Strain Guage and Fracture Indicator Based on Composite Film Including Chain-Structured Magnetically Active Particles
First Claim
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1. A strain gauge comprising:
- a composite film having an axial direction and a thickness, comprisinga non-metallic matrix,magnetically active particles included in the non-metallic matrix,wherein at least a portion of the magnetically active particles form a chain structure oriented substantially parallel to the axial direction; and
two or more leads affixed to the composite film, each affixed to the composite film a predetermined distance from another, so as to form a lead structure oriented substantially parallel to the axial direction, wherein each of the two or more leads is electrically coupled with at least one magnetically active particle in the chain structure.
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Abstract
The disclosed subject matter provides a strain gauge which includes a composite film including a non-metallic matrix and magnetically active particles. At least a portion of the magnetically active particles form one or more chain structures, such that the resistivity of the composite film can vary in response to an applied strain on the composite film. The strain gauge also includes two or more leads affixed to the composite film and electrically coupled with the chain structures. Methods of fabrication and methods of use of the strain gauge based on chain-structured magnetically active particles included in a non-metallic matrix are also disclosed.
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Citations
32 Claims
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1. A strain gauge comprising:
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a composite film having an axial direction and a thickness, comprising a non-metallic matrix, magnetically active particles included in the non-metallic matrix, wherein at least a portion of the magnetically active particles form a chain structure oriented substantially parallel to the axial direction; and two or more leads affixed to the composite film, each affixed to the composite film a predetermined distance from another, so as to form a lead structure oriented substantially parallel to the axial direction, wherein each of the two or more leads is electrically coupled with at least one magnetically active particle in the chain structure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 32)
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16. A method of preparing a thin film strain gauge, comprising:
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applying a first magnetic field to a first mixture including magnetically active particles and a first liquid prepolymer, such that at least a portion of the magnetically active particles form a chain structure oriented substantially parallel to an axial direction; curing the first liquid prepolymer; and affixing two or more leads to the first mixture at a predetermined distance from another, so as to form a lead structure oriented substantially parallel to the axial direction, wherein each of the two or more leads is electrically coupled with at least one magnetically active particle in the chain structure. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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24. A method for measuring strain, comprising:
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applying a load or permitting a load to be exerted on a strain gauge to cause a strain to be sustained on at least a portion of the strain gauge, the strain gauge comprising; a composite film having an axial direction and a thickness, comprising a non-metallic matrix, magnetically active particles included in the non-metallic matrix, wherein at least a portion of the magnetically active particles form a chain structure oriented substantially parallel to the axial direction; and two or more leads affixed to the composite film, each affixed to the composite film a predetermined distance from another, so as to form a lead structure oriented substantially parallel to the axial direction, wherein each of the two or more leads is electrically coupled with at least one magnetically active particle in the chain structure; determining the value of the strain sustained on the portion of the strain gauge based on the difference of (1) the resistivity of a portion of the strain gauge between two selected leads, the two selected leads encompassing the portion of the strain gauge under the strain, and (2) the resistivity between the two selected leads in the absence of the strain. - View Dependent Claims (25)
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26. A method of detecting crack in an object, comprising:
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(a) attaching a strain gauge to the object, the strain gauge comprising; a composite film having an axial direction and a thickness, comprising a non-metallic matrix, magnetically active particles included in the non-metallic matrix, wherein at least a portion of the magnetically active particles form a chain structure oriented substantially parallel to the axial direction; and two or more leads affixed to the composite film, each affixed to the composite film a predetermined distance from another, so as to form a lead structure oriented substantially parallel to the axial direction, wherein each of the two or more leads is electrically coupled with at least one magnetically active particle in the chain structure; (b) applying a load or permitting a load to be exerted on the object so as to deform the object, such that a strain is sustained on at least a portion of the axial direction of the strain gauge; (c) determining a resistivity-associated property of the portion of the strain gauge; (d) determining whether a crack in the object has occurred based on whether the property determined in (c) exceeds a predetermined threshold. - View Dependent Claims (27, 28, 29)
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30. A method of detecting an initiation of a crack in an object, comprising:
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attaching a strain gauge to the object, the strain gauge comprising; a composite film having an axial direction and a thickness, comprising a non-metallic matrix, magnetically active particles included in the non-metallic matrix, wherein at least a portion of the magnetically active particles form a chain structure oriented substantially parallel to the axial direction; and two or more leads affixed to the composite film, each affixed to the composite film a predetermined distance from another, so as to form a lead structure oriented substantially parallel to the axial direction, wherein each of the two or more leads is electrically coupled with at least one magnetically active particle in the chain structure; applying a load or permitting a load to be exerted on the object so as to deform the object, such that a strain is sustained on at least a portion of the axial direction of the strain gauge; continuously measuring a resistivity-associated property of the portion of the strain gauge; determining whether an initiation of a crack in the object has occurred based on a sudden change in the value of the resistivity-associated property measured at an instant time relative to the value of the resistivity-associated property measured in a previous time. - View Dependent Claims (31)
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Specification