Non-destructive testing (NDT) is essential for verifying the integrity, safety, and reliability of materials and structures without causing damage. Widely used across engineering, manufacturing, and infrastructure sectors, NDT enables early detection of flaws, supports compliance with standards, and helps maintain operational performance.
This guide outlines seven commonly used NDT methods, explaining how each works, its advantages, and typical applications.
Overview
Visual Testing is the most basic form of NDT. It involves direct observation of a component’s surface to identify visible defects such as cracks, corrosion, misalignment, or weld discontinuities.
Advantages
Typical Applications
Overview
Ultrasonic Testing uses high-frequency sound waves to detect internal flaws. A transducer sends sound waves into the material, and reflections from discontinuities are analysed to determine their location and size.
Advantages
Typical Applications
Overview
Phased Array UT is an advanced ultrasonic technique that uses multiple transducer elements and electronic beam steering to produce detailed images of internal structures.
Advantages
Typical Applications
Overview
Liquid Penetrant Testing involves applying a dye to the surface of a non-porous material. The dye penetrates surface-breaking defects and is then drawn out with a developer to reveal flaws.
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Typical Applications
Overview
Magnetic Particle Testing uses a magnetic field and iron particles to detect surface and near-surface flaws in ferromagnetic materials. Flaws disrupt the magnetic field, causing particles to gather at the defect site.
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Typical Applications
Overview
Radiographic Testing uses X-rays or gamma rays to create images of a component’s internal structure. Flaws appear as variations in density on the radiograph.
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Typical Applications
Overview
Eddy Current Testing uses electromagnetic induction to detect surface and near-surface flaws in conductive materials. Variations in the eddy current flow indicate the presence of defects or material changes.
Advantages
Typical Applications
Each NDT method offers distinct advantages depending on the material, defect type, and inspection context. A sound understanding of these techniques enables engineers, inspectors, and quality professionals to select the most appropriate method for their needs—supporting safety, compliance, and operational reliability across a wide range of industries.