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Non-destructive Testing: Important Terminology

Updated: Feb 27, 2020

There are many different non-destructive testing techniques recognized by the American Society for Non-destructive Testing (ASNT) including Acoustic Emission Testing (AE), Electromagnetic Testing (ET), Ground Penetrating Radar (GPR), Laser Testing Methods, Leak Testing (LT), Liquid Penetrant Testing (PT), M

agnetic Flux Leakage (MFL), Magnetic Particle Testing (MT), Microwave Technology, Neutron Radiography Testing, Radiographic Testing, Thermal/Infrared Testing, Ultrasonic Testing, Vibration Testing, and Visual Testing. It is interesting to note, however, that most of these techniques process non-destructive testing information in the same sequence to determine the final conclusion on an indication or to answer the existential question; is it a defect or is it not a defect?



ASTM E1316, Standard Terminology for Nondestructive Examinations is good starting point from which key non-destructive testing terms are defined. Additionally, this standard provides a simple but useful chart that presents the basic decision making steps that follow an non-destructive testing (NDT) indication through interpretation to acceptance or rejection. First let’s review the some basic non-destructive testing definitions and see where they fit into the decision making process.





Non-destructive testing indication: The response or evidence from a nondestructive examination. This is located at the top of the process.


Non-destructive interpretation: The determination of whether indications are relevant, non-relevant, or false.


False indication: A non-destructive testing (NDT) indication that is interpreted to be caused by a condition other than a discontinuity or imperfection.


Relevant indication: A non-destructive testing (NDT) indication that is caused by a condition or type of discontinuity that requires evaluation.


Non-relevant indication: A non-destructive testing (NDT) indication that is caused by a condition or type of discontinuity that is not rejectable.