Originally Posted by
Airburst
I was told by my materials lecturer (I'm a first-year mechanical engineering student) that a lot of structures aren't designed to always keep the stresses below the fatigue limit, because they'd be quite a bit heavier if they were. I'm not sure traditional steel frames and forks are "designed" in that sense anyway, but if I was designing a fork that I was going to be riding, I might put up with a bit of excess weight in order to keep the stress below the fatigue limit for a decent proportion of the time. I don't know if that's actually how manufacturers do it, though.
Me too, but given the typical endurance limit for steel 10^7 to 10^8 how much riding would it take to stress a fork beyond the fatigue limit that many times? The fatigue limit for steel is roughly around half of its tensile strength right? (I'm not in a materials class, so seriously.) If that's right then it takes pretty big jar to pass that limit. Doing that 10 million times I think you'd have to be riding rough trail really hard, eight hours every day, for ten years. So it's not really a factor we'd need to worry about much imo, for steel.