Showing papers on "Shell (structure) published in 2004"
Book•
01 Jan 2004
TL;DR: In this paper, the authors present a method for analyzing the effect of different kinds of shells on the performance of different types of shells, such as: CURVED BEAMS, PLATES SHALLOW SHELLS, CYLINDRICAL SHELLs, SPHERICAL SHELS, etc.
Abstract: 1. INTRODUCTION 2. SHELL THEORIES 3. METHODS OF ANALYSIS 4. CURVED BEAMS 5. PLATES SHALLOW SHELLS CYLINDRICAL SHELLS 8. CONICAL SHELLS 9. SPHERICAL SHELLS 10. COMPLICATING EFFECTS REFERENCES
485 citations
TL;DR: In this article, the use of the Murakami zig-zag function (MZZF) in the two-dimensional modeling of multilayered plates and shells is discussed.
267 citations
TL;DR: In this paper, the authors found that the mechanism by which the shell affects the electrode properties depends on the coating material and that either the shell acidity or the electron affinity of the shell are the shift controlling parameters, although the former seems more likely.
246 citations
TL;DR: In this paper, a cylindrical shell which has two stable configurations, due to a particular distribution of residual stresses induced by plastic bending, is investigated, and a comprehensive analytical model is developed which predicts the residual stress distribution and bistable configurations of the shell.
236 citations
TL;DR: In this paper, the authors studied inverted core/shell nanocrystals (NCs) in which a core of a wide gap semiconductor (ZnSe) is overcoated with a shell of a semiconductor of a narrower gap (CdSe).
Abstract: We study inverted core/shell nanocrystals (NCs) in which a core of a wide gap semiconductor (ZnSe) is overcoated with a shell of a semiconductor of a narrower gap (CdSe). By monitoring radiative recombination lifetimes for a series of these NCs with a fixed core radius and progressively increasing shell thickness, we observe a continuous transition from Type-I (both electron and hole wave functions are distributed over the entire NC) to Type-II (electron and hole are spatially separated between the shell and the core) and back to Type-I (both electron and hole primarily reside in the shell) localization regimes. These observations are in good agreement with the calculated dependence of the electron−hole overlap integral on shell thickness.
229 citations
TL;DR: In this article, a simple methodology to design isotropic triangular shell finite elements based on the Mixed Interpolation of Tensorial Components (MITC) approach is presented, which performs well-established numerical tests and shows the performance of the new elements.
218 citations
TL;DR: In this paper, the free vibration of an arbitrarily thick orthotropic piezoelectric hollow cylinder with a functionally graded property along the thickness direction and filled with a non-viscous compressible fluid medium is investigated.
183 citations
Patent•
25 Jun 2004
TL;DR: In this paper, the authors describe a process for assisting the function of a heart disposed within a body, and comprising an outer wall, comprising the steps of measuring at least one parameter that is indicative of the heart, applying a compressive force to a portion of the outer wall of the human heart, and applying an expansive force to the portions of the inner wall.
Abstract: A process for assisting the function of a heart disposed within a body, and comprising an outer wall, comprising the steps of measuring at least one parameter that is indicative of the function of the heart, applying a compressive force to a portion of the outer wall of the heart, and applying an expansive force to the portion of the outer wall of the heart. The process is preferably performed with an apparatus comprising a cup-shaped shell having an exterior wall, an interior wall, an apex, and an upper edge; a liner having an outer surface and an inner surface, an upper edge joined to said interior wall of the cup-shaped shell, and a lower edge joined of the interior wall of the cup-shaped shell, thereby forming a cavity between the outer surface thereof and the interior wall of the shell; and a drive fluid cyclically interposed within the cavity, the drive fluid applying a uniform force on a portion of the outer wall of the heart.
165 citations
TL;DR: In this article, an extended stochastic formulation of the triangular composite facet shell element TRIC is presented for the case of combined uncertain material (Young's modulus, Poisson's ratio) and geometric (thickness) properties.
153 citations
TL;DR: In this article, a boundary layer theory of shell buckling, which includes the effects of nonlinear prebuckling deformations, large deflections in the postbuckling range, and initial geometric imperfections of the shell, is extended to the case of functionally graded cylindrical shells of finite length.
144 citations
TL;DR: Variation of the fabrication parameters allowed complete encapsulation by the shell phase, including the efficient formation of a PCPH shell encapsulating a PLG core and surface-eroding poly[(1,6-bis-carboxyphenoxy) hexane] (PCPH).
TL;DR: In this article, a 14 nm diameter Au core surrounded by a 72 nm thick silica shell was irradiated with 30 MeV heavy ions and the shell deforms into an oblate ellipsoid, while the core becomes rod-shaped with the major axis along the beam.
Abstract: Colloidal particles with a 14 nm diameter Au core surrounded by a 72 nm thick silica shell have been irradiated with 30 MeV heavy ions. The shell deforms into an oblate ellipsoid, while the core becomes rod-shaped (aspect ratio up to 9) with the major axis along the beam. Optical extinction measurements show evidence for split plasmon bands, characteristic for anisotropic metal nanoparticles.
TL;DR: In this paper, a finite element formulation for active vibration control of thin plate laminated structures with integrated piezoelectric layers acting as sensors and actuators is presented, based on the Kirchhoff classical laminated theory.
TL;DR: In this paper, the authors developed the general nonlinear theory of elastic shells with an account of phase transitions in the shell material, based on the dynamically and kinematically exact through-the-thickness reduction of three-dimensional description of the phenomenon to the two-dimensional form written on the shell base surface.
Abstract: We develop the general nonlinear theory of elastic shells with an account of phase transitions in the shell material. Our formulation is based on the dynamically and kinematically exact through-the-thickness reduction of three-dimensional description of the phenomenon to the two-dimensional form written on the shell base surface. In this model shell displacements are expressed by work-averaged translations and rotations of the shell cross-sections. All shell relations are then found from the variational principle of the stationary total potential energy. In particular, we derive the new global dynamic continuity condition at the singular surface curve modelling the phase interface. We also discuss particular forms of the local dynamic continuity conditions at coherent and incoherent interface curves. The results are illustrated by an example of a phase transition in an infinite plate with a circular hole.
TL;DR: In this paper, the authors presented a combined experimental-numerical procedure for development and calibration of macroscopic crack propagation criteria in large-scale shell structures, where a mode-I crack can be driven 400 mm through a 20(+) mm thick plate under fully plastic and controlled conditions.
TL;DR: In this article, the impact response of composite laminate and shell structures is proportional to the impactor velocity, and the effects of various parameters, such as shell curvature, clamped or simple supported boundary conditions, are examined through the parametric study.
TL;DR: In this paper, a delamination model for shell elements is presented, which consists of an adhesive penalty contact formulation for initially tying shells together and a cohesive zone model for degrading the adhesive forces.
TL;DR: In this paper, the influence of different induced folding modes is investigated with the help of experiments as well as numerical finite element (FE) calculations and a simplified analytical model by Marsolek's Energieabsorptionsverhalten zylinderschalenformiger Struktureiemente aus Metall und Faserverbundwerkstoff.
TL;DR: In this article, an elastic double-shell model is presented for the buckling and postbuckling of a double-walled carbon nanotube subjected to external hydrostatic pressure.
TL;DR: In this article, the buckling of an elastic cylinder under non-uniform axial compression applied at one boundary is investigated and four imperfection forms are examined: the linear bifurcation mode, the nonlinear buckling mode, several post-buckling deformed shapes for the perfect shell, and a weld depression.
TL;DR: In this paper, a finite element/finite difference (FE/FD) method was used to determine the transient temperature field and associated thermal stresses in functionally graded materials (FGMs) for high temperature applications.
TL;DR: In this paper, the effects of rotation on wave propagation within a tire's treadband were investigated for the purpose of understanding the effect of rotating a tire on the propagation of a wave within the tire.
Patent•
27 Feb 2004
TL;DR: In this article, a support pillow comprises a medial region and two opposing arms that define a generally open well, with the cushion body having an outer periphery and an inner periphery adjacent the well.
Abstract: A support pillow comprises a cushion body having a medial region and two opposing arms that define a generally open well, with the cushion body having an outer periphery and an inner periphery adjacent the well. A shell encompasses the cushion body. A fabric cover is removably disposed over the shell such that the fabric cover generally conforms to the shell. The fabric cover defines an opening to permit the cover to be placed over the shell, and the fabric covering includes at least one fastener to close the opening once the cover has been placed over the shell.
01 Feb 2004
TL;DR: Considering the complicated testing procedure on a fresh sample of scapula, the high correlation coefficients, the low standard errors and percentage errors in the regression slope, strongly suggest that the strains calculated by the FE model can be used as a valid predictor of the actual measured strain.
Abstract: A new modelling approach, using a combination of shell and solid elements, has been adopted to develop a realistic three-dimensional finite element (FE) model of the human scapula. Shell elements were used to represent a part of the compact bone layer (i.e. the outer cortical layer) and the very thin and rather flat part of the scapula—infraspinous fossa and supraspinous fossa respectively. Solid elements were used to model the remaining part of the compact bone and the trabecular bone. The FE model results in proper element shapes without distortion. The geometry, material properties and thickness were taken from quantitative computed tomography (CT) data. A thorough experimental set-up for strain gauge measurement on a fresh bone serves as a reference to assess the accuracy of FE predictions. A fresh cadaveric scapula with 18 strain gauges fixed at various locations and orientations was loaded in a mechanical testing machine and supported at three locations by linkage mechanisms interconnected b...
TL;DR: In this paper, a spherically symmetric traversable wormhole is matched to a unique exterior vacuum solution, with a generic cosmological constant, at a junction interface, and the surface stresses on the thin shell are deduced.
Abstract: We match an interior solution of a spherically symmetric traversable wormhole to a unique exterior vacuum solution, with a generic cosmological constant, at a junction interface, and the surface stresses on the thin shell are deduced. In the spirit of minimizing the usage of exotic matter we determine regions in which the weak and null energy conditions are satisfied on the junction surface. The characteristics and several physical properties of the surface stresses are explored, namely, regions where the sign of the tangential surface pressure is positive and negative (surface tension) are determined. This is done by expressing the tangential surface pressure as a function of several parameters, namely, that of the matching radius, the redshift parameter, the surface energy density and of the generic cosmological constant. An equation governing the behaviour of the radial pressure across the junction surface is also deduced.
TL;DR: In this article, the authors measured the hardness and elastic modulus of the shell of a scallop, a member of the Pectinidae family, and found that the shell exhibits a hardness of about 5 GPa and elastic modulation of about 87 GPa.
Abstract: Micro/nanomechanical characterization of the shell of a scallop, a member of the Pectinidae family, has been carried out Hardness and elastic modulus were measured by nanoindentation using a nanoindenter Micro/nanoscale cracks were generated by microindentation using a microindenter The shell's crossed lamellar structure and indentation cracks were imaged using an optical microscope, an atomic force microscope and a scanning electron microscope It was found from nanoindentation tests that the shell exhibits a hardness of about 5 GPa and elastic modulus of about 87 GPa Nanoindentation resulted in pile-up around the indent In the middle and bottom layers primary cracks propagate along the first-order lamellar boundaries and numerous secondary cracks branch off along the second-order lamellar boundaries The additional energy required for crack propagation results from the secondary cracks along the second-order lamellar boundaries Cracks formed in the top layer of the shell do not show the crack diversion mechanism due to the lack of first-order lamellar organization Fracture mechanisms were discussed in conjunction with architecture, hardness, elastic modulus, and energy-dissipation during cracking
TL;DR: In this article, the authors investigated the ultrastructure of the secondary layer of the calcite shell of the terebratulide brachiopod Megerlia truncata with SEM and electron beam backscattering diffraction.
Abstract: We investigated the ultrastructure of the secondary layer of the calcite shell of the terebratulide brachiopod Megerlia truncata with SEM and electron beam backscattering diffraction. The material of the secondary layer is an inorganic/organic fibre composite. Each individual cell of the outer epithelium secrets a single crystal confined in a protein sheath. The morphological fibre axes of the single crystals are almost parallel to the shell surface. The fibrous growth occurs in arbitrary directions perpendicular to the triad symmetry direction of calcite. Accordingly, the fibres form a cylindrical \"fibre\" texture, with the texture axis perpendicular to the shell surface. The curvature of the fibres is caused by lateral displacements or rearrangements of the secreting cell array during growth. In these events the existing crystal lattice is not distorted - it is the substrate for continued crystal growth from the cell, irrespective of direction.
TL;DR: Observations suggest that the iridescent colors of the mollusk Haliotis Glabra are caused by both diffraction and interference, and the uniform stacking of layers of nacre below the surface of the shell also causes interference effects that contribute to the irIDEScent colors.
Abstract: Pearls and shells of some mollusks are attractive inorganic materials primarily owing to the beauty of their natural lustrous and iridescent surface. The iridescent colors can be explained by diffraction or interference or both, depending on the microstructure of the surface. Strong iridescent colors are very evident on the polished shell of the mollusk Haliotis Glabra, commonly known as abalone. It would be interesting to study how these colors are produced on the surface of the shell. By using a scanning electron microscope (SEM), the surface of the shell is found to have a fine-scale diffraction grating structure, and stacks of thin crystalline nacreous layers or platelets are found below the surface. These observations suggest that the iridescent colors are caused by both diffraction and interference. From measurements done on the diffraction patterns that were obtained using a He-Ne laser illuminating the shell, the groove width of the grating structure was derived. Good agreement was found between the derived groove density by diffraction and that measured directly using the SEM. The crystalline structure of the nacreous layers of the shell is studied using Fourier transform infrared spectroscopy and SEM observations. The infrared absorption peaks of 700, 713, 862 and 1083 cm-1 confirmed that the nacre of the shell is basically aragonite. The strong iridescent colors of the shell are the result of high groove density on the surface which causes diffraction. The uniform stacking of layers of nacre below the surface of the shell also causes interference effects that contribute to the iridescent colors.