What are the 4 types of NDT?

Four Types of Non-Destructive Testing (NDT)

Non-Destructive Testing (NDT) is a group of analysis techniques used in science and industry to evaluate the properties of a material, component, or system without causing damage. The following are four primary types of NDT:

1. Ultrasonic Testing (UT)

Ultrasonic Testing uses high-frequency sound waves to detect imperfections or changes in the properties of materials. It is commonly used to find defects in welds and to measure the thickness of materials. A transducer connected to a diagnostic machine is passed over the object being inspected. The sound waves travel through the material and reflect back to the transducer, which converts them into electrical signals that can be interpreted.

2. Radiographic Testing (RT)

Radiographic Testing involves the use of X-rays or gamma rays to view the internal structure of a material. This method is particularly useful for identifying cracks or voids inside complex structures. The process requires exposing a photographic film or digital detector to radiation that has passed through the material, creating an image that shows the material's internal features based on varying levels of radiation absorption.

3. Magnetic Particle Testing (MPT)

Magnetic Particle Testing is used to detect surface and slightly subsurface discontinuities in ferromagnetic materials. The process involves magnetizing the material and then applying ferrous particles to the surface. The particles will gather at areas of flux leakage, such as cracks or voids, making them visible under proper lighting conditions.

4. Liquid Penetrant Testing (LPT)

Liquid Penetrant Testing is a method used to reveal surface-breaking defects in non-porous materials. A liquid with high surface wetting characteristics is applied to the surface of the part and allowed to seep into any flaws. After a predetermined time, the excess liquid is removed, and a developer is applied to draw out the penetrant from the defects, making them visible.