Sub-75 µm Optical Fiber Bundles for Robust Crack Detection
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Solution Overview
Problem
Existing crack detection systems for loaded engineering structures, such as wind turbine rotor blades, face challenges in effectively detecting cracks due to fragility and limited robustness of optical fibers used, which can lead to false readings and inadequate early warning of crack propagation.
Innovation Solution
The use of optical fibers with diameters below 75 µm, bundled together to form robust fiber bundles, which are integrated into the structure to provide redundancy and visual detection capabilities, along with light modulation and time-gated detection methods to accurately determine crack severity and location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical fibres with diameter around 120 µm are used in fibre Bragg grating systems, then crack detection capability is provided, but the fibres are extremely fragile and lack robustness
Solution Approach 1:
The optical fibre is segmented into multiple smaller fibres within a bundle, where each individual fibre has reduced diameter and fragility, but the collective bundle maintains robustness while preserving crack detection capability through redundancy
Solution Approach 2:
The patent combines multiple optical fibres into a composite bundle structure, integrating materials with different properties to achieve both robustness (through collective strength) and measurement precision (through individual fibre sensitivity)
2Measurement precision
If optical fibres are attached directly to the surface of the structure, then crack detection is enabled, but the fibres interfere with the structure's aerodynamics and integrity
Solution Approach 1:
The optical fibre bundle is embedded within the structural material rather than being attached to the surface, transitioning from a surface-level attachment to an integrated internal configuration that eliminates aerodynamic interference while maintaining crack detection through strain transfer from the surrounding matrix
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the robustness and reliability of crack detection, allowing for early and accurate identification of cracks, even in rapidly developing situations, and enables visual detection of cracks under night conditions, while minimizing interference with the structure's aerodynamics and integrity.
Implementation Method 1
one or more optical fibres which can transmit the light emitted by a light source to a detector
Implementation Method 2
They are used for detecting transmitted or reflected light, respectively. In case of a crack the amount of transmitted, or reflected, light is altered
Data Source
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AI summary
A crack detection system for detecting cracks in a loaded engineering structure (1) is provided. The crack detection system comprises a light source (17), optical fibres (6) that are led through the structure (1), and a means (19) for coupling the light of the light source (17) into the optical fibres (6). The optical fibres (6) have diameters below 75 µm.