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Triangular aluminum tool kit, filled with polyurethane is constructed to receive various tools and hold them in a snug but quick-release fit as an aid to heavily gloved workers. The kit is designed to allow mounting within easily accessable reach and to provide protection of the tools during storage.
The tooling concepts and manufacturing techniques developed to produce subelements and full-scale bonded test articles for two of the NASA Composites for Advanced Transportation Systems are examined as part of the structural development of graphite/polyimide composite material systems for the Space Shuttle Orbiter and other space transportation systems. The subassembly and the assembly bonding of the test articles were accomplished using self-tooling and low-cost aluminum tooling concepts in order to eliminate the need for complex and expensive tools. Processing procedures and tooling approaches were developed which permit controlled pressure application on specific bonding planes. Two test articles were fabricated using these techniques, an acoustic panel and a quarter segment of the Space Shuttle aft body flap.
Heat treatment processes, applied after welding but before machining, imparts above normal stability to welded aluminum jigs and tool structures. Weight saving will not be realized in these tools if rigidity equal to that of a comparable steel tool is required.
A design solution is developed for the fabrication of an all-composite helicopter airframe cabin roof structure. Although this is inherently a complex structure, the parts count has been minimized by the avoidance of many mechanical fasteners, and a weight reduction of 26% has been obtained. The reduction of parts and elimination of mechanical fasteners will also result in a lowering of labor costs. The bonded graphite/epoxy elements of the structure employed aluminum tooling with control on all mating surfaces to yield accurate bond lines. A summary of static test results is presented for the basic structure and for the structure with mechanically fastened skin stiffeners. It is shown that the shear buckles caused the skin to peel from the stiffeners at about 960 lb/in. shear flow, calling for the addition of stiffeners with more bond area.
Turbine inlet guide vanes have been fabricated from composites of silicon carbide fibers in silicon carbide matrices. A unique design for a cloth made from SiC fibers makes it possible to realize the geometric features necessary to form these vanes in the same airfoil shapes as those of prior metal vanes. The fiber component of each of these vanes was made from SiC-fiber cloth coated with boron nitride. The matrix was formed by chemical-vapor infiltration with SiC, then slurry-casting of SiC, followed by melt infiltration with silicon. These SiC/SiC vanes were found to be capable of withstanding temperatures 400 F (222 C) greater than those that can be withstood by nickel-base-superalloy turbine airfoils now in common use in gas turbine engines. The higher temperature capability of SiC/SiC parts is expected to make it possible to use them with significantly less cooling than is used for metallic parts, thereby enabling engines to operate more efficiently while emitting smaller amounts of NOx and CO. The SiC/SiC composite vanes were fabricated in two different configurations. Each vane of one of the configurations has two internal cavities formed by a web between the suction and the pressure sides of the vane. Each vane of the other configuration has no web (see Figure 1). It is difficult to fabricate components having small radii, like those of the trailing edges of these vanes, by use of stiff stoichiometric SiC fibers currently preferred for SiC/SiC composites. To satisfy the severe geometric and structural requirements for these vanes, the aforementioned unique cloth design, denoted by the term Y-cloth, was conceived (see Figure 2). In the regions away from the trailing edge, the Y-cloth features a fiber architecture that had been well characterized and successfully demonstrated in combustor liners. To form a sharp trailing edge (having a radius of 0.3 mm), the cloth was split into two planes during the weaving process. The fiber tows forming the trailing-edge section were interlocked, thereby enhancing through-thickness strength of the resulting composite material. For vanes of the webless configuration, each made from a layup of six plies of Ycloth, the length of each Y-cloth layer was cut so that the two strips corresponding to the aforementioned two planes would wrap around the perimeter of a graphite vane preform tool with a 10-mm overlap. The overlap was used to join the two strips in a fringe splice. To make the external sixth ply, a standard woven cloth was cut to the required final length and a fringe splice joined the two ends of the cloth at the trailing edge. The cloth was then prepregged. The entire assembly was then placed into an aluminum compaction tool designed to form the outer net shape of the vane. After the prepreg material was allowed to dry, the preform was removed from the aluminum tooling and placed into an external graphite tool before being shipped to a vendor for matrix infiltration. To make the SiC fiber preform for a vane having an internal web, a slightly different initial approach was followed. Each of two sections forming the internal cavities (and ultimately the web) was created by first slipping two concentric layers of a two-dimensional, 2-by-2, 45 - braided tube around a net-shape graphite mandrel. The tubes on both mandrels were prepregged and allowed to dry. The resulting two subassemblies were put together, then four additional plies were wrapped around them in the same fashion as that described above for the six plies of the vaneless configuration. The consolidation of the SiC fiber preforms into SiC/SiC composite parts was performed by commercial vendors using their standard processes. The capability of two of the webless SiC/SiC turbine vanes was demonstrated in tests in a turbine environment. The tests included 50 hours of steady-state operation and 102 two-minute thermal cycles. A surface temperature of 1,320 C was reached during the tests.
Sensors yield data on deviation from predetermined path and speed. Accuracy and repeatability of continuous-path robot motion measured with new method. Determines ability of robot to maintain tool orientation. Used with any type of manipulator arm and with separate, coordinated part positioner. Noncontacting eddy-current sensors measure distance from tool to aluminum path plate as robot end effector moves tool at prescribed distance from plate. Flat, sloped, curved, and other shapes used for path plate.
The "Auto-Adjustable Pin Tool for Friction Stir Welding", was developed at The Marshall Space Flight Center to address process deficiencies unique to the FSW process. The auto-adjustable pin tool, also called the retractable pin-tool (R.PT) automatically withdraws the welding probe of the pin-tool into the pin-tool's shoulder. The primary function of the auto-adjustable pin-tool is to allow for keyhole closeout, necessary for circumferential welding and localized weld repair, and, automated pin-length adjustment for the welding of tapered material thickness. An overview of the RPT hardware is presented. The paper follows with studies conducted using the RPT. The RPT was used to simulate two capabilities; welding tapered material thickness and closing out the keyhole in a circumferential weld. The retracted pin-tool regions in aluminum- lithium 2195 friction stir weldments were studied through mechanical property testing and metallurgical sectioning. Correlation's can be =de between retractable pin-tool programmed parameters, process parameters, microstructure, and resulting weld quality.
A small friction-stir-welding tool has been developed for use in tack welding of aluminum-alloy workpieces. It is necessary to tack-weld the workpieces in order to hold them together during friction stir welding because (1) in operation, a full-size friction-stir-welding tool exerts a large force that tends to separate the workpieces and (2) clamping the workpieces is not sufficient to resist this force. It is possible to tack the pieces together by gas tungsten arc welding, but the process can be awkward and time-consuming and can cause sufficient damage to necessitate rework. Friction stir tack welding does not entail these disadvantages. In addition, friction stir tack welding can be accomplished by use of the same automated equipment (except for the welding tool) used in subsequent full friction stir welding. The tool for friction stir tack welding resembles the tool for full friction stir welding, but has a narrower shoulder and a shorter pin. The shorter pin generates a smaller workpiece-separating force so that clamping suffices to keep the workpieces together. This tool produces a continuous or intermittent partial-penetration tack weld. The tack weld is subsequently consumed by action of the larger tool used in full friction stir welding tool.
Explosive sizing of 70-inch diameter welded aluminum preforms and tool design of explosive form die
Chisel fits into standard riveting gun. Device has V-shaped cutting end, allowing for easy penetration of material and removal of cuttings.
In this presentation, the results of a recent study on the effect of pin tool design for friction stir welding thin sheets (0.040") of aluminum alloys 2024 and 7075 are provided. The objective of this study was to investigate and document the effect of tool shoulder and pin diameter, as well as the presence of pin flutes, on the resultant microstructure and mechanical properties at both room temperature and cryogenic temperature. Specifically, the comparison between three tools will include: FSW process load analysis (tool forces required to fabricate the welds), Static Mechanical Properties (ultimate tensile strength, yield strength, and elongation), and Process window documenting the range of parameters that can be used with the three pin tools investigated. All samples were naturally aged for a period greater than 10 days. Prior research has shown 7075 may require post weld heat treatment. Therefore, an additional pair of room temperature and cryogenic temperature samples was post-weld aged to the 7075-T7 condition prior to mechanical testing.
The proposed Mars Sample Transfer Chain Architecture provides Planetary Protection Officers with clean samples that are required for the eventual release from confinement of the returned Martian samples. At the same time, absolute cleanliness and sterility requirement is not placed of any part of the Lander (including the deep drill), Mars Assent Vehicle (MAV), any part of the Orbiting Sample container (OS), Rover mobility platform, any part of the Minicorer, Robotic arm (including instrument sensors), and most of the caching equipment on the Rover. The removal of the strict requirements in excess of the Category IVa cleanliness (Pathfinder clean) is expected to lead to significant cost savings. The proposed architecture assumes that crosscontamination renders all surfaces in the vicinity of the rover(s) and the lander(s) contaminated. Thus, no accessible surface of Martian rocks and soil is Earth contamination free. As a result of the latter, only subsurface samples (either rock or soil) can be and will be collected for eventual return to Earth. Uncontaminated samples can be collected from a Category IVa clean platform. Both subsurface soil and rock samples can be maintained clean if they are collected by devices that are self-contained and clean and sterile inside only. The top layer of the sample is removed in a manner that does not contaminate the collection tools. Biobarrier (e.g., aluminum foil) covering the moving parts of these devices may be used as the only self removing bio-blanket that is required. The samples never leave the collection tools. The lids are placed on these tools inside the collection device. These single use tools with the lid and the sample inside are brought to Earth in the OS. The lids have to be designed impenetrable to the Earth organisms. The latter is a well established art.
The use of high-strength, lightweight composites for the fixture is the novel feature of this innovation. The main advantage is the light weight and high stiffness-to-mass ratio relative to aluminum. Meter-class optics require support during the grinding/polishing process with large tools. The use of aluminum as a polishing fixture is standard, with pitch providing a compliant layer to allow support without deformation. Unfortunately, with meter-scale optics, a meter-scale fixture weighs over 120 lb (.55 kg) and may distort the optics being fabricated by loading the mirror and/or tool used in fabrication. The use of composite structures that are lightweight yet stiff allows standard techniques to be used while providing for a decrease in fixture weight by almost 70 percent. Mounts classically used to support large mirrors during fabrication are especially heavy and difficult to handle. The mount must be especially stiff to avoid deformation during the optical fabrication process, where a very large and heavy lap often can distort the mount and optic being fabricated. If the optic is placed on top of the lapping tool, the weight of the optic and the fixture can distort the lap. Fixtures to support the mirror during fabrication are often very large plates of aluminum, often 2 in. (.5 cm) or more in thickness and weight upwards of 150 lb (68 kg). With the addition of a backing material such as pitch and the mirror itself, the assembly can often weigh over 250 lb (.113 kg) for a meter-class optic. This innovation is the use of a lightweight graphite panel with an aluminum honeycomb core for use as the polishing fixture. These materials have been used in the aerospace industry as structural members due to their light weight and high stiffness. The grinding polishing fixture consists of the graphite composite panel, fittings, and fixtures to allow interface to the polishing machine, and introduction of pitch buttons to support the optic under fabrication. In its operation, the grinding polishing fixture acts as a reaction structure to the polishing tool. It must be stiff enough to avoid imparting a distorted shape to the optic under fabrication and light enough to avoid self-deflection. The fixture must also withstand significant tangential loads from the polishing machine during operations.
This year marks the 100th anniversary of the fall of Nakhla, a cumulate clinopyroxenite of martian origin that fell near Alexandria, Egypt in 1911. Multiple fragments of the meteorite were seen to fall over an area of 4.5 km in diameter. Approximately 40 stones were recovered with a combined weight of about 10 kg. Most of the larger specimens found their way to museums and meteorite collections in Cairo, Paris, Berlin, and the Smithsonian, to name a few. In 1998, the British Museum sent a 641g (BM1913,25), fully fusion crusted stone of Nakhla to the Johnson Space Center (JSC) for processing in the Antarctic Meteorite Lab in order to allocate samples to the scientific community. The stone was split in half in a dry nitrogen glove box. One half of the stone was sent back to the museum and the other half (346g) was used for sample allocations. From 1998-2001, 37 scientists requested 65 separate samples of Nakhla, including 2 thin sections This set of allocations was especially important in that all of the sample splits are from the same piece of Nakhla and it had a known history since it was acquired by the museum in 1913. With the multiple fragments of Nakhla, it is not known from what pieces the main bulk of research has been done, what variation may exist between all the pieces and to what contaminants the fragments may have been exposed, (i.e. water, solvents or cutting fluids, etc.). All of the allocations prepared at JSC were processed in a nitrogen cabinet using only stainless steel, aluminum, and Teflon tools and containers to reduce the chance of introducing any new contaminants. The focused effort to subdivide and distribute samples of Nakhla to the meteorite community resulted in enhanced under-standing of Nakhla and nakhlites in general: organic geochemistry, weathering, sulfur isotopes, radiometric age, and magmatic history. There are 13 Nakhlites that have been recovered to date: Nakhla, Layfayette, Governador Valdares, three from NW Africa, three from Yamato and four from Miller Range regions in Antarctica. The Yamato Nakhlites are paired as are the Miller Range samples.
Tooling concepts and processes to control time-temperature characteristics in order to improve tensile properties and reduce porosity in aluminum weldments
Installation of an aluminum sleeve, using specially designed tools, reinforces solder- sealed ferrule joints in installed small-diameter aluminum tubing. Tubing joints reinforced by this method withstand considerable torsional tensional, and vibrational stresses at moderately elevated temperatures.
Very large composite structures, such as those used in NASA's Space Launch System, push the boundaries imposed by current autoclaves. New technology is needed to maintain composite performance and free manufacturing engineers from the restraints of curing equipment size limitations. Recent efforts on a Phase II project by Cornerstone Research Group, Inc. (CRG), have advanced the technology and manufacturing readiness levels of a unique two-part epoxy resin system. Designed for room-temperature infusion of a dry carbon preform, the system includes a no-heat-added cure that delivers 350 F composite performance in a matter of hours. This no-oven, no-autoclave (NONA) composite processing eliminates part-size constraints imposed by infrastructure and lowers costs by increasing throughput and reducing capital-specific, process-flow bottlenecks. As a result of the Phase II activity, NONA materials and processes were used to make high-temperature composite tooling suitable for further production of carbon-epoxy laminates and honeycomb/ sandwich-structure composites with an aluminum core. The technology platform involves tooling design, resin infusion processing, composite part design, and resin chemistry. The various technology elements are combined to achieve a fully cured part. The individual elements are not unusual, but they are combined in such a way that enables proper management of the heat generated by the epoxy resin during cure. The result is a self-cured carbon/ epoxy composite part that is mechanically and chemically stable at temperatures up to 350 F. As a result of the successful SBIR effort, CRG has launched NONA Composites as a spinoff subsidiary. The company sells resin to end users, fabricates finished goods for customers, and sells composite tooling made with NONA materials and processes to composite manufacturers.
Friction stir welding is an innovative weld process that continues to grow in use, in the commercial, defense, and space sectors. It produces high quality and high strength welds in aluminum alloys. The process consists of a rotating weld pin tool that plasticizes material through friction. The plasticized material is welded by applying a high weld forge force through the weld pin tool against the material during pin tool rotation. The high weld forge force is reacted against an anvil and a stout tool structure. A variation of friction stir welding currently being evaluated is self-reacting friction stir welding. Self-reacting friction stir welding incorporates two opposing shoulders on the crown and root sides of the weld joint. In self-reacting friction stir welding, the weld forge force is reacted against the crown shoulder portion of the weld pin tool by the root shoulder. This eliminates the need for a stout tooling structure to react the high weld forge force required in the typical friction stir weld process. Therefore, the self-reacting feature reduces tooling requirements and, therefore, process implementation costs. This makes the process attractive for aluminum alloy circumferential weld applications. To evaluate the application of self-reacting friction stir welding for aluminum alloy circumferential welding, a feasibility study was performed. The study consisted of performing a fourteen-foot diameter aluminum alloy circumferential demonstration weld using typical fusion weld tooling. To accomplish the demonstration weld, weld and tack weld development were performed and fourteen-foot diameter rings were fabricated. Weld development consisted of weld pin tool selection and the generation of a process map and envelope. Tack weld development evaluated gas tungsten arc welding and friction stir welding for tack welding rings together for circumferential welding. As a result of the study, a successful circumferential demonstration weld was produced leading the way for future circumferential weld implementation.