"Ed Huntress" wrote in message
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"charlie" wrote in message
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"Ed Huntress" wrote in message
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"Gunner" wrote in message
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On Sun, 24 Feb 2008 13:03:20 -0800 (PST), "
wrote:
On Feb 24, 4:54 am, wrote:
can anyone tell me that what is fludity in cast iron???should it be
more or less in c.i??
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"
this is incorrect. glass is classified as an amorphous solid.
http://en.wikipedia.org/wiki/Amorphous
Maybe why all those old lathes wont hold tolerance anymore. The cast
iron has flowed a bit.
G
Gunner
regards,
charlie
http://glassartists.org/chaniarts
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.
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.
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.
they were wrong.
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
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.
http://www.glasslinks.com/newsinfo/supercooled.htm
http://math.ucr.edu/home/baez/physic...ass/glass.html
"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
http://glassartists.org/chaniarts