Question about heating metal

[Usr117063]

When heating up a casing for a bearing, why doesnt the metal expand inward, decreasing space?

 

[Djw John]

Science

 

[Crayola]

Witchcraft

 

[Usr117063]

What happens if you cool the casing?

 

[Crayola]

It gets colder

 

[Usr117063]

 

[R3k1355]

It gets smaller.

You can shove some types of bearings in the freezer overnight, the contract slightly and slip on in with little fuss.

 

[J-J]

It will be because of the pressure exerted on itself. To expand inwards requires it to press against itself, whilst to expand outwards will allow it to move into free space.

 

[Andy_con]

Magic!

It expands in all directions, not just an outwards direction

 

[alistairolsen]

Think of it as a ring, and imagine the material expanding axially to become longer, rather than radially to become wider or of larger cross section.

 

[dann2707]

Think of it as a ring, and imagine the material expanding axially to become longer, rather than radially to become wider or of larger cross section.

That doesn't answer the question though?

 

[DrR]

The casing gets bigger when it’s heated, so why would the hole get smaller?

 

[Louis]

It expands with heating because of the cte, if it went inwards then it's actually contracting, which only happens when cooled

 

[Usr117063]

So when you heat it, it goes outward both ways and not inward. When you cool it, it goes inward both ways. But its both increasing in size and shrinking at the same time right?

 

[Louis]

So when you heat it, it goes outward both ways and not inward. When you cool it, it goes inward both ways. But its both increasing in size and shrinking at the same time right?

View attachment 1539356

No, it's not increasing and shrinking at the same time.

Temperature and thermal expansion

 

[Usr117063]

No, it's not increasing and shrinking?

Picture on left which is what happens when you heat it right? You are 'gaining' size in the outer and 'losing' size in the inner part. Because what I dont get is you heat the part and you are not heating the whole casing just where the bearing seats, 'it gets bigger' for the bearing, but the casing would be losing its total size ever so slightly (the casing gets smaller by heating)

 

[Pistachio]

Imagine you have two doughnuts and you slice them up like a pizza. You take a slice from doughnut B and add it to doughnut A so that it has an extra doughnut slice.

Both the inner and outer circles of the doughnut have increased in diameter. Because they are hotter and have expanded

You also then have 5 unused doughnut pieces to eat. Which are not hot.



It's pretty simple stuff really

 

[Usr117063]

You would probably heat just the red circle area. Surely the whole casing wouldnt expand as the outer part is not getting hot at all. So the the inner point to the outer point (black arrow) is getting smaller.

 

[Louis]

You would probably heat just the red circle area. Surely the whole casing wouldnt expand as the outer part is not getting hot at all. So the the inner point to the outer point (black arrow) is getting smaller.

View attachment 1539358

The heat will transfer through the casing a lot. Then you have the different CTE between the metals. It cant contract with temperature, it just wont expand as much if the outer isnt able to move (not as hot).

 

[Usr117063]

The heat will transfer through the casing a lot. Then you have the different CTE between the metals. It cant contract with temperature, it just wont expand as much if the outer isnt able to move (not as hot).

If the heat does transfer a lot then that explains it.