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rotate
06-24-2010, 01:58 PM
I've been told that when you heat sheet metal, the metal expands but shrinks to smaller size than normal when it cools down. What's the physics behind this?

I don't actually have a good understanding of shrinking and stretching of sheet metal, not in terms of how it's done or the technique but rather the science behind it. Does someone have a good link or literature that I can refer to? Thanks.

ptjw7uk
06-24-2010, 05:34 PM
Try this, gives a reasonable explanation
http://books.google.co.uk/books?id=YoVvcgyCA9UC&pg=PA364&lpg=PA364&dq=hot+shrinking&source=bl&ots=lhlBE24WXJ&sig=VI5aK117Iol7_wJeuYOX_eoMzZE&hl=en&ei=e84jTKbNDJPy0gS9idnsBA&sa=X&oi=book_result&ct=result&resnum=3&ved=0CBsQ6AEwAg#v=onepage&q=hot%20shrinking&f=false

Peter

strokersix
06-24-2010, 05:49 PM
I think of it this way: The heat causes localized expansion. This expansion constrained by the surrounding material results in localized yield. Then when the material cools the yielded volume contracts and shrinks.

I've seen photos of this effect used for intentionally curving or repairing damaged structural steel using just heat.

RancherBill
06-24-2010, 07:06 PM
YouTube video showing the effect.

http://www.youtube.com/watch?v=ILVWPzO_swY