Alternating Current Field Measurement Technique
Level I
1. What is the medium between an alternating current field measurement technique (ACFM) probe and a metal surface when operating in air?
a. An electric current.
b. Air.
c. Magnetic field.
d. Couplant.
2. For which of the following inspection requirements could you NOT normally use ACFM for defect detection?
a. Fatigue cracks in welded joints of high strength steel.
b. Subsurface cracks in welded joints of mild steel.
c. Inspection for cracks in a weld of high strength steel under paint coating.
d. Surface fatigue in mild steel welds.
3. A fatigue crack perpendicular to the induced current will cause the induced current to:
a. disperse from the central area of the crack and concentrate around the ends.
b. disperse from the ends of the crack and concentrate in the central area.
c. stop flowing in the part.
d. increase in velocity.
Level-ll
1. During an ACFM weld inspection, the measurement of crack depth is NOT dependent on:
a. the frequency of the inspection.
b. the length of the crack.
c. the depth of penetration of the alternating current field.
d. contact with the part.
2. What effect would you expect if the coils in an ACFM probe were smaller and closer together?
a. No effect.
b. lmproved detection of smaller defects.
c. Improved sizing on larger defects.
d. Improved signal-to-noise ratio.
3. The Bx magnetic field can best be described as:
a. parallel to the plate surface and perpendicular to the current flow.
b. perpendicular to the weld.
c. parallel to the plate surface and parallel to the current flow.
d. perpendicular to the plate surface and parallel to the current flow.
