Definition: Material Fatigue and Failure

February 7, 2009

in Engineering

What I experience every day.

Fatigue, when discussing materials, is structural damage caused by cyclic loading that exceeds the lower threshold of the material’s fatigue endurance.  This damage accumulates and progresses during cyclic loading to the eventual point of failure.

Definition of industry standard fatigue testing for bicycle frames can be summarized as follows:

For bicycle frames, the industry standard is the DIN standard.  DIN stands for Deutsches Institut für Normung, or, the German Institute for Standardization, that country’s governing ISO body, with over 30,000 standards.

DIN standard 14781 requires a bicycle frame to survive the maximum loading from an 180lb rider for 100,000 cycles. Failure, in the DIN standard, is not defined as catastrophic; rather it is defined as a 20% increase in frame deflection for the specified load of 1100N.

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