Crack growth measurement network with primary and shunt optical fibers
First Claim
1. An apparatus for optically measuring the propagation of a crack in a structure, comprising:
- a substrate attachable to the structure in which the crack is expected to propagate;
a primary optical fiber attached to said substrate, said primary optical fiber having means for receiving light energy at a first end and means for delivery light energy at a second end; and
a shunt optical path optically connected to said primary optical fiber in optical parallel with a portion of said primary optical fiber so that as the crack propagates the shunt optical path will be stressed by crack propagation causing a change in the light energy available at the second end of the primary optical path.
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Accused Products
Abstract
A fiber optic crack propagation measurement apparatus including an input optical fiber for receiving light energy and an output optical fiber connected to deliver light energy to a detector is disclosed. A plurality of shunt optical fibers are connected in parallel between the input and output optical fibers. The input optical fibers, output optical fibers and shunt optical fibers are secured to a structure in which stresses are expected to cause the advancement of a crack. As the crack grows, individual shunt fibers are broken, reducing the amount of light energy delivered to the detector. Detector signals are generated indicative of the light energy received thereby to report the advancement of the crack. In one embodiment, wavelength division multiplexing techniques are employed so that multiple crack measuring units can be monitored over a single monitoring optical fiber.
36 Citations
26 Claims
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1. An apparatus for optically measuring the propagation of a crack in a structure, comprising:
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a substrate attachable to the structure in which the crack is expected to propagate; a primary optical fiber attached to said substrate, said primary optical fiber having means for receiving light energy at a first end and means for delivery light energy at a second end; and a shunt optical path optically connected to said primary optical fiber in optical parallel with a portion of said primary optical fiber so that as the crack propagates the shunt optical path will be stressed by crack propagation causing a change in the light energy available at the second end of the primary optical path. - View Dependent Claims (2, 3, 4, 5, 6, 7, 13)
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8. An apparatus for measuring the propagation of a crack in a structure, comprising:
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an input optical fiber for receiving light energy; an output optical fiber for delivering light energy to a detector; a plurality of shunt optical fibers, each shunt optical fiber having a first end optically connected to receive light energy from said input optical fiber and having a second end optically connected to deliver light energy received from said input optical fiber to said output optical fiber; means for attaching said shunt optical fibers to said structure in a predetermined spatial pattern in an area of potential structural stress; and said detector comprising means responsive to the amount of light energy received from said output optical fiber for detecting the propagation of a crack in the area of potential structural stress. - View Dependent Claims (9, 10, 11, 12)
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14. An apparatus for measuring the propagation of a crack in a structure, comprising:
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a stress sensing optical fiber means embedded in said structure in a predetermined spatial pattern, said stress sensing means comprising an input optical fiber, an output optical fiber, and a plurality of shunt path optical fibers, each shunt path optical fiber having a first end optically connected to receive light energy from said input optical fiber and having a second end optically connected to deliver light energy received from said input optical fiber to said output optical fiber; connecting means for connecting light energy to said input optical fiber and for connecting light energy from said output optical fiber to a detector; and said detector comprising means responsive to the amount of light energy received from said output optical fiber for detecting the propagation of a crack in said structure. - View Dependent Claims (15)
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16. An optical system for measuring crack propagation in a structure, comprising:
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a plurality of crack propagation measuring means each having an input optical fiber for receiving input light energy, an output optical fiber and a shunt optical path for conveying from said input optical fiber to said output optical fiber an amount of light energy indicative of the propagation of a crack in said structure; a monitoring fiber optically connected to the output optical fibers of each of said plurality of crack propagation measuring means for receiving light energy conveyed thereby; optical source means for coupling an individual one of a plurality of optically distinctive light energy signals to each of said input optical fibers; and detection means connected to receive light energy signals from said monitoring fiber for separately detecting changes in the amount of light energy of each of said optically distinctive light energy signals and for generating signals representing such changes in detected light energy. - View Dependent Claims (17, 18, 19, 20)
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21. An optical system for measuring crack propagation in a structure, comprising:
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a plurality of crack propagation measuring means each having an input optical fiber for receiving input light energy, an output optical fiber and a shunt optical path for conveying from said input optical fiber to said output optical fiber, an amount of light energy indicative of the propagation of a crack in said structure; a monitoring fiber optically connected to the output optical fibers of each of said plurality of crack propagation measuring means for receiving light energy conveyed thereby; optical source means for coupling distinctive light energy signals to each of said input fibers; and detection means connected to receive said distinctive light energy signals from said monitoring fiber, for separately detecting changes in the amount of light energy in each of said received distinctive light energy signals and for generating signals representing such changes in detected light energy.
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22. A method of optically measuring the propagation of a crack in a structure, said method comprising:
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attaching a plurality of crack detection fibers to said structure in an area of anticipated crack propagation; optically connecting each of said crack detection fibers to an input optical fiber; optically connecting each of said crack detection fibers to an output optical fiber; applying optical energy to said input optical fiber; and detecting reductions in the amount of optical energy conveyed by said output optical fiber to measure crack propagation. - View Dependent Claims (23, 24, 25, 26)
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Specification