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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Features for a Modern Strain-Gage Balance Data Analysis Software Tool

Required, recommended, and optional features are discussed that benefit preparation and evaluation of the load prediction equations in a strain-gage balance data analysis tool. First, milestones in the evolution of load prediction methods are reviewed so that suggested features can be put into a historical context. Afterwards, independent and dependent variable choices for the balance data analysis are discussed. Then, it is illustrated how three different metrics may be used for the identification of the root cause of an unwanted divergence of the load iterations that may be observed during an iterative load prediction. Finally, a list of features is provided to guide software development efforts.

wind tunnel test↗
NASA NTRS1991

Advanced Rotorcraft Transmission (ART) program status

Reported herein is work done on the Advanced Rotorcraft Transmission by McDonnell Douglas Helicopter Company under Army/NASA contract. The novel concept pursued includes the use of face gears for power transmission and a torque splitting arrangement. The design reduces the size and weight of the corner-turning hardware and the next reduction stage. New methods of analyzing face gears have increased confidence in their usefulness. Test gears have been designed and manufactured for power transmission testing on the NASA-Lewis spiral bevel test rig. Transmission design effort has included finite element modeling of the split torque paths to assure equal deflection under load. A finite element model of the Apache main transmission has been completed to substantiate noise prediction methods. A positive engagement overrunning clutch design is described. Test spur gears have been made by near-net-shape forging from five different materials. Three housing materials have been procured for evaluation testing.

Bossler, Robert↗
NASA NTRS2012

Advanced Model for Extreme Lift and Improved Aeroacoustics (AMELIA)

With the very recent advent of NASA's Environmentally Responsible Aviation Project (ERA), which is dedicated to designing aircraft that will reduce the impact of aviation on the environment, there is a need for research and development of methodologies to minimize fuel burn, emissions, and reduce community noise produced by regional airliners. ERA tackles airframe technology, propulsion technology, and vehicle systems integration to meet performance objectives in the time frame for the aircraft to be at a Technology Readiness Level (TRL) of 4-6 by the year of 2020 (deemed N+2). The proceeding project that investigated similar goals to ERA was NASA's Subsonic Fixed Wing (SFW). SFW focused on conducting research to improve prediction methods and technologies that will produce lower noise, lower emissions, and higher performing subsonic aircraft for the Next Generation Air Transportation System. The work provided in this investigation was a NASA Research Announcement (NRA) contract #NNL07AA55C funded by Subsonic Fixed Wing. The project started in 2007 with a specific goal of conducting a large-scale wind tunnel test along with the development of new and improved predictive codes for the advanced powered-lift concepts. Many of the predictive codes were incorporated to refine the wind tunnel model outer mold line design. The large scale wind tunnel test goal was to investigate powered lift technologies and provide an experimental database to validate current and future modeling techniques. Powered-lift concepts investigated were Circulation Control (CC) wing in conjunction with over-the-wing mounted engines to entrain the exhaust to further increase the lift generated by CC technologies alone. The NRA was a five-year effort; during the first year the objective was to select and refine CESTOL concepts and then to complete a preliminary design of a large-scale wind tunnel model for the large scale test. During the second, third, and fourth years the large-scale wind tunnel model design would be completed, manufactured, and calibrated. During the fifth year the large scale wind tunnel test was conducted. This technical memo will describe all phases of the Advanced Model for Extreme Lift and Improved Aeroacoustics (AMELIA) project and provide a brief summary of the background and modeling efforts involved in the NRA. The conceptual designs considered for this project and the decision process for the selected configuration adapted for a wind tunnel model will be briefly discussed. The internal configuration of AMELIA, and the internal measurements chosen in order to satisfy the requirements of obtaining a database of experimental data to be used for future computational model validations. The external experimental techniques that were employed during the test, along with the large-scale wind tunnel test facility are covered in great detail. Experimental measurements in the database include forces and moments, and surface pressure distributions, local skin friction measurements, boundary and shear layer velocity profiles, far-field acoustic data and noise signatures from turbofan propulsion simulators. Results and discussion of the circulation control performance, over-the-wing mounted engines, and the combined performance are also discussed in great detail.

Subsonic Fixed Wing↗
NASA NTRS1981

NASA progress in aircraft noise prediction

Langley Research Center efforts to develop a methodology for predicting the effective perceived noise level (EPNL) produced by jet-powered CTOL aircraft to an accuracy of + or - 1.5 dB are summarized with emphasis on the aircraft noise prediction program (ANOPP) which contains a complete set of prediction methods for CTOL aircraft including propulsion system noise sources, aerodynamic or airframe noise sources, forward speed effects, a layered atmospheric model with molecular absorption, ground impedance effects including excess ground attenuation, and a received noise contouring capability. The present state of ANOPP is described and its accuracy and applicability to the preliminary aircraft design process is assessed. Areas are indicated where further theoretical and experimental research on noise prediction are needed. Topics covered include the elements of the noise prediction problem which are incorporated in ANOPP, results of comparisons of ANOPP calculations with measured noise levels, and progress toward treating noise as a design constraint in aircraft system studies.

Raney, J. P.↗
NASA NTRS1991

The application of experimental data to blade wake interaction noise prediction

Blade wake interaction noise (BWI) has been defined as the broadband noise generated by the ingestion of turbulent trailing tip vortices by helicopter rotors. This has been shown to be the dominant contributor to the subjectively important part of the acoustic spectrum for the approach stage of a helicopter flyover. A prediction method for BWI noise based on the calculated trailing vortex trajectories has been developed and estimates of the vortex turbulence have been made. These measurements were made on a trailing vortex from a split wing arrangement and did not give the spectrum of the velocity fluctuations. A recent experiment carried out to measure the turbulence associated with a trailing vortex and the application of the results to BWI noise prediction is described.

Glegg, Stewart A. L.↗
NASA NTRS2018

Effects of Version 2 of the International Sunspot Number on Naive Predictions of Solar Cycle 25

The recalibration of the International Sunspot Number brings new challenges to predictions of Solar Cycle 25. One is that the list of extrema for the original series is no longer usable because the values of all maxima and minima are different for the new version of the sunspot number. Timings of extrema are less sensitive to the recalibration but are a natural result of the calculation. Predictions of Solar Cycle 25 published before 2016 must be converted to the new version of the sunspot number. Any prediction method that looks across the entire time span will have to be reconsidered because values in the nineteenth century were corrected by a larger factor than those in the twentieth century. We report a list of solar maxima and minima values and timings based on the recalibrated sunspot number. Naïve forecasts that depend only on the current values of the time series are common in economic studies. Several naïve predictions of Solar Cycle 25, the climatological average (180 ± 60), two versions of the inertial forecast, and two versions of the even-odd forecast, are derived from that table. The climatological average forecast is the baseline for more accurate predictions and the initial forecast in assimilative models of the Sun. It also provides the error estimate for Monte Carlo techniques that anticipate the long-term effects on the terrestrial environment. The other four predictions are shown to be statistically insignificant.

Pesnell, W. Dean↗
NASA NTRS1988

Life prediction modeling based on strainrange partitioning

Strainrange partitioning (SRP) is an integrated low-cycle-fatigue life predicting system. It was created specifically for calculating cyclic crack initiation life under severe high-temperature fatigue conditions. The key feature of the SRP system is its recognition of the interacting mechanisms of cyclic inelastic deformation that govern cyclic life at high temperatures. The SRP system bridges the gap between the mechanistic level of understanding that breeds new and better materials and the phenomenological level wherein workable engineering life prediction methods are in great demand. The system was recently expanded to address engineering fatigue problems in the low-strain, long-life, nominally elastic regime. This breakthrough, along with other advances in material behavior and testing technology, has permitted the system to also encompass low-strain thermomechanical loading conditions. Other important refinements of the originally proposed method include procedures for dealing with life-reducing effects of multiaxial loading, ratcheting, mean stresses, nonrepetitive (cumulative loading) loading, and environmental and long-time exposure. Procedure were also developed for partitioning creep and plastic strain and for estimating strainrange versus life relations from tensile and creep rupture properties. Each of the important engineering features of the SRP system are discussed and examples shown of how they help toward predicting high-temperature fatigue life under practical, although complex, loading conditions.

Halford, Gary R.↗
NASA NTRS1990

Conversion of piston-driven shocks from powerful solar flares to blast waves in the solar wind

Published observational data on 39 combined type-II/type-IV solar radio bursts from the period 1972-1982 are analyzed, with a focus on the potential use of the type-IV burst duration to predict the time of arrival at earth of piston-driven shock waves (extending and modifying the prediction method proposed by Smart and Shea, 1985). The data and analysis results are presented in tables and graphs and characterized in detail. It is found that a typical shock of this type leaves the solar flare at velocity 1560 km/sec and continues for a distance of 0.12 AU, decelerates as it is convected by the solar wind, and has a travel time of about 48.5 h. The mean deviation between predicted and measured arrival times is 1.40 h, with standard deviation 1.25 h.

Pinter, S.↗
NASA NTRS1996

A Database for Propagation Models and Conversion to C++ Programming Language

The telecommunications system design engineer generally needs the quantification of effects of the propagation medium (definition of the propagation channel) to design an optimal communications system. To obtain the definition of the channel, the systems engineer generally has a few choices. A search of the relevant publications such as the IEEE Transactions, CCIR's, NASA propagation handbook, etc., may be conducted to find the desired channel values. This method may need excessive amounts of time and effort on the systems engineer's part and there is a possibility that the search may not even yield the needed results. To help the researcher and the systems engineers, it was recommended by the conference participants of NASA Propagation Experimenters (NAPEX) XV (London, Ontario, Canada, June 28 and 29, 1991) that a software should be produced that would contain propagation models and the necessary prediction methods of most propagation phenomena. Moreover, the software should be flexible enough for the user to make slight changes to the models without expending a substantial effort in programming. In the past few years, a software was produced to fit these requirements as best as could be done. The software was distributed to all NAPEX participants for evaluation and use, the participant reactions, suggestions etc., were gathered and were used to improve the subsequent releases of the software. The existing database program is in the Microsoft Excel application software and works fine within the guidelines of that environment, however, recently there have been some questions about the robustness and survivability of the Excel software in the ever changing (hopefully improving) world of software packages.

Kantak, Anil V.↗
DOE OSTI2022

Atomically thin interlayer phase from first principles enables defect-free incommensurate SnO2/CdTe interface

Advancing optoelectronic and emerging technologies increasingly requires control and design of interfaces between dissimilar materials. However, incommensurate interfaces are notoriously defective and rarely benefit from first-principles predictions, because no explicit atomic-structure models exist. Here, we adopt a bulk crystal structure prediction method to the interface geometry and apply it to SnO2/CdTe heterojunctions without and with the addition of CdCl2, a ubiquitous and beneficial, but abstruse processing step in CdTe photovoltaics. Whereas the direct SnO2/CdTe interface is highly defective, we discover a unique two-dimensional CdCl2 interphase, unrelated to the respective bulk structure. It facilitates a seamless transition from the rutile to zincblende lattices and removes defect-states from the interface bandgap. Implementing the predicted interface electronic structure in device simulations, we demonstrate the theoretical feasibility of bufferless oxide-CdTe heterojunction solar cells approaching the Shockley–Queisser limit. Our results highlight the broader potential of designing atomically thin interlayers to enable defect-free incommensurate interfaces.

14 SOLAR ENERGY↗
NASA NTRS1986

Helicopter rotor noise due to ingestion of atmospheric turbulence

A theoretical study was conducted to develop an analytical prediction method for helicopter main rotor noise due to the ingestion of atmospheric turbulence. This study incorporates an atmospheric turbulence model, a rotor mean flow contraction model and a rapid distortion turbulence model which together determine the statistics of the non-isotropic turbulence at the rotor plane. Inputs to the combined mean inflow and turbulence models are controlled by atmospheric wind characteristics and helicopter operating conditions. A generalized acoustic source model was used to predict the far field noise generated by the non-isotropic flow incident on the rotor. Absolute levels for acoustic spectra and directivity patterns were calculated for full scale helicopters, without the use of empirical or adjustable constants. Comparisons between isotropic and non-isotropic turbulence at the rotor face demonstrated pronounced differences in acoustic spectra. Turning and contraction of the flow for hover and low speed vertical ascent cases result in a 3 dB increase in the acoustic spectrum energy and a 10 dB increase in tone levels. Compared to trailing edge noise, turbulence ingestion noise is the dominant noise mechanism below approximately 30 rotor harmonics, while above 100 harmonics, trailing edge noise levels exceed turbulence ingestion noise by 25 dB.

Simonich, J. C.↗
NASA NTRS1985

The use of a panel code on high lift configurations of a swept forward wing

A study was done on high lift configurations of a generic swept forward wing using a panel code prediction method. A survey was done of existing codes available at Ames, frow which the program VSAERO was chosen. The results of VSAERO were compared with data obtained from the Ames 7- by 10-foot wind tunnel. The results of the comparison in lift were good (within 3.5%). The comparison of the pressure coefficients was also good. The pitching moment coefficients obtained by VSAERO were not in good agreement with experiment. VSAERO's ability to predict drag is questionable and cannot be counted on for accurate trends. Further studies were done on the effects of a leading edge glove, canards, leading edge sweeps and various wing twists on spanwise loading and trim lift with encouraging results. An unsuccessful attempt was made to model spanwise blowing and boundary layer control on the trailing edge flap. The potential results of VSAERO were compared with experimental data of flap deflections with boundary layer control to check the first order effects.

Scheib, J. S.↗
DOE OSTI2020

A Thermodynamic Reassessment of Lithium-Ion Battery Cathode Calorimetry

This work demonstrates how staged heat release from layered metal oxide cathodes in the presence of organic electrolytes can be predicted from basic thermodynamic properties. These prediction methods for heat release are an advancement compared to typical modeling approaches for thermal runaway in lithium-ion batteries, which tend to rely exclusively on calorimetry measurements of battery components. These calculations generate useful new insights when compared to calorimetry measurements for lithium cobalt oxide (LCO) as well as the most common varieties of nickel manganese cobalt oxide (NMC) and nickel cobalt aluminum oxide (NCA). Accurate trends in heat release with varying state of charge are predicted for all of these cathode materials. These results suggest that thermodynamic calculations utilizing a recently published database of properties are broadly applicable for predicting decomposition behavior of layered metal oxide cathodes. Aspects of literature calorimetry measurements relevant to thermal runaway modeling are identified and classified as thermodynamic or kinetic effects. The calorimetry measurements reviewed in this work will be useful for development of a new generation of thermal runaway models targeting applications where accurate maximum cell temperatures are required to predict cascading cell-to-cell propagation rates.

25 ENERGY STORAGE↗
NASA NTRS1992

An introduction to high speed aircraft noise prediction

The Aircraft Noise Prediction Program's High Speed Research prediction system (ANOPP-HSR) is introduced. This mini-manual is an introduction which gives a brief overview of the ANOPP system and the components of the HSR prediction method. ANOPP information resources are given. Twelve of the most common ANOPP-HSR control statements are described. Each control statement's purpose and format are stated and relevant examples are provided. More detailed examples of the use of the control statements are presented in the manual along with ten ANOPP-HSR templates. The purpose of the templates is to provide the user with working ANOPP-HSR programs which can be modified to serve particular prediction requirements. Also included in this manual is a brief discussion of common errors and how to solve these problems. The appendices include the following useful information: a summary of all ANOPP-HSR functional research modules, a data unit directory, a discussion of one of the more complex control statements, and input data unit and table examples.

Wilson, Mark R.↗
NASA NTRS1991

Fatigue life prediction of an intermetallic matrix composite at elevated temperatures

A strain-based fatigue life prediction method is proposed for an intermetallic matrix composite (IMC) under tensile cyclic loadings at elevated temperatures. Styled after the Universal Slopes method, the model utilizes the composite's tensile properties to estimate fatigue life. Factors such as fiber volume ratio, number of plys and temperature dependence are implicitly incorporated into the model through these properties. The model constants are determined by using unidirectional fatigue data at temperatures of 425 and 815 C. Fatigue lives from two independent sources are used to verify the model at temperatures of 650 and 760 C. Cross-ply lives at 760 C are also predicted. It is demonstrated that the correlation between experimental and predicted lives is within a factor of two.

Bartolotta, Paul A.↗
NASA NTRS1982

Application of an airfoil stall flutter computer prediction program to a three-dimensional wing: Prediction versus experiment

An aerodynamic computer code, capable of predicting unsteady and C sub m values for an airfoil undergoing dynamic stall, is used to predict the amplitudes and frequencies of a wing undergoing torsional stall flutter. The code, developed at United Technologies Research Corporation (UTRC), is an empirical prediction method designed to yield unsteady values of normal force and moment, given the airfoil's static coefficient characteristics and the unsteady aerodynamic values, alpha, A and B. In this experiment, conducted in the PSU 4' x 5' subsonic wind tunnel, the wing's elastic axis, torsional spring constant and initial angle of attack are varied, and the oscillation amplitudes and frequencies of the wing, while undergoing torsional stall flutter, are recorded. These experimental values show only fair comparisons with the predicted responses. Predictions tend to be good at low velocities and rather poor at higher velocities.

Muffoletto, A. J.↗
NASA NTRS1991

Fatigue life prediction of an intermetallic matrix composite at elevated temperatures

A strain-based fatigue life prediction method is proposed for an intermetallic matrix composite (IMC) under tensile cyclic loadings at elevated temperatures. Styled after the 'Universal Slopes' method, the model utilizes the composite's tensile properties to estimate fatigue life. Factors such as fiber volume ratio (Vf), number of plys and temperature dependence are implicitly incorporated into the model through these properties. The model constants are determined by using unidirectional fatigue data at temperatures of 425 and 815 C. Fatigue lives from two independent sources are used to verify the model at temperatures of 650 and 760 C. Cross-ply lives at 760 C are also predicted. It is demonstrated that the correlation between experimental and predicted lives is within a factor of two.

Bartolotta, P. A.↗
DOE OSTI2025

Prediction of carbon nanostructure mechanical properties and the role of defects using machine learning

Graphene-based nanostructures hold immense potential as strong and lightweight materials, however, their mechanical properties such as modulus and strength are difficult to fully exploit due to challenges in atomic-scale engineering. This study presents a database of over 2,000 pristine and defective nanoscale CNT bundles and other graphitic assemblies, inspired by microscopy, with associated stress–strain curves from reactive molecular dynamics (MD) simulations using the reactive INTERFACE force field (IFF-R). These 3D structures, containing up to 80,000 atoms, enable detailed analyses of structure-stiffness-failure relationships. By leveraging the database and physics- and chemistry-informed machine learning (ML), accurate predictions of elastic moduli and tensile strength are demonstrated at speeds 1,000 to 10,000 times faster than efficient MD simulations. Hierarchical Graph Neural Networks with Spatial Information (HS-GNNs) are introduced, which integrate chemistry knowledge. HS-GNNs as well as extreme gradient boosted trees (XGBoost) achieve forecasts of mechanical properties of arbitrary carbon nanostructures with only 3 to 6% mean relative error. The reliability equals experimental accuracy and is up to 20 times higher than other ML methods. Predictions maintain 8 to 18% accuracy for large CNT bundles, CNT junctions, and carbon fiber cross-sections outside the training distribution. The physics- and chemistry-informed HS-GNN works remarkably well for data outside the training range while XGBoost works well with limited training data inside the training range. The carbon nanostructure database is designed for integration with multimodal experimental and simulation data, scalable beyond 100 nm size, and extendable to chemically similar compounds and broader property ranges. The ML approaches have potential for applications in structural materials, nanoelectronics, and carbon-based catalysts.

Winetrout, Jordan J.↗