4,856 research outputs found
Implementation of elastic-plastic structural analysis into NASTRAN
Elastic-plastic analytic capabilities were incorporated into the NASTRAN program. The present implementation includes a general rigid format and additional bulk data cards as well as to two new modules. The modules are specialized to include only perfect plasticity of the CTRMEN and CROD elements but can easily be expanded to include other plasticity theories and elements. The practical problem of an elastic-plastic analysis of a ship's bracket connection is demonstrated and compared to an equivalent analysis using Grumman's PLANS program. The present work demonstrates the feasibility of incorporating general elastic-plastic capabilities into NASTRAN
DYCAST: A finite element program for the crash analysis of structures
DYCAST is a nonlinear structural dynamic finite element computer code developed for crash simulation. The element library contains stringers, beams, membrane skin triangles, plate bending triangles and spring elements. Changing stiffnesses in the structure are accounted for by plasticity and very large deflections. Material nonlinearities are accommodated by one of three options: elastic-perfectly plastic, elastic-linear hardening plastic, or elastic-nonlinear hardening plastic of the Ramberg-Osgood type. Geometric nonlinearities are handled in an updated Lagrangian formulation by reforming the structure into its deformed shape after small time increments while accumulating deformations, strains, and forces. The nonlinearities due to combined loadings are maintained, and stiffness variation due to structural failures are computed. Numerical time integrators available are fixed-step central difference, modified Adams, Newmark-beta, and Wilson-theta. The last three have a variable time step capability, which is controlled internally by a solution convergence error measure. Other features include: multiple time-load history tables to subject the structure to time dependent loading; gravity loading; initial pitch, roll, yaw, and translation of the structural model with respect to the global system; a bandwidth optimizer as a pre-processor; and deformed plots and graphics as post-processors
Development of a scanning electron mirror microscope
Scanning electron mirrors microscope design and developmen
The Shape of an Accretion Disc in a Misaligned Black Hole Binary
We model the overall shape of an accretion disc in a semi-detached binary
system in which mass is transfered on to a spinning black hole the spin axis of
which is misaligned with the orbital rotation axis. We assume the disc is in a
steady state. Its outer regions are subject to differential precession caused
by tidal torques of the companion star. These tend to align the outer parts of
the disc with the orbital plane. Its inner regions are subject to differential
precession caused by the Lense-Thirring effect. These tend to align the inner
parts of the disc with the spin of the black hole. We give full numerical
solutions for the shape of the disc for some particular disc parameters. We
then show how an analytic approximation to these solutions can be obtained for
the case when the disc surface density varies as a power law with radius. These
analytic solutions for the shape of the disc are reasonably accurate even for
large misalignments and can be simply applied for general disc parameters. They
are particularly useful when the numerical solutions would be slow.Comment: Accepted for publication in MNRA
SEPTEMBER 26, 1960 SOLAR COSMIC RAY EVENT
Solar cosmic ray event - september 26, 196
Raised cortisol excretion rate in urine and contamination by topical steroids
No abstract available
Solar wind observations with the ion composition instrument aboard the ISEE-3 ICE spacecraft
The principal observations obtained by the Ion Composition Instrument (ICI) flown on the ISEE-3/ICE spacecraft, which was in the solar wind from September 1978 to the end of 1982, before being directed to the far magnetotail of the Earth are discussed. Almost continuous observations were made of the abundances of 3He++, 4He++, O6+, O7+, Ne, Si and Fe in various charge states, and of their bulk speeds and temperatures. The results show that there is a strong tendency in the collisionless solar wind for the ionic temperatures to be proportional to the masses. For heavier ions these temperatures exceed typical coronal electron temperatures. 4He++, especially in high speed streams, moves faster than H+, and travels at the same speed as heavier ions. The mechanism leading to this heating and rapid streaming is still not entirely clear
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