Verification Facility for Cryogenic Optics, Mechanisms, and Structures for the SIRTF Telescope
NASA's Space Infrared Telescope Facility (SIRTF) is a 1-meter class cryogenically-cooled space observatory.
Cryogenic↗
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Results for “Mechanical Structure”
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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Mechanics of Structure Genome-Based Nonlinear Shell Analysis
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Yufei Long↗
Timoshenko Beam Modeling of Realistic Wind Turbine Blades Using Mechanics of Structure Genome
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Bagla, Akshat [Purdue University]↗
Skeletal adaptation to external loads optimizes mechanical properties: fact or fiction
The skeleton adapts to a changing mechanical environment but the widely held concept that bone cells are programmed to respond to local mechanical loads to produce an optimal mechanical structure is not consistent with the high frequency of bone fractures. Instead, the author suggests that other important functions of bone compete with mechanical adaptation to determine structure. As a consequence of competing demands, bone architecture never achieves an optimal mechanical structure. c2001 Lippincott Williams & Wilkins, Inc.
Review, Tutorial↗
Mechanical testing of large cryogenic structures
The mechanical testing performed on the Cryogenic Limb Array Etalon Spectrometer (CLAES) instrument installed on the Upper Atmosphere Research Satellite is discussed. The CLAES determines temperatures and concentrations of stratospheric minor species as a function of altitude by measuring the atmospheric infrared emission spectra. CLAES is based on a telescope optical system and infrared spectrometer which are cooled with cryogens.
Newkirk, Roger↗
Custom Space Mechanisms and Deployable Structures
MIT LL has experience in the design, analysis, building, testing, and deployment of custom mechanisms and structures for space systems. Previous work includes deployable structures and mechanisms for CubeSats and small satellites in LEO, GEO, and deep space applications.
mechanisms↗
Dynamics of flexible bodies in tree topology - A computer oriented approach
An approach suited for automatic generation of the equations of motion for large mechanical systems (i.e., large space structures, mechanisms, robots, etc.) is presented. The system topology is restricted to a tree configuration. The tree is defined as an arbitrary set of rigid and flexible bodies connected by hinges characterizing relative translations and rotations of two adjoining bodies. The equations of motion are derived via Kane's method. The resulting equation set is of minimum dimension. Dynamical equations are imbedded in a computer program called TREETOPS. Extensive control simulation capability is built in the TREETOPS program. The simulation is driven by an interactive set-up program resulting in an easy to use analysis tool.
Singh, R. P.↗
An overview of computational simulation methods for composite structures failure and life analysis
Three parallel computational simulation methods are being developed at the LeRC Structural Mechanics Branch (SMB) for composite structures failure and life analysis: progressive fracture CODSTRAN; hierarchical methods for high-temperature composites; and probabilistic evaluation. Results to date demonstrate that these methods are effective in simulating composite structures failure/life/reliability.
Chamis, Christos C.↗
A Miniaturized Seismometer for Subsurface Probing on Mars
Seismology is one of the most powerful tools for investigating the subsurface structure of a planet. The mechanical structure information derived from seismic measurements is complementary to other methods of probing the subsurface (such as gravity and electromagnetics), both in terms of spatial and depth resolution and the relevant types of material properties being sensed. In the near-surface, the propagation of seismic waves is especially sensitive to density and degree of compaction. In addition, interfaces between layer with contrasting properties can be relatively easily delineated. The subsurface of Mars provides an obvious target for seismic investigations. Searching for the presence of water is among the highest priority goals of the Mars Exploration Program, but there are many other important science questions that could be addressed by a seismic profile of the upper layers of the crust. We have developed an extremely small, lightweight, low-power seismometer for planetary applications which is ideally suited for use on Mars. This instrument has previously been proposed and selected for use on a comet (on the Rosetta Lander, subsequently deselected for programmatic reasons) and Mars (on the NetLander mission, with an emphasis on global structure determination).
Banerdt, W. B.↗
Structures and Acoustics Division
The Structures and Acoustics Division of NASA Glenn Research Center is an international leader in rotating structures, mechanical components, fatigue and fracture, and structural aeroacoustics. Included are disciplines related to life prediction and reliability, nondestructive evaluation, and mechanical drive systems. Reported are a synopsis of the work and accomplishments reported by the Division during the 1996 calendar year. A bibliography containing 42 citations is provided.
Acquaviva, Cynthia S.↗
Structures and Acoustics Division
The Structures and Acoustics Division of the NASA Glenn Research Center is an international leader in rotating structures, mechanical components, fatigue and fracture, and structural aeroacoustics. Included in this report are disciplines related to life prediction and reliability, nondestructive evaluation, and mechanical drive systems. Reported is a synopsis of the work and accomplishments completed by the Division during the 1997, 1998, and 1999 calendar years. A bibliography containing 93 citations is provided.
Acquaviva, Cynthia S.↗
Optically pumped submillimeter-waves and applications
Rapid development of optically pumped lasers has shown the potential to be used as a source for a high resolution spectrometer. In this connection, a compact, stable FIR laser was designed, fabricated, and assembled, integrating both the pump laser and the FIR cavity in the same mechanical structure for its improved (both thermal and mechanical) stability and mobility. Performance of the mixer structure which was designed and constructed for the evaluation of the Schottky diodes was found to be satisfactory. The feasibility of generating tunable sideband for molecular spectroscopy studies was demonstrated.
Dutta, J. M.↗
Large-scale structural analysis: The structural analyst, the CSM Testbed and the NAS System
The Computational Structural Mechanics (CSM) activity is developing advanced structural analysis and computational methods that exploit high-performance computers. Methods are developed in the framework of the CSM testbed software system and applied to representative complex structural analysis problems from the aerospace industry. An overview of the CSM testbed methods development environment is presented and some numerical methods developed on a CRAY-2 are described. Selected application studies performed on the NAS CRAY-2 are also summarized.
Knight, Norman F., Jr.↗
Biologically-Inspired Control for a Planetary Exploration Tensegrity Robot
Tensegrity structures are becoming increasingly popular as mechanical structures for robots. Their inherent compliance makes them extremely robust to environmental disturbances, and their design allows them to have a high strength-to-weight ratio whilst being lightweight compared to traditional robots. For these reasons they would be of interest to the aerospace industry, particularly for planetary exploration. However, being such compliant structures thanks to their network of elastic elements also means that their control is not an easy task. Relying solely on traditional control strategies to generate efficient locomotion would surely be near impossible due to the complex oscillatory motions and nonlinear interactions of its members. The goal of this project was to use bio-inspired control techniques to generate locomotion for a tensegrity icosahedron, namely the SUPERball project of the Intelligent Robotics Group of NASA Ames Research Center.
Leroy, Marc↗
Structure-Property Relationships of Bismaleimides
The purpose of this research was to control and systematically vary the network topology of bismaleimides through cure temperature and chemistry (addition of various coreactants) and subsequently attempt to determine structure-mechanical property relationships. Characterization of the bismaleimide structures by dielectric, rheological, and thermal analyses, and density measurements was subsequently correlated with mechanical properties such as modulus, yield strength, fracture energy, and stress relaxation. The model material used in this investigation was 4,4'-BismaleiMidodIphenyl methane (BMI). BMI was coreacted with either 4,4'-Methylene Dianiline (MDA), o,o'-diallyl bisphenol A (DABA) from Ciba Geigy, or Diamino Diphenyl Sulfone (DDS). Three cure paths were employed: a low- temperature cure of 140 C where chain extension should predominate, a high-temperature cure of 220 C where both chain extension and crosslinking should occur simultaneously, and a low-temperature (140 C) cure followed immediately by a high-temperature (220 C) cure where the chain extension reaction or amine addition precedes BMI homopolymerization or crosslinking. Samples of cured and postcured PMR-15 were also tested to determine the effects of postcuring on the mechanical properties. The low-temperature cure condition of BMI/MDA exhibited the highest modulus values for a given mole fraction of BMI with the modulus decreasing with decreasing concentration of BMI. The higher elastic modulus is the result of steric hindrance by unreacted BMI molecules in the glassy state. The moduli values for the high- and low/high-temperature cure conditions of BMI/MDA decreased as the amount of diamine increased. All the moduli values mimic the yield strength and density trends. For the high-temperature cure condition, the room- temperature modulus remained constant with decreasing mole fraction of BMT for the BMI/DABA and BMI/DDS systems. Postcuring PMR-15 increases the modulus over that of the cured material even though density values of cured and postcured PMR were essentially the same. Preliminary results of a continuous and intermittent stress relaxation experiment for BMI:MDA in a 2:1 molar ratio indicate that crosslinking is occurring when the sample is in the undeformed state. Computer simulation of properties such as density, glass transition temperature, and modulus for the low- temperature cure conditions of BMI/MDA and BMI/DABA were completed. The computer modeling was used to help further understand and confirm the structure characterization results. The simulations correctly predicted the trends of these properties versus mole fraction BMI and were extended to other BMI/diamine systems.
Tenteris-Noebe, Anita D.↗
Composite fuselage shell structures research at NASA Langley Research Center
Fuselage structures for transport aircraft represent a large portion of both the weight and cost of these aircraft primary structures. Composite materials offer the potential for reducing both the weight and cost of these structures, but only limited studies of the response and failure of composite fuselage structures have been conducted. The research is described which is being conducted and planned at NASA Langley to understand the critical behavior of composite fuselage structures and to validate the structural mechanics methodology being developed for stiffened composite fuselage shell structure subjected to combined internal pressure and mechanical loads. Stiffened shell and curved stiffened panel designs are currently being developed and analyzed, and these designs will be fabricated and then tested to study critical fuselage behavior and to validate structural analysis and design methodology. The research includes studies of the effects of combined internal pressure and mechanical loads on nonlinear stiffened panel and shell behavior, the effects of cutouts and other gradient producing discontinuities on composite shell response, and the effects of local damage on pressure containment and residual strength. Scaling laws are being developed that relate full scale and subscale behavior of composite fuselage shells.
Starnes, James H., Jr.↗
Computational methods in nonlinear structural and solid mechanics; Proceedings of the Symposium, Washington, D.C., October 6-8, 1980. Symposium sponsored by the George Washington University and NASA
Topics discussed include computational strategies for nonlinear problems in structural mechanics, time integration techniques and the numerical solution of nonlinear algebraic equations, material characterization and nonlinear fracture mechanics, nonlinear interaction problems, and seismic response and the nonlinear analysis of concrete structures. Also considered are nonlinear problems for nuclear reactors, crash dynamics and impact problems, nonlinear problems of fibrous composites and advanced nonlinear applications, and computerized symbolic manipulation and nonlinear analysis software systems.
Noor, A. K.↗
Layerwise mechanics and finite element for the dynamic analysis of piezoelectric composite plates
Laminate and structural mechanics for the analysis of laminated composite plate structures with piezoelectric actuators and sensors are presented. The theories implement layerwise representations of displacements and electric potential, and can model both the global and local electromechanical response of smart composite laminates. Finite-element formulations are developed for the quasi-static and dynamic analysis of smart composite structures containing piezoelectric layers. Comparisons with an exact solution illustrate the accuracy, robustness and capability of the developed mechanics to capture the global and local response of thin and/or thick laminated piezoelectric plates. Additional correlations and numerical applications demonstrate the unique capabilities of the mechanics in analyzing the static and free-vibration response of composite plates with distributed piezoelectric actuators and sensors.
Saravanos, Dimitris A.↗