Non-Destructive Testing (NDT)



NDT/NDE has been practiced for decades. Over the years, technological advances spurred rapid developments in techniques and instrumentation. It is impossible to identify exactly when this science began; however, we know that it has been evolving for centuries. For example, blacksmiths used a sonic technique (listening to a ring of different metals) to shape them as desired.


The roots of modern NDT/NDE began prior to the 1920s, but awareness of different methods truly came in the 1920s. During this era there was an awareness of some of the magnetic particle tests (MT) and X-radiography (RT) [in the medical field].

In the early days of railroad, a technique referred to as the “oil and whiting test,” was used and staged the ground for the present day penetrant test (PT). As well, there were some basic principles of eddy current testing (ET) and archaic gamma radiographic techniques. But the majority of the methods that are known today didn’t appear until late in the 1930s and into the early 1940s.

Pre World War II, designers had to engineer with unusually high safety factors for many products, such as pressure vessels and other complex components. Discontinuities and imperfections [relative to lifecycle] became a concern. Catastrophic failures due to product inadequacies brought concern for quality to the forefront. In 1941, the American Industrial Radium and X-ray (now the American Society for Nondestructive Testing) was formed marking the beginning of organization of this field.

A key period in the history and development of nondestructive testing came during and after the Second World War. During the earlier days, the primary purpose was the detection of defects. The war expedited the development of techniques that allowed higher-integrity, more cost- effective production.

From the late 1950’s to present, NDT/NDE has seen exponential advancement. The evolution of NDT/NDE is directly related to safety, the development of the new materials, and the demand for greater product reliability. The changes that have occurred in construction, aerospace, nuclear applications, manufacturing and space exploration would not have been possible without the application of NDT and NDE. 


Pre− 1850

1850 − 1879

1880 − 1899

1900 − 1919

1920 − 1929

1930 − 1939

1940 − 1949

1950 − Present


Current NDT methods are: Acoustic Emission Testing (AE), Electromagnetic Testing (ET), Laser Testing Methods (LM), Leak Testing (LT), Magnetic Flux Leakage (MFL), Liquid Penetrant Testing (PT), Magnetic Particle Testing (MT), Neutron Radiographic Testing (NR), Radiographic Testing (RT), Thermal/Infrared Testing (IR), Ultrasonic Testing (UT), Vibration Analysis (VA) and Visual Testing (VT).


The six most frequently used test methods are Visual Testing (VT), Magnetic Particle Testing (MT), Liquid Penetrant Testing (PT), Radiographic Testing (RT), Ultrasonic Testing (UT) and Acoustic Emission Testing (AET). Each of these test methods will be described here, followed by the other, less often used test methods.

The document was created: 13. 12. 2018 10:09:33