THE STABILITY OF A THIN MOVING ELASTIC STRIP SUBJECTED TO RANDOM PARAMETRIC EXCITATIONS

1997 ◽  
Vol 206 (2) ◽  
pp. 280-285 ◽  
Author(s):  
P. Kozić ◽  
R. Pavlović
Keyword(s):  
Elastic Strip ◽  
The Stability

scholarly journals On the stability under shearing forces of a flat elastic strip

1924 ◽  
Vol 105 (733) ◽  
pp. 582-607 ◽  
Keyword(s):  
Bending Moment ◽  
Elastic Stability ◽  
Elastic Strip ◽  
Plate Girders ◽  
Uniform Shear ◽  
Transverse Vibrations ◽  
Annular Disc ◽  
The Stability ◽  
Limiting Case ◽  
Total Shear

1. The investigation relates to flat elastic strip, of uniform breadth, thickness and material, upon which a uniform shear is imposed by tangential tractions applied at its edges and in its plane. The tractions appear in the expression for the change of potential energy which occurs when the strip is bent, and they must therefore affect both the modes and the frequencies of its free transverse vibrations. If sufficiently intense, they will bring about a condition of limiting elastic stability, since they can neutralize, in certain types of distortion, the restoring effects of the flexural stresses. The results have some bearing on the stability of the webs of deep plate girders, which take the greater part of the total shear transmitted. The correspondence must not, however, be pressed unduly, because in a girder uniform shear will be accompanied by a varying bending moment which imposes additional stresses upon the web. It is more accurate to describe the sheared strip (of which the length, in this paper, has been assumed to be infinite) as the limiting case either of a narrow annular disc, or of a short tube, subjected to torsion. The similarity of the three problems is illustrated by the specimens shown in fig. 1, which have buckled under conditions of limiting elastic stability.

Instability of an Elastic Strip Hanging in an Airstream

1975 ◽  
Vol 42 (1) ◽  
pp. 195-198 ◽  
Author(s):  
S. K. Datta ◽  
W. G. Gottenberg
Keyword(s):  
Small Amplitude ◽  
Critical Speed ◽  
Bending Stiffness ◽  
Elastic Strip ◽  
Approximate Analysis ◽  
Rectangular Strip ◽  
Length Width ◽  
Air Speed ◽  
The Stability

The stability of a long, thin elastic strip hanging vertically in a downward flowing airstream was considered. Experimentally it was observed that the strip remained essentially motionless or at most developed a small amplitude bounded oscillation as the air speed was increased until a critical speed was attained beyond which violent oscillations of the free-ended strip occurred. A linear approximate analysis was performed for this problem which accounted for shape-induced lift and bending stiffness of the strip and which closely predicted critical air speeds for this instability. The critical air speed was studied as a function of the length, width, and thickness of the rectangular strip.

scholarly journals Deformations and Stability of an Elastica Subjected to an Off-Axis Point Constraint

2010 ◽  
Vol 77 (3) ◽  
Author(s):  
Jen-San Chen ◽  
Wei-Chia Ro
Keyword(s):  
Symmetry Breaking ◽  
Natural Frequencies ◽  
Buckling Load ◽  
Elastic Strip ◽  
Eulerian Description ◽  
Symmetric Configuration ◽  
Equilibrium Configurations ◽  
The Stability ◽  
Calculated Equilibrium ◽  
Symmetry Breaking Bifurcation

This paper studies, both theoretically and experimentally, the deformation, the vibration, and the stability of a buckled elastic strip (also known as an elastica) constrained by a space-fixed point in the middle. One end of the elastica is fully clamped while the other end is allowed to slide without friction and clearance inside a rigid channel. The point constraint is located at a specified height above the clamping plane. The elastic strip buckles when the pushing force reaches the conventional buckling load. At this buckling load, the elastica jumps to a symmetric configuration in contact with the point constraint. As the pushing force increases, a symmetry-breaking bifurcation occurs and the elastica evolves to one of a pair of asymmetric deformations. As the pushing force continues to increase, the asymmetric deformation experiences a second jump to a self-contact configuration. A vibration analysis based on an Eulerian description taking into account the sliding between the elastica and the point constraint is described. The natural frequencies and the stability of the calculated equilibrium configurations can then be determined. The experiment confirms the two jumps and the symmetry-breaking bifurcation predicted theoretically.

The Stability of a Moving Elastic Strip Subjected to Random Parametric Excitation

1979 ◽  
Vol 46 (2) ◽  
pp. 404-410 ◽  
Author(s):  
F. Kozin ◽  
R. M. Milstead
Keyword(s):  
Asymptotic Stability ◽  
Stochastic Systems ◽  
Equations Of Motion ◽  
Stochastic Equations ◽  
Thin Strip ◽  
Elastic Strip ◽  
Moving Strip ◽  
The Stability ◽  
Sufficiency Conditions

The dynamic stability of a thin strip, traveling axially, at a constant speed between two roller supports is investigated for the case of zero mean random in-plane loading. Galerkin’s method is used to reduce the equations of motion to a set of fourth-order stochastic equations. An extention of the method first proposed by Wu and Kozin is developed which allows determination of the sufficiency conditions to guarantee Almost Sure Asymptotic Stability of stochastic systems of order greater than two. Using this method, results in terms of the variance of the random loadings on the moving strip are derived. It is found that the critical noise level to guarantee stability of the strip decreases with increasing mode, approaching asymptotically a level determined solely by the strip stiffness.

The Nature of The Torsional Stability of a Monocoque Fuselage

1933 ◽  
Vol 37 (269) ◽  
pp. 411-422 ◽  
Author(s):  
Katsutada Sezawa
Keyword(s):  
Cylindrical Shell ◽  
Light Metal ◽  
Elastic Strip ◽  
Text Book ◽  
Mathematical Solution ◽  
First Approximation ◽  
Solutions Of Equations ◽  
The Stability ◽  
Torsional Stability ◽  
Theoretical Side

Although the problem of the stability of a fuselage that is subjected to torsional force is important in connection with the case of light metal construction of an aeroplane in flight, the theoretical side of the problem does not seem to have received much attention. This is probably because of the difficulty of obtaining its mathematical solution even in the case where the fuselage is assumed to be a circular hollow cylinder. Thus, I studied the problem in assuming that the fuselage is a cylindrical shell for the first approximation. Southwell and Skan have dealt with the stability of a plane elastic strip due to edge shearing forces, but their result cannot be applied to the problem of the cylindrical shell unless its length is very short. Schwerin seems to be the only one who has written on the torsional stability of a cylindrical shell. Although his method of constructing the differential equations of the equilibrium of a cylindrical shell has been chiefly derived from Love's text book, and appears correct in the main, yet owing to the certain apparent particularities on his part his solutions of equations are open to grave doubts.

Open discussion

1982 ◽  
Vol 99 ◽  
pp. 605-613
Author(s):  
P. S. Conti
Keyword(s):  
Buenos Aires ◽  
Large Mass ◽  
List Type ◽  
Common Phenomenon ◽  
Open Discussion ◽  
The Stability ◽  
Ring Nebulae

Conti: One of the main conclusions of the Wolf-Rayet symposium in Buenos Aires was that Wolf-Rayet stars are evolutionary products of massive objects. Some questions:–Do hot helium-rich stars, that are not Wolf-Rayet stars, exist?–What about the stability of helium rich stars of large mass? We know a helium rich star of ∼40 MO. Has the stability something to do with the wind?–Ring nebulae and bubbles : this seems to be a much more common phenomenon than we thought of some years age.–What is the origin of the subtypes? This is important to find a possible matching of scenarios to subtypes.

Symmetric Multistep Methods Revisited: II. Numerical Experiments

1999 ◽  
Vol 173 ◽  
pp. 309-314 ◽  
Author(s):  
T. Fukushima
Keyword(s):  
Multistep Methods ◽  
Computational Time ◽  
Integration Time ◽  
Implicit Methods ◽  
Symmetric Methods ◽  
Celestial Bodies ◽  
The Stability ◽  
Predictor Corrector ◽  
Symmetric Multistep Methods ◽  
Integration Errors

AbstractBy using the stability condition and general formulas developed by Fukushima (1998 = Paper I) we discovered that, just as in the case of the explicit symmetric multistep methods (Quinlan and Tremaine, 1990), when integrating orbital motions of celestial bodies, the implicit symmetric multistep methods used in the predictor-corrector manner lead to integration errors in position which grow linearly with the integration time if the stepsizes adopted are sufficiently small and if the number of corrections is sufficiently large, say two or three. We confirmed also that the symmetric methods (explicit or implicit) would produce the stepsize-dependent instabilities/resonances, which was discovered by A. Toomre in 1991 and confirmed by G.D. Quinlan for some high order explicit methods. Although the implicit methods require twice or more computational time for the same stepsize than the explicit symmetric ones do, they seem to be preferable since they reduce these undesirable features significantly.

Uniformity of Magnification from Different Electron Microscopes

1967 ◽  
Vol 25 ◽  
pp. 32-33
Author(s):  
Godfrey C. Hoskins ◽  
V. Williams ◽  
V. Allison
Keyword(s):  
Diffraction Grating ◽  
The Other ◽  
Carbon Replica ◽  
Electron Microscopes ◽  
The Stability

The method demonstrated is an adaptation of a proven procedure for accurately determining the magnification of light photomicrographs. Because of the stability of modern electrical lenses, the method is shown to be directly applicable for providing precise reproducibility of magnification in various models of electron microscopes.A readily recognizable area of a carbon replica of a crossed-line diffraction grating is used as a standard. The same area of the standard was photographed in Phillips EM 200, Hitachi HU-11B2, and RCA EMU 3F electron microscopes at taps representative of the range of magnification of each. Negatives from one microscope were selected as guides and printed at convenient magnifications; then negatives from each of the other microscopes were projected to register with these prints. By deferring measurement to the print rather than comparing negatives, correspondence of magnification of the specimen in the three microscopes could be brought to within 2%.

Effect of Improved ThO2 Particle Dispersion in Nickel on High-Temperature Strength

1970 ◽  
Vol 28 ◽  
pp. 444-445
Author(s):  
E. R. Kimmel ◽  
H. L. Anthony ◽  
W. Scheithauer
Keyword(s):  
High Temperature ◽  
Metal Matrix ◽  
Oxide Particle ◽  
Oxide Phase ◽  
Dislocation Motion ◽  
Particle Dispersion ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
Oxide Particles ◽  
The Stability

The strengthening effect at high temperature produced by a dispersed oxide phase in a metal matrix is seemingly dependent on at least two major contributors: oxide particle size and spatial distribution, and stability of the worked microstructure. These two are strongly interrelated. The stability of the microstructure is produced by polygonization of the worked structure forming low angle cell boundaries which become anchored by the dispersed oxide particles. The effect of the particles on strength is therefore twofold, in that they stabilize the worked microstructure and also hinder dislocation motion during loading.

An Analysis of Dissociation of Molecules in a High Resolution Electron Microscope

1973 ◽  
Vol 31 ◽  
pp. 486-487
Author(s):  
Mihir Parikh
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Cross Sections ◽  
Resolving Power ◽  
Peak Intensity ◽  
Molecular Film ◽  
Resolution Electron ◽  
Dissociation Cross Section ◽  
High Resolution Electron Microscope ◽  
The Stability

It is well known that the resolution of bio-molecules in a high resolution electron microscope depends not just on the physical resolving power of the instrument, but also on the stability of these molecules under the electron beam. Experimentally, the damage to the bio-molecules is commo ly monitored by the decrease in the intensity of the diffraction pattern, or more quantitatively by the decrease in the peaks of an energy loss spectrum. In the latter case the exposure, EC, to decrease the peak intensity from IO to I’O can be related to the molecular dissociation cross-section, σD, by EC = ℓn(IO /I’O) /ℓD. Qu ntitative data on damage cross-sections are just being reported, However, the microscopist needs to know the explicit dependence of damage on: (1) the molecular properties, (2) the density and characteristics of the molecular film and that of the support film, if any, (3) the temperature of the molecular film and (4) certain characteristics of the electron microscope used

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