Methods of Non Destructive Testing

Non destructive testing means the methods or techniques that are used to check or examine the properties of objects, materials or systems without any destruction. It is a process that saves time and cost for research, evaluation and troubleshooting of products. There are many non destructive testing methods such as low coherence interferometers, eddy current testing, radiographic, magnetic particle, ultrasonic, liquid penetrate, remote visual inspection etc.

NDT is most commonly used in civil engineering, mechanical engineering, forensic engineering, aeronautical engineering, medicine and electrical engineering. There are some professional companies working on non destructive testing. These companies are specialized in certain fields like magnetic particle inspection (MT), dye penetrated inspection (PT), eddy current inspection (ET), radiography X-ray (RAD), ultrasonic flaw detection (UT), and ultrasonic thickness gauging.

Magnetic particle inspection (MT) is used to examine the defects on surface. It is the most widely used method of NDT around the globe. It is very easy to do and the component surface preparation is not very critical. In magnetic particle inspection, magnetic fields which are induced by electro magnet or small magnetic particles are used to detect flaws in components. MT is widely used to check the ability of certain products to be used in the industries.

Dye penetrated inspection (PT) is the most cheap and easiest method in non destructive testing. This method is used for testing the casting and forging defects, leaks and cracks in the products. The steps followed in dye penetrate inspection are surface penetration, penetrate application, excess penetrate removal, developer application, indicator application, inspection and cleaning. 

Eddy current inspection (ET) is one of the important methods of non destructive testing which works on the principle of electromagnetism. There are many advantages for eddy current inspection (ET) with certain limitations. This method is used for metal thickness measurement, crack detection, conductivity measurements, coating thickness measurement etc.

Radiography X-ray method (RAD) is another method of non destructive testing which is mainly used to detect imperfections in the product and certain parts by passing gamma rays or X rays which penetrates into them. This method can check both the imperfection of materials as well as imperfection of manufacturing and assembling.

Ultrasonic inspection (UT) is also a method of non destructive testing where sound energy with high frequency is used to conduct inspections and take measurements. There are number of ways followed in ultrasonic inspection such as flaw detection or evaluation, character finding of materials, thickness gauging and dimensional measuring.

One of the widely used methods of non destructive testing is the visual inspection. This is a simple method to be done with great care to check defects, poor welding, protective coating monitoring, corrosion and pitting, surface degradation & general condition monitoring etc.