Showing papers on "Shell (structure) published in 1992"

Fiber orientation in simple injection moldings. Part II: Experimental results

Abstract: Experimental measurements of fiber orientation are reported for two parts injection molded from nylon 6/6 reinforced with 43 wt% of glass fibers. The parts are a center-gated disk and a film-gated strip. Orientation is measured from polished cross sections and reported as a function of position, both across the thickness and in the flow direction. Both parts have a layered structure, with outer shell layers of flow-aligned fibers surrounding a central core of either random-in-plane (strip) or transversely aligned fibers (disk). The disk also has surface skins with less alignment. The experiments are compared with predictions of the simulation presented in Part I. The simulation predicts the presence, nature, and location of the layers very well. However, it overpredicts the small out-of-plane fiber orientation and places the core-shell transition too close to the midplane. A comparison with selected experimental results suggests that the major source of error is the closure approximation used by the fiber orientation equation. The simulation is exercised for a variety of cases to show the importance of material and process parameters. A polymer matrix with a small power-law index or a large heat of fusion gives a thicker core and is less likely to have a skin. Injection time is an important parameter, but injection temperature and mold temperature have little effect on fiber orientation.

Acetabular cup positioning insert

Abstract: An acetabular cup for use as a prosthetic implant has an insert with a body including a central bore for receiving a positioning rod therein. A key element is formed on the bore and is adapted to align the positioning rod. The insert has a locating element formed on an outer surface of the body and also includes spring elements extending radially outwardly from the body. The acetabular cup has a generally hemispherical shell member coupled to the outer surface of the insert. The shell has an outer surface for engaging the acetabulum and an inner surface having a circumferential groove for receiving the spring elements. The spring elements may be deflected radially inwardly out of engagement with the groove for releasing the insert from the shell. The shell has a plurality of apertures extending from its inner to its outer surface, which apertures are located in an asymmetrical pattern about the shell. The shell includes a recess on its open end for receiving the locating element on the insert to align the insert at a predetermined orientation with respect to the apertures in the shell. The engagement of the insert onto the shell and the engagement of the locating element in the recess aligns the key element on the central bore and, therefore, the positioning rod at a predetermined orientation with respect to the apertures in the shell.

Modeling superheat removal during continuous casting of steel slabs

Abstract: To investigate superheat dissipation in a continuous slab casting machine, mathematical models have been developed to compute fluid flow velocities, temperature distribution within the liquid pool, heat transfer to the inside of the solidifying shell, and its effect on growth of the shell. Three-dimensional (3-D) velocity and heat-transfer predictions compare reasonably with pre-vious experimental measurements and two-dimensional (2-D) calculations. The results indicate that the maximum heat input to the shell occurs near the impingement point on the narrow face and confirm that most of the superheat is dissipated in or just below the mold. Superheat tem-perature and casting speed have the most important and direct influence on heat flux. The effects of other variables, including mold width, nozzle jet angle, and submergence depth, are also investigated. Calculated heat flux profiles are then input to a one-dimensional (1-D) solidifi-cation model to calculate growth of the shell. Shell thickness profiles down the wide and narrow faces are compared with the predictions of conventional heat conduction models and available measurements.

An exact finite rotation shell theory, its mixed variational formulation and its finite element implementation

Abstract: A non-linear shell theory, including transverse shear strains, with exact description of the kinematical fields is developed. The strain measures are derived via the polar decomposition theorem allowing for an explicit use of a three parametric rotation tensor. Thus in-plane rotations, also called drilling degrees of freedom, are included in a natural way. Various alternatives of the theory are derived. For a special version of the theory, with altogether six kinematical fields, different mixed variational principles are given. A hybrid finite element formulation, which does not exhibit locking phenomena, is developed. Numerical examples of shell deformation at finite rotations, with excellent element performance, are presented. Comparison with results reported in the literature demonstrates the features of the theory as well as the proposed finite element formulation.

Advances in one-point quadrature shell elements

Abstract: A one-point quadrature element is developed for shells which overcomes two drawbacks of a similar element developed previously by the senior author and co-workers. The kinematics are improved so that the element is accurate for warped configurations, such as the twisted beam. A nodal projection is added and as result the element passes the quadratic transverse-deflection patch test. The element is applied to a number of test problems which illustrate its effectiveness. One of these is the patch test, and a method for implementing the patch test in an explicit dynamic program is described.

The problem of membrane locking in finite element analysis of cylindrical shells

Abstract: We analyse the problem of membrane locking in (h, p) finite element models of a thin hemicylindrical shell roof loaded by a smoothly varying normal pressure distribution. We show that in the standard finite element method, locking occurs especially at low values ofp and when the finite element grid is not aligned with the axis of the cylinder. A general strategy of avoiding locking by using modified bilinear forms is introduced, and a special implementation of this strategy on aligned rectangular grids is considered.

Axisymmetric wave propagation in fluid‐loaded cylindrical shells. II: Theory versus experiment

Abstract: This paper discusses both theoretical and experimental aspects of axisymmetric wave propagation along fluid‐loaded cylindrical shells (excluding torsional modes). For a steel cylindrical shell with a fixed ratio of inner to outer radius, four different fluid configurations are considered: water inside and outside the steel shell; air inside and outside; water inside and air outside; and air inside and water outside. Calculations of the transient pressure response for the case of an axisymmetric ring source and a point receiver are made as a function of source–receiver separation. Experimentally, a PZT ring source and ring receiver are placed around a steel cylindrical shell with an outer radius of 9.53 mm and an inner radius of 7.94 mm. Waveforms are recorded for multiple source–receiver hydrophone spacings in the frequency band 50–240 kHz. Using a Prony’s method, the complex wave number as a function of frequency for each of the modes in the system is derived from both the theoretical and experimental wa...

A simple class of finite elements for plate and shell problems. II: An element for thin shells, with only translational degrees of freedom

Abstract: This paper is the second of a pair which discuss the development of a class of overlapping hinged bending finite elements, which are suitable for the analysis of thin-shell, plate and beam structures. These elements rely on a simple physically appealing analogy, in which overlapping hinged facets are used to represent bending effects. They are based on quadratic overlapping assumed displacement functions, which results in constant stress/strain representation. Only translational nodal degrees of freedom are necessary, which is a significant advantage over most other currently available beam, plate and shell finite elements which employ translational, rotational and higher-order nodal variables. In paper I the hinged bending element concept has been introduced, and the hinged beam bending (HBB) and hinged plate bending (HPB) elements formulated. In the present paper these concepts are extended to develop a hinged shell bending (HSB) element. The HSB element can be readily combined with the constant strain triangular (CST) plane stress finite element for the modelling of thin-shell structures; and the combined HSB-CST element is tested against a number of 'standard' thin-shell problems. The present paper, like paper I, is conducted entirely in the context of small-displacement elastic behaviour.

Vertical mount connector

Abstract: An electrical connector 1 comprising: a conductive contact 6 connected to a circuit board mounting terminal 17, an insulative body 3 surrounding the contact 6, a conductive shell 2 surrounding the insulative body 3, a base 11 surrounding the shell 2, conductive circuit board mounting posts 13 on the base 11, the shell 2 being insulated from the base 11, and an electrical capacitor comprised of a dielectric element 26 between the shell 2 and the base 11.

Rotation halts cylindrical, relativistic gravitational collapse.

Abstract: It is shown, in a simple analytic example, that an infinitesimal amount of rotation can halt the general relativistic gravitational collapse of a pressure-free cylindrical body. The example is a thin cylindrical shell (a shell with translational symmetry and rotation symmetry), made of counterrotating dust particles. Half of the particles rotate about the symmetry axis in one direction with (conserved) angular momentum per unit rest mass α, and the other half rotate in the opposite direction with the same α. It is shown, using C-energy arguments, that the shell can never collapse to a circumference smaller than C=8παΛ, where Λ is the shell’s nonconserved mass per unit proper length. Equivalently, if R≡‖∂/∂φ∥∂/∂z‖ is the product of the lengths of the rotational and translational Killing vectors at the shell’s location and λ is the shell’s conserved rest mass per unit Killing length z, then the shell can never collapse smaller than R=4αλ. It is also shown that after its centrifugally induced bounce, the shell will oscillate radially and will radiate gravitational waves as it oscillates, the waves will carry away C energy, and this loss of C energy will force the shell to settle down to a static, equilibrium radius.

Recyclable microwavable container with a hinged removable outer shell

Abstract: A microwavable container useful in the microwave heating of items, particularly foodstuffs, comprises readily separable components. An outer shell which will remain relatively cool and, therefore, capable of being handled, is flexibly hinged to an inner shell capable of sustaining high temperatures. The inner shell rotatably folds about the flexible hinge in such a way that it is arranged in a substantially spaced relation to the outer shell and is releasably secured to the outer shell. The outer shell is made of a first microwavable polymeric material. The inner shell is made of a second microwavable polymeric material which is different from the first microwavable polymeric material. A consumer may heat a food product in the inner shell of the present invention without risking contact with that inner shell when the inner shell becomes hot. After use, the components are readily separable for separate recycling processes.

Finite-rotation shell elements for the analysis of finite-rotation shell problems

Abstract: For the analysis of shell structures with finite displacements and rotations displacement-based and mixed finite-rotation shell elements are developed starting from consistent tensorial shell theories. The constraints for the description of the deformed normal vector have been considered at the element level as subsidiary conditions so that finite rotations in arbitrary strongly nonlinear situations can be considered without any difficulty. The efficiency of the finite-rotation elements is demonstrated by numerical examples.

Scattering of an obliquely incident acoustic wave by an infinite hollow cylindrical shell

Abstract: Acoustic scattering from an isotropic elastic hollow cylindrical shell of infinite length excited by an obliquely incident plane acoustic wave is investigated. The form functions of an aluminum cylindrical shell immersed in water have been calculated by the direct summation of the Rayleigh series. Computations are made at angles (with the normal to the cylinder axis) between α=0° and α=35°. The results of the theoretical calculation are in good agreement with the results of experiments. The experimental results have shown in a frequency range of k1a=0 –20 that the resonances are related to three wave families: the circumferential wave (l=2) detected for angles smaller than the ‘‘angle of longitudinal wave in thin rods’’ (αl), the guided wave (p=1) detected for angles smaller than the second critical angle (αT), and the Scholte–Stoneley wave (l=0). The evolution of the resonance frequencies is followed for different angles and one can note experimentally, that at an angle superior to the Rayleigh critical ...

An assumed-stress hybrid 4-node shell element with drilling degrees of freedom

Abstract: An assumed-stress hybrid/mixed 4-node quadrilateral shell element is introduced that alleviates most of the deficiencies associated with such elements. The formulation of the element is based on the assumed-stress hybrid/mixed method using the Hellinger-Reissner variational principle. The membrane part of the element has 12 degrees of freedom including rotational or 'drilling' degrees of freedom at the nodes. The bending part of the element also has 12 degrees of freedom. The bending part of the element uses the Reissner-Mindlin plate theory which takes into account the transverse shear contributions. The element formulation is derived from an 8-node isoparametric element by expressing the midside displacement degrees of freedom in terms of displacement and rotational degrees of freedom at corner nodes. The element passes the patch test, is nearly insensitive to mesh distortion, does not 'lock', possesses the desirable invariance properties, has no hidden spurious modes, and for the majority of test cases used in this paper produces more accurate results than the other elements employed herein for comparison.

Layer-wise shell theory for postbuckling of laminated circular cylindrical shells

Abstract: The layer-wise shell theory of Reddy is used to study the postbuckling response of circular cylindrical shells. The Rayleigh-Ritz method is used to solve the equations by assuming a double Fourier expansion of the displacements with trigonometric coordinate functions. Numerical results for postbuckling response of axially compressed multilayer cylinders with simply supported edge conditions are presented for different values of shell imperfections.

Compartmented fuel tank with fuel absorbent material

Abstract: A fuel tank is disclosed having an inner shell, an outer shell enveloping the inner shell, and a fuel absorbent material filling the space between the inner shell and the outer shell. The fuel absorbent material is preferably a molded granular material. The inner shell is an assembly of injection molded plastic halves joined together along peripheral flanges, each inner shell half being integrally formed with internal walls. The internal walls are formed with undercut openings. The outer shell is an assembly of outer shell halves joined together along peripheral flanges. Also disclosed is an injection molding apparatus adapted to manufacture the inner shell halves with undercut openings in the internal walls.

Air filter for medical ventilation equipment and the like

Abstract: An inexpensive, bi-directional, low flow resistance air filter for medical ventilation equipment and the like includes a disposable shell possessing a cylindrical conduit terminating in an exponentially curved radially outwardly flaring surface. The exponentially curved construction minimizes dead space and hence also flow resistance Radially and axially spaced stepped annular surfaces connected by short axially extending cylindrical sidewall portions at a distal end of the shell function as coupling and sealing surfaces. A ring of adhesive applied adjacent a peripheral edge of an electret filter disk mounts the filter disk internally within the shell. An elastic retaining band detachably secures an equipment connection adapter to the shell, such that a technician may easily and quickly replace the shell and filter. The equipment connection adapter possesses clamping ring and coupling rim surfaces dimensioned in close conformance with the coupling and sealing surfaces of the shell to ensure a fluid tight connection. The filter assembly allows rapid replacement of contaminated filter components to protect patients from diseases caused by bacterial and viral microorganisms, while minimizing medical waste.

Multiple stage countercurrent hollow fiber membrane module

Abstract: A hollow fiber separation module is provided having a single, elongated pressurizable shell and containing multiple separation stages by multiple sections of hollow fiber bundles contained within the shell, with the ends of each bundle section potted within a single tubesheet at each end of the elongated shell. The fibers within each section are aligned so that the permeate within the fiber bores passes along paths traveling generally from one tubesheet to the other and one or more impermeable barriers are provided within the shell to isolate each section and control the passage of feed gas along the shell side of each fiber bundle section in a flow path countercurrent to the passage of permeate in the bores of the fibers.

Separable ventilated athletic jacket

Abstract: Athlete's arm jacket which includes a first shell portion for covering one side of the upper torso of a person wearing the jacket. A sleeve is secured to the shell portion for covering one arm. A mesh covers the opposite side of the upper torso, and a second shell portion is detachably secured to the first shell portion. Another sleeve is attached to the second shell portion. The jacket may be worn and used as a traditional jacket, or one shell portion may be detached so that only one arm, shoulder and one side of the upper torso of the body are covered.

Shielding a surface mount electrical connector

Abstract: A folded sheet metal shielding shell (4) for a surface mounted electrical connector (6) has a side wall (14) with parts (16, 18) defining a seam (20) extending longitudinally of the shielding shell (4) so that electro-magnetic induction radiated by the mating portions (120) of the terminals (116 118) of the connector (6) is not directed towards the circuit board PCB upon which the shell (4) and the connector (6) are mounted, so as to interfere with circuitry on the board PCB. The seam (2) may be held closed by means of a counting flange (208), for securing the shell (4') to a counting panel (P).

Free vibration of axisymmetric and beam-like cylindrical shells, partially filled with liquid

Abstract: A theory is presented for the determination of the free vibration characteristics of anisotropic thin cylindrical shells, partially or completely filled with liquid, for two circumferential wave numbers, n = 0, axisymmetric and n = 1, beam-like. The method used was a combination of finite element analysis and classical shell theory. The shell was subdivided into cylindrical finite elements and the displacement functions were obtained using the shell equations. Expressions for the mass and stiffness matrices for a finite element and for the whole structure were obtained. A finite element was developed for the liquid in cases of potential flow. The natural frequencies of the shell, both empty and partially filled, were obtained and compared with existing experiments and other theories.

Finite Elements for Solids, Fluids, and Optimization

Abstract: Part 1 Introduction to finite elements: skeletal elements basic relationships for solid continua energy principles and applications Lagrange multipliers, penalty factors and basis transformation interpolation functions and numerical integration. Part 2 Applications to the statics of solids: plane stress and plane strain isoparametric mapping and its applications thin plate bending elements thick plate elements flat elements for shell analysis curved shell elements. Part 3 Nonlinear and time dependent problems and FEM programming: nonlinear materials and large displacements eigenvalue analysis of vibration and stability time stepping analysis of vibration and creep finite element programming. Part 4 Finite elements in fluid flow and other field problems: basic differential equations in continua variational and weighted residual methods pseudo-harmonic field problems potential flow, viscous flow and compressible flow fluid flow examples and programs. Part 5 Further applications of the finite element method: boundary solution techniques optimization techniques and applications generalization of constraint techniques and optimization programs.

Large-amplitude plate vibration in an elevated thermal environment

Abstract: At elevated temperatures the dynamics of vibrating plate (or shell) must include the three thermal effects: (i) the global expansion by uniform plate temperature, (ii) the local expansion by temperature variation over the plate, and (iii) the thermal moment induced by temperature gradient across the plate thickness. For the single-mode prototype model of Galerkin representation, (i) and (ii) give rise to the combined stiffness that is responsible for thermal buckling, whereas (iii) contributes to the combined forcing of acoustic and thermal excitations. For the high-temperature sonic fatigue test facility at the Wright Lab, the present study is devoted to the mean square estimates on transverse displacement and normal stress/strain by the equivalent linearization technique.