. 24/7 Space News .
Army researchers develop new method for analyzing metal
by Staff Writers
Adelphi MD (SPX) Feb 17, 2020

An infrared camera captures thermographic data of the ball-on-disk tribometer with labels indicating the locations of the (a) optical microscope objective, (b) disk thermocouple, and (c) ball thermocouple.

Warfighters on the battlefield often rely on machines, vehicles and other technologies with rotating parts to complete their mission. Army researchers have devised a new method of testing for a major factor in equipment failure and breakdown in order to ensure that those tools meet the proper standard of quality.

When mechanical parts slide against each other for long periods of time, the constant grinding may wear down the metal surfaces until the parts are no longer functional. The study of friction, wear and lubrication as two or more surfaces interact in relative motion is known as tribology, and its importance in material science and engineering has led researchers to find new ways to examine dry mechanical contact.

Researchers at the U.S. Army Combat Capabilities Development Command's Army Research Laboratory recently developed a new approach to analyze the tribological response between steel and silicon nitride that takes place as the two metals interact, rather than after the samples have cooled off.

This latest method of studying wear and tear may allow researchers to observe fleeting chemical reactions that occur at the contact site.

"The mechanical system is very dynamic during operation," said Dr. Stephen Berkebile, Army research physicist. "If it is not captured during operation and, instead, measured when not moving quickly, the transient chemical reactions and physical changes would not be captured since the system may change after cooling down from the frictional heating."

Berkebile acted as one of the Army researchers working together with the University of North Texas to study the sliding interaction between steel and silicon nitride. More specifically, the team was trying to investigate why increasing the sliding speed between steel and silicon nitride decreased their rate of friction and wear as they made contact.

According to the researchers, the interaction between steel and silicon nitride is one that commonly takes place during the dry machining process of certain cutting tools and in emergency situations with high speed bearings when they lose their lubrication source, like those in jet engine turbines. Understanding the kinetics behind the high-speed sliding contact between these two metals would be vital in developing better and safer vehicles and equipment for Soldiers.

"Hybrid bearings with the steel/silicon nitride contact are increasingly being used in turbomachinery within helicopter propulsion systems," Berkebile said. "Such hybrid bearings are finding more and more use in rotorcraft and helicopter propulsion systems where they are operated at high speeds."

The researchers conducted the experiment using a Ball on Disk tribometer that slid a rolling silicon nitride ball against a steel rotating disk that was heated to 120 degrees Celsius with a hot plate underneath.

A stereo-optical microscope with a color Charge-Coupled Device, or CCD, camera and an infrared camera obtained thermal imaging data as the rotating speed of the disk sped up from 1 m/s to 16 m/s. Afterwards, the researchers conducted an analysis of the wear tracks using a backscatter electron detector that mapped the elemental composition of the leftover film residue.

"By combining two optical methods with real-time friction data, we could understand the chemical transition in the wear mechanism," Berkebile said. "We were able to correlate the friction, temperature and chemical state of the mechanical contact during active operation of the experiment as the chemical reaction was occurring."

According to the researchers, this experiment represented the first known attempt to analyze the tribological response of steel and silicon nitride in the middle of a high sliding speed test.

Furthermore, the data resulting from this bold venture provided new information about the nature of tribological effects that took place.

The team discovered that the frictional heating caused at a threshold sliding speed of around 4.5 m/s induced a chemical reaction that left behind a lubricating thin film at the highly loaded contact zone.

This slippery thin film was what allowed the mechanical interaction between steel and silicon nitride to demonstrate lower friction and wear as the sliding speed increased. Using the new approach, the team managed to pinpoint the exact time that the chemical reaction occurred from observations of the wear tracks' color change during the experiment.

Additionally, the researchers determined that this phenomenon is fully active when the sliding speed rose above 9 m/s under gear- and bearing-like conditions.

Based on the analysis of the wear tracks, the researchers verified that a series of oxidation reactions must have taken place as a result of the interplay between iron, oxygen and silicon under high temperatures from frictional heating.

"We found that a smooth transition between one chemical reaction to another occurs during the transition between the low friction and wear state and the high friction and wear state," Berkebile said. "The chemical reaction also requires frictional heating to be maintained, and thus can 'extinguish' itself after a few seconds if the low friction state is achieved and the frictional heating is reduced at intermediate speeds."

According to Berkebile, this new in-situ approach to examining dry sliding mechanical contacts holds the potential to significantly improve the Army's efforts to develop machinery that can better withstand high temperatures, loads and speeds.

"Army helicopters have a requirement to operate for 30 minutes after lubrication has been lost from the drive system," Berkebile said. "From this study, we have learned that for drive systems that contain hybrid components, such as silicon nitride/steel bearings, the materials may actually last longer if they are sliding at a higher rather than lower speed, which is really counterintuitive."

Research paper

Related Links
US Army Research Laboratory
Space Technology News - Applications and Research

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

In Norway, bottles made of plastic are still fantastic
Fetsund, Norvege (AFP) Feb 13, 2020
One at a time, the elderly lady places her empties into the gaping hole of a machine at the entrance to an Oslo supermarket. With a well-functioning deposit system, Norway recycles almost all of its plastic bottles. "You have to get rid of them, so you may as well do it intelligently," says the woman in her 70s, as the machine spits out a bar-code ticket that entitles her to around 30 kroner (three euros, $3.25) either in cash or credit at the till. With its 97 percent recycling rate, Norway is ... read more

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

Space station to forge ultra-fast connections

Software defects could have destroyed Boeing Starliner on test flight

The science behind and beyond Luca's mission

Record-Setting NASA Astronaut, Crewmates Return from Space Station

India, Russia Agree to Develop Advanced Ignition Systems to Propel Futuristic Rockets, Missiles

Aerojet Rocketdyne delivers RL10 engines that will help send NASA astronauts to deep space

Changing the way NASA keeps it cool

Rocket Lab successfully launches U.S. spy satellite

MAVEN explores Mars to understand radio interference at Earth

Mars' water was mineral-rich and salty

Russian scientists propose manned Base on Martian Moon to control robots remotely on red planet

To infinity and beyond: interstellar lab unveils space-inspired village for future Mars settlement

China's Long March-5B carrier rocket arrives at launch site

China to launch more space science satellites

China's space station core module, manned spacecraft arrive at launch site

China to launch Mars probe in July

Arianespace and Starsem launch 34 OneWeb satellites to help bridge the digital divide

RUAG Space dispenses another batch of Airbus OneWeb satellites

Azercosmos and Infostellar to enter into Ground Station Partnership

OneWeb lifts off: Next batch ready to launch

New threads: Nanowires made of tellurium and nanotubes hold promise for wearable tech

In Norway, bottles made of plastic are still fantastic

Fastest high-precision 3D printer

First time controlling two spacecraft with one dish

CHEOPS space telescope takes its first pictures

NASA's Webb will seek atmospheres around potentially habitable exoplanets

To make amino acids, just add electricity

AI could deceive us as much as the human eye does in the search for extraterrestrials

Pluto's icy heart makes winds blow

Why Uranus and Neptune are different

Seeing stars in 3D: The New Horizons Parallax Program

Looking back at a New Horizons New Year's to remember

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.