Shell (structure)

About: Shell (structure) is a research topic. Over the lifetime, 76960 publications have been published within this topic receiving 464975 citations.

Subdivision surfaces: a new paradigm for thin-shell finite-element analysis

Abstract: We develop a new paradigm for thin-shell finite-element analysis based on the use of subdivision surfaces for (i) describing the geometry of the shell in its undeformed configuration, and (ii) generating smooth interpolated displacement fields possessing bounded energy within the strict framework of the Kirchhoff–Love theory of thin shells. The particular subdivision strategy adopted here is Loop's scheme, with extensions such as required to account for creases and displacement boundary conditions. The displacement fields obtained by subdivision are H2 and, consequently, have a finite Kirchhoff–Love energy. The resulting finite elements contain three nodes and element integrals are computed by a one-point quadrature. The displacement field of the shell is interpolated from nodal displacements only. In particular, no nodal rotations are used in the interpolation. The interpolation scheme induced by subdivision is non-local, i.e. the displacement field over one element depend on the nodal displacements of the element nodes and all nodes of immediately neighbouring elements. However, the use of subdivision surfaces ensures that all the local displacement fields thus constructed combine conformingly to define one single limit surface. Numerical tests, including the Belytschko et al. [10] obstacle course of benchmark problems, demonstrate the high accuracy and optimal convergence of the method.

Method of making a composite article including a body having a decorative metal plate attached thereto

Abstract: A method of manufacturing a composite article including a hollow body having a decorative metal plate attached thereto. The method includes the forming of a decorative metal plate and the attachment of the plate to a hollow body. The method can be best described by its application to the manufacture of a push button which involves the following: Forming a rectangular sheet of aluminum which sheet has at least one decorative brushed surface. Machining the brushed aluminum surface of the aluminum sheet in an annular pattern around the perimeter of the sheet to remove a uniform thickness of the aluminum thereby leaving a central rectangular island of brushed aluminum. The central rectangular island thus formed is surrounded on all sides by the machined surface which functions as an apron around the island. All of the machined surface apron on both long sides of the rectangular island is removed leaving tabs of apron extending from the opposite short ends of the rectangular island. The tabs are bent away from the brushed aluminum surface so that they extend at generally right angles to the brushed aluminum surface of the island. The metal plate thus formed is attached to the plastic shell by inserting the tabs into passages formed in one end of the plastic shell while positioning the island against the plastic shell. The tabs are crimped to lock the aluminum plate to the plastic shell to complete the push button.

Structural basis for the fracture toughness of the shell of the conch Strombus gigas

Abstract: Natural composite materials are renowned for their mechanical strength and toughness: despite being highly mineralized, with the organic component constituting not more than a few per cent of the composite material, the fracture toughness exceeds that of single crystals of the pure mineral by two to three orders of magnitude The judicious placement of the organic matrix, relative to the mineral phase, and the hierarchical structural architecture extending over several distinct length scales both play crucial roles in the mechanical response of natural composites to external loads Here we use transmission electron microscopy studies and beam bending experiments to show that the resistance of the shell of the conch Strombus gigas to catastrophic fracture can be understood quantitatively by invoking two energy-dissipating mechanisms: multiple microcracking in the outer layers at low mechanical loads, and crack bridging in the shell's tougher middle layers at higher loads Both mechanisms are intimately associated with the so-called crossed lamellar microarchitecture of the shell, which provides for 'channel' cracking in the outer layers and uncracked structural features that bridge crack surfaces, thereby significantly increasing the work of fracture, and hence the toughness, of the material Despite a high mineral content of about 99% (by volume) of aragonite, the shell of Strombus gigas can thus be considered a 'ceramic plywood' and can guide the biomimetic design of tough, lightweight structures

Uniform Shell Designs

Abstract: Designs are generated which have an equally spaced distribution of points lying on concentric spherical shells. They have uniform space‐filling properties and are tabulated up to ten factors. The designs are shown to be more uniform than familiar experimental designs on the basis of two measures of uniformity. Their use is illustrated by an example with four factors.