UT 6dB Drop Defect Thru Wall Sizing

This video demonstrates how to measure the through wall dimension of a center line crack in a weld using an ultrasonic tester. This technique uses the 6dB drop method to size the vertical through wall of a crack. The defect signal is maximized and the transducer is moved in and out to walk the signal up and down until the signal drops by 50% FSH or 6dB. This will detect the crack tips.
Equipment: Olympus EPOCH 1000i UT tester, GE 5MHZ, 0.25" diameter transducer with a 60 degree screw on wedge.

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