What does non-destructive testing (NDT) involve and why is it used?

• A. NDT destroys the part to reveal hidden defects.
• B. NDT only tests electrical systems.
• C. Non-destructive testing uses methods like dye penetrant, magnetic particle, or eddy current to detect defects without damaging the part.
• D. NDT is a cosmetic inspection.

Answer: (C)

Non-destructive testing involves inspecting a component for flaws without damaging it, so you can confirm its integrity while keeping it in service. Dye penetrant testing uses a liquid that seeps into surface-breaking cracks and, after a developer and proper lighting, reveals indications that’d be hard to see otherwise. Magnetic particle testing magnetizes ferromagnetic parts and applies magnetic particles; defects at or near the surface disrupt the magnetic field and attract particles to visible regions. Eddy current testing uses a coil to induce currents in a conductive material; changes in impedance reveal cracks, corrosion, or thinning without taking the part apart. These methods are used because they can detect hidden or subsurface defects quickly and relatively inexpensively, work on complex shapes, and preserve the component for continued use, improving safety and reliability. It’s not about destroying the part, it isn’t limited to electrical systems, and it isn’t just a cosmetic check.