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COMPONENT FAILURE MUSEUM

The main sections of the museum are listed below;

Metal Fatigue
Manufacturing Faults
Bicycle Components
Corrosion
Polymers
Composite Materials

Tools of the trade, some ways to investigate problems;
Photoelasticity
Dye penetrant testing

Glossary
of materials engineering terms


Dye-penetrant testing

Dye-penetrant testing; a method of examining components to detect surface-breaking flaws, such as cracks. The technique is based on the ability of a liquid to be drawn into a "clean" surface-breaking flaw by capillary action.

It is essential that the component to be inspected is thoroughly cleaned to remove all traces of dirt and grease.

It is then sprayed with a penetrating liquid, usually a brightly coloured liquid or a fluorescent dye, which penetrates any surface-breaking cracks or cavities.
The liquid is allowed to soak into the components surface. (Fig1 right)

After soaking, the excess liquid penetrant is wiped from the surface and a developer applied. The developer is usually a dry white powder, which draws the penetrant out of any cracks by reverse capillary action to produce indications on the surface.(Fig2 right)

These (coloured) indications are broader than the actual flaw and are therefore more easily visible.
Fluorescent penetrants are normally used with a UV lamp to enhance sensitvity.

These systems are often used to check weld quality during fabrication.

 

Fig1

Fig2

Follow these links for two examples of dye penetrant testing used on bicycle components.
Crank 2 & Crank 3

 

Ed; AG 9/4/03

 
 
© 2005 Materials Engineering - Page last modified 18-Dec-2007