Influence of manufacturing defects in bicycle frames on their fatigue strength

The paper presents a methodology for the computational assessment of the fatigue strength of bicycle frames, taking into account the specific characteristics of their manufacture and operation. Several technologies are used in the manufacture of bicycle frames, including welding, gravity casting, pressure casting, hydroforming, etc. Each technology creates a different microstructure and carries a risk of defects. The design also requires a computational estimate of the fatigue life, which is then experimentally verified according to standards for bicycle frame testing (ISO 4210/EN 14766, Zedler test, etc.). The engineering calculation of fatigue life assumes the same cyclic properties of the frame material and ideal geometry of the structure. The paper analyzes defects in industrially manufactured aluminum alloy frames and geometric deviations of their design from the ideal shape. An experimental simulation methodology for determining the relevant load spectrum for individual operating conditions of bicycle frames is proposed and discussed.