Ultrasonic non-destructive testing

• US 8,789,419 B2
• Filed: 12/12/2012
• Issued: 07/29/2014
• Est. Priority Date: 11/04/2005
• Status: Active Grant

• Current Assignee: Permasense Limited (Emerson Process Management Limited)
• Original Assignee: Imperial Innovations Limited (Imperial College London)
• Inventors: Cawley, Peter, Cegla, Frederick Bert
• Primary Examiner(s): Macchiarolo, Peter
• Assistant Examiner(s): MILLER, ROSE MARY
• Application Number:
  US13/712,492
• Publication Number:
  US 20130118260A1
• Time in Patent Office: 594 Days
• Field of Search: 736/17, 736/44, 735/96
• US Class Current: 73/617
• CPC Class Codes: G01N 2291/0234 Metals, e.g. steel
• CPC Class Codes: G01N 2291/02854 Length, thickness
• 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 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01N 29/069 Defect imaging, localisation and sizing using, e.g. time of flight diffraction [TOFD], synthetic aperture focusing technique [SAFT], Amplituden-Laufzeit-Ortskurven [ALOK] technique
• CPC Class Codes: G01N 29/2412 using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]; investigating the presence of flaws using eddy currents G01N27/90, magnetostrictive transducers B06B1/08, measuring magnetostrictive properties G01R33/18
• CPC Class Codes: G01N 29/28 providing acoustic coupling , e.g. water impedance matching G10K11/02
• CPC Class Codes: G01N 29/34 Generating the ultrasonic, sonic or infrasonic waves , e.g. electronic circuits specially adapted therefor
• CPC Class Codes: G10K 11/24 for conducting sound through solid bodies, e.g. wires

Abstract

An apparatus and method for ultrasonic non-destructive testing provides an elongate strip of ultrasound transmissive material coupled at a proximal end to an object under test. The elongate strip has a transverse cross-section with a width and thickness giving an aspect ratio greater than unity and matched to the ultrasonic transducer such that excitation induces a substantially non-dispersive ultrasonic signal to propagate along the elongate strip to the proximal end and to enter the object under test. These non-dispersive pulses are particularly suited for time-of-flight measurements, thickness measurements, crack measurements and the like. The elongate strip helps to separate the transducer from a potentially hostile environment associated with the object under test. The elongate strip also has a large area of contact with the object under test allowing efficient transmission of energy into the object under test.

Claims

1. A method of ultrasonic testing of a solid object, the method comprising:

clamping a proximal end of an elongate strip having a width and a thickness and a width to thickness aspect ratio of greater than unity to a solid object;

coupling a transducer at a distal end of the elongate strip;

exciting non-dispersive ultrasonic signals in the elongate strip with the transducer, the signals propagating along a length of the elongate strip from the distal end to the proximal end and into the solid object, said signals comprising shear wave signals which are polarized in a direction perpendicular to their propagation direction; and

receiving corresponding reflected return signals from said solid object that are non-dispersive ultrasonic shear wave signals and are polarized in a direction perpendicular to a propagation direction of the reflected return signals.

2. The method of claim 1, wherein said elongate strip is formed of a material having a shear velocity of Cs and a shear wavelength λ

_B, where λ

_B=C_s/F and F is the frequency corresponding to λ

_B, and said non-dispersive ultrasonic signals are formed of components of different frequencies and having shear wavelengths extending from λ

_short to λ

_long.

3. The method of claim 2 wherein said elongate strip has a transverse cross-section with a thickness less than 2.5 λ

_short.

4. The method of claim 2, wherein said elongate strip has a transverse cross-section with a thickness less than λ

_short.

5. The method of claim 2, wherein said elongate strip has a transverse cross-section with a width greater than 3.5 λ

_long.

6. The method of claim 2, wherein said elongate strip has a transverse cross-section with a width greater than 5 λ

_long.

7. The method of claim 1, wherein said elongate strip is formed of a material having a bar velocity C_bar and a wavelength λ

_bar, where λ

_bar=C_bar/F and F is the frequency corresponding to λ

_bar, and said non-dispersive ultrasonic signals are formed of components of different frequencies and having bar wavelengths extending from λ

_short to λ

_long.

8. The method of claim 7, wherein said thickness is less than 2.5 λ

_long.

9. The method of claim 7, wherein said thickness is less than λ

_short.

10. The method of claim 7, wherein said width is greater than 5 λ

_long.

11. The method of claim 1, wherein substantially only a single mode of propagated guided wave is excited in said elongate waveguide.

12. The method of claim 1, wherein said object under test is:

(i) at a temperature greater than 200°

C.; and

(ii) subject to above background levels of ionizing radiation.