cast iron

Do you want a definition of "fluidity" or a figure for CI? More or less that *what*? Steel? Pure iron?

Try Google:

Specifically - what did your teacher ask for?

-- Jeff R.

This is the time of year for that, isn't it?

Happens other times, but seems to be more often just before spring break.

Or I'm seeing things.

Mike

Isn't being "cast" meaning it is solid? So, there is no fluidity. Must be trick question on a final exam!

Paul

Glass is solid, yet its considered a "slow liquid"

Maybe why all those old lathes wont hold tolerance anymore. The cast iron has flowed a bit.

Gunner

I realize you're joking, but the creep properties of cast iron, combined with the structural design of a lathe, doesn't lend itself to significant distortions from "flow." Now, if the bed of a lathe is under stress from being poorly aligned over a period of years or decades, that might be different.

-- Ed Huntress

this is incorrect. glass is classified as an amorphous solid.

regards, charlie

There's some truth in both statements, Charlie. Amorphous solids -- non-crystalline solids -- have no distinct melting point. The definition of the "glass-transition" temperature, which is arbitrarily considered the temperature at which an amorphous material passes from solid to liquid, is just a viscosity number grabbed out of thin air.

So, to explain the behavior of glassy, or amorphous solids, teachers have often described glass, for example, as a "superliquid." The term has no precise meaning. It's just a handy description.

There are some 250-year-old windows in one of my family's houses that make a strong case that glass is liquid. They look like wavy gravy at their bottoms, and it's not a result of being blown as cylinders and then cut and flattened (which is, of course, the way they were made). They all get wavy at the same point, on the bottom side. You could say that they're just especially subject to creep, if you think of them as solid. Or you could say they're just a very, very viscous liquid.

-- Ed Huntress

did you read the link? it has nothing to do with the melting point. it has to do with the formation of crystals and the speed of cooling.

they were wrong.

that is also incorrect. your wavy windows did not creep. that again is an old wive's tale. your windows were made that way because the craftsmen of the time thought they would last longer with the wavy or thicker part down, or did it because of esthetics in your case as it would look odd to have the demarkation lines at different points in adjacent windows.

if this were true, then why aren't the glass objects the egyptians made 5000 years ago puddles in a museum about now?

there are articles that measure the creep or thickening of glass, and the time for this to occur to something you could see is longer than the age of the earth.

"The use of the term "supercooled liquid" to describe glass still persists, but is considered by many to be an unfortunate misnomer that should be avoided. In any case, claims that glass panes in old windows have deformed due to glass flow have never been substantiated. Examples of Roman glassware and calculations based on measurements of glass visco-properties indicate that these claims cannot be true. The observed features are more easily explained as a result of the imperfect methods used to make glass window panes before the float glass process was invented."

regards, charlie

Urban myth.

Wiki seemed to have missed this...

And you seemed to have missed the

You also seemed to have missed the

Tuesdays are Humor Impaired days?

Gunner

You know thats the trouble with science, they keep changing things. When I was in school (which was even farther back than when Gunner was) I'm pretty sure it was considered a "super cooled liquid" or some such description. :-) ...lew...

That was before global warming. Now they realize it's not really supercooled. a

-- Ed Huntress