silica ~ 14 GPa
'window glass' - soda lime silica ~ 10 GPa.
The above is not commonly known or appreciated.
What is commonly known is that the 'practical', or commonly encountered strength of both of these glasses is ~ 50-70 MPa.
What is commonly known is that the 'practical', or commonly encountered strength of both of these glasses is ~ 50-70 MPa.
On the other hand, the now well-known lightguide fibers being installed in local telephone networks, does have and extremely high strength: ~5.5 GPa over MOST of its length.
It is clear that the reason for this enormous 'discrepancy' is that at some point, the glass surface has been 'mechanically damaged'.
Our task is then 3-fold:
1. Understand the fundamental parameters (composition, etc.) that control the inert intrinsic strength.
2. Understand the factors that influence the susceptibility or resistance to mechanical damge (composition, etc.).
3. Understand/develop techniques to 'protect' the glass surface from this mechanical damage (coatings, chemical and thermal tempering, cladding, lamination).
Happy Holidays, etc.
ReplyDeleteFor me 2010 has been a relatively productive year. In addition to general research initiatives and collaborations relating to strength, indentation behavior and stresses in glasses, activities with GMIC have been productive.
The 'UGSC' is in the process of setting up! This is the 'Usable Glass Strength Consortium'. For more information about this, please go to: gmic.org and more specifically to: http://www.gmic.org/Strength%20In%20Glass.html.
I would encourage all of you to become involved with this. Although it was started by the GMIC in the U.S, it is clearly meant to be an international effort. Have a look and see what part you can play!!!
In research terms, the setting up of the Abrio stress birefringence instrument with Prof. Satoshi Yoshida (in Shiga, Japan) and his student Sohtaro Iwata has been a landmark. Already very important results on ball indentations have been obtained. It is hoped that these studies will be extended to include the effects of coatings and surface stresses and surface condition on ball indentation stresses.
The more general activities of the year are indicated on my web site: glass-fracture.org.
Additional collaborations with Prof.S. Chandrasekar and Dr. Narayan Sundaram at Purdue University related to contact stress calculations as well as other experimental studies related to surface damage have been initiated this year and are being actively pursued.
I encourage all of you to take an active part in the building of this blog into a useful 'information exchange' medium.
Happy New Year.
Chuck