(Press-News.org) ALBUQUERQUE, N.M. — Sandia National Laboratories researchers Lisa Deibler and Arthur Brown had a ready-made problem for their computer modeling work when they partnered with the National Nuclear Security Administration's Kansas City Plant to improve stainless steel tubing that was too hard to meet nuclear weapon requirements.
When steel is too hard it becomes brittle, so the plant ended up getting new tubing. However, Deibler said KCP needed a backup in case it couldn't find replacements in time to meet deadlines.
Sandia's modeling, coupled with experiments, allowed the rapid design of an annealing process to soften the tubing while keeping the metal's desired structure. The model predicted how the microstructure would be affected by variations in the process, which improved researchers' confidence that the heat treatment would produce parts that met specifications.
Brown, a modeler at Sandia's Livermore, Calif., site, said working on the model was a natural extension of a larger project, supported by Sandia's Nuclear Weapons program, called Predicting Performance Margins. Under that program, numerous Sandia researchers are studying the way microstructure affects properties of materials at various scales. Brown became involved in the project as a member of a team that developed a thermal-mechanical modeling tool to predict how microstructure and other properties change during forging. That led to his collaboration with Deibler and Joe Puskar, her Sandia technical adviser, on thermal profiles for welds.
When the need arose to address the tubing issue, Puskar contacted Brown to see if he could work with Deibler to help optimize a heat treatment, Brown said.
Deibler, a postdoctoral appointee in Sandia's Materials Characterization and Performance Department in Albuquerque, provided experimental data that Brown fed into his model of stainless steel recrystallization. Recrystallization, in which grains in deformed microstructures are replaced by strain-free grains, occurs during annealing — the process of heating metal to dissipate energy built up while the metal is compressed, twisted or otherwise worked. Heat makes the metal softer and more ductile.
Deibler and Brown were able to solve the plant's real-life problem since recrystallization is part of the annealing process. And they were able to do it quickly because the model already existed.
Deibler's experiments indicated it was important to model two softening mechanisms, recovery and recrystallization. Recovery happens first within a microstructure when material is heated and softens. By measuring the hardness and the amount of recrystallization after each heat treatment, the team identified how much softening was due to recovery.
"It was important to model both softening mechanisms because we were seeing microstructures that contained no new recrystallized grains, but which had changed properties from the initial deformed material," Deibler said. "By failing to include the effects of recovery, our model couldn't predict why the properties weren't the same as the initial deformed material. Adding in recovery allowed us to account for the changed properties in microstructures with no recrystallization."
She described the work in a poster, "Design of a Heat Treatment to Soften Stainless Steel Tubing," presented at Sandia's winter 2012 Post-Doctoral Technical Showcase.
The team first developed a baseline for the model. Deibler performed heat experiments on the steel tubing since she didn't know the conditions under which it was manufactured. That effort required "a lot of shipping tubing around the country for various heat treatments," she recalled.
She put tubing samples in Sandia's thermal-mechanical experimental system at various temperatures for different lengths of time. Then she had the tubing sectioned, polished and etched, and analyzed the images to see how much the microstructures had recrystallized. Brown fit her data with the model to simulate different heat treatments.
The simulation also required details about the furnace where the tubing would be softened. Heating a furnace quickly tends to overshoot the desired temperature, so the team used the model to determine whether it was better to heat the furnace quickly or slowly raise it to the correct temperature, Deibler said. Once Brown identified the optimal rate of increase and other factors, KCP technicians filled a furnace with tubing and measured temperatures at several locations inside. Brown then ran those profiles through the model, which allowed him to predict the impact of temperature variations on the tubing's final properties.
The researchers want the model to handle both forging and welding because in some ways the two processes work against one another. Forging steel gives it a strong microstructure, but welding adds heat that can destroy those properties. "So if you were able to model that process, that would provide a lot more confidence in the overall modeling that their parts aren't going to fail," Deibler said.
In the future, the researchers want use the model for all kinds of welding at Sandia: laser welding, resistance welding and gas tungsten arc welding. Types of welding vary in their thermal rates — how fast something is heated.
"Looking at how different heating and cooling rates affect the microstructure during welding would give us valuable information," Deibler said.
###
Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies, and economic competitiveness.
Sandia news media contact: Sue Holmes, sholmes@sandia.gov, (505) 844-6362
END
Cyclone Imelda has lost both her punch and her hurricane status as the storm moved into an area of higher wind shear and cooler waters in the Southern Indian Ocean. NASA's Aqua satellite provided an image of Imelda that showed wind shear that has been hammering the storm, had pushed the bulk of the storm's precipitation southeast of the center.
Wind shear at higher levels has increased to as high as 30 knots (34.5 mph/55.5 kph), according to upper level analysis of the atmosphere that was conducted by the Joint Typhoon Warning Center. That stronger wind shear is weakening ...
CHAMPAIGN, Ill. — Though they be but little, they are fierce. The most powerful batteries on the planet are only a few millimeters in size, yet they pack such a punch that a driver could use a cellphone powered by these batteries to jump-start a dead car battery – and then recharge the phone in the blink of an eye.
Developed by researchers at the University of Illinois at Urbana-Champaign, the new microbatteries out-power even the best supercapacitors and could drive new applications in radio communications and compact electronics.
Led by William P. King, the Bliss ...
University of Missouri engineer Randy Curry and his team have developed a method of creating and controlling plasma that could revolutionize American energy generation and storage. Besides liquid, gas and solid, matter has a fourth state, known as plasma. Fire and lightning are familiar forms of plasma. Life on Earth depends on the energy emitted by plasma produced during fusion reactions within the sun. However, Curry warns that without federal funding of basic research, America will lose the race to develop new plasma energy technologies. The basic research program was ...
Three unusually long-lasting stellar explosions discovered by NASA's Swift satellite represent a previously unrecognized class of gamma-ray bursts (GRBs). Two international teams of astronomers studying these events conclude that they likely arose from the catastrophic death of supergiant stars hundreds of times larger than the sun.
VIDEO:
GRB 101225A, better known as the "Christmas burst, " was an unusually long-lasting gamma-ray burst. Because its distance ...
As Earth moves around the sun, it travels surrounded by a giant bubble created by its own magnetic fields, called the magnetosphere. As the magnetosphere plows through space, it sets up a standing bow wave or bow shock, much like that in front of a moving ship. Just in front of this bow wave lies a complex, turbulent system called the foreshock. Conditions in the foreshock change in response to solar particles streaming in from the sun, moving magnetic fields and a host of waves, some fast, some slow, sweeping through the region.
To tease out what happens at that boundary ...
A previous study by the University of Colorado Cancer Center reported the common side effect of low testosterone in men treated with the recently approved lung cancer agent, crizotinib. A new study published this week in the journal Cancer confirms this finding in a multi-national sample, details the mechanism of reduced testosterone, and provides promising preliminary evidence that widely available hormone replacement therapies can alleviate this side effect in many patients.
"This was a wonderful collaboration between multiple centers confirming a side effect that had ...
April 16, 2013 – San Francisco – Brain scans are increasingly able to reveal whether or not you believe you remember some person or event in your life. In a new study presented at a cognitive neuroscience meeting today, researchers used fMRI brain scans to detect whether a person recognized scenes from their own lives, as captured in some 45,000 images by digital cameras. The study is seeking to test the capabilities and limits of brain-based technology for detecting memories, a technique being considered for use in legal settings.
"The advancement and falling costs ...
Overworked and stressed out? Look on the bright side. Some stress is good for you.
"You always think about stress as a really bad thing, but it's not," said Daniela Kaufer, associate professor of integrative biology at the University of California, Berkeley. "Some amounts of stress are good to push you just to the level of optimal alertness, behavioral and cognitive performance."
New research by Kaufer and UC Berkeley post-doctoral fellow Elizabeth Kirby has uncovered exactly how acute stress – short-lived, not chronic – primes the brain for improved performance.
In ...
Combining CT imaging findings with baseline serum lactate dehydrogenase levels is showing promise as a way to predict survival in patients with metastatic melanoma being treated with anti-angiogenic therapy.
With the hope of predicting patient survival, researchers at the University of Mississippi Medical Center in Jackson and at the Ohio State University Comprehensive Cancer Center in Columbus analyzed CT images and clinical data from 46 patients with metastatic melanoma that were treated with anti-angiogenic therapy. "The analysis found that initial post-therapy CT ...
The estimated size of chest lymph nodes and lung nodules seen on CT images varies significantly when the same nodes or nodules are examined using lower versus higher doses of radiation, a new study shows. The size of lymph nodes and lung nodules is an important determinant of treatment and treatment success.
The study, conducted at Massachusetts General Hospital in Boston, used a 3D image processing tool to quantitatively measure the volume of the lymph nodes and lung nodules. "We found that lymph node volumes were estimated at 30% lower in five cases and 10% higher in ...
