Non-Destructive Testing (NDT) Practice Test

Which factors influence the depth of eddy current penetration?

1. The conductivity of the material

2. The frequency of the eddy current

3. The geometry of the test piece

4. All of the above

The correct answer is: All of the above

The depth of eddy current penetration into a material is influenced by a variety of factors, making the correct choice comprehensive. The conductivity of the material plays a crucial role because materials with higher conductivity allow eddy currents to flow more easily, which in turn affects penetration depth. When the conductivity is low, the penetration depth tends to be greater since the eddy currents do not dissipate as rapidly. The frequency of the eddy current is also significant; as frequency increases, the skin effect causes eddy currents to concentrate closer to the surface, reducing penetration depth. Conversely, lower frequencies allow for greater penetration of the eddy currents into the material. The geometry of the test piece matters as well, since its shape and surface conditions can alter how eddy currents flow and distribute throughout the material. Irregular shapes or variations in geometry can create different current paths, impacting the overall effectiveness and depth of the inspection. Since all these factors collectively influence eddy current penetration depth, the most accurate answer reflects their combined effect.