Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
. Space Industry and Business News .




TECH SPACE
Modeling the breaking points of metallic glasses
by Staff Writers
Berkeley CA (SPX) Nov 27, 2012


A simulation of crack initiation in a metallic glass. The metallic glass on the left is initially more relaxed, due to a longer heat treatment, than the metallic glass on the right. The very different crack tip shapes and deformation patterns under the same external conditions result in a significantly reduced breaking resistance for the more relaxed glass. Credit: Courtesy of Christopher Rycroft, Berkeley Lab.

Metallic glass alloys (or liquid metals) are three times stronger than the best industrial steel, but can be molded into complex shapes with the same ease as plastic. These materials are highly resistant to scratching, denting, shattering and corrosion. So far, they have been used in a variety of products from golf clubs to aircraft components.

And, some smartphone manufacturers are even looking to cast their next-generation phone cases out of it. But despite their potential, the mechanical properties of these substances are still a scientific mystery. One lingering question is why they have such wildly different toughness and breaking points, depending on how they are made.

Although this may not be a huge concern for small applications like smartphone cases it will be extremely important if these materials are ever used in structural applications where they would need to support large loads.

Recently, Christopher Rycroft of the Lawrence Berkeley National Laboratory's (Berkeley Lab's) Computational Research Division has developed some novel computational techniques to address this question.

When Rycroft combined these techniques with a mechanical model of metallic glass developed by Eran Bouchbinder and his colleagues at Israel's Weizmann Institute, the two were able to propose a novel explanation of the physical process behind the large variations in breaking points of metallic glasses. Their results are also in qualitative agreement with laboratory experiments.

"We hope that this work will contribute to the understanding of metallic glasses, and aid in their use in practical applications. Ultimately, we would like to develop a tool capable of making quantitative predictions about the toughness of metallic glasses depending on their preparation method," says Rycroft.

What is a Metallic Glass? And, Why is it So Difficult to Model?

Scientists define "glass" as a material that cools from a liquid state to a solid state without crystallizing-which is when atoms settle into a lattice, or a highly regular spatial pattern.

Because many metal lattices are riddled with defects, these materials "deform", or permanently bend out of shape, relatively easily.

When crystallization does not occur, the atoms settle into a random arrangement. This atomic structure allows metallic glasses to spring back into shape instead of deforming permanently. And without the defects, some metallic glasses also have extremely efficient magnetic properties.

Rycroft notes that one of the biggest mysteries in condensed matter physics is how glass transitions from a liquid state to a solid state. To successfully create metallic glass, the metal has to cool relatively quickly before atomic lattices form.

"Depending on how you prepare or manipulate these metallic glasses, the breaking points can differ by a factor of 10," says Rycroft. "Because scientists don't completely understand how glass transitions from liquid to solid state, they have not been able to fully explain why the breaking points of these materials vary so widely."

According to Bouchbinder, computer models also have a hard time predicting the breaking points of metallic glass because the timescale of events varies dramatically-from microseconds to seconds.

For instance, researchers can bend or pull the material for several seconds before it breaks, which occurs almost instantaneously. And the material's internal plastic deformation-the process where it irreversibly deforms-occurs on an intermediate timescale.

"We've actually been able to develop some numerical methods to capture these differences in timescales," says Rycroft, of the techniques used in the recent paper.

When Rycroft incorporated these methods into Bouchbinder's mechanical model and calibrated it based on available data, the duo managed to simulate and better understand the breaking points of metallic glass alloys based on their preparation process.

He notes that this model is rather unique as it combines novel and flexible numerical methods with recent insights about the physics of glasses. The simulations have also been able to predict the large decreases in toughness that are seen in laboratory experiments.

"If you can vary the way metallic glass is prepared in computer models and capture the differences in how it breaks, you can pose a reasonable explanation for why this occurs. This might also give you a better idea about how the glass transitions from a liquid to a solid, as well as the mechanical properties of a glass," says Rycroft.

"We've essentially created something that might evolve into a tool for predicting the toughness of metallic glasses."

"For quite some time I've wanted to calculate the fracture toughness of metallic glasses, but knew that this was a very tough mathematical and computational challenge, certainly well above my abilities, and probably above the capabilities of conventional computational solid mechanics," says Bouchbinder.

"I think that Rycroft's methods have opened the way to new possibilities and I am enthusiastic to see where this can lead us."

Rycroft and Bouchbinder are co-authors on a paper recently published in Physical Review Letters.

.


Related Links
Lawrence Berkeley National Laboratory
Space Technology News - Applications and Research






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





TECH SPACE
New device hides, on cue, from infrared cameras
Boston MA (SPX) Nov 27, 2012
Now you see it, now you don't. A new device invented at the Harvard School of Engineering and Applied Sciences (SEAS) can absorb 99.75% of infrared light that shines on it. When activated, it appears black to infrared cameras. Composed of just a 180-nanometer-thick layer of vanadium dioxide (VO2) on top of a sheet of sapphire, the device reacts to temperature changes by reflecting dramatically m ... read more


TECH SPACE
Japan firm offers 3D model of foetus

Modeling the breaking points of metallic glasses

Putting more cores to work in server farms

New device hides, on cue, from infrared cameras

TECH SPACE
Lockheed Martin to Demonstrate Key Component of Tactical MilSat Communications System

The Skynet 5D secure telecom satellite is received in French Guiana for Arianespace's December Ariane 5 mission

Lockheed Martin Completes On Orbit Testing of Second AEHF Satellite

LynuxWorks LynxOS-SE Deployed by ITT Exelis in New Line of Software-Defined Radios

TECH SPACE
Failure Of India's Big Rocket Project Is Symbolic Of Deep Structural Problems

Russian Briz-M puts US satellite into orbit

Pleiades 1B is ready for integration in the payload "stack" for Arianespace's next Soyuz mission

France, Germany compromise on Ariane launcher: minister

TECH SPACE
East Riding Of Yorkshire Council Selects Ctrack For Specialist Vehicle Tracking Solution

Researchers Use GPS Tracking to Monitor Crab Behavior

US Navy, Raytheon receive Pentagon engineering award for GPS-guided precision landing program

Lockheed Martin Completes Critical Environmental Test on GPS III Pathfinder

TECH SPACE
French police fire tear gas anew on airport protest

Owls' ability to fly in acoustic stealth provides clues to mitigating conventional aircraft noise

China Eastern Airlines to buy 60 A320 aircraft

Mosquitos fail at flight in heavy fog

TECH SPACE
Engineers pave the way towards 3D printing of personal electronics

Antenna-on-a-chip rips the light fantastic

Fabrication on patterned silicon carbide produces bandgap to advance graphene electronics

Important progress for spintronics

TECH SPACE
China successfully launches remote sensing satellite

What lies beneath? New survey technique offers detailed picture of our changing landscape

How many Russian Earth observation satellites will be in orbit by 2015?

A SPOT 6 Success Story

TECH SPACE
Italian steel plant suspends operations in pollution row

Scientists pioneer method to predict environmental collapse

Degraded military lands to get ecological boost from CU-led effort

India's capital widens ban on plastic bags




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement