mm thick protective

layer on it made of metal “A”. The two layers are fused with no air gap between

them. This specimen is hence composed of two layers of metals. An ultrasonic

instrument is calibrated for a range of 0 to 100 mm using a shear wave probe

which produces an angle of 45 degrees to the

normal to the surface in steel. The probe is used to test the plate by placing

it on protective layer and then moved to scan the plate. A crack is found in

the plate and two signals are identified on the instrument screen from the top

and bottom of the crack, at ranges of

mm and 70 mm using the maximum

amplitude technique. The probe has to be moved a distance of 12 mm between the maximized heights of these two

signals. Velocity of shear waves in steel is 3230 m/s. Velocity of shear waves

in metal “A” is 2700 m/s. Calculate the distance of the top and bottom of the

crack from the specimen surface and also the angle of the crack with respect to

the normal to the surface.