> What do you mean by "metals don't actually withstand temperature"? As in the raw metal would melt were it not for the cooling vanes?
They creep. Have you seen, for instance, Blu-tac or glue fail? It doesn't go at once, but slowly, over a period of time. At high temperatures most metals (others on this thread have mentioned single-crystal blades) behave a bit like that.
Although steel is also weaker at temperatures far below its melting point, yes. A simple observation of a blacksmith at work should tell you that. And a think some new jets may be running hotter than Tm for steel now?
> The lower power setting on shutdown does what? Spin it at a low RPM so it doesn't decrease in temp too quickly?
Yup, or more relevantly evenly, although those tend to be related. Given almost all materials expand as they get hotter and contract as they cool, different cooling rates between parts -> different contraction rates -> different relative shape -> Very Bad in precision machinery.
So basically metal gets rubbery when hot, and stopping something all off a sudden could have inertial forces(moving blades, gears etc) wreck the structure?
You have to shut things down step by step, so that rigidity is supplied to the metals as the inertial forces are reduced.
They creep. Have you seen, for instance, Blu-tac or glue fail? It doesn't go at once, but slowly, over a period of time. At high temperatures most metals (others on this thread have mentioned single-crystal blades) behave a bit like that.
Although steel is also weaker at temperatures far below its melting point, yes. A simple observation of a blacksmith at work should tell you that. And a think some new jets may be running hotter than Tm for steel now?
> The lower power setting on shutdown does what? Spin it at a low RPM so it doesn't decrease in temp too quickly?
Yup, or more relevantly evenly, although those tend to be related. Given almost all materials expand as they get hotter and contract as they cool, different cooling rates between parts -> different contraction rates -> different relative shape -> Very Bad in precision machinery.