Embedded Fiber Bragg Grating Strain Gauge for Mechanical Stability
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Solution Overview
Problem
Fiber-optic sensors are mechanically sensitive due to their thin cross-section, making handling difficult and prone to damage, and can slip when glued or laminated into components, leading to inaccurate force measurements.
Innovation Solution
A strain gauge with a carrier material and a fiber-optic sensor featuring a fiber Bragg grating, where the optical waveguide is embedded within the carrier material to enhance mechanical stability and accuracy, using a polymer carrier with reinforcement elements to adapt the modulus of elasticity and simplify handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the optical waveguide is made with a thin cross-section to reduce size, then the sensor becomes more compact, but the mechanical sensitivity increases making handling difficult and prone to damage
Solution Approach 1:
The optical waveguide is embedded within a carrier material that provides mechanical protection and stability. The carrier material acts as a protective outer layer that shields the fragile optical waveguide from damage during handling and installation, while allowing the waveguide to maintain its thin cross-section for compactness.
Solution Approach 2:
The strain gauge combines the optical waveguide with a carrier material to create a composite structure. This composite provides both the optical sensing functionality of the waveguide and the mechanical stability of the carrier material, resolving the contradiction between compactness and mechanical robustness.
2Ease of manufacture
If the optical waveguide is glued or laminated into a plastic component, then the sensor can be integrated into the component, but the waveguide can easily slip leading to inaccurate force measurements
Solution Approach 1:
The carrier material is embedded into the plastic component, and the optical waveguide is subsequently embedded into the carrier material. This nested embedding approach ensures that the waveguide is securely positioned within the component through a two-stage process, preventing slippage and ensuring accurate force measurements while maintaining ease of integration.
3Adaptability or versatility
If fiber connectors are used to connect optical waveguides, then multiple sensors can be connected to form a network, but the coupling becomes error-prone and integration into components is prevented
Solution Approach 1:
Multiple optical waveguides are bundled together within a single carrier material to form an integrated strain gauge assembly. This merging approach eliminates the need for separate fiber connectors at component interfaces, reducing coupling errors and simplifying integration while maintaining the capability to form sensor networks through the bundled structure.
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
The strain gauge can be attached to mechanical components more accurately and reliably, with improved mechanical stability and simplified handling, enabling precise measurement of forces, including acceleration, across various measuring ranges.
Implementation Method 1
The fiber Bragg grating is set up to reflect a predeterminable part of the incoming light and to transmit another part. The wavelength of the reflected or transmitted component depends on the grating constant of the fiber Bragg grating
Implementation Method 2
The refractive index of the core is selected to be slightly smaller than the refractive index of the cladding, so that light coupled into the core is guided within the core by total reflection at the interface between core and cladding
Implementation Method 3
The optical waveguide contains a core and a cladding that surrounds the core approximately concentrically. The refractive index of the core is selected to be slightly smaller than the refractive index of the cladding, so that light coupled into the core is guided within the core by total reflection
Implementation Method 4
The wavelength of the reflected or transmitted component depends on the grating constant of the fiber Bragg grating, which in turn is defined during the production of the fiber Bragg grating and then varies due to temperature changes or mechanical stress
Data Source
Figure 1~2
Figure 3~5
AI summary
The strain gauge (1) has a carrier material (10) and a fiber optical sensor (2), where optical fibers (21,22,23) are provided with a fiber-Bragg-grating (3). The carrier material is made from a polymer. The carrier material has a first layer and a second layer, and the fiber optical sensor is arranged between the first layer and the second layer.