strains at rates of up to 90 Hz.

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High‐speed quasi‐distributed strain sensing based on time division multiplexing of fibre Bragg gratings

Electronics Letters ◽

10.1049/el.2015.4398 ◽

2016 ◽

Vol 52 (8) ◽

pp. 643-645 ◽

Cited By ~ 2

Author(s):

L. Ma ◽

C. Ma ◽

Y. Wang ◽

D.Y. Wang ◽

A. Wang

Keyword(s):

High Speed ◽

Bragg Gratings ◽

Strain Sensing ◽

Time Division Multiplexing ◽

Fibre Bragg Gratings ◽

Time Division ◽

Distributed Strain

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Enlargement of measurement range of simplified BOCDA fiber-optic distributed strain sensing system using a temporal gating scheme

10.1117/12.623707 ◽

2005 ◽

Cited By ~ 11

Author(s):

Kazuo Hotate ◽

Hiroshi Arai

Keyword(s):

Fiber Optic ◽

Measurement Range ◽

Strain Sensing ◽

Sensing System ◽

Distributed Strain ◽

Gating Scheme

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Evaluation of Strain Transition Properties between Cast-In Fibre Bragg Gratings and Cast Aluminium during Uniaxial Straining

Sensors ◽

10.3390/s20216276 ◽

2020 ◽

Vol 20 (21) ◽

pp. 6276

Author(s):

Florian Heilmeier ◽

Robert Koos ◽

Michael Singer ◽

Constantin Bauer ◽

Peter Hornberger ◽

...

Keyword(s):

Bragg Gratings ◽

Tensile Specimen ◽

Strain Sensors ◽

Fe Model ◽

Plastic Strains ◽

Closing The Gap ◽

Optical Strain ◽

Structural Parts ◽

Fibre Bragg Gratings

Current testing methods are capable of measuring strain near the surface on structural parts, for example by using strain gauges. However, stress peaks often occur within the material and can only be approximated. An alternative strain measurement incorporates fibre-optical strain sensors (Fiber Bragg Gratings, FBG) which are able to determine strains within the material. The principle has already been verified by using embedded FBGs in tensile specimens. The transition area between fibre and aluminium, however, is not yet properly investigated. Therefore, strains in tensile specimens containing FBGs were measured by neutron diffraction in gauge volumes of two different sizes around the Bragg grating. As a result, it is possible to identify and decouple elastic and plastic strains affecting the FBGs and to transfer the findings into a fully descriptive FE-model of the strain transition area.We thus accomplished closing the gap between the external load and internal straining obtained from cast-in FBG and generating valuable information about the mechanisms within the strain transition area.It was found that the porosity within the casting has a significant impact on the stiffness of the tensile specimen, the generation of excess microscopic tensions and thus the formation of permanent plastic strains, which are well recognized by the FBG. The knowledge that FBG as internal strain sensors function just as well as common external strain sensors will now allow for the application of FBG in actual structural parts and measurements under real load conditions. In the future, applications for long-term monitoring of cast parts will also be enabled and are currently under development.

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