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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Aircraft wing structure detail design

The provisions of this project call for the design of the structure of the wing and carry-through structure for the Viper primary trainer, which is to be certified as a utility category trainer under FAR part 23. The specific items to be designed in this statement of work were Front Spar, Rear Spar, Aileron Structure, Wing Skin, and Fuselage Carry-through Structure. In the design of these parts, provisions for the fuel system, electrical system, and control routing were required. Also, the total weight of the entire wing planform could not exceed 216 lbs. Since this aircraft is to be used as a primary trainer, and the SOW requires a useful life of 107 cycles, it was decided that all of the principle stresses in the structural members would be kept below 10 ksi. The only drawback to this approach is a weight penalty.

Sager, Garrett L.↗
NASA NTRS1982

Automated optimum design of wing structures. Deterministic and probabilistic approaches

The automated optimum design of airplane wing structures subjected to multiple behavior constraints is described. The structural mass of the wing is considered the objective function. The maximum stress, wing tip deflection, root angle of attack, and flutter velocity during the pull up maneuver (static load), the natural frequencies of the wing structure, and the stresses induced in the wing structure due to landing and gust loads are suitably constrained. Both deterministic and probabilistic approaches are used for finding the stresses induced in the airplane wing structure due to landing and gust loads. A wing design is represented by a uniform beam with a cross section in the form of a hollow symmetric double wedge. The airfoil thickness and chord length are the design variables, and a graphical procedure is used to find the optimum solutions. A supersonic wing design is represented by finite elements. The thicknesses of the skin and the web and the cross sectional areas of the flanges are the design variables, and nonlinear programming techniques are used to find the optimum solution.

Rao, S. S.↗
NASA NTRS1994

Discrete crack growth analysis methodology for through cracks in pressurized fuselage structures

A methodology for simulating the growth of long through cracks in the skin of pressurized aircraft fuselage structures is described. Crack trajectories are allowed to be arbitrary and are computed as part of the simulation. The interaction between the mechanical loads acting on the superstructure and the local structural response near the crack tips is accounted for by employing a hierarchical modeling strategy. The structural response for each cracked configuration is obtained using a geometrically nonlinear shell finite element analysis procedure. Four stress intensity factors, two for membrane behavior and two for bending using Kirchhoff plate theory, are computed using an extension of the modified crack closure integral method. Crack trajectories are determined by applying the maximum tangential stress criterion. Crack growth results in localized mesh deletion, and the deletion regions are remeshed automatically using a newly developed all-quadrilateral meshing algorithm. The effectiveness of the methodology and its applicability to performing practical analyses of realistic structures is demonstrated by simulating curvilinear crack growth in a fuselage panel that is representative of a typical narrow-body aircraft. The predicted crack trajectory and fatigue life compare well with measurements of these same quantities from a full-scale pressurized panel test.

Potyondy, David O.↗
NASA NTRS1977

Evaluation of structural design concepts for an arrow-wing supersonic cruise aircraft

An analytical study was performed to determine the best structural approach for design of primary wing and fuselage structure of a Mach 2.7 arrow wing supersonic cruise aircraft. Concepts were evaluated considering near term start of design. Emphasis was placed on the complex interactions between thermal stress, static aeroelasticity, flutter, fatigue and fail safe design, static and dynamic loads, and the effects of variations in structural arrangements, concepts and materials on these interactions. Results indicate that a hybrid wing structure incorporating low profile convex beaded and honeycomb sandwich surface panels of titanium alloy 6Al-4V were the most efficient. The substructure includes titanium alloy spar caps reinforced with boron polyimide composites. The fuselage shell consists of hat stiffened skin and frame construction of titanium alloy 6Al-4V. A summary of the study effort is presented, and a discussion of the overall logic, design philosophy and interaction between the analytical methods for supersonic cruise aircraft design are included.

Sakata, I. F.↗
NASA NTRS1980

Compliant surfaces - Introduction

It is noted that the essence of the compliant surface question is whether or not wall motion can provide a decrease in skin friction for either transitional or turbulent flows. This wall motion is capable of being externally excited or flow driven, with varying amounts of fluid motion-wall motion phasing (depending primarily upon wall structural configuration and damping). It is concluded that current research has eroded still further the experimental data base which indicates drag reduction on compliant surfaces under turbulent boundary layers in air. The need for further clarification and research is stressed for the small wavelength liquid case.

Bushnell, D. M.↗
NASA NTRS1982

Advanced Strain-Isolation-Pad Material with Bonded Fibrous Construction

The feasibility of utilizing air lay and liquid lay felt deposition techniques to fabricate strain isolation pad (SIP) materials for the Space Shuttle Orbiter was demonstrated. These materials were developed as candidate replacements for the present needled felt SIP used between the ceramic tiles and the aluminum skin on the undersurface of the Orbiter. The SIP materials that were developed consisted of high temperature aramid fibers deposited by controlled fluid (air or liquid) carriers to form low density unbonded felts. The deposited felts were then bonded at the fiber intersections with a small amount of high temperature polyimide resin. This type of bonded felt construction can potentially eliminate two of the problems associated with the present SIP, viz., transmittal of localized stresses into the tiles and load history dependent mechanical response. However, further work is needed to achieve adequate through thickness tensile strength in the bonded felts.

Seibold, R. W.↗
NASA NTRS1988

Composite transport wing technology development

The design, fabrication, testing, and analysis of stiffened wing cover panels to assess damage tolerance criteria are discussed. The damage tolerance improvements were demonstrated in a test program using full-sized cover panel subcomponents. The panels utilized a hard skin concept with identical laminates of 44-percent 0-degree, 44-percent plus or minus 45-degree, and 12-percent 90-degree plies in the skins and stiffeners. The panel skins were impacted at midbay between the stiffeners, directly over the stiffener, and over the stiffener flange edge. The stiffener blades were impacted laterally. Impact energy levels of 100 ft-lb and 200 ft-lb were used. NASTRAN finite-element analyses were performed to simulate the nonvisible damage that was detected in the panels by nondestructive inspection. A closed-form solution for generalized loading was developed to evaluate the peel stresses in the bonded structure. Two-dimensional delamination growth analysis was developed using the principle of minimum potential energy in terms of closed-form solution for critical strain. An analysis was conducted to determine the residual compressive stress in the panels after impact damage, and the analytical predictions were verified by compression testing of the damaged panels.

Madan, Ram C.↗
NASA NTRS2003

Exploratory Calibration of Adjustable-Protrusion Surface-Obstacle (APSO) Skin Friction Vector Gage

The design of an adjustable-protrusion surface-obstacle (APSO) skin friction vector gage is presented. Results from exploratory calibrations conducted in laminar and turbulent boundary layers at the Washington University Low-Speed Wind Tunnel and for turbulent boundary layers at speeds up to Mach 2 on the ceiling of the NASA Glenn Research Center 8- X 6-ft Supersonic Wind Tunnel are also discussed. The adjustable-height gage was designed to yield both the magnitude and direction of the surface shear stress vector and to measure the local static pressure distribution. Results from the NASA test show good correlation for subsonic and low supersonic conditions covering several orders of magnitude in terms of the adopted similarity variables. Recommendations for future work in this area consist of identifying the physical parameters responsible for the disagreement between the university and NASA data sets, developing a compressibility correction specific to the APSO geometry, and examining the effect that static pressure distribution and skewed boundary layers have on the results from the APSO.

Hakkinen, Raimo J.↗
NASA NTRS1993

Recent developments in equivalent plate modeling for wing shape optimization

A new technique for structural modeling of airplane wings is presented taking transverse shear effects into account. The kinematic assumptions of first order shear deformation plate theory in combination with numerical analysis based on simple polynomials which define geometry, construction and displacement approximations lead to analytical expressions for elements of the stiffness and mass matrices and load vector. Contributions from the cover skins, spar and rib caps and spar and rib webs are included as well as concentrated springs and concentrated masses. Limitations of current equivalent plate wing modeling techniques based on classical plate theory are discussed, and the improved accuracy of the new equivalent plate technique is demonstrated through comparison to finite element analysis and test results. Analytical derivatives of stiffness, mass and load terms with respect to wing shape lead to analytic sensitivities of displacements, stresses and natural modes with respect to planform shape and depth distribution. This makes the new capability an effective structural tool for wing shape optimization.

Livne, Eli↗
NASA NTRS1975

Design study of structural concepts for an arrow-wing supersonic-cruise aircraft

An analytical study was performed to determine the best structural approach for design of primary wing and fuselage structure of a Mach number 2.7 arrow-wing supersonic cruise aircraft. Concepts were evaluated considering near-term start-of-design. Emphasis was placed on the complex interactions between thermal stress, static aeroelasticity, flutter, fatigue and fail-safe design, static and dynamic loads, and the effects of variations in structural arrangements, concepts and materials on these interactions. Results indicate that a hybrid wing structure incorporating low-profile convex-beaded and honeycomb sandwich surface panels of titanium alloy 6Al-4V were the most efficient. The substructure includes titanium alloy spar caps reinforced with Boron-polyimide composites. The fuselage shell is a closed-hat stiffened skin and frame construction of titanium alloy 6Al-4V. This paper presents an executive summary of the study effort, and includes a discussion of the overall study logic, design philosophy and interaction between the analytical methods for supersonic cruise aircraft design.

Sakata, I. F.↗
NASA NTRSDate not supplied

USM3D-ME Solutions for RANS Test Suite of High-Fidelity CFD Verification Workshop 2024

USM3D-ME solutions for the High-Fidelity CFD Verification Workshop 2024 are presented. Solutions are computed for the Reynolds-Averaged Navier-Stokes equations using the Spalart-Allmaras one equation turbulence model, SA-neg-QCR2000-R, that is enhanced with a nonlinear correction to the turbulence stresses and a correction for flow rotation. USM3D-ME solutions have been computed for the three verification cases, namely, a Joukowski airfoil, a subsonic three-dimensional flow around an extruded NACA 0012 wing in tunnel, and subsonic flow around a high-lift wing-body configuration. Iterative convergence of USM3D-ME solutions on several grids within various grid families is demonstrated. Grid convergence of integrated forces, pitching moment and sectional variations of surface pressure and skin friction are also presented.

CFD↗
NASA NTRS1983

Preliminary scramjet design for hypersonic airbreathing missile application

A conceptual design study of a scramjet engine was conducted for a hypersonic surface to air missile (HYSAM). The definition of the engine was based upon the requirements of accelerating the HYSAM from Mach 4 at 20,000 feet to Mach 6 at 100,000 feet and the cruise conditions at Mach 6. The resulting external and internal environmental conditions were used by various engineering disciplines performing design, stress and heat transfer analysis. A detailed structural analysis was conducted along with an indepth thermal analysis. Structurally all the components within the system exhibit positive margins of safety. A feasible concept was defined which uses state-of-the-art materials and existing TMC technology. The engine basically consists of a three dimensional carbon/carbon combustor/nozzle secured to an FS-85 columbium inlet. The carbon/carbon liner is sheathed with carbon felt insulation to thermally protect the FS-85 structure and skin. The thermal analysis of the engine indicates that a thermally viable configuration exists.

Carlson, C. H.↗
NASA NTRSDate not supplied

TPSAS-NF1676L-32227-DND

The ability of a recently proposed cohesive fatigue model to predict the initiation and propagation of skin/stiffener separation was evaluated using a three-point bend (3PB) configuration. The 3PB specimen consists of a quasi-isotropic laminate representing the skin of a fuselage. A shorter doubler representing the flange of a stiffener is co-cured at the center of the specimen. A simplified modeling technique was applied, in which the complex damage mechanisms involved in the separation, such as delamination migration, matrix cracking, bridging, and crack delving are represented by a mixed-mode trilinear cohesive law at the interface between the skin and the doubler. The quasi-static properties of the trilinear law were characterized. The main advantage of the proposed fatigue model is that it relies on quasi-static properties as well as engineering assumptions to compose the shape of the S-N diagram. The model does not require Paris law data, and it is capable of predicting the initiation of separation, the rate of propagation, as well as the effects of crack resistance curves and the stress ratio.

Carlos G Davila↗
NASA NTRS1956

Experimental Investigation of the Strength of Multiweb Beams with Corrugated Webs

The results of an experimental investigation of the strength of multiweb beams with corrugated webs are reported. Included in the investigation were two types of connection between the web and the skin. A comparison between the structural efficiency of corrugated-web and channel-web multiweb beams is presented, and it is shown that, for a considerable range of the structural index, corrugated-web beams can be built which are structurally more efficient than channel-web beams.

LOADS AND STRESSES, STRUCTURAL - BENDING↗
NASA NTRS2000

Finite Elements Analysis of a Composite Semi-Span Test Article With and Without Discrete Damage

AS&M Inc. performed finite element analysis, with and without discrete damage, of a composite semi-span test article that represents the Boeing 220-passenger transport aircraft composite semi-span test article. A NASTRAN bulk data file and drawings of the test mount fixtures and semi-span components were utilized to generate the baseline finite element model. In this model, the stringer blades are represented by shell elements, and the stringer flanges are combined with the skin. Numerous modeling modifications and discrete source damage scenarios were applied to the test article model throughout the course of the study. This report details the analysis method and results obtained from the composite semi-span study. Analyses were carried out for three load cases: Braked Roll, LOG Down-Bending and 2.5G Up-Bending. These analyses included linear and nonlinear static response, as well as linear and nonlinear buckling response. Results are presented in the form of stress and strain plots. factors of safety for failed elements, buckling loads and modes, deflection prediction tables and plots, and strainage prediction tables and plots. The collected results are presented within this report for comparison to test results.

Lovejoy, Andrew E.↗
NASA NTRS2012

2012 Ground Testing Highlights

As part of the Fundamental Aeronautics Program and a collaborative effort with Boeing, and Lockheed Martin this past year a series of sonic boom test were completed in the NASA Ames Unitary Plan Wind Tunnel (UPWT). One of the goals was to develop new test techniques and hardware for measuring sonic boom signatures in the transonic and supersonic regimes. Data for various model designs and configurations were collected and will be used to validate CFD predictions of sonic boom signatures. Reactivation of the NASA Ames Mitsubishi compressor system was completed this past year. The compressor is intended to replace and augment the existing UPWT Clark Compressor as the primary Make Up Air (MUA) source. The MUA system provides air and vacuum pumping capability to the Ames UPWT. It will improve productivity and reliability of the UPWT as a vital testing and research facility for the U.S. aerospace industry and NASA. Funding for this task was provided from the American Recovery Investment Act (ARRA). Installation and validation of a Noncontact Stress Monitoring System (NSMS) for the 3-stage compressor was completed at the 11-foot Transonic Wind Tunnel. The system, originally developed at AEDC, consists of 36 pairs of LED light sources with optic beam send and receive probes along a 1-per rev signal. The new system allows for continuous monitoring and recording of compressor blade bending and torsion stress during normal test operations. A very unusual test was completed in the 11 FT TWT to acquire aerodynamic and flow field data for the Crew Exploration Vehicle (CEV) Parachute Assembly System (CPAS) to validate CFD methods and tools. Surface pressure distribution measurements and velocity measurements in the wake of the command module back to the drogues parachute location were acquired. Testing methods included Particle Image Velocimetry (PIV), Pressure Sensitive Paint (PSP), Schlieren Infrared Imaging (IR) and boundary layer survey and skin friction.

Buchholz, Steven J.↗
NASA NTRS1994

Equivalent plate structural modeling for wing shape optimization including transverse shear

A new technique for structural modeling of airplanes wings is presented taking transverse shear effects into account. The kinematic assumptions of first-order shear deformation plate theory in combination with numerical analysis, where simple polynomials are used to define geometry, construction, and displacement approximations, lead to analytical expressions for elements of the stiffness and mass matrices and load vector. Contributions from the cover skins, spar and rib caps, and spar and rib webs are included as well as concentrated springs and concentrated masses. Limitations of wing modeling techniques based on classical plate theory are discussed, and the improved accuracy of the new equivalent plate technique is demonstrated through comparison with finite element analysis and test results. Expressions for analytical derivatives of stiffness, mass, and load terms with respect to wing shape are given. Based on these, it is possible to obtain analytic sensitivities of displacements, stresses, and natural frequencies with respect to planform shape and depth distribution. This makes the new capability an effective structural tool for wing shape optimization.

Livne, Eli↗
NASA NTRS1994

Equivalent Plate Structural Modeling for Wing Shape Optimization Including Transverse Shear

A new technique for structural modeling of airplane wings is presented taking transverse shear effects into account. The kinematic assumptions of first-order shear deformation plate theory In combination with numerical analysis, where simple polynomials are used to define geometry, construction, and displacement approximations, lead to analytical expressions for elements of the stiffness and mass matrices and load vector. Contributions from the cover skins, spar and rib caps, and spar and rib webs are included as well as concentrated springs and concentrated masses. Limitations of wing modeling techniques based on classical plate theory are discussed, and the Improved accuracy of the new equivalent plate technique is demonstrated through comparison with finite element analysis and test results. Expressions for analytical derivatives of stiffness, mass, and load terms with respect to wing shape are given. Based on these, it is possible to obtain analytic sensitivities of displacements, stresses, and natural frequencies with respect to planform shape and depth distribution. This makes the new capability an effective structural tool for wing shape optimization.

Livne, Eli↗