NDT - Non-Destructive Testing Eddy Current Testing Theory Questions and Answers

Question 1

An inspector needs to detect subsurface defects in a thick aluminum plate. According to the principles of eddy current testing, which adjustment to the test frequency would be most effective?

Accepted Answer

Decrease the frequency to increase the depth of penetration.

Answer

Increase the frequency to improve surface resolution.

Answer

Use a multi-frequency setup to cancel out lift-off effects.

Answer

Keep the frequency constant but increase the coil current.

Question 2

The 'standard depth of penetration' in eddy current testing is defined as the depth at which the eddy current density decreases to approximately what percentage of its surface density?

Accepted Answer

37%

Answer

50%

Answer

10%

Answer

75%

Question 3

Which of the following material properties has the MOST significant influence on the magnitude and distribution of induced eddy currents?

Accepted Answer

Electrical Conductivity

Answer

Tensile Strength

Answer

Ductility

Answer

Thermal Expansion Coefficient

Question 4

An inspector is using an eddy current surface probe on a flat plate and observes a signal change as the probe is moved slightly away from the surface. This phenomenon is known as:

Accepted Answer

Lift-Off

Answer

Fill Factor

Answer

Edge Effect

Answer

Phase Lag

Question 5

On an impedance plane diagram, the phase angle (or phase lag) of a defect signal provides crucial information about the defect's:

Accepted Answer

Depth

Answer

Length

Answer

Orientation

Answer

Width

Question 6

When testing a ferromagnetic material, an inspector notes that the depth of penetration is very shallow compared to a non-ferromagnetic material with similar conductivity. This is primarily due to the ferromagnetic material's high:

Accepted Answer

Magnetic Permeability

Answer

Electrical Resistivity

Answer

Modulus of Elasticity

Answer

Density