Non-Destructive Testing (NDT) Practice Test

Which indications appear best with a longitudinal magnetic field?

1. Only indication A

2. Only indication B

3. Indications A and C

4. Both indications B and D

The correct answer is: Indications A and C

In magnetic particle testing (MT), the effectiveness of detecting surface and near-surface discontinuities is influenced by the orientation of the magnetic field relative to the indications being evaluated. A longitudinal magnetic field is established parallel to the direction of the expected cracks or defects. In this context, indications A and C would align well with a longitudinal magnetic field, making them more visible. Indication A may be a crack or flaw that runs parallel to the applied magnetic field, allowing the magnetic particles to accumulate at the flaw and create a visible indication. Indication C might represent another type of defect that also aligns well with the field, enhancing its visibility due to the same principle of magnetic attraction towards the discontinuity. Other options do not account for the types of indications that are best suited for longitudinal magnetic field applications, where indications that align with the magnetic flux lines can be highlighted more effectively than those that do not. Thus, seeing both indications A and C clearly demonstrates the effectiveness of the longitudinal magnetic field in revealing relevant defects.