Showing papers on "Shell (structure) published in 1998"
250 citations
TL;DR: In this paper, the authors present fundamental considerations regarding the finite element analysis of shell structures and propose appropriate shell analysis test cases for numerical evaluations, which are applicable to both categories of shell behaviour and the rate of convergence in either case should be optimal.
222 citations
Patent•
21 Jul 1998TL;DR: In this article, an arch geometry is utilized which extends in a direction opposite that of the force to which the member is subjected, and a portion of the shell contacts the channel-shaped member and is attached to it by welding or other means of attachment.
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.
156 citations
TL;DR: In this paper, the nonlinear free and forced vibrations of a simply supported, circular cylindrical shell in contact with an incompressible and inviscid, quiescent and dense fluid are investigated.
129 citations
TL;DR: In this article, the authors present new aspects of large-strain isotropic elastoplastic analysis of shells and present a stress update algorithm for the plasticity model mentioned above which includes a general return mapping in the eigenvalue space.
127 citations
TL;DR: In this article, the dynamics of a tank partially filled with a liquid having a free surface is investigated, and the effect of free surface waves is taken into account, so that both bulging and sloshing modes are studied.
103 citations
TL;DR: In this article, a new simple triangular shell element with constant membrane and bending strains is presented using discrete Kirchhoff constraints, and the expressions of the internal force vector and logarithmic strains through the thickness are derived.
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.
103 citations
TL;DR: In this article, the influence of boundary conditions for a thin laminated rotating cylindrical shell is analyzed using Love-type shell theory and solved using Galerkin's method.
82 citations
TL;DR: In this article, a finite element formulation of eccentric space curved beams with arbitrary cross-sections is derived, based on a Timoshenko beam kinematic, the strain measures are derived by exploitation of the Green-Lagrangean strain tensor.
75 citations
TL;DR: In this article, the authors consider the numerical approximation of boundary layer phenomena occurring in many singularly perturbed problems in mechanics, such as plate and shell problems, and present guidelines for the effective resolution of such layers in the context of existing, commercial p and hp finite element (FE) version codes.
66 citations
TL;DR: In this paper, an exact solution of free harmonic wave propagation in a composite laminated cylindrical shell is presented within the framework of the theory of three-dimensional cylindrically anisotropic elasticity.
TL;DR: In this paper, the analytical solutions for the free vibration of the rotating composite cylindrical shells with axial stiffeners (stringers) and circumferential stiffener (rings), that is, orthogonal stiffeners, are presented using the energy method.
TL;DR: The results of this study demonstrate that backside nonconformity and locking restraints substantially influence backside relative motion as well as load transfer at the liner/shell interface.
TL;DR: In this article, a postbuckling analysis for a stiffened laminated cylindrical shell of finite length subjected to combined loading of external pressure and a uniform temperature rise is presented.
TL;DR: In this paper, the dynamics of cylindrical shells parametrically excited by axial forcing are considered and the governing system of two coupled non-linear partial differential equations is discretized by using Lagrange equations.
TL;DR: In this article, a general analysis of the vibration characteristics of thin, open, conical isotropic panels using theh-pversion of the finite element method in conjunction with Love's thin shell equations is presented.
Patent•
27 Oct 1998
TL;DR: In this article, 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.
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).
TL;DR: Nodal and edge shell elements are derived from a degeneration of Whitney prism elements and they can be easily applied to a variational formulation to solve thin structure problems as mentioned in this paper, which is just needed to replace the volume integral by surface integral and the field discontinuity across the thin structure is correctly taken into account.
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.
TL;DR: In this article, the optimal bead orientation problem of 3D shell/plate structures is investigated for both static and dynamic cases using a bending equivalent orthotropic shell design cell model, and it is solved by a new energy based method.
TL;DR: In this article, a hybrid of finite element and classical thin shell theories was used to predict the influence of geometric nonlinearities on the natural frequencies of an empty laminated orthotropic cylindrical shell.
TL;DR: In this paper, the authors consider large viscoplastic deformations of shells when the constitutive model is based on the concept of unified evolution equations and present an algorithm for the evaluation of the exponential map for nonsymmetric arguments as well as a closed form of the tangent operator.
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.
TL;DR: In this article, a study of the postbuckling behavior of geometrically imperfect anisotropic sandwich doubly-curved and flat panels subjected to a system of compressive edge loads and a lateral pressure is presented.
TL;DR: In this article, an elastodynamic shell model is developed from the three-dimensional continuum by employing standard assumptions of the first-order shear-deformation theories, which exactly preserves the fundamental constants of the shell motion and guaranties unconditional algorithmic stability.
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.
TL;DR: In this article, the supersonic acoustic 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.
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.
TL;DR: In this article, an element-based Lagrangian formulation for large deformation analysis of both single-layered and laminated shells is described, where natural co-ordinate-based stresses, strains and constitutive equations are used throughout the formulation of the present shell element.
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.
Patent•
23 Sep 1998
TL;DR: In this article, the authors describe a candle holder with a translucent outer shell which includes a bottom outer shell and a top outer shell portion and includes a translucent inner shell, and the inner shell is nested inside the outer shell by a substantially constant separation distance.
Abstract: A candle holder apparatus includes a translucent outer shell which includes a bottom outer shell portion and a top outer shell portion and includes a translucent inner shell which includes a bottom inner shell portion and a top inner shell portion. The inner shell defines a candle-reception chamber. A bridge is connected between the outer shell and the inner shell and provides a hollow wall space between the outer shell and the inner shell. The top outer shell portion, the top inner shell portion, and the bridge define an access opening to the candle-reception chamber. A quantity of translucent marbles are located in the hollow wall space. The inner shell is nested inside the outer shell. The outer shell is spaced from the inner shell by a substantially constant separation distance. The outer shell can be made from heat resistant tempered glass. With one class of embodiments of the invention, the bottom outer shell portion includes a flat portion for resting on a flat support surface, and the bottom inner shell portion includes a flat portion for receiving a flat bottom of a candle. With another class of embodiments, a bottom outer shell portion includes an externally threaded access neck to the hollow wall space, and the base member includes an internally threaded reception portion for receiving the hollow wall space access neck.
TL;DR: In this paper, a semi-analytic discrete-layer model is presented for the three-dimensional free vibration analysis of laminated cylindrical shells with distributed piezoelectric layers, which combines finite element approximations through the shell thickness with Fourier and/or power series in the axial and circumferential directions.
Abstract: A semi-analytic discrete-layer model is presented for the three-dimensional free vibration analysis of laminated cylindrical shells with distributed piezoelectric layers. The discrete-layer theory combines finite-element approximations through the shell thickness with Fourier and/or power series in the axial and circumferential directions. This approach can be applied to cylindrical shells consisting of single or multiple layers. Frequencies for the general vibration of solid elastic cylinders show excellent agreement with those in the literature. Results are also presented for the general vibration of laminated piezoelectric cylindrical shells.
TL;DR: In this article, a 4-noded, 48-d.o.f. doubly curved quadrilateral shell finite element based on Kirchhoff-love shell theory is used in the nonlinear finite element analysis to predict the damage of laminated composite cylindrical/spherical shell panels subjected to low-velocity impact.
TL;DR: In this paper, the authors identify the limiting displacement field of a thin shell when its thickness approaches zero as the solution of a two-dimensional nonlinear membrane shell model and show how to update the assumptions on the applied forces acting on the shell to derive a limiting model by an asymptotic analysis.
Abstract: This paper is the sequel of Part I, in which the limiting displacement field of a thin shell when its thickness approaches zero is identified as the solution of a two‐dimensional nonlinear membrane shell model. When the geometry of the middle surface of the shell and the boundary conditions allow non‐zero “inextensional displacements”, the previous membrane limit model is not relevant. In this case, we show how to “update” the assumptions on the applied forces acting on the shell so that a limiting model can be derived by an asymptotic analysis. Furthermore, we identify this limit as the two‐dimensional nonlinear flexural shell model.
TL;DR: In this paper, the linear elastic buckling of circular cylindrical shells by the new Differential Quadrature Method (DQM) has been conducted, where the Fluegge shell stability equations serve as the basis of the analysis.