Composite inspection

Patent metadata

Field	Value
Publication number	US-10345267-B2
Application number	US-201615070261-A
Country	US
Kind code	B2
Filing date	Mar 15, 2016
Priority date	Dec 21, 2015
Publication date	Jul 9, 2019
Grant date	Jul 9, 2019

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.

First claim

What is claimed is:

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 interpolate

Assignees

• Boeing Co
• Univ Washington

Inventors

• O'Donnell Matthew
• Pelivanov Ivan
• Brady Steven Kenneth
• Georgeson Gary Ernest
• Kollgaard Jeffrey Reyner
• Motzer William P
• Gordon Iii Clarence Lavere
• Bingham Jill Paisley
• Stewart Alan F
• Kennedy James C

Classifications

• G01N29/343

  pulse waves, e.g. particular sequence of pulses, bursts · CPC title

• G01N21/1702 Primary

  with opto-acoustic detection, e.g. for gases or analysing solids · CPC title

• G01N2291/0231

  Composite or layered materials · CPC title

• G01N29/50

  using auto-correlation techniques or cross-correlation techniques · CPC title

• B64F5/60

  Testing or inspecting aircraft components or systems · CPC title