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At least 217 records · Page 12

All sources NASA NTRS DOE OSTI

NASA NTRS2008

Structural Design and Analysis of the Upper Pressure Shell Section of a Composite Crew Module

This paper presents the results of the structural design and analysis of the upper pressure shell section of a carbon composite demonstration structure for the Composite Crew Module (CCM) Project. The project is managed by the NASA Engineering and Safety Center with participants from eight NASA Centers, the Air Force Research Laboratory, and multiple aerospace contractors including ATK/Swales, Northrop Grumman, Lockheed Martin, Collier Research Corporation, Genesis Engineering, and Janicki Industries. The paper discusses details of the upper pressure shell section design of the CCM and presents the structural analysis results using the HyperSizer structural sizing software and the MSC Nastran finite element analysis software. The HyperSizer results showed that the controlling load case driving most of the sizing in the upper pressure shell section was the internal pressure load case. The regions around the cutouts were controlled by internal pressure and the main parachute load cases. The global finite element analysis results showed that the majority of the elements of the CCM had a positive margin of safety with the exception of a few hot spots around the cutouts. These hot spots are currently being investigated with a more detailed analysis. Local finite element models of the Low Impact Docking System (LIDS) interface ring and the forward bay gussets with greater mesh fidelity were created for local sizing and analysis. The sizing of the LIDS interface ring was driven by the drogue parachute loads, Trans-Lunar Insertion (TLI) loads, and internal pressure. The drogue parachute loads controlled the sizing of the gusset cap on the drogue gusset and TLI loads controlled the sizing of the other five gusset caps. The main parachute loads controlled the sizing of the lower ends of the gusset caps on the main parachute fittings. The results showed that the gusset web/pressure shell and gusset web/gusset cap interfaces bonded using Pi-preform joints had local hot spots in the Pi-preform termination regions. These regions require a detailed three-dimensional analysis, which is currently being performed, to accurately address the load distribution near the Pi-preform termination in the upper and lower gusset caps.

Sleight, David W.↗

NASA NTRS1957

Experimental Investigation of Vibratory Stresses in a Concentric-Ring Direct-Air-Cycle Nuclear Fuel Element

Preliminary tests made by the General Electric Company indicated that aerodynamic loads might cause large enough distortions in the thin sheet-metal rings of a nuclear fuel element to result in structural failure. The magnitude of the distortions in a test fuel element was determined from strains measured with airflow conditions simulating those expected during engine operation. The measured vibratory strains were low enough to indicate the improbability of failure by fatigue. A conservative estimate of the radial deflection that accompanied peak strains in the outer ring was +0.0006 inch.

Chiarito, Patrick T.↗

DOE OSTI2016

High power s-band vacuum load

Through a combination of experimentation and calculation the components of a novel room temperature dry load were successfully fabricated. These components included lossy ceramic cylinders of various lengths, thicknesses, and percent of silicon carbide (SiC). The cylinders were then assembled into stainless steel compression rings by differential heating of the parts and a special fixture. Post machining of this assembly provided a means for a final weld. The ring assemblies were then measured for S-parameters, individually and in pairs using a low-cost TE10 rectangular to TE01 circular waveguide adapter specially designed to be part of the final load assembly. Matched pairs of rings were measured for assembly into the final load, and a sliding short designed and fabricated to assist in determining the desired short location in the final assembly. The plan for the project was for Muons, Inc. to produce prototype loads for long-term testing at SLAC. The STTR funds for SLAC were to upgrade and operate their test station to ensure that the loads would satisfy their requirements. Phase III was to be the sale to SLAC of loads that Muons, Inc. would manufacture. However, an alternate solution that involved a rebuild of the old loads, reduced SLAC budget projections, and a relaxed time for the replacement of all loads meant that in-house labor will be used to do the upgrade without the need for the loads developed in this project. Consequently, the project was terminated before the long term testing was initiated. However, SLAC can use the upgraded test stand to compare the long-term performance of the ones produced in this project with their rebuilt loads when they are available.

42 ENGINEERING↗

NASA NTRS1974

Theory to test comparisons for selected aerospace multishell structures and their interfaces under thermomechanical loadings

Guidelines for structural shell analyses were obtained on the basis of theory-to-test comparisons made on two large-scale aerospace structures subject to thermomechanical loads. The first structural test was the cylindrical aluminum skin-stringer-ring construction of the S-IC forward skirt and S-II interstage. The second structural test included the truncated, cone-shaped, bonded honeycomb sandwich shell of the Spacecraft Lunar Module Adapter; the cylindrical bonded aluminum honeycomb sandwich construction of the Instrument Unit; and the skin-stringer construction with rings and intercostals of the S-IVB forward skirt. Analyses were made for loadings simulating the flight environment. Elementary shear lag theory was superimposed on shell analysis for interface junctions between stages to obtain favorable theory-to-test stress comparisons.

Ferdie, R. D.↗

NASA NTRS1980

Verification of the SRB motor case pin retainer band tips

The pin retainer band is a 1-1/4 in. wide by about 1/32 in. thick steel band that is stretched over the pins circumferentially at the joints of the solid rocket booster (SRB) motor case segments. Its purpose is to hold the retaining pins in place during flight. Since the band is thin and is mounted stretched, or under tension, over the pins which are greased in place, it is necessary to protect it thermally. Three typical areas of the band location on the SRB motor case joints were chosen for verifying the cork thermal prection system (TPS) performance on the band: the joint in front of the attach ring, at the aft skirt joint in front of the kick ring and in an unperturbed area at the forward segments of the SRB motor cases. The kick ring area pin retainer band cork TPS passed the test requirements in the region where there are no phenolic splice caps. In the splice cap areas where the band TPS is closed out around the splice with K5NA, additional amounts of K5NA material is required to adequately protect the steel band. TPS requirements were easily met in the one location where the ends of the steel band are joined together after installation and tensioning. The attack ring area pin retainer band TPS did not quite pass the heat load requirements with the .375 in. thick cork TPS as used for the kick ring area band. It is recommended that the cork thickness here be increased to .50 in. The unperturbed area band TPS presented no problems.

Karu, Z. S.↗

DOE OSTI2015

Direct Measurement and Chemical Speciation of Top Ring Zone Liquid During Engine Operation

The present manuscript consists of proof of concept experiments involving direct measurements and detailed chemical speciation from the top ring zone of a running engine. The work uses a naturally aspirated single cylinder utility engine that has been modified to allow direct liquid sample acquisition from behind the top ring. Samples were analyzed and spectated using gas chromatographic techniques. Results show that the liquid mixture in the top ring zone is neither neat lubricant nor fuel but a combination of the two with unique chemical properties. At the tested steady state no-load operating condition, the chemical species of the top ring zone liquid were found to be highly dependent on boiling point, where both low reactivity higher boiling point fuel species and lubricant are observed to be the dominant constituents. The results show that at least for the tested condition, approximately 25% of the top ring zone is comprised of gasoline fuel like molecules, which are dominated by high octane number aromatic species, while the remainder of the liquid is comprised of lubricant like species.

Splitter, Derek A↗

NASA NTRSDate not supplied

Development of A Maximum Anti-Slosh Baffle Pressure Load Model

The sloshing of propellants can affect the stability of a spacecraft and the integrity of the tank structure. Undesirable sloshing can be controlled by the addition of anti-slosh baffles, and the spacing and configuration of baffles are driven by damping requirements. The structural design of the baffle is determined after consideration of many factors, such as the strength and rigidity needed to support the baffle for its lifetime. Therefore, knowledge of distributed pressure loading is important for detailed structural design. In addition, the resultant force and moment produced by the distributed pressure are of direct importance to the design of a vehicle’s control system. Previous experimental investigations have been conducted to determine the liquid pressure loads and slosh damping associated with a rigid ring baffle. The results suggested that when the nondimensional velocity parameter is larger than 1.0, the theories agree with the test. However, when the velocity parameter is less than 1.0, all theories are nonconservative and under-predict the pressure loads. The present study has derived a maximum pressure load on the slosh baffle based on the energy conservation principle. It is verified from CFD that pressure in the slosh flow field can be decomposed into static and transient components. The CFD results confirm that there is a phase shift in pressure across the baffle, which depends on the fluid damping. Higher damping leads to a higher phase shift. The CFD investigation further verifies the proposed theory: the maximum pressure load occurs when the phase shift is 90 degrees. A comparison of the present computational results to the previous comprehensive experimental data validates the maximum pressure theory. When the baffle is submerged, the maximum pressure theory envelopes all the experimental data points.

CFD↗

DOE OSTI2016

Characterization of the High-Speed-Stage Bearing Skidding of Wind Turbine Gearboxes Induced by Dynamic Electricity Grid Events: Preprint

Bearing behavior is an important factor for wind turbine drivetrain reliability. Extreme loads and dynamic excitations pose challenges to the bearing design and therefore its performance. Excessive skidding of the bearing rollers should be avoided because it can cause scuffing failures. Excitations coming from wind and the electricity grid can subject the drivetrain to fluctuating torque and nontorque loads. Wind-induced excitations have been investigated predominantly in literature. However, modern wind turbines are subjected more and more to grid-induced loads because of stricter electricity grid regulations. For example, during fault-ride-through events, turbines are required to stay connected for a longer period of time during the grid failure. This work investigates the influence of electrically induced excitations on the skidding behaviour of the tapered roller bearings on the high-speed stage of a wind turbine gearbox. This skidding behaviour during dynamic events is described as a potential bearing failure initiator by many researchers; however, only limited full-scale dynamic testing is documented. Therefore, a dedicated gridloss-type event is defined in the paper and conducted in a dynamometer test on a full-scale wind turbine nacelle. During the event, a complete electricity grid failure is simulated while the turbine is at rated speed and predefined torque levels. Particular focus is on the characterization of the high-speed shaft tapered roller bearing slip behavior. Strain-gauge bridges in grooves along the circumference of the outer ring are used to characterize the bearing load zone in detail. It is shown that during the torque reversals of the transient event, roller slip can be induced. This indicates the potential of the applied load case to go beyond the preload of the tapered roller bearing. Furthermore, the relation between the applied torque and skidding level is studied.

17 WIND ENERGY↗

DOE OSTI2016

Characterization of the High-Speed-Stage Bearing Skidding of Wind Turbine Gearboxes Induced by Dynamic Electricity Grid Events

17 WIND ENERGY↗

DOE OSTI2015

3-60B Type-B shipping cask enhanced operational features to facilitate leakage rate testing - 15585

EnergySolutions is fabricating a new 3-60B Type B Shipping Cask that will be ready for use in spring 2015, designed for shipping Type B quantities of activated and/or non-fuel-bearing reactor or accelerator components. EnergySolutions, in consult with Leak Testing Specialists, Inc., has implemented an improved design of the 3-60B cask closures to better facilitate periodic and maintenance leakage rate testing and to allow end users to more easily perform pre-shipment leakage rate testing to confirm proper assembly of the cask closures. A typical Type B cask closure lid design incorporates a double O-ring configuration, where the inner O-ring provides containment and the outer O-ring is used for leakage rate testing of the containment O-ring seal. Leakage rate testing of a double O-ring configuration is typically accomplished by filling the cask cavity with helium, pulling a vacuum on the annular space between the two O-rings and monitoring for helium leakage through the containment O-ring. One issue is the potential for helium saturation of the O-ring elastomeric material, which can result in leakage rate test failures. The cask cavity volume is typically large, and takes a significant amount of time to fill with helium. As a result, the saturation time for certain elastomeric compounds may be exceeded, leading to potential false-negative leakage rate testing results. To avoid this, that the cask cavity typically is loaded with sealed container(s) to reduce the free volume and the fill time. The improved 3-60B cask closure lid incorporates a triple O-ring seal configuration that facilitates maintenance leak rate testing of the closure lid containment O-ring seal and eliminates the issues discussed above. The triple O-ring configuration uses the middle O-ring as the containment seal, with the inner and outer test O-rings creating relatively small annular volumes for testing purposes. These small annular volumes are quick to fill, minimizing the issue of Helium saturation of the O-ring material. This seal configuration also makes it possible to detect and replace a damaged O-ring seal during loading operations, or dress a damaged sealing surface, and perform the required maintenance leakage rate testing of the replacement O-ring at the plant site without the need to unload the cask and send it to a maintenance facility. Also, a second test port has been added to each O-ring annulus to allow leakage rate testing to be accomplished using a formal system calibration that complies with the requirements and recommendations of ASME Section V, Article 10 [4], ANSI N14.5-97 [2], and ANSI N14.5-2014 [3]. This provides a simple, reliable, and accurate means to perform leakage rate testing with a test confidence level that cannot be achieved without the second test port. The improved closure and test port design simplifies and shortens the time required to perform leakage testing, resulting in reduced operating costs, greater schedule security, and dose savings for the cask users. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

NASA NTRS1985

Dynamic response of film thickness in spiral-groove face seals

Tests were performed on an inward- and an outward-pumping spiral-groove face seal to experimentally determine the film thickness response to seal seat motions and to gain insight into the effect of secondary seal friction on film thickness behavior. Film thickness, seal seat axial motion, seal frictional torque, and film axial load were recorded as functions of time. The experiments revealed that for sinusoidal axial oscillations of the seal seat, the primary ring followed the seal seat motion very well. For a skewed seal seat, however, the primary ring did not follow the seal seat motion, and load-carrying capacity was degraded. Secondary seal friction was varied over a wide range to determine its effect on film thickness dynamics. The seals were tested with ambient air at room temperature and atmospheric pressure as the fluid medium. The test speed ranged from 7000 to 20,000 rpm. Seal tangential velocity ranged from 34 to 98 m/sec (113 to 323 ft/sec).

Dirusso, E.↗

DOE OSTI2025

ECAR-8823 Rev 0 Structural Evaluation of the MARVEL Support Frame in Dry Critical Configuration

The purpose of this ECAR is to structurally evaluate the MARVEL reactor support frame during the dry critical (DryCrit) start-up testing. The ECAR includes evaluation of the DryCrit configuration for tip-over of the frame during a seismic event, floor loading of the frame on the MFC-720 (TREAT) operating floor, stress analysis of the adapter ring, and stress analysis of the frame itself for gravity and seismic loads.

21 - SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLAN↗

DOE OSTI2013

Multiple piece turbine rotor blade

A multiple piece turbine rotor blade with a shell having an airfoil shape and secured between a spar and a platform with the spar including a tip end piece. a snap ring fits around the spar and abuts against the spar tip end piece on a top side and abuts against a shell on the bottom side so that the centrifugal loads from the shell is passed through the snap ring and into the spar and not through a tip cap dovetail slot and projection structure.

33 ADVANCED PROPULSION SYSTEMS↗

NASA NTRS1974

Inelastic, nonlinear analysis of stiffened shells of revolution by numerical integration

This paper describes the latest addition to the STARS system of computer programs, STARS-2P, for the plastic, large deflection analysis of axisymmetrically loaded shells of revolution. The STARS system uses a numerical integration scheme to solve the governing differential equations. Several unique features for shell of revolution programs that are included in the STARS-2P program are described. These include orthotropic nonlinear kinematic hardening theory, a variety of shell wall cross sections and discrete ring stiffeners, cyclic and nonproportional mechanical and thermal loading capability, the coupled axisymmetric large deflection elasto-plastic torsion problem, an extensive restart option, arbitrary branching capability, and the provision for the inelastic treatment of smeared stiffeners, isogrid, and waffle wall constructions. To affirm the validity of the results, comparisons with available theoretical and experimental data are presented.

Levine, H. S.↗

DOE OSTI2018

Adiabatic shear localization in the CrMnFeCoNi high-entropy alloy

The mechanical behavior of the single phase (fcc) CrMnFeCoNi high-entropy alloy (HEA) is examined in the dynamic regime. Here a series of experiments by dynamic-loading hat-shaped specimens using stopper rings to control the displacement are performed, and the alloy resists adiabatic shear-band formation up to a very large imposed shear strain of ~7. It is proposed that the combination of the excellent strain-hardening ability and moderate thermal-softening effect retard shear localization. Recrystallized ultrafine-grained grains (diameters of 100–300 nm) with twins are revealed inside the shear band. Their formation is explained by the rotational dynamic recrystallization mechanism. The stability of the structure at high strain rates strongly suggests a high ballistic resistance for this class of alloys.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Highly Robust and Efficient Blechert-Type Cyclic(alkyl)(amino)carbene Ruthenium Complexes for Olefin Metathesis

The first Blechert-type ruthenium complexes containing cyclic(alkyl)(amino)carbene (CAAC) ligands are reported. Furthermore, these catalysts demonstrate remarkable thermal stability in solution and excellent catalytic performances at low catalytic loading (up to 0.005 mol%) in ring-closing metathesis (RCM), macro-RCM, ring-closing enyne metathesis (RCEYM), cross-metathesis (CM), ethenolysis and ring-opening cross metathesis (ROCM). Moreover, up to 95% ee was obtained in asymmetric ring-opening cross metathesis (AROCM) and 57% ee asymmetric cross-metathesis (ACM)

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1979

High speed cylindrical rolling element bearing analysis 'CYBEAN' - Analytic formulation

This paper documents the analytic foundation and software architecture for the computerized mathematical simulation of high speed cylindrical rolling element bearing behavior. The software, CYBEAN (CYlindrical BEaring ANalysis), considers a flexible, variable geometry outer ring, EHD films, roller centrifugal and quasidynamic loads, roller tilt and skew, mounting fits, cage and flange interactions. The representation includes both steady state and time transient simulation of thermal interactions internal to and coupled with the surroundings of the bearing. A sample problem illustrating program use is presented.

Kleckner, R. J.↗

NASA NTRS1983

Test Report for MSFC Test No. 83-2: Pressure scaled water impact test of a 12.5 inch diameter model of the Space Shuttle solid rocket booster filament wound case and external TVC PCD

Water impact tests using a 12.5 inch diameter model representing a 8.56 percent scale of the Space Shuttle Solid Rocket Booster configuration were conducted. The two primary objectives of this SRB scale model water impact test program were: 1. Obtain cavity collapse applied pressure distributions for the 8.56 percent rigid body scale model FWC pressure magnitudes as a function of full-scale initial impact conditions at vertical velocities from 65 to 85 ft/sec, horizontal velocities from 0 to 45 ft/sec, and angles from -10 to +10 degrees. 2. Obtain rigid body applied pressures on the TVC pod and aft skirt internal stiffener rings at initial impact and cavity collapse loading events. In addition, nozzle loads were measured. Full scale vertical velocities of 65 to 85 ft/sec, horizontal velocities of 0 to 45 ft/sec, and impact angles from -10 to +10 degrees simulated.

Source record↗