Table of Contents

Materials and Structure





n real engineering situations materials experience fluctuating loads during use. The magnitude of the stress fluctuation may be within the elastic range of the material, however, it is found that material failure can occur through the process known as fatigue.

In the bicycle, two types of location are prone to fatigue failure: the spokes that are always in tension and experience a fluctuating stress for each revolution of the wheels, and the joints between frame members. The photographs show a spoke that failed by fatigue. The nipple section (a) shows that the crack started in the threaded region of the spoke. (b) shows the fracture surface, the black arrow showing where the crack started and the top, matt grey section being the final fast fracture region.

From: McMahon and Graham,
"The Bicycle and the Walkman,"
Merion (1992)