Defects not detectable by dye-penetrant or magnetic particle methods can be found by using which method?

• A. Ultrasonic method
• B. Radiographic method
• C. Magnetic particle inspection
• D. Eddy current method

Answer: (B)

Defects hidden inside a part require inspection that can image through the material, not just inspect the surface. Dye-penetrant shows flaws that reach the surface by letting dye seep into openings, and magnetic particle inspection reveals flux leakage near the surface in ferromagnetic parts. To actually visualize internal features like porosity, inclusions, voids, or cracks inside a solid or weld, radiographic testing uses penetrating radiation (X-ray or gamma) to create an image of the part’s interior. This lets you see defects that surface methods can miss, regardless of their orientation or location within the volume. While ultrasonic testing can also detect internal flaws, radiography uniquely provides a direct internal image, making it the best choice for locating defects that dye-penetrant and magnetic particle methods cannot detect.