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COMPONENT FAILURE MUSEUM

The main sections of the museum are listed below;

Metal Fatigue
Manufacturing Faults
Bicycle Components
Corrosion
Polymers
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Bending fatigue fracture

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 Reversed bending fatigue fracture starting from keyway

This 100 mm diameter steel shaft failed after a long period of service on a large dumper truck. The keyway terminated in a circumferential groove approximately half the depth of the keyway. Fatigue cracks initiated at both corners of the keyway had propagated into the cross section at 900 to the shaft axis, following the sharp corner of a circumferential groove. The crack arrest fronts are close together and the surface fairly smooth, showing that the propagation was slow at first but progressively increasing as the effective cross sectional area decreased.

Eventually, so little cross section remained that the final separation took place under a normal torsional load. This appears as the rougher, pear shaped area near the centre.
This is the kind of failure expected when keyways and recesses in shafts are machined with inadequate radiuses at their roots, thus leading to high stress concentrations under the applied loads.

Return to metal fatigue section

ed: KR 17/12/01

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