Glass is linear elastic and therefore the general rules of brittle materials
is followed.  The material has a number of imperfections: single dimension
point defects, two dimensional linear defects and three dimensional defects.
At any given time the population of flaws are sub critical, material will
last "forever".  Failure occurs when the first sub critical flaw grows to
critical dimensions.

Fracture mechanics and all that materials science stuff.  Generally need to
do material specific test because of the thin dimension and linear elastic
properties with crystallographic orientation or texture if amorphous.  Don't
even try to calculate it.  More realistic is to take a piece of your
material  2x2" to a micro hardness test machine with a diamond indenter.
Indent your glass with ever increasing load and measure the crack tip
length.  Repeat this process until the piece fails. The last measured crack
length is your critical flaw size.  You should repeat this a number of times
because of material variation and your laboratory skills.
Rob

-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org]On
Behalf Of pik
Sent: Saturday, May 03, 2003 1:32 PM
To: mems-talk@memsnet.org
Subject: [mems-talk] Flaws size in cracked glass.


Does anyone know the width range of  flaws in cracked
glass?
Thank you
Adi Lev
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