Non-Destructive Testing (NDT) Practice Test

What is the primary function of a pie gage in magnetic particle testing?

1. To measure the thickness of coatings

2. To provide an indication of field direction

3. To detect surface cracks

4. To calibrate the magnetic field strength

The correct answer is: To provide an indication of field direction

The primary function of a pie gage in magnetic particle testing is indeed to provide an indication of field direction. In magnetic particle testing, it is essential to know how the magnetic field is oriented, as this directly affects the detection of surface discontinuities. The pie gage consists of a set of indicators that can visually show the direction of the magnetic field, allowing operators to understand how the magnetic particles are likely to accumulate in the presence of cracks or flaws. This capability is crucial because for effective inspection, the magnetic field needs to be aligned appropriately with the expected orientation of potential defects. Understanding the field direction ensures that any surface imperfections can be effectively highlighted by the magnetic particles, leading to more accurate results during inspections. The other options focus on functions that are not directly relevant to the role of a pie gage in this context. Measuring coating thickness, detecting cracks, and calibrating magnetic field strength relate to different aspects of magnetic particle testing or other testing methods, but they do not involve the primary purpose of the pie gage itself.