Jerry wrote Maybe I'm too complacent, but I remain unconvinced that quality alloy > bicycle components fail catastrophically and without warning any more ...snip... > cracks. And if I detect cracks, the component is removed immediately > and used for display only. And John replied Be that as it may, but aluminum does not fail gradually like steel, but catastrophically, going from an initial crack to complete failure very quickly -- sometimes in a matter of only a few stress cycles.
My experience with broken cranks (both at the pedal eyes,one SR and one Boone) tells me that aluminium does not fail quite as quickly as that.On examination after the failures,both of which sent me down the road,some of the fractured surface was new and shiny and some of the surface showed obvious signs of having dirt on it.In other words at least part of the crack had been there for a while and the shiny new looking bit had given way when the crank broke.The clear lesson in this for me is that I should examine my cranks more regularly and in the case of the Boone's avoid cranks with such a small pedal end.Boy it was small. Geoff Duke Melbourne Australia