Lower Chatter Friction Pull Plug Welding (FPPW)
The new friction pull plug design is optimized to reduce chatter that results as a fast rotating plug enters the hole in the part. The plug design is based on a shank with multiple frustoconical sections shown in the figure to the right. The sections are carefully sized to ensure that the spinning plug contacts the edge of the hole at just the right position to minimize chatter. It keeps the machine from stalling when the plug enters the hole. This new design makes FPPW more practical, perhaps even as a future rivet replacement.
Ultrasonic Stir Welding
Ultrasonic Stir Welding is a solid state stir welding process, meaning that the weld work piece does not melt during the welding process. The process uses a stir rod to stir the plasticized abutting surfaces of two pieces of metallic alloy that forms the weld joint. Heating is done using a specially designed induction coil. The control system has the capability to pulse the high-power ultrasonic (HPU) energy of the stir rod on and off at different rates from 1-second pulses to 60-millisecond pulses. This pulsing capability allows the stir rod to act as a mechanical device (moving and stirring plasticized nugget material) when the HPU energy is off, and allowing the energized stir rod to transfer HPU energy into the weld nugget (to reduce forces, increase stir rod life, etc.) when the HPU energy is on. The process can be used to join high-melting-temperature alloys such as titanium, Inconel, and steel.
materials and coatings
A New Class of Strong and Flexible Carbon Fiber Reinforced Phenolic Composites
This unique approach modifies the phenolic polymer network by adding thermoplastic molecules with flexible segments such as aliphatic carbon and siloxane. The thermoplastic molecules are terminated with bifunctional groups that can directly react with the phenolic under the curing condition to form chemical bonds. Further incorporation of these segments can be facilitated by a relay reaction of a second molecular component which can bond with both the first flexible segments and the phenolic network. The selections of flexible, thermoplastic segments are based on desired properties, which include flexibility, ablative, an charring ability, heat resistance, and low catalycity. The modified phenolic is a truly molecular composite in which flexible segments are connected with the phenolic network through strong chemical bonds and are uniformly distributed among the networks. This feature renders a uniform toughening/strengthening effect without compromising the lightweight nature of the materials. The process is also feasible to scale up and amenable for manufacturing.
Power Generation and Storage
Solid-State Ultracapacitor for Improved Energy Storage
NASAs solid-state ultracapacitor technology is based on the novel materials design and processes used to make the IBLC-type ultracapacitor. The IBLC concept is known to provide outstanding capacitance behavior but has been difficult to reproduce. NASA has developed a careful process to produce dielectric materials to be used in printed electronic applications with reproducibility. An individual cell is created by building electrodes on each side of the dielectric layer, and complete modules can be constructed by stacking multiple cells. Closely related NASA innovations on dielectric and conductive ink (electrode) formulations are key to the ultracapacitor construct, and are included in the technology package. Target performance criteria of this technology include the following: • Use of standard materials and processing methods • Robust, solid-state device with no liquid electrolytes • High-energy densitytarget energy densities of 60 J/cc at a minimum operating voltage of 50 V • High dielectric breakdown strength (> 25 MV/m) • Excellent pulse-power performance; rapid discharge and charge • Reliable performance under repeated cycling (> 500,000 cycles) Additional development work is underway to build and test complete capacitor modules and further improve material properties and performance.
Materials and Coatings
New Dielectric Material for High-Performance, Solid-State Ultracapacitors
NASA’s technology is a dielectric materials formulation comprising polymers, organic binders, solvents, and surfactants, formulated together with a ceramic perovskite nanopowder. The ceramic nanopowder can be optimized for the required dielectric properties of capacitance, voltage breakdown, and leakage. This involves the addition of dopants or the use of advanced coatings on the powder particulates, and subsequent thermal treatments. The rheology of the formulation can be adjusted to work with a variety of coating or printing methods, from conventional thick-film methods to advanced inkjet or direct-write 3D printing methods used for printed electronics. 3D printing provides the ease of printed manufacturing along with the deposition of thinner layers (e.g., 5 microns in thickness vs. 50-100 micron layer via thick-film methods). Individual devices can then be formed in multilayer arrangements, or stacked and packaged as required for the given device application. The ink composition is a careful blend of polyimide or polyvinylidene fluoride (PVDF) polymers, solvents, surfactants, and barium titanate nanopowders. Proper ratios are needed for viscosity and processability (e.g., nanopowder wetting and dispersion), along with the optimal ultracapacitor device performance.
mechanical and fluid systems
These patented gear bearings provide superior speed reduction in a small package. They form rolling friction systems that function both as gears and bearings and are compatible with most gear types, including spur, helical, elliptical, and bevel gears. These self-synchronized components can be in the form of planets, sun, rings, racks, and segments thereof. The design reduces micro chatter and eliminates rotational wobble to create smooth and precise control. It offers tighter mesh, more even gear loading, and reduced friction and wear. Gear bearings eliminate separate bearings, inner races, and carriers, as well as intermediate members between gears and bearings. Load paths go directly from one gear bearing component to another and then to ground. By incorporating helical gear teeth forms (including herringbone), gear bearings provide outstanding thrust bearing performance. They also provide unprecedented high- and low-speed reduction through the incorporation of phase tuning. Phase tuning allows differentiation in the number of teeth that must be engaged govbetween input and output rings in a planetary gearset, enabling successful reduction ratios of 2:1 to 2,000:1. They provide smooth and accurate control with rifle-true anti-backlash. This produces a planetary transmission with zero backlash. The gear bearing technology is based on two key concepts: the roller gear bearing and the phase-shifted gear bearing. All designs are capable of efficiently carrying large thrust loads. Existing gear systems have drawbacks including weak structures, large size, and poor reliability, as well as high cost for some types (e.g., harmon-ic drives). Gear bearings solve these problems with simpler construction, fewer parts, and superior strength. By selecting the appropriate manufacturing method and materials, gear bearings can be tailored to benefit any application, from toys to aircraft.
Lightweight Fiber Optic Sensors for Real-Time Monitoring of Structural Health
<strong><i>How It Works </strong></i> The FOSS technology employs efficient, real-time, data driven algorithms for interpreting strain data. The fiber Bragg grating sensors respond to strain due to stress or pressure on the substrate. The sensors feed these strain measurements into the systems algorithms to determine shape, stress, temperature, pressure, strength, and operational load in real time. <strong><i>Why It Is Better </strong></i> Conventional strain gauges are heavy, bulky, spaced at distant intervals (which leads to lower resolution imaging), and unable to provide real-time measurements. Armstrong's system is virtually weightless, and thousands of sensors can be placed at quarter-inch intervals along an optical fiber the size of a human hair. Because these sensors can be placed at such close intervals and in previously inaccessible regions (for example, within bolted joints, embedded in a composite structure), the high-resolution strain measurements are more precise than ever before. The fiber optic sensors are non-intrusive and easy to install—thousands of sensors can be installed in less time than conventional strain sensors and the system is capable of processing information at the unprecedented rate of 100 samples per second. This critical, real-time monitoring capability enables an immediate and informed response in the event of an emergency and allows for precise, controlled monitoring to help avoid such scenarios. <b><i>For more information about the full portfolio of FOSS technologies, see DRC-TOPS-37 or visit <a href=https://technology-afrc.ndc.nasa.gov/featurestory/fiber-optic-sensing>https://technology-afrc.ndc.nasa.gov/featurestory/fiber-optic-sensing</a></b></i>