Level 2 , 3 Question [Ref]
I-1 Generation of ultrasound waves with EMATs is possible in a) Electric conductive materials
b) All types of materials
c) Ferromagnetic materials
d) for a and c
I-2 EMAT applied sound waves are generated within the a) coil
b) Material
c) liftoff
I-3 What of these EMAT's advantages are wrong? a) generation of horizontally polarized shear waves
b) inexpensive
c) dry coupling
d) good for high-temperature NDE
I-4 What of these EMAT's disadvantages are wrong? [1 ] a) less fieldability equipment
b) low efficiency factor
c) not applicable on plastics
d) not applicable on inhomogeneous materials
I-5 What causes the ultrasound effect in electric conductive materials? [2 ] a) Lorenz force
b) magnetostriction?
I-6 EMATs are used at high temperatures (800°F), should the probe be cooled? [1, 8 ] a) no
b) yes
Level1 , 2 3 Question
II-1 What kind of waves EMATs can generate? a) shear waves
b) lamb waves (guided waves)
c) Rayleigh waves
d) all of the above
II-2 How much can be the liftoff to the material under test a) up to 1 mm
b) up to 10 mm
II-3 What is an important requirement of an EMAT equipment? a) low noise system
b) wide band amplifier (1 - 20 MHz)
II-4 In what distance under the materials surface the sound is generated? a) less than a wave length
b) about 10 wave length
c) some millimeters
II-5 The sound generation is high efficient in ... a) in high ferromagnetic materials
b) in high conductive materials
c) the same for the above
II-6 EMAT can better ... [3 ] a) receive ultrasonic waves
b) transmit ultrasonic waves
c) the same for both of the above
II-7 Is the efficiency factor affected by the object's material characteristics? [5 ] a) no
b) yes
Level1 , 2 , 3 Question
III-1 EMATs are applied on austenitic weld inspection by use of SH waves, what is correct? [5 ] a) the EMAT technique is enough sufficient
b) piezoelectric angle beam transducers should be used also
III-2 EMATs are applied on boiler tubes, must the oxide layer be removed? [6 ] a) yes
b) no
III-3 How much are the signal losses for a liftoff change from 0.1mm to 0.5 mm? [7 ] a) approx. 3 db
b) approx. 10 db
c) approx. 20 db
III-4 How much are permanent magnet forces typically at a liftoff of 0.2 mm? [7 ] a) approx. 50 N
b) approx. 200 N
c) approx. 500 N
III-5 Is it possible to build EMAT probes in cases comparative to PZT probes? [8 ] a) no
b) yes
III-6 What is for a non-segmented coil specific? [2 ] a) generate narrow band signals
b) distribute the same energy forward and backward.
c) generate broad band signals