Showing papers on "Shell (structure) published in 1998"

Reinforced structural members

Abstract: A channel-shaped section has a thin, local reinforcement shell separated from the channel-shaped section by a layer of structural foam. At the reinforced section an arch geometry is utilized which extends in a direction opposite that of the force to which the member is subjected. The arch may be present as the channel-shaped member, the reinforcement shell or both the channel-shaped member and the shell. A portion of the shell contacts the channel-shaped member and is attached thereto by welding or other means of attachment.

Hierarchical Order in Hollow Spheres of Mesoporous Silicates

Abstract: Mesoporous MCM-41 silica hierarchical structures consisting of a high yield (∼98%) of uniform-sized hollow spheres of diameter 5.0 ± 1.0 μm have been obtained. The nanochannels on the shell are in latitude direction and the inside of the micron spheres has intricate pillar structures producing structures of various topological genus ranks.

The inverse approach with simple triangular shell elements for large strain predictions of sheet metal forming parts

Abstract: An efficient algorithm to estimate the large elasto‐plastic strains encountered in thin sheet metal forming parts has been continuously developed by the authors since 1987. The algorithm is based on a finite element discretization of the known final shape. In this paper a new simple triangular shell element with constant membrane and bending strains is presented using discrete Kirchhoff constraints. The expressions of the internal force vector and logarithmic strains through the thickness are derived. Two applications are considered to discuss the validity and efficiency of the numerical procedure.

Spectroscopy of radioactive beams from single-nucleon knockout reactions: Application to the sd shell nuclei Al-25 and P-26,P-27,P-28

Abstract: Measurements of deexcitation $\ensuremath{\gamma}$ rays in coincidence with the momentum distribution of the projectile residues produced in reactions of the type ${}^{9}\mathrm{Be}{(}^{28}\mathrm{P}{,}^{27}\mathrm{Si}+\ensuremath{\gamma})X$ at energies around 65 MeV/u are used to study single-nucleon stripping to individual states. The cross sections are compared with calculations based on an eikonal model description of the reaction and the shell model. The measurements indicate that the halo character of the ground state and other detailed spectroscopic information can be derived using knockout reactions in inverse kinematics.

Heat-insulating container

Abstract: A heat-insulating container comprises a paper cup body having an inner surface, an upper open end, a shell member and a bottom, the inner surface being coated with polyolefine resin, the upper open end having an outward curled portion and the shell member having a side wall on which at least one rib is formed; and a tubular member being formed of paper and having an inverse truncated conical shape, the tubular member having at a lower end thereof an inward curled portion. The tubular member is combined with an outer periphery of the paper cup body so as to come into contact with the paper cup body in contact portions provided on the at least one rib of the paper cup body and on an outer periphery of an lower end of the side wall of the shell member. According to such a structure, it is possible to provide the heat-insulating container, which has a stable heat-insulating property, a high grade design, a high degree of freedom in indication by printing on the outer surface of the container, and a lower production cost.

Spin, charge, and bonding in transition metal mono-silicides

Abstract: We review some of the relevant physical properties of the transition metal mono-silicides with the FeSi structure (CrSi, MnSi, FeSi, CoSi, NiSi, etc.) and explore the relation between their structural characteristics and the electronic properties. We confirm the suggestion originally made by Pauling that the FeSi structure supports two quasi-atomic d-states at the transition metal atom. This shell contains from 0 to 4 electrons in the sequence CrSi to NiSi. In FeSi the two quasi-atomic d-electrons are responsible for the high temperature S = 1 state, which is compensated for T = 0 by two itinerant electrons associated with the FeSi resonance bonds.

Locking mechanism for acetabular cup

Abstract: An implantable orthopedic prosthesis is provided that includes a shell (10) having a substantially concave inner surface (16) defining a cavity (22) and a substantially annular groove (79) formed therein. The prosthesis further includes a polymeric insert (60) that is positionable within the cavity (22) of the shell (10), and that has a substantially convex outer surface (62) and a circumferential protrusion (78) projecting therefrom. The protrusion (78) has a substantially trapezoidal cross section wherein at least one of the sides of the trapezoid is substantially parallel to the axis of symmetry of the insert (60). The cross section of the protrusion (78) is substantially congruent to the cross section of the groove (79) of the shell (10), and the inner surface (16) of the shell (10) is substantially congruent with a corresponding portion of the outer surface (62) of the insert (60) when the insert (60) is properly positioned within the cavity (22) of the shell (10).

Degenerated Whitney prism elements-general nodal and edge shell elements for field computation in thin structures

Abstract: Nodal and edge shell elements are derived from a degeneration of Whitney prism elements. They can be easily applied to a variational formulation to solve thin structure problems. It is just needed to replace the volume integral by surface integral and the field discontinuity across the thin structure is correctly taken into account. A thin shell eddy current problem is solved using the present elements and dual formulations.

Large viscoplastic deformations of shells. Theory and finite element formulation

Abstract: The paper is concerned with large viscoplastic deformations of shells when the constitutive model is based on the concept of unified evolution equations. Specifically the model due to Bodner and Partom is modified so as to fit in the frame of multiplicative viscoplasticity. Although the decomposition of the deformation gradient in elastic and inelastic parts is employed, no use is made of the concept of the intermediate configuration. A logarithmic elastic strain measure is used. An algorithm for the evaluation of the exponential map for nonsymmetric arguments as well as a closed form of the tangent operator are given. On the side of the shell theory itself, the shell model is chosen so as to allow for the application of a three-dimensional constitutive law. The shell theory, accordingly, allows for thickness change and is characterized by seven parameters. The constitutive law is evaluated pointwise over the shell thickness to allow for general cyclic loading. An enhanced strain finite element method is given and various examples of large shell deformations including loading-unloading cycles are presented.

Supersonic acoustic intensity on planar sources

Abstract: The concept of supersonic acoustic intensity was developed in 1995 out of a need to locate the sources of radiation on an internally excited, submerged cylindrical shell. Supersonic intensity is obtained through signal processing of near-field holographic data to remove the subsonic part of the helical or plane wave spectrum, leaving only the radiating components. This eliminates the out-of-plane circulation of the acoustic intensity vector which results from evanescent waves. The resulting supersonic intensity on the surface is generally only positive, representing outgoing power flow from the surface. Since negative intensity regions of a vibrator are removed, sources of radiation are readily located on the surface of the vibrator. Since the earlier work concentrated on a cylindrical geometry, the theory is presented here for a planar geometry. In many ways the theory for the planar case is simpler and more straightforward. Numerical examples are given for simply supported, baffled plates. It is shown how the supersonic intensity reconstructions, and resulting location of radiating source regions are consistent with the popular theories of corner and edge mode radiation from plates.

On non-linear dynamics of shells: implementation of energy-momentum conserving algorithm for a finite rotation shell model

Abstract: Continuum and numerical formulations for non-linear dynamics of thin shells are presented in this work. An elastodynamic shell model is developed from the three-dimensional continuum by employing standard assumptions of the first-order shear-deformation theories. Motion of the shell-directior is described by a singularity-free formulation based on the rotation vector. Temporal discretization is performed by an implicit, one-step, second-order accurate, time-integration scheme. In this work, an energy and momentum conserving algorithm, which exactly preserves the fundamental constants of the shell motion and guaranties unconditional algorithmic stability, is used. It may be regarded as a modification of the standard mid-point rule. Spatial discretization is based on the four-noded isoparametric element. Particular attention is devoted to the consistent linearization of the weak form of the initial boundary value problem discretized in time and space, in order to achieve a quadratic rate of asymptotic convergence typical for the Newton-Raphson based solution procedures. An unconditionally stable time finite element formulation suitable for the long-term dynamic computations of flexible shell-like structures, which may be undergoing large displacements, large rotations and large motions is therefore obtained. A set of numerical examples is presented to illustrate the present approach and the performance of the isoparametric four-noded shell finite element in conjunction with the implicit energy and momentum conserving time-integration algorithm.

Permanent magnet motor

Abstract: The utility model relates to an electric device, particularly a high-frequency coupling brushless permanent magnet motor. The utility model is characterized in that an iron core is flat and annular; a coil is H-shaped circular ring; the iron core is embedded in a concave groove arranged on one side of coil which is H-shaped, and is fixed on a lower shell; a fan-shaped magnet steel magnetizes towards axial direction and is arranged on the lower surface of a rotor in a loop. The utility model has the advantages of compact structure of the complete machine, high work efficiency, etc.

A nine-node assumed strain finite element for large-deformation analysis of laminated shells

Abstract: An application of the element-based Lagrangian formulation is described for large-deformation analysis of both single-layered and laminated shells. Natural co-ordinate-based stresses, strains and constitutive equations are used throughout the formulation of the present shell element which offers significant implementation advantages compared with the traditional Lagrangian formulation. In order to avoid locking phenomena, an assumed strain method has been employed with judicious selection of the sampling points. Three strictly successive finite rotations are used to represent the current orientation of the shell normal. The equivalent natural constitutive equation is derived using an explicit transformation scheme to consider the multi-layer effect of laminated structures. The arc-length control method is used to trace complex load-displacement paths. Several numerical analyses are presented and discussed in order to investigate the capabilities of the present shell element. © 1998 John Wiley & Sons, Ltd.