Search NASA⌕ Search

SEARCH · Search NASA

Results for “Structural Testing”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,711 records · Page 95
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Mechanical systems readiness assessment and performance monitoring study

The problem of mechanical devices which lack the real-time readiness assessment and performance monitoring capability required for future space missions is studied. The results of a test program to establish the feasibility of implementing structure borne acoustics, a nondestructive test technique, are described. The program included the monitoring of operational acoustic signatures of five separate mechanical components, each possessing distinct sound characteristics. Acoustic signatures were established for normal operation of each component. Critical failure modes were then inserted into the test components, and faulted acoustic signatures obtained. Predominant features of the sound signature were related back to operational events occurring within the components both for normal and failure mode operations. All of these steps can be automated. The structure borne acoustics technique lends itself to reducing checkout time, simplifying maintenance procedures, and reducing manual involvement in the checkout, operation, maintenance, and fault diagnosis of mechanical systems.

Source record↗
NASA NTRS1990

A subgrid-scale model based on the second-order velocity structure function

A series of tests were performed to help extend the use of a subgrid-scale model to compressible and wall-bounded flows. A priori tests were done in the case of the incompressible turbulent channel flow. They showed that a 1-D formulation of the structure-function model is more appropriate, leading to a satisfactory behavior of the model at the walls without requiring any damping function. This model is consistent with the original formulation of Metais & Lesieur (1990). In large-eddy simulations of compressible isotropic turbulence, both models performed well up to an initial rms Mach number of 0.6.

Comte, P.↗
NASA NTRS1993

Advanced composite fuselage technology

Boeing's ATCAS program has completed its third year and continues to progress towards a goal to demonstrate composite fuselage technology with cost and weight advantages over aluminum. Work on this program is performed by an integrated team that includes several groups within The Boeing Company, industrial and university subcontractors, and technical support from NASA. During the course of the program, the ATCAS team has continued to perform a critical review of composite developments by recognizing advances in metal fuselage technology. Despite recent material, structural design, and manufacturing advancements for metals, polymeric matrix composite designs studied in ATCAS still project significant cost and weight advantages for future applications. A critical path to demonstrating technology readiness for composite transport fuselage structures was created to summarize ATCAS tasks for Phases A, B, and C. This includes a global schedule and list of technical issues which will be addressed throughout the course of studies. Work performed in ATCAS since the last ACT conference is also summarized. Most activities relate to crown quadrant manufacturing scaleup and performance verification. The former was highlighted by fabricating a curved, 7 ft. by 10 ft. panel, with cocured hat-stiffeners and cobonded J-frames. In building to this scale, process developments were achieved for tow-placed skins, drape formed stiffeners, braided/RTM frames, and panel cure tooling. Over 700 tests and supporting analyses have been performed for crown material and design evaluation, including structural tests that demonstrated limit load requirements for severed stiffener/skin failsafe damage conditions. Analysis of tests for tow-placed hybrid laminates with large damage indicates a tensile fracture toughness that is higher than that observed for advanced aluminum alloys. Additional recent ATCAS achievements include crown supporting technology, keel quadrant design evaluation, and sandwich process development.

Ilcewicz, Larry B.↗
NASA NTRS1955

Aircraft structures research at elevated temperatures

A review is made of the test techniques that have been developed and used by the NACA for experimental research in aircraft structures at elevated temperatures. Some experimental results are presented. Remarks are included on the problem of model scaling for testing of structures at high temperatures. (author)

Duberg, John E↗
NASA NTRS1982

Development of the structural technology of a large deployable antenna

The current NASA-sponsored Antenna Technology Development Program of the offset wrap-rib antenna concept is based on a ground test program of 'proof of concept' hardware whose potential on-orbit performance is based on analytical estimates. The ground demonstration hardware represents a partial 55-meter diameter reflector and feed support structure. Testing will include automated deployment, reflector surface quality evaluation and validation of analytical performance models. Test results and hardware fabrication costs will be used to refine the models that will be the basis for the preliminary design of a 100-meter diameter wrap-rib antenna system. Additionally, the design, processes, tooling, fabrication techniques, fixturing and assembly approaches used for the 'proof of concept' hardware are directly applicable to building flight systems up to 100 meters in diameter.

Wada, B. K.↗
NASA NTRS2023

The Effects of Off-Axis Loading on the Compression After Impact Strength of Quasi-Isotropic Face Sheet Honeycomb Core Sandwich Structure

This study presents experimental results of compression after impact (CAI) testing of aluminum honeycomb core sandwich structure with face sheets made of co-cured T1100/3960 quasi-isotropic carbon/epoxy when tested at +22.5⁰ and -22.5⁰ with respect to the 0⁰ fibers. In a previous study examining the CAI strengths of honeycomb sandwich structure, it was found that specimens had different CAI strengths, based on a [-45/90/+45/0]s layup, depending on whether they were tested in the 0⁰ direction (face sheet layup of [-45/90/+45/0]s) or 90⁰ direction (face sheet layup of [+45/0/-45/90]s). The CAI strength results showed that the specimens tested in the 90⁰ direction had a 19% drop in CAI strength compared to specimens tested in the 0⁰ direction. This was attributed to the 0⁰ load bearing plies in the 0⁰ direction specimens being “tucked in” at the center of the specimen thus providing more stability against microbuckling. This raised the question as to what CAI strength would specimens tested at +22.5⁰ (face sheet layup of [-22.5/- 67.5/+67.6/+22.5]s) and -22.5⁰ (face sheet layup of [-67.5/+67.5/+22.5/-22.5]s) have compared to specimens tested in the 0⁰ and 90⁰ direction. Results presented in this study show that the specimens loaded at +22.5⁰ and -22.5⁰ have a similar average CAI strength compared to the specimens loaded in the 0⁰ direction. The specimens loaded in the 90⁰ direction exhibit 16% lower average CAI strength. Additional specimens were tested in the +45⁰ direction to put the 0⁰ load bearing fibers on the outside of the specimen to see if this would decrease the strength as has been documented for undamaged strength. These specimens have average CAI strength values between the 0⁰ direction average CAI strength values and the 90⁰ direction average CAI strength values.

Sandwich structure↗
NASA NTRS1983

Development of deployable structures for large space platforms. Volume 2: Design development

Design evolution, test article design, test article mass properties, and structural analysis of deployable platform systems are discussed. Orbit transfer vehicle (OTV) hangar development, OTV hangar concept selection, and manned module development are discussed. Deployable platform systems requirements, material data base, technology development needs, concept selection and deployable volume enclosures are also discussed.

Greenberg, H. S.↗
NASA NTRS2007

A One-Piece Lunar Regolith Bag Garage Prototype

Shelter structures on the moon, even in early phases of exploration, should incorporate lunar materials as much as possible. This Technical Memorandum details the design and construction of a prototype for a one-piece regolith bag unpressurized garage concept and a materials testing program to investigate six candidate fabrics to learn how they might perform in the lunar environment. The conceptualization was that a lightweight fabric form be launched from Earth and landed on the lunar surface to be robotically filled with raw lunar regolith. Regolith bag fabric candidates included: Vectran(TM), Nextel(TM), Gore PTFE Fabric(TM), Zylon(TM), Twaron(TM), and Nomex(TM). Tensile (including post radiation exposure), fold, abrasion, and hypervelocity impact testing were performed under ambient conditions, and also performed under cold and elevated temperatures. In some cases, Johnson Space Center lunar simulant (JSC-1) was used in conjunction with testing. A series of preliminary structures was constructed during final prototype design based on the principles of the classic masonry arch. The prototype was constructed of Kevlar(TM) and filled with vermiculite. The structure is free-standing, but has not yet been load tested. Future plans would be to construct higher fidelity prototypes and to conduct appropriate tests of the structure.

Smithers, G. A.↗
NASA NTRS2004

Space Shuttle Crawler Transporter Vibration Analysis in Support of Rollout Fatigue Load Spectra Verification Program

The Crawler Transporter (CT), designed and built for the Apollo Program in the 1960's and surpassing its initial operational life, has become an integral part of the Space Shuttle Program (SSP). The CT transports the Space Shuttle Vehicle (SSV) stack, atop the Mobile Launch Platform (MLP), from the Vehicle Assembly Building (VAB) to the launch pad. This support structure provides hydraulic jacking, leveling and load equalization for the 12 million pound stack on its 3.5-5.0 mile rollout to the launch pad. Major elements of the SSV, consisting of the orbiter, solid rocket boosters (SRB) and external tank (ET) have required fatigue analyses as part of the mission life certification. Compared to rollout vibration, the SSV sees relatively high vibration loads during launch, ascent, descent and landing phases of the mission. Although preliminary measured SRB vibration levels during rollout were of low amplitude and frequency, the duration of the rollout phase is typically high, from 5-6 hours. As part of an expanded mission life assessment, additional certification effort was initiated to define fatigue load spectra for rollout. This study addresses the CT vibration analyses in support of the rollout fatigue study. Structural models developed for modal and vibration analyses were used to identify unique CT, CT/MLP and CT/MLP/SRB vibration characteristics for comparison to instrumented rollout tests. Whereas the main structural and vibration characteristics of the SSV are well defined, minimum analytical and vibration test data on the Crawler Transporter were available. Unique vibration characteristics of the CT are attributable to the drive mechanism, hydraulic jacking system, structural framing and the CT-to-MLP support pad restraints. Initial tests performed on the CT/MLP/SRB configuration showed reasonable correlation with predicted mode shapes and frequencies.

Margasahayam, Ravi N.↗
NASA NTRS1992

TDS and BMT for CASES ADF (ADF RAMS), acceptance test

The Controls, Astrophysics, and Structures Experiment (CASES) is a proposed experiment to collect x ray images of the galactic center and solar disk with unprecedented resolution. This requires precision pointing and suppression of vibrations in the long, flexible structure that comprises the 32-m x ray telescope optical bench. Two separate electro-optical sensors systems are provided for the ground test facility (GTF). The Boom Motion Tracker (BMT) measures eigenvector data for post-mission use in system identification. The Tip Displacement Sensor (TDS) measures boom tip position and is used as feedback for the closed-loop control system that stabilizes the boom. The deployment and testing of the BMT and TDS systems is summarized.

Davis, Hugh W.↗
NASA NTRS1979

Experimental Investigation of Launch Vehicle Transient Input Simulation in Payload Tests

The technique of electronically simulating the structural dynamics of a launch vehicle in transient tests of payloads using multiple vibration excitation systems was investigated. The development of computer programs to determine transfer functions, synthesize shaker forcing functions, and control vibration exciters is described. A demonstration test using the techniques was described and results are presented. The evaluation of the potential for applying this technique to large Shuttle payloads is discussed.

Rader, P.↗
NASA NTRS2008

The Inception of OMA in the Development of Modal Testing Technology for Wind Turbines

Wind turbines are immense, flexible structures with aerodynamic forces acting on the rotating blades at harmonics of the turbine rotational frequency, which are comparable to the modal frequencies of the structure. Predicting and experimentally measuring the modal frequencies of wind turbines has been important to their successful design and operation. Performing modal tests on wind turbine structures over 100 meters tall is a substantial challenge, which has inspired innovative developments in modal test technology. For wind turbines, a further complication is that the modal frequencies are dependent on the turbine rotation speed. The history and development of a new technique for acquiring the modal parameters using output-only response data, called the Natural Excitation Technique (NExT), will be reviewed, showing historical tests and techniques. The initial attempts at output-only modal testing began in the late 1980's with the development of NExT in the 1990's. NExT was a predecessor to OMA, developed to overcome these challenges of testing immense structures excited with environmental inputs. We will trace the difficulties and successes of wind turbine modal testing from 1982 to the present. Keywords: OMA, Modal Analysis, NExT, Wind Turbines, Wind Excitation

James, George H., III↗
NASA NTRSDate not supplied

Simplified Applied Loads of a Transonic Truss-Braced Wing Derived from Computational Fluid Dynamics

The transonic truss-braced wing (TTBW) concept is under consideration by the NASA Advanced Air Transport Technology (AATT) project due to its potential to reduce fuel consumption of transport aircraft. To properly evaluate the TTBW concept, detailed structural modeling and subsequent test planning is underway, which requires a simplified set of discrete applied loads that simulate the distributed aerodynamic pressures. Given the unique architecture of the TTBW and its intended operation in the transonic regime, computational fluid dynamics (CFD) is the ideal approach to employ to ensure the aerodynamics of this configuration are sufficiently captured. To convert aerodynamic results into input for structural models, application of a data transfer tool, Discrete Data Transfer Between Dissimilar Meshes (DDTBDM), is presented to resolve aerodynamic pressures from CFD into single load vectors at hardpoints along both the wing and the strut. Evaluation of mapping the aerodynamic forces to hardpoints at rib and spar intersections in a structural model is performed, and the results are also compared with a linear static aeroelastic analysis. The structural responses indicate that distributing forces along only the wing and strut forward spars is insufficient for simulating the distributed aerodynamic loads. Adding moments along the forward spars improved the global response of the wing, but the point moments created unrealistic local rotations within the structure. When distributing loads along both the forward and aft spars of the wing and strut, the global response was less sensitive to the inclusion of point moments, which indicated the arrangement of point forces alone was sufficient input for structural design work and testing and provided a more continuous loading profile.

Finite Element↗
NASA NTRSDate not supplied

Simplified Applied Loads of a Transonic Truss-Braced Wing Derived from Computational Fluid Dynamic

The transonic truss-braced wing (TTBW) concept is under consideration by the NASA Advanced Air Transport Technology (AATT) project due to its potential to reduce fuel consumption of transport aircraft. To properly evaluate the TTBW concept, detailed structural modeling and subsequent test planning is underway, which requires a simplified set of discrete applied loads that simulate the distributed aerodynamic pressures. Given the unique architecture of the TTBW and its intended operation in the transonic regime, computational fluid dynamics (CFD) is the ideal approach to employ to ensure the aerodynamics of this configuration are sufficiently captured. To convert aerodynamic results into input for structural models, application of a data transfer tool, Discrete Data Transfer Between Dissimilar Meshes (DDTBDM), is presented to resolve aerodynamic pressures from CFD into single load vectors at hardpoints along both the wing and the strut. Evaluation of mapping the aerodynamic forces to hardpoints at rib and spar intersections in a structural model is performed, and the results are also compared with a linear static aeroelastic analysis. The structural responses indicate that distributing forces along only the wing and strut forward spars is insufficient for simulating the distributed aerodynamic loads. Adding moments along the forward spars improved the global response of the wing, but the point moments created unrealistic local rotations within the structure. When distributing loads along both the forward and aft spars of the wing and strut, the global response was less sensitive to the inclusion of point moments, which indicated the arrangement of point forces alone was sufficient input for structural design work and testing and provided a more continuous loading profile.

Finite Element↗
NASA NTRS1997

Advanced Transportation Systems, Alternate Propulsion Subsystem Concepts

An understanding of the basic flow of of the subject hybrid model has been gained through this series of testing. Changing injectors (axial vs. radial) and inhibiting the flow between the upstream plenum and the CP section changes the basic flow structure, as evidenced by streamline and velocity contour plots. Numerous shear layer structures were identified in the test configurations; these structures include both standing and traveling vortices which may affect combustion ion stability. Standing vortices may play a role in the heat addition process as the oxidizer enters the motor, while traveling vortices may be instability mechanisms in themselves. Finally, the flow visualization and LVD measurements give insight into determining the effects of flow induced shear layers.

Source record↗
NASA NTRS1995

Finite Element Analysis of an Energy Absorbing Sub-floor Structure

As part of the Advanced General Aviation Transportation Experiments program, the National Aeronautics and Space Administration's Langley Research Center is conducting tests to design energy absorbing structures to improve occupant survivability in aircraft crashes. An effort is currently underway to design an Energy Absorbing (EA) sub-floor structure which will reduce occupant loads in an aircraft crash. However, a recent drop test of a fuselage specimen with a proposed EA sub-floor structure demonstrated that the effects of sectioning the fuselage on both the fuselage section's stiffness and the performance of the EA structure were not fully understood. Therefore, attempts are underway to model the proposed sub-floor structure on computers using the DYCAST finite element code to provide a better understanding of the structure's behavior in testing, and in an actual crash.

Moore, Scott C.↗