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Installing a Test Tap on a Metal Battery Case

A mechanical fitting and relatively simple and safe method of installing it on the metal case of a battery have been devised to provide access to the interior of the battery to perform inspection and/or to measure such internal conditions as temperature and pressure. A metal boss or stud having an exterior thread is attached to the case by capacitor-discharge stud welding (CDSW), which takes only 3 to 6 milliseconds and in which the metallurgical bond (weld) and the heat-affected zone are limited to a depth of a few thousandths of an inch (a few hundredths of a millimeter).

Posted in: Manufacturing & Prototyping, Briefs, TSP

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Linear Actuator Has Long Stroke and High Resolution

There are potential applications in precise measurement and precise fabrication. The term “precision linear actuator, direct drive” (“PLADD”) refers to a robust linear actuator designed to be capable of repeatedly performing, over a lifetime of the order of 5 to 10 years, positioning maneuvers that include, variously, submicron increments or slews of the order of a centimeter. The PLADD is capable of both long stroke (120 mm) and high resolution (repeatable increments of 20 nm). Unlike precise linear actuators of prior design, the PLADD contains no gears, levers, or hydraulic converters. The PLADD, now at the prototype stage of development, is intended for original use as a coarse-positioning actuator in a spaceborne interferometer. The PLADD could also be adapted to terrestrial applications in which there are requirements for long stroke and high resolution: potential applications include medical imaging and fabrication of semiconductor devices.

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Fabricating PFPE Membranes for Capillary Electrophoresis

Precisely sized and positioned holes are defined by photomasks. A process has been developed for fabricating perfluoropolyether (PFPE) membranes that contain microscopic holes of precise sizes at precise locations. The membranes are to be incorporated into “laboratory-on-a-chip” microfluidic devices to be used in performing capillary electrophoresis.

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Fabricating PFPE Membranes for Microfluidic Valves and Pumps

This process contributes to development of “laboratory-on-a-chip” devices. A process has been developed for fabricating membranes of a perfluoropolyether (PFPE) and integrating them into valves and pumps in “laboratory-on-a-chip” microfluidic devices. Membranes of poly(tetrafluoroethylene) [PTFE] and poly(dimethylsilane) [PDMS] have been considered for this purpose and found wanting. By making it possible to use PFPE instead of PTFE or PDMS, the present process expands the array of options for further development of microfluidic devices for diverse applications that could include detection of biochemicals of interest, detection of toxins and biowarfare agents, synthesis and analysis of proteins, medical diagnosis, and synthesis of fuels.

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Structural/Radiation-Shielding Epoxies

Pendant aliphatic groups are incorporated as integral parts of molecular structures. A development effort was directed toward formulating epoxy resins that are useful both as structural materials and as shielding against heavy-ion radiation. Hydrogen is recognized as the best element for absorbing heavy-ion radiation, and high- hydrogen-content polymers are now in use as shielding materials. However, high- hydrogen-content polymers (e.g. polyethylene) are typically not good structural materials. In contrast, aromatic polymers, which contain smaller amounts of hydrogen, often have the strength necessary for structural materials. Accordingly, the present development effort is based on the concept that an ideal structural/heavy-ion-radiation-shielding material would be a polymer that contains sufficient hydrogen (e.g., in the form of aliphatic molecular groups) for radiation shielding and has sufficient aromatic content for structural integrity.

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Modal Vibration Analysis of Large Castings

Massive objects can be tested in situ, without precisely controlling boundary conditions. The art of experimental modal vibration analysis (MVA) has been extended to apply to large castings. This extension was made to enable the use of experimental MVA as a relatively inexpensive, simple means of assessing the internal structural integrity of tread shoes of crawler transporters used to move spacecraft to the launch pad at Kennedy Space Center. Each tread shoe is made from cast iron and weighs about a ton (has a mass ≈907 kg). The present extended version of experimental MVA could also be applied to other large castings. It could be especially useful to manufacturers as a means of rapidly discriminating against large castings that contain unacceptably large concentrations of internal defects.

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Laser Ablation Increases PEM/Catalyst Interfacial Area

Increased interfacial area is expected to result in improved fuel-cell performance. An investigational method of improving the performance of a fuel cell that contains a polymer-electrolyte membrane (PEM) is based on the concept of roughening the surface of the PEM, prior to deposition of a thin layer of catalyst, in order to increase the PEM/catalyst interfacial area and thereby increase the degree of utilization of the catalyst. The roughening is done by means of laser ablation under carefully controlled conditions. Next, the roughened membrane surface is coated with the thin layer of catalyst (which is typically platinum), then sandwiched between two electrode/catalyst structures to form a membrane/electrode assembly.

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