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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Dissimilar Metal Weld Joints of P91/Ni Alloy: Microstructural Characterization of HAZ of P91 and Stress Analysis at the Weld Interfaces

Microstructure evolution and hardness were evaluated at the interface of two friction-welded transition joints between P91 and AISI 304 fabricated applying Inconel interlayers, viz. single-interlayer weld (P91/IN600/AISI304) and three-interlayer weld (P91/IN625/IN600/IN800H/AISI304). The welds were subjected to post-weld heat treatment at 1023 K for 1 h followed by air cooling and a long-term exposure at 973 K for 100, 250, and 500 h. A soft zone with the absence of lath martensite was noticed in both the welds which was located at the intercritical heat-affected zone of the welds. This zone was found to be extending with time toward the fine grain heat-affected zone by carbide precipitation and coarsening at the grain boundaries. Soft zone formation at the interface of the welds was found to be due to carbon diffusion. The presence of high-nickel-content alloy at the interface was proven to be beneficial in stopping carbon diffusion at the interface. Though soft zones existed in both the welds, better creep rupture life was observed for three-interlayer welds. Finite element analysis of these weld joints was performed for thermal loading followed by tensile loading. The results from this analysis indicated that thermal expansion also plays an important role in the failures of these dissimilar weld joints by creating high stress at the interface due to incompatibility.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Development of LWR Fuels with Enhanced Accident Tolerance ATF Feasibility Analysis and Final Technical Report Deliverable for the Westinghouse Accident Tolerant Fuel Program (Rev. 2)

The beyond design basis accident at Fukushima Daiichi in March 2011 and the Three Mile Island accident in 1979 imply that severe nuclear accidents may occur at somewhat higher frequencies than previously predicted, and that the financial liabilities of such accidents can cripple a utility. While current fuel is more than adequate for design basis accidents, the potential for harm from beyond design basis accidents (BDBA) has been a driver for Westinghouse development efforts since 2003. After Fukushima, other fuel vendors also began pursuing new fuel materials that can provide significant increases in the time, enabling reactor operators to respond to unforeseen events before significant releases of fuel materials and fission products occur. In order to be commercially successful, accident tolerant fuel (ATF) products must also provide significant fuel cost savings, operating cost improvements as well as safety improvements. This report documents the engineering, design and testing that occurred from October 1, 2016, through September 30, 2018, by the Westinghouse team. In addition, it includes: 1. The results of modeling and simulation work completed to date that supports technical feasibility of the ATF concept in meeting the goals of the enhanced ATF program including a core level analysis predicting how an existing LWR will perform when loaded with ATF. 2. Regulatory Analysis showing path to LTA/LTR acceptance. 3. Business Analysis showing commercial viability of the ATF concept.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1984

Calculation of transonic flow in a linear cascade

Turbomachinery blade designs are becoming more aggressive in order to achieve higher loading and greater range. New analysis tools are required to cope with these heavily loaded blades that may operate with a thin separated region near the trailing edge on the suction surface. An existing, viscous airfoil code was adapted to cascade conditions in an attempt to provide this capability. Comparisons with recently obtained data show that calculated and experimental surface Mach numbers were in good agreement but loss coefficients and outlet air angles were not.

Donovan, L. F.↗
NASA NTRS1984

Calculation of transonic flow in a linear cascade

Turbomachinery blade designs are becoming more aggressive in order to achieve higher loading and greater range. New analysis tools are required to cope with these heavily loaded blades that may operate with a thin separated region near the trailing edge on the suction surface. An existing, viscous airfoil code was adapted to cascade conditions in an attempt to provide this capability. Comparisons with recently obtained data show that calculated and experimental surface Mach numbers were in good agreement but loss coefficients and outlet air angles were not. Previously announced in STAR as N84-24539

Donovan, L. F.↗
NASA NTRS1976

Minimum trim drag design for interfering lifting surfaces using vortex-lattice methodology

A new method has been developed by which the mean camber surface can be determined for trimmed noncoplanar planforms with minimum vortex drag under subsonic conditions. The method uses a vortex lattice and overcomes previous difficulties with chord loading specification; it uses a Trefftz plane analysis to determine the optimum span loading for minimum drag, then solves for the mean camber surface of the wing which will provide the required loading. Pitching-moment or root-bending-moment constraints can be employed as well at the design lift coefficient. Sensitivity studies of vortex-lattice arrangement have been made with this method and are presented. Comparisons with other theories show generally good agreement. The versatility of the method is demonstrated by applying it to (1) isolated wings, (2) wing-canard configurations, (3) a tandem wing, and (4) a wing-winglet configuration.

Lamar, J. E.↗
NASA NTRS1986

Unsteady forces on counter-rotating propeller blades

Unsteady forces experienced by counter-rotating propeller blades are examined in this paper. A fully coupled vortex lattice model of counter-rotation is used to obtain a quasi-steady solution to the propeller loadings, and an unsteady Sears (1941) analysis provides an estimate of the unsteady loads from the quasi-steady results. The vortex lattice method predicts the overall performance of counter-rotation well, based on comparisons of measured and predicted results. The effects of propeller spacing and blade number on the unsteady loadings are investigated. The peak-to-peak variation about the mean of the unsteady loads on the rear propeller varied from 9 percent for a 2 x 2 counter-rotation system to 2 percent for an 8 x 8 system.

Lesieutre, D. J.↗
DOE OSTI2021

Analysis of the Amorphous and Interphase Influence of Comononomer Loading on Polymer Properties toward Forwarding Bioadvantaged Copolyamides

In this paper we present an approach for selectively modifying the properties of semicrystalline polymers by introducing “bioadvantaged” counits. With this approach, the unique functionality of biomass can be leveraged to tailor the properties of the amorphous phase of semicrystalline polymers with minimal impact on crystallinity and thermomechanical properties. As a model case, PA 6,6 copolyamides were produced using the bioadvantaged monomer trans-3-hexenedioic acid (t3HDA). The analogous structure of t3HDA to adipic acid, a PA 6,6 monomer, allows for seamless integration. Screening over the entire composition range identified the t3HDA loading (20 mol%) beyond which properties deviate appreciably from Nylon 6,6. Once identified, copolyamides of suitable compositions were upgraded to commercial quality and fully characterized to assess the influence of counit loading and polymer structure on thermal and mechanical properties. Samples were characterized using gel permeation chromatography (GPC), proton nuclear magnetic resonance spectroscopy (1H NMR), heteronuclear single quantum coherence spectroscopy (HSQC), wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), tensile testing, flexural testing, and water absorption testing. t3HDA units were shown to hydrate during the harsh polycondensation to 3-hydroxyhexanedioic acid (3HHDA) and fully incorporate into the polymer backbone. Loading levels up to 20% were shown to have comparable thermal and mechanical properties in the dry state, yet moisture absorption—a known method for improving the toughness, yield strain, and elongation of polyamides—was enhanced by over 100% at 20% loading. This case study on bioadvantaged copolymers elucidates the governing structure-function principles that can be leveraged to forward value-added renewable polymers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Thermal Evaluation of the SAVY-4000 1 Quart Container at High Heat Loads

The SAVY-4000 Safety Analysis Report (SAR) was published in 2013 which established the design life of the container series through physical testing that meets applicable requirements from DOE M 441.1-1, Nuclear Material Packaging Manual. One critical requirement in DOE M 441.1-1 is to set a maximum heat load for the entire series to ensure that throughout the lifetime of the container, each of the components still performs within manufacture specifications. The original maximum decay heat limit has been defined within the SAVY-4000 SAR, which was accomplished by completing a series of tests that heat loaded the SAVY-4000 series and measured the steady state temperature and graded it against manufacture specifications. The container series is comprised of a corrosion resistant 316L stainless steel containment boundary, ceramic composite filter for the prevention of radiological particulate release and a chemically stable O-ring made of Viton ® . Currently, the SAVY 4000 maximum decay heat load is set at 25 Watts and the heat load expected during normal handling and storage is considered sufficient that the SAVY 4000 container requirements will not be the limiting factor for storage of most common material in use at TA-55, e.g. weapons grade oxide, americium, Pu-238 oxide and encapsulated heat sources. The SAVY 4000 lifetime was originally set as 5 years within the SAVY-4000 SAR, but in July 2019 the lifetime was extended to 15 years through a technical basis justification approved by the Department of Energy (DOE) Los Alamos Field Office. The 25 Watt limit applies to all SAVY 4000 container sizes; 1-quart, 2-quart, 3-quart, 5-quart, 8-quart, 12-quart, 5-gallon, and 10-gallon.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1992

Microcracking, microcrack-induced delamination, and longitudinal splitting of advanced composite structures

A combined analytical and experimental study was conducted to analyze microcracking, microcrack-induced delamination, and longitudinal splitting in polymer matrix composites. Strain energy release rates, calculated by a variational analysis, were used in a failure criterion to predict microcracking. Predictions and test results were compared for static, fatigue, and cyclic thermal loading. The longitudinal splitting analysis accounted for the effects of fiber bridging. Test data are analyzed and compared for longitudinal splitting and delamination under mixed-mode loading. This study emphasizes the importance of using fracture mechanics analyses to understand the complex failure processes that govern composite strength and life.

Nairn, John A.↗
DOE OSTI2013

Minimization of Impact from Electric Vehicle Supply Equipment to the Electric Grid Using a Dynamically Controlled Battery Bank for Peak Load Shaving

This research presents a comparison of two control systems for peak load shaving using local solar power generation (i.e., photovoltaic array) and local energy storage (i.e., battery bank). The purpose is to minimize load demand of electric vehicle supply equipment (EVSE) on the electric grid. A static and dynamic control system is compared to decrease demand from EVSE. Static control of the battery bank is based on charging and discharging to the electric grid at fixed times. Dynamic control, with 15-minute resolution, forecasts EVSE load based on data analysis of collected data. In the proposed dynamic control system, the sigmoid function is used to shave peak loads while limiting scenarios that can quickly drain the battery bank. These control systems are applied to Oak Ridge National Laboratory s (ORNL) solar-assisted electric vehicle (EV) charging stations. This installation is composed of three independently grid-tied sub-systems: (1) 25 EVSE; (2) 47 kW photovoltaic (PV) array; and (3) 60 kWh battery bank. The dynamic control system achieved the greatest peak load shaving, up to 34% on a cloudy day and 38% on a sunny day. The static control system was not ideal; peak load shaving was 14.6% on a cloudy day and 12.7% on a sunny day. Simulations based on ORNL data shows solar-assisted EV charging stations combined with the proposed dynamic battery control system can negate up to 89% of EVSE load demand on sunny days.

Battery Management Systems↗
NASA NTRS1990

Ply-level failure analysis of a graphite/epoxy laminate under bearing-bypass loading

A combined experimental and analytical study was conducted to investigate and predict the failure modes of a graphite/epoxy laminate subjected to combined bearing and bypass loading. Tests were conducted in a test machine that allowed the bearing-bypass load ratio to be controlled while a single-fastener coupon was loaded to failure in either tension or compression. Onset and ultimate failure modes and strengths were determined for each test case. The damage-onset modes were studied in detail by sectioning and micrographing the damaged specimens. A two-dimensional, finite-element analysis was conducted to determine lamina strains around the bolt hole. Damage onset consisted of matrix cracks, delamination, and fiber failures. Stiffness loss appeared to be caused by fiber failures rather than by matrix cracking and delamination. An unusual offset-compression mode was observed for compressive bearing-bypass loading in which the specimen failed across its width along a line offset from the hole. The computed lamina strains in the fiber direction were used in a combined analytical and experimental approach to predict bearing-bypass diagrams for damage onset from a few simple tests.

Naik, R. A.↗
DOE OSTI2021

Asynchronous and Load-Balanced Union-Find for Distributed and Parallel Scientific Data Visualization and Analysis

We present a novel distributed union-find algorithm that features asynchronous parallelism and k-d tree based load balancing for scalable visualization and analysis of scientific data. Applications of union-find include level set extraction and critical point tracking, but distributed union-find can suffer from high synchronization costs and imbalanced workloads across parallel processes. In this study, we prove that global synchronizations in existing distributed union-find can be eliminated without changing final results, allowing overlapped communications and computations for scalable processing. We also use a k-d tree decomposition to redistribute inputs, in order to improve workload balancing. We benchmark the scalability of our algorithm with up to 1,024 processes using both synthetic and application data. Here, we demonstrate the use of our algorithm in critical point tracking and super-level set extraction with high-speed imaging experiments and fusion plasma simulations, respectively.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1987

Thermo-elasto-viscoplastic analysis of problems in extension and shear

The problems of extension and shear behavior of structural elements made of carbon steel and subjected to large thermomechanical loads are investigated. The analysis is based on nonlinear geometric and constitutive relations, and is expressed in a rate form. The material constitutive equations are capable of reproducing all nonisothermal, elasto-viscoplastic characteristics. The results of the test problems show that: (1) the formulation can accommodate very large strains and rotations; (2) the model incorporates the simplification associated with rate-insensitive elastic response without losing the ability to model a rate-temperature dependent yield strength and plasticity; and (3) the formulation does not display oscillatory behavior in the stresses for the simple shear problem.

Riff, R.↗
NASA NTRS1988

Thermo-elasto-viscoplastic analysis of problems in extension and shear

The problems of extension and shear behavior of structural elements made of carbon steel and subjected to large thermomechanical loads are investigated. The analysis is based on nonlinear geometric and constitutive relations, and is expressed in a rate form. The material constitutive equations are capable of reproducing all nonisothermal, elasto-viscoplastic characteristics. The results of the test problems show that: (1) the formulation can accommodate very large strains and rotations; (2) the model incorporates the simplification associated with rate-insensitive elastic response without losing the ability to model a rate-temperature dependent yield strength and plasticity; and (3) the formulation does not display oscillatory behavior in the stresses for the simple shear problem.

Riff, R.↗
NASA NTRS1957

Motion of a ballistic missile angularly misaligned with the flight path upon entering the atmosphere and its effect upon aerodynamic heating, aerodynamic loads, and miss distance

An analysis is given of the oscillating motion of a ballistic missile which upon entering the atmosphere is angularly misaligned with respect to the flight path. The history of the motion for some example missiles is discussed from the point of view of the effect of the motion on the aerodynamic heating and loading. The miss distance at the target due to misalignment and to small accidental trim angles is treated. The stability problem is also discussed for the case where the missile is tumbling prior to atmospheric entry.

Allen, Julian H↗
NASA NTRS1993

Further studies using matched filter theory and stochastic simulation for gust loads prediction

This paper describes two analysis methods - one deterministic, the other stochastic - for computing maximized and time-correlated gust loads for aircraft with nonlinear control systems. The first method is based on matched filter theory; the second is based on stochastic simulation. The paper summarizes the methods, discusses the selection of gust intensity for each method and presents numerical results. A strong similarity between the results from the two methods is seen to exist for both linear and nonlinear configurations.

Scott, Robert C.↗