Subscribe free to our newsletters via your
. Space Industry and Business News .




TECH SPACE
An efficient method to measure residual stress in 3D printed parts
by Staff Writers
Livermore CA (SPX) Nov 17, 2014


Amanda Wu images an additively manufactured part using digital image correlation. Image courtesy Julie Russell and LLNL.

Lawrence Livermore National Laboratory researchers have developed an efficient method to measure residual stress in metal parts produced by powder-bed fusion additive manufacturing.

This 3D printing process produces metal parts layer by layer using a high-energy laser beam to fuse metal powder particles. When each layer is complete, the build platform moves downward by the thickness of one layer, and a new powder layer is spread on the previous layer.

While this process is able to produce quality parts and components, residual stress is a major problem during the fabrication process. That's because large temperature changes near the last melt spot -- rapid heating and cooling -- and the repetition of this process result in localized expansion and contraction, factors that cause residual stress.

Aside from their potential impact on mechanical performance and structural integrity, residual stress may cause distortions during processing resulting in a loss of net shape, detachment from support structures and, potentially, the failure of additively manufactured (AM) parts and components.

An LLNL research team, led by engineer Amanda Wu, has developed an accurate residual stress measurement method that combines traditional stress-relieving methods (destructive analysis) with modern technology: digital image correlation (DIC). This process is able to provide fast and accurate measurements of surface-level residual stresses in AM parts.

The team used DIC to produce a set of quantified residual stress data for AM, exploring laser parameters. DIC is a cost-effective, image analysis method in which a dual camera setup is used to photograph an AM part once before it's removed from the build plate for analysis and once after. The part is imaged, removed and then re-imaged to measure the external residual stress.

In a part with no residual stresses, the two sections should fit together perfectly and no surface distortion will occur. In AM parts, residual stresses cause the parts to distort close to the cut interface.

The deformation is measured by digitally comparing images of the parts or components before and after removal. A black and white speckle pattern is applied to the AM parts so that the images can be fed into a software program that produces digital illustrations of high to low distortion areas on the part's surface.

In order to validate their results from DIC, the team collaborated with Los Alamos National Laboratory (LANL) to perform residual stress tests using a method known as neutron diffraction (ND).

This technique, performed by LANL researcher Donald Brown, measures residual stresses deep within a material by detecting the diffraction of an incident neutron beam. The diffracted beam of neutrons enables the detection of changes in atomic lattice spacing due to stress.

Although it's highly accurate, ND is rarely used to measure residual stress because there are only three federal research labs in the U.S. -- LANL being one of them -- that have the high-energy neutron source required for this analysis.

The LLNL team's DIC results were validated by the ND experiments, showing that DIC is a reliable way to measure residual stress in powder-bed fusion AM parts.

Their findings were the first to provide quantitative data showing internal residual stress distributions in AM parts as a function of laser power and speed. The team demonstrated that reducing the laser scan vector length instead of using a continuous laser scan regulates temperature changes during processing to reduce residual stress.

Furthermore, the results show that rotating the laser scan vector relative to the AM part's largest dimension also helps reduce residual stress. The team's results confirm qualitative data from other researchers that reached the same conclusion.

By using DIC, the team was able to produce reliable quantitative data that will enable AM researchers to optimally calibrate process parameters to reduce residual stress during fabrication. Laser settings (power and speed) and scanning parameters (pattern, orientation angle and overlaps) can be adjusted to produce more reliable parts.

Furthermore, DIC allowed the Lawrence Livermore team to evaluate the coupled effects of laser power and speed, and to observe a potentially beneficial effect of subsurface layer heating on residual stress development.

"We took time to do a systematic study of residual stresses that allowed us to measure things that were not quantified before," Wu said. "Being able to calibrate our AM parameters for residual stress minimization is critical."

LLNL's findings eventually will be used to help qualify properties of metal parts built using the powder-bed fusion AM process. The team's research helps build on other qualification processes designed at LLNL to improve quality and performance of 3D printed parts and components.


Thanks for being here;
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 Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

.


Related Links
Lawrence Livermore 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 Process Isolates Promising Material
Evanston IL (SPX) Nov 14, 2014
After graphene was first produced in the lab in 2004, thousands of laboratories began developing graphene products worldwide. Researchers were amazed by its lightweight and ultra-strong properties. Ten years later, scientists now search for other materials that have the same level of potential. "We continue to work with graphene, and there are some applications where it works very well," s ... read more


TECH SPACE
Cloaking device hides across continuous range of angles

A new approach to the delivery of satellites to orbit

An efficient method to measure residual stress in 3D printed parts

Boeing Stacks Two Satellites to Launch as a Pair

TECH SPACE
Harris Corporation supplying Falcon III radios to Canadian military

GenDyn Canada contracted to connect military to WGS system

Northrop Grumman continues Joint STARS sustainment services

Harris Corporation opens engineering support facility

TECH SPACE
Elon Musk unveils 'drone ship' and 'x-wing' fins for rockets via Twitter

China launches Yaogan-24 remote sensing satellite

Soyuz Installed at Baikonur, Expected to Launch Wednesday

Time-lapse video shows Orion's move to Cape Canaveral launch pad

TECH SPACE
Russia to place global navigation stations in China

Telit Introduces Jupiter SL871-S GPS Module

Galileo satellite set for new orbit

KVH Receives Order for Military Navigation Systems

TECH SPACE
NASA Awards NASA Balloon Operations Contract

Holiday Season Makes Most of NASA Aeronautics Gifts

Modernized Russian Tu-160 bomber completes 1st flight

Britain's RAF receives first A400M airlifter

TECH SPACE
Giving LEDs a cozy, warm glow

Magic tricks created using artificial intelligence for the first time

Researchers create and control spin waves for enhanced data processing

New technique to help produce next-generation photonic chips

TECH SPACE
NASA Computer Model Provides a New Portrait of Carbon Dioxide

NASA's New Wind Watcher Ready for Weather Forecasters

GOES-S Satellite EXIS Instrument Passes Final Review

NASA Lining up ICESat-2's Laser-catching Telescope

TECH SPACE
European urbanites breathing highly polluted air: report

Cut the salt: Green solutions for highway snow and ice control

Study: Six toxic flame retardants found in humans

India sending 'chilling message' on environment: Greenpeace




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - 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. 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 All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.