Which nondestructive testing method uses sound waves to detect defects and can be applied to bolts, pins, and railing?

• A. Acoustical Testing
• B. Ultrasonic Testing
• C. Magnetic Particle Testing
• D. Radiographic Testing

Answer: (B)

Ultrasonic testing uses high-frequency sound waves to probe metal parts. A transducer sends waves into the material and listens for echoes that bounce off internal flaws, voids, or boundaries. The reflections reveal the presence and size of defects, and can also be used to measure remaining thickness. This makes it ideal for bolts, pins, and railing because these metal pieces can be small or complex, yet UT can detect internal cracks or inconsistencies that aren’t visible on the surface. The method works well on ferrous and nonferrous metals and can inspect through coatings or rough surfaces with proper coupling between the transducer and the part.

Other methods rely on different principles: some use magnetic fields to find surface or near-surface flaws in ferromagnetic materials, some use radiation to image internal features, and others reference general acoustics without the specialized, high-frequency probing of UT. Ultrasonic testing specifically employs sound waves, which is why it’s the best fit for detecting internal defects in bolts, pins, and railing components.