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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

 

Bicycle component failures.

Titanium seat post failure.

Click on pictures below for larger image.

 This lightweight titanium alloy cycle seat post lasted only 500m before failure of the seat rail clamping mechanism caused the seat to tilt forwards.
The hinge mechanism required three cylindrical sections to be welded to thin plates as shown.

 

The failure of the weld on both sides of the central hinge cylinder occured. This photograph shows the limited extent of the weld penetration on both sides.

A microsection through the weld revealed that where penetration was present it appeared metallurgically sound.


However the shape of the unpenetrated region was that of an internal notch. This shows the side of the weld next to the thicker walled hinge cylinder. Even there the fracture event had nucleated a sharp crack in the corner of the weld penetration defect.

The component had a manufacturing process that included a very poor design and an unacceptable welding procedure. Several indentical failures were reported to the importer and the seat post was withdrawn from sale.

Return to bicycle components

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12/03/02 ed:AG

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