Showing papers on "Shell (structure) published in 1975"

Elastostatics and Kinetics of Anisotropic and Heterogeneous Shell-Type Structures

Abstract: You may download books from anvatquynhon.xyz. Project is a high quality resource for free Books books.Here is the websites where you can find free eBooks. You have the option to browse by most popular titles, recent reviews, authors, titles, genres, languages and more.Look here for bestsellers, favorite classics and more.The anvatquynhon.xyz is home to thousands of free audiobooks, including classics and out-of-print books. These books are compatible for Kindles, Nooks, iPads and most e-readers.

Scattering of electromagnetic waves by an optically active spherical shell

Abstract: The scattering of electromagnetic waves by a spherical shell with intrinsic optical activity is calculated exactly from electromagnetic theory using the constitutive relations for an optically active, isotropic medium. The solution so obtained reduces to the standard solution in the limit of equal refractive indices for left− and right−circularly polarized waves. Expressions are given for single−particle cross sections and scattering matrix elements as well as circular dichroism and optical rotation for an aggregate of shells. These expressions are potentially applicable to the calculation of scattering contributions to optical rotatory dispersion and circular dichroism spectra for those particles of biological origin which can be modeled by an optically active shell.

Collapse of Long Cylindrical Shells under Combined Bending and Pressure Loads

Abstract: The nonlinear collapse behavior of long cylindrical shell structures subject to a bending load only or combined bending and uniform normal pressure loads is studied using the STAGS computer code. Two modes of nonlinear collapse are investigated to determine maximum strength. One mode of collapse is described by circumferential flattening of the cylinder cross section, while the other mode is represented by axial wrinkling in the region of maximum compression. Results compare favorably with available published data for cylinders loaded by pure bending, and results are presented for combined loads which have not been previously reported. The collapse loads obtained in this study show that current design criteria are conservative except for a narrow range of length-to-radius ratios and pressures.

Linear Simulations of Boussinesq Convection in a Deep Rotating Spherical Shell

Abstract: We present extensive linear numerical simulations of Boussinesq convection in a rotating spherical shell of finite depth. The motivation for the study is the problem of general circulation of the solar convection zone. We solve the marching equations on a staggered grid in the meridian plane for the amplitudes of the most unstable Fourier mode of longitudinal wavenumber m between 0 and 24, for Taylor number T between 0 and 106, at a Prandtl number P=1, for a shell of depth 20% of the outer radius. Stress-free, fixed-temperature boundary conditions are used at the inner and outer bounding surfaces. Modes of two symmetries, symmetric and antisymmetric about the equator, are studied. The principal results are as follows: Increasing Taylor number T splits the most unstable solutions for each m into two classes: a broad band of high m solutions which peak at or near the equator, and a small number of low m solutions which peak at or near the poles. The equatorial modes are unstable at lower Rayleigh n...

Position determining apparatus and transducer therefor

Abstract: An apparatus for determining the position of a movable element or stylus which is movable in a data space. In accordance with the invention there are provided first and second spaced receivers, each receiver comprising a hollow shell of piezoelectric material, which may be cylindrical or spherical in shape, and resilient conductive means coupled across the inner and outer surfaces of the shell. Means are provided for periodically generating a source of sound waves for travel between the stylus and the first and second receivers. Timing means are coupled to the receivers and synchronized with the generation of the sound waves for measuring transit time of the sound waves between the source and receivers. Computing means are employed to determine the positional coordinates of the stylus in a desired coordinate system, such as rectangular coordinates. In an embodiment of the invention the first and second receivers have conductive mesh loaded within the shell and in contact with the inner surface of the shell. In this embodiment a spring contact is coupled to the outer surface of the shell. In an embodiment of the invention the movable element or stylus is passive and means are provided for periodically generating sound waves at a source position spaced from the movable element. This eliminates the need for an "active" stylus and the problems associated therewith.

Composite building module

Abstract: A monolithic-like, composite building module such as a wall panel having a core of rigid foam encased in a shell made of fiber reinforced cement. The composite module can be made by forming a supported open shell made of a hardened mixture of cement and fibers, introducing a rigid foamable polymer into the open shell, closing the open shell with a cover member made of a hardened mixture of cement and glass fibers and thereafter holding the cover member in place while polymer foam fills the interior of the enclosed shell.

Zero force printed circuit board connector

Abstract: A zero force printed circuit board connector in which two rows of resilient contacts are mounted on opposite sides of a printed circuit board receiving slot in a connector housing. The upper ends of the contacts in the two rows are inclined toward each other. A hollow shell is also mounted over the contacts inside the housing and is vertically movable within the housing. The shell has a slot therein aligned with the slot in the outer housing. An elongated cam rod inside the outer housing is longitudinally movable to shift the shell downwardly to cam actuate the contacts.

A method for determining the dielectric constant and the conductivity of membrane-bounded particles of biological relevance.

Abstract: Numerical assessment is made regarding Pauly and Schwan's theory which describes the dielectric behaviour of a suspension of “shell spheres” as a model of biological membrane-bounded particles. The results indicate that approximate expressions of the theory may give rise to serious errors when applied to particles smaller than about 1 Μm in diameter. With a view to performing analysis according to a general expression of the theory, some of the characteristic responses of dielectric parameters upon changes in phase parameters are examined with particular reference to some numerical ranges of biological interest. On this basis a simplified and systematic procedure is proposed for estimating the phase parameters of particles whose shell phase can be regarded as non-conductive. As the application of the procedure proposed, a set of dielectric data of a synaptosome suspension is analyzed, so that the following three phase parameters are successfully determined: membrane capacitance (or shell phase dielectric constant), internal phase conductivity and internal phase dielectric constant. Some limitations of the procedure are discussed for the cases of conducting shells and small particles.

Dynamic Stability of Cylindrical Shells Under Step Loading

Abstract: A study has been made to determine the dynamic stability of an imperfect circular cylindrical shell subject to a step loading in the axial direction. In the analysis, the radial displacement of the shell is approximated by a finite degree of freedom system. To assure that the created model is proper, its static buckling behavior was studied. It was found that the model gives the proper imperfection sensitivity behavior. The dynamic analysis includes not only the effect of the radial inertia, but also that due to the axial inertia in an approximate manner. The critical loads are determined by numerical integration of the equation of motion. In addition a study is carried out to consider the effects of wave number of the radial mode shape, mass on the loaded edge of the shell and damping of the axial motion. Compared with the static case, there is a significant reduction of the dynamic buckling load for the high wave numbers of the radial modes. Also, there is a critical clamping value, above which the dynamic buckling load is close to the static buckling load. The dynamic buckling load approaches half of the static buckling load with increasing mass on the loading edge. Through the parametric studies of the wave number, mass, and damping factor it is concluded that due to frequency coupling between axial and radial motions, the axial inertia plays an essential role in characterizing the dynamic instability of a finite length shell.

An analysis of the growth bands and ridges of barnacle shell plates

Abstract: Periodic structures indicating discontinuous growth of shell wall plates have been observed in thin sections of shell and on the outer surface of shell plates of many species of operculate (Bourget, 1975). When sectioned and etched the shell plates appear to be composed of successive thin layers of shell material, each layer consisting of a few rows of fine crystals. Where two layers are adjoined, a dark line, marking the junction of two incremental zones, is clearly visible. The thin layers of shell have been termed growth bands whereas the junction of adjoining layers will be referred to as the growth line.

Protective helmet with liner means

Abstract: A protective helmet comprising a shell, and liner means positioned on the inside of the shell for absorbing impacts applied against the helmet. The liner means has a plurality of fluid-filled chamber means generally aligned intermediate the wearer's head and the shell, with at least two of the aligned chamber means being deformable in differing amounts responsive to a given force level applied against the helmet.

A triangular thin shell finite element: Linear analysis

Abstract: The formulation of the linear stiffness matrix for a doubly-curved triangular thin shell element, using a modified potential energy principle, is described. The strain energy component of the potential energy is expressed in terms of displacements and displacement gradients by use of consistent Koiter strain-displacement equations. The element inplane and normal displacement fields are approximated by complete cubic polynomials. The interelement displacement admissibility conditions are met in the global representation by imposition of constraint conditions on the interelement boundaries; the constraints represent the modification of the potential energy. Errors due to the nonzero strains under rigid body motion are shown to be of small importance for practical grid refinements through performance of extensive comparison analyses.

Armor piercing projectile

Abstract: An armor piercing projectile configuration which provides strength, rigidity and mass properties sufficient to permit long thin armor piercing cores to be fired from guns in a stable and accurate manner. The core is supported at both ends in such a way that a monocoque skin or shell provides rigidity and the space between the core and the shell is filled with rigid material or structure so as to support the core throughout substantially all of its length. The shell is of relatively high density adding to the lateral/transverse moment of inertia ratio to provide gyroscopic stability for the long thin core.

Impact-absorbing helmet

Abstract: An impact-absorbing helmet comprising an inner, substantially-stationary, shell member formed as an integral part of the base member, including a separate outer shell member superposed over the inner shell member and rotatably attached thereto, the rotation thereof being about the vertical axis of the helmet, whereby any tangential impact received by the outer shell will cause the outer shell to rotate, thereby absorbing the blow thereto, wherein the outer shell is held in rotational, spaced relationship by a plurality of bearing units interdisposed therebetween.

Non-linear modal equations for thin elastic shells

Abstract: In this paper we derive non-linear modal equations for thin elastic shells of arbitrary geometry. Geometric non-linearities are accounted for by utilizing the strain-displacement relations of the Sanders-Koiter non-linear shell theory. Arbitrary initial imperfections are accounted for and the shell thickness is free to vary within the limits of thin shell theory. The derivation gives the coefficients of the modal equations as integral expressions over the surface of the shell. The resulting equations are well-suited for practical applications. Weighting factors are introduced to allow for reduction of our results to the Love shell theory and to the Donnell approximation. The equations are specialized for a finite simply supported circular cylinder and numerical results are compared to those previously published in the literature.

Land erosion protection on a rock cutter

Abstract: Cone shell erosion between inserts is substantially reduced by positioning small, flat-topped compacts in the vulnerable cutter shell areas. At least one row of substantially outwardly projecting formation contacting inserts are located on the rock cutter. A row of substantially flush compacts are embedded in the cutter shell alternately positioned between the outwardly projecting formation contacting inserts.

Stability of Cantilever Shells under Wind Loads

Abstract: Static stability analysis of clamped-free cylindrical shells subjected to wind pressure is presented, using the energy theory of buckling. The criterion used is the vanishing of the second variation of potential energy, i.e., expressed in terms of prebuckling membrane strains and the assumed virtual displacement components. The prebuckling analysis has been carried out using Donnell's linear shell theory. Numerical results are presented for various shell geometries. Supporting experimental evidence is also provided. The effect of relaxing the axial displacement and rotation at the clamped base has also been theoretically studied. Current engineering practice of determining buckling load for maximum uniform pressure condition is shown to be conservative.

Combustor liner structure

Abstract: An air-cooled combustor liner is constructed of a continuous, constant-thickness, annular shell having a plurality of rings attached to the inner surface thereof to direct the flow of coolant air entering the shell by way of apertures formed therein, along the inner surface of the shell to provide a film cooling function. The rings, which are fabricated to desired dimensions sufficient to prevent significant thermal distortion which would cause flow restriction, are secured to the inner surface of the shell by brazing or the like.

Positional Instabilities in a Tokamak with a Resistive Shell

Abstract: The investigation of positional instabilities, that is, vertical displacement and horizontal expansion of the plasma loop, is extended to a tokamak with a resistive shell. The shell current induced by a small displacement of the current-carrying plasma column produces a restoring force, which contributes to the stabilization. The quantitative analysis of the effect due to the shell shows that the finiteness of the minor radius of the plasma column reduces the effective skin time of the shell τs from the intrinsic one. Consequently it is shown that although the stability condition is not altered, a resistive shell restrains the growth rate of the instability to the order of τs-1, in a wider region than the stable one.

Device for preventing ice formation on parts of aircraft

Abstract: A device for preventing ice formation on parts of aircraft-support surfaces (wings or aerofoils), propellers, rotor blades or the like-comprises electrical resistance heaters embedded in a shell of thermally conducting material (e.g. aluminium sheet or moulding) sheathing the aircraft part. Thermally insulating, thermally conducting and electrically insulating layers may be provided within the shell. The heaters, or some of them, may be controlled by a temperature sensor in or on the shell.