Showing papers on "Shell (structure) published in 1977"

On the correlation of indentation experiments

Abstract: The relationship between indentation pressure produced by cones, pyramids and spheres, and the mechanical properties of elastic-plastic materials is considered, based on previous work which uses the expansion of a cavity in an elastic-plastic material. According to the earlier model, there are three zones: a hydrostatic 'core' of which the indenter is embedded; a hemispherical shell, where plastic flow is taking place; and beyond this the elastic hinterland. An improved correlation with experimental results is obtained if it is assumed that the hemispherical core is a region in which the stresses are changing from purely hydrostatic to values which satisfy the Von Mises yield criterion. A further improvement results if a correction is made for the lack of geometric similarity of the strain field in indentations by spheres.

Nonlinear dynamics of boussinesq convection in a deep rotating spherical shell-i

Abstract: Convection in a rotating spherical shell has wide application for understanding the dynamics of the atmospheres and interiors of many celestial bodies. In this paper we review linear results for convection in a shell of finite depth at substantial but not asymptotically large Taylor numbers, present nonlinear multimode calculations for similar conditions, and discuss the model and results in the context of the problem of solar convection and differential rotation. Detailed nonlinear calculations are presented for Taylor number T = 105, Prandtl number P = 1, and Rayleigh number R between 1 |MX 104 and 4 |MX 104 (which is between about 4 and 16 times critical) for a shell of depth 20% of the outer radius. Sixteen longitudinal wave numbers are usually included (all even wave numbers m between 0 and 30) the amplitudes of which are computed on a staggered grid in the meridian plane. The kinetic energy spectrum shows a peak in the wave number range m = 12–18 at R = 104, which straddles the critical wav...

Mode interaction in axially stiffened cylindrical shells

Abstract: Postbuckling behavior and imperfection sensitivity associated with mode interaction in axially stiffened cylindrical shells under axial compression are studied. The two modes considered are an overall mode with wavelengths that are long compared to stiffener spacing and a short-wavelength panel mode involving buckling between the stiffeners. A restricted optimization study is made where the number of stringers is treated as a design parameter, and the range of designs considered includes the optimum design for the perfect shell, where the two modes are simultaneous. The influence of a given level of imperfections on the optimum is explored. A general method for analyzing initial postbuckling behavior is proposed for structures with simultaneous or nearly simultaneous modes. Asymptotic expansions of all fields in the amplitudes of the competing modes provide a set of uniformly valid results.

Static equilibrium configurations of a model red blood cell.

Abstract: The membrane of the red blood cell is modeled as a fluid shell which resists bending and changes in area. The differential equations governing the mechanical equilibrium of such a membrane are derived and axisymmetric solutions are obtained numerically.

Some "laws" of gastropod shell form

Abstract: Five generalizations derived from the shell form of prosobranch gastropods are developed. (1) A univalve of more than one volution whose aperture lies in a plane that passes through the axis of coiling does not live with the aperture parallel to the substrate. (2) A univalve of more than one volution whose aperture lies in a plane that is tangential to the body whorl does live with the plane of the aperture parallel to the substrate. (3) Gastropods with tangential apertures, when extended, support the shell so that the center of mass of the shell and its contents is over the midline of the cephalopedal mass; this balancing of the shell may be accomplished either by regulatory detorsion, by inclination or by a combination thereof, to keep the center of gravity of the shell as low as possible. (4) Angulations or re-entrants in the gastropod aperture are usually indicative of inhalent or exhalent areas; inhalent areas are directed as far anteriorly as possible. (5) Gastropods having elongated apertures possess only a single gill and develop a water current through the mantle cavity from anterior to posterior along the long axis of the aperture; this axis is subparallel to the anterior-posterior axis of the foot.These generalizations are then used as the basis for some deductive interpretations of behavioral modes of Paleozoic Gastropoda.

Composite module with reinforced shell

Abstract: A composite module having a rigid foam core encapsulated in a shell of reinforced cementitious material. The shell is reinforced with at least two types of material, the first being a fiber reinforcing material distributed in an interconnected random matrix substantially throughout the shell and the second being a scrim reinforcing material adjacent at least one surface of the shell and/or the rigid foam core.

Shoe, particularly for general sporting activities and training

Abstract: A shoe with a sole and an upper portion for general sporting activities and training, comprising a shell made in one piece from wear-resistant material, such as plastics, rubber and the like, and incorporating the sole and the upper portions of the shoe integral therewith. Inside the shell there is provided a liner having the form of a folded elongated strip internally overlying at least the sole portion, the heel and the instep portion of the shell and being bent at the toe portion and the heel portion to maintain continuity thereof and protect at least the arch, the toes, the plantar and heel portions of the wearer's foot.

A new kind of 3-body problem

Abstract: A new kind of restricted 3-body problem is considered. One body,m1, is a rigid spherical shell filled with an homogeneous incompressible fluid of density ρ1. The second one,m2, is a mass point outside the shell andm3 a small solid sphere of density ρ3 supposed movinginside the shell and subjected to the attraction ofm2 and the buoyancy force due to the fluid ρ1. There exists a solution withm3 at the center of the shell whilem2 describes a Keplerian orbit around it. The linear stability of this configuration is studied assuming the mass ofm3 to beinfinitesimal. Explicitly two cases are considered. In the first case, the orbit ofm2 aroundm1 is circular. In the second case, this orbit is elliptic but the shell is empty (i.e. no fluid inside it) or the densities ρ1 and ρ3 are equal. In each case, the domain of stability is investigated for the whole range of the parameters characterizing the problem.

Imperfection Surveys on a 10-ft-Diameter Shell Structure

Abstract: The results of an extensive imperfection survey on a 10-ft-diameter integrally stiffened cylindrical shell are presented. The shape of the measured initial imperfections is clearly influenced by details of the shell construction. The modal components of the measured imperfection surface as a function of the circumferential and of the axial wave numbers are calculated. The discrete axial power spectral density functions and the corresponding root-mean-square values of the imperfections are also determined for given circumferential wave numbers. Using the Fourier coefficients of the measured initial imperfections, buckling loads are calculated by solving the nonlinear Donnell-type imperfect shell equations iteratively. The calculated lowest buckling load compares favorably with the values usually recommended for similar shell structures.

Boot with hinged upper

Abstract: A motorcycle boot includes a lower vamp shell having a front tongue and rear tapering flaps which extend into an upper shell assembly formed by a hinged front door and a rear cuff The door, of impact resistant plastic to protect the wearer's shin, interleaves with the cuff and is closed by overlying flexible straps A closure system includes wire bales, longitudinally adjustable within holes spaced along the straps, and received with toothed latched receivers The side legs of each wire bale snap-fits under locking flanges when the bale is closed over center A connector hinge assembly includes a slotted plate, attached to the vamp shell, through which extends a freely movable pivot pin journalled in the upper shell to allow forward and rearward motion, rockable sideways motion, and lateral twisting of the shells A replaceable sole insert, formed by a resilient pad molded to a carrier plate, is mechanically locked within a base recess on the bottom of the shell An inner liner extends through the upper shell and is sealed to the lower vamp A replaceable bootie extends into the vamp shell and is fastened to the inner liner

Hand operable scoop for the collection and disposal of animal excrement

Abstract: A container is formed from a pair of concave shell halves with each shell half having a small upper portion and a lower portion which is larger than the upper portion. The shell halves are connected by an integral hinge at their respective upper portions. The smaller upper portions are sized to be easily received in and encompassed by the fingers of a user. The lower portions are provided with straight edges which are disposed remote from the integral hinge. The shell halves are constructed so that they can be manipulated from their normally biased open, i.e., spread apart configuration to a closed configuration about animal excrement. As the shell halves are so manipulated the straight edges scrape the animal excrement into the container. In one embodiment when the shell halves are in their closed configuration the straight edges are in telescoping relationship and a locking structure is provided along at least the straight edges to lock the shell halves in their closed relationship thereby effectively sealing the container. In an alternative embodiment, the straight edges, when the shell halves are in the closed configuration, abut each other and a locking structure disposed on the edges of the shell halves locks the shell halves in their closed relationship.

Acoustic reflection from layered elastic absorptive cylinders

Abstract: The reflection of plane waves by a layered cylindrical shell in water is investigated theoretically. Either or both of the two layers of elastic material may be absorptive. The solution as a function of frequency is examined for several combinations of inner and outer layers.

Rotating trickling filter

Abstract: There is disclosed a rotating trickling filter formed from an elongated, hollow, circular cylindrical shell in which fixed film contactor media is mounted. Wastewater is introduced through an inlet at one end of the shell and exits through an outlet at the opposite end. The volume of wastewater within the shell is maintained as a small fraction of the total volume within the shell and collects as a shallow pool of wastewater at the bottom of the shell. Longitudinal channels sweep through the pool of wastewater as the shell is rotated to raise wastewater and discharge it over the media, which also rotates with the shell. In one embodiment the shell is cradled on belts, one of which is driven to rotate the shell. In another embodiment, the shell is mounted within a holding tank of wastewater and is driven by the release of gas under pressure from a conduit disposed beneath the shell, with the gas being trapped in cups arranged about the perimeter of the shell.

Sonar cross section of a coated hollow cylinder in water

Abstract: We study the acoustic scattering which occurs when a plane wave is incident on an infinite hollow elastic cylinder covered with an ideally bonded layer of viscoelastic and sound‐absorbing material. The structure is immersed in water and it contains air in the cavity. The normal‐mode solution is found in all four media and programmed for numerical evaluation in the exterior fluid. Series expressions for the differential and the sonar scattering cross sections are constructed and added by computer. Two size cylinders are investigated in a parametric study, and oscillations in the cross‐sectional values due to resonances in the shell and coating materials are found and plotted for the basically low‐frequency range k1c<20. The effect of a variable viscosity in the coating is analyzed, and as one would expect, progressively higher viscosity values damp out the rapid cross‐sectional oscillations and reduce the amplitudes to smaller values, down to an optimum point, beyond which the reverse effect begins to take...

Multi-purpose carrying bag or case

Abstract: A multi-purpose carrying bag or case having a parallelepiped shape is provided. The carrying bag or case comprises a shell of a watertight and airtight, rip-resistant material, the shell having top and bottom portions, first and second longitudinal side portions and first and second end portions; a slot-type opening provided in said upper portion and being closeable by means of a watertight and airtight zipper; and a fill-valve provided in said shell for filling the interior of the carrying bag or case.

Protective head gear

Abstract: A helmet or the like which has a rigid central shell and inner and outer inflatable impact absorbing liners with one-way valve means for inflating same. A plurality of inserts of foam or spongy material is secured to the inner shell and adapted to contact the head of the wearer. The liners may be removably secured to the shell.

Inter-shell correlations in the formation of singly charged ions near the Ar L-shell ionisation threshold

Abstract: The yield of singly charged ions is considered for inelastic fast-electron scattering. The densities of the generalised oscillator strengths are calculated in the single-electron approximation, taking account of the many-electron inter-shell correlations in the RPAE framework and out of it. It is demonstrated that a special type of inter-shell interaction of the electrons is responsible for this effect. This interaction arises as a consequence of the rearrangement of the core self-consistent field due to Auger-decay of the 2p6 vacancy. Such interactions may be considered as a type of the so-called post-collision interaction and this permits us to achieve reasonable agreement with the existing experimental data.

On cracks in shells with shear deformation

Abstract: Although much work has been done on the stress analysis of cracks in initially flat plates [1], theoretical treatment of cracks in initially curved plates or shells has received attention only in recent years. The presence of curvature in a shell generates deviation from behavior of flat plates, in that stretching loads will induce both extensional and bending stresses, while bending loads will also lead to both types of stresses. In the neighborhood of geometric defects such as man-made flaws or cracks, the stresses are redistributed and can lead to a reduction of the load carrying capacity of shell structures.

Vertically swingable camper shell

Abstract: A specially constructed hinge, mounted within the open body of a light truck, pivotally supports a body-enclosing, box-type shell behind the truck cab for vertical swinging movement of the shell about an axis extending transversely of the truck adjacent the uppermost portion of the cab end of the shell whereby the shell may be swung selectively up or down to open or close the body without encountering interference between the shell and cab The hinge comprises a pair of parallel, upright, laterally spaced plates each secured to a respective sidewall of the truck body and defining a pair of spaced, arcuate, non-concentric slots for captively retaining corresponding rollers carried by depending structure on said shell An electric winch selectively retracts or releases cable and pulley assemblies associated with respective pairs of rollers for powered raising or lowering of the shell relative to the truck body