After a machinist slips a hot, snugly fitting iron ring over a cold brass cylinder, the ring becomes "locked"

Question

in position and cant be removed even by subsequent heating. This procedure is called shrink fitting. HOw does it occur? Can u conclude anything about the thermal expansion rates of iron and brass?

Answer 1

It doesn't really have to do with the "different thermal expansion rates" of brass and iron. It has more to do with the fact that a ring of Any metal expands when heated and will have a larger diameter than when cold. Once you slide it over the cylinder and the temperatures equalize it is pretty much locked on and can only be removed with a hydraulic press or by cutting it off. This is because once it is on the cylinder you cannot just heat the outer ring without heating the cylinder as well.

If it were the result of different rates of expansion, in theory you could just reheat both and remove the ring.

Answer 2

No, you can't.

Even if both the ring and the cylinder were the same material, it would work. The inside diameter of the ring is simply smaller than the outside diameter of the cylinder, when they're both at the same temperature.

You may be able to unlock them by heating them both up, then chilling the cylinder but not the ring in liquid nitrogen. Since the heat is not instantly transfered through the system, there will be a period of time when the cylinder is colder than the ring. Conversely, you can heat the ring alone, with several wraps of nichrome wire, and get a temperature (and therefor size) differential.

Answer 3

I read this question rather halfheartedly, and for a second I thought you were being quite naughty.
Afraid I'm no good when It comes to the answer though. Other than the fact that iron will become smaller when it's cold, as when it is hot all the particles wiggle about and all that basic stuff.