FILENAMES:

recdecrig.JPG
recdecwire.MPG

DESCRIPTION:

These files are a picture and a movie showing an experimental
apparatus demonstrating dimensional changes in steel as it
goes through its critical temperature transition.

Posted by Randy Zimmerman <rzimmerm@sprint.ca>. 

The following description was provided:

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Critical temperature demonstration:

        The setup is quite crude but is effective in showing the changing rate
of expansion and contraction when steel passes through the critical temperature.
The wire itself is a length of regular .035" diameter welding wire.
To control the rate that the wire heats a section of Nichrome wire was
salvaged from an old electric clothes drier.  It was cut to produce
approximately four ohms resistance.

	The affair is set on a length of one by four lumber with wood screws
as attachment points.  To tension the wire several rubber bands pull on
a piece of white doweling that serves as the pointer.

A piece of black plywood sits behind the pointer to increase visibility.

	The heating and cooling takes about thirty seconds total.  
The pointer will move as soon as current is applied and the wire starts expanding.
The pointer will hesitate as the wire reaches red heat. 
 When the current is removed the pointer returns rapidly, hesitates 
and actually indicates expansion before contracting down to room temperature.

	When you see the pointer moving to the right I have removed the current.
I am not reapplying it to the wire but you will see the pointer suddenly
stopping and moving to the left.

	The whole point of this demo is to reinforce the concept that the
steel actually undergoes a significant change at critical temp. 
That change from  body centered cubic to face centered cubic and back again
is a leap of faith until you see its effects.

	If there are any further questions regarding the construction
 of this little demo unit just e-mail me at rzimmerm@sprint.ca

Randy Zimmerman