Method of conducting probe coupling calibration in a guided-wave inspection instrument

Patent metadata

Field	Value
Publication number	US-9523660-B2
Application number	US-201514674988-A
Country	US
Kind code	B2
Filing date	Mar 31, 2015
Priority date	Mar 31, 2015
Publication date	Dec 20, 2016
Grant date	Dec 20, 2016

Abstract

The method for calibrating an inspection instrument coupled with acoustic transducers disposed at circumferential positions distributed around a surface of an elongated object to inspect generally has the steps of: for each one of the circumferential positions, measuring a first and a second received signal using two acoustic transducers disposed at two axial positions along the object, the received signals resulting from the propagation of an acoustic guided wave signal along the object; identifying an acoustic mode according to the first received and the second received signals using a known period of time associated with the propagation of the acoustic guided wave signal between the two axial positions along the object; and determining a coupling coefficient associated with the acoustic mode, the coupling coefficient being indicative of the coupling of the acoustic transducers on the object; and calibrating the inspection instrument coupled to the object based on the coupling coefficients.

First claim

What is claimed is:

1. A method for calibrating an inspection instrument coupled with a plurality of acoustic transducers disposed at a plurality of circumferential positions distributed on a test surface of an elongated test object to be inspected, each of the acoustic transducers is acoustically coupled with the test surface during operation, the method comprising the steps of:
for each one or one group of the plurality of circumferential positions,
measuring at least a first and a second received signal using at least two or two groups of acoustic transducers disposed at two distinct axial positions along the elongated test object, the received signals resulting from the propagation of an acoustic guided wave signal along the elongated test object;
identifying an acoustic mode according to the first received and the second received signals using a known period of time associated with the propagation of the acoustic guided wave signal between the two axial positions along the elongated test object; and
determining a coupling coefficient associated with the acoustic mode, the coupling coefficient being indicative of the relative coupling condition between at least one of the at least two or two groups acoustic transducers and the elongated test object; and,

calibrating the inspection instrument for the at least one of the at least two or two groups of acoustic transducers based on the plurality of coupling coefficients.

2. The method of claim 1 , wherein the identified acoustic mode is a T(0,1) mode and has an amplitude uniform across the circumference of the test surface of the elongated test object.

3. The method of claim 1 , wherein said calibrating includes modifying driving voltages associated with each one of the plurality of transducers based on the determined calibration coefficients.

4. The method of claim 1 , wherein said calibrating includes modifying reception gains associated with each one of the plurality of transducers based on the determined calibration coefficients.

5. The method of claim 1 , wherein the first and the second received signal are measured at a plurality of central frequencies and across a corresponding plurality of bandwidths, wherein said obtaining, said identifying, said determining and said calibrating are performed for each one of the plurality of bandwidths.

6. The method of claim 1 , wherein the coupling coefficient associated with a circumferential position is an average of the coupling coefficients determined using each one of the at least two transducers at the circumferential position.

7. The method of claim 1 , wherein said identifying includes correlating the first acoustic signal data to the second acoustic signal data, wherein said identifying is based on the known period of time.

8. The method of claim 1 , wherein said identifying includes shifting one of the first and the second acoustic signal data by the known period of time and summating the shifted acoustic signal data to the other one of the first and the second acoustic signal data, wherein said identifying is based on a maximum of said summating.

9. The method of claim 1 , wherein said measuring includes transmitting an acoustic signal along the elongated test object using the plurality of transducers and wherein the first and the second received acoustic signals are reflected acoustic signals resulting from the reflection of the transmitted acoustic signal propagating along the elongated test object.

10. The method of claim 9 , wherein said transmitting is performed using the plurality of transducers at both the two axial positions such that the transmitted acoustic signal is directed to only one direction along the elongated test object.

11. A coupling calibrator for calibrating an inspection instrument coupled with a plurality of acoustic transducers disposed at a plurality of circumferential positions distributed on a test surface of an elongated test object to be inspected, each of the acoustic transducers is acoustically coupled with the test surface during operation, the coupling calibrator comprising:
a mode identifier configured to, for each one or one group of the plurality of circumferential positions,
obtain at least a first and a second received signal being measured using at least two or two groups of acoustic transducers disposed at two distinct axial positions along the elongated test object, the received signals resulting from the propagation of an acoustic guided wave signal along the elongated test object; and
identify an acoustic mode according to the first received and the second received signals using a known period of time associated with the propagation of the acoustic guided wave signal between the two axial positions along the elongated test object;
a coupling calculator configured to determine a coupling coefficient associated with the acoustic mode for each one of the one or the one group of the plurality of circumferential positions, each of the coupling coefficients being indicative of the relative coupling condition between at least one of the two or the two groups of acoustic transducers and the elongated test object; and

a coupling compensator configured to calibrate the inspection instrument for the at least one of the two or the two groups of acoustic transducers based on the plurality of coupling coefficients.

12. The coupling calibrator of claim 11 , wherein the identified acoustic mode is a T(0,1) mode and has an amplitude uniform across the circumference of the circular test surface of the elongated test object.

13. The coupling calibrator of claim 11 , wherein the coupling compensator is configured to modify driving voltages associated with each one of the plurality of transducers based on the determined calibration coefficients.

14. The coupling calibrator of claim 11 , wherein the coupling compensator is configured to modify reception gains associated with each one of the plurality of transducers based on the determined calibration coefficients.

15. The coupling calibrator of claim 11 , wherein mode identifier is configured to identify the acoustic mode at a plurality of central frequencies and across a corresponding plurality of bandwidths, wherein the coupling calculator determines calibration coefficients for each one of the plurality of bandwidths.

16. The coupling calibrator of claim 11 , wherein the coupling calculator is configured to average the coupling coefficients associated with a circumferential position.

17. The coupling calibrator of claim 11 , wherein the mode identifier is configured to correlate the first acoustic signal data to the second acoustic signal data, and wherein said identifying is based on the known period of time.

18. The coupling calibrator of claim 11 , wherein the mode identifier is configured to shift one of the first and the second acoustic signal data by the known period of time and to sum the shifted acoustic signal data to the other one of the first and the second acoustic signal data, and wherein said identifying is based on a maximum of said summation.

19. A guided wave inspection instrument for inspecting an elongated test object, the guided wave inspection instrument comprising:
a probe assembly coupled with a plurality of acoustic transducers to be disposed at a plurality of circumferential positions distributed on a test surface of the elongated test object to be inspected, each of the acoustic transducers is acoustically coupled with the test surface during operation;
an acquisition unit for receiving at least a first and a second received signal u

Assignees

• Lepage Benoit
• Painchaud-April Guillaume
• Olympus Scient Solutions Americas Inc

Inventors

• Lepage Benoit
• Painchaud-April Guillaume

Classifications

• G01N29/07

  by measuring propagation velocity or propagation time of acoustic waves · CPC title

• G01N29/30 Primary

  Arrangements for calibrating or comparing, e.g. with standard objects · CPC title

• G01N29/28

  providing acoustic coupling {, e.g. water (impedance matching G10K11/02)} · CPC title

• G01N2291/262

  Linear objects · CPC title

• G01N2291/0425

  Parallel to the surface, e.g. creep waves · CPC title