ACS Non-Destructive Testing (NDT) Methods 2

Question 1

What is the primary principle behind eddy current testing?

Accepted Answer

Alternating magnetic fields induce eddy currents in conductive materials, and changes in those currents indicate defects

Answer

Eddy current testing works by inducing eddy currents in electrically conductive materials via alternating magnetic fields; discontinuities or material variations alter the eddy current flow, changing the coil impedance that is measured.

Question 2

What is a couplant used for in contact ultrasonic testing?

Accepted Answer

To eliminate the air gap between the transducer and the test surface, enabling sound transmission

Answer

A couplant (such as water, oil, or gel) fills the air gap between the transducer and test surface because ultrasonic sound waves cannot effectively transmit through air.

Question 3

On an A-scan ultrasonic display, what do the peaks (echoes) represent?

Accepted Answer

Reflections of sound energy from surfaces, boundaries, or discontinuities within the material

Answer

On an A-scan display, peaks represent reflected ultrasonic echoes from surfaces or internal discontinuities; the horizontal axis shows time (depth) and the vertical axis shows signal amplitude.

Question 4

Which eddy current probe orientation is most effective for detecting cracks perpendicular to the surface on a flat plate?

Accepted Answer

Surface (pancake) probe

Answer

A surface (pancake) probe placed flat against the test surface is most effective for detecting surface cracks in flat materials because its coil orientation maximizes sensitivity to surface discontinuities.

Question 5

What effect does increasing the frequency of an ultrasonic transducer have on inspection capability?

Accepted Answer

Increases sensitivity to small defects but reduces penetration depth

Answer

Higher ultrasonic frequencies produce shorter wavelengths, improving resolution and sensitivity to small defects, but are attenuated more rapidly, reducing penetration depth in the material.

(ACS) Airman Certification Standard Certified Mechanic Practice Test

(ACS) Airman Certification Standard Certified Mechanic Practice Test

ACS Non-Destructive Testing (NDT) Methods 2