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

High-frequency sound waves are transmitted through the material

Answer

Ionizing radiation passes through the material to expose a film

Answer

Fluorescent dye penetrates surface cracks and is revealed under UV light

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

To magnetize the test piece

Answer

To develop the penetrant indication

Answer

To enhance fluorescent visibility under UV light

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

Magnetic field intensity at various depths

Answer

Electrical impedance changes caused by eddy currents

Answer

Radiation intensity measured by the detector

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

Encircling probe

Answer

Bobbin probe

Answer

Reflection probe

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

Increases penetration depth but reduces sensitivity to small defects

Answer

Has no effect on penetration or sensitivity

Answer

Increases both penetration depth and sensitivity equally

Question 6

What type of material condition can eddy current testing detect that magnetic particle inspection cannot?

Accepted Answer

Surface cracks in non-ferromagnetic alloys such as aluminum and titanium

Answer

Subsurface cracks in ferromagnetic steel

Answer

Porosity in welds

Answer

Delaminations in composites

Question 7

In ultrasonic testing, what is 'back-wall echo loss' an indication of?

Accepted Answer

A large internal discontinuity or severe attenuation blocking the return of the back-wall reflection

Answer

Insufficient couplant application

Answer

Calibration error in the time base

Answer

Surface roughness causing signal scatter at the entry point only