Device and method to detect cracks in the countersink of a fastener
First Claim
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1. A method for detecting cracks in a structure, the method comprising:
- generating a first Lamb wave at a first location, wherein the first Lamb wave propagates towards a fastener in the structure;
detecting, via a detector at a first detector position, a first signal corresponding to the first Lamb wave subsequent to the first Lamb wave'"'"'s interaction with the fastener;
generating a second Lamb wave at the first location;
detecting, at a second detector position, a second signal corresponding to the second Lamb wave subsequent to the second Lamb wave'"'"'s interaction with the fastener, wherein the second detector position is symmetric to the first detector position relative to the fastener and the first location; and
calculating a first symmetry parameter from the first signal and the second signal, wherein the first symmetry parameter comprises a value representing a comparison of an amplitude of the first signal and an amplitude of the second signal.
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Abstract
Disclosed are methods and systems to nondestructively detect cracks at or near a countersink of a fastener, such as a rivet, in a thin walled structure using Lamb waves. Generation and detection of Lamb waves at symmetric locations relative to the fastener provides signals used to calculate a symmetry parameter. The symmetry parameter represents a comparison of the relative amplitudes of the detected Lamb wave signals and provides a simple indication of whether a crack exists.
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Citations
21 Claims
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1. A method for detecting cracks in a structure, the method comprising:
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generating a first Lamb wave at a first location, wherein the first Lamb wave propagates towards a fastener in the structure; detecting, via a detector at a first detector position, a first signal corresponding to the first Lamb wave subsequent to the first Lamb wave'"'"'s interaction with the fastener; generating a second Lamb wave at the first location; detecting, at a second detector position, a second signal corresponding to the second Lamb wave subsequent to the second Lamb wave'"'"'s interaction with the fastener, wherein the second detector position is symmetric to the first detector position relative to the fastener and the first location; and calculating a first symmetry parameter from the first signal and the second signal, wherein the first symmetry parameter comprises a value representing a comparison of an amplitude of the first signal and an amplitude of the second signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for detecting cracks in a structure, the method comprising:
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generating a first Lamb wave at a first location, wherein the first Lamb wave propagates towards a fastener in the structure; detecting, at a first detector position, a first signal corresponding to the first Lamb wave subsequent to the first Lamb wave'"'"'s interaction with the fastener; generating a second Lamb wave at a second location, wherein the second location is symmetric to the first location relative to the fastener and the first detector position; detecting, at the first detector position, a second signal corresponding to the second Lamb wave subsequent to the second Lamb wave'"'"'s interaction with the fastener; and calculating a first symmetry parameter from the first signal and the second signal, wherein the first symmetry parameter comprises a value representing a comparison of an amplitude of the first signal and an amplitude of the second signal. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A system for detecting cracks in a structure comprising:
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a Lamb wave generation device that generates a first Lamb wave that propagates towards a fastener in the structure and that generates a second Lamb wave that propagates towards the fastener; a Lamb wave detection device that provides a first signal corresponding to the first Lamb wave subsequent to the first Lamb wave'"'"'s interaction with the fastener and provides a second signal corresponding to the second Lamb wave subsequent to the second Lamb wave'"'"'s interaction with the fastener; a positioning system that positions the Lamb wave detection device to measure the first signal at a first position and to measure the second signal at second position, wherein the first position is symmetric to the second position relative to the fastener and the Lamb wave generation device; and a computing system comprising, one or more processors, and a memory system comprising one or more non-transitory computer readable media storing instructions that, when executed by the one or more processors, causes the computing system to calculate a symmetry parameter from the first signal and second signal and compare the symmetry parameter to a predetermined threshold, wherein the symmetry parameter comprises a value representing a comparison of an amplitude of the first signal and an amplitude of the second signal. - View Dependent Claims (18, 19, 20)
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21. A method for detecting cracks in a structure, the method comprising:
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generating a first Lamb wave at a first location, wherein the first Lamb wave propagates towards a fastener in the structure; detecting, at a first detector position, a first signal corresponding to the first Lamb wave subsequent to the first Lamb wave'"'"'s interaction with the fastener; detecting, at a second detector position, a second signal corresponding to the first Lamb wave subsequent to the first Lamb wave'"'"'s interaction with the fastener, wherein the second detector position is symmetric to the first detector position relative to the fastener and the first location; and calculating a first symmetry parameter from the first signal and the second signal, wherein the first symmetry parameter comprises a value representing a comparison of an amplitude of the first signal and an amplitude of the second signal.
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Specification