Radiographic inspection is based on exposure of the components to short wavelength electromagnetic radiation in the form of X-rays or gamma rays from a suitable source. The amount of radiation absorbed by a particular part is a function of its thickness and density. The variation in the transmitted radiation can be detected with the aid of photographic films, fluorescent screens or counting equipment.
Ultrasonic Testing (UT) is employed for flaw detection, quality evaluation and also for thickness measurement. In these methods’ ultrasonic waves, which are high frequency sound waves are allowed to propagate inside the specimen and the transmitted or reflected ultrasonic waves are analyzed for flaws or thickness measurement.
Magnetic Particle Testing
Method applicable to ferromagnetic materials, which can easily be magnetized. This method involves disturbance of magnetic flux lines, (leakage flux) and detection of the same.
If the method employs finely divided ferromagnetic particles for the detection of leakage flux, then the method is known as Magnetic Particle Testing.
This method is used to reveal surface discontinuities by bleed out of colored or fluorescent dye from the flaw. The method is based on the ability of a liquid to be drawn into a clean surface discontinuity by capillary action. After a period of time called the dwell time, the excess surface penetrant is removed and a developer applied. This act as a blotter that draws penetrant from the discontinuity to reveal its presence.
Visual Testing is a nondestructive testing technique that provides a means of detecting and examining a variety of surface flaws, such as corrosion, contamination, surface finish, and surface discontinuities on joints (for example, welds, seals, solder connections, and adhesive bonds). It is a simple, accessible, low-cost inspection method, but it requires a trained inspector. Additionally, it can be an excellent process-control tool to help avoid subsequent fabrication problems and evaluate workmanship.