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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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We will develop structural mechanics models that capture the evolution of feedstock attributes during the Forest Concepts comminution process. Models will be validated by data provided by Forest Concepts and experiments performed by synergistic projects within the Feedstock Conversion Interface Consortium.
The EM CsI crystals and SiPM readout calorimeter of the Mu2e experiment is fully assembled, with all components completed and tested; the mechanical structure is fully built, with a complete integration and test of all the analog sensors and electronics. The digital electronics is being produced and installed. We summarise the Calorimeter characteristics and the assembly status, as well as the move, installation and commissioning plans of the final disks in the Mu2e hall.
Cyclic loading or other stresses can lead to development of cracks and crack growth in mechanical structures, leading to eventual failure. While ultrasound imaging can be used for non-destructive testing of such structures, conventional ultrasound techniques are often limited by crack size, density, and areal coverage. An effective characterization of real-world, large-area structures is required at an early damage stage to prevent catastrophic failure and predict remaining life. In this study, a new nonlinear ultrasonic testing (NUT) method is proposed for large-area monitoring of practical structures with arbitrary complexity by using multiple-mode guided-wave ultrasonic signals. The proposed guided-wave NUT technique requires single-element transducers, simple electronics, and a mixed time-frequency domain signal processing. As a proof-of-concept demonstration, numerical simulations and experiments are performed on an A36 carbon steel beam assembly with previously formed microstructural defects that cause nonlinearities in ultrasonic response. The quadratic dependence of the nonlinear wave excitation on the input ultrasonic signal amplitude is shown by numerical simulations, and such a nonlinear ultrasonic response is experimentally observed in the zone with a high density of microstructural defects.
Ultrasonic thickness measurement of mechanical structures is one of the most popular and commonly used nondestructive methods for various kinds of process control and corrosion monitoring. With ultrasonic propagation speed being temperature-dependent, the thickness measurement can be performed reliably only when the thermal profile is completely known. Most conventional techniques assume the temperature of the test structure is uniform and at room temperature across its thickness. Such assumptions may lead to large errors in the thickness measurement, especially when there are significant temperature variations across the thickness. State-of-the-art techniques use external temperature measurements or implement iterative methods to compensate for the unknown thermal profiles. However, such techniques produce unsatisfactory results when the heat distribution is complex or varies rapidly with time. In this work, we propose a two-sensors technique, using both compressive and shear excitations, with a non-iterative rapid data processing method for accurate thickness measurement under arbitrary time-variant thermal profile. The independent behavior of shear and compressive waves is used to formulate a real-time thickness estimation technique. The developed technique is experimentally validated on a steel plate with fixed acoustic sensors. Test results show that the error in thickness estimation can be reduced by up to 98% compared to conventional thickness gauging methods.
Macrolides are a diverse class of hydrophobic compounds characterized by a macrocyclic lactone ring and distinguished by variable side chains/groups. Some of the most well characterized macrolides are toxins produced by marine bacteria, sea sponges, and other species. Many marine macrolide toxins act as biomimetic molecules to natural actin-binding proteins, affecting actin polymerization, while other toxins act on different cytoskeletal components. The disruption of natural cytoskeletal processes affects cell motility and cytokinesis, and can result in cellular death. While many macrolides are toxic in nature, others have been shown to display therapeutic properties. Indeed, some of the most well known antibiotic compounds, including erythromycin, are macrolides. In addition to antibiotic properties, macrolides have been shown to display antiviral, antiparasitic, antifungal, and immunosuppressive actions. Here, we review each functional class of macrolides for their common structures, mechanisms of action, pharmacology, and human cellular targets.
Stress-magnification factors for mismatch effect of middle surfaces at junctions in shell structures - structural mechanics
Aerodynamics, thermodynamics, thermal control, and structural mechanics for Mars probe entry shell
Feasibility of using laser radiation for detection and measurement of vibration of mechanical structures
Computer graphic techniques for numerical control, electrical network analysis, flight mechanics, structural analysis, and engineering drawing retrieval
Research projects on defect structure, mechanical behavior, electrical and optical properties, and thermodynamics of solid materials at university
Physical properties of near stoichiometric nickel- titanium alloy Nitinol and some structural- mechanical applications employing these properties
Magnitude limited random excitation effect on linear system response, using single degrees of freedom model representing idealized mechanical structure
The development of the lunar module landing gear subsystem through the Apollo 11 lunar landing mission is presented. The landing gear design evolved from the design requirement, which had to satisfy the structural, mechanical, and landing performance constraints of the vehicle. Extensive analyses and tests were undertaken to verify the design adequacy. Techniques of the landing performance analysis served as a primary tool in developing the subsystem hardware and in determining the adequacy of the landing gear for toppling stability and energy absorption. The successful Apollo 11 lunar landing mission provided the first opportunity for a complete flight test of the landing gear under both natural and induced environments.
The importance of long-range planning for space flight emergency systems is pointed out. Factors in emergency systems planning are considered, giving attention to some of the mission classes which have to be taken into account. Examples of the hazards in space flight include fire, decompression, mechanical structure failures, radiation, collision, and meteoroid penetration. The criteria for rescue vehicles are examined together with aspects regarding the conduction of rescue missions. Future space flight programs are discussed, taking into consideration low earth orbit space stations, geosynchronous orbit space stations, lunar operations, manned planetary missions, future space flight vehicles, the space shuttle, special purpose space vehicles, and a reusable nuclear shuttle.
A description and applications of a computer capability for determining the ultimate optimal behavior of a dynamically loaded structural-mechanical system are presented. This capability provides characteristics of the theoretically best, or limiting, design concept according to response criteria dictated by design requirements. Equations of motion of the system in first or second order form include incompletely specified elements whose characteristics are determined in the optimization of one or more performance indices subject to the response criteria in the form of constraints. The system is subject to deterministic transient inputs, and the computer capability is designed to operate with a large linear programming on-the-shelf software package which performs the desired optimization. The report contains user-oriented program documentation in engineering, problem-oriented form. Applications cover a wide variety of dynamics problems including those associated with such diverse configurations as a missile-silo system, impacting freight cars, and an aircraft ride control system.
An interorbital shuttle that can be utilized to carry payloads between low earth orbit (180 n mi, 37.6 deg) and lunar or geosynchronous orbits, and also to interplanetary trajectories is discussed. After each mission the stage returns to its earth parking orbit where it delivers the inbound payloads, and where it is maintained and refueled for the subsequent missions. The stage can also be utilized to carry large payloads (150 to 200 KLBS) to the Space Station orbit (270 n mi, 55 deg) when it is used as a second or parallel burn stage to the space shuttle booster. The mission and systems analysis, as well as the results of structural, mechanical and propulsion, and avionics subsystems analysis and design are described. A development plan and cost estimates are also included.
Structural resins have moduli and strengths which are different in tension and compression. The three-point-bend test is used extensively in their characterization. An investigation is performed to derive all the equations needed for the analysis and test data reduction of the three-point-bend test. The governing equations are derived using well-known linear structural mechanics principles and are represented graphically. The stress concentration effects in the vicinity of the load point are investigated, and failure stress and failure initiation are examined.
The theoretical and mechanical structure of the computer program is presented along with guidance on adaptation of the code to solution of a particular problem. Sample solutions are discussed for several problems, especially with respect to solution accuracy and speed as a function of parameters under control of the user. Construction of input data decks for sample problems is discussed.