SYSTEM AND METHOD FOR TESTING A STRUCTURE USING LASER ULTRASOUND

• US 20190331757A1
• Filed: 04/30/2018
• Published: 10/31/2019
• Est. Priority Date: 04/30/2018
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Motzer, William P., Georgeson, Gary E., Bingham, Jill P., Kennedy, James C., Garvey, Jeffry J.
• Granted Patent: US 11,287,507 B2
• Time in Patent Office: Days
• CPC Class Codes: G01N 29/2418 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 Class Codes: G01N 29/265 by moving the sensor relative to a stationary material
• CPC Class Codes: G01N 29/34 Generating the ultrasonic, sonic or infrasonic waves , e.g. electronic circuits specially adapted therefor
• CPC Class Codes: G01N 29/4445 Classification of defects
• CPC Class Codes: G01S 3/801 Details G01S3/82, G01S3/84, G01S3/86 take precedence
• CPC Class Codes: G06F 30/20 Design optimisation, verification or simulation optimisation, verification or simulation of circuit designs G06F30/30
• CPC Class Codes: G06T 17/00 Three dimensional [3D] modelling, e.g. data description of 3D objects

Abstract

A method for testing a structure includes steps of: identifying a three-dimensional position of a surface of the structure relative to a reference frame; transmitting laser light from an output of a transmitter onto the surface of the structure to form ultrasonic waves in the structure and to detect a response to the ultrasonic waves; based on the three-dimensional position of the surface, moving the laser light over the structure along a scan path so that the output of the transmitter is located at a constant offset distance from the surface and that the laser light, transmitted from the output of the transmitter, is directed onto the surface at a constant angle of projection; and based on the response to the ultrasonic waves, determining whether an inconsistency is present in the structure.

Claims

1. A method for testing a structure using laser ultrasound, the method comprising:

identifying a three-dimensional position of a surface of the structure relative to a reference frame;

transmitting laser light from an output of a transmitter onto the surface of the structure to form ultrasonic waves in the structure and to detect a response to the ultrasonic waves;

based on the three-dimensional position of the surface, moving the laser light over the structure along a scan path so that the output of the transmitter is located at a constant offset distance from the surface and that the laser light, transmitted from the output of the transmitter, is directed onto the surface at a constant angle of projection; and

based on the response to the ultrasonic waves, determining whether an inconsistency is present in the structure.

2. The method of claim 1, wherein:

each one of a plurality of points on the surface has a corresponding three-dimensional position relative to the reference frame;

the three-dimensional position comprises an XYZ-coordinate in the reference frame; and

a Z-coordinate of one of the plurality of points on the surface is different than a Z-coordinate of another one of the plurality of points on the surface.

3. The method of claim 2, further comprising:

forming the laser light, transmitted from the output of the transmitter, into a pattern on the surface of the structure; and

positioning the pattern on the surface so that a difference value of Z-coordinates of any two of the plurality of points on the surface, which are located inclusively within the pattern of the laser light, is less than or equal to a threshold value.

4. The method of claim 3, wherein the threshold value is less than or equal to one-eighth of an inch.

5. The method of claim 3, wherein the pattern of the laser light is in the form of a line of the laser light.

6. The method of claim 5, further comprising:

identifying a first one of the plurality of points on the surface and a second one of the plurality of points on the surface in which a difference value of Z-coordinates in the reference frame of any two of the plurality of points on the surface, which are located inclusively along a straight line that extends between the first one of the plurality of points and the second one of the plurality of points, is less than or equal to the threshold value; and

aligning the line of the laser light with the straight line, extending between the first one of the plurality of points and the second one of the plurality of points.

7. The method of claim 6, further comprising:

identifying a third one of the plurality of points on the surface and a fourth one of the plurality of points on the surface in which a difference value of Z-coordinates in the reference frame of any two of the plurality of points on the surface, which are located inclusively along a second straight line that extends between the third one of the plurality of points and the fourth one of the plurality of points, is less than or equal to the threshold value;

selecting the scan path of the laser light between the straight line, extending between the first one of the plurality of points and the second one of the plurality of points, and the second straight line, extending between the third one of the plurality of points and the fourth one of the plurality of points;

moving the line of the laser light across the surface along the scan path; and

aligning the line of the laser light with the second straight line, extending between the third one of the plurality of points and the fourth one of the plurality of points.

8. The method of claim 7, further comprising adjusting a pose of the transmitter so that the output of the transmitter is located at the constant offset distance from the surface and that the laser light, transmitted from the output of the transmitter, is directed onto the surface at the constant angle of projection as the line of the laser light moves across the surface along the scan path between the straight line, extending between the first one of the plurality of points and the second one of the plurality of points, and the second straight line, extending between the first one of the plurality of points and the second one of the plurality of points.

9. The method of claim 7, wherein:

the structure comprises a stiffener of an aircraft;

the stiffener comprises a first axis; and

each one of the straight line, extending between the first one of the plurality of points and the second one of the plurality of points, and the second straight line, extending between the third one of the plurality of points and the fourth one of the plurality of points is oriented parallel to the first axis of the stiffener.

10. The method of claim 9, wherein the scan path of the laser light is perpendicular to the first axis of the stiffener.

11. The method of claim 9, wherein the scan path of the laser light is oblique to the first axis of the stiffener.

12. The method of claim 5, further comprising:

providing three-dimensional point cloud data of the surface of the structure;

based on the three-dimensional point cloud data of the surface, identifying the three-dimensional position of the plurality of points on the surface relative to a structure reference frame; and

aligning the structure reference frame with the reference frame.

13. The method of claim 12, further comprising:

providing a three-dimensional model of the structure; and

extracting the three-dimensional point cloud data of the surface from the three-dimensional model of the structure.

14. The method of claim 13, further comprising:

capturing an image of the structure; and

generating the three-dimensional model of the structure from the image of the structure.

15. The method of claim 13, further comprising, based on the three-dimensional model of the surface, simulating the scan path of the laser light so that a difference value of Z-coordinates of any two of the plurality of points on the surface, which are located inclusively within the line of the laser light, is less than or equal to the threshold value as the line of the laser light moves across the surface of the structure.

16. A laser ultrasound testing system comprising:

a laser source configured to emit laser light;

a transmitter optically coupled with the laser source and configured to transmit the laser light from an output of the transmitter onto a surface of a structure, wherein the laser light is configured to form ultrasonic waves in the structure and to detect a response to the ultrasonic waves;

a movement mechanism coupled to the transmitter and configured to move the transmitter relative to the structure;

a computer configured to;

identify a three-dimensional position of the surface relative to a reference frame;

control the movement mechanism so that the laser light moves over the structure along a scan path in which the output of the transmitter is located at a constant distance from the surface and the laser light, transmitted from the output of the transmitter, is directed at a constant angle of projection onto the surface based on the three-dimensional position of the surface; and

determine whether an inconsistency is present in the structure based on the response to the ultrasonic waves.

17. The laser ultrasound testing system of claim 16, wherein:

the transmitter is configured to transmit the laser light onto the surface of the structure in the form of a pattern; and

the pattern of the laser light is positioned on the surface so that a difference value of Z-coordinates of any two of a plurality of points on the surface, which are located inclusively within the pattern of the laser light, is less than or equal to a threshold value.

18. The laser ultrasound testing system of claim 17, wherein the computer is further configured to:

extract three-dimensional point cloud data of the surface from a three-dimensional model of the structure; and

based on the three-dimensional point cloud data of the surface, identify the three-dimensional position of the plurality of points on the surface relative to the reference frame.

19. The laser ultrasound testing system of claim 18, further comprising a sensor configured to capture an image of the structure, wherein the computer is further configured to generate the three-dimensional model of the structure from the image of the structure.

20. The laser ultrasound testing system of claim 18, wherein, based on the three-dimensional point cloud data of the surface, the computer is further configured to select the scan path of the laser light so that a difference value of Z-coordinates of any two of the plurality of points on the surface, which are located inclusively within the pattern of the laser light, is less than or equal to the threshold value as the pattern of the laser light moves across the surface of the structure.