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Re: cold weld between polished surfaces



There is nice modelling and STM work done on this. As an ex-surface
science person I would say too things.
First if the surfaces are really clear, I would guess a couple of
molecular vibrations, so less then feptoseconds.
Second, if this is a real case the statement "smooth and free of
contaminants" is essentially impossible to achieve.

Regarding the smooth issue, if you measure smoothness by considering the
range of surface heights divided by the scale of the object, the earth
is smoother than a billiard ball. Regarding contaminate free, at a
microTorr, a monolayer of contaminate will form on a metal surface in a
microsecond. You can scale what will happen at lower pressures.

cheers,

joe

On
Wed, 29 Sep 2004, Stephens, Kenny wrote:

What are the list-members' opinions on the rate at which two
highly-polished metal surfaces will cold weld to each other. Take the
surfaces to be smooth and free of contaminants. What time frame is
required for the surfaces to bond sufficiently well that when placed
under tension a fracture occurs NOT at the weld joint?

I was asked and could not confidently state a time frame. Any
constructive thoughts are appreciated.

Kenny Stephens
kstephens@hsutx.edu


Joseph J. Bellina, Jr. 574-284-4662
Professor of Physics
Saint Mary's College
Notre Dame, IN 46556