Browse Topic: Vacuum
This paper presents an experimental-numerical investigation on the axial strain of highly-curved blades. Models of the blades were analyzed using a 2-D finite element code, SectionBuilder, coupled with a comprehensive analysis code, Dymore, and first validated using strain measurements under a static tip load. Frequency responses were obtained under an impulsive load for each of the blades with multiple boundary conditions and compared with the numerical models. Experimental measurements under centrifugal loading from 0 up to 3300 RPM in a vacuum showed the effect of curvature on the axial strain, with significant bending strains observed in the responses for the curved blades that were also well captured by the numerical analysis. The present analysis shows that even moderate levels of out-of-plane curvature significantly increases the strain magnitudes, while higher levels of in-plane curvature have a much smaller impact.
ABSTRACT The current method used for bonding liners onto dynamic components requires the use of spring-loaded clamps, vacuum bags, and ovens. This process works well for our smaller articles although has posed problems for our larger bonding requirements. The primary problem for our large bonded components is our ovens would take up to 3.5 hrs. to heat the thickest areas up to bonding temperature. For the adhesives that we use the recommended temperature ramp-up time is 20-60 minutes. In addition, the thinner areas reach temperature sooner and would exceed the recommended maximum curing time of 60 min. A minimum of 25 pounds per square inch (PSI) is required to achieve a sound bondline. The clamps used during cure cycles rely on springs to apply pressure to the liner being bonded. The pressure they exert is not exact, and tends to vary. A vacuum bag can only apply the pressure that is supplied by shop air, 14.7 psi. The solution to achieving uniform and accurate pressure during bonding operations is to have a flexible zoned system that can bring all the areas, thick and thin, to temperature simultaneously, apply even amounts of pressure to the liners, and record all zones of temperature and pressure during the bonding process. Through the entire process, the zones are monitored, recorded, and graphed. This system can be moved anywhere within the factory because the heating elements and the air bladders are incorporated into the fixture.
The analysis and simulation of gases expanding from sources such as rocket nozzles into vacuum, or the effects plumes from these sources create when they interact with solid surfaces, present a considerable challenge to the scientific and engineering communities. As a plume expands into vacuum, density levels, and hence collision rates, decrease rapidly by many orders of magnitude. The main difficulty lies in accurately describing a flow field extending from continuum flow at the nozzle exit, through the transition regime, and reaching free molecule behavior within a relatively short distance downstream. For thrusters, flow at the nozzle exit is usually characterized by high exit velocities and relatively high Mach numbers. Even in regions where significant intermolecular collision rates occur, relative velocity levels are low, and little thermal scattering occurs normal to the mainly radial streamlines. Such observations lead one to consider describing the expansion under certain circumstances using free molecule theory.
NASA has long recognized the difficulty in providing emergency medical care to astronauts in space. Many aspects of space travel make medical care inherently difficult, and sufficient storage space for medical equipment severely limits the ability to carry a full complement of diagnostic and therapeutic equipment onboard. The Microgravity Compatible Medical Suction Device (MCMSD) enables aspiration and containment of bodily fluids and vomitus, while preventing the transmission of infectious agents.
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