LR12838 - How do arches break under vibration? It turns out that arches sporting a neat, clean shape resist better than those with geometrical imperfections. In a recent experiment, physicists first create arches in a vertical layer of small spheres and then submit them to controlled perturbations. After considering several geometrical features of the arches such as size or aspect ratio, they conclude that the danger is concentrated at places where the arch departs from a perfect, uniform shape. Worse still, if one of the beads is hanging from its neighbors due to friction, odds are high that the arch will break just there, as observed in high-speed recordings. Moreover, the more prominent the defect, the easier it is to shatter the arch. Other variables, such as the number of beads, only affect the robustness to the extent that they influence the probability of finding a defect. The researchers also point to the forces between the spheres and the friction coefficient of the material as issues deserving a closer look. Apart from the obvious hits for designing stronger structures, this could also help in getting weaker ones - which could be interesting, for instance, to avoid clogging in particulate flows.
