Flaw detector incorporating DGS

• US 5,511,425 A
• Filed: 12/09/1993
• Issued: 04/30/1996
• Est. Priority Date: 12/09/1993
• Status: Expired due to Term

• Current Assignee: GE Inspection Technologies LP (General Electric Company)
• Original Assignee: Krautkramer-Branson Incorporated
• Inventors: Weiner, Alan D., Cuffe, John M., Feydo, Mark H., Ballenger, Theodore L., Kleinert, Wolf-Dietrich
• Primary Examiner(s): Chilcot, Richard
• Assistant Examiner(s): Noori, Max H.
• Application Number:
  US08/164,210
• Time in Patent Office: 873 Days
• Field of Search: 73/598, 73/600, 73/627, 73/602, 73/631, 73/609
• US Class Current: 73/627
• CPC Class Codes: G01N 2291/02854 Length, thickness
• 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 29/30 Arrangements for calibrating or comparing, e.g. with standard objects
• CPC Class Codes: G01N 29/40 by amplitude filtering, e.g. by applying a threshold or by gain control
• CPC Class Codes: G01N 29/4463 Signal correction, e.g. distance amplitude correction [DAC], distance gain size [DGS], noise filtering
• CPC Class Codes: G01N 29/50 using auto-correlation techniques or cross-correlation techniques

Abstract

Apparatus (10) for performing ultrasonic flaw testing of a material (M) or assembly. A pulser (28) generates an electrical pulse having defined characteristics. A transducer (12) converts the signal to an ultrasonic pulse, propagates the pulse through the material or assembly, receives an echo the characteristics of which include reflections off flaws or discontinuities in the material or assembly, and converts the echo into an electrical reply signal. The transducer is selectable from among a number of transducers. A processor (32) processes the reply signal to produce a visual display representing the amplitude of the reply signal for a range of propagation times (distances) into the material. A visual display (16) displays the processed electrical signal. A correlation module (42) generates a gate signal which is visually displayed (at 38) with the processed electrical signal. The gate signal corresponds to a maximum amplitude value which represents the maximum flaw size allowable for the test. If the displayed amplitude of the processed electrical signal exceeds the maximum amplitude value, the material or assembly fails the test. The correlation module emulates a series of DGS curves for the transducer used during the test. This is done to take into account test parameters related to the transducer and the material, so after an initial calibration of the apparatus is performed using a selected transducer and a reference reflector, valid test results are obtained with the transducer regardless of the distance of the reflector.

Claims

1. A method of performing ultrasonic flaw testing of a material with ultrasonic flaw test apparatus comprising:

generating an electrical pulse having defined pulse characteristics and supplying said electrical pulse to a transducer means said transducer means being selectable from among a plurality of transducer means;

converting the electrical signal to an ultrasonic pulse by the transducer means;

propagating the ultrasonic pulse through the material or assembly, the pulse producing echoes when it encounters flaws or discontinuities in the material as it propagates therethrough;

receiving the echoes back at said transducer means;

converting the received echoes by said transducer means back into a reply electrical signal;

processing the reply electrical signal into a visual display signal representing the amplitude of the echoes for a range of propagation times (distances) of the ultrasonic pulse into the material;

visually displaying the processed electrical signal; and

,

generating a gate signal which is visually displayed with the processed electrical signal, the displayed gate signal corresponding to a maximum amplitude value which represents the maximum flaw size allowable for the test, whereby if the displayed amplitude of the processed electrical signal exceeds the maximum amplitude value the material fails the test, generating the gate signal including emulating a series of DGS curves for the transducer means used during the test to take into account test parameters related to the transducer means and the material so that after an initial calibration is performed using a selected transducer means and a selected reference reflector prior to a test, valid test results are obtained with the transducer means regardless of the distance of the subsequent reflections, generating said gate signal including storing a series of DGS curves for each transducer means which may be selected, the DGS curves providing a gain factor by which the gate signal is uniform throughout for the entire range of propagation times, each series of DGS curves including information relating both to the near range operation of the transducer means and a gain value required to bring the amplitude of a processed reply electrical signal to a predetermined amplitude value, and storing the DGS curves includes creating a DGS table for each type of transducer means used with the apparatus, the table including a series of entries relating to near field distance, amplitude, and the delay velocity associated with the transducer, the type of crystal used in the selected transducer means to convert electrical signals to ultrasonic pulses and vice versa, and the diameter and operating frequency of the crystal whereby the relationship between the displayed amplitude of the processed electrical signal and the gate signal is readily determined so the user can readily ascertain if a flaw test is passed or failed by the material.

2. The method of claim 1 further including selecting a particular transducer means by the person performing the test with the person entering into the apparatus information identifying the particular transducer means selected, and selecting from among the stored DGS curves those relating to the selected transducer means.

3. The method of claim 2 wherein storing the DGS curves for a transducer means includes digitizing the contents of the table and storing the resulting digital values in the apparatus.

4. The method of claim 3 wherein the method further includes incorporating in the table the type of reference reflector used in a calibration, and the diameter of a reference echo which is produced when the selected transducer means is used with a selected reference reflector.

5. The method of claim 4 wherein the method further includes incorporating in the table sound attenuation values for the selected reference reflector and the material under test, amplitude correction values for the selected reference reflector, and transfer loss values relating to the difference in coupling conditions between the selected reference reflector and the material under test.

6. The method of claim 5 wherein the method further includes incorporating in the table an equivalent reflector size which defines the shape of a disk shaped reflector for a DGS curve.

7. In a method of performing ultrasonic flaw testing of a material with ultrasonic flaw test apparatus in which an electrical pulse having defined pulse characteristics is generated and supplied to a transducer means, converted to an ultrasonic pulse which is propagated through the material to produce echoes when is encounters flaws or discontinuities in the material, the echoes being received back at said transducer means and converted into a reply electrical signal which is processed to produce a visual display signal representing the amplitude of the echoes for a range of propagation times (distances) of the ultrasonic pulse into the material, the processed electrical signal being visually displayed, the improvement comprising:

generating a gate signal which is visually displayed with the processed electrical signal, the displayed gate signal corresponding to a maximum amplitude value which represents the maximum flaw size allowable for the test, whereby if the displayed amplitude of the processed electrical signal exceeds the maximum amplitude value the material fails the test, generating the gate signal including storing a series of DGS curves for the transducer means used during the test to take into account test parameters related to the transducer means and the material,

defining each DGS curve as a function of the sound propagation qualities of the material under test, the diameter and operating frequency of a crystal used in the transducer means, the type of selected reflector used for the calibration and the diameter of the reflected echo produced by the selected transducer means, the sound attenuation of the selected reference reflector and the material under test, an amplitude correction value which is used if the selected reference reflector is arcuate as opposed to a flat wall surface type of reflector, a compensation value to compensate for transfer loss differences between the selected reference reflector and the material under test, and an equivalent reflector size value defining a diameter of a disk shaped reflector used for generating DGS curves so that after an initial calibration is performed using a selected transducer means and a selected reference reflector prior to a test, valid test results are obtained with the transducer means regardless of the size of the reflections produced during a test.

8. The method of claim 7 wherein generating the DGS curves includes creating a DGS table for each type of transducer means, and storing the tables.

9. The method of claim 8 wherein storing the DGS curves for a transducer means includes digitizing the contents of the table and storing the resulting digital values.

10. Apparatus for performing ultrasonic flaw testing of a material comprising:

means for generating an electrical pulse having defined pulse characteristics;

a transducer probe for convening the electrical signal to an ultrasonic pulse which propagates through the material, receives an echo whose characteristics are a function of flaws or discontinuities in the material, and for converting the received echo into an electrical reply signal, said probe being selectable from among a plurality of probes;

processing means for processing the electrical reply signal into a visual display signal representing the amplitude of the echo for a range of propagation times (distances) into the material;

means for visually displaying the processed electrical signal; and

,

correlation means for generaling a gate signal which is visually displayed with the processed electrical signal, the displayed gate signal corresponding to a maximum amplitude value which represents the maximum flaw size allowable for the test, whereby if the displayed amplitude of the processed electrical signal exceeds the maximum amplitude value the material fails the test, the correlation means including means for emulating a series of DGS curves for the probe used during the test to take into account test parameters related to the probe and the material so that after an initial calibration of the apparatus is performed using a selected probe and a reference reflector, valid test results are obtained with the probe means regardless of the size of the reflector used in the test, said correlation means including means for storing a digitized table of parameters from which DGS curves are formed, said parameters included in the table including the sound propagation qualities of the material under test, the diameter and operating frequency of a crystal used in the transducer means, the type of selected reflector used for the calibration and the diameter of the reflected echo produced by the selected transducer, the sound attenuation of the selected reference reflector and the material under test, an amplitude correction value which is used if the selected reference reflector is arcuate as opposed to a flat wall surface type of reflector, a compensation value to compensate for transfer loss differences between the selected reference reflector and the material under test, and an equivalent reflector size value defining a diameter of a disk shaped reflector used for generating DGS curves.

11. The apparatus of claim 10 further including interface means by which the user of the apparatus can program the correlation means as to which probe and reflector and used during calibration.