System and method for detecting cracks and their location
First Claim
1. A system for detecting cracks and their location in a structure, comprising:
- at least one circuit coupled to a structure, each said circuit having a plurality of capacitive strain sensors coupled sequentially and in parallel to one another wherein, when excited by a variable magnetic field, said circuit has a resonant frequency that is (i) a first resonant frequency when said circuit is in an unstrained state, (ii) one of a plurality of second resonant frequencies when said circuit is in a strained state, (iii) a third resonant frequency when said circuit has been broken and the remaining active circuit is in an unstrained state, said third resonant frequency being substantially different in frequency from said first resonant frequency, and (iv) one of a plurality of fourth resonant frequencies when said circuit is broken and the remaining active circuit is in a strained state, said fourth resonant frequencies being substantially different in frequency from said plurality of second resonant frequencies, each of said plurality of second resonant frequencies being indicative of a region of said circuit that is experiencing strain induced by strain in a region of the structure in proximity to said region of said circuit, said third resonant frequency being indicative of a region of said circuit that is broken, and each of said fourth resonant frequencies being indicative of a region of said remaining active circuit that is strained;
an inductor electrically coupled to one end of each said circuit; and
a magnetic field response recorder for wirelessly transmitting said variable magnetic field to said inductor and for sensing said resonant frequency of said circuit so-excited by said variable magnetic field.
1 Assignment
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Accused Products
Abstract
A system and method are provided for detecting cracks and their location in a structure. A circuit coupled to a structure has capacitive strain sensors coupled sequentially and in parallel to one another. When excited by a variable magnetic field, the circuit has a resonant frequency that is different for unstained and strained states. In terms of strained states, the resonant frequency is indicative of a region of the circuit that is experiencing strain induced by strain in a region of the structure in proximity to the region of the circuit. An inductor is electrically coupled to one end of each circuit. A magnetic field response recorder wirelessly transmits the variable magnetic field to the inductor and senses the resonant frequency of the circuit so-excited by the variable magnetic field.
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Citations
31 Claims
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1. A system for detecting cracks and their location in a structure, comprising:
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at least one circuit coupled to a structure, each said circuit having a plurality of capacitive strain sensors coupled sequentially and in parallel to one another wherein, when excited by a variable magnetic field, said circuit has a resonant frequency that is (i) a first resonant frequency when said circuit is in an unstrained state, (ii) one of a plurality of second resonant frequencies when said circuit is in a strained state, (iii) a third resonant frequency when said circuit has been broken and the remaining active circuit is in an unstrained state, said third resonant frequency being substantially different in frequency from said first resonant frequency, and (iv) one of a plurality of fourth resonant frequencies when said circuit is broken and the remaining active circuit is in a strained state, said fourth resonant frequencies being substantially different in frequency from said plurality of second resonant frequencies, each of said plurality of second resonant frequencies being indicative of a region of said circuit that is experiencing strain induced by strain in a region of the structure in proximity to said region of said circuit, said third resonant frequency being indicative of a region of said circuit that is broken, and each of said fourth resonant frequencies being indicative of a region of said remaining active circuit that is strained; an inductor electrically coupled to one end of each said circuit; and a magnetic field response recorder for wirelessly transmitting said variable magnetic field to said inductor and for sensing said resonant frequency of said circuit so-excited by said variable magnetic field. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for detecting cracks and their location in a structure, comprising:
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at least one circuit partially coupled to a structure, each said circuit having N capacitive strain sensors coupled sequentially and in parallel to one another with a first through (N-1) capacitive stain sensors coupled to the structure and an N-th capacitive strain sensor being uncoupled from the structure wherein, when excited by a variable magnetic field, said circuit has a resonant frequency that is (i) a first resonant frequency when said circuit is in an unstrained state, (ii) one of a plurality of second resonant frequencies when said circuit is in a strained state, (iii) a third resonant frequency when said circuit has been broken and the remaining active circuit is in an unstrained state, said third resonant frequency being substantially different in frequency from said first resonant frequency, and (iv) one of a plurality of fourth resonant frequencies when said circuit is broken and the remaining active circuit is in a strained state, said fourth resonant frequencies being substantially different in frequency from said plurality of second resonant frequencies, each of said plurality of second resonant frequencies being indicative of a region of said circuit that is experiencing strain induced by strain in a region of the structure in proximity to said region of said circuit, said third resonant frequency being indicative of a region of said circuit that is broken, and each of said fourth resonant frequencies being indicative of a region of said remaining active circuit that is strained; an inductor electrically coupled to one end of each said circuit via said N-th capacitive strain sensor associated therewith; and a magnetic field response recorder for wirelessly transmitting said variable magnetic field to said inductor and for sensing said resonant frequency of said circuit so-excited by said variable magnetic field. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method of detecting cracks and their location in a structure, comprising the steps of:
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providing a circuit that includes a plurality of capacitive strain sensors coupled sequentially and in parallel to one another; coupling at least a portion of said circuit to a structure; coupling an inductor to one end of said circuit; inducing a variable magnetic field in said inductor wherein, when excited by said variable magnetic field, said circuit has a resonant frequency that is (i) a first resonant frequency when said circuit is in an unstrained state, (ii) one of a plurality of second resonant frequencies when said circuit is in a strained state, (iii) a third resonant frequency when said circuit has been broken and the remaining active circuit is in an unstrained state, said third resonant frequency being substantially different in frequency from said first resonant frequency, and (iv) one of a plurality of fourth resonant frequencies when said circuit is broken and the remaining active circuit is in a strained state, said fourth resonant frequencies being substantially different in frequency from said plurality of second resonant frequencies, each of said plurality of second resonant frequencies being indicative of a region of said circuit that is experiencing strain induced by strain in a region of the structure in proximity to said region of said circuit, said third resonant frequency being indicative of a region of said circuit that is broken, and each of said fourth resonant frequencies being indicative of a region of said remaining active circuit that is strained; and sensing said resonant frequency of said circuit so-excited by said variable magnetic field. - View Dependent Claims (16, 17, 18, 19, 20)
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21. A system for detecting cracks and their location in a structure, comprising:
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at least one circuit coupled to a structure, each said circuit having at least three capacitive strain sensors wherein, when excited by a variable magnetic field, said circuit has a resonant frequency that is (i) a first resonant frequency when said circuit is in an unbroken state, and (ii) one of a plurality of second resonant frequencies when said circuit is in a broken state, each of said plurality of second resonant frequencies being indicative of a region of said circuit that is broken; at least two inductors electrically coupled to each said capacitive strain sensor, wherein each inductor is positioned between two capacitive strain sensors; and a magnetic field response recorder for wirelessly transmitting said variable magnetic field to said one or more inductors and for sensing said resonant frequency of said circuit so-excited by said variable magnetic field. - View Dependent Claims (22, 23, 24, 25, 26)
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27. A method of detecting product tampering, comprising the steps of:
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providing a circuit that comprises at least three capacitive strain sensors; coupling at least a portion of said circuit to a structure; coupling at least two inductors to each capacitive strain sensor, wherein each inductor is positioned between two capacitive strain sensors; inducing a variable magnetic field in each inductor wherein, when excited by said variable magnetic field, said circuit has a resonant frequency that is (i) a first resonant frequency when said circuit is in an unstrained state, and (ii) one of a plurality of second resonant frequencies when said circuit is in a strained state, each of said plurality of second resonant frequencies being indicative of a region of said circuit that is experiencing strain induced by strain in a region of the structure in proximity to said region of said circuit; and sensing said resonant frequency of said circuit so-excited by said variable magnetic field. - View Dependent Claims (28, 29, 30, 31)
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Specification