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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 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Structural weights analysis of advanced aerospace vehicles using finite element analysis

A conceptual/preliminary level structural design system has been developed for structural integrity analysis and weight estimation of advanced space transportation vehicles. The system includes a three-dimensional interactive geometry modeler, a finite element pre- and post-processor, a finite element analyzer, and a structural sizing program. Inputs to the system include the geometry, surface temperature, material constants, construction methods, and aerodynamic and inertial loads. The results are a sized vehicle structure capable of withstanding the static loads incurred during assembly, transportation, operations, and missions, and a corresponding structural weight. An analysis of the Space Shuttle external tank is included in this paper as a validation and benchmark case of the system.

Bush, Lance B.↗
NASA NTRS1987

Analysis of structures with rotating, flexible substructures applied to rotorcraft aeroelasticity in GRASP

Application to the General Rotorcraft Aeromechanical Stability Program (GRASP) of new methodology for structural dynamic analysis, including substructuring, frames of reference, nodes, finite elements, and constraints, is discussed. The structure is decomposed into a hierarchy of substructures, and discrete relative motion between substructures is analyzed exactly. The finite element method is used to treat deformation of continua, and the library of finite elements includes a nonlinear beam element incorporating aeroelastic effects. Analytical bases for the aeroelastic beam element and the screw constraint are considered, and the important role of geometric stiffness in the formulation is shown.

Hodges, Dewey H.↗
NASA NTRS1980

Turbine blade structural dynamic analysis

The paper presents structural dynamic analysis and test results for the Space Shuttle Main Engine turbine blades. Athough these blades are designed to avoid coincidence of natural frequencies with harmonic excitation forces, the complexity of the turbine hardware, its nonlinearities and lack of information regarding the forcing function have led to fatigue failures. A comparison of single-blade analysis and test modal frequencies, shapes, and stresses is given; analysis techniques to describe the forcing function, compute dynamic responses, and incorporate the nonlinearities of Coulomb-friction dampers are presented. Recommendations are made for new research to improve forcing function computations and structural damping estimates used in the analysis.

Dickerson, E. O.↗
NASA NTRS1974

Conical isogrid adapter structural test results. Appendix C: Cylindrical isogrid structures

Analysis techniques and data for evaluating the load carrying capabilities of cylindrical isogrid structures subjected to compression and body bending loads are presented. Structural tests were conducted on a 120-inch diameter by 37-inch long cylindrical adapter. Photographs and drawings of the flanged isogrid adapter structure are included. The subjects considered are: (1) summary of the test data resulting from structural analysis, (2) techniques for predicting local and general instability, (3) a method for predicting extended local instability, (4) the effects of basic parameter and constant variations in extended local stability analysis, and (5) evaluation of effective skin width and compression buckling of skin panels on the basis of test data.

Source record↗
NASA NTRS1991

Probabilistic analysis of structures involving random stress-strain behavior

The present methodology for analysis of structures with random stress strain behavior characterizes the uniaxial stress-strain curve in terms of (1) elastic modulus, (2) engineering stress at initial yield, (3) initial plastic-hardening slope, (4) engineering stress at point of ultimate load, and (5) engineering strain at point of ultimate load. The methodology is incorporated into the Numerical Evaluation of Stochastic Structures Under Stress code for probabilistic structural analysis. The illustrative problem of a thick cylinder under internal pressure, where both the internal pressure and the stress-strain curve are random, is addressed by means of the code. The response value is the cumulative distribution function of the equivalent plastic strain at the inner radius.

Millwater, H. R.↗
DOE OSTI2015

Aquantis 2.5 MW Ocean Current Generation Device - Scaled Tank Test Design and Results

Aquantis 2.5 MW Ocean Current Generation Device, Tow Tank Dynamic Rig Structural Analysis Results. This is the detailed documentation for scaled device testing in a tow tank, including models, drawings, presentations, cost of energy analysis, and structural analysis. This dataset also includes specific information on drivetrain, roller bearing, blade fabrication, mooring, and rotor characteristics.

16 TIDAL AND WAVE POWER↗
NASA NTRS1975

Interactive computer graphics system for structural sizing and analysis of aircraft structures

A computerized system for preliminary sizing and analysis of aircraft wing and fuselage structures was described. The system is based upon repeated application of analytical program modules, which are interactively interfaced and sequence-controlled during the iterative design process with the aid of design-oriented graphics software modules. The entire process is initiated and controlled via low-cost interactive graphics terminals driven by a remote computer in a time-sharing mode.

Bendavid, D.↗
NASA NTRS1981

Elevated temperature fatigue testing of metals

Material characterization and evaluation conducted for the purpose of calculating fatigue crack initiation lives of components operating at elevated temperatures are discussed. The major technology areas needed to perform a life prediction of an aircraft turbine engine hot section component and the steps required for life prediction are outlined. These include: the determination of the operating environment, the calculation of the thermal and mechanical loading of the component, the cyclic stress strain and creep behavior of the material required for structural analysis, the structural analysis to determine the local stress strain temperature time response of the material at the critical location in the component, and from a knowledge of the fatigue, creep, and failure resistance of the material, a prediction of the life of the component.

Hirschberg, M. H.↗
NASA NTRS1974

Fractional watt Vuillemier cryogenic refrigerator program engineering notebook. Volume 2: Stress analysis

A structural analysis performed on the 1/4-watt cryogenic refrigerator. The analysis covered the complete assembly except for the cooling jacket and mounting brackets. Maximum stresses, margin of safety, and natural frequencies were calculated for structurally loaded refrigerator components shown in assembly drawings. The stress analysis indicates that the design is satisfactory for the specified vibration environment, and the proof, burst, and normal operating loads.

Miller, W. S.↗
NASA NTRS1988

Probabilistic methods for structural response analysis

This paper addresses current work to develop probabilistic structural analysis methods for integration with a specially developed probabilistic finite element code. The goal is to establish distribution functions for the structural responses of stochastic structures under uncertain loadings. Several probabilistic analysis methods are proposed covering efficient structural probabilistic analysis methods, correlated random variables, and response of linear system under stationary random loading.

Wu, Y.-T.↗
DOE OSTI2016

Data mining graphene: Correlative analysis of structure and electronic degrees of freedom in graphenic monolayers with defects

The link between changes in the material crystal structure and its mechanical, electronic, magnetic, and optical functionalities known as the structure-property relationship is the cornerstone of the contemporary materials science research. The recent advances in scanning transmission electron and scanning probe microscopies (STEM and SPM) have opened an unprecedented path towards examining the materials structure property relationships on the single-impurity and atomic-configuration levels. Lacking, however, are the statistics-based approaches for cross-correlation of structure and property variables obtained in different information channels of the STEM and SPM experiments. Here we have designed an approach based on a combination of sliding window Fast Fourier Transform, Pearson correlation matrix, linear and kernel canonical correlation, to study a relationship between lattice distortions and electron scattering from the SPM data on graphene with defects. Our analysis revealed that the strength of coupling to strain is altered between different scattering channels which can explain coexistence of several quasiparticle interference patterns in the nanoscale regions of interest. In addition, the application of the kernel functions allowed us extracting a non-linear component of the relationship between the lattice strain and scattering intensity in graphene. Lastly, the outlined approach can be further utilized to analyzing correlations in various multi-modal imaging techniques where the information of interest is spatially distributed and has usually a complex multidimensional nature.

36 MATERIALS SCIENCE↗
NASA NTRS2021

NASA Engineering and Safety Center Technical Bulletin No. 21-05: Industry Recommendations from Arecibo Observatory Zinc Spelter Socket Joint Failure Analysis

A structural analysis and forensic investigation concluded that the Arecibo Observatory M4N socket joint failure in August 2020 was primarily due to cumulative damage caused by initially low structural design margins and a high percentage of sustained load, resulting in zinc creep deformation, progressive internal socket wire damage, and eventual loss of joint capacity. Open spelter sockets of this type are used throughout industry in stay cables. Recommendations are proposed to prevent failures of similar socket joints, including verification of positive stress margins in socket joint wires for all failure modes, periodic visual inspections with pass/fail criteria for zinc extrusion that are tied to structural qualification, and revisiting codes/ industry standards to capture lessons learned.

Arecibo Observatory↗
NASA NTRS1997

A Geometry Based Infra-structure for Computational Analysis and Design

The computational steps traditionally taken for most engineering analysis (CFD, structural analysis, and etc.) are: Surface Generation - usually by employing a CAD system; Grid Generation - preparing the volume for the simulation; Flow Solver - producing the results at the specified operational point; and Post-processing Visualization - interactively attempting to understand the results For structural analysis, integrated systems can be obtained from a number of commercial vendors. For CFD, these steps have worked well in the past for simple steady-state simulations at the expense of much user interaction. The data was transmitted between phases via files. Specifically the problems with this procedure are: (1) File based. Information flows from one step to the next via data files with formats specified for that procedure. (2) 'Good' Geometry. A bottleneck in getting results from a solver is the construction of proper geometry to be fed to the grid generator. With 'good' geometry a grid can be constructed in tens of minutes (even with a complex configuration) using unstructured techniques. (3) One-Way communication. All information travels on from one phase to the next. Until this process can be automated, more complex problems such as multi-disciplinary analysis or using the above procedure for design becomes prohibitive.

Haimes, Robert↗
NASA NTRS1993

Automated Finite Element Modeling of Wing Structures for Shape Optimization

The displacement formulation of the finite element method is the most general and most widely used technique for structural analysis of airplane configurations. Modem structural synthesis techniques based on the finite element method have reached a certain maturity in recent years, and large airplane structures can now be optimized with respect to sizing type design variables for many load cases subject to a rich variety of constraints including stress, buckling, frequency, stiffness and aeroelastic constraints (Refs. 1-3). These structural synthesis capabilities use gradient based nonlinear programming techniques to search for improved designs. For these techniques to be practical a major improvement was required in computational cost of finite element analyses (needed repeatedly in the optimization process). Thus, associated with the progress in structural optimization, a new perspective of structural analysis has emerged, namely, structural analysis specialized for design optimization application, or.what is known as "design oriented structural analysis" (Ref. 4). This discipline includes approximation concepts and methods for obtaining behavior sensitivity information (Ref. 1), all needed to make the optimization of large structural systems (modeled by thousands of degrees of freedom and thousands of design variables) practical and cost effective.

Harvey, Michael Stephen↗
NASA NTRS1979

Finite-strain large-deflection elastic-viscoplastic finite-element transient response analysis of structures

A method of analysis for thin structures that incorporates finite strain, elastic-plastic, strain hardening, time dependent material behavior implemented with respect to a fixed configuration and is consistently valid for finite strains and finite rotations is developed. The theory is formulated systematically in a body fixed system of convected coordinates with materially embedded vectors that deform in common with continuum. Tensors are considered as linear vector functions and use is made of the dyadic representation. The kinematics of a deformable continuum is treated in detail, carefully defining precisely all quantities necessary for the analysis. The finite strain theory developed gives much better predictions and agreement with experiment than does the traditional small strain theory, and at practically no additional cost. This represents a very significant advance in the capability for the reliable prediction of nonlinear transient structural responses, including the reliable prediction of strains large enough to produce ductile metal rupture.

Rodal, J. J. A.↗