Featured Research

from universities, journals, and other organizations

Engineered Glass Tempering Halts Cracks

Date:
February 26, 1999
Source:
Penn State
Summary:
Few things are as fragile as glass, and if a Penn State researcher has his way, some types of glass will be less fragile.

University Park, Pa. --- Few things are as fragile as glass, and if a Penn State researcher has his way, some types of glass will be less fragile.

"Chemical and heat tempered glasses have been around for a long time," says Dr. David J. Green, professor of ceramic science and engineering. "These glasses can withstand more stress before breaking than untreated glass, but when they break, they usually break catastrophically."

Another problem with chemical and heat tempered glass is that while each individual piece of glass becomes stronger, the variability of strength between pieces of glass increases dramatically. Engineers choosing glass for specific purposes must account for this wider range of strengths.

Working with Dr. R. Tandon of Caterpillar Inc., in Peoria, Illinois, and V.M. Sglavo of the University of Trento, Italy, Green developed a theoretical approach to designing strengthened glass. The team reported their work in today's (Feb. 26) issue of the journal Science.

Conventional tempering of glass alters the outer surface of the glass so that it is under compression. Glass under compression can withstand higher levels of stress before reaching the failure point.

"Rather than simply altering the outside layer of glass, we would like to engineer the glass so that it has a specific compression profile making the final product stronger and less variable," says Green, a faculty member in the College of Earth and Mineral Sciences.

The researchers tested their theory using the chemical tempering process on sodium aluminosilicate glass, but believe that they could adapt the process to other tempering processes and other materials.

In chemical tempering, potassium atoms are often used to replace some of the sodium atoms near the surface. These potassium atoms are slightly larger than the sodium atoms and they compress the layer in which they are substituted by crowding the other atoms. Chemical tempering usually occurs in the outer millimeter of the pane of glass.

"If we place the maximum compression layer beneath the surface, when cracks propagate from the flaws on the surface, they reach the layer and stop," says Green.

The researchers created these internal compressed layers by subjecting the glass to chemical processing where potassium substituted for sodium, but then exchanged some of the potassium near the surface back to sodium. This created glass with an untempered surface, but with a tempered, compressed layer below.

"Unexpectedly, glass made in this way exhibits multiple cracking," says Green. "Unlike untreated glass or conventionally tempered glass where a crack that begins progresses rapidly to catastrophic failure, small cracks begin to form in the untempered layer and then the cracks are arrested by the compressed layer."

Many cracks may form before the ultimate crack that propagates through the compressed layer and shatters the glass. This surface crazing can be used as a warning that the glass is approaching its breaking point and needs to be replaced. Creating glass that will only break at a certain, predetermined stress level may also be possible.

"The strength range of a batch of conventionally tempered glass may be as broad as 25 percent on either side of the average strength," Green says. "However, the specially designed glass we are looking at has a range of only 6 percent on either side of the average." This smaller range provides more consistency when manufacturing the glass.

Chemically tempered glass is used in eyeglasses and sunglasses and thermally tempered glass is used in automobile windshields. This new tempering method could allow thinner glass to be used in such things as photocopying machines, scanners and electronic displays that would make them stronger and lighter. Eventually, glasses could be designed with specific strengths and a higher reliability.


Story Source:

The above story is based on materials provided by Penn State. Note: Materials may be edited for content and length.


Cite This Page:

Penn State. "Engineered Glass Tempering Halts Cracks." ScienceDaily. ScienceDaily, 26 February 1999. <www.sciencedaily.com/releases/1999/02/990226075422.htm>.
Penn State. (1999, February 26). Engineered Glass Tempering Halts Cracks. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/1999/02/990226075422.htm
Penn State. "Engineered Glass Tempering Halts Cracks." ScienceDaily. www.sciencedaily.com/releases/1999/02/990226075422.htm (accessed July 31, 2014).

Share This




More Matter & Energy News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Britain Testing Driverless Cars on Roadways

Britain Testing Driverless Cars on Roadways

AP (July 30, 2014) British officials said on Wednesday that driverless cars will be tested on roads in as many as three cities in a trial program set to begin in January. Officials said the tests will last up to three years. (July 30) Video provided by AP
Powered by NewsLook.com
7 Ways to Use Toothpaste: Howdini Hacks

7 Ways to Use Toothpaste: Howdini Hacks

Howdini (July 30, 2014) Fresh breath and clean teeth are great, but have you ever thought, "my toothpaste could be doing more". Well, it can! Lots of things! Howdini has 7 new uses for this household staple. Video provided by Howdini
Powered by NewsLook.com
Amid Drought, UCLA Sees Only Water

Amid Drought, UCLA Sees Only Water

AP (July 30, 2014) A ruptured 93-year-old water main left the UCLA campus awash in 8 million gallons of water in the middle of California's worst drought in decades. (July 30) Video provided by AP
Powered by NewsLook.com
Smartphone Powered Paper Plane Debuts at Airshow

Smartphone Powered Paper Plane Debuts at Airshow

AP (July 30, 2014) Smartphone powered paper airplane that was popular on crowdfunding website KickStarter makes its debut at Wisconsin airshow (July 30) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



    Save/Print:
    Share:

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile: iPhone Android Web
    Follow: Facebook Twitter Google+
    Subscribe: RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins