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Don't think I can afford that experimental setup Alan, I'll try it with a packet of spaghetti first.
I haven't tackled the spaghetti question yet, but I recall launching gliders with a tow truck and 600m of steel wire. If the truck accelerated too quickly from slack, the cable would break with a very satisfying bang, and always into 3 pieces. But if you had established a constant tension and the glider was climbing smoothly, a little extra enthusiasm from the pilot could cause the cable to break in just one place.
I was speaking with a friend from the engineering giant Rolls-Royce the other day; he told me that at one of their recent interviews for new recruits they were asking candidates to explain why spaghetti break into 3 pieces rather than 2 when you hold each end and snap it.So what's the correct answer?Chris
... Contrary to the intuition that removing a loading decreases stresses and so cannot induce failure by itself , we have shown that rods can break just because they are released. When a bent rod reaches its limit curvature and breaks at a first point, a burst of flexural waves is sent through the newly formed fragments, which locally further increase the curvature. The limit curvature is therefore exceeded again at later time, allowing a cascading failure mechanism to take place.