Showing papers on "Shell (structure) published in 1981"
TL;DR: In this paper, the quasiconfiguration method is applied to fp shell nuclei and second order degenerate perturbation theory is shown to produce, for low lying states, the same results as large diagonalizations in the full ( f 7 2 p 3 2 p 1 2 f 5 2 ) n space, due to the operation of linked cluster mechanisms.
246 citations
TL;DR: Shell-breaking behavior of the crabs Ozius verreauxii Saussure and Eriphia squamata from the Bay of Panama is described and fish predation appears to enforce a close sympatry between smaller gastropods and their crab predators.
188 citations
TL;DR: A simple flat three-node triangular shell element for linear and nonlinear analysis is presented in this article, where the stiffness matrix with 6 degrees of freedom per node is obtained by superimposing its bending and membrane stiffness matrices.
177 citations
TL;DR: In this paper, a general analytical method is presented for evaluating the free vibration characteristics of a circular cylindrical shell with classical boundary conditions of any type, and the solution is obtained through a direct solution procedure in which Sanders' shell equations are used with the axial modal displacements represented as simple Fourier series expressions.
166 citations
Patent•
03 Mar 1981
TL;DR: In this article, an electric bulb is mounted on a base and enclosed by a shell which is at least partially translucent, whereby the shell functions as a light shade, the shell being spring-mounted on the base and therefore being depressible.
Abstract: An aroma-generating lamp structure including an electric bulb mounted on a base and enclosed by a shell which is at least partially translucent, whereby the shell functions as a light shade, the shell being spring-mounted on the base and therefore being depressible. Socketed on the base is a bottle filled with a liquid scent, the bottle being coupled to a pump having an actuating head which cooperates with the shell so that when the shell is depressed, liquid is sprayed onto an absorbent pad disposed within the shell in the proximity of the bulb. Heat from the bulb vaporizes the liquid to generate an aroma which is exuded through vents in the shell.
114 citations
01 Jan 1981
TL;DR: In this paper, a nonlinear finite element shell formulation is generalized to accomodate large membrane strains, and the formulation is demonstrated on the bending and inflation of a circular plate and the axisymmetric stretching of an annular plate.
Abstract: A previously developed nonlinear finite element shell formulation is generalized to accomodate large membrane strains. The formulation is demonstrated on the bending and inflation of a circular plate and the axisymmetric stretching of an annular plate. Both problems are modeled with a Mooney-Rivlin material and involve large membrane strains.
101 citations
TL;DR: In this paper, the authors compute the Casimir stress on a perfectly conducting cylindrical shell, due to quantum field fluctuations (zero-point energy) in both the interior and exterior regions, using a Green's dyadic formulation for the field strengths.
99 citations
TL;DR: In this article, a doubly curved superparamatric quadratic shell element is described as a model for the analysis of practical, non-classical structural configuration constructed of fiber reinforced laminated composites.
83 citations
TL;DR: In this paper, a finite element formulation of shells with large deflections including elastoplastic material behaviour is presented, with special emphasis on the simple 4-node quadrilateral.
67 citations
TL;DR: In this article, fractional parentage arguments were also applied to the linewidths of the 4f multiplet levels as observed in electron spectroscopy, and a similarity was predicted between the PES of a 4fn element and the BIS of an 4f14-n element.
Abstract: The partially filled 4f shell in rare earths gives rise to complex multiplet structure in both photoelectron spectroscopy (PES) and bremsstrahlung isochromat spectroscopy (BIS). The fractional parentage theory previously applied to PES is extended to BIS, and a similarity is predicted between the PES of a 4fn element and the BIS of a 4f14-n element. Fractional parentage arguments are also applied to the linewidths of the 4f multiplet levels as observed in electron spectroscopy.
65 citations
TL;DR: In this paper, the Coriolis effect on the first bending and first torsional frequencies of flat rotating low aspect ratio cantilever plates has been investigated using finite element method.
Abstract: The Coriolis effect on the first bending and first torsional frequencies of flat rotating low aspect ratio cantilever plates has been investigated using finite element method. The cantilever plate has been modelled using plane triangular shell elements with three nodes and eighteen degrees of freedom. Three typical skew angles (0, 45, and 90 degrees) and two aspect ratios (1 and 2) are considered in the analysis. In addition to the Coriolis effect other effects, namely the geometric stiffness and the supplementary stiffness, have been considered. The mass and stiffness matrices have been derived using area coordinates. It has been found that the effect of including Coriolis effect is to lower the first two frequencies. This effect is negligible when the skew angle is 90 degrees. In the other two cases, skew of 0 and 45 degrees, there is a noticeable effect on the first torsional mode frequency when the aspect ratio is unity and on the first bending mode frequency when the aspect ratio is 2. An inc...
TL;DR: In this paper, the analysis of the X-ray Debye-Scherrer lines of the fine gold particles of which sizes are in a range from 60 to 230 A, it was found that the thermal expansion coefficient as well as the lattice parameter are not different from those of the bulk crystal, while the characteristic temperature decreases monotonously with the decrease of the particle size.
TL;DR: In this paper, the authors show that the discrepancy can be explained by allowing neutron excitations from the d3/2 shell into the f7/2shell, which is a shell model that can be used to calculate the binding energies of the neutron-rich isotopes of sodium and magnesium.
Abstract: Standard shell-model calculations of the binding energies of the neutron-rich isotopes of sodium and magnesium are in strong disagreement with the experimental values near N=20. The authors show that the discrepancy can be explained by allowing neutron excitations from the d3/2 shell into the f7/2 shell.
TL;DR: A total Lagrangian formulation for large deformation analysis of shells by the finite element method is presented in this article, where a special discretization in the thickness direction is employed to permit solution of shell problems without numerical difficulties.
01 Jan 1981
TL;DR: In this paper, the authors extended previous endeavors of the authors on quasistatic plate and shell analysis and presented several sample problems of a two-and three-dimensional nature.
Abstract: Dynamical aspects of a general nonlinear finite element shell analysis procedure are described. The work extends previous endeavors of the authors on quasistatic plate and shell analysis. Several sample problems of a two- and three-dimensional nature are presented which demonstrate the applicability of the methodology.
Patent•
16 Apr 1981TL;DR: In this article, a thin film semiconductor gas sensor including a metal oxide sensor layer whose electrical resistance changes in dependence upon the nature and concentration of a gas being detected and having a heating element integrated therewith is improved by forming the sensor from a semiconductor body having a shell zone located relatively close to an outer surface of such body and being doped to the point of degeneration, with two spaced apart metal contact strips being positioned on such doped shell zone for connection with a current source.
Abstract: A thin film semiconductor gas sensor including a metal oxide semiconductor sensor layer whose electrical resistance changes in dependence upon the nature and concentration of a gas being detected and having a heating element integrated therewith is improved by forming the sensor from a semiconductor body having a shell zone located relatively close to an outer surface of such body and being doped to the point of degeneration, with two spaced apart metal contact strips being positioned on such doped shell zone for connection with a current source to heat the sensor.
Patent•
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15 Jun 1981
Abstract: An ear plug is described, which includes a shell formed of closed cell foam material, with the shell surface having a multiplicity of small bumps that also form the walls of cells which lie at the surface of the shell, whereby to avoid wrinkling when the shell is squeezed into the ear canal. A stem of resilient material lies freely moveable in the shell, and is short so it extends substantially no further than the open end of the shell.
TL;DR: A low resolution model for the virus is shown to be consistent with its composition as given by earlier physico-chemical measurements, and this model underestimates the thickness of the protein shell and that it in fact makes contact with the RNA at about 65 A.
TL;DR: Nacreous shell is shown to be less resistant than prismatic or crossed-lamellar shell to simulated components of whelk attack and Homogeneous shell is more resistant than other shell types to abrasion.
Abstract: The combination of an inner layer of nacre and an outer layer of simple prisms is thought to be phylogenetically the oldest molluscan shell type. Although nacre is very strong it is not as widely used as crossed-lamellar shell. Factors other than tensile strength or modulus of elasticity, such as resistance to abrasion or chemical attack, may have been important in the evolution of other shell types. Nacreous shell is shown to be less resistant than prismatic or crossed-lamellar shell to simulated components of whelk attack. Homogeneous shell is more resistant than other shell types to abrasion. A relationship between life-style and shell microstructure is suggested.
TL;DR: In this paper, the authors present a summary of the different theories used and examine the assumptions upon which each of them is based and show when it is more suitable to use a particular approximation and to indicate the errors it introduces.
TL;DR: In this paper, the axisymmetric free oscillations of a fluid-filled spherical shell are studied and the dynamic response of the shell is determined by the classical normal mode method, while a boundary layer approximation is employed for the compressible viscous fluid medium.
TL;DR: In this paper, the equations of motion derived from a Love-type theory are presented for laminated filament-wound cylindrical shells in which each layer is permitted an arbitrary fixed fiber orientation.
Abstract: The equations of motion, derived from a Love-type theory, are presented for laminated filament-wound cylindrical shells in which each layer is permitted an arbitrary fixed fiber orientation. A general method of solution is established, based upon the use of a complex finite Fourier transform. The frequency spectra of free natural vibrations are investigated for numerous single, bi- and tri-Iayered clamped or simply supported generally orthotropic shells. The effect of fiber orientation on the frequency response is found to be quite considerable in certain composite shells; for some shells the frequency is increased by a factor of 3.1 by simply choosing an optimal combination of fiber winding angles. Similar important effects are noted due to the combined action of shell heterogeneity and fiber winding angle.
TL;DR: Using a thin shell theory developed by Reissner, a nonlinear model for the in-plane bending of a curved pipe is described in this article, where it is shown how classical thin shell models of this component can be deduced on making certain simplifying assumptions concerning the mode of deformation.
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10 Aug 1981
TL;DR: In this paper, the first and second identical annular opposed shell members are held between outer symmetrical opposed disc sections of the respective hub-forming members, where each shell member has an outer inwardly positioned circumferential edge where each such shell member abuts the opposed shell member.
Abstract: The cord reel assembly comprises first and second identical hub-forming members. A plate is positioned between the inner ends of abutting cylindrical sections of the hub-forming members. First and second identical annular opposed shell members are held between outer symmetrical opposed disc sections of the respective hub-forming members. Each shell member has an outer inwardly positioned circumferential edge where each such shell member abuts the opposed shell member. A rivet-like member is provided for holding the cylindrical sections together with the plate situated between the inner ends of the cylindrical sections to form a hub assembly with each disc section bearing against one of the shell members to hold the shell members in place with the inner edges thereof in abutting relationship. Each shell member has a notch extending into the shell member from the outer circumferential edge thereof and adapted to register with an opposed identical notch in the opposed shell member. The plate has a radially extending slot therein adapted to be rotated into alignment with the notches when the notches are in registry with each other for receiving a loop of a cord. Manually manipulatable ribs are provided on the outer surface of each disc section of each hub-forming member for enabling the hub assembly to be rotated by hand relative to the shell members after a loop of cord has been inserted through the aligned notches and into the slot for winding up excess cord.
TL;DR: In this article, a finite element technique has been used to determine the natural frequencies of a pre-twisted and tapered plate mounted on the periphery of a rotating disc, which is idealized as an assemblage of three noded triangular shell elements with six degrees of freedom at each node.
Patent•
03 Jun 1981
TL;DR: In this paper, a rotary disk mounting and centering device for use in a disc file employing removable, flexible rotary discs comprises guides 52 for locating a disc 40 such that a central and circular locating hole 48 in the disc 40 is approximately parallel planar and coaxial with a circular recess 12 of substantially the same diameter as the hole 48, set in the flat top of a rotating cylindrical spindle 10.
Abstract: A disc mounting and centering device, for use in a disc file employing removable, flexible rotary discs comprises guides 52 for locating a disc 40 such that a central and circular locating hole 48 in the disc 40 is approximately parallel planar and coaxial with a circular recess 12 of substantially the same diameter as the hole 48, set in the flat top of a rotating cylindrical spindle 10, a frusto conical expandable shell 20 for insertion through the hole 48 into the recess 12 having a largest, unexpanded diameter less than that of the hole 48, a lip 22 at the largest diameter end of the shell 20, of greater diameter than the hole for engaging the disc 40 with the spindle 10 as the shell 20 enters the recess, and a frusto conical expander 30 for insertion into the shell 20 firstly to expand the shell 20 until it is constrained by the recess 12 and secondly, by applying axial force in excess of that required to expand the shell 20 for pressing the lip 22 against the spindle 10, with said excess force to clamp the disc 40.
01 Jan 1981
TL;DR: In this article, the stability of a cylindrical shell subjected to wind load is analyzed using numerical solution methods, and good agreement is derived with respect to both stability limit and buckling mode.
Abstract: The stability of a cylindrical shell subjected to wind load is analyzed using numerical solution methods. The multisegment direct integration as well as the finite element method are applied in linear analysis, and a nonlinear finite element algorithm is used to take into account the nonlinear prebuckling effects of the perfect and imperfect structure. The calculated results are compared with measurements, and good agreement is derived with respect to both stability limit and buckling mode.
01 Jan 1981
TL;DR: In this article, the authors present a progress report of some of the research that is conducted in finite element analysis of thin shell structures, including the isoparametric displacement-rotation thin shell element and the discrete-Kirchhoff-theory (DKT) plate/shell element.
Abstract: This paper represents a progress report of some of the research that we are conducting in the finite element analysis of thin shell structures. We consider our isoparametric displacement-rotation thin shell element and our discrete-Kirchhoff-theory (DKT) plate/shell element, which we are continuously refining for accurate and effective geometric and materially nonlinear analysis. In the paper we briefly discuss the locking phenomenon of the isoparametric element, the use of this element as a transition element between shell surfaces and in shell-solid transitions, and we give some results using the DKT element.
TL;DR: In this article, the resonant vibration frequencies of a fiber-reinforced, thick-wall, circular-cylindrical shell of finite length were analyzed using an iterative, yet exact, method.
Abstract: The resonant vibration frequencies of a fiber-reinforced, thick-wall, circular-cylindrical shell of finite length which is materially monoclinic are analyzed. The degree of material anisotropy precludes a closed-form solution and so an iterative, yet exact, method is used. The analytical method is validated by comparison of results with previously published results for a homogeneous, isotropic thin shell, and an orthogonally stiffened-thin shell modeled as orthotropic. Results for a materially monoclinic, thick-wall shell with free-free end conditions are compared with experimental results obtained by the present investigators.
01 Mar 1981-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, three types of surface features such as grooves, wrinkles, and laps have been recognized, which are associated with the mechanical behavior of the thermally stressed solidifying shell.
Abstract: Geometric features such as grooves, wrinkles, and laps are commonly observed on chill-cast surfaces. With lead used as a representative material, the occurrence of these features over a range of casting speeds from 0.025 to 17 cm/s (0.6 to 400 in./min) has been examined. On the basis of their assumed origin, three types of surface features have been recognized. The first two are associated with the mechanical behavior of the thermally stressed solidifying shell. Fine Type I grooves are the remnants of periodic shell corrugations formed near the meniscus during the earliest stages of solidification, and their spacing decreases with increasing casting speeds. More widely spaced Type II wrinkles are concavities that develop as solidification progresses, and are associated with the temperature perturbations that cause uneven thickening of the shell. Type III surface features occur at slow casting speeds when freezing of the meniscus gives rise to periodic surface lapping.