Showing papers on "Shell (structure) published in 1990"

On a stress resultant geometrically exact shell model. Part IV: variable thickness shells with through-the-thickness stretching

Abstract: This paper in concerned with the extension of the shell theory and numerical analysis presented in Part I, II and III to include finite thickness stretch and initial variable thickness. These effects play a significant role in problems involving finite membrane strains, contact, concentrated surface loads and delamination (in composite shells). We show that a direct numerical implementation of the standard single extensible director shell model circumvents the need for rotational updates, but exhibits numerical ill-conditioning in the thin shell limit. A modified formulation obtained via a multiplicative split of the director field into an extensible and inextensible part is presented, which involves only a trivial modification of the weak form of the equilibrium equations considered in Part III, and leads to a perfectly well-conditioned formulation in the thin-shell limit. In sharp contrast with previous attempts in the context of the degenerated solid approach, the thickness stretch is an independent field, not a dependent variable updated iteratively via the plane stress condition. With regard to numerical implementation, an exact update procedure which automatically ensures that the thickness stretch remains positive is presented. For the present theory, standard displacement models would exhibit ‘locking’ in the incompressible limit as a result of the essentially three-dimensional character of the constitutive equations. A mixed formulation is described which circumvents this difficulty. Numerical examples are presented that illustrate the effects of the thickness stretch, the performance of the proposed mixed interpolation, and the well-conditioned response exhibited by the present approach in the thin-shell (inextensible director) limit.

A robust quadrilateral membrane finite element with drilling degrees of freedom

Abstract: A quadrilateral membrane finite element with drilling degrees of freedom is derived from variational principles employing an independent rotation field. Both displacement based and mixed approaches are investigated. The element exhibits excellent accuracy characteristics. When combined with a plate bending element, the element provides an efficient tool for linear analysis of shells.

Supershells in metal clusters

Abstract: Assuming a spherical mean field for electrons in metal clusters, single-particle level densities and electronic binding energies are calculated for clusters with up to 4000 valence electrons. Two phenomenological mean-field potentials, simulating microscopically calculated ones, are used. A global beating pattern, which envelopes individual shell oscillations, emerge from the calculations. The semiclassical interpretation of such a supershell structure, as proposed by Balian and Bloch in terms of interference of amplitudes associated with classical closed orbits, is found to be valid in the present case. Thermal effects, which tend to smear out shell and, therefore, supershell structures, are investigated qualitatively. Consequences of the shell structure are not obscured for cluster sizes up to several thousand atoms under the experimentally accessible temperature of 100--1000 K.

Torque controlled tubing

Abstract: Catheter tubing suitable for medical uses is disclosed, comprising an interior tubular portion and a concentric outer shell, wherein said interior portion extends beyond said concentric outer shell on at least one end of the longitudinal axis, and wherein the hardness of the concentric outer shell exceeds the hardness of the interior tubular portion, the interior tubular portion further comprising at least two resins co-tapered with respect to each other, the hardness of the innermost of which exceeds the hardness of the outermost.

Three dimensional packaging arrangement for computer systems and the like

Abstract: A three dimensional arrangement for packaging planar arrays of circuit components in a plurality of essentially planar layers in which the layers lie closely adjacent to one another is disclosed. Each layer is separated by a shell that interposes slots for allowing coolant to pass between the layers and electrical conductors through the shell, so that when the layers are placed together, the conductors form a bus through the structure.

Examples of post-mortality alteration in Recent brachiopod shells and (paleo)ecological consequences

Abstract: Post-mortality alteration of brachiopod shells under normal environmental conditions leads to high taphonomic loss, and to a poor contribution to the biodetrital soft sediment. The successive stages of alteration which shells undergo are: (bio)degradation of the organic matrix → shell softening → structural disaggregation or/and mechanical fragmentation; these processes depend on the shell structure (number of layers) and composition (organic and inorganic components), but very little on environmental conditions, except for the dissolution of inorganic shell constituents. Among the Brachiopoda, three types of alteration occur to different types of shells — Type I: two-layered chitino-phosphatic shell (species ofLingula andGlottidia) displays a rapid degradation of the organic matrix and mechanical abrasion, leading to total disappearance of the shell in 2 to 3 wk; Type II: two-layered carbonate shell, e.g.Terebratulina spp. [but notNotosaria nigricans (Sowerby) which may constitute a fourth shell type], exhibits degradation of the organic matrix of the secondary layer, shell softening, and structural disaggregation leading to shell disintegration in 6 to 7 mo with a concomitant contribution of calcitic microfibres to the sediment; Type III: three-layered carbonate shell, e.g.Gryphus vitreus (Born), undergoes organic degradation of the secondary layer, fragmentation of the anterior two-thirds of the shell, and slow degradation (because of the thick tertiary layer) of the posterior portion of the shell, with dissolution of the inorganic components (mainly in the tertiary layer) which make a relatively minor contribution to the sediment.

Child's combination carseat and stroller

Abstract: A convertible carseat/stroller is of the type having a molded plastic shell with lower door panels in the shell and a wheel assembly includes front and rear legs pivotally connected to a common support member within the shell and extensible between a downwardly divergent stroller position beneath the shell and upper retracted position within the shell under the control of a manual release member which is slidable along the support member for the wheel assembly. A handle unit is telescopically mounted with respect to the support member and is retractable into the shell when converted into a carseat. The door panels on the bottom of the shell follow movement of the wheel assembly so as to open in extending the wheel assembly between the shell for use as a stroller and will return to a closed position when the wheel assembly is retracted into the shell.

Large displacement and rotational formulation for laminated shells including parabolic transverse shear

Abstract: The paper presents an approach for a general laminated shell geometry describable by orthogonal curvilinear coordinates. The theory includes a through-the-thickness parabolic distribu- tion of transverse shear stress.-Additionally, a simplified approach that allows large displacements and rotations is incorporated. The theory is cast into a displacement-based finite element formula- tion and then specialized to a cylindrical shell geometry. The theory is then applied to the problem of a transversely loaded isotropic deep arch, and results show a slightly more flexible response compared with published results that are based upon inextensible assumptions. This problem also indicates that the usual locking associated with shell elements is apparently eliminated.

Cable having non-metallic armoring layer

Abstract: An animal-resistant optical fiber cable (20) includes a core (22) which comprises a transmission medium and a sheath system. The sheath system includes an outer jacket (65) and a dielectric armor (40) in the form of a shell. The shell comprises a plurality of longitudinally extending preformed segments (42-42) each being a composite comprising a substrate portion (50) and a layer (52) of a coating material which has a relatively high hardness disposed on an outer surface of the substrate portion. Each of the segments covers less than half of the periphery of the core and, in a preferred embodiment, eight segments are used. Further, the shell segments are stranded helically about the core with at least portions of longitudinal edge surfaces of adjacent segments being in engagement with each other. The shell segments not only provide rodent protection for the cable, but also they provide suitable tensile and compressive strength as well as suitable flexibility and cable bending performance. Further, because the cable in a preferred embodiment has an all-dielectric sheath system, it is inherently lightning, corrosion and EMP resistant.

Golf club shaft having selective reinforcement

Abstract: A golf shaft selectively reinforced with a composite outer shell substantially shorter in length than the golf shaft. A single shell is molded at a selected location over the shaft. The location of the shell controls the kick point of the golf shaft. The shell is comprised of a reinforced polymeric composite.

Computerized ply pattern generation

Abstract: A computerized process to generate ply patterns for smanufacturing industrial parts by stacking and molding a large number of plies is based on solid modeling. The outermost shell of the part is unfolded to a planar pattern using a surface development procedure. The part is decomposed based on the ply thickness; the shell with the ply thickness is removed from the solid model once the surface is unfolded. A set of ply patterns are formed by repeating the unfolding process until no more volume remains. More accurate patterns are produced in less time, especially plies for complexly shaped composite parts such as aircraft engine components.

Disposable urinary pad

Abstract: This invention provides a disposable urinary pad (10) comprising a liquid-impermeable backing (12), an absorbent core (13) and a liquid permeable facing (14) adhered to the shell so as to entrap the absorbent core therebetween. The absorbent core comprises a web of absorbent fibers and superabsorbent material and has a liquid-permeable transfer layer adjacent to one surface. The absorbent core is pleated, as in an M-configuration, to form therein a center lengthwise channel (24). The transfer layer, after pleating of the absorbent core, extends down the sides of the core so as to provide a liquid path to the bottom of the core.

A Poynting vector formulation for thin shells and plates, and its application to structural intensity analysis and source localization. Part I: Theory

Abstract: This paper deals with a formulation of the Poynting vector (structural intensity) for thin shells and plates, and its application to structural intensity analysis and source localization. The procedure begins with the insertion of a Taylor series expansion of the displacement components (about the middle surface of the shell) directly into the three‐dimensional representation of the Poynting vector. From this representation, an average power flow per unit length, or equivalently an intensity resultant, is derived, whose form permits expressibility in terms of force and moment resultants. The corresponding equations of continuity for energy are derived for both body and surface forces, and the time integral of the net outflow is developed, yielding a technique for source localization. This technique offers a method for the determination of the structural intensity of thin, elastic shells and plates, and is successful for source localization.

Vehicular lug nut cover and clip

Abstract: A cover for a bolt and an annular nut having a plurality of generally planar, side surfaces comprises a shell including a closed end portion and a plurality of side surfaces extending downwardly from the closed end portion. Each side surface of the shell has a generally planar inner wall that terminates in the bottom wall adapted for adjoining a flat surface of the wheel rim mounted on a vehicle with a plurality of such bolts and nuts. The cover further comprises a clip for inserting into the cavity defined by the shell side surfaces. This clip includes an annular ring and a plurality of spaced projections extending downwardly from the ring's perimeter, each projection adapted for engaging a side surface of the annular nut when the cover is installed thereover. The cover further comprises means for retaining the clip within the shell cavity. Preferred retaining means include: at least one inward protrusion from each inner wall against which a clip projection end section will engage when the clip is inserted into the cavity; and at least one pair of ring locators extending inwardly and axially along opposing inner walls of the shell. On a preferred basis, this outer shell is made from chrome-plated plastic and the clip from a zinc-plated metal such as steel, brass or aluminum.

On a moderate rotation theory of laminated anisotropic shells—Part 1. Theory☆

Abstract: A moderate rotation theory of laminated anisotropic shells, proposed by Schmidt and Reddy [ J. appl. Mech . 55 , 611–617.1988], is developed and its application is presented. All aspects of the derivations are explicitly developed and specific forms of the equations are derived in this part. The finite-element formulation and its applications are presented in Part 2 of the paper.

Detection of an expanding H I shell in the old supernova remnant CTB 80

Abstract: An expanding H I shell associated with the SNR CTB 80 has been detected. The expansion velocity and size indicate that the H I shell is an SNR shell. The center, shape, and mass of the shell match those of the IR shell detected by Fesen et al. (1988), supporting the idea that the pulsar has caught up with the SW portion of the shell and has produced its peculiar radio morphology. The shell's large 60 to 100 micron ratio implies that the larger grains may have been preferentially destroyed by the shock.

A shell around a black hole

Abstract: The authors present an exact solution describing a black hole surrounded by a massive shell. Energy conditions for the material of the shell are examined and yield its minimum radius.

Apparatus and method for forming and loading a magazine for prewound spools of web material

Abstract: An apparatus and method are disclosed for forming a very open shell (28) having axially extending lips (20c,20t) spaced sufficiently far apart to permit a prewound spool of web material (10) to be inserted radially, laterally into the very open form shell, after which the shell is closed and end caps (24) are installed. Apparatus are disclosed for forming the very open form shell (40), transferring the shell to a mechanism for applying end caps (48), inserting a prewound spool of web material (56) into the very open shell, positioning the spool accurately within the shell (780-856), closing the shell about the spool (58) and staking the end caps in place (60).

Method for producing a heatable and refrigerable element for a system handling small quantities of liquid, and an element manufactured by the method

Abstract: The invention relates to a method for producing a heatable and refrigerable element (12) for a system handling small amounts of liquid and to an element manufactured by the method. The element comprises flow channels (11) and one or more liquid spaces (8) communicating with them, the channels being provided with valves (10) connected to a refrigerator (25) and a heater (18), for blocking the channels by freezing the liquid in them. The element (12) is produced by using a removable mould which serves as a substrate for deposition and by depositing one or more metallic materials by electroformation or an equivalent procedure in such a way that the deposited metal forms a shell (5, 7) by removing the mould from inside the shell by dissolving or smelting, and by connecting the shell at the spot of the valves to a refrigerator (25) and a heater (18). The deposition is carried out so that there is a higher thermal conductivity at the spot of the valves (10) than in the adjacent shell areas.

Thermal buckling of laminated composite shells

Abstract: The linear buckling analysis of laminated composite cylindrical and conical shells under thermal load using the finite element method is reported here. Critical temperatures are presented for various cases of cross-ply and angle-ply laminated shells. The effects of radius/thickness ratio, number of layers, ratio of coefficients of thermal expansion, and the angle of fiber orientation have been studied. The results indicate that the buckling behavior of laminated shell under thermal load is different from that of mechanically loaded shell with respect to the angle of fiber orientation. Content H IGH-speed aerospace vehicles consisting of thin-shell elements are subjected to aerodynamic heating. This induces a temperature distribution over the surface and thermal gradient through the thickness of the shell. The compressive stresses, which in these circumstances develop, may cause buckling. Recently fiber-reinforced, laminated composites have begun to be used extensively in aerospace vehicle construction due to the high specific properties of the composites. In view of the above, the thermal buckling analysis of laminated composite shell assumes importance. Thermal buckling of isotropic cylindrical and conical shells have been reviewed by Bushnell. 1 Chang and Card2 investigated thermal buckling of stiffened, orthotropic, multilayered cylindrical shells. The governing equations obtained through the minimization of the total potential energy were solved by the finite difference technique with a few cases of practical problems. Nevertheless, this technique cannot be extended to other complex geometries and loading conditions. In this paper the Semiloof shell element formulated by Irons,3 which was adapted by the authors for thermal stress analyses of laminated plates and shells,4 is being extended to thermal buckling problems. The derivation of governing equation is a standard procedure, which uses the principle of minimum total potential energy. The characteristic finite element equilibrium equation thus obtained is [Ks] [q] = [F] where [Ks] is the structural stiffness matrix, [q} is the nodal displacement vector and [F] is the consistent nodal load vector. In order to establish the critical buckling state corresponding to the neutral equilibrium condition, the second variation of the total potential must be equated to zero, which gives rise to the condition, | [Ks] + \[Kg] j = 0, where [Kg] is the geometric stiffness matrix and X is the eigenvalue. The computer program (COMSAP) developed based on this formulation can handle general temperature variations, lamination parameters, and various boundary conditions. The material properties considered in the analysis of laminated shells are En/En = 10, Glt/Ett = 0.5,