Nonlinear ultrasonic scanning to detect material defects
First Claim
1. A method of detecting defects in a material, comprising the steps of:
- mixing waves of a first frequency with waves of a second frequency at an interaction zone in said material to generate at least one of a difference wave and a sum wave in said interaction zone, said difference wave occurring at said first frequency minus said second frequency and said sum wave occurring at said first frequency plus said second frequency;
measuring the amplitude of at least one of said difference wave and said sum wave; and
computing a value defined as the amplitude of at least one of said difference wave and said sum wave divided by the product of the amplitude of the waves of said first frequency and the amplitude of the waves of said second frequency, wherein said value is an indication of defects in said interaction zone.
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Abstract
A method and system are provided to detect defects in a material. Waves of known frequency(ies) are mixed at an interaction zone in the material. As a result, at least one of a difference wave and a sum wave are generated in the interaction zone. The difference wave occurs at a difference frequency and the sum wave occurs at a sum frequency. The amplitude of at least one nonlinear signal based on the sum and/or difference waves is then measured. The nonlinear signal is defined as the amplitude of one of the difference wave and sum wave relative to the product of the amplitude of the surface waves. The amplitude of the nonlinear signal is an indication of defects (e.g., dislocation dipole density) in the interaction zone.
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Citations
20 Claims
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1. A method of detecting defects in a material, comprising the steps of:
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mixing waves of a first frequency with waves of a second frequency at an interaction zone in said material to generate at least one of a difference wave and a sum wave in said interaction zone, said difference wave occurring at said first frequency minus said second frequency and said sum wave occurring at said first frequency plus said second frequency; measuring the amplitude of at least one of said difference wave and said sum wave; and computing a value defined as the amplitude of at least one of said difference wave and said sum wave divided by the product of the amplitude of the waves of said first frequency and the amplitude of the waves of said second frequency, wherein said value is an indication of defects in said interaction zone. - View Dependent Claims (2, 3, 4, 5, 6, 7, 18, 19)
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8. A system for detecting defects in a material comprising:
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acoustic means for causing waves of a first ultrasonic frequency to mix with waves of a second ultrasonic frequency at an interaction zone in said material such that a difference wave and a sum wave are generated in said interaction zone, said difference wave occurring at said first frequency minus said second frequency and said sum wave occurring at said first frequency plus said second frequency; at least one acoustic transducer positioned to detect the amplitude of at least one of said difference wave and said sum wave; and means coupled to said acoustic means and said at least one acoustic transducer for determining a product of the amplitude of said waves of said first ultrasonic frequency and the amplitude of said waves of said second ultrasonic frequency and for monitoring the amplitude of a nonlinear signal defined as the amplitude of one of said difference wave and said sum wave relative to said product of the amplitude of said waves of said first ultrasonic frequency and the amplitude of said waves of said second ultrasonic frequency, wherein the amplitude of said nonlinear signal is an indication of defects in said interaction zone. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17)
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20. A method of detecting dislocation dipoles in a material, comprising the steps of:
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mixing fixed amplitude waves of a first frequency with fixed amplitude waves of a second frequency at an interaction zone in said material to generate at least one of a difference wave and a sum wave in said interaction zone, said difference wave occurring at said first frequency minus said second frequency and said sum wave occurring at said first frequency plus said second frequency; and measuring the amplitude of at least one of said difference wave and said sum wave as an indication of dislocation dipoles in said interaction zone.
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Specification