Mode localization experiments on a ribbed antenna
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Levine-West, M. B.↗
Engineering topics
Salama, M. A.
Publications and source records attributed to Salama, M. A..
Model localization experiments on a ribbed antenna
In this paper, the model localization (ML) phenomenon is investigated experimentally and analytically to determine the influence of its parameters. For this purpose, a full-scale 12-rib loosely-coupled antenna testbed with small imperfections is dynamically tested for various levels of inter-rib coupling stiffness and excitation force. The experimental results are described herein. Using a simplified numerical model of the structure, a sensitivity analysis of the modal behavior is also performed. The numerical and experimental results are shown to agree remarkably well, thereby providing conclusive validation of the ML phenomenon on a testbed having the dynamic characteristics of space structures.
Levine-West, M. B.↗
Experimental Parallel-Processing Computer
Master processor supervises slave processors, each with its own memory. Computer with parallel processing serves as inexpensive tool for experimentation with parallel mathematical algorithms. Speed enhancement obtained depends on both nature of problem and structure of algorithm used. In parallel-processing architecture, "bank select" and control signals determine which one, if any, of N slave processor memories accessible to master processor at any given moment. When so selected, slave memory operates as part of master computer memory. When not selected, slave memory operates independently of main memory. Slave processors communicate with each other via input/output bus.
Mcgregor, J. W.↗
Algorithms for Finite-Element Equations
Five direct and five iterative algorithms for finite element equations in linear equilibrium problems investigated for number of parallel computer architectures and their basic computation methods compared.
Salama, M. A.↗
Estimating Design Loads in Coupled Vibrating Structures
Approximate spectral analysis faster and less expensive than transient analysis. Method of vibration analysis combines separate modes of spacecraft and launcher to determine approximate conditions for resonance. Useful for analysis of any complex structure made up of substructures not coupled too closely; however important to note, method includes effect of dynamic impedance between launcher and payload.
Trubert, M. R.↗
Methods for Estimating Payload/Vehicle Design Loads
Several methods compared with respect to accuracy, design conservatism, and cost. Objective of survey: reduce time and expense of load calculation by selecting approximate method having sufficient accuracy for problem at hand. Methods generally applicable to dynamic load analysis in other aerospace and other vehicle/payload systems.
Chen, J. C.↗
Dynamic stability of multilayer sandwich plates
Report studies equations for analyzing effects of periodic inplane loads, using contemporary variational principle for dynamics.
Salama, M. A.↗
On the thermoelastic analysis of solar cell arrays and related material properties
Accurate prediction of failure of solar cell arrays requires accuracy in the computation of thermally induced stresses. This was accomplished by using the finite element technique. Improved procedures for stress calculation were introduced together with failure criteria capable of describing a wide range of ductile and brittle material behavior. The stress distribution and associated failure mechanisms in the N-interconnect junction of two solar cell designs were then studied. In such stress and failure analysis, it is essential to know the thermomechanical properties of the materials involved. Measurements were made of properties of materials suitable for the design of lightweight arrays: microsheet-0211 glass material for the solar cell filter, and Kapton-H, Kapton F, Teflon, Tedlar, and Mica Ply PG-402 for lightweight substrates. The temperature-dependence of the thermal coefficient of expansion for these materials was determined together with other properties such as the elastic moduli, Poisson's ratio, and the stress-strain behavior up to failure.
Salama, M. A.↗
Thermoelastic analysis of solar cell arrays and their material properties
Announced report discusses experimental test program in which five different solar cell array designs were evaluated by subjecting them to 60 thermal cycles from minus 190 deg to 0.0 deg. Results indicate that solder-coated cells combined with Kovar n-interconnectors and p-interconnectors are more durable under thermal loading than other configurations.
Salama, M. A.↗
Thermoelastic analysis of solar cell arrays and their material properties
Description of a thermoelastic stress analysis procedure for predicting the thermally induced stresses and failures in silicon solar cell arrays. A prerequisite for the analysis is the characterization of the temperature-dependent thermal and mechanical properties of the solar cell materials. Extensive material property testing was carried out in the temperature range from -200 to +200 C for the filter glass, P- and N-type silicon, interconnector metals, solder, and several candidate silicone rubber adhesives. The analysis procedure is applied to several solar cell array design configurations, which were tested in the Space Molecular Sink. Results of the analysis indicate the optimum design configuration with respect to materials and geometry, effect of the solder coating, and effect of the interconnector geometry.
Salama, M. A.↗
Thermoelastic analysis of solar cell arrays and their material properties
A thermoelastic stress analysis procedure is reported for predicting the thermally induced stresses and failures in silicon solar cell arrays. A prerequisite for the analysis is the characterization of the temperature-dependent thermal and mechanical properties of the solar cell materials. Extensive material property testing was carried out in the temperature range -200 to +200 C for the filter glass, P- and N-type silicon, interconnector metals, solder, and several candidate silicone rubber adhesives. The analysis procedure is applied to several solar cell array design configurations. Results of the analysis indicate the optimum design configuration, with respect to compatible materials, effect of the solder coating, and effect of the interconnector geometry. Good agreement was found between results of the analysis and the test program.
Salama, M. A.↗