Composite inspection

{
  "publication_number": "US10345267B2",
  "country": "US",
  "kind": "B2",
  "title": "Composite inspection",
  "abstract": "A method of detecting material changes in a composite structure is presented. A pulsed laser beam is directed towards the composite structure comprised of a number of composite materials. Wide-band ultrasonic signals are formed in the composite structure when radiation of the pulsed laser beam is absorbed by the composite structure. The wide-band ultrasonic signals are detected to form data. The data comprises a number of ultrasonic A-scans. The data is processed to identify a plurality of frequency measurements for each of the number of ultrasonic A-scans. A frequency image is displayed using the plurality of frequency measurements. The material changes are represented in the frequency image.",
  "claims": [
    "1. A method of detecting material changes in a composite structure, the method comprising: directing a pulsed laser beam towards the composite structure comprised of a number of composite materials, wherein wide-band ultrasonic signals are formed in the composite structure when radiation of the pulsed laser beam is absorbed by the composite structure; detecting the wide-band ultrasonic signals to form data, wherein the data comprises a number of ultrasonic A-scans; processing the data to identify a plurality of frequency measurements for each of the number of ultrasonic A-scans; and displaying a frequency image using the plurality of frequency measurements, wherein the material changes are represented in the frequency image, wherein a first axis of the frequency image is one of time or depth, and wherein an intensity of each pixel of the frequency image is indicative of a frequency measurement of the plurality of frequency measurements.",
    "2. The method of claim 1, wherein processing the data comprises: applying a moving window to each of the number of ultrasonic A-scans, wherein the moving window is a filter; and determining at least one of a mean frequency or a maximum frequency within the moving window.",
    "3. The method of claim 2, wherein the moving window has a Gaussian shape.",
    "4. The method of claim 1 further comprising: determining whether undesirable conditions are present in the composite structure by analyzing the frequency image, wherein the undesirable conditions include the material changes.",
    "5. The method of claim 1, wherein the plurality of frequency measurements are selected from at least one of mean frequencies or maximum frequencies.",
    "6. The method of claim 1, wherein processing the data comprises: determining a maximum frequency of a windowed signal of an A-scan of the number of ultrasonic A-scans using the equation S n =Σ k=1 p a k *S n-k, where p is a quantity of coefficients and S n is an A-scan signal at sample point n.",
    "7. The method of claim 1, wherein processing the data to identify the plurality of frequency measurements comprises: determining a mean frequency of a windowed signal of an ultrasonic A-scan of the number of ultrasonic A-scans using an autocorrelation function of a complex, analytic representation of the windowed signal of the ultrasonic A-Scan, {circumflex over (R)}(t), according to at least one of equation f mean = 1 2 ⁢ π ⁢ ⁢ i ⁢ R. ⁡ (0) R ⁡ (0) = 1 2 ⁢ π ⁢ ∅. ⁡ (0), where R(0) is the magnitude of complex autocorrelation function, {circumflex over (R)}(t), at time zero, and Ø(0) is the phase of the complex autocorrelation function at the time zero, and a dot above a function represents a time derivative of that function, or for an N-point sampled version of the A-Scan, f mean = tan - 1 ⁡ [im ⁢ R N ⁡ (1) re ⁢ R N ⁡ (1)], where R N (1) is the N-point complex autocorrelation function R N evaluated at sample point 1, im refers to the imaginary part of the complex autocorrelation function and re refers to the real part of the complex autocorrelation function.",
    "8. The method of claim 1, wherein the wide-band ultrasonic signals are detected using a point-like optical detector.",
    "9. A method of non-destructive inspection capable of detecting inconsistencies previously masked by a structure signal, the method comprising: directing a pulsed laser beam towards a composite structure comprised of a plurality of layers, wherein a number of wide-band ultrasonic signals are formed in the composite structure when radiation of the pulsed laser beam is absorbed by the composite structure; detecting the wide-band ultrasonic signals to form data, wherein the data comprises a plurality of ultrasonic A-scans for the composite structure; applying a moving window to each of the plurality of ultrasonic A-scans to form windowed signals, wherein the moving window is a filter; determining a frequency measurement within the windowed signals for each of the plurality of ultrasonic A-scans; removing spectral components of a structure signal from an A-scan spectrum of each of the plurality of ultrasonic A-scans using the frequency measurement; performing an interpolation on the A-scan spectrum of the each of the plurality of ultrasonic A-scans after removing the spectral components of the structure signal to form interpolated A-scan spectrum data; and determining whether an inconsistency is present in the composite structure based on the interpolated A-scan spectrum data.",
    "10. The method of claim 9 further comprising: Fourier transforming each of the plurality of ultrasonic A-scans to form the A-scan spectrum of each of the plurality of ultrasonic A-scans; and performing an inverse Fourier transformation on the interpolated A-scan spectrum data to form a plurality of structureless ultrasonic A-scans.",
    "11. The method of claim 10 further comprising: filtering a structureless B-scan image formed from the plurality of structureless ultrasonic A-scans, wherein determining whether an inconsistency is present in the composite structure based on the interpolated A-scan spectrum data comprises analyzing the structureless B-scan image for an inconsistency.",
    "12. The method of claim 11, wherein filtering the structureless B-scan image comprises using a low-pass filter on the structureless B-scan image.",
    "13. The method of claim 9, wherein the frequency measurement is selected from a mean frequency or a maximum frequency.",
    "14. The method of claim 13, wherein the mean frequency is determined using an autocorrelation function of a complex, analytic representation of a windowed signal of an ultrasonic A-Scan, {circumflex over (R)}(t), according to at least one of the equation f mean = 1 2 ⁢ π ⁢ ⁢ i ⁢ R. ⁡ (0) R ⁡ (0) = 1 2 ⁢ π ⁢ ∅. ⁡ (0), where R(0) is a magnitude of complex autocorrelation function, {circumflex over (R)}(t), at time zero, and Ø(0) is the phase of the complex autocorrelation function at the time zero, and a dot above a function represents the time derivative of that function, or for an N-point sampled version of the A-Scan, according to the equation f mean = tan - 1 ⁡ [im ⁢ R N ⁡ (1) re ⁢ R N ⁡ (1)], where R N (1) is the N-point complex autocorrelation function R N evaluated at sample point 1, im refers to the imaginary part of the complex autocorrelation function and re refers to the real part of the complex autocorrelation function.",
    "15. The method of claim 13, wherein the maximum frequency is determined using equation S n =Σ k=1 p a k *S n-k, where p is a quantity of coefficients and S n is an A-scan signal at sample point n.",
    "16. A method of non-destructive inspection capable of detecting inconsistencies previously masked by a structure signal, the method comprising: obtaining data for a composite structure using a laser ultrasound inspection system; determining a width and a frequency of spectral components of the structure signal in the data; removing the spectral components of the structure signal from the data in a frequency domain; performing an interpolation routine to fill in a region of an A-scan spectrum left empty by removing the spectral components of the structure signal to form interpolated data; and performing an inverse Fourier transformation on the interpolated data to form a processed A-scan with the structure signal removed; and determining whether an inconsistency is present in the composite structure based on the A-scan with the structure signal removed.",
    "17. The method of claim 16 further comprising: filtering the processed A-scan to form filtered data; and displaying the filtered data in a structureless B-scan image, wherein determining whether an inconsistency is present in the composite structure based on the A-scan with the structure signal removed comprises analyzing the structureless B-scan image for an inconsistency.",
    "18. The method of claim 16, wherein the frequency of the spectral components of the structure signal is estimated using equation S n =Σ k=1 p a k *S n-k, where p is a quantity of coefficients and S n is an A-scan signal at sample point n.",
    "19. The method of claim 16, wherein the frequency of the spectral components of the structure signal is estimated using an autocorrelation function of a complex, analytic representation of a windowed signal of an ultrasonic A-Scan, {circumflex over (R)}(t), according to at least one of equation f mean = 1 2 ⁢ π ⁢ ⁢ i ⁢ R. ⁡ (0) R ⁡ (0) = 1 2 ⁢ π ⁢ ∅. ⁡ (0), where R(0) is a magnitude of complex autocorrelation function, {circumflex over (R)}(t), at time zero, and Ø(0) is the phase of the complex autocorrelation function at the time zero, and a dot above a function represents the time derivative of that function, or for an N-point sampled version of the A-Scan, f mean = tan - 1 ⁡ [im ⁢ R N ⁡ (1) re ⁢ ⁢ R N ⁡ (1)], where R N (1) is the N-point complex autocorrelation function R N evaluated at sample point 1, im refers to the imaginary part of the complex autocorrelation function and re refers to the real part of the complex autocorrelation function.",
    "20. The method of claim 16, wherein a spectral region around the spectral components of the structure signal is a mean frequency±two times a width of a structural signal spectrum in the frequency domain, wherein the width of the structural signal spectrum in the frequency domain is a width of the A-scan spectrum associated with spectral components.",
    "21. The method of claim 20, wherein the width of the structural signal spectrum in the frequency domain is estimated using an autocorrelation function of a complex, analytic representation of the windowed signal of an ultrasonic A-Scan, {circumflex over (R)}(t), and wherein for an N-point sampled version of the A-Scan, width = 2 N ⁡ [1 -  R N ⁡ (1)  R N ⁡ (0)], where |R N (1)| is the magnitude of the N-point complex autocorrelation function R N evaluated at sample point 1 and R N (0) is the N-point complex autocorrelation function R N evaluated at sample point 0."
  ],
  "description_excerpt": "This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/270,529, filed Dec. 21, 2015, and entitled “Composite Inspection.”\n\n1. Field\n\nThe present disclosure relates generally to non-destructive inspection and, in particular, to performing non-destructive inspection on a layered structure. Still more particularly, the present disclosure relates to a method and apparatus for detecting material changes or other inconsistencies in a composite structure.\n\n2. Background\n\nIn manufacturing aircraft, vehicles, and other structures, inspection of parts used to form these structures is often performed to determine whether the parts will have desired parameters for a desired performance of the part. Additionally, the structures and parts are inspected as part of normal maintenance when the aircraft, vehicles, and other structures are in use.\n\nNon-destructive testing is commonly performed on these parts. Non-destructive testing is used to evaluate the properties of a part without altering the ability to use the part in service.\n\nUltrasound testing is a type of non-destructive testing. Ultrasound testing is often used to perform inspections on aircraft parts that include, or are comprised of, composite materials. Ultrasound testing involves transmitting sound waves through a test object, such as an aircraft part or structure.\n\nUltrasound testing is commonly performed using a transducer. The transducer is configured to send sound waves into a test object and detect a response to the sound waves.",
  "cpc": [
    "G01N 29/0645",
    "B64F 5/60",
    "G01N 2021/1706",
    "G01N 21/1702",
    "G01N 2291/015",
    "G01N 2291/0231",
    "G01N 2291/044",
    "G01N 2291/2694",
    "G01N 29/043",
    "G01N 29/11",
    "G01N 29/2418",
    "G01N 29/343",
    "G01N 29/348",
    "G01N 29/36",
    "G01N 29/4454",
    "G01N 29/449",
    "G01N 29/46",
    "G01N 29/50"
  ],
  "ipc": [
    "G01N 21/17",
    "G01N 29/06",
    "G01N 29/24",
    "B64F 5/60",
    "G01N 29/04",
    "G01N 29/11",
    "G01N 29/34",
    "G01N 29/44",
    "G01N 29/46",
    "G01N 29/50"
  ],
  "assignees": [
    "Boeing Co"
  ],
  "inventors": [
    "Matthew O'Donnell",
    "Ivan Pelivanov",
    "Steven Kenneth Brady",
    "Gary Ernest Georgeson",
    "Jeffrey Reyner Kollgaard",
    "William P. Motzer",
    "Clarence Lavere Gordon, III",
    "Jill Paisley Bingham",
    "Alan F. Stewart",
    "James C. Kennedy"
  ],
  "filing_date": "2016-03-15",
  "publication_date": "2019-07-09",
  "grant_date": "2019-07-09",
  "priority_date": "2015-12-21",
  "application_number": "US-201615070261-A",
  "family_id": "57113205",
  "cited_by_count": 5,
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}