Non-Destructive Testing (NDT) Practice Test

Which method results in the most effective detection of surface defects?

1. Using high-frequency AC currents

2. Magentic particles in a wet suspension

3. All indications pointing into longitudinal fields

4. Perpendicular magnetization relative to defect orientation

The correct answer is: Perpendicular magnetization relative to defect orientation

The most effective detection of surface defects is achieved through perpendicular magnetization relative to defect orientation. This method enhances the magnetic flux leakage at the site of a surface defect, making it easier to detect indications. When the magnetization is applied perpendicular to the orientation of the defect, it allows for a more pronounced disturbance in the magnetic field around the defect, which subsequently results in clearer signals being produced for inspection purposes. In non-destructive testing techniques, particularly in magnetic particle testing, the relationship between the orientation of the defect and the direction of the magnetic field is crucial. When defects such as cracks or voids are oriented perpendicular to the magnetic field, they disrupt the flow of the magnetic field lines most effectively, leading to better visibility of the defects when magnetic particles are applied. The other methods, while they have their applications, do not capitalize on this specific interaction to the same extent. For example, high-frequency AC currents can detect certain types of defects but may not be as sensitive to surface-breaking flaws as direct magnetic particle methods. The use of magnetic particles in a wet suspension aids in coverage and detection but is less effective without ensuring the correct magnetization orientation. Similarly, while all indications pointing into longitudinal fields may provide some visibility of defects, it does not optimize