Archive for Alan Jacobsen
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Researchers perform both theoretical analyses and finite element simulations to demonstrate for the first time that without changing the material tangent stiffness, residual stress within the beam can directly influence the bending stiffness of the beam. The direct influence arises from geometry nonlinearity and Poisson’s ratio effect. For a cantilever beam with adsorbed macromolecules on its surfaces, we find that longer macromolecular chains with lower normal stiffness and larger intermolecular forces would make the effect of the residual stress even more pronounced. The present work provides guidelines for improving the sensitivity of cantilever-based sensors.
The DOE announced it has reached a major milestone in its efforts to clean up the Cold War legacy at the Savannah River Site in South Carolina, laying the groundwork for closing two underground storage tanks that previously held radioactive liquid waste from nuclear weapons production at SRS. The determination signed by DOE Secretary Steven Chu paves the way for SRS to begin closing the massive tanks that make up the F Tank Farm. The site will start this year by closing two tanks that pose the greatest risk to the environment: Tanks 18 and 19. These tank closures will be the first DOE tanks closed nationwide since 2007, the first closed at SRS in 15 years, and some of the largest underground storage tanks closed by the DOE to date.
(Discover) Faced with a DOD charge to manipulate well-known materials in new ways, Alan Jacobsen, a research scientist at HRL Laboratories in California, constructed delicate lattices of polymer fibers less than a millimeter thick. He then coated the lattices with nickel and dissolved the polymer, leaving behind the spindly metal mesh. Surprisingly, minimizing weight does not mean sacrificing strength and resilience. “I was playing with it, marveling at the weight, and I squished it between my fingers,” materials scientist Tobias Schaedler says. “It bounced right back to its original size.” The lattice can recover after being compressed to half its volume. The mesh’s low weight and high durability, Jacobsen says, make it promising for use in airplane wings and automobile shock absorbers. A brick-size piece of the new mesh would weigh less than a paper clip.
(China Post) China’s long-awaited rare earth industry association is due to be established early this month and will cover the majority of companies in the industry chain, in the latest move to consolidate the ill-regulated sector. The association, which will have more than 100 members, will be formally launched in Beijing on April 8, according to people with direct knowledge of the situation, who declined to be named. Several rare earth exploring and processing companies confirmed they have received notification to attend the launch ceremony in April, without elaborating. There has been widespread market speculation for years that the government would set up an official organization to strengthen ties among the industry’s players. The major functions of the organization will include providing production guidelines, market research and channels of communication between companies and the government, the [National Business Daily reported], adding that the association will play a role in influencing rare earth import and export quotas.
(Composites World) ÉireComposites (Galway, Ireland) has successfully produced a 12.6m/85-ft long blade using a reactive thermoplastic, cyclic butylene terephthalate and unique processing technology. …While the Dutch see great promise in APA-6, ÉireComposites found it difficult to process and eventually chose CBT instead. What made this possible was the further development of ÉireComposites’ patented MECH tooling system to enable processing at 200°C to 400°C (392°F to 752°F) without the issues of thermal expansion and with sufficiently fast heat-up and cool-down rates. The new tooling is formed from alternating layers of ceramic cement and carbon fiber-reinforced polyetheretherketone, with electrical heater elements embedded close to the tool surface within a ceramic layer. Because the ceramic becomes rigid at 60°C/140°F, tooling can be built on inexpensive patterns, removed from the pattern after this initial lower temperature cure and then processed to full temperature (200°C to 400°C) via a freestanding postcure. But, CBT availability is an issue. Therefore, ÉireComposites began looking for other materials. Indeed, alongside its TPC blades, ÉireComposites now offers a unique thermoset alternative, using its ceramic carbon fiber/PEEK composite tooling to enable one-piece wind blade production using powdered epoxy technology. [A company official] claims that this thermoset alternative can cut overall blade production cycle time by 65 percent, based on actual processes in use today, and is not limited in terms of part size. The first commercial application is a 12.6m/41.3-ft blade for ACSA Eólica’s (Las Palmas de Gran Canaria, Spain) A27, a 225-kW turbine.