Method of determining acoustic transit times for material having high acoustic attenuation properties

• US 8,276,431 B1
• Filed: 08/08/2008
• Issued: 10/02/2012
• Est. Priority Date: 08/08/2008
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Latimer, Paul J., Birks, Albert S.
• Primary Examiner(s): Williams, Hezron E
• Assistant Examiner(s): MILLER, ROSE MARY
• Application Number:
  US12/228,320
• Time in Patent Office: 1,516 Days
• Field of Search: 73/18.2, 73/18.6, 735/97, 735/98, 736/02
• US Class Current: 73/1.86
• CPC Class Codes: G01N 2291/0421 Longitudinal waves
• CPC Class Codes: G01N 2291/0422 Shear waves, transverse waves, horizontally polarised waves
• CPC Class Codes: G01N 29/07 by measuring propagation velocity or propagation time of acoustic waves
• CPC Class Codes: G01N 29/30 Arrangements for calibrating or comparing, e.g. with standard objects

Abstract

A method for determining time a single transit of an acoustic wave through a test material using a calibration material having known acoustic velocity characteristics and an acoustic pitch-catch system with a signal recorder for recording a received signal as a function of time. The system includes a first configuration for transmission of acoustic shear waves and a second configuration for transmission of acoustic longitudinal waves. In the first configuration, a first acoustic zero is determined when the acoustic shear waves are applied to the calibration material. In its second configuration, a second acoustic zero is determined when the acoustic longitudinal waves are applied to the calibration material. Each configuration is coupled to a test material with the respective first and second acoustic zeroes identified on the recorder. The signal recorder determines a single transit time for the acoustic waves through the test material.

Claims

1. A method of determining the time for a single transit of an acoustic wave through a test material, comprising:

providing a calibration material having known acoustic velocity characteristics, said calibration material having a plurality of sections with each of said sections defining a known thickness;

providing an acoustic pitch-catch system that includes a recording structure for recording a received signal as a function of time, said pitch-catch system having a first configuration for the transmission of acoustic shear waves and a second configuration for the transmission of acoustic longitudinal waves;

determining a first acoustic zero for said pitch-catch system in said first configuration when said acoustic shear waves are applied at normal incidence by said pitch-catch system to each of said sections of said block;

determining a second acoustic zero for said pitch-catch system in said second configuration when said acoustic longitudinal waves are applied at normal incidence by said pitch-catch system to each of said sections of said calibration material;

providing a test material of known thickness;

coupling said pitch-catch system in said first configuration to the test material such that said acoustic shear waves can be applied at normal incidence to the test material;

identifying said first acoustic zero on said recording structure;

determining a single transit time for said acoustic shear waves to transit the test material using said pitch-catch system in said first configuration with said first acoustic zero so-identified;

coupling said pitch-catch system in said second configuration to the test material such that said acoustic longitudinal waves can be applied at normal incidence to the test material;

identifying said second acoustic zero on said recording structure; and

determining a single transit time for said acoustic longitudinal waves to transit the test material using said pitch-catch system in said second configuration with said second acoustic zero so-identified.

2. The method according to claim 1, wherein said calibration material is a block of calibration material, and wherein said calibration material is comprised of an isotropic material.

3. The method according to claim 1, wherein said calibration material is a block of calibration material selected from the group consisting of aluminum and steel.

4. The method according to claim 1, wherein said calibration material is a stepped block of calibration material, and wherein each of said sections is defined by a step in said stepped block.

5. The method according to claim 1, wherein said recording structure comprises a digital oscilloscope.

6. The method according to claim 5, wherein said identifying said first acoustic zero comprises fixing a cursor of said digital oscilloscope at said first acoustic zero.

7. The method according to claim 5, wherein said identifying said second acoustic zero comprises fixing a cursor of said digital oscilloscope at said second acoustic zero.

8. A method of determining the time for a single transit of an acoustic wave through a test material, comprising:

providing a stepped block of an isotropic material, said stepped block having a plurality of stepped sections with each of said stepped sections defining a known thickness;

providing an acoustic pitch-catch system that includes recording structure for recording a received signal as a function of time, said pitch-catch system having a first configuration for the transmission of acoustic shear waves and a second configuration for the transmission of acoustic longitudinal waves;

determining a first acoustic zero for said pitch-catch system in said first configuration when said acoustic shear waves are applied at normal incidence by said pitch-catch system to each of said stepped sections of said stepped block;

determining a second acoustic zero for said pitch-catch system in said second configuration when said acoustic longitudinal waves are applied at normal incidence by said pitch-catch system to each of said stepped sections of said stepped block;

providing a test material of known thickness;

coupling said pitch-catch system in said first configuration to the test material such that said acoustic shear waves can be applied at normal incidence to the test material;

identifying said first acoustic zero on said recording structure;

determining a single transit time for said acoustic shear waves to transit the test material using said pitch-catch system in said first configuration with said first acoustic zero so-identified;

coupling said pitch-catch system in said second configuration to the test material such that said acoustic longitudinal waves can be applied at normal incidence to the test material;

identifying said second acoustic zero on said recording structure; and

determining a single transit time for said acoustic longitudinal waves to transit the test material using said pitch-catch system in said second configuration with said second acoustic zero so-identified.

9. The method according to claim 8, wherein said isotropic material is selected from the group consisting of aluminum and steel.

10. The method according to claim 8, wherein said recording structure comprises a digital oscilloscope.

11. The method according to claim 10, wherein said identifying said first acoustic zero comprises fixing a cursor of said digital oscilloscope at said first acoustic zero.

12. The method according to claim 10, wherein said identifying said second acoustic zero comprises fixing a cursor of said digital oscilloscope at said second acoustic zero.

13. A method of determining the time for a single transit of an acoustic wave through a test material, comprising:

providing a block of a calibration material having known acoustic velocity characteristics, said block having a plurality of sections with each of said sections defining a known thickness;

providing an acoustic pitch-catch system that includes a digital oscilloscope for recording a received signal as a function of time, said pitch-catch system having a first configuration for the transmission of acoustic shear waves and a second configuration for the transmission of acoustic longitudinal waves;

determining a first acoustic zero for said pitch-catch system in said first configuration when said acoustic shear waves are applied at normal incidence by said pitch-catch system to each of said sections of said block;

determining a second acoustic zero for said pitch-catch system in said second configuration when said acoustic longitudinal waves are applied at normal incidence by said pitch-catch system to each of said sections of said block;

providing a test material of known thickness;

coupling said pitch-catch system in said first configuration to the test material such that said acoustic shear waves can be applied at normal incidence to the test material;

identifying said first acoustic zero on said digital oscilloscope;

determining a single transit time for said acoustic shear waves to transit the test material using said pitch-catch system in said first configuration with said first acoustic zero so-identified;

coupling said pitch-catch system in said second configuration to the test material such that said acoustic longitudinal waves can be applied at normal incidence to the test material;

identifying said second acoustic zero on said digital oscilloscope; and

determining a single transit time for said acoustic longitudinal waves to transit the test material using said pitch-catch system in said second configuration with said second acoustic zero so-identified.

14. The method according to claim 13, wherein said block of calibration material comprises an isotropic material.

15. The method according to claim 13, wherein said block of calibration material is selected from the group consisting of aluminum and steel.

16. The method according to claim 13, wherein said block of calibration material is a stepped block, and wherein each of said sections is defined by a step in said stepped block.