[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Cracking Glass

Ken Whelan said:

> The physics of cracking glass is easy. 
> Stress is defined as Force/Area.    At the end of the spreading
> crack,  the
> area at the tip of the crack approaches zero.   This means that the
> stress
> at that point of that fracture is approaching infinity.  Stress =
> Force/.0001 (or whatever the area is).  This means the stress goes
> very
> high.
> This means that it takes very little force at around the tip of the
> crack to
> make it spread.  That force can be induced by a unlevel aquarium,  
> the
> weight of the water,  stresses induced at assembly or many other
> things.
> Once that crack starts(or nick or whatever) it isn't going to stop by
> itself.
> Now my terminology is almost certainly incorrect,  (don't remember
> the
> correct terms for stress and force) the theory is what I was taught
> in a
> physics class long long ago.

Certainly part of the story but there must be more.  This helps explain
why, for example, plexiglass/lucite type acrylic and most glass can be
"cut" by scoring it and then applying stress along the crack.  But you
can stress the heck out of polycarbonate or metal after scoring it and
you will need different expectations.  The structure of the material
plays a critical role in the behavior and something about glass let's a
small subscopic defect in the surface of an aquarium turn into a very
wet floor beneath the aquarium. :-\

Scott H.

Do You Yahoo!?
Yahoo! Tax Center - online filing with TurboTax