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The main sections of the museum are listed below;

Metal Fatigue
Manufacturing Faults
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Manufacturing Faults

A problem with replacement gears

For a brief overview see below
or follow this link for the full case history

Click on pictures below for full size image in new window

The forged and machined gear, on the right, ran successfully until the small inner teeth gradually showed excessive wear. The replacement fully machined spare part, shown on the left, failed immediately in service as the inner teeth sheared off.

 

 Sections taken from both are shown polished and macro etched (deep etch) on the left.

The original forging on the left shows flow lines indicating a forged pre-form was produced before final machining. The section from an unused spare recently machined from a solid bar shows flow lines across the roots of the small teeth (arrowed).

 

 This is OK on small lightly stressed gears (see left) but the planes of weakness cause problems in highly stressed forgings. The component was re-forged correctly.

Return to Manufacturing faults

17/12/01 ed:AG

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