Biaxial Testing and Analysis of Bicycle-Welded Components for the Definition of a Safety Standard

This paper presents the experimental evaluation of the fatigue behaviour of welded components under non-proportional variable amplitude biaxial loads. The study was undertaken on welded mountain bike handlebar stems, which were different in terms of geometry and technology and tested with load histories that were reconstructed and accelerated from recorded field data. Loads measured in the field were decomposed into bending and torsional components; a synchronous Peak-Valley counting, a spectrum inflation technique, a spline interpolation and a final amplification were applied to the measured signals in order to obtain test drive signals with the correct content of biaxial non-proportional loadings. After evaluation of the bending and torsion load-life curves of components under constant amplitude fatigue, the resulting data from biaxial variable amplitude fatigue tests were analysed in order to evaluate the damage contribution as a result of the two load components and an equivalent simplified two-stage constant amplitude fatigue test was proposed to the working group ISO/SC1/TC149/WG4.