another option.

já traduzi esse termo um sem-número de vezes! <hope it helps>

Introduction
Non Destructive Testing (NDT) is the name given to any form of testing or inspection that can verify the structural integrity of a component without compromising its ability to perform in service.


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Non-destructive testing methods
Visual inspection
Liquid penetrant testing
Magnetic particle testing
Acoustic monitoring
X Ray testing
Ultrasonic testing
Digital technology
Past HSC question and sample answer


Liquid penetrant testing

The test specimen is first thoroughly cleaned and dried before the test. A liquid penetrant is applied to the surface; spraying, dipping or brushing may do this. Over a period of time the liquid penetrant is drawn into any surface faults by capillary action, any excess liquid is removed. Depending on the process being used, the surface is coated with whiting or a developer. Faults open to the surface will appear as a discoloured line in the whiting. Fluorescent or coloured dyes drawn into the faults are readily seen under ultraviolet light or as a line in the developer.

Liquid penetrant tests are simple, versatile, portable and inexpensive. The results are easy to interpret but only surface faults can be detected. If a permanent record is required a photograph or videotape or inspectors report may be kept. The use of laser scanners and digital control allows this process to be used as a mass production technique


Liquid Penetrant Testing
Apart from visual inspection this is probably the oldest and most widely used of all the NDT methods. It can be used on any non-porous material. Its use is confined to the detection of surface breaking defects.

A coloured or fluorescent dye, when applied to a clean surface and allowed to dwell for 10 to 20 minutes, will be drawn into the discontinuity by capillary pressure. The capillary pressure is determined by the width of discontinuity, surface tension and contact angle of the dye on the surface.

The excess dye is then removed from the surface and a developer applied, Figure 1.

The developer has two functions to assist in drawing the dye back out to the surface, giving an indication to assist in seeing this indication by giving good visual contrast.

After a time, usually a minimum of 10 minutes, the surfaces are visually inspected. White light is used for red dyes, ultra-violet light for fluorescent dyes.