Materials and Structure

Bicycle Front Forks

An example of selecting a material for a specific use is a high performance front fork for a bicycle. The front fork transfers the load to the front hub and makes an angle to the line of action of the resultant force. The members of the fork experience both compressive and bending forces and may be thought of as cantilever beams when identifying suitable fabricating materials. The forks must operate in their elastic range and, therefore, possible materials are identified in terms of their transition to plastic deformation or fracture.

The compressive stress acting on the fork is well within the elastic range, and the selection of a suitable cross-sectional shape will keep expected loads outside the compressional buckling range. It is the force normal to the fork that presents the problem, particularly if the wheel hits a curb or other road hazard. The fork can then fail by bending. The selection criterion for this case is finding a material with the maximum value of (s_y/r^3/2). Shape, fabrication method, cost, etc., can then be examined.