Comparison of NDT Methods | Welding & NDT Tips for QA/QC Inspector

Comparison of Non-Destructive Testing Methods

Non-destructive testing (NDT) is a testing and analysis technique used by industry to evaluate the properties of a material, component, structure, or system for characteristic differences or welding defects and discontinuities without causing damage to the original part. NDT is also known as non-destructive examination (NDE), non-destructive inspection (NDI), and Non-destructive evaluation (NDE).

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As we know, non-destructive testing can generally be split into two areas: surface techniques and sub-surface techniques. These techniques are then categorized into various testing methods such as visual testing, liquid penetrant testing, acoustic emission testing, leak testing, radiography, ultrasonic testing, magnetic particle testing, eddy-current testing, vibration analysis, thermal/infrared testing, and laser testing.

Let’s have a look at the points which differentiate them from each other.

Visual Testing	VT	Oldest forms of testing	Can check for damage including cracks, corrosion, and misalignment
Liquid Penetrant Testing	LT	Flexible technique used in the aviation industry	Can detect surface defects and structural damage in non-porous materials
Acoustic Emission Testing	AE	An abrupt force is used	Leaks and active corrosion can be detected
Leak Testing	LT	Involves pressurizing & immersing the test object in a liquid	detects gas (usually air) leaking from the test piece in the form of bubbles.
Radiographic Testing	RT	can use both x-rays for thin materials and gamma rays for thicker materials	To show discontinuities in the testing object
Ultrasonic Testing	UT	uses high-frequency sound waves to locate defects	conduct examinations and measurements on a test area
Magnetic Particle Testing	MT	involves inducing a magnetic field in the test object	find discontinuities at or near the surface of ferromagnetic materials
Eddy-current Testing	ECT	induces an electromagnetic field in a conductive test object	measures the secondary magnetic field generated around the electric current
Vibration Analysis	VA	used to monitor the vibration signatures generated by a rotating piece of machinery	-
Thermal/Infrared Testing	IRT	mapping the surface temperatures of an object	used to detect damage such as corrosion, delamination, voids, and disbonds
Laser Testing Methods	LMT	Useful in detecting tiny flaws	use laser light in different ways to detect deformation on the surface of objects and computer processing to compare stressed and unstressed conditions