Strength of Inorganic Glasses

Tim Dabbs: subthreshold indents

2011-11-03T08:10:00.000-07:00

I have recently obtained (courtesy of Brian Lawn and Robert Cook) a pdf copy of Tim's PhD thesis and have posted it on my web site: glass-fracture.org.
Tony Fisher-Cripps provided Tim's web site: (http://members.optusnet.com.au/timbaigl/dabbs.htm) but the email address listed there does not seem to work. If anyone has his email address please let me know.

Thanks,

Chuck
Since I originally posted the above, I learned that Tim's email has changed to: tdabbs@optusnet.com.au.

He has graciously provided a high resolution copy of his thesis and it has replaced the original I crude copy I had on my site. This is a very important piece of work. Although Tim published a lot of this, a lot has remained unpublished and is contained in the thesis.

Chuck

UGSC Research Strategy Workshop in Savannah, Georgia

2011-04-12T17:45:00.000-07:00

A meeting will be held in Savannah Georgia on Thursday and Friday, April14&15.

The purpose of the meeting is: " To enable the development of ultra-strong glass products through pre-competitive fundamental research on usable glass strength: to educate the next generation of glass researchers: and to develop the tools and measurement techniques essential for the advancement of glass science".

The results will be reported here.

email alerts!

2011-01-23T06:44:00.000-08:00

Some years ago I set up a website and a Blog to 'publicize' and share info about strength activities in glasses. While there is generally some traffic on the web site, there is little on the Blog. I have just posted a 'New Year's Greeting' and hope to see some activity result from that.
What I would like to do is to suggest that you each add 'Google reader' to you computers. This will allow email alerts when a new post appears on the Blog.
I will be sending you each a separate email to tell about this.

Chuck

2011-01-22T07:45:00.000-08:00

Chuck Kurkjian said...: Happy Holidays, etc.

For 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

2010-02-02T15:35:00.000-08:00

I have recently been made aware of three patents having to do with the lithium salts or lithium vapor treatment for strengthening. All of these apparently have to do with the change in coefficient of thermal expansion. In two of these patents, formation of low thermal expansion crystals on the surface is described while in the third one lithium vapor treatment results in lithium either being dissolved or exchanged into the surface, thereby producing a lower expansion surface layer.. These patents are listed below:

1. Dec 11, 1971. Anchor Hocking, Shonebarger, #3,615,319, Li enriched ‘shell’ is in compression.

2. Feb 23, 1988. Corning, Pierson, Stookey, #4,726,981, Li, xtln.

3. March 21, 1989. Corning, Beall, Pierson, Stookey, #4,814,297, Li xtln.

Ion exchange in glasses

2009-12-02T06:51:00.000-08:00

One question I have in mind for quite some time:

Ion exchange in glasses leads to higher strength, because literally speaking “bigger” ions are incorporated into the glass network and build up compressive stresses.

Has there ever been the idea of incorporating ions to induce a different coefficient of thermal expansion (CTE) which then, when cooling the glass, will lead to compressive stresses, because of different CTE between inner and outer of the glass?

2009-09-08T19:19:00.000-07:00

For some reason, I have not seen the Wikipedia site:'strength of glass' before tonight. I think it would be a good idea for us to contribute to it.

Chuck

2009-08-25T18:10:00.000-07:00

Inorganic glasses are one of the strongest known materials.

Strength of Inorganic Glasses

2009-08-25T17:34:00.000-07:00

The intrinsic inert strength of oxide glasses is among the highest of any known materials:

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.

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).