Method and apparatus for dual amplitude dual time-of-flight ultrasonic imaging

• US 5,750,895 A
• Filed: 07/03/1996
• Issued: 05/12/1998
• Est. Priority Date: 07/12/1995
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Butler, David W., Chern, Engmin James
• Primary Examiner(s): Oda, Christine K.
• Application Number:
  US08/675,509
• Time in Patent Office: 678 Days
• Field of Search: 73/602, 73/610, 73/612, 73/614, 73/615, 73/620, 73/629, 73/626, 364/507, 364/508, 128/660.07, 128/660.08, 128/660.09
• US Class Current: 73/614
• CPC Class Codes: G01N 2291/2632 flat
• CPC Class Codes: G01N 29/0609 Display arrangements, e.g. colour displays indicating or recording in connection with measuring in general G01D
• CPC Class Codes: G01N 29/0645 Display representation or displayed parameters, e.g. A-, B- or C-Scan
• 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 29/11 by measuring attenuation of acoustic waves
• CPC Class Codes: G01N 29/348 with frequency characteristics, e.g. single frequency signals, chirp signals measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00
• CPC Class Codes: G01N 29/38 by time filtering, e.g. using time gates
• CPC Class Codes: G01N 29/40 by amplitude filtering, e.g. by applying a threshold or by gain control
• CPC Class Codes: G01S 15/8938 using transducers mounted for mechanical movement in two dimensions
• CPC Class Codes: G01S 7/52061 Plan position indication (PPI display); C-scan display

Abstract

A method and apparatus for ultrasonic imaging which includes scanning a test specimen located in a test fixture in a predetermined scan pattern. Propagating and receiving reflected pulses of ultrasonic energy from an ultrasonic transducer directed to a surface of the test specimen. Detecting and generating data of both the amplitude and the depth of a defect in the test specimen from the pulses received from the test specimen. Merging the data of the amplitude and the data of the depth of the defect into composite data and then displaying the composite data in a three dimensional image whereby a mesh of both amplitude and depth data of the defect is displayed in a single image of the defect.

Claims

1. A method of ultrasonic imaging, comprising the steps of:

scanning a test specimen in a predetermined scan pattern;

propagating and receiving reflected pulses of ultrasonic energy directed to a surface of said test specimen;

detecting and generating data of both the amplitude and depth of a defect in said test specimen from the pulses received from said test specimen wherein the step of generating said data includes the step of generating a first timing gate having a start trigger for a timing unit at a front surface of said test specimen and a second timing gate having a stop trigger within a body of said test specimen;

merging said data of said amplitude and said data of said depth of said defect into composite data; and

displaying said composite data in three dimensional image whereby a mesh of both amplitude and depth data of said defect is displayed in a single image of said defect.

2. The method of claim 1 wherein the step of scanning comprises scanning the surface of said test specimen in two dimensions.

3. The method of claim 1 wherein said step of scanning comprises linear scanning in mutual orthogonal directions.

4. The method of claim 1 wherein said step of scanning comprises scanning said test specimen in a C-scan mode of operation.

5. The method of claim 4 wherein said step of generating data includes the additional step of acquiring the interval between the moment of emission of said pulses of ultrasonic energy and the return of said pulses from said surface of said test specimen.

6. The method of claim 4 wherein said step of generating data includes the additional step of separately acquiring the amplitude of said pulses from said surface of said test specimen.

7. The method of claim 1 wherein the data of the depth is generated by measuring the time interval between the start trigger and the stop trigger.

8. The method of claim 7 and additionally including the step of determining the depth z of said defect from the expression z=(Δ

t/2)v, where Δ

t is the measured time interval between the start trigger and the stop trigger, and v is the acoustic velocity of said material of the test specimen.

9. The method of claim 8 and wherein said step of displaying comprises displaying said composite data as height of said image and said amplitude is displayed as a portion of said image having a grayscale shade signifying a certain value.

10. The method of claim 8 and wherein said step of displaying comprises displaying said composite data as the height of said image and said amplitude is displayed as a portion of said image having a color signifying a certain value.

19. The method of claim 1 wherein the step of detecting and generating data of both the amplitude and depth of a defect in said test specimen includes

detecting said reflected pulses received from said test specimen in a time sequence referred to the time of emission of said pulses;

and

detecting said pulses received from said test specimen in a time sequence referred to the receipt of reflected pulses from said surface of said test specimen.

11. Apparatus for detecting and measuring defects in a test specimen, comprising:

a test fixture for said test specimen;

scanning means located on said test fixture for scanning said test specimen in a predetermined scan pattern;

ultrasonic transducer means located on said scanning means for propagating pulses of ultrasonic energy to and receiving reflected energy from said test specimen;

means for detecting the amplitude of said pulses of ultrasonic energy received back from said test specimen and generating an amplitude signal;

means for determining the depth of a defect in said test specimen from said pulses of ultrasonic energy including means for determining the time interval for an ultrasonic pulse generated by said transducer to travel from an outer surface of said test specimen to said defect and then return to said outer surface and means for generating a start signal when said ultrasonic pulse arrives at said outer surface and a stop signal at the location of said defect, and timer means responsive to said start signal and said stop signal for determining the time difference therebetween, and generating a depth signal;

means for combining said amplitude signal and said depth signal into a composite signal; and

means for displaying said composite signal as a meshed image indicative of both amplitude and depth data of said defect in said test specimen.

12. The apparatus of claim 11 wherein said scan pattern comprises a linear scan pattern in two dimensions and said meshed image comprises a three dimensional image.

13. The apparatus of claim 12 wherein said linear scan pattern in two dimensions comprises a linear scan along two mutually orthogonal axes of a rectilinear three axis system.

14. The apparatus of claim 11 wherein said scanning means comprises a portion of an ultrasonic C-scan system.

15. The apparatus of claim 11 wherein said means for determining said time interval includes means for determining the depth z of said defect from the equation z=(Δ

t/2)v, where Δ

t is the round trip time of said ultrasonic pulse to travel from said outer surface to said defect and back to said outer surface and v is the acoustic velocity of ultrasonic energy in the constituent material of said test specimen.

16. The apparatus of claim 11, and wherein said means for detecting said amplitude of said pulses include a peak detector for determining said amplitude of said defect.

17. The apparatus of claim 16 and wherein said means for displaying includes means for displaying depth as the height of said meshed image and said amplitude is displayed as a portion of said image having a grayscale shade signifying a certain value.

18. The apparatus of claim 16 and wherein said means for displaying includes means for displaying depth as the height of said meshed image and said amplitude is displayed as a portion of said image having a color of a plurality of colors signifying a certain value.