Nondestructive inspection using continuous ultrasonic wave generation

Patent metadata

Field	Value
Publication number	US-10444202-B2
Application number	US-201514688854-A
Country	US
Kind code	B2
Filing date	Apr 16, 2015
Priority date	Apr 16, 2014
Publication date	Oct 15, 2019
Grant date	Oct 15, 2019

Abstract

Methods and apparatus are disclosed for analyzing structures by applying a continuous ultrasonic excitation and measuring steady state response of the structures using laser Doppler vibrometery, or other techniques. In one example, a method comprises applying a continuous signal having one or more periodic tones to the structure, generating measurements of wave response to the signal at each of a plurality of inspection points of the structure, and, for each of the periodic tones, estimating wavenumbers for a number of the inspection points of the structure based on the wave response measurements and the frequency of the periodic tones. The estimated wavenumbers can be used to determine properties of the structure, including defects, damage, or variation in thickness.

First claim

We claim:

1. A method for analyzing a structure, the method comprising:
applying a continuous signal having one or more periodic tones to the structure, causing the structure to reach a steady vibration state;
generating measurements of wave response of the structure to the signal at each of a plurality of inspection points of the structure; and
for each of the periodic tones, estimating a wavenumber for a number of the inspection points of the structure, by calculating amplitudes of spatial frequency domain data based on the wave response measurements.

2. The method of claim 1 , wherein the continuous signal is applied by using a piezoelectric transducer in physical communication with the structure.

3. A method, comprising:
projecting a laser light onto a surface of a structure, causing the structure to reach a steady vibration state;
generating measurements of wave response of the structure to the laser light at each of a plurality of inspection points of the structure; and
estimating a wavenumber for a number of the inspection points of the structure, by calculating amplitudes of spatial frequency domain data based on the wave response measurements.

4. The method of claim 1 , wherein the periodic tones have frequencies in a range of 30-500 kHz.

5. A method for analyzing a structure, the method comprising:
applying a continuous signal having one or more periodic tones to the structure, causing the structure to reach a steady vibration state;
using a laser Doppler vibrometer, generating measurements of wave response of the structure to the signal at each of a plurality of inspection points of the structure; and
for each of the periodic tones, estimating a wavenumber for a number of the inspection points of the structure, by calculating amplitudes of spatial frequency domain data based on the wave response measurements.

6. The method of claim 1 , wherein the method further comprises identifying a defect in the structure, and wherein the structure comprises a planar metallic or composite material.

7. The method of claim 1 , wherein the method further comprises composing the wavenumber into a map of properties of the structure, and wherein the mapped properties include at least one or more of the following: thickness, density, material composition, elasticity, or temperature.

8. The method of claim 1 , wherein the wave response measurements are time domain data, and wherein the estimating the wavenumber comprises transforming at least a portion of the wave response measurements into spatial frequency domain data.

9. The method of claim 1 , further comprising generating an image or map of at least a portion of the inspection points.

10. The method of claim 1 , further comprising:
determining one or more properties of the structure based on the estimated wavenumber; and
separating foreground inspection targets from background objects using a mask formed by thresholding vibration responses based on the determined properties.

11. At least one non-transitory computer-readable storage medium storing computer-readable instructions that when executed by a computer, cause the computer to perform the method of claim 1 .

12. The method of claim 3 , wherein the method further comprises identifying a defect in the structure, and wherein the structure comprises a planar metallic or composite material.

13. The method of claim 3 , wherein the method further comprises composing the wavenumber into a map of properties of the structure, and wherein the mapped properties include at least one or more of the following: thickness, density, material composition, elasticity, or temperature.

14. The method of claim 3 , wherein the wave response measurements are time domain data, and wherein the estimating the wavenumber comprises transforming at least a portion of the wave response measurements into spatial frequency domain data.

15. The method of claim 3 , further comprising generating an image or map of at least a portion of the inspection points.

16. The method of claim 3 , further comprising:
determining one or more properties of the structure based on the estimated wavenumber; and
separating foreground inspection targets from background objects using a mask formed by thresholding vibration responses based on the determined properties.

17. At least one non-transitory computer-readable storage medium storing computer-readable instructions that when executed by a computer, cause the computer to perform the method of claim 3 .

18. The method of claim 5 , wherein the periodic tones have frequencies in a range of 30-500 kHz.

19. The method of claim 5 , wherein the method further comprises identifying a defect in the structure, and wherein the structure comprises a planar metallic or composite material.

20. The method of claim 5 , wherein the method further comprises composing the wavenumber into a map of properties of the structure, and wherein the mapped properties include at least one or more of the following: thickness, density, material composition, elasticity, or temperature.

21. The method of claim 5 , wherein the wave response measurements are time domain data, and wherein the estimating the wavenumber comprises transforming at least a portion of the wave response measurements into spatial frequency domain data.

22. The method of claim 5 , further comprising generating an image or map of at least a portion of the inspection points.

23. The method of claim 5 , further comprising:
determining one or more properties of the structure based on the estimated wavenumber; and
separating foreground inspection targets from background objects using a mask formed by thresholding vibration responses based on the determined properties.

24. At least one non-transitory computer-readable storage medium storing computer-readable instructions that when executed by a computer, cause the computer to perform the method of claim 5 .

Assignees

• Los Alamos Nat Security Llc
• Triad Nat Security Llc

Inventors

• Flynn Eric B
• Farrar Charles R
• Jarmer Gregory James Sylvester

Classifications

• G01N2291/02881

  Temperature · CPC title

• G01N29/2418

  using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics (photoacoustic cells G01N21/1702; measuring characteristics of vibrations by using radiation-sensitive means G01H9/00; acousto-optical conversion techniques for short-range imaging G01S15/8965; sound-producing devices using laser bundle G10K15/046) · CPC title

• G01N29/2437

  Piezoelectric probes · CPC title

• G01N2291/02827

  Elastic parameters, strength or force · CPC title

• G01N2291/02854

  Length, thickness · CPC title