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EN ISO 16826:2014 pdf free

EN ISO 16826:2014 pdf free.Non-destructive testing一Ultrasonic testing一Examination for discontinuities perpendicular to the surface
The examination is normally carried out using two similar 45° angle probes, one probe operating as the transmitter and the other probe as receiver. For wall thicknesses greater than approximately 1 60 mm, probes with different transducer sizes are preferred in order to ensure approximately the same beam diameters in the examination zone.
The use of probe angles other than 45° may be necessary to comply with particular geometrical conditions.Probe angles that give rise to mode conversions shall be avoided.
The probe distance, y, see Figure 1, is adjusted for each examination zone with the intersection of the beam axes in the centre of the zone. Alternatively, the width and number of the examination zones can be determined graphically using scale drawings of the calculated or measured 6 dB beam profiles.
DGS-diagrams for tandem examination may be derived from the general DGS-diagram or based on probe specific diagrams.
The diagrams are prepared as shown in Figure 3. The mean value of the gain differences V1 and V2 are derived from the specific diagrams for the probes or from the general DGS diagram. These are used to establish a distance amplitude curve (DAC) for specific tandem examinations, based on this disk-shaped reflector (DSR).
The time base of the instrument is calibrated for transverse waves using transducer, TR, of the LLT probe as a transceiver, see Figure 7a).
The probe is then used in the LLT mode (with transducer, TT, operating as transmitter, and transducer, TR, as receiver) on a reference block having the same thickness as the object to be examined and containing a number of vertical disk-shaped reflectors at different depths, see Figure 7b). The observed sound path distance along the time base for each of these reflectors should be noted in a table or a diagram against their depth from the scanning surface, see Figure 7c).
This table or diagram is then used to determine the depth, t, of a discontinuity from a measurement of its observed sound path distance, see Figure 7c) and 7d).EN ISO 16826 pdf download.

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