Which non-destructive testing method is used to detect internal weld discontinuities using ultrasonic energy?

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Ultrasonic testing uses high-frequency sound waves to probe the interior of a weld. A transducer sends a pulse into the material through a coupling medium, and when the wave encounters a flaw like porosity, lack of fusion, or a crack, part of the energy is reflected back as an echo. The tester reads these echoes to determine whether a discontinuity exists, and can estimate its location and size based on the travel time and signal strength. This method is ideal for detecting internal weld defects because the waves travel through the metal and reveal features that aren’t visible from the surface.

In contrast, magnetic particle testing detects surface and near-surface flaws in ferromagnetic materials, liquid penetrant testing reveals surface-breaking defects, and radiography images internal features using penetrating radiation. Ultrasonic testing specifically provides a direct look inside the weld, making it the method of choice for internal weld discontinuities.