Plain Ring Research Articles

Strength of damage ring and orthogonally stiffened shells—part I: Plain ring stiffened shells

This paper is the first of two parts describing the procedure of, and results from, a series of tests on ring and orthogonally stiffened thin-walled shells. The primary purpose of the work was to investigate the collapse behaviour of the shells subjected to simulated damage and then tested under a combination of external pressure and axial compressive loading. The test specimens consisted of two five-bay cylinders stiffened with plain ring stiffeners; two three-bay cylinders stiffened with T-ring stiffeners and two three-bay orthogonally stiffened cylinders, one with 20 stringers, and the other with 40. This Part I deals with the tests on the plain ring stiffened cylinders. A major conclusion that can be drawn from the results of these few tests is that although the design of the plain rings was adequate to prevent general buckling of the undamaged shells, they were ineffective in limiting the area of initial damage when the shell was subjected to pressure loading.

Analysis of spread in ring rolling

Hill's general method of analysis (variational procedure), combining flexibility with rigorous principles, is applied to predict spread during plain ring rolling. The use of ‘dual stream functions’ in selecting a single approximating velocity field from a ‘sufficiently wide’ orthogonalizing family is demonstrated.

A thin−film ring distributed−feedback laser

We report the construction and operation of a ring distributed−feedback laser formed by incorporating a periodic structure as part of the plain ring laser. The characteristics of the observed spectrum are in general agreement with theoretical analysis. Mode selection and bandwidth narrowing have been observed.

The Deflexion of a Thick Plain Ring under a Uniformly Distributed Couple

Several theoretical methods of estimating the deflexion of a thick plain ring under a uniformly distributed couple have been published, both in this country and in the U.S.A. Probably the best-known of these theories is that of Dr. R. W. Bailey.† In all cases the treatment has not been rigid from a mathematical point of view, the axial or shear forces in the ring notably being neglected, and the load being assumed concentrated on particular loading circles whereas in fact it is distributed over an appreciable area. The present paper attempts to treat the problem in a more rigid manner, with due consideration of the effect of load distribution. Expressions for the axial and radial deflexions, and the axial, shear, radial, and circumferential stresses in the ring are developed, and values of these functions are obtained for a wide range of ring dimensions, and are compared with the values of similar quantities obtained by the use of the theory of Dr. R. W. Bailey.

Some polarization phenomena in magnetic materials, with special reference to nickel-iron alloys

Asymmetry of E-I loops for nickel-iron cores under alternating magnetizing forces is shown to be due to residual polarization, the distribution of which throughout the crosssection of the stamping is different from the distribution of the flux due to the applied alternating magnetizing force. It is also shown that such polarization may, under certain conditions, bein different directions simultaneously in the inner and outer parts of thestamping. The polarization can be removed by applying a relatively large alternating magnetizing force and reducing it slowly to zero. Curves are produced showing the amount of polarizing flux removed by different values of alternating magnetizing force, tarting with a known value of residual flux. It is shown that in the case of mumetal the curves are different when the residual flux is caused by switching off alternating and direct current respectively. Other curves show the marked increase in polarizing flux produced bydirect current when an alternating magnetizing force of suitable valueis superimposed. The reduction of apparent permeability due to residual polarization is also shown. Strong polarization is found to occur, both in nickel-iron and in silicon-steel cores, under conditions in which capacitanceloading of the secondary winding produces resonance with even harmouics, provideda small initial polarization is present. Initial polarization sufficient toallow this phenomenon to occur is found to be usually present, evenwhen thenormal loop is almost symmetrical. The presence of even harmonics in the magnetizing current, as may occur, for instance, when the source of supply iathermionic valve, is also found to cause polarization. With certain values of capacitance loading of polarized specimens, sub-harmonics are produced. The asymmetry of E-I loops or specimens with residual polarization is found to be less apparent as the frequency is raised above 50 cycles per sec. It is pointed out that these phenomena should be taken into account in the design and operation of electromagnetic apparatus, but that cores of the more usual commercial forms will not exhibit the phenomena to the same extent as the plain ring stampings used in most of the tests described.