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Singapore Launches First Driverless Vehicles for Public

Researchers and engineers from the Singapore — MIT Alliance for Research and Technology (SMART) and the National University of Singapore (NUS) are deploying two driverless vehicles, free‑of‑charge, for public use. They will feature vehicle‑to‑vehicle communications that will allow each vehicle to know where the other vehicle is.

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M8/M12 Connector System: When Communication Simply Needs to Work

As industry specifications become stricter, the need for ruggedized and reliable connections increases. Learn how TE Connectivity's (TE's) M8/M12 product line, widely used within industrial automation environments and applications, can strengthen communication, decrease downtime and provide a complete solution for your interconnect needs.

Posted in: Tech Talks

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Jeff Ding, Aerospace Welding Engineer, Marshall Space Flight Center, Huntsville, AL

Jeff Ding developed Ultrasonic Stir Welding (USW) to join large pieces of very high‑strength metals, such as titanium and Inconel. The solid-state weld process improves the current Thermal Stir Welding process by adding high-power ultrasonic (HPU) energy at 20 kHz frequency. NASA Tech Briefs: What is Ultrasonic Stir Welding? Jeff Ding: Ultrasonic Stir Welding is a solid‑state weld process, which means the material being welded does not melt. The material is heated into a plastic state which is between solid and liquid. (Weld properties resulting from a solid state weld process are superior as compared to those properties resulting from fusion weld processes that melt the weld material). Finally, ultrasonic energy is integrated into the stir rod and a non-rotating containment plate. NTB: What are the advantages of this type of welding? Ding: I've integrated ultrasonics through the stir pin, as well as a non‑rotating containment plate. The ultrasonics operate at 20 kHz, about 4 and a half kilowatts of power. The advantages of integrating ultrasonics are an overall reduction in plunge, frictional and shear forces as compared to Friction Stir Welding. Faster travel rates can also be realized. NTB: What are commercial applications for this type of welding? Ding: I've just started the development of the process. I'm hoping to see an increase in travel rate. I believe we can see up to twenty inches a minute, maybe even faster. This would put the process in the same class as other weld processes in the commercial sector, where an increase in travel rate going as fast as you can means dollars to a company. By being able to take a solid‑state weld process and increased travel to be competitive with other fusion weld processes, such as tig or mig electron beam, now this could be a value to the commercial sector. Also, by reducing the overall loads of the process, it is feasible to integrate the process with relatively inexpensive, off‑the‑shelf robots for robotic applications. NTB: Could it even play a role in manufacturing in space? Ding: Absolutely. The agency has to consider making things, in real time, onboard the space capsule or in space. Right now we have the 3D printer on the Space Station, demonstrating the capability to make parts. Let's say we do have the 3D printer producing some parts of subcomponents in the event of a failure of some kind. There has to be a process to take subcomponents and join them into an overall part. Welding certainly has to be considered. Ultrasonic welding would be a safe process for the operator, as there are no high‑energy beams, and no spatter as you would find in electron beam welding, which has been considered for welding in space. This would produce a safe process for the operator and get the same benefits as other fusion weld processes. NTB: Is there an ease of use advantage with this type of process? Ding: It would be easier in respect to protecting the operator from any possible harm from using the process, compared to, say, electron beam, if that were selected. I'm sure in the development of in‑space applications, you would have to consider all the safety and overcome all of those issues. The same thing with ultrasonics welding in space. You'd have to overcome safety issues, but as I mentioned, the safety issues would not be as severe as those experience with the fusion weld processes. NTB: Why is ultrasonic stir welding such an exciting technology? Ding: It has never been done before. It is certainly leading‑edge. Early data from 2008 and 2010 and 2011 that I've generated indicates that it is feasible, and it is doable, so we'll see after the development effort goes on. NTB: What is your day‑to‑day work now with the technology? Ding: I've just completed some initial welds to look at, and based upon the results, I will change the development effort, and I will eventually get into a design of experiments to find out what the best parameters are for different materials: aluminums and your heat‑resistant alloys, such as your titaniums and your steels. One thing I have not done yet in the early development effort: I have not pulsed the ultrasonics on and off during a welding, and I think this will be beneficial to the quality of the weld, as compared with welds done with the ultrasonics just constantly on through the weld. NTB: And why is that? Ding:One of the experiments that I did in 2008: I inserted a steel rod about half an inch diameter up into the tool holder, the spindle holder. Without this little half‑inch‑diameter rod rotating at all, just being static, I turned the ultrasonics on. If you slide your finger over the steel rod, you'll find that it feels like it is totally lubricated. Turn the ultrasonics off: and then you'll feel the friction between your skin and the rod. What this tells me is that, in a Stir Weld process, we want to move the plasticized material in the weld nugget. We're moving it from the advancing side to the retreating side of the weld nugget (relative to stir rod rotation). And you have to wonder: Is this material movement even possible by having the ultrasonics on all the time? Are we slipping through that plastic nugget as we're trying to move material from the advancing to the retreating side of the nugget? It's just a theory right now, and I have to do the work and start pulsing it on and off to see what the effect is of having the ultrasonics on and ultrasonics off. When you pulse it off, through a stir pin, it will act as a mechanical device to move the plastic material, similar to Friction Stir Welding. When it is on, it will act as a device to increase travel speed and reduce the sheer forces on the pin as it's traveling through the weld, and that's what I feel is going to happen when it's on. When it's off, it will be a mechanical device. NTB: You won our 2012 Create the Future Design Contest with your Thermal Stir Weld process. How is Ultrasonic Stir Welding different? Ding: Thermal Stir is similar to Ultrasonic Stir Welding, in that I have non‑rotating containment plates, a stir rod, and an induction coil for heating. [Similarly,] I have decoupled the heating, stirring, and the forging of Friction Stir Welding so I can control each element independently. Thermal Stir Welding doesn't have any ultrasonics, and Thermal Stir Welding is designed for heat‑resistant alloys, such as your thick‑sectioned titanium. I was very successful in welding half‑inch‑thick titanium — commercially pure and Ti 6‑4 ELI. Right now the ultrasonic stir welding prototype system is only designed for a quarter‑inch material and less. It's just a testbed to characterize the process and show the benefits of it. I do hope to get ultrasonics integrated into the Thermal Stir process so I can realize these benefits in the thick‑sectioned alloys, by using ultrasonics. When it's all said and done, Ultrasonic Stir Welding and Thermal Stir Welding will be very, very similar in nature. In order to pursue the technology, of course, it comes down to funding. And in these austere times, it's very difficult to get the level of funding to advance the technology to the next higher level. So it's in the prototype phase. What's next for Ultrasonic Stir Welding? Ding: After we prove out the benefits, the next level would be to build the necessary equipment to demonstrate this for a commercial application. We do have another weld system at Marshall. It's called High‑Speed Friction Stir Welding, and it would be relatively easy to remove the main spindle stack, integrate ultrasonics in it and then reattach the spindle stack to the machine. This machine would have the capability of integrated motion. It would be able to do circles and complex paths, not necessarily just linear welds. It could do a number of things, and this would be beneficial in demonstrating the process for an application in the commercial sector. To learn more about Ultrasonic Stir Welding, read a full transcript, or listen to a downloadable podcast, visit www.techbriefs.com. SIDEBAR: Want to learn more? Jeff Ding will host a live webcast on November 13. To register for the free Ultrasonic Stir Welding presentation, go to http://www.techbriefs.com/webinar250.

Posted in: Who's Who

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Researchers Measure Stress in 3D-Printed Metal Parts

Lawrence Livermore National Laboratory researchers have developed an efficient method to measure residual stress in metal parts produced by powder-bed fusion additive manufacturing (AM).The 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 the method produces quality parts and components, residual stress is a major problem during the fabrication process. Large temperature changes near the last melt spot, and the repetition of this process, result in localized expansion and contraction.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). The process provides 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.SourceAlso: Learn about Design and Analysis of Metal-to-Composite Nozzle Extension Joints.

Posted in: News

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NASA Computer Model Reveals Carbon Dioxide Levels

An ultra-high-resolution NASA computer model has given scientists a stunning new look at how carbon dioxide in the atmosphere travels around the globe.Plumes of carbon dioxide in the simulation swirl and shift as winds disperse the greenhouse gas away from its sources. The simulation also illustrates differences in carbon dioxide levels in the northern and southern hemispheres, and distinct swings in global carbon dioxide concentrations as the growth cycle of plants and trees changes with the seasons.Scientists have made ground-based measurements of carbon dioxide for decades and in July NASA launched the Orbiting Carbon Observatory-2 (OCO-2) satellite to make global, space-based carbon observations. But the simulation — the product of a new computer model that is among the highest-resolution ever created — is the first to show in such fine detail how carbon dioxide actually moves through the atmosphere.In addition to providing a striking visual description of the movements of an invisible gas like carbon dioxide, as it is blown by the winds, this kind of high-resolution simulation will help scientists better project future climate. Engineers can also use this model to test new satellite instrument concepts to gauge their usefulness. The model allows engineers to build and operate a “virtual” instrument inside a computer.SourceAlso: Learn about the NASA Data Acquisition System (NDAS).

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3D Audio Research Helps Make Cockpit Safer

Imagine yourself in a cockpit, flying a mission, listening to a multitude of critical voices delivering vital messages, all at the same time and from the same direction. Now imagine the same environment, except that the voices are now distinct and separate. The Air Force Research Laboratory (AFRL) has developed 3D sound technology that creates a sound environment that mimics the way the human body receives aural cues, much like 3D movies create the perception that the viewer is part of the movie.

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NASA Tests Revolutionary Shape-Changing Aircraft Flap

NASA's green aviation project is one step closer to developing technology that could make future airliners quieter and more fuel‑efficient with the successful flight test of a wing surface that can change shape in flight. Researchers replaced an airplane’s conventional aluminum flaps with advanced, shape‑changing assemblies that form seamless bendable and twistable surfaces. Flight testing will determine whether flexible trailing‑edge wing flaps are a viable approach to improve aerodynamic efficiency and reduce noise generated during takeoffs and landings.

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