. 24/7 Space News .
NANO TECH
Researchers show how nanoscale patterning can decrease metal fatigue
by Staff Writers
Providence RI (SPX) Nov 02, 2017


Researchers performed fatigue tests on 5mm samples of nanotwinned copper (top image). Electron microscope images show that the microstructure of the material before the tests (images b and c) were preserved after 17,000 loading cycles (e and f). The results show that nanotwinned can be far more resistant to fatigue than standard metals

A new study in the journal Nature shows how metals can be patterned at the nanoscale to be more resistant to fatigue, the slow accumulation of internal damage from repetitive strain.

The research focused on metal manufactured with nanotwins, tiny linear boundaries in a metal's atomic lattice that have identical crystalline structures on either side. The study showed that nantowins help to stabilize defects associated with repetitive strain that arise at the atomic level and limit the accumulation of fatigue-related damage.

"Ninety percent of failure in metal components and engineering structures is through fatigue," said Huajian Gao, a professor in Brown University's School of Engineering and corresponding author of the new research. "This work represents a potential path to more fatigue-resistant metals, which would useful in nearly every engineering setting."

Gao co-authored the study with Haofei Zhou, a postdoctoral researcher at Brown, along with Quingson Pan, Qiuhong Lu and Lei Lu from the Chinese Academy of Science.

To study the fatigue effects of nanotwins, the researchers electroplated bulk samples of copper with closely spaced twin structures within the plates' crystalline grains. Then they performed a series of experiments in which they stretched and compressed the plates repeatedly at different amplitudes of strain and measured the material's associated stress response using a fatigue testing system. Beginning with a strain amplitude of .02 percent, the researchers progressively increased the amplitude every 1,500 cycles to .04, then .06, finally peaking at .09 before stepping back down through the strain amplitudes.

The tests showed that the stress response of the nanotwinned copper quickly stabilized at each strain amplitude. More importantly, Gao said, the study found that the stress response at each strain amplitude was the same during the second half of the experiment, when the metal was cycled through each strain amplitude a second time. That means the material did not harden or soften under the strain as most metals would be expected to do.

"Despite having already been through thousands of strain cycles, the material showed the same stress response," Gao said. "That tells us that the reaction to cyclic strain is history-independent - the damage doesn't accumulate the way it does in common materials."

For comparison, the researchers performed similar experiments on non-nanotwinned samples, which showed significant hardening and softening (depending on the material) and displayed the type of cumulative fatigue effects that are common in most metals.

To understand the mechanism behind this fatigue resistance, the researchers performed supercomputer simulations of the metal's atomic structure. At the atomic level, material deformation manifests itself through the motion of dislocations - line defects in the crystalline structure where atoms are pushed out of place.

The simulations showed that the nanotwin structures organize strain-related dislocations into linear bands called correlated necklace dislocations (named for their beaded-necklace-like appearance in simulation). Within each crystal grain, the dislocations remain parallel to each other and don't block each other's motion, which is why the effects of the dislocations are reversible, Gao says.

"In a normal material, fatigue damage accumulates because dislocations get tangled up with each other and can't be undone," he said. "In the twinned metal, the correlated necklace dislocations are highly organized and stable. So when the strain is relaxed, the dislocations simply retreat and there's no accumulated damage to the nanotwin structure."

The metals aren't entirely immune to fatigue, however. The fatigue resistance demonstrated in the study is within each crystalline grain. There's still damage that accumulates at the boundaries between grains. But the within-grain resistance to fatigue "slows down the degradation process, so the structure has a much longer fatigue life," Gao said.

Gao's research group has worked extensively on nanotwinned metals, previously showing that nanotwin structures can improve a metal's strength - the ability to resist deformation such as bending - and ductility, the ability to stretch without breaking. This new finding suggests yet another advantage to twinned metals. He and his colleagues hope this latest research will encourage manufacturers to find new ways of creating nanotwins in metals.

The electroplating method used to fabricate the copper for this study isn't practical for making large components. And while there are some forms of twinned metal available now (twinning-induced plasticity or "TWIP" steel is an example), scientists are still looking for cheap and efficient ways to make metals and alloys with twin structures.

"It's still more of an art than a science, and we haven't mastered it yet," said Lu, one of the corresponding authors from Chinese Academy of Sciences. "We hope that if we point out the benefits you can get from twinning, it might stimulate fabrication experts to find new alloys that will twin easily."

Research paper

NANO TECH
New technique produces tunable, nanoporous materials
Chicago IL (SPX) Oct 30, 2017
A collaborative group of researchers including Petr Kral, professor of chemistry at the University of Illinois at Chicago, describe a new technique for creating novel nanoporous materials with unique properties that can be used to filter molecules or light. They describe their research in the journal Science. Nanoparticles are tiny particles made up of a central solid core to which molecul ... read more

Related Links
Brown University
Nano Technology News From SpaceMart.com
Computer Chip Architecture, Technology and Manufacture


Thanks for being there;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Monthly Supporter
$5+ Billed Monthly


paypal only
SpaceDaily Contributor
$5 Billed Once


credit card or paypal


Comment using your Disqus, Facebook, Google or Twitter login.

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

NANO TECH
Pope asks spacemen life's big questions in ISS live chat

Plants and psychological well-being in space

Spacewalkers fix robotic arm in time to grab next cargo ship

NASA develops and tests new housing for in-orbit science payloads

NANO TECH
Thruster for Mars mission breaks records

Draper and Sierra Nevada Corporation announce new agreement for space missions

Aerojet Rocketdyne breaks ground on advanced manufacturing center in Huntsville

New solid rocket motor development facility completed at Spaceport America

NANO TECH
Mars Rover Mission Progresses Toward Resumed Drilling

Solar eruptions could electrify Martian moons

MAVEN finds Mars has a twisted tail

Mine craft for Mars

NANO TECH
Space will see Communist loyalty: Chinese astronaut

China launches three satellites

Mars probe to carry 13 types of payload on 2020 mission

UN official commends China's role in space cooperation

NANO TECH
Myanmar to launch own satellite system-2 in 2019: vice president

Eutelsat's Airbus-built full electric EUTELSAT 172B satellite reaches geostationary orbit

Turkey, Russia to Enhance Cooperation in the Field of Space Technologies

SpaceX launches 10 satellites for Iridium mobile network

NANO TECH
Turning a material upside down can sometimes make it softer

Nanoscale textures make glass invisible

Discovery of a new structure family of oxide-ion conductors SrYbInO4

Technique offers advance in testing micro-scale compressive strength of cement

NANO TECH
Comet mission reveals 'missing link' in our understanding of planet formation

Astronomers discover sunscreen snow falling on hot exoplanet

Marine microbes living beneath seabed resort to cannibalism

New NASA study improves search for habitable worlds

NANO TECH
Haumea, the most peculiar of Pluto companions, has a ring around it

Ring around a dwarf planet detected

Helicopter test for Jupiter icy moons radar

Solving the Mystery of Pluto's Giant Blades of Ice









The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news 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. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. 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. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.