Circular Shells Research Articles

Control of the Deformation of a Circular Cylindrical Shell

Within the framework of simplified nonlinear models, the initial nonlinear-elastic stage of obtaining hollow gear parts from the circular shells by the method of hydrostatic compression from circular circles is studied by analytical and numerical methods. It is shown that a suitable choice of a rigid rod inside the shell allows one to control the corrugation of the cross section of the pipe billet, to prevent the formation of unwanted folds and ribs on the surfaces of gear products.

Mathematical and experimental study of deformations of a steel roll of a road roller with a variable geometry of a contact surface

Abstract The lack of a common methodology on compaction theory stimulates developers of road construction equipment to create various approximate methods for their calculation, the number of which, at the present time, is comparable with the nomenclature of the proposed designs of rollers. The article presents the analysis of the deformable shell behavior of a road roller, and the compacted material under its compacting roller, in a situation when a rigid circular shell of the roller is replaced by a forcefully deformable elliptical shape, which, unlike the circular design, allows variation, adjustment and optimization of the road roller impact on the material to be compacted.

Investigation of Free Vibrations of Three-Layered Circular Shell Supported by Annular Ribs of Rigidity

The construction of a mathematical model and the development of an algorithm of free vibrations investigation in the three-layered circular shell with a light-weight aggregate supported by annular rigidity ribs are considered in paper. The hypotheses of Kirchoff-Lyav are accepted for external bearing layers of shell and for aggregate there is accepted the linear law of tangential displacements change by thickness. The boundary conditions of a shell region closed between the ribs are established. Using the boundary transition, conditions along the lines of the ribs, taking into account and without deformations of displacement in the ribs, but without taking into account the torsional rigidity in the ribs are determined. The equation of motion of supported three-layered shell is obtained. The frequencies of free vibrations were investigated and values of parameter of the first frequency of free vibrations for a shell, supported by one and three rigidity ribs, were calculated. There are given values depending on the physical and mechanical properties of materials and geometric dimensions of the shell, the curvature parameter, and the rigidity parameter of an aggregate.

Sound transmission through truncated conical shells

A theoretical model is presented to investigate the sound transmission through a thin-walled truncated circular conical shell excited by an oblique incident plane sound wave, which impinges on the outer surface of the shell. Love’s theory is used to implement the governing equations of the shell motion, and a convergent power series solution is applied to obtain the exact dynamic response of the shell. In order to calculate the acoustic pressure loadings acting on the shell surfaces, the shell is divided into several narrow segments which can be considered to be locally cylindrical. At first, the model predictions are compared with their experimental and analytical counterparts reported in the literature. Then, the effects of crucial design parameters including different boundary conditions at the ends of the shell, cone angle, incident sound wave angle, length, radius, thickness and material properties of the shell, and the material properties of the fluid media are studied on the characteristics of the sound transmission loss. The proposed model can provide an effective tool in the acoustic design stage of the truncated circular conical shells.

Nonlinear dynamic buckling of full-filled fluid sandwich FGM circular cylinder shells

This paper is concerned with the nonlinear dynamic buckling of sandwich functionally graded circular cylinder shells filled with fluid. Governing equations are derived using the classical shell theory and the geometrical nonlinearity in von Karman–Donnell sense is taken into account. Solutions of the problem are established by using Galerkin's method and Runge–Kutta method. Effects of thermal environment, geometric parameters, volume fraction index $ k $ and fluid on dynamic critical loads of shells are investigated.

Paleogeographic and paleoecological significance of Schachriomonia (Brachiopoda) from the Upper Ordovician of the Tarim Basin, Northwest China

AbstractThe atrypide brachiopod Schachriomonia is documented here for the first time from the upper Katian Hadabulaktag Formation on the northeastern edge of Tarim Basin in Northwest China. These shells are conspecific with the earlier reported Rhynchotrema pentagonia Fang in Liu and Fang, 1990 from the same region. This species is most similar to Schachriomonia parva Popov et al., 1999 described from the Upper Ordovician of the Chu-Ili and Chingiz terranes and less closely resembles species from North and South China, indicating a close paleogeographic connection between these plates and terranes and Tarim during the Late Ordovician. Its dominance at three horizons in the study area may indicate that this species was an opportunistic colonizer of the seafloor following ecological disruption, or alternatively that the larvae were substrate-selective. Variation in shell shape from a nearly circular shell outline with a dorsal sulcus and ventral fold in the smallest shells to a wider outline with a more reversed dorsal fold and ventral sulcus in the largest is an example of ontogenic development. This may have been an adaptation to accommodate the growing lophophore or development of gonads in the mantle cavity over the life of the brachiopod. A stronger tooth-socket connection in larger shells strengthened the hinge area to better withstand the stresses caused by the mass of a larger shell.

Free vibration response of functionally graded carbon nanotubes double curved shell and panel with piezoelectric layers in a thermal environment

This paper presents free vibration of the double-curved shells and panels with piezoelectric layers in a thermal environment. Vibration characteristics of elliptical, spherical, cycloidal, and toro circular shells of revolution are studied in detail. Vibration behavior of carbon nanotubes (CNTs) reinforced composite shells embedded with piezoelectric layers at the upper and lower surfaces is scrutinized. It is supposed that temperature changes linearly through-thickness direction. Reissner- Mindlin and the first order shear deformation (FSDT) theories are implemented to derive the governing equations of the considered structures. The distribution of nanotubes is assumed to be linear along the thickness direction. For solving the equation, the General Differential Quadrature (GDQ) method is used to obtain a numerical analysis for the dynamics of the objective structures. Finally, the effects of boundary conditions, the thickness of piezoelectric layers, functional distribution of CNTs, thermal environment and kinds of the circuit (opened-circuit and closed-circuit) are analyzed. Eigenvalue system is solved to obtain natural frequencies. It is delineated that the obtained fundamental frequency by the closed -circuit is smaller than those obtained by the opened-circuit. Another interesting result is that the natural frequency is decreased by increasing temperature.

Investigations on dynamic analysis and free vibration of FGMs rotating circular cylindrical shells

In this study, the free vibration studies of rotating circular cylindrical shells composited of functionally graded materials (FGMs) layer with simply supported boundary condition has been investigated. The FGMS layer composed from metal and ceramic that metal has on the outer surface and ceramic has on the inner surface of the circular cylinder shells. Based on the Love’s first approximation shell theory, relations between strain and displacement are expressed. Then, according to Hamilton’s principle, the governing equations for the cylindrical shell are extracted. Also, due to the simply supported boundary condition, the Navier’s solution is used to solve the equations of the cylindrical shell. Then the results obtained with the present method compared with the results of other investigations. The results are compared with a results that presented by other researchers. Finally, the results obtained from the rotating FGMs cylindrical shells for length to radius ratio, rotating speed, axial and circumferential wave number, are presented.

A novel and enigmatic two-holed shell aperture in a new species of suspension-feeding worm-snail (Vermetidae)

Shell aperture modifications are well known in terrestrial and aquatic gastropods, with apertural lip thickening and tooth development common in species with terminal (determinate) shell growth. In contrast, secondary shell openings are rare in snails and are largely limited to slit shells, keyhole limpets, and abalone of the Vetigastropoda. When such features occur in other groups, they are noteworthy and raise interesting questions concerning the functional/adaptive significance of these shell modifications. Here we report on one such modification in a newly described species of vermetid snail. Members of the worm-snail family Vermetidae are sessile, suspension-feeding caenogastropods found in warm temperate to tropical marine environments worldwide. As juveniles, vermetids permanently cement their shells to hard substrata and subsequently produce irregularly coiled polychaete-like shell tubes with indeterminate growth and typically a simple circular shell aperture. In one previously studied group (genusCupolaconcha), the aperture can be covered by a shell dome with a central slit that retains its widest opening in the center of the aperture. Vermetid specimens collected in the barrier reefs of Belize and the Florida Keys show an extreme aperture modification previously unknown in Gastropoda, in which the shell opening is covered by an apertural dome that leaves two equal-sized circular holes, each corresponding to the inflow and outflow water exchange currents of the animal’s mantle cavity. The function of this perforated apertural dome is unknown, and it is in some ways antithetical to the suspension feeding habit of these snails. Further field and laboratory-based studies will be needed to clarify the functional significance and trade-offs of this unique morphology. The new taxon, which is not closely related to the previously described dome-building cladeCupolaconcha, is described and named asVermetus biperforatusBieler, Collins, Golding & Rawlings n. sp.

Discovery of a putative supernova remnant around the long-period X-ray pulsar SXP 1323 in the Small Magellanic Cloud

ABSTRACT We report the discovery of a circular shell centred on the Be X-ray binary (BeXB) SXP 1323 in the Small Magellanic Cloud. The shell was detected in an H α image obtained with the Very Large Telescope. Follow-up spectroscopy with the Southern African Large Telescope showed that the shell expands with a velocity of ${\approx }100{\rm \, km\, s^{-1}}$ and that its emission is due to shock excitation. We suggest that this shell is a remnant of the supernova explosion that led to the formation of SXP 1323’s neutron star ${\approx }40\, 000$ yr ago. SXP 1323 represents the second known case of a BeXB associated with a supernova remnant (the first one is SXP 1062). Interestingly, both of these BeXBs harbour long-period pulsars and are located in a low-metallicity galaxy.

Mechanical Analysis of Vibrations in a Switched Reluctance Motor Using Experimental, Numerical, and Analytical Methodologies

Abstract Switched reluctance motors (SRM) are characterized by rotor/stator pole pairs, in which the wound field coils in the stator poles induce magnetic reluctance in the rotor poles to create torque. However, noise development during motor operation is a key issue for this class of motors and much of the work to understand the acoustics and vibrations of these systems is limited to comparing experimental measurements with high-performance, multiphysics simulations. This work focuses on mathematical analysis of these systems through reduced-order modeling using both numerical and analytical methods, and the results are compared against experimental measurements of a typical SRM. To describe the underlying response of the experimental system, a circular shell model is developed for the stator, and electromagnetic finite element analysis is utilized to develop a physically motivated forcing profile for the experimental system. A numerical simulation model is then constructed by applying the calculated electromagnetic forces to the stator, and effective system parameters are determined by calibrating the numerical model to match experimental measurements. An analytical approximation is then derived by leveraging disparate timescales in the problem, and it is shown that the analytical solution accurately recovers the numerical and experimental results while also providing insight into the underlying physics of the experimental system.

Giant Magneto Impedance Effect of Co-Based Metallic Fiber Under Bias Magnetic Field

The giant magneto impedance, GMI, effect of Co-based metallic fibers prepared by melt-extracted technology is investigated under different bias direct electrical current Ib. The GMI curves have single peaks which are symmetric about zero field at and below 1MHz. However, the bimodal GMI curves which have asymmetric peaks are observed when Ib is over 2mA at 0.1MHz. And asymmetric GMI, AGMI, effect is also appeared at 1MHz when Ib just is 1mA and the field sensitivity of GMI effect is increased 5.6 times. The GMI effect and magnetization process is affected by the bias magnetic field profoundly induced by Ib, which is correlated with the outer shell domain structures with circumferentially magnetization easy axis existed in the outer shell of Co-rich magnetic wires with low and negative magnetostriction. Below 1 MHz, only if the bias current is over 1.5mA which induces a magnetic circumferential magnetic field is above the coercivity of 14.4A/m, the circumferential magnetization and GMI effect can experience the bias magnetic field effect. Above 1MHz, the skin effect gets stronger and significantly decreases the total participants of circular magnetization process in the fibers and consequently, the circular outer shell magnetization process gets much sensitive to circular bias magnetic field. AGMI effect with high field sensitivity is realized due to the bias current.

A higher-order isoparametric superelement for free vibration analysis of functionally graded shells of revolution

A higher-order isoparametric superelement is developed to study the vibration of functionally graded shells of revolution. The effective material properties of functionally graded materials (FGMs) vary continuously along the thickness direction of the shell in accordance with the power law distribution. The governing equations are presented based on the three-dimensional elasticity theory using Hamilton’s principle. Since the isoparametric formulation is considered, a unified formulation is presented for all types of shells of revolution. The properties of the FG shells are graded through the thickness direction, and consequently, the analysis of such structures is quite difficult using conventional three-dimensional finite elements. The proposed superelement facilitates the analysis of FG shell structures. Different types of circular shell structures including cylindrical, conical, spherical and circular toroid are considered in this study. To show the accuracy and efficiency of the proposed superelement, different comparative studies are presented.

Confirmation of G6.31+0.54 as a part of a Galactic supernova remnant

A combination of archival multi-frequency radio observations with narrow-band HAlpha optical imagery and new confirmatory optical spectroscopy have shown that candidate supernova remnant G6.31+0.54 can now be confirmed as part of a Galactic supernova remnant (SNR). It has non-thermal emission, an optical emission line spectrum displaying shock excitation and standard SNR line ratios, fine filamentary structures in HAlpha typical of optical remnants and closely overlapping radio and optical footprints. An X-ray ROSAT source 1RXS J175752.1-231105 was also found that matches the radio and optical emission though a definite association is not proven. Nevertheless, taken together, all these observed properties point to a clear SNR identification for this source. We provide a rough estimate for the kinematic distance to G6.31+0.54 of ~4.5kpc. The detected optical filaments are some ~10arcminutes in extent (or about 13 pc at the assumed distance). However, as only a partial arcuate structure of the SNR can be seen (and not a full shell) the full angular extent of the SNR is unclear. Hence the physical extent of the observed partial shell is also difficult to estimate. If we assume an approximately circular shell then a conservative fit to the optical arc shaped filaments gives an angular diameter of ~20 arcminutes corresponding to a physical diameter of ~26 pc that shows this to be an evolved remnant.

Residue analysis, use-wear patterns, and replicative studies indicate that sandstone tools were used as reamers when producing shell fishhooks on San Nicolas Island, California

Elucidating the tools and production steps involved in manufacturing the characteristic circular shell fishhooks found on the California Channel Islands has been a long-standing problem in California archaeology. A prehistoric production site for shell fishhooks excavated on the most remote island, San Nicolas Island, has provided a rare opportunity to examine manufacturing sequences. We have previously employed a multidisciplinary research approach to demonstrate that fishhook production at this site involved using sandstone slabs as abraders, or “saws”. Here, we use chemical residue analysis, replicative experiments, and microwear patterns to show that fishhook production also involved the use of small pointed pieces of sandstone as reamers. These results bring us one step closer to understanding the complete prehistoric toolkit used for production of circular shell fishhooks.

Taxonomic revision of the genus Ichthyosarcolites Demarest, 1812, and description of a new canaliculate rudist from the Cenomanian of Slovenia: Oryxia sulcata gen. et sp. nov. (Bivalvia, Hippuritida)

Ichthyosarcolites was amongst the first rudist genera to be described. Nineteen species have been assigned to this genus since its introduction in 1812, all from shallow-marine tropical carbonates of Albian and Cenomanian age (mid-Cretaceous). Almost all nominal species suffer from vague original descriptions, and some forms were inaccurately assigned to the genus. Several species were defined on the basis of the number of flanges along the shell, such as Ichthyosarcolites rotundus, I. monocarinatus, I. triangularis, I. bicarinatus, I. tricarinatus, I. alatus and I. polycarinatus. An analysis of the relative position of the flanges on the shell by hierarchical clustering helps with taxon definition. Two species with a single flange are here recognised, one with a dorsal flange (I. monocarinatus), the other with a ventral one (I. triangularis). There is no consistency in flange distribution on the shells whatever their number is, i.e., two or more, and homology of individual flanges cannot be demonstrated. Morphometric analysis finds a link between the shape of the general cavity and flange number and distribution. Out of the nineteen species named in the literature, only four can be retained after our thorough morphological analyses, namely Ichthyosarcolites rotundus (defined by a circular shell that lacks flanges), I. triangularis (defined by a single dorsal flange), I. monocarinatus (defined by a single ventral flange) and I. bicarinatus (defined by two flanges or more). Flanges have very variable morphological features among I. bicarinatus. In addition, we here erect Oryxia sulcata nov. gen. et sp., a new form based on specimens previously identified as I. bicarinatus, I. poljaki and I. tricarinatus. This new taxon is defined by the presence of a ligament groove, this in contrast to Ichthyosarcolites which never shows any trace of ligament. Oryxia nov. gen. may be the sister group of a clade of canaliculated forms that lost contact between the ligament support and the shell exterior and includes antillocaprinids, trechmannellids or ichthyosarcolitids.

Analysis of efficiency of deck diverce masking from distribution-diversion glaiders by a formable embody buffer zone

The object of research is the process of elastic interaction of an ultrasonic beam with a cylindrical module enclosing the airplane in the form of two circular shells of the same length coaxially connected by their ends, the hermetical gap between them filled with liquid. One of the problematic areas of the study is that the dislocation of deck aviation in the open waist plane allows the means of detecting the suborbital and atmospheric reconnaissance of the enemy to determine undefined not only the initial coordinates but also its coordinate functions for the entire period of subsequent trajectory travel. Finally, the on-board glider equipment, taking this information as the original one, makes it possible, with anticipation, accurately, to fire at the theoretical trajectory of motion, thereby increasing the probability of hitting the target. Therefore, it is necessary to ensure 100 % masking of deck aviation at open launch positions. This will significantly reduce or completely eliminate and improve the efficiency and life-span of the aircraft as a whole. It is shown that, when the case is subjected to symmetrical oscillations, which greatly exceed the resistance to antisymmetric vibrations, the sound permeability of the case elements will increase solely by bending vibrations. It is revealed that the «acoustic transparency» of the device case serves as an intensive transfer of the sound energy of the bending waves of the case and completely depends on the frequency of the acoustic radiation, as well as the incidence angles. Thus, by creating a circular or ellipsoidal enclosing cylindrical module in the form of two circular shells filled with liquid, it will be possible to quickly disassemble and place it over another object in a matter of hours.

Optical spectroscopy of the blue supergiant Sk−69° 279 and its circumstellar shell with SALT

We report the results of optical spectroscopy of the blue supergiant Sk-69 279 and its circular shell in the Large Magellanic Cloud (LMC) with the Southern African Large Telescope (SALT). We classify Sk-69 279 as an O9.2 Iaf star and analyse its spectrum by using the stellar atmosphere code CMFGEN, obtaining a stellar temperature of \approx 30 kK, a luminosity of log(L_*/Lsun)=5.54, a mass-loss rate of log(\dot{M}/(Msun/yr))=-5.26, and a wind velocity of 800 km/s. We found also that Sk-69 279 possesses an extended atmosphere with an effective temperature of \approx 24 kK and that its surface helium and nitrogen abundances are enhanced, respectively, by factors of \approx 2 and 20--30. This suggests that either Sk-69 279 was initially a (single) fast-rotating (\ga 400 km/s) star, which only recently evolved off the main sequence, or that it is a product of close binary evolution. The long-slit spectroscopy of the shell around Sk-69 279 revealed that its nitrogen abundance is enhanced by the same factor as the stellar atmosphere, which implies that the shell is composed mostly of the CNO processed material lost by the star. Our findings support previous propositions that some massive stars can produce compact circumstellar shells and, presumably, appear as luminous blue variables while they are still on the main sequence or have only recently left it.

On Elastoplastic Buckling Analysis of Cylinders Under Nonproportional Loading by Differential Quadrature Method

The paper investigates the elastoplastic buckling of thin circular shells subjected to nonproportional loading consisting of axial tensile stress and external pressure. The governing equations of buckling for cylindrical shells derived by Flugge serve as the basis of analysis. To capture the elastic/plastic behavior, two plasticity theories are considered; the flow theory and the deformation theory of plasticity. Plastic buckling pressures for cylinders with various combinations of boundary conditions are presented for which no analytical solutions are available. The results obtained from the flow and deformation theories confirm that, under over-constrained kinematic assumptions, the deformation theory tends to provide lower values of buckling pressure and the discrepancies in the results from the two plasticity theories increase with increasing thickness-to-radius ratios, tensile stresses, boundary clamping and E/[Formula: see text] ratios. The plastic buckling results obtained by means of the differential quadrature method are compared with carefully conducted FEA results for both the flow and the deformation theory of plasticity. The reasons underlying the apparent plastic buckling paradox are thus investigated for a vast class of boundary conditions and loads.

Reduction of technological risks of flight operation by artificial formation of the buffer zone to penetrating acoustic radiation

The possibility of reducing technological risks from the effect of penetrating acoustic radiation on flight equipment of flight elements is analyzed. The object of research is the process of elastic interaction of an ultrasonic beam with a metal bush in the form of two identical lengths and different shell radii connected at the ends by flat rings, the internal gap between them is filled with liquid. The disadvantage of the proposed technical solution is to recognize some complication in the design of the float gyro. Results of semi-detailed experimental studies of the float gyroscope in an acoustic medium are presented. As shown by experimental studies, the equipment of the float gyro from outside the thermal casing by a bush of two coaxial, identical lengths, circular shells makes it possible, with artificial irradiation with ultrasonic waves of the outer shell, to create conditions for formation of a caustic zone in the liquid between the shell spaces. This will lead to the creation of an increased energy state relative to the initial state, in the form of a surface coaxial with the internal cavity of the device body. The attainment of the incidence angle equal to the coincidence angle of the wave of the ultrasonic beam allows the outer shell to be converted into an acoustically transparent design. Thus, the entire energy of the ultrasonic radiator will go to the formation of the maximum energy state of the inter-shell liquid turbulent in structure and the available cavitation spaces. This will create a buffer zone for the propagation of external acoustic waves, in which intense dissipation of its energy takes place, and thus the level of the acoustic radiation passing through the device is reduced to zero. At the wave coincidence angle θс=10 degree, the offset of the output signal of the device is 1.24 mV. The measurement error is Δωav≈0.00282 degree·s-1.