What pattern indicates the presence of inclusions in magnetic particle inspection?

The presence of inclusions in magnetic particle inspection is indicated by parallel lines forming a buildup. This pattern suggests that the magnetic particles have gathered in response to the magnetic field's interaction with subsurface discontinuities, such as inclusions. When the magnetic field is applied, any defects or inclusions can disrupt the uniform flow of the magnetic particles, causing them to cluster along these lines.

Inclusions disrupt the magnetic fields locally, leading to variations in the field intensity. As the magnetic particles orient themselves along the field lines, the buildup creates a visual indication of these defects, which will appear as parallel lines. This is crucial for inspectors because it helps in identifying specific areas that may require further evaluation or repair.

Other patterns may not definitively indicate the presence of inclusions. For example, random dots could signify noise or surface contamination and might not represent significant internal flaws. Circular patterns often indicate surface defects like cracks rather than inclusions. Concentric rings typically reflect magnetic pole effects or surface-shaped anomalies rather than inclusions themselves. Understanding these nuances allows inspectors to accurately interpret the results of magnetic particle inspections and address potential material defects effectively.