Flaw detector incorporating DGS

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.

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.