Optical Sensing Systems For Structural Health Monitoring

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FBG Rail Monitoring Applications

FBG sensors are well suited for rail monitoring applications because they are rugged, self referencing (do not drift or need to be recalibrated), and they do not transmit electricity, so there is no risk of signal or voltage leakage. FBGs also do not require a Wheatstone Bridge circuit to measure the change in strain; each individual sensor measures its own values, which can provide more information than conventional technologies. The following case studies illustrate some of their uses.

Stress Monitoring

FBG sensors can be attached to the rail to monitor for stress caused by ground subsidence, thermal change and train loads. FBGs sensors can be attached to the rail axially or in a rosette arrangement and through changes in strain, it can measure changes in stress, using the rail's known modulus of elasticity. Temperature sensors are also typically applied with the strain sensors to compensate for the thermal effect on both the optical fibre and the thermal expansion of the rail. This allows distinction between mechanical stress, thermal stress and total stress. Many conventional technologies do not offer this feature. MOS conducted a pilot study of axial FBG sensors alongside electrical strain gauges setup in a Full Wheatstone Bridge circuit in a tee-rosette arrangement, and these distinctions were evident. For more information on this pilot study please contact us.

Rolling Stock Detection

FBG sensors can also be used to capture the strain signatures from vehicle axles, and have successfully been used to monitor rolling stock weight, turning the rail into a weigh bridge.
For more information please contact us.
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