Why is the selection of the magnetization method critical in magnetic particle testing?

The selection of the magnetization method in magnetic particle testing is crucial because it directly influences the type of defects that can be detected. Different magnetization methods, such as continuous or residual magnetization, create varying magnetic fields that affect the sensitivity and depth of penetration of the magnetic field into the material. This means that certain methods may be more effective at revealing surface defects like cracks, while others may be better suited for detecting subsurface defects.

For example, if a method prone to shallow magnetization is chosen, it could lead to missed indications of deeper flaws that would not be present in the magnetic field created by that method. Therefore, understanding the characteristics of each magnetization method allows inspectors to appropriately select a technique that aligns with the material type, geometry, and expected defect types in order to enhance the efficacy of the testing process.