In NDT, which method is primarily used for thickness measurements?

Ultrasonic Testing (UT) is primarily used for thickness measurements because it utilizes high-frequency sound waves that are transmitted into the material being tested. When these sound waves encounter a boundary, such as the interface between the material and any defect or at its back wall, they are reflected back to the surface. By measuring the time it takes for the echoes to return, the thickness of the material can be calculated. This method is highly effective for measuring the thickness of metals, plastics, and composites, providing accurate and reliable data without causing any damage to the test object.

In contrast, X-ray Testing is primarily used for detecting internal flaws rather than measuring thickness, as it relies on the differential absorption of X-rays to reveal the internal structure. Magnetic Particle Testing is designed to identify surface and near-surface discontinuities in ferromagnetic materials by using magnetic fields and iron particles. Liquid Penetrant Testing is also focused on finding surface defects and does not gauge material thickness, as it works by applying a penetrant that seeps into surface-breaking defects. These methods serve different purposes and are not suitable for direct thickness measurements like Ultrasonic Testing.