Use of fiber optic strain sensors to monitor fastener damage in structures
AssigneeSikorsky Aircraft Corporation
InventorsAvinash V. Sarlashkar, Theodore S. Meyer, Matthew P. Harrigan
Life of this patent
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Abstract
A fastener health monitoring system includes a structure including a first component and a second component, one or more fasteners securing the first component to the second component, and an optical fiber arranged adjacent to the one or more fasteners. The fiber is configured to detect strain on the structure from the one or more fasteners. Strain patterns are derivable from sensed data from the optical fiber, and any deviation in strain value greater than a threshold value at a particular fiber position along the optical fiber is indicative of a missing, damaged, or loosened fastener amongst the one or more of fasteners corresponding to that particular fiber position.
Claims19
A fastener health monitoring system comprising:
- a structure including a first component and a second component;
- one or more fasteners securing the first component to the second component;
- an optical fiber arranged adjacent to the one or more fasteners, the optical fiber configured to detect strain on the structure from the one or more fasteners;
- and
- an interrogation system including an interrogator, the interrogator including a light source and a receiver configured to:
- analyze reflected light from the optical fiber as sensed data;
- determine a baseline strain pattern comprising strain as a function of distance along the optical fiber when the one or more fasteners are not missing, loosened, or broken;
- after the baseline strain pattern is determined, determine a strain pattern comprising strain as a function of distance along the optical fiber;
- detect, by comparing the strain pattern to the baseline strain pattern, a deviation of the strain pattern relative to the baseline strain pattern that is greater than a threshold value;
- analyze, for a structure with an applied load, local spatial variations of detected strain associated with a plurality of neighboring fasteners;
- associate, based on the detected deviation of the strain pattern and the analysis of local spatial variations, the detected deviation with a fiber position corresponding to a fastener of the one or more fasteners;
- and
- in response to associating the deviation of the strain pattern with the fiber position corresponding to the fastener of the one or more fasteners, determine that the fastener of the one or more fasteners is missing, loosened, or broken.
A method of detecting a missing or malfunctioning fastener in a structure, the method comprising:
- arranging an optical fiber along one or more fasteners connecting a first component to a second component of the structure, wherein the optical fiber is disposed within a shadow of each fastener of the one or more fasteners, the shadow defining an area surrounding each fastener within a distance from the fastener where strain is detectable from the fastener, wherein the distance is not more than three times a diameter of a fastener hole through which the fastener is inserted to secure the first component to the second component;
- directing light down the optical fiber;
- receiving reflected light from the optical fiber;
- analyzing the reflected light to determine a strain pattern along the optical fiber;
- determining a baseline strain pattern comprising strain as a function of distance along the optical fiber when the one or more fasteners are not missing, loosened, or broken;
- after the baseline strain pattern is determined, determining a strain pattern comprising strain as a function of distance along the optical fiber;
- detecting, by comparing the strain pattern to the baseline strain pattern, a deviation of the strain pattern relative to the baseline strain pattern that is greater than a threshold value and associated with a fiber position corresponding to a fastener of the one or more fasteners;
- analyzing, for a structure with an applied load, local spatial variations of detected strain associated with a plurality of neighboring fasteners;
- associating, based on the detected deviation of the strain pattern and the analysis of local spatial variations, the detected deviation with a fiber position corresponding to a fastener of the one or more fasteners;
- and
- in response to associating the deviation of the strain pattern with the fiber position corresponding to the fastener of the one or more fasteners, determining that the fastener of the one or more fasteners is missing, loosened, or broken.
Dependencies are inferred from the claim text.