GB1472472A - Methods of ultrasonic testing - Google Patents

Abstract

1472472 Ultrasonic flaw detection KRAUTKRAMER GmbH 29 April 1974 [28 April 1973] 18664/74 Heading G1G An ultrasonic pulse-echo detection flaw detection apparatus comprises a plurality of sequentially energized test probes, and, in operation, determines transit time values representative of individual coupling distances of the test probes with respect to a datum at a given time point which values are stored, and recalled during subsequent sequential operation of the test probes. The test probes are initially caused to operate on a calibration block to produce transit time values which represent the distance 52, Fig. 1 from which the known propagation transit time representing the distance 51 is subtracted to yield the value of the coupling distance sn. During a subsequent flaw detection sequence on test piece 21, the coupling distance sn, so measured, is used define a period 2sn, Fig. 3, after the time of occurrence of transmitted pulse 23, during which surface entry echoes will occur before the period 2D during which echoes from any inhomogeneities will be detected. The bottom echo 24 from the test piece rear face, if detected during a further detection zone S4, provides monitoring information that correct coupling has been achieved, zone S4 occurring after a safety margin period S3. Fig. 4 (not shown) shows a block diagram of the apparatus according to the invention, which includes a display screen which provides an image similar to Figs. 1 and 3, and on which are displayed, in operation, the echo signal from each of the sequentially energized test probes 20. The echo signals are also monitored by control circuitry which automatically, at a first command switch setting, measures the n coupling distances, which values are stored, and used during test. The acoustic coupling, detection zone, safety margin and detection, or not, of the back echo, are automatically monitored, and indications are given as to whether the flaw detection measurement which provides an indication of any detected flaws is reliable.