Free vibrations of circular cylindrical shells
Armenàkas, Anthony E; Herrmann, George
2013-01-01
Free Vibrations of Circular Cylindrical Shells deals with thin-walled structures that undergo dynamic loads application, thereby resulting in some vibrations. Part I discusses the treatment of problems associated with the propagation of plane harmonic waves in a hollow circular cylinder. In such search for solutions, the text employs the framework of the three-dimensional theory of elasticity. The text explains the use of tables of natural frequencies and graphs of representative mode shapes of harmonic elastic waves bounding in an infinitely long isotropic hollow cylinder. The tables are
Natural frequency of a circular cylindrical shell filled with fluid
Energy Technology Data Exchange (ETDEWEB)
Jeong, Kyeong Hoon; Kim, Tae Wan; Kim, Kang Soo; Park, Keun Bae [Korea Atomic Energy Research Institute, Taejon (Korea)
1998-08-01
This report presents an analytical method for evaluating the free vibration of a circular cylindrical shell filled with bounded compressible fluid. The analytical method was developed by means of the finite Fourier series expansion method. The compressible fluid motion was determined by means of the linear velocity potential theory. To clarify the validity of the analytical method, the natural frequencies of a circular cylindrical shell with the clamped-clamped boundary condition, and filled with water, were obtained by the analytical method and the finite element method using a commercial ANSYS 5.2 software. Excellent agreement on the natural frequencies of the fluid-filled shell structure was found. The compressibility and density of fluid effects the normalized coupled natural frequencies were investigated. The density of fluid affects on all coupled natural frequencies of the shell,, whereas the compressibility and bounding of fluid affects mainly on the natural frequencies of lower circumferential modes. The theory developed in this report will be applicable to the dynamic analysis of a core support barrel in SMART integral reactor filled with coolant. (author). 15 refs., 14 figs., 1 tab.
Vibrations of cantilevered circular cylindrical shells Shallow versus deep shell theory
Lee, J. K.; Leissa, A. W.; Wang, A. J.
1983-01-01
Free vibrations of cantilevered circular cylindrical shells having rectangular planforms are studied in this paper by means of the Ritz method. The deep shell theory of Novozhilov and Goldenveizer is used and compared with the usual shallow shell theory for a wide range of shell parameters. A thorough convergence study is presented along with comparisons to previously published finite element solutions and experimental results. Accurately computed frequency parameters and mode shapes for various shell configurations are presented. The present paper appears to be the first comprehensive study presenting rigorous comparisons between the two shell theories in dealing with free vibrations of cantilevered cylindrical shells.
Internal resonance of axially moving laminated circular cylindrical shells
Wang, Yan Qing; Liang, Li; Guo, Xing Hui
2013-11-01
The nonlinear vibrations of a thin, elastic, laminated composite circular cylindrical shell, moving in axial direction and having an internal resonance, are investigated in this study. Nonlinearities due to large-amplitude shell motion are considered by using Donnell's nonlinear shallow-shell theory, with consideration of the effect of viscous structure damping. Differently from conventional Donnell's nonlinear shallow-shell equations, an improved nonlinear model without employing Airy stress function is developed to study the nonlinear dynamics of thin shells. The system is discretized by Galerkin's method while a model involving four degrees of freedom, allowing for the traveling wave response of the shell, is adopted. The method of harmonic balance is applied to study the nonlinear dynamic responses of the multi-degrees-of-freedom system. When the structure is excited close to a resonant frequency, very intricate frequency-response curves are obtained, which show strong modal interactions and one-to-one-to-one-to-one internal resonance phenomenon. The effects of different parameters on the complex dynamic response are investigated in this study. The stability of steady-state solutions is also analyzed in detail.
Simplified dispersion curves for circular cylindrical shells using shallow shell theory
Sarkar, Abhijit; Sonti, Venkata R.
2009-04-01
An alternative derivation of the dispersion relation for the transverse vibration of a circular cylindrical shell is presented. The use of the shallow shell theory model leads to a simpler derivation of the same result. Further, the applicability of the dispersion relation is extended to the axisymmetric mode and the high frequency beam mode.
Nonlinear vibrations of fluid-filled clamped circular cylindrical shells
Karagiozis, K. N.; Amabili, M.; Païdoussis, M. P.; Misra, A. K.
2005-12-01
In this study, the nonlinear vibrations are investigated of circular cylindrical shells, empty or fluid-filled, clamped at both ends and subjected to a radial harmonic force excitation. Two different theoretical models are developed. In the first model, the standard form of the Donnell's nonlinear shallow-shell equations is used; in the second, the equations of motion are derived by a variational approach which permits the inclusion of constraining springs at the shell extremities and taking in-plane inertial terms into account. In both cases, the solution includes both driven and companion modes, thus allowing for a travelling wave in the circumferential direction; they also include axisymmetric modes to capture the nonlinear inward shell contraction and the correct type (softening) nonlinear behaviour observed in experiments. In the first model, the clamped beam eigenfunctions are used to describe the axial variations of the shell deformation, automatically satisfying the boundary conditions, leading to a 7 degree-of-freedom (dof) expansion for the solution. In the second model, rotational springs are used at the ends of the shell, which when large enough reproduce a clamped end; the solution involves a sine series for axial variations of the shell deformation, leading to a 54 dof expansion for the solution. In both cases the modal expansions satisfy the boundary conditions and the circumferential continuity condition exactly. The Galerkin method is used to discretize the equations of motion, and AUTO to integrate the discretized equations numerically. When the shells are fluid-filled, the fluid is assumed to be incompressible and inviscid, and the fluid structure interaction is described by linear potential flow theory. The results from the two theoretical models are compared with existing experimental data, and in all cases good qualitative and quantitative agreement is observed.
Crack detection in circular cylindrical shells using differential quadrature method
International Nuclear Information System (INIS)
The differential quadrature method combined with an evolutionary optimization algorithm has been proposed for crack detection in cylindrical shell structures. The circumferential crack, which is assumed to be open, is modeled by the extended rotational spring. A crack with finite length divides the shell into four segments. The governing differential equations of motion of the shell are formulated based on Flugge's shell theory. Applying differential quadrature to the differential equations of each segment and the corresponding boundary and continuity conditions results in an algebraic system of equations. Then, an eigenvalue analysis is performed to obtain the natural frequencies of the cracked shell. To identify the crack parameters, an optimization problem is defined and minimized by Bees algorithm, a swarm-based evolutionary optimization technique. The integrity and applicability of the proposed method is confirmed by some experimental case studies. The results show that the crack statuses are predicted well. -- Highlights: • The problem of crack detection in cylindrical shell structures is investigated. • To do this, the differential quadrature method and bees algorithm has been used. • Numerical and experimental studies on the cracked free–free shells were conducted. • The results showed that the crack locations, sizes and depths were predicted well
Bending Boundary Layers in Laminated-Composite Circular Cylindrical Shells
Nemeth, Michael P.; Smeltzer, Stanley S., III
2000-01-01
A study of the attenuation of bending boundary layers in balanced and unbalanced, symmetrically and unsymmetrically laminated cylindrical shells is presented for nine contemporary material systems. The analysis is based on the linear Sanders-Koiter shell equations and specializations to the Love-Kirchhoff shell equations and Donnell's equations are included. Two nondimensional parameters are identified that characterize the effects of laminate orthotropy and anisotropy on the bending boundary-layer decay length in a very general manner. A substantial number of structural design technology results are presented for a wide range of laminated-composite cylinders. For all laminates considered, the results show that the differences between results obtained with the Sanders-Koiter shell equations, the Love-Kirchhoff shell equations, and Donnell's equations are negligible. The results also show that the effect of anisotropy in the form of coupling between pure bending and twisting has a negligible effect on the size of the bending boundary-layer decay length of the balanced, symmetrically laminated cylinders considered. Moreover, the results show that coupling between the various types of shell anisotropies has a negligible effect on the calculation of the bending boundary-layer decay length in most cases. The results also show that, in some cases, neglecting the shell anisotropy results in underestimating the bending boundary-layer decay length and, in other cases, results in an overestimation.
Institute of Scientific and Technical Information of China (English)
2008-01-01
The effect of matrix cracking on the bifurcation creep buckling of viscoelastic laminated circular cylindrical shells is investigated.The viscoelastic behavior of laminas is modeled by Schapery’s integral constitutive equation with growing matrix cracks.The values of damage variables are correlated to non-dimensional density of matrix cracks relying on the formulas from mesomechanics approach,and the evolution equation predicting the growth rate of density of matrix cracks is assumed to follow a power type relation with transverse tensile stress.The governing equations for prebuckling creep deformation and bifurcation buckling of laminated circular cylindrical shells under axial compression are obtained on the basis of the Donnell type shallow shell theory and Kármán-Donnell geometrically nonlinear relationship.Corresponding solution strategy is constructed by integrating finite-difference technique,trigonometric series expansion method and Taylor’s numerical recursive scheme for convolution integration.The bifurcation creep buckling of symmetrically laminated glass-epoxy circular cylindrical shells with matrix creep cracking coupled are examined for various geometrical parameters and parameters of damage evolution as well as boundary conditions.The numerical results show that matrix creep cracking remarkably shortens the critic time of bifurcation buckling and reduces the durable critic loads,and its effects become weak and finally vanish with the increase of the ratio of radius to thickness in the case of short laminated circular cylindrical shells,also the influence of the matrix creep cracking is mainly dependent on the boundary conditions at two ends for moderately long circular cylindrical shells.
Institute of Scientific and Technical Information of China (English)
PENG Fan; FU YiMing; CHEN YaoJun
2008-01-01
The effect of matrix cracking on the bifurcation creep buckling of viscoelastic laminated circular cylindrical shells is investigated. The viscoelastic behavior of laminas is modeled by Schapery's integral constitutive equation with growing ma-trix cracks. The values of damage variables are correlated to non-dimensional density of matrix cracks relying on the formulas from meso-mechanics approach, and the evolution equation predicting the growth rate of density of matrix cracks is assumed to follow a power type relation with transverse tensile stress. The gov-erning equations for pre-buckling creep deformation and bifurcation buckling of laminated circular cylindrical shells under axial compression are obtained on the basis of the Donnell type shallow shell theory and Karman-Donnell geometrically nonlinear relationship. Corresponding solution strategy is constructed by inte-grating finite-difference technique, trigonometric series expansion method and Taylor's numerical recursive scheme for convolution integration. The bifurcation creep buckling of symmetrically laminated glass-epoxy circular cylindrical shells with matrix creep cracking coupled are examined for various geometrical parame-ters and parameters of damage evolution as well as boundary conditions. The nu-merical results show that matrix creep cracking remarkably shortens the critic time of bifurcation buckling and reduces the durable critic loads, and its effects become weak and finally vanish with the increase of the ratio of radius to thickness in the case of short laminated circular cylindrical shells, also the influence of the matrix creep cracking is mainly dependent on the boundary conditions at two ends for moderately long circular cylindrical shells.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The present work discusses the problem of dynamic stability of a viscoelastic circular cylindrical shell, according to revised Timoshenko theory, with an account of shear deformation and rotatory inertia in the geometrically nonlinear statement. Proceeding by Bubnov-Galerkin method in combination with a numerical method based on the quadrature formula the problem is reduced to a solution of a system of nonlinear integro-differential equations with singular kernel of relaxation. For a wide range of variation of physical mechanical and geometrical parameters, the dynamic behavior of the shell is studied. The influence of viscoelastic properties of the material on the dynamical stability of the circular cylindrical shell is shown. Results obtained using different theories are compared.
Free-vibration Characteristics of Laminated Angle-ply Non-circular Cylindrical Shells
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M. Ganapathi
2004-10-01
Full Text Available This paper deals with the free-vibration behaviour of anisotropic laminated angle-ply noncircular cylindrical shells using finite element approach. The formulation is based on first-ordershear deformation theory. The present model accounts for in-plane and rotary inertia effects. A detailed study has been carried out to highlight the effects of shell geometry, cross-sectionalproperties, lay-up and ply-angles on the natural frequencies of different types of modes of vibration of non-circular elliptical shell structures.
Free vibrations of finite circular cylindrical shells and tubes with and without a surrounding fluid
International Nuclear Information System (INIS)
Numerical models are evaluated for determining the natural frequencies of thin-walled closed circular cylindrical shells and straight tube bundles in a fluid or without a fluid. Experiments are described to check the reliability of the numerical models. Some of the models are applied for the vibration analysis of some parts of the sodium-steam heat exchangers of the SNR-300 reactor in Kalkar (West Germany). (Auth.)
Free vibration of symmetric angle-ply laminated circular cylindrical shells
International Nuclear Information System (INIS)
Free vibration of symmetric angle-ply laminated circular cylindrical shells is studied using Spline approximation. The equations of motions in longitudinal, circumferential and transverse displacement components, are derived using Love's first approximation theory. The coupled differential equations are solved using Spline approximation to obtain the generalized eigenvalue problem. Parametric studies are performed to analyse the frequency response of the shell with reference to the material properties, number of layers, ply orientation, length and circumferential node number and different boundary conditions
Yuan, Li-Yun; Xiang, Yu; Lu, Jing; Jiang, Hong-Hua
2015-12-01
Based on the transfer matrix method of exploring the circular cylindrical shell treated with active constrained layer damping (i.e., ACLD), combined with the analytical solution of the Helmholtz equation for a point source, a multi-point multipole virtual source simulation method is for the first time proposed for solving the acoustic radiation problem of a submerged ACLD shell. This approach, wherein some virtual point sources are assumed to be evenly distributed on the axial line of the cylindrical shell, and the sound pressure could be written in the form of the sum of the wave functions series with the undetermined coefficients, is demonstrated to be accurate to achieve the radiation acoustic pressure of the pulsating and oscillating spheres respectively. Meanwhile, this approach is proved to be accurate to obtain the radiation acoustic pressure for a stiffened cylindrical shell. Then, the chosen number of the virtual distributed point sources and truncated number of the wave functions series are discussed to achieve the approximate radiation acoustic pressure of an ACLD cylindrical shell. Applying this method, different radiation acoustic pressures of a submerged ACLD cylindrical shell with different boundary conditions, different thickness values of viscoelastic and piezoelectric layer, different feedback gains for the piezoelectric layer and coverage of ACLD are discussed in detail. Results show that a thicker thickness and larger velocity gain for the piezoelectric layer and larger coverage of the ACLD layer can obtain a better damping effect for the whole structure in general. Whereas, laying a thicker viscoelastic layer is not always a better treatment to achieve a better acoustic characteristic. Project supported by the National Natural Science Foundation of China (Grant Nos. 11162001, 11502056, and 51105083), the Natural Science Foundation of Guangxi Zhuang Autonomous Region, China (Grant No. 2012GXNSFAA053207), the Doctor Foundation of Guangxi
AMABILI, M.; PELLICANO, F.; PAÏDOUSSIS, M. P.
1999-08-01
The study presented is an investigation of the non-linear dynamics and stability of simply supported, circular cylindrical shells containing inviscid incompressible fluid flow. Non-linearities due to large-amplitude shell motion are considered by using the non-linear Donnell's shallow shell theory, with account taken of the effect of viscous structural damping. Linear potential flow theory is applied to describe the fluid-structure interaction. The system is discretiszd by Galerkin's method, and is investigated by using a model involving seven degrees of freedom, allowing for travelling wave response of the shell and shell axisymmetric contraction. Two different boundary conditions are applied to the fluid flow beyond the shell, corresponding to: (i) infinite baffles (rigid extensions of the shell), and (ii) connection with a flexible wall of infinite extent in the longitudinal direction, permitting solution by separation of variables; they give two different kinds of dynamical behaviour of the system, as a consequence of the fact that axisymmetric contraction, responsible for the softening non-linear dynamical behaviour of shells, is not allowed if the fluid flow beyond the shell is constrained by rigid baffles. Results show that the system loses stability by divergence.
Wang, Y. Q.; Guo, X. H.; Li, Y. G.; Li, J.
2010-03-01
This is a study of nonlinear traveling wave response of a cantilever circular cylindrical shell subjected to a concentrated harmonic force moving in a concentric circular path at a constant velocity. Donnell's shallow-shell theory is used, so that moderately large vibrations are analyzed. The problem is reduced to a system of ordinary differential equations by means of the Galerkin method. Frequency-responses for six different mode expansions are studied and compared with that for single mode to find the more contracted and accurate mode expansion investigating traveling wave vibration. The method of harmonic balance is applied to study the nonlinear dynamic response in forced oscillations of this system. Results obtained with analytical method are compared with numerical simulation, and the agreement between them bespeaks the validity of the method developed in this paper. The stability of the period solutions is also examined in detail.
ANALYSIS OF THE DYNAMIC STABILITY OF ELECTRICAL GRADED PIEZOELECTRIC CIRCULAR CYLINDRICAL SHELLS
Institute of Scientific and Technical Information of China (English)
ZhuJunqiang; ShenYapeng; ChenChangqing
2004-01-01
A system of Mathieu Hill equations have been obtained for the dynamic stability analysis of electrical graded piezoelectric circular cylindrical shells subjected to the combined loading of periodic axial compression and radial pressure and electric field. Bolotin's method is then employed to obtain the dynamic instability regions. It is revealed that the piezoelectric effect, the piezoelectric graded effect and the electric field only have minor effect on the unstable region. In contrast, the geometric parameters, the rigidity of constituent materials and the external loading play a dominant role in determining the unstable region.
Institute of Scientific and Technical Information of China (English)
2008-01-01
Based on the first order shear deformation theory and classic buckling theory, the paper investigates the creep buckling behavior of viscoelastic laminated plates and laminated circular cylindrical shells. The analysis and elaboration of both instantaneous elastic critic load and durable critic load are emphasized. The buckling load in phase domain is obtained from governing equations by applying Laplace transform, and the instantaneous elastic critic load and durable critic load are determined according to the extreme value theorem for inverse Laplace transform. It is shown that viscoelastic approach and quasi-elastic approach yield identical solutions for these two types of critic load respectively. A transverse disturbance model is developed to give the same mechanics significance of durable critic load as that of elastic critic load. Two types of critic loads of boron/epoxy composite laminated plates and circular cylindrical shells are discussed in detail individually, and the influencing factors to induce creep buckling are revealed by examining the viscoelasticity incorporated in transverse shear deformation and in-plane flexibility.
Free flexural radial vibrations of a thin circular cylindrical shell bearing added mass
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Seregin Sergey Valer’evich
2014-12-01
Full Text Available The author comes up with a refined mathematical model contemplating that added mass facilitates interaction between coupled flexural and radial vibrations in the linear setting. The author has identified a higher splitting of the flexural frequency spectrum due to the presence of the added mass and the wave generation parameters that characterize the relative length and thickness of the shell. Within the framework of the shallow-shell theory, the influence of the small concentrated mass onto natural dynamic properties of the shell is exposed to research. The refined mathematical model was employed to identify that the added mass binds the coupled flexural shape of the circular cylindrical shell and facilitates interaction between low-frequency flexural vibrations and high-frequency radial vibrations. Moreover, radial vibrations act as a supplementary inertial link between coupled flexural shapes. Due to the availability of the exciting load, non-resonant areas, identified through the application of the traditional mathematical model, can be resonant in essence. The findings of this research must be considered in the course of the assessment of the dynamic strength of any shell structures designed. This refined finite-dimensional model, capable of recognizing radial vibrations, has generated the results that comply with numerical analyses and experimental data both quantitatively and qualitatively. Therefore, dynamic problems that have already been resolved may need refinement.
Finite element analysis of cylindrical shells with circular and elliptical holes
International Nuclear Information System (INIS)
A finite element solution to the problem of stress distribution in cylindrical shells with circular and elliptical holes is given in the present paper. Quadrilateral and triangular curved finite elements are used in the analysis. The elements of a new class, based on simple independent generalized strain functions insofar as this is allowed by the compatibility equations. The elements also satisfy exactly the requirements of strain-free-rigid body displacements and uses only the external open-quotes geometricclose quotes nodal degrees of freedom to avoid the difficulties associated with unnecessary internal degree of freedom. A rectangular curved element was first developed and applied to the analysis of the familiar pinched cylinder and barrel vault problems Ashwell and Sabir. The results converge rapidly for displacements as well as for stresses. Further tests were carried out to investigate the ability of this element in predicting the high stresses in the neighborhood of applied concentrated loads Sabir and Ashwell. The loads considered were either radial or axial forces as well as moments about tangents to the circular cross section. The results obtained were not only in agreement with those of Forsberg and Flagge but when plotted for the complex parameters defining proportions of the shell and flexibility as suggested by Calladine, their general forms corresponded closely with theoretical predications. In the present paper we first develop strain based quadrilateral and triangular elements and apply them to the solution of the problem of stress concentrations in the neighborhood of small and large circular and elliptical holes when the cylinders are subjected to a uniform axial tension. These results are compared with analytical solutions based on shallow sheel approximations and show that the use of these strain based elements obviates the need for using an inordinately large number of elements
Directory of Open Access Journals (Sweden)
Dong Tang
2016-01-01
Full Text Available An analytical procedure for free vibration analysis of circular cylindrical shells with arbitrary boundary conditions is developed with the employment of the method of reverberation-ray matrix. Based on the Flügge thin shell theory, the equations of motion are solved and exact solutions of the traveling wave form along the axial direction and the standing wave form along the circumferential direction are obtained. With such a unidirectional traveling wave form solution, the method of reverberation-ray matrix is introduced to derive a unified and compact form of equation for natural frequencies of circular cylindrical shells with arbitrary boundary conditions. The exact frequency parameters obtained in this paper are validated by comparing with those given by other researchers. The effects of the elastic restraints on the frequency parameters are examined in detail and some novel and useful conclusions are achieved.
Bich, Dao Huy; Xuan Nguyen, Nguyen
2012-12-01
In the present work, the study of the nonlinear vibration of a functionally graded cylindrical shell subjected to axial and transverse mechanical loads is presented. Material properties are graded in the thickness direction of the shell according to a simple power law distribution in terms of volume fractions of the material constituents. Governing equations are derived using improved Donnell shell theory ignoring the shallowness of cylindrical shells and kinematic nonlinearity is taken into consideration. One-term approximate solution is assumed to satisfy simply supported boundary conditions. The Galerkin method, the Volmir's assumption and fourth-order Runge-Kutta method are used for dynamical analysis of shells to give explicit expressions of natural frequencies, nonlinear frequency-amplitude relation and nonlinear dynamic responses. Numerical results show the effects of characteristics of functionally graded materials, pre-loaded axial compression and dimensional ratios on the dynamical behavior of shells. The proposed results are validated by comparing with those in the literature.
Liu, Y. Z.; Hao, Y. X.; Zhang, W.; Chen, J.; Li, S. B.
2015-07-01
The nonlinear vibration of a simply supported FGM cylindrical shell with small initial geometric imperfection under complex loads is studied. The effects of radial harmonic excitation, compressive in-plane force combined with supersonic aerodynamic and thermal loads are considered. The small initial geometric imperfection of the cylindrical shell is characterized in the form of the sine-type trigonometric functions. The effective material properties of this FGM cylindrical shell are graded in the radial direction according to a simple power law in terms of the volume fractions. Based on Reddy's third-order shear deformation theory, von Karman-type nonlinear kinematics and Hamilton's principle, the nonlinear partial differential equation that controls the shell dynamics is derived. Both axial symmetric and driven modes of the cylindrical shell deflection pattern are included. Furthermore, the equations of motion can be reduced into a set of coupled nonlinear ordinary differential equations by applying Galerkin's method. In the study of the nonlinear dynamics responses of small initial geometric imperfect FGM cylindrical shell under complex loads, the 4th order Runge-Kutta method is used to obtain time history, phase portraits, bifurcation diagrams and Poincare maps with different parameters. The effects of external loads, geometric imperfections and volume fractions on the nonlinear dynamics of the system are discussed.
Khalifa, Ahmed Mousa
2011-11-01
The combination of Flügge's shell theory, the transfer matrix approach and the Romberg integration method are used to investigate the free vibration behaviour of stepped orthotropic cylindrical shells. The hoop step on the shell surface is described by a reduced thickness over part of its circumference. Modal displacements of the shell can be described by trigonometric functions and Fourier's approach is used to separate the variables. The vibration equations of the shell are reduced to eight first-order differential equations in the circumferential coordinate, and by using the transfer matrix of the shell, these equations can be written in a matrix differential equation. The transfer matrix is derived from the non-linear differential equations of the cylindrical shells by introducing the trigonometric functions in the longitudinal direction and applying the numerical integration in the circumferential direction. The proposed model is used to get the vibration frequencies and the corresponding mode shapes for symmetrical and antisymmetrical type-modes. Computed results indicate the sensitivity of the frequency parameters and the bending deformations to the geometry of stepped shell, and also to the axial and circumferential rigidities of the shell.
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Based on the linear theories of thin cylindrical shells and viscoelastic materi-als, a governing equation describing vibration of a sandwich circular cylindrical shell with a viscoelastic core under harmonic excitation is derived. The equation can be written as a matrix differential equation of the first order, and is obtained by considering the energy dissipation due to the shear deformation of the viscoelastic core layer and the interaction between all layers. A new matrix method for solving the governing equation is then pre-sented with an extended homogeneous capacity precision integration approach. Having obtained these, vibration characteristics and damping effect of the sandwich cylindrical shell can be studied. The method differs from a recently published work as the state vector in the governing equation is composed of displacements and internal forces of the sandwich shell rather than displacements and their derivatives. So the present method can be applied to solve dynamic problems of the kind of sandwich shells with various boundary, conditions and partially constrained layer damping. Numerical examples show that the proposed approach is effective and reliable compared with the existing methods.
Pellicano, F.; Amabili, M.
2006-05-01
In the present paper the dynamic stability of circular cylindrical shells subjected to static and dynamic axial loads is investigated. Both Donnell's nonlinear shallow shell and Sanders-Koiter shell theories have been applied to model finite-amplitude static and dynamic deformations. Results are compared in order to evaluate the accuracy of these theories in predicting instability onset and post-critical nonlinear response. The effect of a contained fluid on the stability and the post-critical behaviour is analyzed in detail. Geometric imperfections are considered and their influence on the dynamic instability and post-critical behaviour is investigated. Chaotic dynamics of pre-compressed shells is investigated by means of nonlinear time-series techniques, extracting correlation dimension and Lyapunov exponents.
International Nuclear Information System (INIS)
Cylindrical shells are utilized as structural elements of nuclear power plans, heat exchangers or pressure vessels, which are operated under elevated temperature. Creep buckling is one of the failure modes of structures at elevated temperature. In some experiments conducted by other authors, axially compressive cylindrical shells with a large ratio of radius to thickness were observed to buckle with circumferential waves. We reported that the circumferential weaves occur due to bifurcation buckling. But, the citrical time and the minimum loading for bifurcation buckling obtained from calculations of finite element analyses are not very good agreement with those of the experiments. One of the reasons for the disagreement is considered to be that the creep constitutive equations employed in many previous analyses represent steady creep. The creep phenomena usually have primary creep period, steady creep one and tertiary creep one. A creep strain-time relation through the three periods can be simulated by using a constitutive equation based on creep damage mechanics. In the present paper, we analyze bifurcation creep buckling of circular cylindrical shells subjected to axial compression by the use of the finite element method taking account of the creep damage mechanics of Kachanov-Rabotnov. (author)
DEFF Research Database (Denmark)
Rahmani, Omid; Khalili, S.M.R.; Thomsen, Ole Thybo
2012-01-01
A new model based on the high order sandwich panel theory is proposed to study the effect of external loads on the free vibration of circular cylindrical composite sandwich shells with transversely compliant core, including also the calculation of the buckling loads. In the present model, in...... contrast to most of the available sandwich plate and shell theories, no prior assumptions are made with respect to the displacement field in the core. Herein the displacement and the stress fields of the core material are determined through a 3D elasticity solution. The performance of the present theory is......, which is based on a 3D elasticity solution for the core material, can be used as a benchmark in future studies of the free vibration and buckling of circular cylindrical composite sandwich shells with a transversely compliant core....
Free flexural radial vibrations of a thin circular cylindrical shell bearing added mass
Seregin Sergey Valer’evich
2014-01-01
The author comes up with a refined mathematical model contemplating that added mass facilitates interaction between coupled flexural and radial vibrations in the linear setting. The author has identified a higher splitting of the flexural frequency spectrum due to the presence of the added mass and the wave generation parameters that characterize the relative length and thickness of the shell. Within the framework of the shallow-shell theory, the influence of the small concentrated mass onto ...
International Nuclear Information System (INIS)
A semi-analytical approach eccentrically stiffened functionally graded circular cylindrical shells surrounded by an elastic medium subjected to external pressure is presented. The elastic medium is assumed as two-parameter elastic foundation model proposed by Pasternak. Based on the classical thin shell theory with the geometrical nonlinearity in von Karman-Donnell sense, the smeared stiffeners technique and Galerkin method, this paper deals the nonlinear dynamic problem. The approximate three-term solution of deflection shape is chosen and the frequency-amplitude relation of nonlinear vibration is obtained in explicit form. The nonlinear dynamic responses are analyzed by using fourth order Runge-Kutta method and the nonlinear dynamic buckling behavior of stiffened functionally graded shells is investigated according to Budiansky-Roth criterion. Results are given to evaluate effects of stiffener, elastic foundation and input factors on the frequency-amplitude curves, natural frequencies, nonlinear responses and nonlinear dynamic buckling loads of functionally graded cylindrical shells. (authors)
Amabili, M.; Sarkar, A.; Païdoussis, M. P.
2006-03-01
The geometric nonlinear response of a water-filled, simply supported circular cylindrical shell to harmonic excitation in the spectral neighbourhood of the fundamental natural frequency is investigated. The response is investigated for a fixed excitation frequency by using the excitation amplitude as bifurcation parameter for a wide range of variation. Bifurcation diagrams of Poincaré maps obtained from direct time integration and calculation of the Lyapunov exponents and Lyapunov dimension have been used to study the system. By increasing the excitation amplitude, the response undergoes (i) a period-doubling bifurcation, (ii) subharmonic response, (iii) quasi-periodic response and (iv) chaotic behaviour with up to 16 positive Lyapunov exponents (hyperchaos). The model is based on Donnell's nonlinear shallow-shell theory, and the reference solution is obtained by the Galerkin method. The proper orthogonal decomposition (POD) method is used to extract proper orthogonal modes that describe the system behaviour from time-series response data. These time-series have been obtained via the conventional Galerkin approach (using normal modes as a projection basis) with an accurate model involving 16 degrees of freedom (dofs), validated in previous studies. The POD method, in conjunction with the Galerkin approach, permits to build a lower-dimensional model as compared to those obtainable via the conventional Galerkin approach. Periodic and quasi-periodic response around the fundamental resonance for fixed excitation amplitude, can be very successfully simulated with a 3-dof reduced-order model. However, in the case of large variation of the excitation, even a 5-dof reduced-order model is not fully accurate. Results show that the POD methodology is not as "robust" as the Galerkin method.
Nemeth, Michael P.; Schultz, Marc R.
2012-01-01
A detailed exact solution is presented for laminated-composite circular cylinders with general wall construction and that undergo axisymmetric deformations. The overall solution is formulated in a general, systematic way and is based on the solution of a single fourth-order, nonhomogeneous ordinary differential equation with constant coefficients in which the radial displacement is the dependent variable. Moreover, the effects of general anisotropy are included and positive-definiteness of the strain energy is used to define uniquely the form of the basis functions spanning the solution space of the ordinary differential equation. Loading conditions are considered that include axisymmetric edge loads, surface tractions, and temperature fields. Likewise, all possible axisymmetric boundary conditions are considered. Results are presented for five examples that demonstrate a wide range of behavior for specially orthotropic and fully anisotropic cylinders.
International Nuclear Information System (INIS)
Several experimental investigations indicate the necessity to take into account the material anisotropy as well as different creep strengths in uniaxial tension and compression (CSD-effect) in descriptions of deformation behaviour of such materials which are used in the design of pressure vessels and pipings of the chemical industry and power plants. Within the frame of the representation theory of tensor functions a suitable constitutive equation is proposed and used in connection with the Norton-Bailey power creep law for the numerical analysis of the steady state creep of thin-walled circular cylindrical shells, subjected to an axially symmetric load. Thereby the investigations are not performed with the assumption of a sandwich shell but start from an actual solid wall shell whose creep deformations are analysed by using the extended Newton-method combined with the method of finite differences. As numerical example a circular cylindrical shell with open ends subjected to internal pressure is investigated. Thereby the shell is assumed to be clamped at both ends in supports that are free to move in the axial direction. The results of calculation indicate that material anisotropy as well as the CSD-effect have great influence on the components of displacement and bending moment. (orig.)
Torsion of Elliptical Composite Cylindrical Shells
Haynie, Waddy
2007-01-01
The response of elliptical composite cylindrical shells under torsion is studied. The torsional condition is developed by rotating one end of the cylinder relative to the other. Prebuckling, buckling, and postbuckling responses are examined, and material failure is considered. Four elliptical cross sections, defined by their aspect ratio, the ratio of minor to major radii, are considered: 1.00 (circular), 0.85, 0.70, and 0.55. Two overall cylinder sizes are studied; a small size with a radius...
Plastic buckling of cylindrical shells
International Nuclear Information System (INIS)
Cylindrical shells exhibit buckling under axial loads at stresses much less than the respective theoretical critical stresses. This is due primarily to the presence of geometrical imperfections even though such imperfections could be very small (e.g., comparable to thickness). Under internal pressure, the shell regains some of its buckling strength. For a relatively large radius-to-thickness ratio and low internal pressure, the effect can be reasonably estimated by an elastic analysis. However, for low radius-to-thickness ratios and greater pressures, the elastic-plastic collapse controls the failure load. in order to quantify the elastic-plastic buckling capacity of cylindrical shells, an analysis program was carried out by use of the computer code BOSOR5 developed by Bushnell of Lockheed Missiles and Space Company. The analysis was performed for various radius-to-thickness ratios and imperfection amplitudes. The purpose of the analytical program was to compute the buckling strength of underground cylindrical tanks, that are used for storage of nuclear wastes, for realistic geometric imperfections and internal pressure loads. This paper presents the results of the elastic-plastic analyses and compares them with other available information for various pressure loads
Vibration of cylindrical shells of bimodulus composite materials
Bert, C. W.; Kumar, M.
1982-03-01
A theory is formulated for the small amplitude free vibration of thick, circular cylindrical shells laminated of bimodulus composite materials, which have different elastic properties depending upon whether the fiber-direction strain is tensile or compressive. The theory used is the dynamic, shear deformable (moderately thick shell) analog of the Sanders best first approximation thin shell theory. By means of tracers, the analysis can be reduced to that of various simpler shell theories, namely Love's first approximation, and Donnell's shallow shell theory. As an example of the application of the theory, a closed form solution is presented for a freely supported panel or complete shell. To validate the analysis, numerical results are compared with existing results for various special cases. Also, the effects of the various shell theories, thickness shear flexibility, and bimodulus action are investigated.
Omnidirectional, circularly polarized, cylindrical microstrip antenna
Stanton, Philip H. (Inventor)
1985-01-01
A microstrip cylindrical antenna comprised of two concentric subelements on a ground cylinder, a vertically polarized (E-field parallel to the axis of the antenna cylinder) subelement on the inside and a horizontally polarized (E-field perpendicular to the axis) subelement on the outside. The vertical subelement is a wraparound microstrip radiator. A Y-shaped microstrip patch configuration is used for the horizontally polarized radiator that is wrapped 1.5 times to provide radiating edges on opposite sides of the cylindrical antenna for improved azimuthal pattern uniformity. When these subelements are so fed that their far fields are equal in amplitude and phased 90.degree. from each other, a circularly polarized EM wave results. By stacking a plurality of like antenna elements on the ground cylinder, a linear phased array antenna is provided that can be beam steered to the desired elevation angle.
RESONANCE RADIATION OF SUBMERGED INFINITE CYLINDRICAL SHELL
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The resonance sound radiation from submerged infinite elastic cylindrical shell, excited by internal harmonic line force, is investigated. The shell radiation power is presented in terms of resonant modal radiation derived from resonance radiation theory (RRT). The resonance radiation formulae are derived from classical Rayleigh normal mode solution, which are useful for understanding the mechanism of sound radiation from submerged shells. As an example, numerical calculation of a thin steel cylindrical shell is done by using these two methods. It seems that the results of RRT solutions are in good agreement with that of Rayleigh normal mode solutions.
Multimode interaction in axially excited cylindrical shells
Silva F. M. A.; Rodrigues L.; Gonçalves P. B.; Del Prado Z. J. G. N
2014-01-01
Cylindrical shells exhibit a dense frequency spectrum, especially near the lowest frequency range. In addition, due to the circumferential symmetry, frequencies occur in pairs. So, in the vicinity of the lowest natural frequencies, several equal or nearly equal frequencies may occur, leading to a complex dynamic behavior. So, the aim of the present work is to investigate the dynamic behavior and stability of cylindrical shells under axial forcing with multiple equal or nearly equal natural fr...
Improvement of the axial buckling capability of elliptical cylindrical shells
Paschero, Maurizio
2008-01-01
A rather thorough and novel buckling analysis of an axially-loaded orthotropic circular cylindrical shell is formulated. The analysis assumes prebuckling rotations are negligible and uses a unique re-defining of the orthotropic material properties in terms of a so-called geometric mean isotropic (GMI) material. Closed-form expressions for the buckling stress in terms of cylinder geometry and orthotropic material properties are presented, the particular closed form depending on ...
Distributed neural signals on parabolic cylindrical shells
Hu, S. D.; Li, H.; Tzou, H. S.
2013-06-01
Parabolic cylindrical shells are commonly used as key components in communication antennas, space telescopes, solar collectors, etc. This study focuses on distributed modal neural sensing signals on a flexible simply-supported parabolic cylindrical shell panel. The parabolic cylindrical shell is fully laminated with a piezoelectric layer on its outer surface and the piezoelectric layer is segmented into infinitesimal elements (neurons) to investigate the microscopic distributed neural sensing signals. Since the dominant vibration component of the shell is usually the transverse oscillation, a new transverse mode shape function is defined. Two shell cases, i.e., the ratio of the meridian height to the half span distance of a parabola at 1:4 (shallow) and 1:1 (deep), are studied to reveal the curvature effect to the neural sensing signals. Studies suggest that the membrane signal component dominates for lower natural modes and the bending signal component dominates for higher natural modes. The meridional membrane and bending signal components are mostly concentrated on the high-curvature areas, while the longitudinal bending component is mostly concentrated on the relatively flat areas. The concentration behavior becomes more prominent as the parabolic cylindrical shell deepens, primarily resulting from the enhanced membrane effect due to the increased curvature.
OPTIMAL THICKNESS OF A CYLINDRICAL SHELL
Directory of Open Access Journals (Sweden)
Paul Ziemann
2015-01-01
Full Text Available In this paper an optimization problem for a cylindrical shell is discussed. The aim is to look for an optimal thickness of a shell to minimize the deformation under an applied external force. As a side condition, the volume of the shell has to stay constant during the optimization process. The deflection is calculated using an approach from shell theory. The resulting control-to-state operator is investigated analytically and a corresponding optimal control problem is formulated. Moreover, necessary conditions for an optimal solution are stated and numerical solutions are presented for different examples.
Indentation of Ellipsoidal and Cylindrical Elastic Shells
Vella, Dominic
2012-10-01
Thin shells are found in nature at scales ranging from viruses to hens\\' eggs; the stiffness of such shells is essential for their function. We present the results of numerical simulations and theoretical analyses for the indentation of ellipsoidal and cylindrical elastic shells, considering both pressurized and unpressurized shells. We provide a theoretical foundation for the experimental findings of Lazarus etal. [following paper, Phys. Rev. Lett. 109, 144301 (2012)PRLTAO0031-9007] and for previous work inferring the turgor pressure of bacteria from measurements of their indentation stiffness; we also identify a new regime at large indentation. We show that the indentation stiffness of convex shells is dominated by either the mean or Gaussian curvature of the shell depending on the pressurization and indentation depth. Our results reveal how geometry rules the rigidity of shells. © 2012 American Physical Society.
Research on cylindrical shell vibration reduction systems
Institute of Scientific and Technical Information of China (English)
XING Xiao-liang; WANG Min-qing
2008-01-01
Longitudinal and horizontal vibration must both be reduced in an effective vibration isolation system. We present a cylindrical shell vibration isolator as a dynamic system composed of four springs and dampers. Vibration is directly produced by the motion of machinery, and more is subsequently generated by harmonic frequencies within their structure. To test the effectiveness of our isolator, we first determined equations for the transmission of vibration from the machine to its cylindrical shell. Damping effects produced by the vibration parameters of our system are then analyzed.
Free Vibration of Partially Supported Cylindrical Shells
Mirza, S.; Y. Alizadeh
1995-01-01
The effects of detached base length on the natural frequencies and modal shapes of cylindrical shell structures were investigated in this work. Some of the important applications for this type of problem can be found in the cracked fan and rotor blades that can be idealized as partially supported shells with varying unsupported lengths. A finite element model based on small deflection linear theory was developed to obtain numerical solutions for this class of problems. The numerical results w...
SPSM and its application in cylindrical shells
Nie, Wu; Zhou, Su-Lian; Peng, Hui
2008-03-01
In naval architectures, the structure of prismatic shell is used widely. But there is no suitable method to analyze this kind of structure. Stiffened prismatic shell method (SPSM) presented in this paper, is one of the harmonic semi-analytic methods. Theoretically, strong stiffened structure can be analyzed economically and accurately. SPSM is based on the analytical solution of the governing differential equations for orthotropic cylindrical shells. In these differential equations, the torsional stiffness, bending stiffness and the exact position of each stiffener are taken into account with the Heaviside singular function. An algorithm is introduced, in which the actions of stiffeners on shells are replaced by external loads at each stiffener position. Stiffened shells can be computed as non-stiffened shells. Eventually, the displacement solution of the equations is acquired by the introduction of Green function. The stresses in a corrugated transverse bulkhead without pier base of an oil tanker are computed by using SPSM.
Stochastic Analysis of Cylindrical Shell
Directory of Open Access Journals (Sweden)
Grzywiński Maksym
2014-06-01
Full Text Available The paper deals with some chosen aspects of stochastic structural analysis and its application in the engineering practice. The main aim of the study is to apply the generalized stochastic perturbation techniques based on classical Taylor expansion with a single random variable for solution of stochastic problems in structural mechanics. The study is illustrated by numerical results concerning an industrial thin shell structure modeled as a 3-D structure.
Vibrations of cantilevered shallow cylindrical shells of rectangular planform
Leissa, A. W.; Lee, J. K.; Wang, A. J.
1981-10-01
A cantilevered, shallow shell of circular cylindrical curvature and rectangular planform exhibits free vibration behavior which differs considerably from that of a cantilevered beam or of a flat plate. Some numerical results can be found for the problem in the previously published literature, mainly obtained by using various finite element methods. The present paper is the first definitive study of the problem, presenting accurate non-dimensional frequency parameters for wide ranges of aspect ratio, shallowness ratio and thickness ratio. The analysis is based upon shallow shell theory. Numerical results are obtained by using the Ritz method, with algebraic polynomial trial functions for the displacements. Convergence is investigated, with attention being given both to the number of terms taken for each co-ordinate direction and for each of the three components of displacement. Accuracy of the results is also established by comparison with finite element results for shallow shells and with other accurate flat plate solutions.
Vibrations of cantilevered shallow cylindrical shells of rectangular planform
Leissa, A. W.; Lee, J. K.; Wang, A. J.
1981-01-01
A cantilevered, shallow shell of circular cylindrical curvature and rectangular planform exhibits free vibration behavior which differs considerably from that of a cantilevered beam or of a flat plate. Some numerical results can be found for the problem in the previously published literature, mainly obtained by using various finite element methods. The present paper is the first definitive study of the problem, presenting accurate non-dimensional frequency parameters for wide ranges of aspect ratio, shallowness ratio and thickness ratio. The analysis is based upon shallow shell theory. Numerical results are obtained by using the Ritz method, with algebraic polynomial trial functions for the displacements. Convergence is investigated, with attention being given both to the number of terms taken for each co-ordinate direction and for each of the three components of displacement. Accuracy of the results is also established by comparison with finite element results for shallow shells and with other accurate flat plate solutions.
Multimode interaction in axially excited cylindrical shells
Directory of Open Access Journals (Sweden)
Silva F. M. A.
2014-01-01
Full Text Available Cylindrical shells exhibit a dense frequency spectrum, especially near the lowest frequency range. In addition, due to the circumferential symmetry, frequencies occur in pairs. So, in the vicinity of the lowest natural frequencies, several equal or nearly equal frequencies may occur, leading to a complex dynamic behavior. So, the aim of the present work is to investigate the dynamic behavior and stability of cylindrical shells under axial forcing with multiple equal or nearly equal natural frequencies. The shell is modelled using the Donnell nonlinear shallow shell theory and the discretized equations of motion are obtained by applying the Galerkin method. For this, a modal solution that takes into account the modal interaction among the relevant modes and the influence of their companion modes (modes with rotational symmetry, which satisfies the boundary and continuity conditions of the shell, is derived. Special attention is given to the 1:1:1:1 internal resonance (four interacting modes. Solving numerically the governing equations of motion and using several tools of nonlinear dynamics, a detailed parametric analysis is conducted to clarify the influence of the internal resonances on the bifurcations, stability boundaries, nonlinear vibration modes and basins of attraction of the structure.
Realization of cylindrical submicron shell arrays by diffraction-introduced photolithography
International Nuclear Information System (INIS)
In this paper, we present an approach for the fabrication of cylindrical shell arrays with shell thickness of a few hundred nanometers. This approach is based on introducing diffraction into conventional ultraviolet photolithography, which is realized by deliberately leaving a gap between mask patterns and photoresist surfaces. The cylindrical shells generated from this method have external diameters from 1.5 to 4.5 µm, internal diameters from 0.5 to 3.5 µm, and heights of 10–15 µm at most, while side lengths of original square mask patterns (or diameters of circular mask patterns) are within 2–5 µm. Experimental results indicate that these cylindrical submicron shell arrays are reproducible and uniform in morphologies and dimensions. The optical principle of the fabrication is simulated based on Fresnel diffraction theory. Moreover, the cylindrical submicron shell arrays fabricated herein may find applications in bio-chemical and micro/nano-fluidic fields
Free Vibration of Partially Supported Cylindrical Shells
Directory of Open Access Journals (Sweden)
S. Mirza
1995-01-01
Full Text Available The effects of detached base length on the natural frequencies and modal shapes of cylindrical shell structures were investigated in this work. Some of the important applications for this type of problem can be found in the cracked fan and rotor blades that can be idealized as partially supported shells with varying unsupported lengths. A finite element model based on small deflection linear theory was developed to obtain numerical solutions for this class of problems. The numerical results were generated for shallow shells and some of the degenerate cases are compared with other results available in the literature. The computations presented here involve a wide range of variables: material properties, aspect ratios, support conditions, and radius to base ratio.
Institute of Scientific and Technical Information of China (English)
王延庆; 梁力; 郭星辉; 杨坤
2012-01-01
A composite circular cylindrical shell made from different materials is investigated. Based on Donnell＇s shallow shell theory and classical laminated shell theory, nonlinear vibrating equation is derived, in which the effects of dynamic Young＇s modulus and geometric large-amplitude are considered. Galerkin method is used to disperse the vibrating equation. The nonlinear vibrating responses of the system with the participation of two neighboring axial modes are solved by applying the multidimensional L-P method. And complex frequency-response curves indicating internal resonance are obtained, showing that the energy is transferred between the two modes which affect each other, and there is 1：1 internal resonance phenomenon in the system. Result of multiple scales method is compared with that of multidimensional L-P method, and the same conclusion is drawn.%以不同材料构成的复合材料圆柱壳作为研究模型，考虑几何非线性，动态弹性模量等因素，根据Dormell’s简化壳理论及经典层合壳理论建立其非线性振动方程。采用Galerkin方法对振动方程进行离散化，应用多元L-P法求解了系统包含两个相邻轴向模态的非线性振动响应，得到了反映复杂内共振的幅频特性曲线，表明能量在两个模态之间相互传递，彼此影响牵制，系统存在1：1内共振现象。最后利用多尺度法与多元L-P法所得结果进行比较，得到了相同的结论。
Thermalization Calculations in a Cylindrical Shell
International Nuclear Information System (INIS)
An approximate, semi-analytical procedure for determining the distribution and energy spectrum of the thermal and epithermal neutron flux in a weakly neutron capturing, cylindrical shell medium is considered. The shell medium is taken to represent the moderator surrounding a fuel rod in a thermal reactor. The basis for calculating the flux in most of the moderator is the energy-dependent diffusion equation. Transient corrections to the diffusion approximation are added near the medium boundaries. The effects of adjoining media are taken into account through the boundary conditions imposed on the diffusion and transient fluxes. At the inner boundary these effects are calculated by collision probability methods. Activation fluxes are derived from the calculated neutron flux distributions and compared with measurements made in the D2O moderator surrounding a uranium metal rod in the ZEEP reactor. (author)
Mercan, Kadir; Demir, Çiğdem; Civalek, Ömer
2016-01-01
In the present manuscript, free vibration response of circular cylindrical shells with functionally graded material (FGM) is investigated. The method of discrete singular convolution (DSC) is used for numerical solution of the related governing equation of motion of FGM cylindrical shell. The constitutive relations are based on the Love's first approximation shell theory. The material properties are graded in the thickness direction according to a volume fraction power law indexes. Frequency values are calculated for different types of boundary conditions, material and geometric parameters. In general, close agreement between the obtained results and those of other researchers has been found.
Directory of Open Access Journals (Sweden)
Mercan Kadir
2016-01-01
Full Text Available In the present manuscript, free vibration response of circular cylindrical shells with functionally graded material (FGM is investigated. The method of discrete singular convolution (DSC is used for numerical solution of the related governing equation of motion of FGM cylindrical shell. The constitutive relations are based on the Love’s first approximation shell theory. The material properties are graded in the thickness direction according to a volume fraction power law indexes. Frequency values are calculated for different types of boundary conditions, material and geometric parameters. In general, close agreement between the obtained results and those of other researchers has been found.
Buckling of un-stiffened cylindrical shell under non-uniform axial conpressive stress
Institute of Scientific and Technical Information of China (English)
宋昌永
2002-01-01
This paper provides a review of recent research advances and trends in the area of stability of un-stiffened circular cylindrical shells subjected to general non-uniform axial compressive stresses. Only the more important and interesting aspects of the research, judged from a personal viewpoint, are discussed. They can be crudely classified into four categories: (1) shells subjected to non-uniform loads; (2) shells on discrete supports; (3) shells with intended cutouts/holes; and (4) shells with non-uniform settlements.
Study on 1∶ 1 internal resonance of thin laminated circular cylindrical shells%层合薄壁圆柱壳1:1内共振研究
Institute of Scientific and Technical Information of China (English)
王延庆; 梁力; 郭星辉; 楼玲娜
2011-01-01
针对一端固定,一端自由的层合薄壁圆柱壳模型,根据Donnell's非线性简化壳理论建立其非线性振动方程.采用Galerkin方法对非线性振动方程进行离散化,应用平均法对系统包含两个相邻轴向模态的非线性振动响应进行了解析分析,与数值模拟进行了比较,并得到了不同参数对层合薄壁圆柱壳复杂的振动响应的影响.结果表明,1)由于所选的两个相邻轴向模态频率相距较近,能量在两个模态之间相互传递,系统存在1∶1内共振现象；2)系统复杂的振动响应受激振力大小的影响比较大,而对于阻尼不敏感.%A cantilever thin laminated circular cylindrical shell was investigated. Based on Donnell's nonlinear shallow shell theory, nonlinear wave equation of the system was derived, in which the effects of dynamic Young's modulus, damping and geometric large-amplitude were considered. Galerkin method was used to disperse the wave equation. Applying averaging method, the nonlinear response of the system was solved with two neighboring axial modes participation, and the results obtained were compared with those gained by numerical method. The effects of different parameters on the complex dynamic response were also investigated. The results show that; due to the frequencies of the two modes selected are very close, there exists 1: 1 internal resonance in the system; the complex vibration response of the system is affected by exciting force evidendy, but it is not very sensitive to damping.
Forced Vibration Analysis for a FGPM Cylindrical Shell
Directory of Open Access Journals (Sweden)
Hong-Liang Dai
2013-01-01
Full Text Available This article presents an analytical study for forced vibration of a cylindrical shell which is composed of a functionally graded piezoelectric material (FGPM. The cylindrical shell is assumed to have two-constituent material distributions through the thickness of the structure, and material properties of the cylindrical shell are assumed to vary according to a power-law distribution in terms of the volume fractions for constituent materials, the exact solution for the forced vibration problem is presented. Numerical results are presented to show the effect of electric excitation, thermal load, mechanical load and volume exponent on the static and force vibration of the FGPM cylindrical shell. The goal of this investigation is to optimize the FGPM cylindrical shell in engineering, also the present solution can be used in the forced vibration analysis of cylindrical smart elements.
A circumferential crack in a cylindrical shell under tension.
Duncan-Fama, M. E.; Sanders, J. L., Jr.
1972-01-01
A closed cylindrical shell under uniform internal pressure has a slit around a portion of its circumference. Linear shallow shell theory predicts inverse square-root-type singularities in certain of the stresses at the crack tips. This paper reports the computed strength of these singularities for different values of a dimensionless parameter based on crack length, shell radius and shell thickness.
Plasmon modes of circular cylindrical double-layer graphene.
Zhao, Tao; Hu, Min; Zhong, Renbin; Chen, Xiaoxing; Zhang, Ping; Gong, Sen; Zhang, Chao; Liu, Shenggang
2016-09-01
In this paper, a theoretical investigation on plasmon modes in a circular cylindrical double-layer graphene structure is presented. Due to the interlayer electromagnetic interaction, there exist two branches of plasmon modes, the optical plasmon mode and the acoustic plasmon mode. The characteristics of these two modes, such as mode pattern, effective mode index and propagation loss, are analyzed. The modal behaviors can be effectively tuned by changing the distance between two graphene layers, the chemical potential of graphene and the permittivity of interlayer dielectric. Importantly, the breakup of tradeoff between mode confinement and propagation loss is discovered in the distance-dependent modal behavior, which originates from the unique dispersion properties of a double-layer graphene system. As a consequence, both strong mode confinement and longer propagation length can be achieved. Our results may provide good opportunities for developing applications based on graphene plasmonics in circular cylindrical structure. PMID:27607651
NONLINEAR FARADAY WAVES IN A PARAMETRICALLY EXCITED CIRCULAR CYLINDRICAL CONTAINER
Institute of Scientific and Technical Information of China (English)
菅永军; 鄂学全; 柏威
2003-01-01
In the cylindrical coordinate system, a singular perturbation theory of multiple-scale asymptotic expansions was developed to study single standing water wave mode bysolving potential equations of water waves in a rigid circular cylinder, which is subject to avertical oscillation. It is assumed that the fluid in the circular cylindrical vessel is inviscid ,incompressible and the motion is irrotational, a nonlinear amplitude equation with cubicand vertically excited terms of the vessel was derived by expansion of two-time scales withoutconsidering the effect of surface tension. It is shown by numerical computation that differentfree surface standing wave patterns will be formed in different excited frequencies andamplitudes. The contours of free surface waves are agreed well with the experimental resultswhich were carried out several years ago.
On the accuracy of the asymptotic theory for cylindrical shells
DEFF Research Database (Denmark)
Niordson, Frithiof; Niordson, Christian
1999-01-01
We study the accuracy of the lowest-order bending theory of shells, derived from an asymptotic expansion of the three-dimensional theory of elasticity, by comparing the results of this shell theory for a cylindrical shell with clamped ends with the results of a solution to the three......-dimensional problem. The results are also compared with those of some commonly used engineering shell theories....
Gravitational collapse of a cylindrical null shell in vacuum
Directory of Open Access Journals (Sweden)
S. Khakshournia
2008-03-01
Full Text Available Barrabès-Israel null shell formalism is used to study the gravitational collapse of a thin cylindrical null shell in vacuum. In general the lightlike matter shell whose history coincides with a null hypersurface is characterized by a surface energy density. In addition, a gravitational impulsive wave is present on this null hypersurface whose generators admit both the shear and expansion. In the case of imposing the cylindrical flatness the surface energy-momentum tensor of the matter shell on the null hypersurface vanishes and the null hyper- surface is just the history of the gravitational wave .
The covariant electromagnetic Casimir effect for real conducting cylindrical shells
International Nuclear Information System (INIS)
Using covariant quantization of the electromagnetic field, the Casimir force per unit area experienced by a long conducting cylindrical shell, under both Dirichlet and Neumann boundary conditions, is calculated. The renormalization procedure is based on the plasma cut-off frequency for real conductors. The real case of a gold (silver) cylindrical shell is considered and the corresponding electromagnetic Casimir pressure is computed. It is discussed that the Dirichlet and Neumann problems should be considered separately without adding their corresponding results.
NONLINEAR THEORY OF DYNAMIC STABILITY FOR LAMINATED COMPOSITE CYLINDRICAL SHELLS
Institute of Scientific and Technical Information of China (English)
周承倜; 王列东
2001-01-01
Hamilton Principle was uaed to derive the general governing equations of nonlinear dynamic stability for laminated cylindrical shells in which, factors of nonlinear large deflection, transverse shear and longitudinal inertia force were concluded. Equations were solved by variational method. Analysis reveals that under the action of dynamic load,laminated cylindrical shells will fall into a state of parametric resonance and enter into the dynamic unstable region that causes dynamic instability of shells. Laminated shells of three typical composites were computed: i.e. T300/5 208 graphite epoxy E-glass epoxy, and ARALL shells. Results show that all factors will induce important influence for dynamic stability of laminated shells. So, in research of dynamic stability for laminated shells, to consider these factors is important.
Gerhard, Craig Steven; Gurdal, Zafer; Kapania, Rakesh K.
1996-01-01
Layerwise finite element analyses of geodesically stiffened cylindrical shells are presented. The layerwise laminate theory of Reddy (LWTR) is developed and adapted to circular cylindrical shells. The Ritz variational method is used to develop an analytical approach for studying the buckling of simply supported geodesically stiffened shells with discrete stiffeners. This method utilizes a Lagrange multiplier technique to attach the stiffeners to the shell. The development of the layerwise shells couples a one-dimensional finite element through the thickness with a Navier solution that satisfies the boundary conditions. The buckling results from the Ritz discrete analytical method are compared with smeared buckling results and with NASA Testbed finite element results. The development of layerwise shell and beam finite elements is presented and these elements are used to perform the displacement field, stress, and first-ply failure analyses. The layerwise shell elements are used to model the shell skin and the layerwise beam elements are used to model the stiffeners. This arrangement allows the beam stiffeners to be assembled directly into the global stiffness matrix. A series of analytical studies are made to compare the response of geodesically stiffened shells as a function of loading, shell geometry, shell radii, shell laminate thickness, stiffener height, and geometric nonlinearity. Comparisons of the structural response of geodesically stiffened shells, axial and ring stiffened shells, and unstiffened shells are provided. In addition, interlaminar stress results near the stiffener intersection are presented. First-ply failure analyses for geodesically stiffened shells utilizing the Tsai-Wu failure criterion are presented for a few selected cases.
Dynamic stability of simply supported composite cylindrical shells under partial axial loading
Dey, Tanish; Ramachandra, L. S.
2015-09-01
The parametric vibration of a simply supported composite circular cylindrical shell under periodic partial edge loadings is discussed in this article. Donnell's nonlinear shallow shell theory considering first order shear deformation theory is used to model the shell. The applied partial edge loading is represented in terms of a Fourier series and stress distributions within the cylindrical shell are determined by prebuckling analysis. The governing equations of the dynamic instability of shells are derived in terms of displacements (u-v-w) and rotations (φx, φθ). Employing the Galerkin and Bolotin methods the dynamic instability regions are computed. Using the expression for the stress function derived in this paper, the pre-buckling stresses in the cylindrical shell due to partial loading can be calculated explicitly. Numerical results are presented to show the influence of radius-to-thickness ratio, different partial edge loading distributions and shear deformation on the dynamic instability regions. The linear and nonlinear responses in the stable and unstable regions are presented to bring out the characteristic features of the dynamic instability regions, such as the existence of beats, its dependence on forcing frequency and effect of nonlinearity on the response. The effect of dynamic load amplitude on the nonlinear response is also studied. It is found that for higher values of dynamic loading, the shell exhibits chaotic behavior.
PERFORATION OF PLASTIC SPHERICAL SHELLS UNDER IMPACT BY CYLINDRICAL PROJECTILES
Institute of Scientific and Technical Information of China (English)
NING Jian-guo; SONG Wei-dong
2006-01-01
The objective is to study the perforation of a plastic spherical shell impacted by a cylindrical projectile. First, the deformation modes of the shell were given by introducing an isometric transformation. Then, the perforation mechanism of the shell was analyzed and an analytical model was advanced. Based on Hamilton principle, the governing equation was obtained and solved using Runge-Kuta method. Finally, some important theoretical predictions were given to describe the perforation mechanism of the shell. The results will play an important role in understanding the perforation mechanism of spherical shells impacted by a projectile.
Reliability Analysis Of Thin-Walled Cylindrical Shells
Kala Zdeněk
2015-01-01
The subject of the article is the verification of the reliability of thin-walled rotationally symmetric cylindrical shells, using probabilistic approaches. Internal forces and stress of the shell are analysed assuming a membrane action. Material and geometric characteristics of the steel shell are considered as random variables. The reliability index is evaluated using the Latin Hypercube Sampling method. The results of the reliability analysis are derived in a general form, so that they may ...
Prediction of Vibrational Behavior of Grid-Stiffened Cylindrical Shells
Rahimi, G. H.; M. Hemmatnezhad; Ansari, R.
2014-01-01
A unified analytical approach is applied to investigate the vibrational behavior of grid-stiffened cylindrical shells with different boundary conditions. A smeared method is employed to superimpose the stiffness contribution of the stiffeners with those of shell in order to obtain the equivalent stiffness parameters of the whole panel. Theoretical formulation is established based on Sanders’ thin shell theory. The modal forms are assumed to have the axial dependency in the form of Fourier ser...
Vibration analysis of bi-layered FGM cylindrical shells
Energy Technology Data Exchange (ETDEWEB)
Arshad, Shahid Hussain; Sultana, Nazra; Iqbal, Zafar [University of Sargodha, Department of Mathematics, Sargodha, Punjab (Pakistan); Naeem, Muhammad Nawaz [G C University Faisalabad, Department of Mathematics, Faisalabad, Punjab (Pakistan); Shah, Abdul Ghafar [The Islamia University of Bahawalpur, Department of Mathematics, Bahawalpur, Punjab (Pakistan)
2011-03-15
In the present study, a vibration frequency analysis of a bi-layered cylindrical shell composed of two independent functionally graded layers is presented. The thickness of the shell layers is assumed to be equal and constant. Material properties of the constituents of bi-layered functionally graded cylindrical shell are assumed to vary smoothly and continuously through the thickness of the layers of the shell and are controlled by volume fraction power law distribution. The expressions for strain-displacement and curvature-displacement relationships are utilized from Love's first approximation linear thin shell theory. The versatile Rayleigh-Ritz approach is employed to formulate the frequency equations in the form of eigenvalue problem. Influence of material distribution in the two functionally graded layers of the cylindrical shells is investigated on shell natural frequencies for various shell parameters with simply supported end conditions. To check the validity, accuracy and efficiency of the present methodology, results obtained are compared with those available in the literature. (orig.)
The deformation of cylindrical shells subjected to radial loads
Madureira, M.L.R.; Fonseca, E.M.M.; Melo, F.J.M.Q. de
2010-01-01
Cylindrical shells have a simple geometry and application in pressure vessels and piping engineering. The development of calculation algorithms in structural project is impelled by a constant challenge in the search of more accurate and fast design tools in engineering. The objective of this work is to contribute with a simple and reliable numerical tool for the stress analysis of cylindrical vessels subjected to generalized forces. A hybrid formulation in the definition of forces...
Evolution of bulk strain solitons in cylindrical inhomogeneous shells
Energy Technology Data Exchange (ETDEWEB)
Shvartz, A., E-mail: andrew.shvartz@mail.ioffe.ru; Samsonov, A.; Dreiden, G.; Semenova, I. [Ioffe Institute, 26 Politekhnicheskaya, St Petersburg 194021 (Russian Federation)
2015-10-28
Bulk strain solitary waves in nonlinearly elastic thin-walled cylindrical shells with variable geometrical and physical parameters are studied, and equation for the longitudinal strain component with the variable coefficients is derived. A conservative finite difference scheme is proposed, and the results of numerical simulation of the strain soliton evolution in a shell with the abrupt variations of cross section and physical properties of the material are presented.
Strength Reliability Analysis of Stiffened Cylindrical Shells Considering Failure Correlation
Institute of Scientific and Technical Information of China (English)
Xu Bai; Liping Sun; Wei Qin; Yongkun Lv
2014-01-01
The stiffened cylindrical shell is commonly used for the pressure hull of submersibles and the legs of offshore platforms. There are various failure modes because of uncertainty with the structural size and material properties, uncertainty of the calculation model and machining errors. Correlations among failure modes must be considered with the structural reliability of stiffened cylindrical shells. However, the traditional method cannot consider the correlations effectively. The aim of this study is to present a method of reliability analysis for stiffened cylindrical shells which considers the correlations among failure modes. Firstly, the joint failure probability calculation formula of two related failure modes is derived through use of the 2D joint probability density function. Secondly, the full probability formula of the tandem structural system is given with consideration to the correlations among failure modes. At last, the accuracy of the system reliability calculation is verified through use of the Monte Carlo simulation. Result of the analysis shows the failure probability of stiffened cylindrical shells can be gained through adding the failure probability of each mode.
DYNAMICAL BEHAVIOR OF VISCOELASTIC CYLINDRICAL SHELLS UNDER AXIAL PRESSURES
Institute of Scientific and Technical Information of China (English)
程昌钧; 张能辉
2001-01-01
The hypotheses of the Kármán-Donnell theory of thin shells with large deflections and the Boltzmann laws for isotropic linear, viscoelastic materials, the constitutive equations of shallow shells are first derived. Then the governing equations for the deflection equations of elastic thin plates. Introducing proper assumptions, an approximate theory for viscoelastic cylindrical shells under axial pressures can be obtained. Finally, the dynamical behavior is studied in detail by using several numerical methods. Dynamical properties,such as, hyperchaos , chaos, strange attractor, limit cycle etc., are discovered.
Vibration control of cylindrical shells using active constrained layer damping
Ray, Manas C.; Chen, Tung-Huei; Baz, Amr M.
1997-05-01
The fundamentals of controlling the structural vibration of cylindrical shells treated with active constrained layer damping (ACLD) treatments are presented. The effectiveness of the ACLD treatments in enhancing the damping characteristics of thin cylindrical shells is demonstrated theoretically and experimentally. A finite element model (FEM) is developed to describe the dynamic interaction between the shells and the ACLD treatments. The FEM is used to predict the natural frequencies and the modal loss factors of shells which are partially treated with patches of the ACLD treatments. The predictions of the FEM are validated experimentally using stainless steel cylinders which are 20.32 cm in diameter, 30.4 cm in length and 0.05 cm in thickness. The cylinders are treated with ACLD patches of different configurations in order to target single or multi-modes of lobar vibrations. The ACLD patches used are made of DYAD 606 visco-elastic layer which is sandwiched between two layers of PVDF piezo-electric films. Vibration attenuations of 85% are obtained with maximum control voltage of 40 volts. Such attenuations are attributed to the effectiveness of the ACLD treatment in increasing the modal damping ratios by about a factor of four over those of conventional passive constrained layer damping (PCLD) treatments. The obtained results suggest the potential of the ACLD treatments in controlling the vibration of cylindrical shells which constitute the major building block of many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles.
Nonlinear dynamical behavior of shallow cylindrical reticulated shells
Institute of Scientific and Technical Information of China (English)
WANG Xin-zhi; LIANG Cong-xing; HAN Ming-jun; YEH Kai-yuan; WANG Gang
2007-01-01
By using the method of quasi-shells , the nonlinear dynamic equations of three-dimensional single-layer shallow cylindrical reticulated shells with equilateral triangle cell are founded. By using the method of the separating variable function, the transverse displacement of the shallow cylindrical reticulated shells is given under the conditions of two edges simple support. The tensile force is solved out from the compatible equations, a nonlinear dynamic differential equation containing second and third order is derived by using the method of Galerkin. The stability near the equilibrium point is discussed by solving the Floquet exponent and the critical condition is obtained by using Melnikov function. The existence of the chaotic motion of the single-layer shallow cylinmapping.
Tunable cylindrical shell as an element in acoustic metamaterial
Titovich, Alexey S
2014-01-01
Elastic cylindrical shells are fitted with an internal mechanism which is optimized so that, in the quasi-static regime, the combined system exhibits prescribed effective acoustic properties. The mechanism consists of a central mass supported by an axisymmetric distribution of elastic stiffeners. By appropriate selection of the mass and stiffness of the internal mechanism, the shell's effective acoustic properties (bulk modulus and density) can be tuned as desired. Subsonic flexural waves excited in the shell by the attachment of stiffeners are suppressed by including a sufficiently large number of such stiffeners. Effectiveness of the proposed metamaterial is demonstrated by matching the properties of a thin aluminum shell with a polymer insert to those of water. The scattering cross section in water is nearly zero over a broad range of frequencies at the lower end of the spectrum. By arranging the tuned shells in an array the resulting acoustic metamaterial is capable of steering waves. As an example, a cyl...
Nonlinear vibrations and imperfection sensitivity of a cylindrical shell containing axial fluid flow
del Prado, Z.; Gonçalves, P. B.; Païdoussis, M. P.
2009-10-01
The high imperfection sensitivity of cylindrical shells under static compressive axial loads is a well-known phenomenon in structural stability. On the other hand, less is known of the influence of imperfections on the nonlinear vibrations of these shells under harmonic axial loads. The aim of this work is to study the simultaneous influence of geometric imperfections and an axial fluid flow on the nonlinear vibrations and instabilities of simply supported circular cylindrical shells under axial load. The fluid is assumed to be non-viscous and incompressible and the flow to be isentropic and irrotational. The behavior of the thin-walled shell is modeled by Donnell's nonlinear shallow-shell equations. It is subjected to a static uniform compressive axial pre-load plus a harmonic axial load. A low-dimensional modal expansion, which satisfies the relevant boundary and continuity conditions, and takes into account all relevant nonlinear modal interactions observed in the past in the nonlinear vibrations of cylindrical shells with and without flow is used together with the Galerkin method to derive a set of eight coupled nonlinear ordinary differential equations of motion which are, in turn, solved by the Runge-Kutta method. The shell is considered to be initially at rest, in a position corresponding to a pre-buckling configuration. Then, a harmonic excitation is applied and conditions for parametric instability and dynamic snap-through are sought. The results clarify the marked influence of geometric imperfections and fluid flow on the dynamic stability boundaries, bifurcations and basins of attraction.
2DEG on a cylindrical shell with a screw dislocation
Filgueiras, Cleverson; Silva, Edilberto O.
2015-09-01
A two dimensional electron gas on a cylindrical surface with a screw dislocation is considered. More precisely, we investigate how both the geometry and the deformed potential due to a lattice distortion affect the Landau levels of such system. The case showing the deformed potential can be thought in the context of 3D common semiconductors where the electrons are confined on a cylindrical shell. We will show that important quantitative differences exist due to this lattice distortion. For instance, the effective cyclotron frequency is diminished by the deformed potential, which in turn enhances the Hall conductivity.
International Nuclear Information System (INIS)
A mixed layerwise theory and differential quadrature (DQ) method (LW-DQ) for three-dimensional free vibration analysis of arbitrary laminated circular cylindrical shells is introduced. Using the layerwise theory in conjunction with the three-dimensional form of Hamilton's principle, the transversely discretized equations of motion and the related boundary conditions are obtained. Then, the DQ method is employed to discretize the resulting equations in the axial directions. The fast convergence behavior of the method is demonstrated and its accuracy is verified by comparing the results with those of other shell theories obtained using conventional methods and also with those of ANSYS software. In the case of arbitrary laminated shells with simply supported ends, the exact solution is developed for comparison purposes. It is shown that using few DQ grid points, converged accurate solutions are obtained. Less computational efforts of the proposed approach with respect to ANSYS software is shown
Plasticity around an Axial Surface Crack in a Cylindrical Shell
DEFF Research Database (Denmark)
Krenk, Steen
1979-01-01
field in an axially cracked cylindrical shell arising from use of classical eighth order shallow shell theory is removed when use is made of a tenth order shell theory which accounts for transverse shear deformations. Although the membrane stresses are only moderately affected, the influence on the...... Ratwani,3–5 it generalises Dugdale's assumption of a concentrated yield zone in the plane of the crack but, contrary to that model, transverse shear effects are included and a continuous stress distribution is assumed in the yield zone. The inherent difficulties arising from the use of shell theory to...... model a three-dimensional problem can be overcome when the crack is sufficiently deep and the material is so ductile that full yield of the section around the crack develops before failure. In that case the calculations confirm the initial assumption of separation of the crack surfaces and the sides of...
Stresses at the intersection of two cylindrical shells
International Nuclear Information System (INIS)
The stress analysis based on the theory of a thin shell is carried out for two normally intersecting cylindrical shells with a large diameter ratio. Instead of the Donnell shallow shell equation, the modified Morley equation, which is applicable to ρ0(R/T)1/2XXXX1, is used for the analysis of the shell with cut-out. The solution in terms of displacement function for the nozzle with a non-planar end is based on the Love equation. The boundary forces and displacements at the intersection are all transformed from Gaussian coordinates (α,β) on the shell, or Gaussian coordinates (ζ,θ) on the nozzle into three-dimensional cylindrical coordinates (ρ,θ,z). Their expressions on the intersecting curve are periodic functions of θ and expanded in Fourier series. Every harmonics of Fourier coefficients of boundary forces and displacements are obtained by numerical quadrature.The results obtained are in agreement with those from the finite element method and experiments for d/D≤0.8. ((orig.))
2DEG on a cylindrical shell with a screw dislocation
Energy Technology Data Exchange (ETDEWEB)
Filgueiras, Cleverson, E-mail: cleversonfilgueiras@yahoo.com.br [Unidade Acadêmica de Física, Universidade Federal de Campina Grande, POB 10071, 58109-970, Campina Grande, Paraíba (Brazil); Departamento de Física (DFI), Universidade Federal de Lavras (UFLA), Caixa Postal 3037, 37200-000, Lavras, Minas Gerais (Brazil); Silva, Edilberto O., E-mail: edilbertoos@pq.cnpq.br [Departamento de Física, Universidade Federal do Maranhão, Campus Universitário do Bacanga, 65085-580, São Luís, Maranhão (Brazil)
2015-09-25
Highlights: • Electron gas on a cylindrical surface. • Quantum Hall effects. • Geometric potential induced by confinement. • Topological defect. - Abstract: A two dimensional electron gas on a cylindrical surface with a screw dislocation is considered. More precisely, we investigate how both the geometry and the deformed potential due to a lattice distortion affect the Landau levels of such system. The case showing the deformed potential can be thought in the context of 3D common semiconductors where the electrons are confined on a cylindrical shell. We will show that important quantitative differences exist due to this lattice distortion. For instance, the effective cyclotron frequency is diminished by the deformed potential, which in turn enhances the Hall conductivity.
Relativistic Gravitational Collapse of a Cylindrical Shell of Dust
Nakao, Ken-ichi; Kurita, Yasunari; Morisawa, Yoshiyuki; Harada, Tomohiro
2006-01-01
The gravitational collapse of a thick cylindrical shell of dust matter is investigated. It is found that a spacetime singularity forms on the symmetry axis and that it is necessarily naked, i.e., observable in principle. We propose a physically reasonable boundary condition at this naked singularity to construct the solution including its causal future. This boundary condition enables us to construct the unique continuation of spacetime beyond the naked singularity and ensures that the dust s...
Dynamic reponse of a cylindrical shell immersed in a potential fluid
International Nuclear Information System (INIS)
A numerical solution technique is presented for determining the dynamic response of a thin, elastic, circular, cylindrical shell of constant wall thickness and density, immersed in a potential fluid. The shell may be excited by an arbitrary radial forcing function with a specified time history and spatial distribution. In addition, a pressure history may be specified over a segment of the fluid outer boundary. Any of the natural shell end conditions may be prescribed. A numerical instability prevented direct solutions where the ratio of the hydrodynamic forces to shell inertial forces is greater than two. This instability is believed to be the result of the weak coupling between the equations describing the fluid to those describing the shell. To circumvent this instability, an effective mass was calculated and added to the shell. Comparison of numerical to experimental results are made using a 1/12 scale model of a nuclear reactor core support barrel. Natural frequencies and modes are determined for this model in air, water, and oil. The computed frequencies compare to experimental results to within 15%. The use of this numerical technique is illustrated by comparing it to an analytical solution for shell beam modes and an uncertainty in the analytical technique concerning the proper effective mass to use, is resolved
Nonlinear stability of cylindrical shells subjected to axial flow: Theory and experiments
Karagiozis, K. N.; Païdoussis, M. P.; Amabili, M.; Misra, A. K.
2008-01-01
This paper, is concerned with the nonlinear dynamics and stability of thin circular cylindrical shells clamped at both ends and subjected to axial fluid flow. In particular, it describes the development of a nonlinear theoretical model and presents theoretical results displaying the nonlinear behaviour of the clamped shell subjected to flowing fluid. The theoretical model employs the Donnell nonlinear shallow shell equations to describe the geometrically nonlinear structure. The clamped beam eigenfunctions are used to describe the axial variations of the shell deformation, automatically satisfying the boundary conditions and the circumferential continuity condition exactly. The fluid is assumed to be incompressible and inviscid, and the fluid-structure interaction is described by linear potential flow theory. The partial differential equation of motion is discretized using the Galerkin method and the final set of ordinary differential equations are integrated numerically using a pseudo-arclength continuation and collocation techniques and the Gear backward differentiation formula. A theoretical model for shells with simply supported ends is presented as well. Experiments are also described for (i) elastomer shells subjected to annular (external) air-flow and (ii) aluminium and plastic shells with internal water flow. The experimental results along with the theoretical ones indicate loss of stability by divergence with a subcritical nonlinear behaviour. Finally, theory and experiments are compared, showing good qualitative and reasonable quantitative agreement.
Dynamic reponse of a cylindrical shell immersed in a potential fluid
Energy Technology Data Exchange (ETDEWEB)
Cummings, G.E.
1978-04-18
A numerical solution technique is presented for determining the dynamic response of a thin, elastic, circular, cylindrical shell of constant wall thickness and density, immersed in a potential fluid. The shell may be excited by an arbitrary radial forcing function with a specified time history and spatial distribution. In addition, a pressure history may be specified over a segment of the fluid outer boundary. Any of the natural shell end conditions may be prescribed. A numerical instability prevented direct solutions where the ratio of the hydrodynamic forces to shell inertial forces is greater than two. This instability is believed to be the result of the weak coupling between the equations describing the fluid to those describing the shell. To circumvent this instability, an effective mass was calculated and added to the shell. Comparison of numerical to experimental results are made using a /sup 1///sub 12/ scale model of a nuclear reactor core support barrel. Natural frequencies and modes are determined for this model in air, water, and oil. The computed frequencies compare to experimental results to within 15%. The use of this numerical technique is illustrated by comparing it to an analytical solution for shell beam modes and an uncertainty in the analytical technique concerning the proper effective mass to use, is resolved.
Plastic limit loads for cylindrical shell intersections under combined loading
International Nuclear Information System (INIS)
In this research, applied methods of nonlinear analysis and results of determining the plastic limit loads for shell intersection configurations under combined internal pressure, in-plane moment and out-plane moment loadings are presented. The numerical analysis of shell intersections is performed using the finite element method, geometrically nonlinear shell theory in quadratic approximation and plasticity theory. For determining the load parameter of proportional combined loading, the developed maximum criterion of rate of change of relative plastic work is employed. The graphical results for model of cylindrical shell intersection under different two-parameter combined loadings (as generalized plastic limit load curves) and three-parameter combined loading (as generalized plastic limit load surface) are presented on the assumption that the internal pressure, in-plane moment and out-plane moment loads were applied in a proportional manner. - Highlights: • This paper presents nonlinear two-dimensional FE analysis for shell intersections. • Determining the plastic limit loads under combined loading is considered. • Developed maximum criterion of rate of change of relative plastic work is employed. • Plastic deformation mechanism in shell intersections is discussed. • Results for generalized plastic limit load curves of branch intersection are presented
Plastic limit load of cylindrical shells with cutouts subject to pure bending moment
International Nuclear Information System (INIS)
In this paper, the results of limit analyses of thin-walled cylindrical shells with a circular hole under the action of a pure bending moment are presented in dimensionless form for a wide range of geometric parameters. Analytical estimation of lower bound limit load is carried out using the feasible sequential quadratic programming (FSQP) technique. The finite element calculations of limit load consist of elastic-plastic and lower and upper bound predictions by elastic compensation methods. A testing device was made to perform experiments to obtain limit bending moment of cylinders with circular openings. The analytical and finite element calculations are compared with experimental results and their correlation is discussed. The finite element calculation results were found to be in good agreement with lower bound estimations by the nonlinear mathematical programming (FSQP) method and the formula proposed by Shu
An Experimental Investigation of the Implosion of Cylindrical Shell Structures
Ikeda, C. M.; Wilkerling, J.; Duncan, J. H.
2009-11-01
An experimental study of the physics of the implosion of cylindrical shell structures in a high-pressure water environment was performed. The shell structures are filled with air at atmospheric pressure and the implosions occur when the water pressure is raised above the shell buckling stability limit. High-speed photography (27,000 fps) was used to observe and measure the motion of the structure during its implosion. High-frequency underwater blast sensors recorded dynamic pressure waves at 13 positions in the tank. The cylindrical models are made from various aluminum alloys (diameter D = 39.1 mm, wall thickness t = 0.89 mm) and brass (D = 16.7 to 25.4 mm, t = 0.33 to 0.36 mm). The ends of the tubes were sealed with Aluminum caps. The pressure records are interpreted in light of the high-speed movies. Cylinder length-to-diameter (L/D) ratios between 6 and 10 were examined; in this range the cylinders implode in a mode 2 cross-sectional shape at pressures between 6.9 and 28.7 bar. It is found that the pressure versus time records from sensors placed at the same dimensionless radial position (r/D) from the cylinder surface scale well with time and pressure scales from cavitation bubble collapse theory.
Explosion-Induced Implosions of Cylindrical Shell Structures
Ikeda, C. M.; Duncan, J. H.
2010-11-01
An experimental study of the explosion-induced implosion of cylindrical shell structures in a high-pressure water environment was performed. The shell structures are filled with air at atmospheric pressure and are placed in a large water-filled pressure vessel. The vessel is then pressurized to various levels P∞=αPc, where Pc is the natural implosion pressure of the model and α is a factor that ranges from 0.1 to 0.9. An explosive is then set off at various standoff distances, d, from the model center line, where d varies from R to 10R and R is the maximum radius of the explosion bubble. High-speed photography (27,000 fps) was used to observe the explosion and resulting shell structure implosion. High-frequency underwater blast sensors recorded dynamic pressure waves at 6 positions. The cylindrical models were made from aluminum (diameter D = 39.1 mm, wall thickness t = 0.89 mm, length L = 240 mm) and brass (D = 16.7 mm, t = 0.36 mm, L=152 mm) tubes. The pressure records are interpreted in light of the high-speed movies. It is found that the implosion is induced by two mechanisms: the shockwave generated by the explosion and the jet formed during the explosion-bubble collapse. Whether an implosion is caused by the shockwave or the jet depends on the maximum bubble diameter and the standoff distance.
Prediction of Vibrational Behavior of Grid-Stiffened Cylindrical Shells
Directory of Open Access Journals (Sweden)
G. H. Rahimi
2014-01-01
Full Text Available A unified analytical approach is applied to investigate the vibrational behavior of grid-stiffened cylindrical shells with different boundary conditions. A smeared method is employed to superimpose the stiffness contribution of the stiffeners with those of shell in order to obtain the equivalent stiffness parameters of the whole panel. Theoretical formulation is established based on Sanders’ thin shell theory. The modal forms are assumed to have the axial dependency in the form of Fourier series whose derivatives are legitimized using Stoke's transformation. A 3D finite element model is also built using ABAQUS software which takes into consideration the exact geometric configuration of the stiffeners and the shell. The achievements from the two types of analyses are compared with each other and good agreement has been obtained. The Influences of variations in shell geometrical parameters, boundary condition, and changes in the cross stiffeners angle on the natural frequencies are studied. The results obtained are novel and can be used as a benchmark for further studies. The simplicity and the capability of the present method are also discussed.
Study of laminated anisotropic cylindrical shells sensitive to transverse stresses
International Nuclear Information System (INIS)
A variational method for the determination of stresses and displacements in a multilayered cylindrical shell is presented. All included materials are linearly anisotropic (monoclinic) - i.e. directional fibres reinforced materials. This study uses a functional which is derived from the potential energy of the structure. The incoming stresses are σRR, σRθ, σRZ, and the displacements are uθ and uZ. This mixed group is the main variables of the formulation. It is shown that the stationarity conditions of the functional are the equilibrium equations and the associated boundary conditions. An approximate solution can be found using a finite element method which realizes a tridimensional discretization of the structure. The program issued is a specific mean for studying the transverse shear stresses in laminated cylindrical structures. From the results obtained it can be concluded that it meets all requirements for the purposes of this range of problems. (author)
Sound radiation of a functionally graded material cylindrical shell in water by mobility method
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
Based on the fundamental dynamic equations of functionally graded material (FGM) cylindrical shell, this paper investigates the sound radiation of vibrational FGM shell in water by mobility method. This model takes into account the exterior fluid loading due to the sound press radiated by the FGM shell. The FGM cylindrical shell was excited by a harmonic line radial force uniformly distributing along the generator. The FGM shell equations of motion, the Helmholtz equation in the exterior fluid medium and th...
Nonlinear free vibrations of shallow cylindrical shells at elevated temperature
International Nuclear Information System (INIS)
Modern structures are often subjected to severe vibrations and high temperatures. In such cases vibrations and thermal stresses play an important and even a primary role. The aim of the present paper is to investigate the behaviour of shallow cylindrical shells vibrating at large amplitudes including thermal effect. Though the present project of the author includes the nonlinear analysis under a general thermal boundary condition, the present paper concerns with a specific temperature distribution. The analysis is based on Karman-Tsien field equations extended to thermal loading. (orig./GL)
Linear stability analysis of capillary instabilities for concentric cylindrical shells
Liang, X; Nave, J -C; Johnson, S G
2010-01-01
Motivated by complex multi-fluid geometries currently being explored in fibre-device manufacturing, we study capillary instabilities in concentric cylindrical flows of N fluids with arbitrary viscosities, thicknesses, densities, and surface tensions in both the Stokes regime and for the full Navier--Stokes problem. Generalising previous work by Tomotika (N=2), Stone & Brenner (N=3, equal viscosities) and others, we present a full linear stability analysis of the growth modes and rates, reducing the system to a linear generalised eigenproblem in the Stokes case. Furthermore, we demonstrate by Plateau-style geometrical arguments that only axisymmetric instabilities need be considered. We show that the N=3 case is already sufficient to obtain several interesting phenomena: limiting cases of thin shells or low shell viscosity that reduce to N=2 problems, and a system with competing breakup processes at very different length scales. The latter is demonstrated with full 3-dimensional simulations. Many $N > 3$ c...
Transverse shear effect in a circumferentially cracked cylindrical shell
Delale, F.; Erdogan, F.
1979-01-01
The objectives of the paper are to solve the problem of a circumferentially-cracked cylindrical shell by taking into account the effect of transverse shear, and to obtain the stress intensity factors for the bending moment as well as the membrane force as the external load. The formulation of the problem is given for a specially orthotropic material within the framework of a linearized shallow shell theory. The particular theory used permits the consideration of all five boundary conditions as to moment and stress resultants on the crack surface. The effect of Poisson's ratio on the stress intensity factors and the nature of the out-of-plane displacement along the edges of the crack, i.e., bulging, are also studied.
Flow-induced vibration of circular cylindrical structures
Energy Technology Data Exchange (ETDEWEB)
Chen, S.S.
1985-06-01
This report summarizes the flow-induced vibration of circular cylinders in quiescent fluid, axial flow, and crossflow, and applications of the analytical methods and experimental data in design evaluation of various system components consisting of circular cylinders. 219 figs., 30 tabs. (JDB)
Flow-induced vibration of circular cylindrical structures
International Nuclear Information System (INIS)
This report summarizes the flow-induced vibration of circular cylinders in quiescent fluid, axial flow, and crossflow, and applications of the analytical methods and experimental data in design evaluation of various system components consisting of circular cylinders. 219 figs., 30 tabs
Effects of Shell-Buckling Knockdown Factors in Large Cylindrical Shells
Hrinda, Glenn A.
2012-01-01
Shell-buckling knockdown factors (SBKF) have been used in large cylindrical shell structures to account for uncertainty in buckling loads. As the diameter of the cylinder increases, achieving the manufacturing tolerances becomes increasingly more difficult. Knockdown factors account for manufacturing imperfections in the shell geometry by decreasing the allowable buckling load of the cylinder. In this paper, large-diameter (33 ft) cylinders are investigated by using various SBKF's. An investigation that is based on finite-element analysis (FEA) is used to develop design sensitivity relationships. Different manufacturing imperfections are modeled into a perfect cylinder to investigate the effects of these imperfections on buckling. The analysis results may be applicable to large- diameter rockets, cylindrical tower structures, bulk storage tanks, and silos.
Chaotic vibration of a liquid-filled thin cylindrical shell
International Nuclear Information System (INIS)
Recently, a large number of thin walled cylindrical tanks have been widely used, such as oil-storage tanks, and LMFBR primary components. To assess the safety of these systems against earthquakes, it is of great technical importance to clarify the fluid-coupled vibration characteristics of the systems subjected to certain kinds of dynamic loads. This paper describes an experimental study on the chaos of a partially liquid-filled cylindrical tank under horizontal excitation. The test cylinder with a mean radius of 170 mm was made of polyester film with a nominal thickness of 0.188 mm which was lap-joined along a longitudinal seam and bonded with an aluminum end plate along one edge. Shaking table tests were conducted in order to investigate the dynamic characteristics of the shell response. Several types of limit cycles were observed at lower accelerations, and the instability phenomenon, which jumped at some excitation frequencies, occurred for acceleration amplitudes above a critical value. Finally, at higher excitation accelerations, the shell responses became chaotic. The occurrence of the chaos was recognized by the time history, Poincare map, phase trajectory, power spectrum and a positive Lyapunov exponent calculated from the orbits in the three dimensional phase space. In order to visualize the strange attractor, phase portraits were constructed by embedding the trajectories in the phase space
Nemeth, Michael P.
2014-01-01
Nonlinear and bifurcation buckling equations for elastic, stiffened, geometrically perfect, right-circular cylindrical, anisotropic shells subjected to combined loads are presented that are based on Sanders' shell theory. Based on these equations, a three-parameter approximate Rayleigh-Ritz solution and a classical solution to the buckling problem are presented for cylinders with simply supported edges. Extensive comparisons of results obtained from these solutions with published results are also presented for a wide range of cylinder constructions. These comparisons include laminated-composite cylinders with a wide variety of shell-wall orthotropies and anisotropies. Numerous results are also given that show the discrepancies between the results obtained by using Donnell's equations and variants of Sanders' equations. For some cases, nondimensional parameters are identified and "master" curves are presented that facilitate the concise representation of results.
Elastic Buckling of Bionic Cylindrical Shells Based on Bamboo
Institute of Scientific and Technical Information of China (English)
Jian-feng Ma; Wu-yi Chen; Ling Zhao; Da-hai Zhao
2008-01-01
High load-bearing efficiency is one of the advantages of biological structures after the evolution of billions of years.Biomimicking from nature may offer the potential for lightweight design. In the viewpoint of mechanics properties, the culm of bamboo comprises of two types of cells and the number of the vascular bundles takes a gradient of distribution. A three-point bending test was carried out to measure the elastic modulus. Results show that the elastic modulus of bamboo decreases gradually from the periphery towards the centre. Based on the structural characteristics of bamboo, a bionic cylindrical structure was designed to mimic the gradient distribution of vascular bundles and parenchyma cells. The buckling resistance of the bionic structure was compared with that of a traditional shell of equal mass under axial pressure by finite element simulations. Results show that the load-bearing capacity of bionic shell is increased by 124.8%. The buckling mode of bionic structure is global buckling while that of the conventional shell is local buckling.
Resonant Excitation of a Truncated Metamaterial Cylindrical Shell by a Thin Wire Monopole
DEFF Research Database (Denmark)
Kim, Oleksiy S.; Erentok, Aycan; Breinbjerg, Olav
2009-01-01
A truncated metamaterial cylindrical shell excited by a thin wire monopole is investigated using the integral equation technique as well as the finite element method. Simulations reveal a strong field singularity at the edge of the truncated cylindrical shell, which critically affects the matching...
Stress Analysis of Composite Cylindrical Shells with an Elliptical Cutout
Oterkus, E.; Madenci, E.; Nemeth, M. P.
2007-01-01
A special-purpose, semi-analytical solution method for determining the stress and deformation fields in a thin laminated-composite cylindrical shell with an elliptical cutout is presented. The analysis includes the effects of cutout size, shape, and orientation; non-uniform wall thickness; oval-cross-section eccentricity; and loading conditions. The loading conditions include uniform tension, uniform torsion, and pure bending. The analysis approach is based on the principle of stationary potential energy and uses Lagrange multipliers to relax the kinematic admissibility requirements on the displacement representations through the use of idealized elastic edge restraints. Specifying appropriate stiffness values for the elastic extensional and rotational edge restraints (springs) allows the imposition of the kinematic boundary conditions in an indirect manner, which enables the use of a broader set of functions for representing the displacement fields. Selected results of parametric studies are presented for several geometric parameters that demonstrate that analysis approach is a powerful means for developing design criteria for laminated-composite shells.
Coupling cavity model for circular cylindrical waveguide with uniform cross section
Ayzatsky, M I
2016-01-01
We developed the general approach that gives possibility to calculate the coupling coefficients for arbitrary chain of resonators without using the great number of eigen functions. For understanding this method and having possibility to control the accuracy of obtained results, we applied this procedure for simplest structure that has the analytical solutions - a circular cylindrical waveguide with uniform cross section.
Non-linear Vibrations of Deep Cylindrical Shells by the p-Version Finite Element Method
Pedro Ribeiro; Bruno Cochelin; Sergio Bellizzi
2010-01-01
A p-version shell finite element based on the so-called shallow shell theory is for the first time employed to study vibrations of deep cylindrical shells. The finite element formulation for deep shells is presented and the linear natural frequencies of different shells, with various boundary conditions, are computed. These linear natural frequencies are compared with published results and with results obtained using a commercial software finite element package; good agreement is found. Exter...
Efficient method for analyzing multiple circular cylindrical nanoparticles on a substrate
Lu, Xun; Lu, Ya Yan
2016-05-01
Due to the existing nanofabrication techniques, many metallic or dielectric nanoparticles are cylindrical objects with top and bottom surfaces parallel to a substrate and side boundaries perpendicular to the substrate. In this paper, we develop a relatively simple and efficient semi-analytic method for analyzing the scattering of light by a set of circular cylindrical objects (of finite height) on a layered background. The method relies on expanding the field in one-dimensional modes in layered regions where the material properties change with one spatial variable only, to establish a linear system on the boundaries separating the layered regions. Although the ‘expansion coefficients’ are two-dimensional (2D) functions, they satisfy scalar 2D Helmholtz equations which have analytic solutions due to the special geometry. The method is used to analyze dielectric and metallic circular cylindrical nanoparticles on a substrate or in free space.
A Semi-Analytical Model for Buckling of Stiffened Cylindrical Shells
2013-01-01
Cylindrical shells are common configurations within the technology. The transition from the side to the bottom on a ship has the shape of a fourth of a cylindrical shell. Both ring and stringer stiffeners can be added to the shell for support. Buckling of this type of structure is an important area of interest. The main purpose of this thesis has been to make a semi-analytical model that can describe how a ring stiffened shell and stringer stiffened shell respond during buckling. A va...
Analysis of circumferential waves on a water-filled cylindrical shell
Institute of Scientific and Technical Information of China (English)
FAN Wei; ZHENG Guoyin; FAN Jun
2012-01-01
The formation of scattering field from a water-filled cylindrical shell was studied. The analytic solutions of scattering field are derived using elastic thin shell theory and Sommerfeld-Watson Transformation （SWT） method. Complex wave-number poles of circumferential waves are found numerically, the phase speed and attenuation of circumferential waves between the situation of a hollow cylindrical shell and a water-filled cylindrical shell are compared. The synthesis of backscattering form functions which are sum of specular reflection component and circumferential waves is consistent with normal mode result. The calculated echo sequences of additional fluid circumferential waves are compared with experimental results. The results show that richer resonance peaks appeared in the backscattering form functions of a water-filled cylindrical shell and the formation of echo＇s structure are due to re-radiation effects of additional fluid circumferential waves.
The Nonlinear Instability Modes of Dished Shallow Shells under Circular Line Loads
Liu Chang-Jiang; Zheng Zhou-Lian; Huang Cong-Bing; He Xiao-Ting; Sun Jun-Yi; Chen Shan-Lin
2011-01-01
This paper investigated the nonlinear stability problem of dished shallow shells under circular line loads. We derived the dimensionless governing differential equations of dished shallow shell under circular line loads according to the nonlinear theory of plates and shells and solved the governing differential equations by combing the free-parameter perturbation method (FPPM) with spline function method (SFM) to analyze the nonlinear instability modes of dished shallow shell under circular l...
Directory of Open Access Journals (Sweden)
Seung-Bok Choi
2013-02-01
Full Text Available In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.
Buckling of Cracked Laminated Composite Cylindrical Shells Subjected to Combined Loading
Allahbakhsh, Hamidreza; Shariati, Mahmoud
2013-10-01
A series of finite element analysis on the cracked composite cylindrical shells under combined loading is carried out to study the effect of loading condition, crack size and orientation on the buckling behavior of laminated composite cylindrical shells. The interaction buckling curves of cracked laminated composite cylinders subject to different combinations of axial compression, bending, internal pressure and external pressure are obtained, using the finite element method. Results show that the internal pressure increases the critical buckling load of the CFRP cylindrical shells and bending and external pressure decrease it. Numerical analysis show that axial crack has the most detrimental effect on the buckling load of a cylindrical shell and results show that for lower values of the axial compressive load and higher values of the external pressure, the buckling is usually in the global mode and for higher values of axial compressive load and lower levels of external pressure the buckling mode is mostly in the local mode.
Qiu, Q.; Fang, Z. P.; Wan, H. C.; Zheng, L.
2013-07-01
Based on the Donnell assumptions and linear visco-elastic theory, the constitutive equations of the cylindrical shell with multilayer Passive Constrained Layer Damping (PCLD) treatments are described. The motion equations and boundary conditions are derived by Hamilton principle. After trigonometric series expansion and Laplace transform, the state vector is introduced and the dynamic equations in state space are established. The transfer function method is used to solve the state equation. The dynamic performance including the natural frequency, the loss factor and the frequency response of clamped-clamped multi-layer PCLD cylindrical shell is obtained. The results show that multi-layer PCLD cylindrical shell is more effective than the traditional three-layer PCLD cylindrical shell in suppressing vibration and noise if the same amount of material is applied. It demonstrates a potential application of multi-layer PCLD treatments in many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles.
International Nuclear Information System (INIS)
Based on the Donnell assumptions and linear visco-elastic theory, the constitutive equations of the cylindrical shell with multilayer Passive Constrained Layer Damping (PCLD) treatments are described. The motion equations and boundary conditions are derived by Hamilton principle. After trigonometric series expansion and Laplace transform, the state vector is introduced and the dynamic equations in state space are established. The transfer function method is used to solve the state equation. The dynamic performance including the natural frequency, the loss factor and the frequency response of clamped-clamped multi-layer PCLD cylindrical shell is obtained. The results show that multi-layer PCLD cylindrical shell is more effective than the traditional three-layer PCLD cylindrical shell in suppressing vibration and noise if the same amount of material is applied. It demonstrates a potential application of multi-layer PCLD treatments in many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles
Institute of Scientific and Technical Information of China (English)
Li Li; Wen Ji-Hong; Cai Li; Zhao Hong-Gang; Wen Xi-Sen
2013-01-01
Using the multilayered cylinder model,we study acoustic scattering from a submerged cylindrical shell coated with locally resonant acoustic metamaterials,which exhibit locally negative effective mass densities.A spring model is introduced to replace the traditional transfer matrix,which may be singular in the negative mass region.The backscattering form function and the scattering cross section are calculated to discuss the acoustic properties of the coated submerged cylindrical shell.
Seung-Bok Choi; Juncheol Jeon; Jung Woo Sohn; Heung Soo Kim
2013-01-01
In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs) were used as actuators and sensors. One MFC was used as an excite...
International Nuclear Information System (INIS)
Using the multilayered cylinder model, we study acoustic scattering from a submerged cylindrical shell coated with locally resonant acoustic metamaterials, which exhibit locally negative effective mass densities. A spring model is introduced to replace the traditional transfer matrix, which may be singular in the negative mass region. The backscattering form function and the scattering cross section are calculated to discuss the acoustic properties of the coated submerged cylindrical shell. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)
Institute of Scientific and Technical Information of China (English)
吴林志; Kunio Funami
2002-01-01
The electro-elastic field of the infinite piezoelectric medium with two piezoelectric circular cylindrical inclusions is derived under the antiplane shear stresses and inplane electric fields. The analytical solution is obtained. The proposed method is based upon the use of conformal mapping and the theorem of analytic continuation. From the results obtained, it can be found that the electro-elastic field depends on the material constants of individual phases, the geometric parameters of the system and the applied antiplane shear stresses and electric fields at infinity. In addition, the specific cases when two circular cylindrical inclusions are tangent to each other and they are holes and/or rigid ones, are also studied in this paper.
Design guide for calculating hydrodynamic mass. Part I. Circular cylindrical structures
International Nuclear Information System (INIS)
Many reactor and plant components contain, or are submerged in, a fluid. The fluid moving with a vibrating structure has an important effect on the dynamics of the structure, particularly on its natural frequencies. The effect of the fluid on natural frequencies can be accounted for using the hydrodynamic mass associated with the structure. The design guide provides formulas, graphs, and computer programs for calculating hydrodynamic masses of circular cylindrical structures
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
We analyze thickness-shear vibration of an axially poled circular cylindrical tube with unattached electrodes and air gaps. Both free and electrically forced vibrations are studied. Exact solutions are obtained from the equations of linear piezoelectricity. Resonant frequencies and the impedance of the transducer are calculated from the solution. Results show that the resonant frequencies are sensitive to the dimensions of the air gaps when the gaps are thin. The impedance depends strongly on the air gaps.
The vector potential of a circular cylindrical antenna in terms of a toroidal harmonic expansion
Selvaggi, Jerry; Salon, Sheppard; Chari, M. V. K.
2008-08-01
A toroidal harmonic expansion is developed which is used to represent the vector potential due to a circular cylindrical antenna with a rectangular cross section at any arbitrary point in space. The singular part of the antenna kernel is represented by an associated toroidal harmonic expansion and the analytic part of the kernel is represented by a binomial expansion. A simple example is given to illustrate the application of the toroidal expansion.
Beirao Da Veiga, Lourenco
2001-01-01
We introduce, and numerically solve for decreasing thicknesses, particular toroidal and cylindrical shell problems which hold, due to load irregularity, an intermediate asymptotic behaviour. The numerical results are compared with those obtained applying a very recent asymptotic shell classification theory. Finally, we examine a local energy oscillation effect, with thickness-dependent frequency, that was found in all the problems treated.
A cylindrical shell with an axial crack under skew-symmetric loading.
Yuceoglu, U.; Erdogan, F.
1973-01-01
The skew-symmetric problem for a cylindrical shell containing an axial crack is considered. It is assumed that the material has a special orthotropy - namely, that the shear modulus may be evaluated from the measured Young's moduli and Poisson ratios and is not an independent material constant. The problem is solved within the confines of an eighth-order linearized shallow shell theory. As numerical examples, the torsion of an isotropic cylinder and that of a specially orthotropic cylinder (titanium) are considered. The membrane and bending components of the stress intensity factor are calculated and are given as functions of a dimensionless shell parameter. In the torsion problem for the axially cracked cylinder the bending effects appear to be much more significant than that found for the circumferentially cracked cylindrical shell. Also, as the shell parameter increases, unlike the results found in the pressurized shell, the bending stresses around crack ends do not change sign.
A note on the geometry of a cylindrical shell with screw dislocation
International Nuclear Information System (INIS)
This Letter reports the equivalence of the geometries of a cylindrical shell with screw dislocation and another without defect but with a larger radius. The issue may have applications in condensed matter physics for models where quantum particles (such as electrons and holes) move on the walls of nanotubes. -- Highlights: ► Equivalence of effective geometries of cylindrical shells with defects. ► Physics of quantum particles moving on the shells will look the same. ► A nanotube could be replaced by a thinner nanotube with appropriate screw dislocation.
A note on the geometry of a cylindrical shell with screw dislocation
Energy Technology Data Exchange (ETDEWEB)
De Lorenci, Vitorio A., E-mail: delorenci@unifei.edu.br [Instituto de Ciências Exatas, Universidade Federal de Itajubá, Itajubá, MG 37500-903 (Brazil); Moreira, Edisom S., E-mail: moreira@unifei.edu.br [Instituto de Ciências Exatas, Universidade Federal de Itajubá, Itajubá, MG 37500-903 (Brazil)
2012-07-09
This Letter reports the equivalence of the geometries of a cylindrical shell with screw dislocation and another without defect but with a larger radius. The issue may have applications in condensed matter physics for models where quantum particles (such as electrons and holes) move on the walls of nanotubes. -- Highlights: ► Equivalence of effective geometries of cylindrical shells with defects. ► Physics of quantum particles moving on the shells will look the same. ► A nanotube could be replaced by a thinner nanotube with appropriate screw dislocation.
Crack Path Bifurcation at a Tear Strap in a Pressurized Stiffened Cylindrical Shell
Cowan, Amy Lorraine
1999-01-01
A finite element model of a fracture test specimen is developed using the STAGS computer code (STructural Analysis of General Shells). The test specimen was an internally pressurized, aluminum cylindrical shell reinforced with two externally bonded aluminum tear straps around its circumference. The shell contained an initial, axial through-crack centered between the straps. The crack propagated slowly in the axial direction as the pressure increased above a certain value until a maximum press...
Directory of Open Access Journals (Sweden)
Surya Narain
1981-04-01
Full Text Available This paper investigates magneto-elastic torsional waves in a composite non homogeneous cylindrical shell under initial stress. The non homogeneous character of the shell is due to the variable elastic constants C/sub ij/ and the variable density rho. The composite form of the shell is due to the combination of orthotropic elastic material and visco-elastic material of general linear type. Frequency equation for the said wave has been derived.
The bending vibration response and approximate calculation of elastic cylindrical shell
Institute of Scientific and Technical Information of China (English)
CHEN Xiao-li; SHENG Mei-ping; HE Chen
2006-01-01
Useful structure characteristics of elastic cylindrical shells have led them to being widely applied in virtual projects ,so it is important to conduct vibration research on the shells and find it's a simpler corresponding compact calculation method. Utilising the input and transfer point mobility of a thin plate structure, a theoretical expression of the cylindrical shell's bending vibration responsewas deduced and numerical simulations were done to simplify the theoretical expression within an acceptable error margin, greatly reducing the amount of computations. Furthermore, whole vibration response distributions of the cylindrical shell were analyzed. It was found thathe vibration energy propagates in helical form under mono-frequency excitation, while under bandwidth frequency excitation, it attenuates around in term of fluctuation. The axial attenuation rate of the vibration energy is larger than the circumferential attenuation rate.
Mechanical stability of cylindrical thin-shell wormholes
Energy Technology Data Exchange (ETDEWEB)
Sharif, M. [University of the Punjab, Department of Mathematics, Lahore (Pakistan); Azam, M. [University of Education, Division of Science and Technology, Lahore (Pakistan)
2013-04-15
In this paper, we apply the cut and paste procedure to the charged black string for the construction of a thin-shell wormhole. We consider the Darmois-Israel formalism to determine the surface stresses of the shell. We take the Chaplygin gas to deal with the matter distribution on shell. The radial perturbation approach (preserving the symmetry) is used to investigate the stability of static solutions. We conclude that stable static solutions exist both for uncharged and charged black string thin-shell wormholes for particular values of the parameters. (orig.)
A Circular-cylindrical Flux-rope Analytical Model for Magnetic Clouds
Nieves-Chinchilla, T.; Linton, M. G.; Hidalgo, M. A.; Vourlidas, A.; Savani, N. P.; Szabo, A.; Farrugia, C.; Yu, W.
2016-05-01
We present an analytical model to describe magnetic flux-rope topologies. When these structures are observed embedded in Interplanetary Coronal Mass Ejections (ICMEs) with a depressed proton temperature, they are called Magnetic Clouds (MCs). Our model extends the circular-cylindrical concept of Hidalgo et al. by introducing a general form for the radial dependence of the current density. This generalization provides information on the force distribution inside the flux rope in addition to the usual parameters of MC geometrical information and orientation. The generalized model provides flexibility for implementation in 3D MHD simulations. Here, we evaluate its performance in the reconstruction of MCs in in situ observations. Four Earth-directed ICME events, observed by the Wind spacecraft, are used to validate the technique. The events are selected from the ICME Wind list with the magnetic obstacle boundaries chosen consistently with the magnetic field and plasma in situ observations and with a new parameter (EPP, the Electron Pitch angle distribution Parameter) which quantifies the bidirectionally of the plasma electrons. The goodness of the fit is evaluated with a single correlation parameter to enable comparative analysis of the events. In general, at first glance, the model fits the selected events very well. However, a detailed analysis of events with signatures of significant compression indicates the need to explore geometries other than the circular-cylindrical. An extension of our current modeling framework to account for such non-circular CMEs will be presented in a forthcoming publication.
Relativistic dynamics of cylindrical shells of counter-rotating particles
Hamity, V H; Barraco, D E
2007-01-01
Although infinite cylinders are not astrophysical entities, it is possible to learn a great deal about the basic qualitative features of generation of gravitational waves and the behavior of the matter conforming such shells in the limits of very small radius. We describe the analytical model using kinetic theory for the matter and the junction conditions through the shell to obtain its equation of motion. The nature of the static solutions are analyzed, both for a single shell as well as for two concentric shells. In this second case, for a time dependent external shell, we integrate numerically the equation of motion for several values of the constants of the system. Also, a brief description in terms of the Komar mass is given to account for the gravitational wave energy emitted by the system.
Ray-based modeling of reverberation in subsurface circular cylindrical void
Chen, Ping; Xia, Dan; Chen, Boyuan; Li, Lin; Li, Xiuzhong; Dong, Tian-lin
2011-03-01
Ray representation of electromagnetic resonance (reverberation) mode in subsurface circular cylindrical dielectric resonator (including void) is proposed. The modal ray path must be regular polygon or polystar. Travel time formulas for fundamental resonance multiples and the detecting conditions for non-exact-backscattering rays are derived. Simulation of time-distance curves of a modal hollow concrete block is generally concurred to the measured ground penetrating radar signal pattern. The proposed modeling method can be generalized to other resonant cavities with different profiles and provide a sound base for further applications of other more complicated geophysics science and engineering fields, particularly in ray-based tomography.
International Nuclear Information System (INIS)
The purpose of this paper is the formulation of a Wave Concept Iterative Process (WCIP) for the analysis of the microwave planar circuits printed between two dielectric mediums in a cylindrical metallic box. This method is based on the transverse wave formulation. It also uses the Hankel Transform to express the integral relation in a spectral domain. An example of annular ring and circular patch loaded by annular ring has been studied and the obtained results validate the new approach. The good agreement between the simulation results and the experimental published data justifies the design procedure and validates the present analysis approach.
Paranin, Vyacheslav D.; Karpeev, Sergey V.; Kazanskiy, Nikolay L.; Krasnov, Andrey P.
2016-03-01
The optical system for converting laser beams with circular polarization to cylindrical vector beams on the basis of anisotropic crystals has been developed. The experimental research of beam formation quality has been carried out on the both polarization and structural characteristics. The research showed differences in the formation of the azimuthal and radial polarizations for Gaussian modes and Bessel beams. The boundaries of changes of the optical system parameters to form different types of polarizations with different amplitude and phase distributions have been identified.
Finite Element Modeling of a Fluid Filled Cylindrical Shell with Active Constrained Layer Damping
Institute of Scientific and Technical Information of China (English)
ZHANG Yi; ZHANG Zhi-yi; TONG Zong-peng; HUA Hong-xing
2005-01-01
On the basis of the piezoelectric theory, Mindlin plate theory, viscoelastic theory and ideal fluid equa tion, the finite element modeling of a fluid-filled cylindrical shell with active constrained layer damping (ACLD) was discussed. Energy methods and Lagrange's equation were used to obtain dynamic equations of the cylindrical shell with ACLD treatments, which was modeled as well with the finite element method. The GHM (Golla-Hughes-McTavish) method was applied to model the frequency dependent damping of viscoelastic material. Ideal and incompressible fluid was considered to establish the dynamic equations of the fluid-filled cylindrical shell with ACLD treatments, Numerical results obtained from the finite element analysis were compared with those from an experiment. The comparison shows that the proposed modeling method is accurate and reliable.
Effect of weld reinforcement on axial plastic buckling of welded steel cylindrical shells
Institute of Scientific and Technical Information of China (English)
Chu-lin YU; Zhi-ping CHEN; Ji WANG; Shun-juan YAN; Li-cai YANG
2012-01-01
The effect of weld reinforcement on axial plastic buckling of welded steel cylindrical shells is investigated through experimental and numerical buckling analysis using six welded steel cylindrical shell specimens.The relationship between the amplitude of weld reinforcement and the axial plastic buckling critical load is explored.The effect of the material yield strength and the number of circumferential welds on the axial plastic buckling is studied.Results show that circumferential weld reinforcement represents a severe imperfect form of axially compressed welded steel cylindrical shells and the axial plastic buckling critical load decreases with the increment of the mean amplitude of circumferential weld reinforcement.The material yield strength and the number of circumferential welds are found to have no significant effect on buckling waveforms; however,the axial plastic buckling critical load can be decreased to some extent with the increase of the number of circumferential welds.
Weak Formulation Study For Thermoelastic Buckling Analysis Of Thick Laminated Cylindrical Shells
Directory of Open Access Journals (Sweden)
Kewei Ding
2015-08-01
Full Text Available Weak formulations of mixed state equations of closed laminated cylindrical shells are presented in the Hamilton System. The Hamilton canonical equation of closed cylindrical shell is established. By means of applying the transfer matrix method and taking the advantage of Hamiltonian matrix in the calculation, a unified approach and three-dimensional thermoelastic solutions are obtained for the buckling analysis of closed thick laminated cylindrical shells. All equations of elasticity can be satisfied and all elastic constants can be taken into account. Numerical results are given to compare with those of FEM calculated using SAP5. The principle and method suggested here have clear physical concepts. The equations and boundary conditions proposed in this paper are weakened. The solutions and results given here may serve as a benchmark for other numerical procedures.
Electromagnetic Casimir densities for a cylindrical shell on de Sitter space
Saharian, A A; Saharyan, N A
2016-01-01
Complete set of cylindrical modes is constructed for the electromagnetic field inside and outside a cylindrical shell in the background of $(D+1)$% -dimensional dS spacetime. On the shell, the field obeys the generalized perfect conductor boundary condition. For the Bunch-Davies vacuum state, we evaluate the expectation values (VEVs) of the electric field squared and of the energy-momentum tensor. The shell-induced contributions are explicitly extracted. In this way, for points away from the shell, the renormalization is reduced to the one for the VEVs in the boundary-free dS bulk. As a special case, the VEVs are obtained for a cylindrical shell in the $(D+1)$% -dimensional Minkowski bulk. We show that the shell-induced contribution in the electric field squared is positive for both the interior and exterior regions. The corresponding Casimir-Polder forces are directed toward the shell. The vacuum energy-momentum tensor, in addition to the diagonal components, has a nonzero off-diagonal component correspondin...
Frederico Martins Alves da Silva; Augusta Finotti Brazão; Paulo Batista Gonçalves
2015-01-01
This work investigates the influence of Young’s modulus, shells thickness, and geometrical imperfection uncertainties on the parametric instability loads of simply supported axially excited cylindrical shells. The Donnell nonlinear shallow shell theory is used for the displacement field of the cylindrical shell and the parameters under investigation are considered as uncertain parameters with a known probability density function in the equilibrium equation. The uncertainties are discretized a...
Energy Technology Data Exchange (ETDEWEB)
Kelker, D.; Langenberg, C.W.
1988-08-01
A folded surface can be represented by the orientation of normals to the surface measured at several locations. When plotted on the unit sphere, the pattern of normals determines the type of fold. Poles from a cylindrical fold give a great circle on the unit sphere, whereas poles of a circular conical fold give a small circle, and poles from an elliptical conical fold give the projection of an ellipse onto the surface of the sphere. Several statistical tests that appear in the literature for classifying folds are discussed and compared. All but one of the tests use quantities obtained from an iterative least-squares procedure that fits the appropriate curve on the sphere. The classification procedure is illustrated with folds from the Canadian Rocky Mountains and uses for examples a cylindrical fold and a circular conical fold from the Smoky River coal field near Grande Cache, Alberta, and an elliptical conical fold near Jasper, Alberta. This methodology has resulted in new coal reserves in the Grande Cache area.
Circular-cylindrical flux-rope analytical model for Magnetic Clouds
Nieves-Chinchilla, Teresa; Linton, Mark; Hidalgo, Miguel A.; Vourlidas, Angelos; Savani, Neel P.; Szabo, Adam; Farrugia, Charlie; Yu, Wenyuan
2016-05-01
We present an analytical model to describe magnetic flux-rope topologies. When these structures are observed embedded in Interplanetary Coronal Mass Ejections (ICMEs) with a depressed proton temperature, they are called Magnetic Clouds ( MCs). The model extends the circular-cylindrical concept of Hidalgo et al. (2000) by introducing a general form for the radial dependence of the current density. This generalization provides information on the force distribution inside the flux rope in addition to the usual parameters of MC geometrical information and orientation.The generalized model provides flexibility for implementation in 3D MHD simulations. Here, we evaluate its performance in the reconstruction of MCs in in-situ observations. Four Earth directed ICME events, observed by the Wind spacecraft, are used to validate the technique. The events are selected from the ICME Wind list with the magnetic obstacle boundaries chosen consistently with the magnetic fi eld and plasma in situ observations and with a new parameter (EPP, Electron Pitch angle distribution Parameter) which quantifies the bidirectionally of theplasma electrons. The goodness of the fit is evaluated with a single correlation parameter to enable comparative analysis of the events. In general, at first glance, the model fits the selected events very well. However, a detailed analysis of events with signatures of significant compression indicates the need to explore geometries other than the circular-cylindrical.
Cylindrical acoustic levitator/concentrator having non-circular cross-section
Energy Technology Data Exchange (ETDEWEB)
Kaduchak, Gregory; Sinha, Dipen N.
2003-11-11
A low-power, inexpensive acoustic apparatus for levitation and/or concentration of aerosols and small liquid/solid samples having particulates up to several millimeters in diameter in air or other fluids is described. It is constructed from a commercially available, hollow piezoelectric crystal which has been formed with a cylindrical cross-section to tune the resonance frequency of the breathing mode resonance of the crystal to that of the interior cavity of the cylinder. When the resonance frequency of the interior cylindrical cavity is matched to the breathing mode resonance of the cylindrical piezoelectric transducer, the acoustic efficiency for establishing a standing wave pattern in the cavity is high. By deforming the circular cross-section of the transducer, the acoustic force is concentrated along axial regions parallel to the axis of the transducer. The cylinder does not require accurate alignment of a resonant cavity. The concentrated regions of acoustic force cause particles in the fluid to concentrate within the regions of acoustic force for separation from the fluid.
Free vibration analysis of rotating cylindrical shells using discrete singular convolution technique
International Nuclear Information System (INIS)
Free vibration analysis of rotating cylindrical shells is presented. Discrete singular convolution (DSC) method has been proposed for numerical solution of vibration problem. The formulations are based on Love's first approximation shell theory, and include the effects of initial hoop tension and centrifugal and Coriolis accelerations due to rotation. Frequencies are obtained for different types of boundary conditions and geometric parameters. In general, close agreement between the obtained results and those of other researchers has been found.
Temme, Michael W.
2003-01-01
CIVINS The thesis compares the analytical solution, two marine classification society design rules, and numerical analysis against experimental results for predicting the failure modes (general instability, axisymmetric buckling, and asymmetric collapse of the shell) and failure pressures of ring-stiffened cylindrical shells. The analytical solution is first summarized based on several sources. Design rules for the classification societies are then presented with brief explanations for e...
Non-linear Vibrations of Deep Cylindrical Shells by the p-Version Finite Element Method
Directory of Open Access Journals (Sweden)
Pedro Ribeiro
2010-01-01
Full Text Available A p-version shell finite element based on the so-called shallow shell theory is for the first time employed to study vibrations of deep cylindrical shells. The finite element formulation for deep shells is presented and the linear natural frequencies of different shells, with various boundary conditions, are computed. These linear natural frequencies are compared with published results and with results obtained using a commercial software finite element package; good agreement is found. External forces are applied and the displacements in the geometrically non-linear regime computed with the p-model are found to be close to the ones computed using a commercial FE package. In all numerical tests the p-FE model requires far fewer degrees of freedom than the regular FE models. A numerical study on the dynamic behaviour of deep shells is finally carried out.
Rose, Cheryl A.; Young, Richard D.; Starnes, James H., Jr.
1999-01-01
Results of a geometrically nonlinear finite element parametric study to determine curvature correction factors or "bulging factors" that account for increased stresses due to curvature for longitudinal cracks in unstiffened pressurized cylindrical shells are presented. Geometric parameters varied in the study include the shell radius, the shell wall thickness, and the crack length. The major results are presented in graphs of the bulging factor as a function of the applied load and as a function of geometric parameters that include the shell radius, the shell thickness and the crack length. The computed bulging factors are compared with solutions based on linear shallow shell theory, and with semi-empirical solutions that approximately account for the nonlinear deformation in the vicinity of the crack. The effect of biaxial loads on the computed bulging factors is also discussed.
Vibrational power flow of a finite cylindrical shell with discrete axial stiffeners
Institute of Scientific and Technical Information of China (English)
LIU Yanmei; HUANG Xieqing
2002-01-01
The structural wave power flows in an elastic finite cylindrical shell with discrete axial stiffeners are studied when a simple harmonic force is applied on it. The equations of motion of the shell are derived by using Flugge equation and Hamilton variational principle,and the responses of the shell are obtained. By use of the basic definition of the power flow, the characteristics of axial propagation of the power flow supplied by input structure and carried by different shell internal forces of a forced shell are investigated. The effects of parameters, such as relative location of driving force and stringer, driving force type and structural damping on the vibrational power flows in the shell, are discussed. These provide some theoretical bases for vibration control and noise reduction of this kind of structure.
Institute of Scientific and Technical Information of China (English)
薛明德; 王和慧; 陈伟; 黄克智
1999-01-01
The stress analysis based on the theory of a thin shell is carried out for cylindrical shells with normally intersecting nozzles subjected to external moment loads on the ends of shells with a large diameter ratio （ρ0≤0.8）. Instead of the Donnell shallow shell equation, the modified Morley equation, which is applicable to ρ0 （R/T）1/2（?）1, is used for the analysis of the shell with cutout. The solution in terms of displacement function for the nozzle with a nonplanar end is based on the Goldenveizer equation. The boundary forces and displacements at the intersection are all transformed from Gaussian coordinates （α, β） on the shell, or Gaussian coordinates （ζ, θ） on the nozzle into three-dimensional cylindrical coordinates （ρ, θ, z）. Their expressions on the intersecting curve are periodic functions of θ and expanded in Fourier series. Every harmonic of Fourier coefficients of boundary forces and displacements are obtained by numerical quadrature. The results obtained are in agreement with
Demagnetization factors for cylindrical shells and related shapes
Czech Academy of Sciences Publication Activity Database
Beleggia, M.; Vokoun, David; De Graef, M.
2009-01-01
Roč. 321, č. 9 (2009), s. 1306-1315. ISSN 0304-8853 EU Projects: European Commission(XE) 46559 - CERINKA Institutional research plan: CEZ:AV0Z10100520 Keywords : demagnetization factor * magnetostaticenergy * nano-ring * core-shell * dipolar interaction * shape anisotropy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.204, year: 2009
Institute of Scientific and Technical Information of China (English)
王吉; 王肖钧; 王峰; 赵凯
2004-01-01
With finite-element software ANSYS 7.0 and simple thermal-mechanical coupling constitutive relations,the buckling failure of preloaded cylindrical shell irradiated by high power laser beam was studied by numerical simulations. The buckling mode and buckling critical loading were analysed for different preloading conditions. The influence of laser intensity, beam irradiation time, preloading conditions and geometric parameters of cylindrical shell on the buckling mode were discussed. The numerical results show that: ① the buckling deformation of the cylindrical shell was concentrated in the area of laser spot and the radial buckling was the main buckling mode, ② a linear relationship between the buckling eigenvalue and the maximum temperature at the center of laser spot was approached, ③ the buckling failure of cylindrical shell was attributed to the coupling effect of the material softening and the radial deformation in the laser spot, and hence to raise the stiffness of the material would enhance the ability for anti-irradiation of structure substantially.
Thin Circular Disc Shells of Radio Sources Around Supernova Remnant G16.2-2.7
Institute of Scientific and Technical Information of China (English)
俞志尧
2002-01-01
We propose a new model of distinct thin circular disc shells to analyse the radio map of the supernova remnant (SNR) G16.2-2.7 from NRAO VLA Sky Survey at 1.4 GHz and the radio sources around it. It is obtained that the 20 radio sources around the SNR G16.2-2.7 distribute on the four thin circular disc shells. The results support the shell-like structure strongly and further indicate that the shell-like structure is several thin circular disc shells. Because the shell-like structure dominates the total sample, our result is important for research of the radio morphology of SNRs.
Buckling characteristic of multi-laminated composite elliptical cylindrical shells
Kassegne, Samuel Kinde; Chun, Kyoung-Sik
2015-03-01
Fiber-reinforced composite materials continue to experience increased adoption in aerospace, marine, automobile, and civil structures due to their high specific strength, high stiffness, and light weight. This increased use has been accompanied by applications involving non-traditional configurations such as compression members with elliptical cross-sections. To model such shapes, we develop and report an improved generalized shell element called 4EAS-FS through a combination of enhanced assumed strain and the substitute shear strain fields. A flat shell element has been developed by combining a membrane element with drilling degree-of-freedom and a plate bending element. We use the element developed to determine specifically buckling loads and mode shapes of composite laminates with elliptical cross-section including transverse shear deformations. The combined influence of shell geometry and elliptical cross-sectional parameters, fiber angle, and lay-up on the buckling loads of an elliptical cylinder is examined. It is hoped that the critical buckling loads and mode shapes presented here will serve as a benchmark for future investigations.
Enhanced thermal stability of functionally graded sandwich cylindrical shells by shape memory alloys
Asadi, H.; Akbarzadeh, A. H.; Chen, Z. T.; Aghdam, M. M.
2015-04-01
The present paper deals with the nonlinear thermal instability of geometrically imperfect sandwich cylindrical shells under uniform heating. The sandwich shells are made of a shape memory alloy (SMA)-fiber-reinforced composite and functionally graded (FG) face sheets (FG/SMA/FG). The Brinson phenomenological model is used to express the constitutive characteristics of SMA fibers. The governing equations are established within the framework of the third-order shear deformation shell theory by taking into account the von Karman geometrical nonlinearity and initial imperfection. The material properties of constituents are assumed to be temperature dependent. The Galerkin technique is utilized to derive expressions of the bifurcation points and bifurcation paths of the sandwich cylindrical shells. Using the developed closed-form solutions, extensive numerical results are presented to provide an insight into the influence of the SMA fiber volume fraction, SMA pre-strain, core thickness, non-homogeneity index, geometrical imperfection, geometry parameters of sandwich shells and temperature dependency of materials on the stability of shells. The results reveal that proper application of SMA fibers postpones the thermal bifurcation point and dramatically decreases thermal post-buckling deflection. Moreover, the induced tensile recovery stress of SMA fibers could also stabilize the geometrically imperfect shells during the inverse martensite phase transformation.
Active structural acoustic control of a smart cylindrical shell using a virtual microphone
Loghmani, Ali; Danesh, Mohammad; Kwak, Moon K.; Keshmiri, Mehdi
2016-04-01
This paper investigates the active structural acoustic control of sound radiated from a smart cylindrical shell. The cylinder is equipped with piezoelectric sensors and actuators to estimate and control the sound pressure that radiates from the smart shell. This estimated pressure is referred to as a virtual microphone, and it can be used in control systems instead of actual microphones to attenuate noise due to structural vibrations. To this end, the dynamic model for the smart cylinder is derived using the extended Hamilton’s principle, the Sanders shell theory and the assumed mode method. The simplified Kirchhoff-Helmholtz integral estimates the far-field sound pressure radiating from the baffled cylindrical shell. A modified higher harmonic controller that can cope with a harmonic disturbance is designed and experimentally evaluated. The experimental tests were carried out on a baffled cylindrical aluminum shell in an anechoic chamber. The frequency response for the theoretical virtual microphone and the experimental actual microphone are in good agreement with each other, and the results show the effectiveness of the designed virtual microphone and controller in attenuating the radiated sound.
Free vibration of composite skewed cylindrical shell panel by finite element method
Haldar, Salil
2008-03-01
In this paper a composite triangular shallow shell element has been used for free vibration analysis of laminated composite skewed cylindrical shell panels. In the present element first-order shear deformation theory has been incorporated by taking transverse displacement and bending rotations as independent field variables. The interpolation function used to approximate transverse displacement is one order higher than for bending rotations. This has made the element free from locking in shear. Two types of mass lumping schemes have been recommended. In one of the mass lumping scheme the effect of rotary inertia has been incorporated in the element formulations. Free vibration of skewed composite cylindrical shell panels having different thickness to radius ratios ( h/R=0.01-0.2), length to radius ratios ( L/R), number of layers and fiber orientation angles have been analyzed following the shallow shell method. The results for few examples obtained in the present analysis have compared with the published results. Some new results of composite skewed cylindrical shell panels have been presented which are expected to be useful to future research in this direction.
Young, Richard D.; Rose, Cheryl A.; Starnes, James H., Jr.
2000-01-01
Results of a geometrically nonlinear finite element parametric study to determine curvature correction factors or bulging factors that account for increased stresses due to curvature for longitudinal and circumferential cracks in unstiffened pressurized cylindrical shells are presented. Geometric parameters varied in the study include the shell radius, the shell wall thickness, and the crack length. The major results are presented in the form of contour plots of the bulging factor as a function of two nondimensional parameters: the shell curvature parameter, lambda, which is a function of the shell geometry, Poisson's ratio, and the crack length; and a loading parameter, eta, which is a function of the shell geometry, material properties, and the applied internal pressure. These plots identify the ranges of the shell curvature and loading parameters for which the effects of geometric nonlinearity are significant. Simple empirical expressions for the bulging factor are then derived from the numerical results and shown to predict accurately the nonlinear response of shells with longitudinal and circumferential cracks. The numerical results are also compared with analytical solutions based on linear shallow shell theory for thin shells, and with some other semi-empirical solutions from the literature, and limitations on the use of these other expressions are suggested.
Initial imperfection survey on a cylindrical shell at the Ultra-Centrifuge Nederland n.v
International Nuclear Information System (INIS)
The results of the initial imperfection survey of a circular shell, with an inner- and outer-skin made out of carbon fibres with an aluminium honey-comb in between, are presented. At UCN the shell is called the ''Demonstrator Model'' shortly the ''Demonstrator''. The modal components of the measured imperfection surface as a function of the circumferential and axial wave numbers are calculated. The characteristic imperfection distributions associated with the fabrication process used are presented. (orig.)
Kim, Young-Wann
2015-12-01
The free vibration characteristics of fluid-filled functionally graded cylindrical shells buried partially in elastic foundations are investigated by an analytical method. The elastic foundation of partial axial and angular dimensions is represented by the Pasternak model. The motion of the shells is represented by the first-order shear deformation theory to account for rotary inertia and transverse shear strains. The functionally graded cylindrical shells are composed of stainless steel and silicon nitride. Material properties vary continuously through the thickness according to a power law distribution in terms of the volume fraction of the constituents. The governing equation is obtained using the Rayleigh-Ritz method and a variation approach. The fluid is described by the classical potential flow theory. Numerical examples are presented and compared with existing available results to validate the present method.
Dispersion of axially symmetric waves in fluid-filled cylindrical shells
DEFF Research Database (Denmark)
Bao, X.L.; Überall, H.; Raju, P. K.;
2000-01-01
in striking contrast to the results for double (outside and inside) loading by two fluids of comparable density, where circumferential waves in both external and internal fluids were found, their interaction causing segmentation and repulsion phenomena of their dispersion curves. The condition of......Acoustic waves normally incident on an elastic cylindrical shell can cause the excitation of circumferential elastic waves on the shell. These shells may be empty and fluid immersed, or fluid filled in an ambient medium of air, or doubly fluid loaded inside and out. Circumferential waves on such......, 317 (1972)]. We have extended the work of Kumar to the case of fluid-filled aluminum shells and steel shells imbedded in air. These cases demonstrate the existence of circumferential waves traveling in the filler fluid, exhibiting a certain simplicity of the dispersion curves of these waves. This is...
CAPILLARY EFFECT ON VERTICALLY EXCITED SURFACE WAVE IN CIRCULAR CYLINDRICAL VESSEL
Institute of Scientific and Technical Information of China (English)
JIAN Yong-jun; E Xue-quan; ZHANG Jie
2006-01-01
In a vertically oscillating circular cylindrical container, singular perturbation theory of two-time scale expansions was developed in inviscid fluids to investigate the motion of single free surface standing wave including the effect of surface tension. A nonlinear slowly varying amplitude equation, which incorporates cubic nonlinear term,external excitation and the influence of surface tension, was derived from potential flow equation. The results show that, when forced frequency is lower, the effect of surface tension on mode selection of surface wave is not important. However, when forced frequency is higher, the surface tension can not be neglected. This proved that the surface tension causes free surface returning to equilibrium location. In addition, due to considering the effect of surface tension, the theoretical result approaches to experimental results much more than that of no surface tension.
Rayleigh-Taylor and Richtmyer-Meshkov Instabilities and Mixing in Stratified Cylindrical Shells
Energy Technology Data Exchange (ETDEWEB)
Mikaelian, K O
2004-04-15
We study the linear stability of an arbitrary number N of cylindrical concentric shells undergoing a radial implosion or explosion.We derive the evolution equation for the perturbation {eta}{sub i} at interface i; it is coupled to the two adjacent interfaces via {eta}{sub i{+-}1}. For N=2, where there is only one interface, we verify Bell's conjecture as to the form of the evolution equation for arbitrary {rho}{sub 1} and {rho}{sub 2}, the fluid densities on either side of the interface. We obtain several analytic solutions for the N=2 and 3 cases. We discuss freeze-out, a phenomenon that can occur in all three geometries (planar, cylindrical, or spherical), and ''critical modes'' that are stable for any implosion or explosion history and occur only in cylindrical or spherical geometries. We present numerical simulations of possible gelatin-ring experiments illustrating perturbation feedthrough from one interface to another. We also develop a simple model for the evolution of turbulent mix in cylindrical geometry and define a geometrical factor G as the ratio h{sub cylindrical}/h{sub planar} between cylindrical and planar mixing layers. We find that G is a decreasing function of R/R{sub o}, implying that in our model h{sub cylindrical} evolves faster (slower) than h{sub planar} during an implosion (explosion).
Study of the vibration of bulkhead-stiffened cylindrical shells by laser-based methods
Zhu, Ninghui
The first part of this dissertation work deals with an experimental study of the vibration behavior of bulkhead stiffened cylindrical shells by using laser-based vibration measurement methods. Holographic interferometry and laser speckle photography are first demonstrated on revealing the dynamic behavior of a 22 ft long cylindrical shell. These methods are thereafter further explored to study the vibration characteristic of cylindrical shells with different stiffeners such as a full bulkhead or a partial bulkhead. Many experimentally obtained holograms and specklegrams reveal interesting features of the vibration of bulkhead stiffened cylindrical shells. The experimentally obtained results are compared with those obtained from a finite element model developed by General Dynamic Electric Boat Division, and the finite element model is generally validated. Mode localization theory is used to explain some interesting findings in experiments and the reason of some discrepancies between the finite element analysis and experiment results. The presence of irregularities in a weakly coupled structure such as a bulkhead-stiffened cylindrical shell is shown to be able to localize the modes of vibration and inhibit the propagation of vibration within the shell. A numerical simulation based on the finite element modal analysis indicates the validation of this explanation of the experimental findings. Thereafter, the eigensolutions of disordered, plate-stiffened cylindrical shell stiffened are derived by the use of receptance method. Numerical calculations are thereafter performed based upon this model and indeed reveal the exist of localized vibration in this kind of structure. This analytical study provides physical insights into the mode localization phenomenon in stiffened cylindrical shell type of structures from a more systematic manner. The conditions and the effect of mode localization on natural frequencies and mode shapes of cylindrical shell structure are also
The Nonlinear Instability Modes of Dished Shallow Shells under Circular Line Loads
Directory of Open Access Journals (Sweden)
Liu Chang-Jiang
2011-01-01
Full Text Available This paper investigated the nonlinear stability problem of dished shallow shells under circular line loads. We derived the dimensionless governing differential equations of dished shallow shell under circular line loads according to the nonlinear theory of plates and shells and solved the governing differential equations by combing the free-parameter perturbation method (FPPM with spline function method (SFM to analyze the nonlinear instability modes of dished shallow shell under circular line loads. By analyzing the nonlinear instability modes and combining with concrete computational examples, we obtained the variation rules of the maximum deflection area of initial instability with different geometric parameters and loading action positions and discussed the relationship between the initial instability area and the maximum deflection area of initial instability. The results obtained from this paper provide some theoretical basis for engineering design and instability prediction and control of shallow-shell structures.
Effectiveness of the magnetostatic shielding by the cylindrical shells
Grabchikov, S. S.; Trukhanov, A. V.; Trukhanov, S. V.; Kazakevich, I. S.; Solobay, A. A.; Erofeenko, V. T.; Vasilenkov, N. A.; Volkova, O. S.; Shakin, A.
2016-01-01
The experimental research of the magnetostatic shielding effectiveness and the analytical calculations of the average magnetic permeability of single-layer cylindrical sample of the shields based on electrolytically deposited Ni80Fe20 alloy are carried out. The locations of maxima on the Ef(H) and μ(H) curves do not match each other, which is difficult to interpret in terms of the shunting model. The results are explained by the non-linear distribution of the magnetic permeability through the thickness of the shield. It has been shown that in the magnetic fields range from 100 A/m up to 2700 A/m, the shields based on the Ni80Fe20 alloy are preferred over ones based on the 84KHSR amorphous ribbon. It is concluded that at the selection of shield materials it should take into account not only the main magnetic characteristics - μ; Hs; Hc but also Hmax parameter, which is important to evaluate the effectiveness of magnetic shielding.
Characterization of plasticity and fracture of shell casing of lithium-ion cylindrical battery
Zhang, Xiaowei; Wierzbicki, Tomasz
2015-04-01
Most of the literature on lithium-ion battery cells is concerned with modeling of jellyroll with little attention to properties of shell casing. However, shell casing provides substantial strength and fracture resistance under mechanical loading and therefore must be an important part of modeling of lithium-ion batteries. The paper reports on a comprehensive test program on commercially available empty shell casing of 18650 lithium-ion cylindrical cells. Part of the tests was used to determine plastic and fracture properties from sub-size specimens cut from lateral part of the cans. The other part served to validate plasticity and fracture models under various loading conditions. The associated flow rule was used to simulate plasticity behavior and Modified Mohr-Coulomb (MMC) fracture model was adopted to predict crack initiation and propagation of shell casing. Simulation results confirmed that present plasticity and fracture models could predict global plastic behavior of the cells under different loading conditions. The jellyroll model with volumetric hardening was introduced to compare the performance of empty shell casing, bare jellyroll and complete battery cell. It was shown that in many loading situations, for example, three point bending of the cylindrical cells, the metallic shell casing provides most of mechanical resistance.
Modal analysis of thin cylindrical shells with cardboard liners and estimation of loss factors
Koruk, Hasan; Dreyer, Jason T.; Singh, Rajendra
2014-04-01
Cardboard liners are often installed within automotive drive shafts to reduce radiated noise over a certain frequency range. However, the precise mechanisms that yield noise attenuation are not well understood. To overcome this void, a thin shell (under free boundaries) with different cardboard liner thicknesses is examined using analytical, computational and experimental methods. First, an experimental procedure is introduced to determine the modal behavior of a cylindrical shell with a cardboard liner. Then, acoustic and vibration frequency response functions are measured in acoustic free field, and natural frequencies and the loss factors of structures are determined. The adverse effects caused by closely spaced modes during the identification of modal loss factors are minimized, and variations in measured natural frequencies and loss factors are explored. Material properties of a cardboard liner are also determined using an elastic plate treated with a thin liner. Finally, the natural frequencies and modal loss factors of a cylindrical shell with cardboard liners are estimated using analytical and computational methods, and the sources of damping mechanisms are identified. The proposed procedure can be effectively used to model a damped cylindrical shell (with a cardboard liner) to predict its vibro-acoustic response.
Investigating the transitional state between circular plates and shallow spherical shells
Moayyad Al-Nasra; Mohamad Daoud
2015-01-01
The stiffness of circular plates can be increased by inducing a rise at the center of these plates; this rise converts the circular plates from two-dimensional stiffness elements into three-dimensional stiffness elements. This slight change in the geometry shifts the state of stresses from mainly bending stresses to tensilecompressive stresses. The rise at the center of a circular plate is increased gradually to the point where a shell element is formed. This paper focuses on this particul...
Energy Technology Data Exchange (ETDEWEB)
Villalobos Mendoza, Brenda; Cordero Davila, Alberto [Benemerita Universidad Autonoma de Puebla, 4 Sur 104 Centra Historico C.P. 72000, Puebla, Pue. (Mexico); Gonzalez Garcia, Jorge, E-mail: bvillalobosmendoza@gmail.com [Universidad Tecnologica de la Mixteca, Carretera Huajuapan-Acatlima, Km 2.5, CP. 6900, Huajuapan de Leon, Oaxaca (Mexico)
2011-01-01
This paper describes the construction of an elliptical-cylindrical model without spherical aberration using vertical rotating tools. The engine of the circular tool is placed on one arm so that the tool fits on the surface and this in turn is moved by an X-Y table. The test method and computer algorithms that predict the desired wear are described.
International Nuclear Information System (INIS)
This paper describes the construction of an elliptical-cylindrical model without spherical aberration using vertical rotating tools. The engine of the circular tool is placed on one arm so that the tool fits on the surface and this in turn is moved by an X-Y table. The test method and computer algorithms that predict the desired wear are described.
International Nuclear Information System (INIS)
In this paper, an analytical approach to the static behavior of functionally graded material (FGM) cylindrical shells with simply supported edges is developed. The Poisson's ratios of the FGM shell are assumed to be constant, but it is the modulus of elasticity which varies continuously through the radial direction according to the exponential function. The shell has finite length and embedded piezoelectric layers. The partial differential equilibrium equations as well as the stress–displacement relations are reduced to the ordinary one with constant coefficient by using the Fourier series expansion. Finally, the problem is solved by using the state space method. Numerical results are given to demonstrate the accuracy of the presented method. The influences of the gradient index, applied voltage and radius to thickness ratios on the static behavior of FGM shells are also studied
International Nuclear Information System (INIS)
This paper presents an investigation on the nonlinear dynamic response of piezoelectric cylindrical shells reinforced with boron nitride nanotubes (BNNTs) under a combined axisymmetric electro-thermo-mechanical loading. By employing the classical Donnell shell theory, the von Kármán–Donnell kinematic relationship, and a piezo-elastic constitutive law including thermal effects, the nonlinear governing equations of motion of the shell are derived through the Reissner variational principle. The finite difference method and a time-integration scheme are used to obtain the nonlinear dynamic response of the BNNT-reinforced piezoelectric shell. A parametric study is conducted, showing the effects of geometrically nonlinear deformation, applied voltage, temperature change, mechanical load, BNNT volume fraction and boundary conditions on the nonlinear dynamic response. (paper)
Free Vibration Characteristics of Cylindrical Shells Using a Wave Propagation Method
Directory of Open Access Journals (Sweden)
A. Ghoshal
2001-01-01
Full Text Available In the present paper, concept of a periodic structure is used to study the characteristics of the natural frequencies of a complete unstiffened cylindrical shell. A segment of the shell between two consecutive nodal points is chosen to be a periodic structural element. The present effort is to modify Mead and Bardell's approach to study the free vibration characteristics of unstiffened cylindrical shell. The Love-Timoshenko formulation for the strain energy is used in conjunction with Hamilton's principle to compute the natural propagation constants for two shell geometries and different circumferential nodal patterns employing Floquet's principle. The natural frequencies were obtained using Sengupta's method and were compared with those obtained from classical Arnold-Warburton's method. The results from the wave propagation method were found to compare identically with the classical methods, since both the methods lead to the exact solution of the same problem. Thus consideration of the shell segment between two consecutive nodal points as a periodic structure is validated. The variations of the phase constants at the lower bounding frequency for the first propagation band for different nodal patterns have been computed. The method is highly computationally efficient.
Institute of Scientific and Technical Information of China (English)
TAO Meng; FAN Jun; TANG Weilin
2009-01-01
The effect of multiple compliant layers on sound radiation from a finite cylindrical shell immersed in an infinite acoustic medium is studied. The transfer matrix is derived according to the continuous boundary conditions at each adjacent interface of the multi-layer system.With the shell theory and the acoustic wave equation, the theoretical model is developed to estimate the characteristics of sound radiation. The numerical calculation results show that the amount of the acoustic radiation power reduction increases as the wave speed or the density of the compliant layer decreases, and using multi-layer system could be more effective on noise reduction than the corresponding uniform single layer.
Analyses of a Dipole Antenna Loaded by a Cylindrical Shell of Double Negative (DNG Metamaterial
Directory of Open Access Journals (Sweden)
Khan M. Z. Shams
2007-10-01
Full Text Available The current distribution, input impedance, and radiation pattern of a cylindrical dipole antenna enclosed by a thin cylindrical shell of double negative (DNG metamaterial are computed using the piecewise sinusoidal Galerkin formulation. In the presence of the DNG shell, the dipole antenna exhibits three interesting characteristics. The input impedance shows potentials for wide bandwidth due to the relative insensitivity of the impedance with frequency. Within specific ranges of DNG material parameter values, the dipole shows resonance at much lower frequencies than its resonant frequency in free space. The dipole does not show change in the direction of the principal beam nor does it show signs of beam splitting and side lobes even when the antenna length approaches one and a half wavelength.
LOAD CARRYING CAPABILITY OF LIQUID FILLED CYLINDRICAL SHELL STRUCTURES UNDER AXIAL COMPRESSION
Directory of Open Access Journals (Sweden)
QASIM H. SHAH
2011-08-01
Full Text Available Empty and water filled cylindrical Tin (Sn coated steel cans were loaded under axial compression at varying loading rates to study their resistance to withstand accidental loads. Compared to empty cans the water filled cans exhibit greater resistance to axially applied compression loads before a complete collapse. The time and load or stroke and load plots showed three significant load peaks related to three stages during loading until the cylinder collapse. First peak corresponds to the initial structural buckling of can. Second peak occurs when cylindrical can walls gradually come into full contact with water. The third peak shows the maximum load carrying capability of the structure where pressurized water deforms the can walls into curved shape until can walls fail under peak pressure. The collapse process of water filled cylindrical shell was further studied using Smooth Particle Hydrodynamics (SPH technique in LSDYNA. Load peaks observed in the experimental work were successfully simulated which substantiated the experimental work.
Stress of anisotropic structure vaults consisting of cylindrical shells. Part I
International Nuclear Information System (INIS)
A method is described for the numerical solution of problems based on analytical relations derived for bending deformation of a cylindrical shell stressed with radially flat, rotationally asymmetrical loads. The relations are expressed and processed by a matrix representation suitable for cascade-type calculation with free parameters and for computer processing. The method thus permits the designing of vaults of arbitrary eccentricities and variable thicknesses. A vault of this particular type is fairly common in nuclear reactor constructions. (M.S.)
International Nuclear Information System (INIS)
The graduated cylindrical shell (GCS) model developed by Thernisien et al. has been used with the goal of studying the three-dimensional morphology, position, and kinematics of coronal mass ejections observed by coronagraphs. These studies focused more on the results rather than the details of the model itself. As more researchers begin to use the model, it becomes necessary to provide a deeper discussion on how it is derived, which is the purpose of this paper. The model is built using the following features and constraints: (1) the legs are conical, (2) the front is pseudo-circular, (3) the cross section is circular, and (4) it expands in a self-similar way. We derive the equation of the model from these constraints. We also show that the ice-cream cone model is a limit of the GCS when the two legs overlap completely. Finally, we provide formulae for the calculation of various geometrical dimensions, such as angular width and aspect ratio, as well as the pseudo-code that is used for its computer implementation.
Gonçalves, P. B.; Silva, F. M. A.; Del Prado, Z. J. G. N.
2008-08-01
In formulating mathematical models for dynamical systems, obtaining a high degree of qualitative correctness (i.e. predictive capability) may not be the only objective. The model must be useful for its intended application, and models of reduced complexity are attractive in many cases where time-consuming numerical procedures are required. This paper discusses the derivation of discrete low-dimensional models for the nonlinear vibration analysis of thin cylindrical shells. In order to understand the peculiarities inherent to this class of structural problems, the nonlinear vibrations and dynamic stability of a circular cylindrical shell subjected to static and dynamic loads are analyzed. This choice is based on the fact that cylindrical shells exhibit a highly nonlinear behavior under both static and dynamic loads. Geometric nonlinearities due to finite-amplitude shell motions are considered by using Donnell's nonlinear shallow-shell theory. A perturbation procedure, validated in previous studies, is used to derive a general expression for the nonlinear vibration modes and the discretized equations of motion are obtained by the Galerkin method using modal expansions for the displacements that satisfy all the relevant boundary and symmetry conditions. Next, the model is analyzed via the Karhunen-Loève expansion to investigate the relative importance of each mode obtained by the perturbation solution on the nonlinear response and total energy of the system. The responses of several low-dimensional models are compared. It is shown that rather low-dimensional but properly selected models can describe with good accuracy the response of the shell up to very large vibration amplitudes.
Analysis of Experimental Research on Cyclones with Cylindrical and Spiral Shells
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Aleksandras Chlebnikovas
2012-12-01
Full Text Available The conducted investigation is aimed at providing information on air flow parameters in the cylindrical and spiral shell (devices are designed for separating solid particles from air flow having tangent flow inlet. Experimental research has employed multi-cyclones created by the Department of Environmental Protection at Vilnius Gediminas Technical University. The study is focused on investigating and comparing the distribution of the dynamic pressure of the airflow in six-channel cyclones inside the structures of devices. The paper establishes and estimates the efficiency of air cleaning changing air phase parameters using different particulate matters. The efficiency of the cyclone has been defined applying the weighted method based on LAND 28-98/M-08 methodology. The article presents the results of experimental research on the air cleaning efficiency of cylindrical and spiral shells using 20 µm glass and clay particulate matter under the initial concentration that may vary from 500 mg/m3 to 15 g/m3 using semi-rings with windows at different positions. The obtained results has shown that the maximum efficiency of the cylindrical shell increases up to 87,3 % while the initial concentration of glass makes 15 g/m3.Article in Lithuanian
Parametric Analysis of A Submerged Cylindrical Shell Subjected to Shock Waves
Institute of Scientific and Technical Information of China (English)
LI Shang-ming; FAN Sau-Cheong
2007-01-01
In this study,an FEM-SBFEM (scaled boundary finite element method) coupling procedure proposed by Fan et al.(2005) is adopted to obtain the dynamic responses of a submerged cylindrical shell subjected to plane step or exponential acoustic shock waves.The coupling procedure can readily be applied to three-dimensional problem,however for clarity,the problems to be presented are limited to two-dimensional domain.In the analyses,the cylindrical shell is modeled by simple beam elements (using FEM),while the effects of the surrounding infinite fluid is modeled by the SBFEM.In it,no free surface and seabed are involved.Compared with Fan and his co-authors' works,the FEM-SBFEM coupling procedure is further verified to be feasible for shock waves by benchmark examples.Furthermore,parametric studies are performed and presented to gain insight into effects of the geometric and material properties of the cylindrical shell on its dynamic responses.
International Nuclear Information System (INIS)
Cavitation problems in plant's piping system have been investigated on the basis of high-speed observation. Cavitation is one of the important factors with potential damage in piping system at nuclear power plant. In a power plant, there is cavitation occurrence to be expected in some local places such as an orifice, a valve and a pressure reducer. We have investigated about unsteady behavior and impact of cavitation in a long orifice with an abruptly expanding pipe. In this study, some detailed cavitation behaviors are observed by varying cavitating condition in the orifice throat and downstream of the orifice. High-speed behaviors of cavitation are observed by means of a high-speed video camera with a laser sheet in order to observe the inside of the circular orifice. Then images are analyzed using a frame difference method. As a result, we observe a series of cavitation developing process with decrease in cavitation number such as 1: cavitation inception occurs at the inlet of orifice, 2: cavitation develops in the throat of the orifice, 3: large-scale cavitation clouds appear downstream of the orifice, 4: liquid jet appears when the pressure downstream of the orifice decrease to about vapor pressure. Cavitation clouds in a circular cylindrical orifice with abruptly expanding part show some unsteadiness even in the steady operating condition. Cavitation clouds also show a large-scale shedding behavior in the transition stage to a liquid jet condition. In addition, we observe that the interface instability of a liquid jet downstream of the orifice depends on the cavitation instability in the orifice throat. (author)
LOW-FREQUENCY MAGNETIC FIELD SHIELDING BY A CIRCULAR PASSIVE LOOP AND CLOSED SHELLS
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V.S. Grinchenko
2016-05-01
Full Text Available Purpose. To analyze the shielding factors for a circular passive loop and conductive closed shells placed in a homogeneous low-frequency magnetic field. Methodology. We have obtained simplified expressions for the shielding factors for a circular passive loop and a thin spherical shell. In addition, we have developed the numerical model of a thin cubical shell in a magnetic field, which allows exploring its shielding characteristics. Results. We have obtained dependences of the shielding factors for passive loops and shells on the frequency of the external field. Analytically determined frequency of the external magnetic field, below which field shielding of a passive loop is expedient to use, above which it is advisable to use a shielding shell.
Mahadev, Sthanu
Continued research and development efforts devoted in recent years have generated novel avenues towards the advancement of efficient and effective, slender laminated fiber-reinforced composite members. Numerous studies have focused on the modeling and response characterization of composite structures with particular relevance to thin-walled cylindrical composite shells. This class of shell configurations is being actively explored to fully determine their mechanical efficacy as primary aerospace structural members. The proposed research is targeted towards formulating a composite shell theory based prognosis methodology that entails an elaborate analysis and investigation of thin-walled cylindrical shell type laminated composite configurations that are highly desirable in increasing number of mechanical and aerospace applications. The prime motivation to adopt this theory arises from its superior ability to generate simple yet viable closed-form analytical solution procedure to numerous geometrically intense, inherent curvature possessing composite structures. This analytical evaluative routine offers to acquire a first-hand insight on the primary mechanical characteristics that essentially govern the behavior of slender composite shells under typical static loading conditions. Current work exposes the robustness of this mathematical framework via demonstrating its potential towards the prediction of structural properties such as axial stiffness and bending stiffness respectively. Longitudinal ply-stress computations are investigated upon deriving the global stiffness matrix model for composite cylindrical tubes with circular cross-sections. Additionally, this work employs a finite element based numerical technique to substantiate the analytical results reported for cylindrically shaped circular composite tubes. Furthermore, this concept development is extended to the study of thin-walled, open cross-sectioned, curved laminated shells that are geometrically
Vibration analysis of axisymmetric and beam like cylindrical shells containing flowing fluid
International Nuclear Information System (INIS)
The free vibration characteristics of anisotropic laminated thin cylindrical shells partially or completely filled with liquid or subjected to a flowing fluid are studied in this work for two circumferential wave number n=0, axisymmetric, and n=1, beam-like. The shear deformation effects are taken into account in this theory therefore the equations of motion are determined with displacements and transverse shear as independent variables. The present method is a combination of finite element analysis and refined shell theory in which the displacement functions are derived from the exact solution of refined shell equations based on orthogonal curvilinear coordinates. Mass and stiffness matrices are determined by precise analytical integration. A finite element is developed for the liquid in case of potential flow which yields three forces (inertial, centrifugal and Coriolis) of moving fluid. The mass, stiffness and damping matrices due to the fluid effect are obtained by an analytical integration of the fluid pressure over the liquid element. The available solution based on the Sanders' theory is also obtained from the present theory in the limiting case of the transverse shear rigidities. The natural frequencies of the isotropic and anisotropic cylindrical shells in cases of empty, partially or completely filled with liquid as well as subjected to a flowing fluid are given and compared with the corresponding results of existing available theories, very good agreement is obtained. (authors)
Thermal stresses in a spherical shell with a circular elastic inclusion
International Nuclear Information System (INIS)
Thermal stress analysis of a spherical shell with a circular elastic inclusion is presented. Using Reissner's theory for thin shallow spherical shells, displacements and stresses are obtained in the shell and the inclusion in terms of Hankel and Bessel function. The thermal loading is assumed to be given by a temperature which is uniform on the inner and outer surfaces of the shell and the inclusion but may vary linearly across the thickness. The thermal stress problem is converted into an equivalent static loading problem. The satisfaction of the boundary conditions at the shell inclusion junction leads to the evaluation of the unknowns in the solutions. Results obtained show the inadequacy of flat plate solutions and the effect of curvature. The effect of various parameters of the problem such as elastic moduli, coefficients of linear expansion, curvature parameters is studied. Limiting cases of a rigid circular inclusion either free to move with the shell or clamped are also considered and the results are compared with the existing analytical solutions. Stress concentrations that are developed are presented in graphical form which is useful in the design of spherical shells containing a rigid or an elastic inclusion. It is found that a clamped rigid inclusion results in a more severe stress concentration than a rigid inclusion free to move with the shell. The maximum principal stress in a uniformly heated spherical shell with a circular elastic inclusion is found to be tensile in the shell and compressive in the inclusion. An increase in Esub(c)/Esub(s) or αsub(c)/αsub(s) (Esub(c), αsub(c), Esub(s), αsub(s) are the elastic modulus and coefficient of linear expansion of the inclusion and the shell material, respectively) causes an increase in the shell stresses and a reduction in the inclusion stresses
INTERNAL RESONANT INTERACTIONS OF THREE FREE SURFACE-WAVES IN A CIRCULAR CYLINDRICAL BASIN
Institute of Scientific and Technical Information of China (English)
马晨明
2003-01-01
The basic equations of free capillary-gravity surface-waves in a circular cylindrical basin were derived from Luke' s principle. Taking Galerkin ' s expansion of the velocity potential and the free surface elevation, the second-order perturbation equations were derived by use of expansion of multiple scale. The nonlinear interactions with the second order internal resonance of three free surface-waves were discussed based on the above. The results include:derivation of the couple equations of resonant interactions among three waves and the conservation laws; analysis of the positions of equilibrium points in phase plane; study of the resonant parameters and the non-resonant parameters respectively in all kinds of circumstances; derivation of the stationary solutions of the second-order interaction equations corresponding to different parameters and analysis of the stability property of the solutions; discussion of the effective solutions only in the limited time range. The analysis makes it clear that the energy transformation mode among three waves differs because of the different initial conditions under nontrivial circumstance. The energy may either exchange among three waves periodically or damp or increase in single waves.
Extension, inflation and torsion of a residually stressed circular cylindrical tube
Merodio, José; Ogden, Ray W.
2016-03-01
In this paper, we provide a new example of the solution of a finite deformation boundary-value problem for a residually stressed elastic body. Specifically, we analyse the problem of the combined extension, inflation and torsion of a circular cylindrical tube subject to radial and circumferential residual stresses and governed by a residual-stress dependent nonlinear elastic constitutive law. The problem is first of all formulated for a general elastic strain-energy function, and compact expressions in the form of integrals are obtained for the pressure, axial load and torsional moment required to maintain the given deformation. For two specific simple prototype strain-energy functions that include residual stress, the integrals are evaluated to give explicit closed-form expressions for the pressure, axial load and torsional moment. The dependence of these quantities on a measure of the radial strain is illustrated graphically for different values of the parameters (in dimensionless form) involved, in particular the tube thickness, the amount of torsion and the strength of the residual stress. The results for the two strain-energy functions are compared and also compared with results when there is no residual stress.
Vertically forced surface wave in weakly viscous fluids bounded in a circular cylindrical vessel
Institute of Scientific and Technical Information of China (English)
Jian Yong-Jun; E Xue-Quan
2004-01-01
Two-time scale perturbation expansions were developed in weakly viscous fluids to investigate surface wave motions by linearizing the Navier-Stokes equation in a circular cylindrical vessel which is subject to a vertical oscillation. The fluid field was divided into an outer potential flow region and an inner boundary layer region. A linear amplitude equation of slowly varying complex amplitude, which incorporates a damping term and external excitation, was derived for the weakly viscid fluids. The condition for the appearance of stable surface waves was obtained and the critical curve was determined. In addition, an analytical expression for the damping coefficient was determined and the relationship between damping and other related parameters (such as viscosity, forced amplitude, forced frequency and the depth of fluid, etc.) was presented. Finally, the influence both of the surface tension and the weak viscosity on the mode formation was described by comparing theoretical and experimental results. The results show that when the forcing frequency is low, the viscosity of the fluid is prominent for the mode selection. However, when the forcing frequency is high, the surface tension of the fluid is prominent.
Directory of Open Access Journals (Sweden)
Ali Nouri
2014-01-01
Full Text Available The maximizing of sound transmission loss (TL across a functionally graded material (FGM cylindrical shell has been conducted using a genetic algorithm (GA. To prevent the softening effect from occurring due to optimization, the objective function is modified based on the first resonant frequency. Optimization is performed over the frequency range 1000–4000 Hz, where the ear is the most sensitive. The weighting constants are chosen here to correspond to an A-weighting scale. Since the weight of the shell structure is an important concern in most applications, the weight of the optimized structure is constrained. Several traditional materials are used and the result shows that optimized shells with aluminum-nickel and aluminum-steel FGM are the most effective at maximizing TL at both stiffness and mass control region, while they have minimum weight.
Influence of transverse shear on plasticity around an axial crack in a cylindrical shell
International Nuclear Information System (INIS)
The paper presents a plasticity model for deep axial surface cracks in pressurized pipes. The model is used in an investigation of the relative merits of fracture criteria based on COD and plastic instability. Recent investigations have shown that the inconsistency of the singular bending stress field in an axially cracked cylindrical shell arising from use of classical 8th order shallow shell theory is removed, when use is made of a 10th order shell theory, which accounts for transverse shear deformations. Although the membrane stresses are only moderately affected, the influence on the bending stresses is considerable. In the case of surface cracks moments are induced to the eccentricity of the crack, and transverse shear effects should therefore be included. (Auth.)
Sound scattering by free surface piercing and fluid-loaded cylindrical shells.
Avital, Eldad J; Miloh, Touvia
2011-07-28
A vertical flexible, thin, cylindrical shell is considered to be clamped to a rigid base in shallow water and piercing its surface. The shell is composed of an isotropic and homogeneous material and may be empty inside or filled with compressible fluid. Linear acoustics and structural dynamics are used to model sound scattering caused by an external incident sound wave. A solution is derived using a Fourier transform in the tangential and vertical directions. A collocation technique coupled with an orthogonalization procedure is used to account for the edge conditions of the shell. It is shown that zero sound scattering, indicating acoustic invisibility, is theoretically attainable and can be achieved when a continuous distribution of an oscillating pressure load is applied on the shell's wall. Similarly, zero sound transmission into the shell's inner fluid can also be considered. The possibility of using a pre-determined discrete distribution of the applied pressure load is also discussed. The derived equations are numerically solved to examine sound scattering by a thin aluminium shell in shallow water. PMID:21690137
Wave motion of a compressible viscous fluid contained in a cylindrical shell
Energy Technology Data Exchange (ETDEWEB)
Terhune, J.H.; Karim-Panahi, K. (General Electric Co., San Jose, CA (United States). GE Nuclear Energy)
1993-08-01
The free vibration of cylindrical shells filled with a compressible viscous fluid has been studied by numerous workers using the linearized Navier-Stokes equations, the fluid continuity equation, and Fluegge's equations of motion for thin shells. It happens that solutions can be obtained for which the interface conditions at the shell surface are satisfied. Formally, a characteristic equation for the system eigenvalues can be written down, and solutions are usually obtained numerically providing some insight into the physical mechanisms. In this paper, the authors modify the usual approach to this problem, use a more rigorous mathematical solution and limit the discussion to a single thin shell of infinite length and finite radius, totally filled with a viscous, compressible fluid. It is shown that separable solutions are obtained only in a particular gage, defined by the divergence of the fluid velocity vector potential, and the solutions are unique to that gage. Numerical results are obtained for the first few wave modes of a large shell, which illustrate the general approach to the solution. The wave phase velocity is related to the real part of the axial wave number and turns out to be independent of frequency, with numerical value lying between the sonic velocities in the fluid and the shell. The frequency dependencies of these parameters and fluid velocity mode shapes are computed for a typical case and displayed in nondimensional graphs.
Generalized asymptotic expansions for coupled wavenumbers in fluid-filled cylindrical shells
Kunte, M. V.; Sarkar, Abhijit; Sonti, Venkata R.
2010-12-01
Analytical expressions are found for the coupled wavenumbers in an infinite fluid-filled cylindrical shell using the asymptotic methods. These expressions are valid for any general circumferential order ( n). The shallow shell theory (which is more accurate at higher frequencies) is used to model the cylinder. Initially, the in vacuo shell is dealt with and asymptotic expressions are derived for the shell wavenumbers in the high- and the low-frequency regimes. Next, the fluid-filled shell is considered. Defining a relevant fluid-loading parameter μ, we find solutions for the limiting cases of small and large μ. Wherever relevant, a frequency scaling parameter along with some ingenuity is used to arrive at an elegant asymptotic expression. In all cases, Poisson's ratio ν is used as an expansion variable. The asymptotic results are compared with numerical solutions of the dispersion equation and the dispersion relation obtained by using the more general Donnell-Mushtari shell theory ( in vacuo and fluid-filled). A good match is obtained. Hence, the contribution of this work lies in the extension of the existing literature to include arbitrary circumferential orders ( n).
Experiments and analysis on chaotic vibrations of a shallow cylindrical shell-panel
Nagai, K.; Maruyama, S.; Murata, T.; Yamaguchi, T.
2007-08-01
Detailed experimental results and analytical results are presented on chaotic vibrations of a shallow cylindrical shell-panel subjected to gravity and periodic excitation. The shallow shell-panel with square boundary is simply supported for deflection. In-plane displacement at the boundary is elastically constrained by in-plain springs. In the experiment, the cylindrical shallow shell-panel with thickness 0.24 mm, square form of length 140 mm and mean radius 5150 mm is used for the test specimen. All edges around the shell boundary are simply supported by adhesive flexible films. First, to find fundamental properties of the shell-panel, linear natural frequencies and characteristics of restoring force of the shell-panel are measured. These results are compared with the relevant analytical results. Then, geometrical parameters of the shell-panel are identified. Exciting the shell-panel with lateral periodic acceleration, nonlinear frequency responses of the shell-panel are obtained by sweeping the frequency of periodic acceleration. In typical ranges of the exciting frequency, predominant chaotic responses are generated. Time histories of the responses are recorded for inspection of the chaos. In the analysis, the Donnell equation with lateral inertia force is introduced. Assuming mode functions, the governing equation is reduced to a set of nonlinear ordinary differential equations by the Galerkin procedure. Periodic responses are calculated by the harmonic balance method. Chaotic responses are integrated numerically by the Runge-Kutta-Gill method. The chaotic responses, which are obtained by the experiment and the analysis, are inspected with the Fourier spectra, the Poincaré projections, the maximum Lyapunov exponents and the Lyapunov dimension. It is found that the dominant chaotic responses of the shell-panel are generated from the responses of the sub-harmonic resonance of {1}/{2} order and of the ultra-sub-harmonic resonance of {2}/{3} order. By the
Directory of Open Access Journals (Sweden)
Khudayarov B. A.
2010-09-01
Full Text Available In this work is investigated the flutter of visco-elastic cylindrical shells streamlined by gas current. The basic direction of work is consisted in taking into account of visco-elastic material’s properties at supersonic speeds. Critical speeds for shell flutter are defined.
Khudayarov B.A.
2010-01-01
In this work is investigated the flutter of visco-elastic cylindrical shells streamlined by gas current. The basic direction of work is consisted in taking into account of visco-elastic material’s properties at supersonic speeds. Critical speeds for shell flutter are defined.
Vibration characteristics of thin rotating cylindrical shells with various boundary conditions
Sun, Shupeng; Chu, Shiming; Cao, Dengqing
2012-08-01
An analysis is presented for the vibration characteristics of thin rotating cylindrical shells with various boundary conditions by use of Fourier series expansion method. Based on Sanders' shell equations, the governing equations of motion which take into account the effects of centrifugal and Coriolis forces as well as the initial hoop tension due to rotating are derived. The displacement field is expressed as a product of Fourier series expressions which represents the axial modal displacements and trigonometric functions which represents the circumferential modal displacements. Stokes' transformation is employed to derive the derivatives of the Fourier series expressions. Then, through the process of formula derivation, an explicit expression of the exact frequency equation can be obtained for a thin rotating cylinder with classical boundary conditions of any type. Once the frequency equation has been determined, the frequencies are calculated numerically. To validate the present analysis, comparisons between the results of the present method and previous studies are performed and very good agreement is achieved. Finally, the method is applied to investigate the vibration characteristics of thin rotating cylindrical shells under various boundaries, and the results are presented.
Torki, Mohammad Ebrahim; Kazemi, Mohammad Taghi; Reddy, Junuthula N.; Haddadpoud, Hassan; Mahmoudkhani, Saeid
2014-02-01
In this paper, flutter of functionally graded material (FGM) cylindrical shells under distributed axial follower forces is addressed. The first-order shear deformation theory is used to model the shell, and the material properties are assumed to be graded in the thickness direction according to a power law distribution using the properties of two base material phases. The solution is obtained by using the extended Galerkin's method, which accounts for the natural boundary conditions that are not satisfied by the assumed displacement functions. The effect of changing the concentrated (Beck's) follower force into the uniform (Leipholz's) and linear (Hauger's) distributed follower loads on the critical circumferential mode number and the minimum flutter load is investigated. As expected, the flutter load increases as the follower force changes from the so-called Beck's load into the so-called Leipholz's and Hauger's loadings. The increased flutter load was calculated for homogeneous shell with different mechanical properties, and it was found that the difference in elasticity moduli bears the most significant effect on the flutter load increase in short, thick shells. Also, for an FGM shell, the increase in the flutter load was calculated directly, and it was found that it can be derived from the simple power law when the corresponding increase for the two base phases are known.
Directory of Open Access Journals (Sweden)
Gangolu Vijay Kumar
2012-01-01
Full Text Available A four-node composite facet-shell element is developed, accounting for electromechanical coupling of Macrofiber Composite (MFC and conventional PZT patches. Further a warping correction is included in order to capture correctly the induced strain of conformable MFC, surface bonded on a cylindrical shell. The element performance to model the relations between in-plane electric field to normal strains is examined with the help of experiment and ANSYS analysis. In ANSYS, a simple modeling scheme is proposed for MFC using a parallel capacitors concept. The independent modal space control technique has been revisited to address the control of combination resonances through a selective modal space control scheme, where two or more modes can be combined to form the vibrating system or plant in modal domain. The developed control schemes are implemented in a digital processor using DS1104 and the closed-loop vibration control experiments are conducted on a CFRP shell structure. The influence of directionally induced actuation of MFC actuators on elastic couplings of composite shell is studied theoretically and is subsequently demonstrated in experiments. MFC actuators provide the much needed optimization domain for achieving the vibration control of combination resonances of elastically coupled deep-shell structure.
Effect of vertical seismic load on shear-bending buckling strength of thin cylindrical shells
International Nuclear Information System (INIS)
The main vessels of Fast Breeder Reactors (FBR) are cylindrical structures containing liquid, and have to be thin-walled in order to withstand severe thermal condition. One of the most critical factors in the design of earthquake-resistant FBRs is the buckling strength of the cylinder part of the reactor vessel. In order to investigate various non-linear response characteristics, including buckling, of thin cylindrical shells under vertical and horizontal seismic motion, pseudo-dynamic experiments and non-linear response simulation analysis is performed. It is confirmed that buckling is caused mainly by horizontal seismic loads, and that vertical seismic loads reduce the lateral load-carrying capacity of cylinders and amplify response displacement for a given horizontal seismic load. To evaluate the amplification of non-linear horizontal responses due to vertical input motions, the authors define a response amplification factor, which is calculated from floor response spectra of seismic waves
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
Current patch test for Mindlin plate element only satisfies the zero shear deformation condition.The patch test of non-zero constant shear for Mindlin plate problem cannot be performed.For shell element, the patch test does not even exist.Based on the theory of enhanced patch test proposed by Chen W J (2006),the authors proposed the enhanced patch test function for Mindlin plate and thin cylindrical shell elements.This enhanced patch test function can be used to assess the convergence of the Mindlin plate and cylindrical thin shell elements.
Effect of a cylindrical thin-shell of matter on the electrostatic self-force on a charge
Rubín de Celis, Emilio
2015-01-01
The electrostatic self-force on a point charge in cylindrical thin-shell space-times is interpreted as the sum of a $bulk$ field and a $shell$ field. The $bulk$ part corresponds to a field sourced by the test charge placed in a space-time without the shell. The $shell$ field accounts for the discontinuity of the extrinsic curvature ${\\kappa^p}_q$. An equivalent electric problem is stated, in which the effect of the shell of matter on the field is reconstructed with the electric potential prod...
Energy Technology Data Exchange (ETDEWEB)
Arshad, Shahid Hussain; Sultana, Nazra; Iqbal, Zafar [University of Sargodha, Department of Mathematics, Sargodha (Pakistan); Naeem, Muhammad Nawaz [G. C. University Faisalabad, Department of Mathematics, Faisalabad (Pakistan); Shah, Abdul Ghafar [Islamia University of Bahawalpur, Department of Mathematics, Bahawalpur (Pakistan)
2011-08-15
In the present work, vibration characteristics of thin functionally graded cylindrical shells are studied under the influence of various boundary conditions. Fabrication of FGM cylindrical shell is carried out by using exponential volume fraction law. Strain- and curvature-displacements relationships are taken from Love's thin shell theory. The frequency equation in the form of eigenvalue problem is obtained by adapting the Rayleigh-Ritz method. Characteristic beam functions are assumed to approximate the axial modal dependence. Effects of exponential volume fraction law on the natural frequencies of the FGM cylindrical shells for various boundary conditions are studied against circumferential wave number, length to radius ratio and thickness to radius ratio for different values of power law exponents. Results evaluated show good agreement with those available in the literature. (orig.)
A viscoplastic model of expanding cylindrical shells subjected to internal explosive detonations
Energy Technology Data Exchange (ETDEWEB)
Martineau, R.L.
1998-04-01
Magnetic flux compression generators rely on the expansion of thin ductile shells to generate magnetic fields. These thin shells are filled with high explosives, which when detonated, cause the shell to expand to over 200% strain at strain-rates on the order of 10{sup 4} s{sup {minus}1}. Experimental data indicate the development and growth of multiple plastic instabilities which appear in a quasi-periodic pattern on the surfaces of the shells. These quasi-periodic instabilities are connected by localized zones of intense shear that are oriented approximately 45{degree} from the outward radial direction. The quasi-periodic instabilities continue to develop and eventually become through-cracks, causing the shell to fragment. A viscoplastic constitutive model is formulated to model the high strain-rate expansion and provide insight into the development of plastic instabilities. The formulation of the viscoplastic constitutive model includes the effects of shock heating and damage in the form of microvoid nucleation, growth, and coalescence in the expanding shell. This model uses the Johnson-Cook strength model with the Mie-Grueneisen equation of state and a modified Gurson yield surface. The constitutive model includes the modifications proposed by Tvergaard and the plastic strain controlled nucleation introduced by Neeleman. The constitutive model is implemented as a user material subroutine into ABAQUS/Explicit, which is a commercially available nonlinear explicit dynamic finite element program. A cylindrical shell is modeled using both axisymmetric and plane strain elements. Two experiments were conducted involving plane wave detonated, explosively filled, copper cylinders. Instability, displacement, and velocity data were recorded using a fast framing camera and a Fabry-Perot interferometer. Good agreement is shown between the numerical results and experimental data. An additional explosively bulged cylinder experiment was also performed and a photomicrograph of
Steady-state temperature distribution in living tissue modeled as cylindrical shells.
Shitzer, A.; Chato, J. C.
1971-01-01
Closed form, analytical solutions to the problem of steady-state heat transfer in living tissue modeled as cylindrical shells are presented and discussed. These solutions are particularly useful for the study of temperature distributions in the extremities. Metabolic heat generation, conduction, and heat transported by the blood perfusing the tissue are considered in the model. The results demonstrate the important role that the blood stream plays in the transfer of heat inside living tissue. Solutions are also presented for the limiting cases of diminishing blood flow that would occur during vasoconstriction or occlusion of blood by external means.
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
An FAE (Fuel-Air-Explosives) device is used to develop a numerical and theoretical analysis of a thin cylindrical shell with inner explosive loading. The dynamic fracture process is simulated numerically in the DYNA3D program using the finite element method. The material's dynamic properties are described by a strain hardening viscoplastic constitution. A damage variable is introduced in the determination of the dynamic fracture criterion. Final rupture of structure is decided by a rupture-strain criterion which is deduced in terms of a critical damage variable. The numerical results have been compared with theoretical solutions.
Institute of Scientific and Technical Information of China (English)
SHENG Hong-yu; LI He-ping; XU Hai-yan
2009-01-01
Based on the theories of three-dimensional elasticity and piezoelectricity, and by assuming appropriate boundary functions, we established a state equation of piezoelectric cylindrical shells. By using the transfer matrix method, we presented an analytical solution that satisfies all the arbitrary boundary conditions at boundary edges, as well as on upper and bottom surfaces. Our solution takes into account all the independent elastic and piezoelectric constants for a piezoelectric orthotropy, and satisfies continuity conditions between plies of the laminates. The principle of the present method and corresponding results can be widely used in many engineering fields and be applied to assess the effectiveness of varions approximate and numerical models.
Ray and wave scattering in smoothly curved thin shell cylindrical ridges
Sondergaard, Niels
2016-01-01
We propose wave and ray approaches for modelling mid- and high- frequency structural vibrations through smoothed joints on thin shell cylindrical ridges. The models both emerge from a simplified classical shell theory setting. The ray model is analysed via an appropriate phase-plane analysis, from which the fixed points can be interpreted in terms of the reflection and transmission properties. The corresponding full wave scattering model is studied using the finite difference method to investigate the scattering properties of an incident plane wave. Through both models we uncover the scattering properties of smoothed joints in the interesting mid-frequency region close to the ring frequency, where there is a qualitative change in the dynamics from anisotropic to simple geodesic propagation.
Directory of Open Access Journals (Sweden)
Surya Narain
2004-10-01
Full Text Available This study investigates magnetoelastic torsional vibration of a non-homogeneous aeolotropic cylindrical shell of viscoelastic solids. The non-homogeneity of the shell obeyingpower law variation of elastic constants and density given by Aij= Crjf', p = por"(i, j = 1,2 ,... 6, where Cu (i, j = 1,2, ... 6 and po are constants and r is the radius vector. Frequency equation and phase velocity in several cases have been derived. Such problems of interaction of elastic and electromagnetic fields have numerous applications in various branches of science, particularly in the detection of mechanical explosions in the interior of the earth and in the electromagnetic energy into vacuum.
Effect of a cylindrical thin-shell of matter on the electrostatic self-force on a charge
International Nuclear Information System (INIS)
The electrostatic self-force on a point charge in cylindrical thin-shell space-times is interpreted as the sum of a bulk field and a shell field. The bulk part corresponds to a field sourced by the test charge placed in a space-time without the shell. The shell field accounts for the discontinuity of the extrinsic curvature κpq. An equivalent electric problem is stated, in which the effect of the shell of matter on the field is reconstructed with the electric potential produced by a non-gravitating charge distribution of total image charge Q, to interpret the shell field in both the interior and exterior regions of the space-time. The self-force on a point charge q in a locally flat geometry with a cylindrical thin-shell of matter is calculated. The charge is repelled from the shell if κpq = κ < 0 (ordinarymatter) and attracted toward the shell if κ > 0 (exotic matter). The total image charge is zero for exterior problems, while for interior problems Q/q = κre, with re the external radius of the shell. The procedure is general and can be applied to interpret self-forces in other space-times with shells, e.g., for locally flat wormholes we found Q-+wh/q = -1/(κwhr±). (orig.)
Effect of a cylindrical thin-shell of matter on the electrostatic self-force on a charge
Rubín de Celis, Emilio
2016-02-01
The electrostatic self-force on a point charge in cylindrical thin-shell space-times is interpreted as the sum of a bulk field and a shell field. The bulk part corresponds to a field sourced by the test charge placed in a space-time without the shell. The shell field accounts for the discontinuity of the extrinsic curvature {κ ^p}_q. An equivalent electric problem is stated, in which the effect of the shell of matter on the field is reconstructed with the electric potential produced by a non-gravitating charge distribution of total image charge Q, to interpret the shell field in both the interior and exterior regions of the space-time. The self-force on a point charge q in a locally flat geometry with a cylindrical thin-shell of matter is calculated. The charge is repelled from the shell if {κ p}p=κ attracted toward the shell if κ >0 (exotic matter). The total image charge is zero for exterior problems, while for interior problems Q/q=-κ r_e, with r_e the external radius of the shell. The procedure is general and can be applied to interpret self-forces in other space-times with shells, e.g., for locally flat wormholes we found Q_{∓}^{wh}/q=-1/ (κ_{wh} r_{± }).
Effect of a cylindrical thin-shell of matter on the electrostatic self-force on a charge
Energy Technology Data Exchange (ETDEWEB)
Rubin de Celis, Emilio [Universidad de Buenos Aires y IFIBA, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina)
2016-02-15
The electrostatic self-force on a point charge in cylindrical thin-shell space-times is interpreted as the sum of a bulk field and a shell field. The bulk part corresponds to a field sourced by the test charge placed in a space-time without the shell. The shell field accounts for the discontinuity of the extrinsic curvature κ{sup p}{sub q}. An equivalent electric problem is stated, in which the effect of the shell of matter on the field is reconstructed with the electric potential produced by a non-gravitating charge distribution of total image charge Q, to interpret the shell field in both the interior and exterior regions of the space-time. The self-force on a point charge q in a locally flat geometry with a cylindrical thin-shell of matter is calculated. The charge is repelled from the shell if κ{sup p}{sub q} = κ < 0 (ordinarymatter) and attracted toward the shell if κ > 0 (exotic matter). The total image charge is zero for exterior problems, while for interior problems Q/q = κr{sub e}, with re the external radius of the shell. The procedure is general and can be applied to interpret self-forces in other space-times with shells, e.g., for locally flat wormholes we found Q{sub -+}{sup wh}/q = -1/(κ{sub wh}r{sub ±}). (orig.)
Radial oscillations of highly stressed nonhomogenous, thick-walled cylindrical and spherical shells
International Nuclear Information System (INIS)
The present work investigates the infinitesimal breathing motions of spherical and long cylindrical shells of arbitrary wall thickness subject to a finite, axisymmetric deformation field caused by uniform internal and/or external pressures. A neo-Hookean material with a material constant varying continuously along the radial direction is used. The shell is first subject to finite, axisymmetric, static deformations and is then exposed to a secondary, axisymmetric, static deformations and is then exposed to a secondary, axisymmetric, dynamic displacement field. Based on the theory of small deformations superposed on large deformations, closed form expressions are obtained for the frequency of small oscillations about the highly prestressed state. Frequency versus initial deformation parameter curves are given for several nonhomogeneity functions and for various wall thicknesses. The softening or the hardening behaviors of the shells for varying prestress values are observed from these curves. When the frequency of breathing motions cease to be real valued, the superposed secondary motions are no larger periodic. Thus, the critical value of the prestress causing instability is defined as the one which corresponds to zero frequency. It is seen that when the nonhomogeneity parameters are taken zero, the known results of the homogeneous case are obtained. Although the material is assumed to be incompressible, the theory is general enough to include compressible materials. However, in this case, the governing equations of the problem become more complicated for a closed form solution. An interesting and practical extension of the problem is the vibration analysis of layered shells
Steel, Robin; Fish, Peter J
2002-02-01
Flow phantoms used in medical ultrasound usually employ a plastic tube as a blood vessel mimic. These tubes often have acoustic properties differing significantly from the tissue and blood-mimicking media, which results in distortion of the acoustic pressure field within the tubes and, hence, of the Doppler flow spectra. Previous analyses of this problem have used some form of the infinite plate transmission coefficient, although at least one ray-based analysis has considered a cylindrical interface but with zero wall thickness. In this paper, we compare these approximate pressure fields with the exact solution for oblique incidence on a viscoelastic cylindrical shell at 5 MHz to find for which materials the plate approximation is valid. The shell has water both inside and outside, but it can be modified to use a different fluid inside and also to include absorption in either fluid. We find the plate approximation is reasonable for soft tubes such as the copolymer Cflex (Cole-Palmer, Niles, IL) but much less so for hard tubes such as polymethylmethacrylate (PMMA). PMID:11885684
Acoustic resonance scattering from a multilayered cylindrical shell with imperfect bonding.
Rajabi, M; Hasheminejad, Seyyed M
2009-12-01
The method of wave function expansion is adopted to study the three dimensional scattering of a time-harmonic plane progressive sound field obliquely incident upon a multi-layered hollow cylinder with interlaminar bonding imperfection. For the generality of solution, each layer is assumed to be cylindrically orthotropic. An approximate laminate model in the context of the modal state equations with variable coefficients along with the classical T-matrix solution technique is set up for each layer to solve for the unknown modal scattering and transmission coefficients. A linear spring model is used to describe the interlaminar adhesive bonding whose effects are incorporated into the global transfer matrix by introduction of proper interfacial transfer matrices. Following the classic acoustic resonance scattering theory (RST), the scattered field and response to surface waves are determined by constructing the partial waves and obtaining the non-resonance (backgrounds) and resonance components. The solution is first used to investigate the effect of interlayer imperfection of an air-filled and water submerged bilaminate aluminium cylindrical shell on the resonances associated with various modes of wave propagation (i.e., symmetric/asymmetric Lamb waves, fluid-borne A-type waves, Rayleigh and Whispering Gallery waves) appearing in the backscattered spectrum, according to their polarization and state of stress. An illustrative numerical example is also given for a multi-layered (five-layered) cylindrical shell for which the stiffness of the adhesive interlayers is artificially varied. The sensitivity of resonance frequencies associated with higher mode numbers to the stiffness coefficients is demonstrated to be a good measure of the bonding strength. Limiting cases are considered and fair agreements with solutions available in the literature are established. PMID:19586650
Self-force on a charge in a locally flat geometry with a cylindrical thin-shell
de Celis, Emilio Rubín
2015-01-01
The electrostatic self-interaction of a point charge is calculated for an arbitrary position in a locally flat space-time with a cylindrical thin-shell of matter centred at a straight cosmic string. The results show a radial self-force. Near the string or asymptotically far from the thin-shell the charge is repelled from the central axis, this interaction is produced by the global deficit angle of the geometry. In the neighbourhood of the shell the charge is repelled from it if the surface energy density is positive (ordinary matter) and attracted towards the shell if the surface energy density is negative (exotic matter).
Plattenburg, Joseph; Dreyer, Jason T.; Singh, Rajendra
2016-06-01
This paper proposes a new analytical model for a thin cylindrical shell that utilizes a homogeneous cardboard liner to increase modal damping. Such cardboard liners are frequently used as noise and vibration control devices for cylindrical shell-like structures in automotive drive shafts. However, most prior studies on such lined structures have only investigated the associated damping mechanisms in an empirical manner. Only finite element models and experimental methods have been previously used for characterization, whereas no analytical studies have addressed sliding friction interaction at the shell-liner interface. The proposed theory, as an extension of a prior experimental study, uses the Rayleigh-Ritz method and incorporates material structural damping along with frequency-dependent viscous and Coulomb interfacial damping formulations for the shell-liner interaction. Experimental validation of the proposed model, using a thin cylindrical shell with three different cardboard liner thicknesses, is provided to validate the new model, and to characterize the damping parameters. Finally, the model is used to investigate the effect of the liner and the damping parameters on the modal attenuation of the shell vibration, in particular for the higher-order coupled shell modes.
Kriegesmann, Benedikt; Hilburger, Mark W.; Rolfes, Raimund
2012-01-01
Results from a numerical study of the buckling response of a thin-walled compressionloaded isotropic circular cylindrical shell with initial geometric and loading imperfections are used to determine a lower bound buckling load estimate suitable for preliminary design. The lower bound prediction techniques presented herein include an imperfection caused by a lateral perturbation load, an imperfection in the shape of a single stress-free dimple (similar to the lateral pertubation imperfection), and a distributed load imperfection that induces a nonuniform load in the shell. The ABAQUS finite element code is used for the analyses. Responses of the cylinders for selected imperfection amplitudes and imperfection types are considered, and the effect of each imperfection is compared to the response of a geometrically perfect cylinder. The results indicate that compression-loaded shells subjected to a lateral perturbation load or a single dimple imperfection, and a nonuniform load imperfection, exhibit similar buckling behavior and lower bound trends and the predicted lower bounds are much less conservative than the corresponding design recommendation NASA SP-8007 for the design of buckling-critical shells. In addition, the lateral perturbation technique and the distributed load imperfection produce response characteristics that are physically meaningful and can be validated via laboratory testing.
Model-based failure detection for cylindrical shells from noisy vibration measurements.
Candy, J V; Fisher, K A; Guidry, B L; Chambers, D H
2014-12-01
Model-based processing is a theoretically sound methodology to address difficult objectives in complex physical problems involving multi-channel sensor measurement systems. It involves the incorporation of analytical models of both physical phenomenology (complex vibrating structures, noisy operating environment, etc.) and the measurement processes (sensor networks and including noise) into the processor to extract the desired information. In this paper, a model-based methodology is developed to accomplish the task of online failure monitoring of a vibrating cylindrical shell externally excited by controlled excitations. A model-based processor is formulated to monitor system performance and detect potential failure conditions. The objective of this paper is to develop a real-time, model-based monitoring scheme for online diagnostics in a representative structural vibrational system based on controlled experimental data. PMID:25480059
Deng, D S; Johnson, S G; Fink, Y
2010-01-01
Recent experimental observations have demonstrated interesting instability phenomenon during thermal drawing of microstructured glass/polymer fibers, and these observations motivate us to examine surface-tension-driven instabilities in concentric cylindrical shells of viscous fluids. In this paper, we focus on a single instability mechanism: classical capillary instabilities in the form of radial fluctuations, solving the full Navier--Stokes equations numerically. In equal-viscosity cases where an analytical linear theory is available, we compare to the full numerical solution and delineate the regime in which the linear theory is valid. We also consider unequal-viscosity situations (similar to experiments) in which there is no published linear theory, and explain the numerical results with a simple asymptotic analysis. These results are then applied to experimental thermal drawing systems. We show that the observed instabilities are consistent with radial-fluctuation analysis, but cannot be predicted by radi...
Fast Prediction of Acoustic Radiation from a Hemi-capped Cylindrical Shell in Waveguide
Institute of Scientific and Technical Information of China (English)
Hongyang Chen; Qi Li; Dejiang Shang
2014-01-01
In order to predict acoustic radiation from a structure in waveguide, a method based on wave superposition is proposed, in which the free-space Green’s function is used to match the strength of equivalent sources. In addition, in order to neglect the effect of sound reflection from boundaries, necessary treatment is conducted, which makes the method more efficient. Moreover, this method is combined with the sound propagation algorithms to predict the sound radiated from a cylindrical shell in waveguide. Numerical simulations show the effect of how reflections can be neglected if the distance between the structure and the boundary exceeds the maximum linear dimension of the structure. It also shows that the reflection from the bottom of the waveguide can be approximated by plane wave conditionally. The proposed method is more robust and efficient in computation, which can be used to predict the acoustic radiation in waveguide.
Design Optimization and Residual Strength Assessment of a Cylindrical Composite Shell Structure
Rais-Rohani, Masoud
2000-01-01
A summary of research conducted during the specified period is presented. The research objectives included the investigation of an efficient technique for the design optimization and residual strength assessment of a semi-monocoque cylindrical shell structure made of composite materials. The response surface methodology is used in modeling the buckling response of individual skin panels under the combined axial compression and shear loading. These models are inserted into the MSC/NASTRAN code for design optimization of the cylindrical structure under a combined bending-torsion loading condition. The comparison between the monolithic and sandwich skin design cases indicated a 35% weight saving in using sandwich skin panels. In addition, the residual strength of the optimum design was obtained by identifying the most critical region of the structure and introducing a damage in the form of skin-stringer and skin-stringer-frame detachment. The comparison between the two skin design concepts indicated that the sandwich skin design is capable of retaining a higher residual strength than its monolithic counterpart. The results of this investigation are presented and discussed in this report.
Mallon, N.; Fey, R.H.B.; Nijmeijer, H.
2010-01-01
Considering both an experimental and a numerical approach, the dynamic stability of a harmonically base-excited thin orthotropic cylindrical shell carrying a top mass is examined. To be able to compare the experimentally obtained results with numerical results, a semi-analytical coupled shaker-struc
Indian Academy of Sciences (India)
K Athiannan; R Palaninathan
2004-02-01
This paper presents experimental studies on buckling of cylindrical shell models under axial and transverse shear loads. Tests are carried out using an experimental facility specially designed, fabricated and installed, with provision for in-situ measurement of the initial geometric imperfections. The shell models are made by rolling and seam welding process and hence are expected to have imperfections more or less of a kind similar to that of real shell structures. The present work thus differs from most of the earlier investigations. The measured maximum imperfections $\\delta_{\\text{max}}$ are of the order of $\\pm 3t$ (t = thickness). The buckling loads obtained experimentally are compared with the numerical buckling values obtained through ﬁnite element method (FEM). In the case of axial buckling, the imperfect geometry is obtained in four ways and in the case of transverse shear buckling, the FE modelling of imperfect geometry is done in two ways. The initial geometric imperfections affect the load carrying capacity. The load reduction is considerable in the case of axial compression and is marginal in the case of transverse shear buckling. Comparisons between experimental buckling loads under axial compression, reveal that the extent of imperfection, rather than its maximum value, in a specimen inﬂuences the failure load. Buckling tests under transverse shear are conducted with and without axial constraints. While differences in experimental loads are seen to exist between the two conditions, the numerical values are almost equal. The buckling modes are different, and the experimentally observed and numerically predicted values are in complete disagreement.
Honeycutt, T. E.; Roberts, T. G.
1986-05-01
Brass retainer rings are currently fastened to artillery shells by spinning each shell at a high rate and then jamming the ring on it so that it is fastened or welded by friction between the two objects. This is an energy-inefficient process which heats and weakens more material than is desirable. The shell spinning at a high rate is also potentially dangerous. A laser welder is provided that generates output energy focused on a circular or cylindrical shape for simultaneously welding around a 360 degs circumference without unnecessarily heating large amounts of material. The welder may be used to fasten cylindrical shaped objects, gears and shafts together, which is difficult to do by conventional means. The welder may also be used to fasten one cylinder to another. To accomplish the welding, a laser has an unstable optical cavity arranged with its feedback mirror centered to generate a circular output beam having an obscuration in the center. A circularly-symmetric, off-axis concave mirror focuses the output beam onto the objects being fastened and away from the center line or axis of the circular beam.
Vertical position control for non-circular plasma column by shell effect
International Nuclear Information System (INIS)
The next tokamak fusion reactor, for example, INTOR, obtains a high beta under a non-circular plasma whose MHD equilibrium requires an external field configuration with negative decay index. It is well known that such a plasma in its external field has a positional instability in the vertical direction. How to control the instability is in general composed of two kinds of method. One is to use a passive position control, that is, the shell effect which will be effective up to the growth time of instability (= a few ten msec.) above that time constant. In this report some concrete shell-structures under which the shell effect will play its part in the next tokamak are proposed on taking account of practical forms of the first wall and the vacuum chamber in the device. Analyses of the shell effect contain a dipole current model, in which coupling of shell currents with a plasma column is replaced with that of the current with dipole currents, and an eddy current evaluation. (author)
Institute of Scientific and Technical Information of China (English)
Jian Yong-Jun; E Xue-Quan; Zhang Jie; Meng Jun-Min
2004-01-01
Singular perturbation theory of two-time-scale expansions was developed in inviscid fluids to investigate patternforming, structure of the single surface standing wave, and its evolution with time in a circular cylindrical vessel subject to a vertical oscillation. A nonlinear slowly varying complex amplitude equation, which involves a cubic nonlinear term,an external excitation and the influence of surface tension, was derived from the potential flow equation. Surface tension was introduced by the boundary condition of the free surface in an ideal and incompressible fluid. The results show that when forced frequency is low, the effect of surface tension on the mode selection of surface waves is not important.However, when the forced frequency is high, the surface tension cannot be neglected. This manifests that the function of surface tension is to cause the free surface to return to its equilibrium configuration. In addition, the effect of surface tension seems to make the theoretical results much closer to experimental results.
International Nuclear Information System (INIS)
An analytical method was proposed for calculating radiative fluxes incident on a planar circular detector from a volume multiple point chemi- or bio-luminescent source inside a coaxial cylindrical reactor. The method was designed for a cylindrical reactor when the surface reflections were neglected and when chemi- or bio-luminescence reaches a detector embedded in the same homogeneous optical medium as the point emitters of the volume multiple point source model. The radiative fluxes from arbitrarily distributed point emitters were expressed by one generalized quadruple-integral formula. Then some double- and single-integral formulas were obtained for calculating radiative fluxes from identically radiating point emitters uniformly distributed within the reactor. Selected results were computed and illustrated graphically. The obtained formulas are suitable for optimizing and/or calibrating the considered source-detectors systems (optical radiometers or luminometers) and determining radiative fluxes generated by chemical, biological, and physical processes leading to chemi-, bio-, radio-, and sono-luminescence for example.
Mindle, W. L.; Torvik, P. J.
1986-01-01
The natural frequencies and associated mode shapes for three thick open cantilevered cylindrical shells were determined both numerically and experimentally. The shells ranged in size from moderately to very thick with length to thickness ratios of 16, 8 and 5.6, the independent dimension being the shell thickness. The shell geometry is characterized by a circumferential angle of the 142 degrees and a ratio of length to inner radii arc length near 1.0. The finite element analysis was performed using NASTRAN's (COSMIC) triangular plate bending element CTRIA2, which includes membrane effects. The experimental results were obtained through holographic interferometry which enables one to determine the resonant frequencies as well as mode shapes from photographs of time-averaged holograms.
Bakulin, V. N.; Volkov, E. N.; Nedbai, A. Ya.
2016-05-01
The dynamic stability of a cylindrical orthotropic shell reinforced by longitudinal ribs and a hollow cylinder under the action of axial forces changing harmonically with time was investigated with regard for the axial contact interaction of the shell with the ribs. A solution of the differential equations defining this process has been obtained in the form of trigonometric series in the angular and time coordinates. A two-term approximation of the Mathieu-Hill equations of motion was used for construction of the main region of instability of the shell. As a result, the problem was reduced to a system of algebraic equations for components of displacements of the shell at the locations of the ribs. The problem for uniformly spaced ribs was solved in the explicit form. A numerical example of this solution is presented.
Chaotic Energy Exchange Through Auto-Parametric Resonance in Cylindrical Shells
POPOV, A. A.; THOMPSON, J. M. T.; MCROBIE, F. A.
2001-11-01
Internal auto-parametric instabilities in the free non-linear vibrations of a cylindrical shell are studied numerically, focusing on two modes (a concertina mode and a chequerboard mode) whose non-linear interaction breaks the in-out symmetry of the linear vibration theory. The two-mode interaction leads to preferred vibration patterns with larger deflection inwards than outwards, and at internal resonance, significant energy transfer occurs between the modes. This has regular and chaotic features. Here, direct numerical integration is employed to examine chaotic motions. Using a set of 2-D Poincaré sections, each valid for a fixed level of the Hamiltonian, H, the instability under increasing H appears, as a supercritical period-doubling pitchfork bifurcation. Chaotic motions near a homoclinic separatrix appear immediately after the bifurcation, giving an irregular exchange of energy. This chaos occurs at arbitrarily low amplitude as perfect tuning is approached. The instability manifests itself as repeating excursions around the separatrix, and a number of practical predictions can be made. These include the magnitude of the excursion, the time taken to reach this magnitude and the degree of chaos and unpredictability in the outcome. The effect of small damping is to pull the motion away from what was the chaotic separatrix, giving a response that resembles, for a while, the lower-energy quasi-periodic orbits of the underlying Hamiltonian system.
International Nuclear Information System (INIS)
The load carrying behaviour of cylindrical thin-walled shell structures under pressure load is strongly dependent on the nature and magnitude of the imperfections invariably caused by various manufacturing processes. The present paper examines instabilities of long homogeneous and isotropic thin elastic tubes, characterized by geometric imperfections like eccentricity or oval shape, on the buckling behaviour in conditions for which, at present, a complete theoretical analysis was not found in literature. Moreover, the additional aspect of the influence of the welded joint geometry and position is investigated over a wide range of diameter to thickness ratio, extending the findings of previous works. The experiments were conducted on test specimens with different materials, e.g. A-316 ASTM (with and without seam weld) and Inconel, as well as different loading conditions (lateral and hydrostatic external pressure). A validation of numerical evaluations by comparison with test results is also performed. A good agreement has been observed between the experimental data and the elasto-plastic finite element analyses results, highlighting also the different influence of the mentioned imperfections on the buckling loads. For all 3 tube families tested, the oval form was found to reduce the collapse pressure quite significantly. The local thickness variation along the longitudinal welding and the interaction between neighbouring imperfections have been shown to be important factors governing buckling
The effective conductivity of three-phase composite materials with circular cylindrical inclusions
International Nuclear Information System (INIS)
We extend the Rayleigh method for the calculation of the effective conductivity to three-phase composite materials. The materials under study consist of two types of circular cylinders in a periodic arrangement embedded in a matrix. Highly accurate values for lattice sums were obtained using algorithms which have been recently developed. A series of explicit formulations, which are used to facilitate the calculation of the effective conductivity of the composites under study, are reported. We also perform a series of numerical calculations to study the behaviour of these composites
Energy Technology Data Exchange (ETDEWEB)
Alashti, R. Akbari, E-mail: raalashti@nit.ac.ir [Mechanical Engineering Department, Babol University of Technology, P.O. Box 484, Shariati Avenue, Babol (Iran, Islamic Republic of); Khorsand, M. [Mechanical Engineering Department, Babol University of Technology, P.O. Box 484, Shariati Avenue, Babol (Iran, Islamic Republic of)
2011-05-15
Three-dimensional thermo-elastic analysis of a functionally graded cylindrical shell with piezoelectric layers under the effect of asymmetric thermo-electro-mechanical loads is carried out. Numerical results of displacement, stress and thermal fields are obtained using two versions of the differential quadrature methods, namely polynomial and Fourier quadrature methods. Material properties of the shell are assumed to be graded in the radial direction according to a power law but the Poisson's ratio is assumed to be constant. Shells are considered to be under the effect of the pressure loading in the form of cosine and ring pressure loads, electric potentials and temperature fields. Numerical results for various boundary conditions are obtained and the effects of the thickness of piezoelectric layers, grading index of material properties and the ratio of the thickness to the radius of the shell on these results is presented. - Highlights: > A numerical study of an FGM cylindrical shell with piezoelectric layers is made. > Governing equations are solved by two versions of differential quadrature methods. > The effect of layers thickness, grading index and geometrical ratios is presented.
Directory of Open Access Journals (Sweden)
Frederico Martins Alves da Silva
2015-01-01
Full Text Available This work investigates the influence of Young’s modulus, shells thickness, and geometrical imperfection uncertainties on the parametric instability loads of simply supported axially excited cylindrical shells. The Donnell nonlinear shallow shell theory is used for the displacement field of the cylindrical shell and the parameters under investigation are considered as uncertain parameters with a known probability density function in the equilibrium equation. The uncertainties are discretized as Hermite-Chaos polynomials together with the Galerkin stochastic procedure that discretizes the stochastic equation in a set of deterministic equations of motion. Then, a general expression for the transversal displacement is obtained by a perturbation procedure which identifies all nonlinear modes that couple with the linear modes. So, a particular solution is selected which ensures the convergence of the response up to very large deflections. Applying the standard Galerkin method, a discrete system in time domain that considers the uncertainties is obtained and solved by fourth-order Runge-Kutta method. Several numerical strategies are used to study the nonlinear behavior of the shell considering the uncertainties in the parameters. Special attention is given to the influence of the uncertainties on the parametric instability and time response, showing that the Hermite-Chaos polynomial is a good numerical tool.
Bezerra, V B; Klimchitskaya, G L; Mostepanenko, V M; Saharian, A A
2011-01-01
We derive the exact Casimir-Polder potential for a polarizable microparticle inside an ideal metal cylindrical shell using the Green function method. The exact Casimir-Polder potential for a particle outside a shell, obtained recently by using the Hamiltonian approach, is rederived and confirmed. The exact quantum field theoretical result is compared with that obtained using the proximity force approximation and a very good agreement is demonstrated at separations below 0.1$R$, where $R$ is the radius of the cylinder. The developed methods are applicable in the theory of topological defects.
Energy Technology Data Exchange (ETDEWEB)
Bezerra, V.B.; Bezerra de Mello, E.R. [Federal University of Paraiba, Department of Physics, C.P. 5008, Joao Pessoa, Pb (Brazil); Klimchitskaya, G.L. [Federal University of Paraiba, Department of Physics, C.P. 5008, Joao Pessoa, Pb (Brazil); North-West Technical University, St. Petersburg (Russian Federation); Mostepanenko, V.M. [Federal University of Paraiba, Department of Physics, C.P. 5008, Joao Pessoa, Pb (Brazil); Noncommercial Partnership ' ' Scientific Instruments' ' , Moscow (Russian Federation); Saharian, A.A. [Yerevan State University, Department of Physics, Yerevan (Armenia)
2011-04-15
We derive the exact Casimir-Polder potential for a polarizable microparticle inside an ideal metal cylindrical shell using the Green function method. The exact Casimir-Polder potential for a particle outside a shell, obtained recently by using the Hamiltonian approach, is rederived and confirmed. The exact quantum field theoretical result is compared with that obtained using the proximity force approximation and a very good agreement is demonstrated at separations below 0.1R, where R is the radius of the cylinder. The developed methods are applicable in the theory of topological defects. (orig.)
Directory of Open Access Journals (Sweden)
Mohammad Zamani Nejad
2014-01-01
Full Text Available Using disk form multilayers, a semi-analytical solution has been derived for determination of displacements and stresses in a rotating cylindrical shell with variable thickness under uniform pressure. The thick cylinder is divided into disk form layers form with their thickness corresponding to the thickness of the cylinder. Due to the existence of shear stress in the thick cylindrical shell with variable thickness, the equations governing disk layers are obtained based on first-order shear deformation theory (FSDT. These equations are in the form of a set of general differential equations. Given that the cylinder is divided into n disks, n sets of differential equations are obtained. The solution of this set of equations, applying the boundary conditions and continuity conditions between the layers, yields displacements and stresses. A numerical solution using finite element method (FEM is also presented and good agreement was found.
Institute of Scientific and Technical Information of China (English)
Yang Xiaomeng; Hu Yuantai; Yang Jiashi
2005-01-01
We study electromechanical fields in the anti-plane deformation of an infinite medium of piezoelectric materials of 6 mm symmetry with a circular cylindrical hole. The theory of electroelastic dielectrics with electric field gradient in the constitutive relations is used. Special attention is paid to the fields near the surface of the hole.
Matrix solution of coupling impedance in multi-layer circular cylindrical structures
International Nuclear Information System (INIS)
Continuing interest in computing the coupling impedance of cylindrical multi-layer beam tubes led to several recent publications. A novel matrix method is here presented in which radial wave propagation is treated in analogy to longitudinal transmission lines. Starting from the Maxwell equations the solutions for monopole electromagnetic fields are in each layer described by a 2 x 2 matrix. Assuming isotropic material properties within one layer, the radially transverse field components at the inner boundary of a layer are uniquely determined by matrix transfer of the field components at its outer boundary. By imposing power flow constraints on the matrix, field matching between layers is enforced and replaced by matrix multiplication. The coupling impedance of a stainless steel beam tube defined by a matrix is given as a representative demonstration
Institute of Scientific and Technical Information of China (English)
LIU Hongmin; CHEN Suwen; PENG Yan; SUN Jianliang
2015-01-01
As the traditional forging process has many problems such as low efficiency, high consumption of material and energy, large cylindrical shell rolling is introduced. Large cylindrical shell rolling is a typical rotary forming technology, and the upper and lower rolls have different radii and speeds. To quickly predict the three-dimensional stresses and eliminate fishtall defect, an improved strip layer method is developed, in which the asymmetry of the upper and lower rolls, non-uniform deformation and stress, as well as the asymmetrical spread on the end surface are considered. The deformation zone is divided into a certaln number of layers and strips along the thickness and width, respectively. The transverse displacement model is constructed by polynomial function, in order to increase the computation speed greatly. From the metal plastic mechanics principle, the three-dimensional stress models are established. The genetic algorithm is used for optimization calculation in an industrial experiment example. The results show that the rolling pressure, the normal stresses, the upper and lower friction stress distributions are not similar with those of a general plate rolling. There are two relative maximum values in rolling pressure distribution. The upper and lower longitudinal friction stresses change direction nearby the upper and lower neutral points, respectively. The fishtall profile of spread on the end surface is predicted satisfactorily. The reduction could be helpful to eliminate fishtall defect. The large cylindrical shell rolling example illustrates the calculation results acquired rapidly are good agreements with the finite element simulation and experimental values of previous study. A highly effective and reliable three-dimensional simulation method is proposed for large cylindrical shell rolling and other asymmetrical rolling.
Effect of radial electric boundary potential on a circular cylindrical magneto plasma, 3
International Nuclear Information System (INIS)
In krypton gas plasma, the frequency shift was measured by applying an alternating potential to a cylindrical side wall. The experimental apparatus was similar to that for the former study. In the effect induced in plasma, there was no difference when an insulator was attached to the side wall or not, as for as the frequency shift phenomenon was concerned. The procedure of measurement was also the same as the former study. One of the strongest waves excited in this type of electron beam plasma systems can be observed near the upper hybrid frequency which is due to the interaction of the slow plasma waves in an electron beam with the cyclotron waves in the generated plasma. A negative going square wave potential was applied. The amount of frequency shift in relation to the amplitude of the applied potential is shown. When the side wall was at a static negative potential, the frequency of the spectral line did not change. When an oscillating potential was applied, the frequency decreased. The amount of frequency shift depended on the amplitude and frequency of a wall potential. When the amplitude was about 10 V, a remarkable difference arose. In the case of krypton plasma, the short circuit effect of beam current must be related. (Kako, I.)
Sun, Dongming; Wang, Sheng; Sakurai, Junpei; Choi, Kee-Bong; Shimokohbe, Akira; Hata, Seiichi
2010-04-01
A piezoelectric linear ultrasonic motor is proposed, with a cylindrical stator and slider structure. The length and diameter of the motor are about 10 and 1.5 mm, respectively. The stator consists of two piezoelectric ceramic (PZT) tubes connected by a thin film metallic glass (TFMG) pipe. The stator is designed based on theoretical analyses and finite element method (FEM) simulation. The traveling wave propagation is obtained in the FEM simulation under the proper geometrical sizes, suitable boundary conditions and driving voltage signals. The trajectories of particles on the TFMG pipe are elliptical motion. In the experiment, a 25 µm thick TFMG pipe is fabricated using the rotating magnetron sputtering technique and the vibration characteristics of the stator are measured by a laser Doppler vibrometer (LDV) system. Bidirectional motion of the slider is observed around 600 kHz, the maximum velocity is near to 40 mm s - 1 at 50 Vp-p for the loose slider and the maximum output force is 6 mN at 70 Vp-p for the tight slider.
On the Flutter of Cylindrical Shells and Panels Moving in a Flow of Gas
Stepanov, R. D.
1958-01-01
The equations of shells are taken in the form of the general technical theory of shallow shells and shells of medium length. The aerodynamic forces acting on a shell are taken into account only as forces of excess pressure according to the formula proposed by A.A. Iliushin in reference 3.
International Nuclear Information System (INIS)
The load carrying behaviour of cylindrical thin-walled shell structures under pressure load is strongly dependent on the nature and magnitude of the imperfections invariably caused by various manufacturing processes. The present paper examines instabilities of long homogeneous and isotropic thin elastic tubes, characterized by geometric imperfections like eccentricity or ovality, on the buckling behaviour in conditions for which, at present, a complete theoretical analysis was not found in literature. Moreover, the additional aspect of the influence of the welded joint geometry and position is investigated over a wide range of diameter to thickness ratio, extending the findings of previous works. The problem of buckling for variable load conditions is relevant in the context of NPP applications as, for instance the optimisation of an integrated and innovative LWR Steam Generator (SG) tubes, according to the updated ASME rules. To the purpose, at Pisa University a rather intense research activity is being carried out on the buckling of thin walled metal specimens in the dimensional range suitable for the above mentioned application. Therefore a test equipment (with the necessary data acquisition facility), suitable for carrying out test series on this issue, as well as numerical models implemented on the MARC FEM code, were set up. The experiments were conducted on test specimens with different materials, e.g. A-316 ASTM (with and without seam weld) and Inconel 690 TT, as well as different loading conditions (lateral and hydrostatic external pressure). A validation of numerical evaluations by comparison with test results is also performed. A good agreement has been observed between the experimental data and the elasto-plastic finite element analyses results, highlighting also the different influence of the mentioned imperfections on the buckling loads
International Nuclear Information System (INIS)
A hybrid finite element method is developed to predict the influence of large amplitude vibration of orthotropic, circumferentially non-uniform open and closed cylindrical shells submerged and subjected to an internal and/or external fluid flow. The open shells are assumed to be freely simply supported along their curved edges and to have arbitrary straight edge boundary conditions. The method developed is a combination of thin shell theory, fluid theory and the finite element method. The solution is divided into three parts. In part one, the displacement functions are obtained from Sanders' linear shell theory and the mass and linear stiffness matrices for an open shell element are obtained by the finite element procedure. In part two, the modal coefficients, derived from the Sanders-Koiter non-linear theory of thin shells, are obtained for these displacement functions. Expressions for the second and third order non-linear stiffness matrices of the open shell element are then determined through the finite element method. With the dynamic pressure of the moving fluid and the boundary condition of impermeability, we develop in the third part the mass and the stiffness matrices of a fluid finite element for the interaction shell-fluid system. The non-linear equation of motion is then solved by the fourth-order Runge-Kutta numerical method. The linear and non-linear natural frequency variations are determined as a function of shell amplitudes for different cases. Here the uncoupled non-linear system is solved. The complete solution of the coupled non-linear system will be treated in a future work. (orig.)
Qu, Yegao; Hua, Hongxing; Meng, Guang
2015-10-01
A semi-analytical method is developed to predict the vibration and acoustic responses of submerged coupled spherical-cylindrical-spherical shells stiffened by circumferential rings and longitudinal stringers. The structural model of the coupled stiffened shell is formulated using a modified variational method combined with a multi-segment partitioning technique, whereas a spectral Kirchhoff-Helmholtz integral formulation is employed to model the exterior fluid. The stiffened rings and stringers, which may be few or many in number, non-uniform or uniform in size, and non-uniformly or uniformly spaced, are treated as discrete elements. The displacement and sound pressure variables are expanded in the form of a double mixed series using Fourier series and Chebyshev orthogonal polynomials. This provides a flexible way for the present method to account for the individual contributions of circumferential wave modes to the vibration and acoustic responses of coupled stiffened shells in an analytical manner. The application of the method is illustrated with several numerical examples, and comparisons are made with available solutions obtained from the coupled finite element/boundary element method. The contributions of different circumferential wave modes to the vibration responses, sound power and the directivity of radiated sound pressure for coupled shells bounded by light or heavy fluid are examined. Effects of the rings and stringers on the vibration and acoustic responses of the coupled shells are investigated.
Hernandes, J. A.; E. Capelas De Oliveira; Assis, A. K. T.
2004-01-01
In this work we consider a long, resistive cylindrical shell carrying a steady current. A battery in the middle of the wire generates the current. We study the behavior of the potential, electric field and surface charges close to the batteryEn este trabajo consideramos una capa resistiva cilíndrica que transporta una corriente constante. Una batería genera la corriente en el centro del conductor. Estudiamos el comportamiento del potencial, campo eléctrico y cargas superficiales cerca de la b...
Delale, F.; Erdogan, F.
1977-01-01
The problem of a cylindrical shell containing a circumferential through crack is considered by taking into account the effect of transverse shear deformations. The formulation is given for a specially orthotropic material within the confines of a linearized shallow shell theory. The particular theory used permits the consideration of all five boundary conditions regarding moment and stress resultants on the crack surface. Consequently, aside from multiplicative constants representing the stress intensity factors, the membrane and bending components of the asymptotic stress fields near the crack tip are found to be identical. The stress intensity factors are calculated separately for a cylinder under a uniform membrane load, and that under a uniform bending moment. Sample results showing the nature of the out-of-plane crack surface displacement and the effect of the Poisson's ratio are presented.
The axial symmetric vibrations of cylindrical shell, filled by the flowing Gas-Liquid mixture
Directory of Open Access Journals (Sweden)
Grigoryan Sh.H.
2011-09-01
Full Text Available The problem of axial symmetric self–vibrations of the infinite long shell, filled by flowing gas bubbles of large and small sizes in fluid mixture is considered. The subsonic and supersonic regimes of the mixture flow are discussed. For vibration frequencies of the system under consideration are shown that shell frequencies with big bubbles–liquids mixture exceed the frequencies of system of with small gas bubbles–liquid mixture. In subsonic regime increasing of shell thickness brings to increasing of shell frequencies, as in case of shell with pure fluid. In subsonic regime the frequencies are increasing with decreasing of the flowing velocity, on the contrary, brings to decreasing of frequencies, similar to the case of shell with the pure fluid.
Directory of Open Access Journals (Sweden)
Ghulghazaryan G.R.
2011-03-01
Full Text Available The problem of existence of free vibrations of an elastic orthotropic open cylindrical shell (with arbitrary directional curve with free end, when other edges are rigid – clamped is studied. The investigation is carried out for elastic orthotropic shell when bending rigidity is vanishingly small (the moment free shell. The dispersion equations for finding the natural frequencies of vibrations are derived. The calculations were carried out for the shells with directing curve in form of a parabola with different values of curvature and lengths.
Institute of Scientific and Technical Information of China (English)
CHEN Meixia; LUO Dongping; PENG Xu; LUO Bin
2004-01-01
The characteristics of vibration and sound radiation from a double shell with the outer shell coated with viscoelastic layer are systematically studied. The shell's motion funcby three-dimensional Navier equations, whose displacement solutions are expressed by Taylor expansion along the layer thickness. The continuity conditions of displacement and stress between the shell and the layers are used in obtaining the vibration equations. The effects of layer thickness, modulus of elasticity, the loss factor, and the hydro-compressibility on the structural acoustic characteristic are discussed in detail. It showed that the higher the modulus of elasticity is, or the thinner the thickness of layer is, or the smaller the loss factor is, the higher the sound radiation power is.
International Nuclear Information System (INIS)
The two-dimensional dynamic interaction of progressive plane seismic waves with an arbitrarily thick, isotropic, and functionally graded cylindrical shell of infinite extent embedded in a boundless fluid-saturated porous elastic medium is investigated. The inhomogeneous shell is approximated by a laminate model, for which the solution is expected to gradually approach the exact one as the number of layers increases. Continuity of the displacement and stress components at the interfaces of neighboring layers is applied to form a system global transfer matrix, ultimately leading to determination of the modal scattering and transmission coefficients. The analytical results are illustrated with numerical examples in which an air-filled steel-zirconia FGM shell, buried in a water-saturated Ridgefield Sandstone formation, is insonified by fast compressional or shear waves at normal incidence. The effects of material compositional gradient and FGM layer thickness on the basic dynamic field quantities are evaluated and discussed. Limiting cases are considered and good agreements with the solutions available in the literature are obtained
Nakao, Ken-ichi; Harada, Tomohiro; Kurita, Yasunari; Morisawa, Yoshiyuki
2009-01-01
We numerically study the dynamics of an imploding hollow cylinder composed of dust. Since there is no cylindrical black hole in 4-dimensional spacetime with physically reasonable energy conditions, a collapsed dust cylinder involves a naked singularity accompanied by its causal future, or a fatal singularity which terminates the history of the whole universe. In a previous paper, the present authors have shown that if the dust is assumed to be composed of collisionless particles such that the...
LOAD CARRYING CAPABILITY OF LIQUID FILLED CYLINDRICAL SHELL STRUCTURES UNDER AXIAL COMPRESSION
Qasim H. Shah; MOHAMMAD MUJAHID; MUSHTAK AL-ATABI; YOUSIF A. ABAKR
2011-01-01
Empty and water filled cylindrical Tin (Sn) coated steel cans were loaded under axial compression at varying loading rates to study their resistance to withstand accidental loads. Compared to empty cans the water filled cans exhibit greater resistance to axially applied compression loads before a complete collapse. The time and load or stroke and load plots showed three significant load peaks related to three stages during loading until the cylinder collapse. First peak corresponds to the ini...
Cyril Touzé; Cédric Camier; Gaël Favraud; Olivier Thomas
2008-01-01
19 pages International audience The effect of geometric imperfections and viscous damping on the type of nonlinearity (i.e., the hardening or softening behaviour) of circular plates and shallow spherical shells with free edge is here investigated. The Von Kármán large-deflection theory is used to derive the continuous models. Then, nonlinear normal modes (NNMs) are used for predicting with accuracy the coefficient, the sign of which determines the hardening or softening behaviour of the...
Non-linear vibrations of laminated cylindrical shallow shells under thermomechanical loading
Ribeiro, P.; Jansen, E.
2008-08-01
The geometrically non-linear vibrations of linear elastic composite laminated shallow shells under the simultaneous action of thermal fields and mechanical excitations are analysed. For this purpose, a model based on a very efficient p-version first-order shear deformation finite element, with hierarchical basis functions, is employed. The equations of motion are solved in the time domain by a Newmark implicit time integration method. The model and code developed are partially validated by comparison with published data. Parametric studies are carried out in order to study the influence of temperature change, initial curvature, panel thickness and fibre orientation on the shells' dynamics.
International Nuclear Information System (INIS)
Different clamping conditions and variations of the material behaviour are considered. Especially the plastic strain concentrations at the shell clamping are determined. The analyses have been carried out with a finite-element code. Standard stress analysis procedures like the ASME-code are critically assessed. The results show that only minor plastic strain concentrations have to be expected for a rigidly clamped shell loaded by internal pressure. The work hardening characteristic of the material has little influence on these strain concentrations. On the other hand considerable plastic strain concentrations have to be expected at a flange type clamping loaded by axial stresses in the shell. These concentrations depend on the work hardening characteristic of the material. Comparison of these analyses with standard stress analysis procedures shows that these procedures are conservative, provided the classification of the different types of stresses has been done in a correct way which, however, may be difficult for some problems. For instance, for the rigidly clamped shell bending stresses can be classified as secondary stresses, but for a flange type clamping bending stresses must be treated as primary stresses with lower limits. With these results the structural integrity of the core barrel clamping of a PWR under blowdown loading has been assessed. Even in case of a sudden and complete pipe break the structure is able to withstand blowdown loading. (orig./HP)
Rahman, T.; Jansen, E.L.; Tiso, P.
2011-01-01
In this paper, a finite element-based approach for nonlinear vibration analysis of shell structures is presented. The approach makes use of a perturbation method that gives an approximation for the amplitude-frequency relation of the structure. The method is formulated using a functional notation an
Some applications of NASTRAN to the buckling of thin cylindrical shells with cutouts
Williams, J. G.; Starnes, J. H., Jr.
1972-01-01
The buckling of isotropic and waffle-stiffened circular cylinders with and without cutouts was studied using NASTRAN's Rigid Format 5 for the case of axial compressive loading. The results obtained for the cylinders without cutouts are compared with available reference solutions. The results for the isotropic cylinders containing a single circular cutout with selected radii are compared with available experimental data. For the waffle-stiffened cyclinder, the effect of two diametrically opposed rectangular cutouts was studied. A DMAP alter sequence was used to permit the necessary application of different prebuckling and buckling boundary conditions. Advantage was taken of available symmetry planes to formulate equivalent NASTRAN model segments which reduced the associated computational cost of performing the analyses. Limitations of the applicability of NASTRAN for the solution of problems with nonlinear characteristics are discussed.
Li, Yi-Wei; Elishakoff, Isaac; Starnes, James H., Jr.; Bushnell, David
1998-01-01
This study is an extension of a previous investigation of the combined effect of axisymmetric thickness variation and axisymmetric initial geometric imperfection on buckling of isotropic shells under uniform axial compression. Here the anisotropic cylindrical shells are investigated by means of Koiter's energy criterion. An asymptotic formula is derived which can be used to determine the critical buckling load for composite shells with combined initial geometric imperfection and thickness variation. Results are compared with those obtained by the software packages BOSOR4 and PANDA2.
Velikovich, A. L.; Schmit, P. F.
2015-11-01
Bell-Plesset effects accounting for the time dependence of the radius, velocity and acceleration of the Rayleigh-Taylor-unstable surface are ubiquitous in the instability of spherical laser targets and magnetically driven cylindrical liners. We present an analytical model that, for an ideal incompressible fluid and small perturbation amplitudes, exactly accounts for the Bell-Plesset effects in finite-thickness targets and liners through acceleration and deceleration phases. We derive the time-dependent dispersion equations determining the ``instantaneous growth rate'' and demonstrate that by integrating this growth rate over time (the WKB approximation) we accurately evaluate the number of perturbation e-foldings during the acceleration phase. In the limit of the small target/liner thickness, we obtain the exact thin-shell perturbation equations and approximate thin-shell dispersion relations, generalizing the earlier results of Harris (1962), Ott (1972) and Bud'ko et al. (1989). This research was supported by the US DOE/NNSA (A.L.V.), and in part by appointment to the Sandia National Laboratories Truman Fellowship in National Security Science and Engineering (P.F.S.), which is part of the Laboratory Directed Research and Development (LDRD) Program, Project No. 165746, and sponsored by Sandia Corporation (a wholly owned subsidiary of Lockheed Martin Corporation) as Operator of Sandia National Laboratories under its U.S. Department of Energy Contract No. DE-AC04-94AL85000.
Nakao, Ken-ichi; Kurita, Yasunari; Morisawa, Yoshiyuki
2009-01-01
We numerically study the dynamics of an imploding hollow cylinder composed of dust. Since there is no cylindrical black hole in 4-dimensional spacetime with physically reasonable energy conditions, a collapsed dust cylinder involves a naked singularity accompanied by its causal future, or a fatal singularity which terminates the history of the whole universe. In a previous paper, the present authors have shown that if the dust is assumed to be composed of collisionless particles such that these particles go through the symmetry axis of the cylinder, then the scalar polynomial singularity formed on the symmetry axis is so weak that almost all of geodesics are complete, and thus effectively no singularity forms by the collapse of a hollow dust cylinder. By contrast, in this paper, we assume that whole of the collapsed dust settles down on the symmetry axis by changing its equation of state. Obtained solutions are the straightforward extension of Morgan's null dust solution, in which no gravitational radiation i...
Agarwal, B. L.; Sobel, L. H.
1976-01-01
This work presents optimum designs for unstiffened, hat stringer-stiffened and honeycomb sandwich cylinders under axial compression. Optimization results for graphite-epoxy cylinders show about a 50 percent weight savings over corresponding optimized aluminum cylinders for a wide loading range. The inclusion of minimum gage considerations results in a significant weight penalty, especially for a lightly loaded cylinder. Effects of employing a smeared stiffener buckling theory in the optimization program are investigated through comparison of results obtained from a more accurate branched shell buckling computer code. It was found that the stiffener cross-sectional deformations, which are usually ignored in smeared stiffener theory, result in about a 30 percent lower buckling load for the graphite-epoxy hat stiffened cylinder.
Energy Technology Data Exchange (ETDEWEB)
Maeda, T.; Matsuura, N. [Obayashigumi Research Inst., Tokyo (Japan)
1997-10-01
Concerning the Sub-Arena being a part of the Osaka City Central Gymnasium which acted as the main meeting place of `Namihaya Athletics Meet` in 1997, its construction and results of predictive analyses were introduced in this paper. This area (Maishima isle) is covered with reclaimed soil until -6m in ground line (GL) and then with clay layer until -36m. The lower part from the above line is gravel layer, and the natural water level is GL-3m. Though the spherical shell roof assembled by PC can be found on the ground, the main body is a cylindrical earth self-retaining wall whose upper fringe is 0m in GL. The wall was composed of RC elements (thickness 1.2m) and made up a circle whose dia. was 52m by means of connection applying rigid joints. Though the bottom surface was GL-13m, the wall whose overall height was 39m was penetrated into gravel layer. Regarding predictive analyses for stress and deformation at the time of excavation, calculation factors were decided in accordance with guide-lines for basic design about underground connected wall by Obayashi-gumi Ltd. and the Japan Road Association. Deformation of the face of wall has been about 30mm at maximum at the most upper part whose value was about three times of analyzed value, and also increased about 5mm by the Hanshin earthquake. 3 refs., 12 figs.
Institute of Scientific and Technical Information of China (English)
YAO Xiong-liang; LIU Qing-jie; YU Xiu-bo
2007-01-01
The research on structural vibration and sound radiation of underwater ring-ribbed cylindrical shell, which is coated with a kind of deadening and decoupling materials, becomes a focus in recent years. This paper analyzes the problem on two aspects: model experiment and numerical calculation. The model experiment is carried out including three cases firstly, in which the structural vibration response and radiating acoustic field are measured respectively, and the results gained in these three cases are analyzed to discuss the effect of reducing structural vibration and radiating noise of the deadening and decoupling materials. The coupling FEM/BEM and the SEA methods are both used in numerical calculation, i.e. the arithmetic of the coupling FEM/BEM method is adopted to calculate the low frequency characteristics and the SEA method is adopted to calculate the medium-high frequencies characteristics of the model. By comparing experimental results with numerical calculation results, it is proved that the algorithm adopted in this paper is reasonable.
Energy Technology Data Exchange (ETDEWEB)
Hautala, K.; Schmidt, H.
1998-12-01
The buckling test program comprised 37 axially loaded cylinders made of austenitic stainless steels and 6 reference cylinders made of mild steel. The three test parameters were the steel grade, the shell slenderness and the operating temperature. The chosen steel grades are typical for practical applications: AISI 304 (No. 1.4301) as the basic austenitic stainless steel, AISI 316 L (No. 1.4404) as a molybdenum alloyed and AISI 316 Ti (No. 1.4571) as a molybdenum and titanium alloyed austenitic stainless steel. The chosen shell slendernesses are typical for the above-mentioned elastic-plastic region: r/t=50, 150 and 400, approximately corresponding to non-dimensional slenderness parameters {lambda}=0.3, 0.5 and 0.9 respectively. The chosen testing temperatures cover a wide range of applications: T=20 C, 100 C, 250 C and 400 C. The test cylinders were manufactured from 3.0 mm, 1.0 mm and 0.5 mm steel sheets, cold rolled into the cylindrical shape and longitudianlly TIG-welded. The radii were 150 mm and 200 mm, the length was 350 mm. (orig.) [German] Das Beulversuchsprogramm bestand aus 37 axialbelasteten Zylindern aus austenitischen rostfreien Staehlen und sechs Referenzzylindern aus Baustahl. Die drei Versuchsparameter waren die Stahlsorte, die Schalenschlankheit und die Betriebstemperatur. Die drei ausgewaehlten Stahlsorten sind typisch fuer baupraktische Anwendungen: WNr. 1.4301 (AISI 304) als einfachster, WNr. 1.4404 (AISI 316L) als ein Molybdaen-legierter und WNr. 1.4571 (AISI 316Ti) als ein Molybdaen- und Titanium-legierter austenitischer rostfreier Stahl. Die ausgewaehlten Schalenschlankheiten sind typisch fuer den oben erwaehnten elastisch-plastischen Bereich: r/t=50, 150 und 400, entsprechend dimensionslosen Schlankheitsparametern von naeherungsweise {lambda}=0.3, 0.5 und 0.9. Die ausgewaehlten Versuchstemperaturen decken ein breites Spektrum von Anwendungen ab: T=20 C, 100 C, 250 C und 400 C. Die Versuchszylinder wurden aus 3 mm, 1 mm, und 0.5 mm
Schmidt, J. M.; Cairns, Iver H.; Xie, Hong; St. Cyr, O. C.; Gopalswamy, N.
2016-03-01
Coronal mass ejections (CMEs) are major transient phenomena in the solar corona that are observed with ground-based and spacecraft-based coronagraphs in white light or with in situ measurements by spacecraft. CMEs transport mass and momentum and often drive shocks. In order to derive the CME and shock trajectories with high precision, we apply the graduated cylindrical shell (GCS) model to fit a flux rope to the CME directed toward STEREO A after about 19:00 UT on 29 November 2013 and check the quality of the heliocentric distance-time evaluations by carrying out a three-dimensional magnetohydrodynamic (MHD) simulation of the same CME with the Block Adaptive Tree Solar-Wind Roe Upwind Scheme (BATS-R-US) code. Heliocentric distances of the CME and shock leading edges are determined from the simulated white light images and magnetic field strength data. We find very good agreement between the predicted and observed heliocentric distances, showing that the GCS model and the BATS-R-US simulation approach work very well and are consistent. In order to assess the validity of CME and shock identification criteria in coronagraph images, we also compute synthetic white light images of the CME and shock. We find that the outer edge of a cloud-like illuminated area in the observed and predicted images in fact coincides with the leading edge of the CME flux rope and that the outer edge of a faint illuminated band in front of the CME leading edge coincides with the CME-driven shock front.
Dynamics of a coupled shell/fluid system
International Nuclear Information System (INIS)
A study of two concentrically located circular cylindrical shells containing and separated by fluids is presented. An exact frequency equation is derived for the general case and an approximate closed-form solution is obtained for the shell system with an incompressible fluid. It is found that the lowest frequency of the coupled system is associated with one of the out-of-phase modes, and is lower than the frequencies of the individual shells. (auth)
A high transmission broadband gradient index lens using elastic shell acoustic metamaterial elements
Titovich, Alexey S.; Haberman, Michael R.; Norris, Andrew N.
2016-01-01
The use of cylindrical elastic shells as elements in acoustic metamaterial devices is demonstrated through simulations and underwater measurements of a cylindrical-to-plane wave lens. Transformation acoustics (TA) of a circular region to a square dictates that the effective density in the lens remain constant and equal to that of water. Piecewise approximation to the desired effective compressibility is achieved using a square array with elements based on the elastic shell metamaterial concep...
International Nuclear Information System (INIS)
A series of tests investigating dynamic pulse buckling of a cylindrical shell under axial impact is compared to several 2D and 3D finite element simulations of the event. The purpose of the work is to investigate the performance of various analysis codes and element types on a problem which is applicable to radioactive material transport packages, and ultimately to develop a benchmark problem to qualify finite element analysis codes for the transport package design industry. During the pulse buckling tests, a buckle formed at each end of the cylinder, and one of the two buckles became unstable and collapsed. Numerical simulations of the test were performed using PRONTO, a Sandia developed transient dynamics analysis code, and ABAQUS/Explicit with both shell and continuum elements. The calculations are compared to the tests with respect to deformed shape and impact load history
International Nuclear Information System (INIS)
A periodic shell made of functionally graded material (FGM) is proposed in this Letter. Wave propagation and vibration transmission in the FGM periodic shell for different circumferential modes are investigated. By illustrating the dynamical behavior of the periodic FGM shell within the pass/stop band frequency ranges, the mechanism of wave propagation and vibration transmission in the shell are illuminated. Moreover, the suppression characteristics of structure-borne sound in the internal field of the shell, either within the stop or pass band frequency ranges, are studied. -- Highlights: ► Construction of a periodic shell used functionally graded material periodically. ► Investigation of wave propagation and vibration transmission. ► Dynamical behaviors and formation mechanism of band gap. ► Characteristics of acoustic pressure distribution.
Energy Technology Data Exchange (ETDEWEB)
Shen, Huijie; Wen, Jihong [Key Laboratory of Science and Technology on Integrated Logistics Support, National University of Defense Technology, Changsha 410073 (China); Païdoussis, Michael P. [Department of Mechanical Engineering, McGill University, Montreal, Québec, H3A OC3 (Canada); Yu, Dianlong [Key Laboratory of Science and Technology on Integrated Logistics Support, National University of Defense Technology, Changsha 410073 (China); Asgari, Meisam [Department of Mechanical Engineering, McGill University, Montreal, Québec, H3A OC3 (Canada); Wen, Xisen, E-mail: wenxs@vip.sina.com [Key Laboratory of Science and Technology on Integrated Logistics Support, National University of Defense Technology, Changsha 410073 (China)
2012-10-01
A periodic shell made of functionally graded material (FGM) is proposed in this Letter. Wave propagation and vibration transmission in the FGM periodic shell for different circumferential modes are investigated. By illustrating the dynamical behavior of the periodic FGM shell within the pass/stop band frequency ranges, the mechanism of wave propagation and vibration transmission in the shell are illuminated. Moreover, the suppression characteristics of structure-borne sound in the internal field of the shell, either within the stop or pass band frequency ranges, are studied. -- Highlights: ► Construction of a periodic shell used functionally graded material periodically. ► Investigation of wave propagation and vibration transmission. ► Dynamical behaviors and formation mechanism of band gap. ► Characteristics of acoustic pressure distribution.
The self–vibrations of cylindrical shell, filled by the flowing non viscous Gas-Liquid mixture
Directory of Open Access Journals (Sweden)
Ohanyan G.G.
2014-03-01
Full Text Available The problem of non-symmetrical self–vibrations of the infinite long shell, filled by the flowing non viscous Liquid with large or small sizes of bubbles is considered. The subsonic regime of the shell–mixture system with small bubbles which vibration frequencies exceed the frequencies values of those with the large bubbles is considered. The frequency values of the system is increased, when shell thickness and flow speed are increased as when vibration modes are decreased analogous to the case of shell with the pure liquids.
Titovich, Alexey S
2014-01-01
A thin infinitely long elastic shell is stiffened by $J$ in number identical lengthwise ribs distributed uniformly around the circumference and joined to a rod in the center. The 2D model of the substructure is a rigid central mass supported by $J$ axisymmetrically placed linear springs. The response of the shell-spring-mass system is quite different from a fluid filled shell or that of a solid cylinder due to the discrete number of contact points which couple the displacement of the shell at different locations. Exterior acoustic scattering due to normal plane wave incidence is solved in closed form for arbitrary $J$. The scattering matrix associated with the normal mode solution displays a simple structure, composed of distinct sub-matrices which decouple the incident and scattered fields into $J$ families. The presence of a springs-mass substructure causes resonances which are shown to be related to the subsonic shell flexural waves, and an approximate analytic expression is derived for the quasi-flexural ...
Institute of Scientific and Technical Information of China (English)
朱卫平; 黄黔
2002-01-01
The overall bending of circular ring shells subjected to bending moments and lateral forces is discussed. The derivation of the equations was based upon the theory of flexible shells generalized by E. L. Axelrad and the assumption of the moderately slender ratio less than 1/3 ( i. e. , ratio between curvature radius of the meridian and distance from the meridional curvature center to the axis of revolution ). The present general solution is an analytical one convergent in the whole domain of the shell and with the necessary integral constants for the boundary value problems. It can be used to calculate the stresses and displacements of the related bellows. The whole work is arranged into four parts: ( Ⅰ )Governing equation and general solution; ( Ⅱ ) Calculation for Omega-shaped bellows;( Ⅲ ) Calculation for C-shaped bellows; ( Ⅳ ) Calculation for U-shaped bellows. This paper is the first part.
Directory of Open Access Journals (Sweden)
Khaled M. Saadeldin Eldalil
2009-01-01
Full Text Available The load acting on the actively controlled cylindrical shell under a transient pressure pulse propelling a moving mass (gun case has been experimentally studied. The concept of using piezoelectric stack and stiffener combination is utilized for damping the tube wall radial and circumferential deforming vibrations, in the correct meeting location timing of the moving mass. The experiment was carried out by using the same stiffened shell tube of the experimental 14 mm gun tube facility which is used in part 1. Using single and double stacks is tried at two pressure levels of low-speed modes, which have response frequencies adapted with the used piezoelectric stacks characteristics. The maximum active damping ratio is occurred at high-pressure level. The radial circumferential strains are measured by using high-frequency strain gage system in phase with laser beam detection system similar to which used in part 1. Time resolved strain measurements of the wall response were obtained, and both precursor and transverse hoop strains have been resolved. A complete comparison had been made between the effect of active controlled and stepped structure cases, which indicate a significant attenuation ratio especially at higher operating pressures.
轴压作用下粘弹性柱壳的动力学行为%Dynamical Behavior of Viscoelastic Cylindrical Shells Under Axial Pressures
Institute of Scientific and Technical Information of China (English)
程昌钧; 张能辉
2001-01-01
The hypotheses of the Krmn-Donnell t heory of thin shells with large deflections and the Boltzmann laws for isotropic linear, viscoelastic materials, the constitutive equations of shallow shells ar e first derived. Then the governing equations for the deflection and stress func tion are formulated by using the procedure similar to establishing the Krmn equations of elastic thin plates. Introducing proper assumptions, an approximate theory for viscoelastic cylindrical shells under axial pressures can be obtaine d. Finally, the dynamical behavior is studied in detail by using several numeric al methods. Dynamical properties, such as, hyperchaos, chaos, strange attractor, limit cycle etc.,are discovered.%基于大挠度薄壳的Krmn-Donnell理论和 各向同性线粘弹性材料的Boltzmann定律， 首先推导了浅壳的本构方程， 然后利用与建立 弹性薄板Krmn方程类似的过程， 得到了关于挠度和应力函数的控制方程在 合适的假设下， 一种近似理论被用来分析轴压作用下粘弹性柱壳的力学行为最 后， 利用各种数值方法考察了粘弹性柱壳的动力学行为，发现了超混沌、混沌、奇怪吸引 子和极限环等多种动力学性质
Directory of Open Access Journals (Sweden)
Rakesh Singh Rajput,
2010-10-01
Full Text Available This paper deals with the effect of fluid presence on the non-axisymmetric dynamic response of imperfectly bonded buried orthotropic thick and thin fluid filled pipeline due to incident horizontal shear wave. In the thin shell theory the effect of shear deformation and rotary inertia is not considered. The pipeline has been modeled as an infinite cylindrical shell imperfectly bonded to surrounding. An approach similar to Dwivedi and Upadhyay (1989 has been followed wherein a thin layer is assumed between the shell and the surrounding medium (soil such that this layer possesses the properties of stiffness and damping both. The degree of imperfection of the bond is varied by changing the stiffness and the damping parameters of this layer. Although a general formulation including P-, SV- and SHwave excitations has been presented, numerical results are given for the case of incident SH-waves only. When it is excited by seismic-wave there are two types of soil movements that take place at the time of earthquake both around the epicenter. One is vertical movement (up and down of the soil and due to this movement the shearwave (S-V and S-H is developed on the surface of the pipe and other is horizontal movement (compressive or extend of the soil due to this the longitudinal wave or pressure wave or P-wave is developed on the surface of the pipe. Since it is not possible to condense the results for P-, SV- and SH-waves into one paper, in this paper theresults concerning only the shear waves (SH Wave are to be presented..With increasing urban population and its dependence on utility services, dynamic response of pipelines to seismic excitation has become a subject of importance.
International Nuclear Information System (INIS)
Displacement current is associated with the generation of magnetic fields due to time-varying electric fields. The harmonic response of a magneto-electro-elastic axisymmetric cylinder accounting for displacement current is carried out using the semi-analytical finite element method. The non-conservative electric field is represented using a magnetic vector potential. Studies are carried out for the first circumferential harmonics of the shell structure with the clamped–free boundary condition. The contribution made to the magnetic flux density by the electric displacement current is very small at lower frequencies but it becomes significant at higher frequencies
International Nuclear Information System (INIS)
A series of tests investigating dynamic pulse buckling of a cylindrical shell under axial impact is compared to several 2D and 3D finite element simulations of the event. The purpose of the work is to investigate the performance of various analysis codes and element types on a problem which is applicable to radioactive material transport packages, and ultimately to develop a benchmark problem to qualify finite element analysis codes for the transport package design industry. Four axial impact tests were performed on 4 in-diameter, 8 in-long, 304 L stainless steel cylinders with a 3/16 in wall thickness. The cylinders were struck by a 597 lb mass with an impact velocity ranging from 42.2 to 45.1 ft/sec. During the impact event, a buckle formed at each end of the cylinder, and one of the two buckles became unstable and collapsed. The instability occurred at the top of the cylinder in three tests and at the bottom in one test. Numerical simulations of the test were performed using the following codes and element types: PRONTO2D with axisymmetric four-node quadrilaterals; PRONTO3D with both four-node shells and eight-node hexahedrons; and ABAQUS/Explicit with axisymmetric two-node shells and four-node quadrilaterals, and 3D four-node shells and eight-node hexahedrons. All of the calculations are compared to the tests with respect to deformed shape and impact load history. As in the tests, the location of the instability is not consistent in all of the calculations. However, the calculations show good agreement with impact load measurements with the exception of an initial load spike which is proven to be the dynamic response of the load cell to the impact. Finally, the PRONIT02D calculation is compared to the tests with respect to strain and acceleration histories. Accelerometer data exhibited good qualitative agreement with the calculations. The strain comparisons show that measurements are very sensitive to gage placement
Institute of Scientific and Technical Information of China (English)
金广文; 章林柯; 缪旭弘; 贾地; 王雪仁
2011-01-01
研究水下双层圆柱壳体振动传递特性具有重要的工程意义,尤其对于水下结构噪声快速预报和外壳表面速度场实时重构.以此为出发点,通过双层加肋圆柱壳体模型水下振动试验研究了不同激励条件下内外壳体振动特性;然后建立了水下双层圆柱壳体有限元模型,计算分析了壳体在流固耦条件下的振动路径及特性,找出了不同激励方向、流体耦合方式和内外壳体连接方式等典型因素下内、外壳体间振动传递规律,为速度场重构和水下噪声预报提供了一定的理论指导.%In order to reconstruct velocity field and evaluate noise on outer shell surface of a submarine, vibration transmissibility between double shells of a submerged cylindrical double-shell structure was studied with underwater vibration test. An finite element model of a ribbed cylindrical double-shell was established here, its vibration response was analyzed. The law of vibration transmissibility for cylindrical double-shells in different forms was found, with typical influencing factors of fluid-structure coupling, exciting forces and connection condition between double shells. The results of tests and calculations provided some theoretical basis for velocity field reconstruction of outer shell and noise source identification of a submarine.
Experiments on shells under base excitation
Pellicano, Francesco; Barbieri, Marco; Zippo, Antonio; Strozzi, Matteo
2016-05-01
The aim of the present paper is a deep experimental investigation of the nonlinear dynamics of circular cylindrical shells. The specific problem regards the response of circular cylindrical shells subjected to base excitation. The shells are mounted on a shaking table that furnishes a vertical vibration parallel to the cylinder axis; a heavy rigid disk is mounted on the top of the shells. The base vibration induces a rigid body motion, which mainly causes huge inertia forces exerted by the top disk to the shell. In-plane stresses due to the aforementioned inertias give rise to impressively large vibration on the shell. An extremely violent dynamic phenomenon suddenly appears as the excitation frequency varies up and down close to the linear resonant frequency of the first axisymmetric mode. The dynamics are deeply investigated by varying excitation level and frequency. Moreover, in order to generalise the investigation, two different geometries are analysed. The paper furnishes a complete dynamic scenario by means of: (i) amplitude frequency diagrams, (ii) bifurcation diagrams, (iii) time histories and spectra, (iv) phase portraits and Poincaré maps. It is to be stressed that all the results presented here are experimental.
围壁补强的圆柱壳开孔结构有限元分析%Finite Element Analysis of Coaming Opening on the Cylindrical Shell
Institute of Scientific and Technical Information of China (English)
周猛猛; 杨宇华; 耿黎明; 刘朝骏
2014-01-01
The single radial opening is common on the pressure hull of submarine , and is stiffened by coaming usually .The ABAQUS software was utilized to calculate the stresses of cylindrical shell cut with single radial opening .The stress components were separated according to the equivalent principles to study the influence of coaming parameters upon stresses distribution , such as opening rate , thickness and height of coaming .%考虑到潜艇耐压壳上不可避免地要设置一些正交单圆孔，并采用围壁进行补强，利用ABAQUS通用有限元软件对该结构形式的系列模型进行求解，并利用等效原理分离出各应力成分，最终得出开孔率、围壁厚度、围壁高度以及围壁在壳体外的比例对各应力成分的影响规律。
A Geometric Theory of Nonlinear Morphoelastic Shells
Sadik, Souhayl; Angoshtari, Arzhang; Goriely, Alain; Yavari, Arash
2016-08-01
Many thin three-dimensional elastic bodies can be reduced to elastic shells: two-dimensional elastic bodies whose reference shape is not necessarily flat. More generally, morphoelastic shells are elastic shells that can remodel and grow in time. These idealized objects are suitable models for many physical, engineering, and biological systems. Here, we formulate a general geometric theory of nonlinear morphoelastic shells that describes both the evolution of the body shape, viewed as an orientable surface, as well as its intrinsic material properties such as its reference curvatures. In this geometric theory, bulk growth is modeled using an evolving referential configuration for the shell, the so-called material manifold. Geometric quantities attached to the surface, such as the first and second fundamental forms, are obtained from the metric of the three-dimensional body and its evolution. The governing dynamical equations for the body are obtained from variational consideration by assuming that both fundamental forms on the material manifold are dynamical variables in a Lagrangian field theory. In the case where growth can be modeled by a Rayleigh potential, we also obtain the governing equations for growth in the form of kinetic equations coupling the evolution of the first and the second fundamental forms with the state of stress of the shell. We apply these ideas to obtain stress-free growth fields of a planar sheet, the time evolution of a morphoelastic circular cylindrical shell subject to time-dependent internal pressure, and the residual stress of a morphoelastic planar circular shell.
Abrosimov, N. A.; Novosel'tseva, N. A.
2015-11-01
A method for identification of material parameters of the constitutive relations of elastoplastic and viscoelastic deformation of isotropic and composite materials is developed. The method is based on minimizing the functional of the residue of results of numerical and experimental analysis of unsteady deformation of structural elements made of examined materials. The method is tested, and prospects of its application for determining material parameters of viscoelastic and elastoplastic models of nonlinear deformation of cylindrical metal-plastic shells under explosive loading are demonstrated.
A high transmission broadband gradient index lens using elastic shell acoustic metamaterial elements
Titovich, Alexey S; Norris, Andrew N
2016-01-01
The use of cylindrical elastic shells as elements in acoustic metamaterial devices is demonstrated through simulations and underwater measurements of a cylindrical-to-plane wave lens. Transformation acoustics (TA) of a circular region to a square dictates that the effective density in the lens remain constant and equal to that of water. Piecewise approximation to the desired effective compressibility is achieved using a square array with elements based on the elastic shell metamaterial concept developed in [30]. The size of the elements are chosen based on availability of shells, minimizing fabrication difficulties. The tested device is neutrally buoyant comprising 48 elements of nine different types of commercial shells made from aluminum, brass, copper, and polymers. Simulations indicate a broadband range in which the device acts as a cylindrical to plane wave lens. The experimental findings confirm the broadband quadropolar response from approximately 20 to 40 kHz, with positive gain of the radiation patte...
Institute of Scientific and Technical Information of China (English)
李翔宇; 王马法; 董文朴; 梁民族
2015-01-01
This paper presents brief results of an experimental investigation on deformation shapes of cylindrical shell filled with soil subjected to lateral explosion loading,and the ultimate deformation shapes are obtained.Based on the experimental results,a corresponding analytical model is undertaken by using the plastic hinge theory.In the analytical model,the cylindrical shell is divided into several end-to-end rigid square bars.The deformation shape of cylindrical shell is described by the translation and rotation process of rigid square bars.The expressions of the spring force,moment and deflection angle between adjacent bars are deduced theoretically in detail.In addition,the blast loading conditions are studied in terms of the covering width of outer layer explosive and the initial velocity of cylindrical shell.Theoretical and experimental results show a good agreement,thus the analytical model can be considered as a valuable tool in understanding the deformation mechanism and predicting the deforma-tion shape of cylindrical shell under lateral contact explosion.The various deformation shapes of cylin-drical shell can be achieved by modifying the covering width of outer layer explosive and initial velocity of cylindrical shell.%对填充介质圆柱壳在侧向爆炸冲击作用下的变形型面进行了实验研究，获得了圆柱壳的最终变形型面。基于刚塑性动力学中的塑性铰理论建立了相应的分析模型，将圆柱壳划分为多个首尾相连的刚性方杆，利用方杆的平动、转动描述圆柱壳的变形过程，详细推导了相邻方杆间弹簧力、弯矩和偏折角等的表达式，考察了侧向炸药覆盖宽度和圆柱壳初始速度等因素对变形型面的影响。研究结果表明：所建立的分析模型能够有效地预测圆柱壳的变形型面，侧向炸药覆盖宽度和爆轰威力是影响圆柱壳最终变形型面的关键因素，可通过调整侧向炸药的覆盖宽
Mobility Power Flow (MPF) approach applied to a fluid-loaded shell with a plate bulkhead
McCain, Thomas Scott; Cuschieri, Joseph M.
Cylindrical shells, immersed in heavy fluids, coupled to plate-like bulkheads are commonly encountered in engineered structures. Often the performance of such systems is dependent upon the vibrational characteristics of the system as a whole or parts thereof. In distributed systems such as these, characterization of vibrational energy transmission between substructures, in addition to the vibrational response, is required for complete understanding of the vibrational characteristics of the system. In this paper, the vibrational characteristics of an infinite, thin cylindrical shell, immersed in an unbounded heavy fluid, coupled internally to a damped, circular plate is considered.
Resonant photoemission and magnetic x-ray circular dichroism in the M shell of ultrathin films of Fe
International Nuclear Information System (INIS)
Using magnetic ultra thin films (2--4 ml) of Fe on Cu(001) and bulk-like Fe, the Fe3p and Fe3s core states have been investigated with resonant photoemission and core-level photoemission, including, magnetic x-ray circular dichroism (MXCD) experiments. The resonant photoemission experiment has been done in fine steps over a wide photon energy range (hν = 695 eV - 715 eV), to probe the parentage of various spectral structures. The onset of secondary channels at the L3(hν = 707 eV) and L2(hν = 72O eV) edges will be analyzed in light of results from bulk Ni. The MXCD photoelectron spectroscopy of the Fe3p exhibits a 0.2 eV shift with circular polarization variation. The previously observed split peak structure in the Fe3s will be discussed with regard to the new resonant photoemission results. The resonant photoemission results will also be put into the context of our MXCD absorption results for monolayer and multilayers of Fe
Varied effects of shear correction on thermal vibration of functionally graded material shells
Directory of Open Access Journals (Sweden)
C.C. Hong
2014-12-01
Full Text Available The effects of varied shear correction coefficient on the first-order transverse shear deformation result of functionally graded material (FGM thick circular cylindrical shells under thermal vibration are investigated and computed by using the generalized differential quadrature method. The computed and varied values of shear correction coefficient are usually functions of FGM power law index and environment temperature. In the thermoelastic stress–strain relations, the simpler form stiffness of FGM shells under linear temperature rise is considered. The equation of shear correction coefficient is derived and obtained by using the total strain energy principle. Two parametric effects: environment temperature and FGM power law index on the thermal stress and center deflection of FGM thick circular cylindrical shells are obtained and investigated.
Circularly-Polarized Microstrip Antenna
Stanton, P. H.
1985-01-01
Microstrip construction compact for mobile applications. Circularly polarized microstrip antenna made of concentric cylindrical layers of conductive and dielectric materials. Coaxial cable feedlines connected to horizontal and vertical subelements from inside. Vertical subelement acts as ground for horizontal subelement.
Institute of Scientific and Technical Information of China (English)
陶襄樊; 陈美霞; 魏建辉
2012-01-01
水下双层加筋圆柱壳振动和辐射声场的预估对其噪声控制具有重要意义.以此为出发点,基于双层加筋圆柱壳干模态叠加原理,运用欠定盲分离方法,实现了有限数目测点预报结构振动和辐射声场的目的,并用数值方法对预报结果的有效性进行了验证.结果表明,欠定盲分离方法可以对水下双层加筋圆柱壳辐射声场进行预报,并且该预报方法对测点的位置、选取的模态阶数没有严格的要求,所需要的测点数目也较少,有很好的适用性.%The prediction of vibration and radiated acoustic field for double ring-stiffened cylindrical shell under water is of great importance to noise control. Based on the theory of modal superposition of double ring-stiffened cylindrical shell in vacuum, this paper proposes an underdetermined blind source separation method which achieves the aim of predicting the vibration and radiated acoustic field of the double ring-stiffened cylindrical shell under water with a few measuring points. The validity of the prediction results is analyzed through numerical method. It demonstrates that the prediction is reliable. And it does not has rigorous requirements on the location of the measuring points and the number of selected modes, otherwise, the number of the measuring points needed is acceptable, consequently, this method has much better applicability.
Institute of Scientific and Technical Information of China (English)
谢天宇; 王永生; 付建; 魏应三; 王旅
2013-01-01
The influence on the vibration and sound radiation of submarine with frame coated by damping layer is systematically studied.By finite element analysis of constrained damping plate is presented and the nature frequencies match with theoretical ones well,which verifies the rationality of damping model.After that,the numerical of analysis of sound radiation from a submerged cylindrical stiffened shell have been carried out by using FEM and BEM,which approximately equals to the testing results.Taking constrained damping plates and cylindrical stiffened shells with frame as research objects,analysis of the influence on vibration character of frame and the underwater sound radiation noise of stiffened cylindrical shells whether the constrained damping layer covers on frame in it.The result shows with constrained damping layer the radiation noise of cylindrical shell and its frame will be reduced effectively.%为研究敷设阻尼材料基座对艇体振动辐射噪声的影响,采用有限元法计算得到约束阻尼板的固有频率同理论值吻合较好,验证了阻尼材料建模的合理性;并利用有限元/边界元法分析了加肋柱壳受激后的水下声辐射,结果同试验值基本一致;最后以加筋板(裸基座)和含基座的加肋圆柱壳作为对象,计算分析了约束阻尼对裸基座振动特性的影响以及基座敷设阻尼材料前后壳体辐射声场的变化.结果表明:敷设约束阻尼能有效降低加肋圆柱壳体及其内部基座的辐射噪声.
Yan, Min; Qiu, Min
2008-01-01
Cylinder-shaped perfect lens deduced from the coordinate transformation method is proposed. The previously reported perfect slab lens is noticed to be a limiting form of the cylindrical lens when the inner radius approaches infinite with respect to the lens thickness. Connaturality between a cylindrical lens and a slab lens with the same thickness and equivalent material parameters is affirmed by comparing their eigen-field transfer functions. We numerically confirm the subwavelength imaging capability of such a cylindrical lens with consideration of material imperfection. The advantages of a cylindrical lens include finite structure size and ability to image with magnification or demagnification. Besides subwavelength imaging, its invisibility property implies that a cylindrical lens may also be valuable for non-invasive electromagnetic probing applications.
Serebryannikov, A. E.; Ozbay, Ekmel
2009-11-01
We demonstrate that a circular dielectric cylinder can be nearly invisible at multiple frequencies when being coated with a ring shell, which is made of an isotropic material simultaneously showing large positive or large negative values of permittivity and permeability. The suggested cloaking mechanism is based on the use of radial resonances, which are similar to those in conventional Fabry-Perot resonators. It can be used for cylindrical objects for a wide range of variation of the diameter-to-wavelength ratio, which includes the values corresponding to subwavelength to resonant-sized objects. The presence of frequency dispersion of the shell material positively affects the possibility of multifrequency operation.
Method of initial functions for thick transversely isotropic shells
International Nuclear Information System (INIS)
In the present work for circular cylindrical shells, three-dimensional elasticity equations are solved by assuming Taylor series expansions, in the radial direction, for the stresses and displacements. Depending upon the number of terms retained in the expansion, different order shell theories are derived. Classical theories (referred to as eighth-order), the shear deformation-transverse normal stress theories (referred to as tenth-order), and higher order theories (referred to as twelfth-order) are derived. In each case, by carrying out the symbolic algebra using the digital computer, partial differential equations are derived. The procedure was carried out in detail for the case of a circular cyclindrical shell with no loading on the interior surface and a given pressure distribution on the exterior surface. Then, numerical comparisons are made between the current theories and various shell theories, as well as the exact (three-dimensional) theory. Thus, using this method with its associated computer programs, one can realize a spectrum of approximate shell theories ranging from the classical thin shell, through all current thick shell theories, and approaching the three-dimensional elastic theories. (orig.)
Method of initial functions for thick transversely isotropic shells
Energy Technology Data Exchange (ETDEWEB)
Faraji, S. (Lowell Univ., MA (USA). Dept. of Civil Engineering); Archer, R.R. (Massachusetts Univ., Amherst (USA). Dept. of Civil Engineering)
1989-10-10
In the present work for circular cylindrical shells, three-dimensional elasticity equations are solved by assuming Taylor series expansions, in the radial direction, for the stresses and displacements. Depending upon the number of terms retained in the expansion, different order shell theories are derived. Classical theories (referred to as eighth-order), the shear deformation-transverse normal stress theories (referred to as tenth-order), and higher order theories (referred to as twelfth-order) are derived. In each case, by carrying out the symbolic algebra using the digital computer, partial differential equations are derived. The procedure was carried out in detail for the case of a circular cyclindrical shell with no loading on the interior surface and a given pressure distribution on the exterior surface. Then, numerical comparisons are made between the current theories and various shell theories, as well as the exact (three-dimensional) theory. Thus, using this method with its associated computer programs, one can realize a spectrum of approximate shell theories ranging from the classical thin shell, through all current thick shell theories, and approaching the three-dimensional elastic theories. (orig.).
Wang, Fei; Gong, Haoran; Chen, Xi; Chen, C Q
2016-01-01
Origami structures enrich the field of mechanical metamaterials with the ability to convert morphologically and systematically between two-dimensional (2D) thin sheets and three-dimensional (3D) spatial structures. In this study, an in-plane design method is proposed to approximate curved surfaces of interest with generalized Miura-ori units. Using this method, two combination types of crease lines are unified in one reprogrammable procedure, generating multiple types of cylindrical structures. Structural completeness conditions of the finite-thickness counterparts to the two types are also proposed. As an example of the design method, the kinematics and elastic properties of an origami-based circular cylindrical shell are analysed. The concept of Poisson's ratio is extended to the cylindrical structures, demonstrating their auxetic property. An analytical model of rigid plates linked by elastic hinges, consistent with numerical simulations, is employed to describe the mechanical response of the structures. Under particular load patterns, the circular shells display novel mechanical behaviour such as snap-through and limiting folding positions. By analysing the geometry and mechanics of the origami structures, we extend the design space of mechanical metamaterials and provide a basis for their practical applications in science and engineering. PMID:27624892
Varied effects of shear correction on thermal vibration of functionally graded material shells
Hong, C. C.
2014-01-01
The effects of varied shear correction coefficient on the first-order transverse shear deformation result of functionally graded material (FGM) thick circular cylindrical shells under thermal vibration are investigated and computed by using the generalized differential quadrature method. The computed and varied values of shear correction coefficient are usually functions of FGM power law index and environment temperature. In the thermoelastic stress–strain relations, the simpler form stiffnes...
On dynamic buckling of cylindrical shell in soil subjected to blast loads%爆炸荷载作用下土埋圆柱壳动力屈曲分析
Institute of Scientific and Technical Information of China (English)
刘新宇; 马林建; 方秦; 张川; 马淑娜
2012-01-01
To investigate the dynamic stability of cylindrical shell in shallow soil,the calculation model of soil spring-shell interaction was established based on the stress characteristic of the shell subjected to blast loads. The nonlinear FEM method was utilized to solve the structural dynamic responses. The B-R buckling rule was applied to determining the critical buckling load following the numerical simulation of the shell buckling progress. The influence of the soil layer deformation on the structural buckling load was analyzed in detail. The quantitative relationship between the buckling load of the structure and the elastic modulus of the soil was obtained. The results indicate that the structural buckling load increases nonlinear-ly with the soil elastic modulus.%为研究爆炸动载作用下土中圆柱壳结构的动力稳定特性,依据爆炸动载作用下土埋圆柱壳的受力特征,建立了考虑土与圆柱壳相互作用的土弹簧一柱壳计算模型,应用非线性有限元方法进行了数值计算.在圆柱壳结构动力屈曲过程数值分析的基础上,运用B-R屈曲准则判定土埋圆柱壳在爆炸动载作用下的屈曲临界荷载,并重点讨论了土层变形性质对圆柱壳屈曲荷载的影响,得到了土中圆柱壳屈曲荷载和土体弹性常数K的定量关系.结果表明,屈曲荷载随土体弹性常数的增大而非线性增大.
International Nuclear Information System (INIS)
It is shown that the existence of static, cylindrically symmetric wormholes does not require violation of the weak or null energy conditions near the throat, and cylindrically symmetric wormhole geometries can appear with less exotic sources than wormholes whose throats have a spherical topology. Examples of exact wormhole solutions are given with scalar, spinor and electromagnetic fields as sources, and these fields are not necessarily phantom. In particular, there are wormhole solutions for a massless, minimally coupled scalar field in the presence of a negative cosmological constant, and for an azimuthal Maxwell electromagnetic field. All these solutions are not asymptotically flat. A no-go theorem is proved, according to which a flat (or string) asymptotic behavior on both sides of a cylindrical wormhole throat is impossible if the energy density of matter is everywhere nonnegative.
Institute of Scientific and Technical Information of China (English)
于英霞; 刘丰军; 张伟; 梁斌
2012-01-01
The strength of ring-stiffened cylindrical shell is calculated and analyzed by using the finite element method.The failure state function is established based on the response surface method.First Order Reliability Method is studied and improved by combining with response surface method.By means of all random variables being converted into independent and normalized,the quadratic term of the failure state function is kept.The computational accuracy of the improved RSM-FORM in this paper is completely satisfied to the need of practical engineering.The reliability of ring-stiffened cylindrical shell is analyzed with RSM-FORM and the results indicate that RSM-FORM has a better calculation precision.%文章在用有限元法对结构进行强度计算和分析的基础上,应用RSM确定了环肋圆柱壳结构强度失效的功能函数;在对相关可靠度理论进行研究的基础上,将RSM与FORM相结合,对FORM进行了改进,解决了当量正态化和参数独立化问题,保留了功能函数的二次项,使计算精度满足实际工程的需要;最后用RSM-FORM对环肋圆柱壳结构强度的可靠性进行了计算分析,计算结果表明,RSM-FORM具有较好的计算精度.
Département des Ressources humaines
2004-01-01
Administrative Circular N° 2 (Rev. 2) - May 2004 Guidelines and procedures concerning recruitment and probation period of staff members This circular has been revised. It cancels and replaces Administrative Circular N° 2 (Rev. 1) - March 2000. Administrative Circular N° 9 (Rev. 3) - May 2004 Staff members contracts This circular has been revised. It cancels and replaces Administrative Circular N° 9 (Rev. 2) - March 2000. Administrative Circular N° 26 (Rev. 4) - May 2004 Procedure governing the career evolution of staff members This circular has also been revised. It Administrative Circulars Administrative Circular N° 26 (Rev. 3) - December 2001 and brings up to date the French version (Rev. 4) published on the HR Department Web site in January 2004. Operational Circular N° 7 - May 2004 Work from home This circular has been drawn up. Operational Circular N° 8 - May 2004 Dealing with alcohol-related problems...
Institute of Scientific and Technical Information of China (English)
李正良; 胡浩; 于伟
2015-01-01
Thefreevibrationofajoined,smoothandorthogonallystiffenedcylindrical-sphericalshellundervarious boundary conditions was studied.Based on the simplification of the joined part,the spherical shell is of free boundary condition and the cylindrical shell is of simply supported boundary condition.The Rayleigh-Ritz method was applied to solve the natural frequencies of the structure according to the Flügge's thin shell theory.The natural frequencies were calculated and compared with those by the finite element software ANSYS to confirm the applicability and validity of the simplification.The effects of the shallowness of the spherical shell and the length-to-radius ratio of the joined shell on the free vibrational behavior of the joined structure were investigated.The results indicate that as the semi-angle Φof the sphere increases,the natural frequencies decrease.As the length-to-radius ratio L/Rc increases,the influence of the semi-angle Φof the sphere on the natural frequencies decreases,the natural frequencies decrease gradually and their reducing magnitude descends.%研究不同边界条件下光滑、正交加筋圆柱壳－球壳组合结构的自由振动。通过对圆柱壳与球壳连接处简化处理，视球壳为自由约束，圆柱壳为简支约束，据Flügge 薄壳理论利用Rayleigh-Ritz 法求得结构频率，与有限元软件ANSYS结果比较，验证该方法的适用性及有效性；分析球壳扁率及组合壳体长径比对频率影响。结果表明，球心半角Φ增大结构自振频率降低；长径比L／Rc增大球心半角Φ对组合结构频率影响逐渐减弱，结构自振频率逐渐降低，且降幅减小。
Response of long shallow cylindrical panels to radial line loads
Johnson, E. R.; Hyer, M. W.; Carper, D. M.
1984-01-01
The large displacement static response of shallow orthotropic panels subjected to lateral loading is examined both theoretically and experimentally. The panels are circular cylindrical open shells which are also thin and long. The straight edges are simply supported at a fixed distance apart, and the curved edges are free. The lateral load is a spatially uniform line load acting along the generator direction of the cylinder, and is directed radially inward toward the center of curvature. The load induces a circumferential thrust, and the panel can, and does, snap-through to an inverted configuration at the buckling load. The effect of load position on the response is also examined. The test panels discussed in the paper are /(90/0)3/S graphite-epoxy laminates. Nominal dimensions are a radius of 60 in., a thickness of 0.060 in., and an arc length of 12 in. Very good agreement between theory and experiment is achieved.
The fundamental solution for a consistent complex model of the shallow shell equations
Directory of Open Access Journals (Sweden)
Matthew P. Coleman
1999-09-01
Full Text Available The calculation of the Fourier transforms of the fundamental solution in shallow shell theory ostensibly was accomplished by J. L. Sanders [J. Appl. Mech. 37 (1970, 361-366]. However, as is shown in detail in this paper, the complex model used by Sanders is, in fact, inconsistent. This paper provides a consistent version of Sanders's complex model, along with the Fourier transforms of the fundamental solution for this corrected model. The inverse Fourier transforms are then calculated for the particular cases of the shallow spherical and circular cylindrical shells, and the results of the latter are seen to be in agreement with results appearing elsewhere in the literature.
Creep analysis of orthotropic shells
International Nuclear Information System (INIS)
A method of creep analysis of orthotropic cylindrical shells subjected to axisymmetric loads has been developed. A general study of creep behaviour of cylindrical shells subjected to a uniform internal pressure has been conducted for a wide range of values of anisotropy coefficients and creep law exponent. Analysis includes determination of stress re-distribution, strain rates, stationary state stresses. Application of reference stress technique has been extended to analysis of shells. (author)
Institute of Scientific and Technical Information of China (English)
张焱冰; 任春雨; 朱锡
2014-01-01
In order to reduce the vibration and noise of submarines ,a FEM model of composite lami-nated cylindrical shell is established .The model is used for the investigation into its underwater vibra-tion and sound radiation .Based on the genetic algorithm (GA) ,the structural-acoustical optimization model is presented ,with the angle of laminated layers as design variable and the maximum sound pressure on the coupled interface as an object of optimization .The result shows that the optimizing design of the angle of the composite laminated cylindrical shell can improve its sound radiation effec-tively ,compared with the symmetrical laminated angle .The optimized far-field pressure level reduces 3 .6 dB on average in the frequency band of 50 Hz to 300 Hz .Therefore ,this optical design can pro-vide a certain reference for further study of the optimization of sound radiation from a large complex underwater structure .%为了降低艇体的振动噪声，建立了复合材料圆柱壳的有限元模型，并对其水下振动和声辐射特性进行了研究。在此基础上，分析了复合材料圆柱壳水下声辐射的优化模型；基于遗传优化算法，以复合材料铺层角度为设计变量，以流固耦合面内辐射声压的最大值为优化目标，进行了优化分析。结果表明：对复合材料圆柱壳的铺层角度进行优化设计可以有效提高其声辐射性能，相比对称铺层方式，优化后的远场辐射声压级在50～300 Hz频段内平均降低了3．6 dB。该结果验证了优化设计的有效性，为下一步进行大型复杂水下结构的声辐射优化研究提供了一定的思路。
Optimum rotationally symmetric shells for flywheel rotors
Blake, Henry W.
2000-01-01
A flywheel rim support formed from two shell halves. Each of the shell halves has a disc connected to the central shaft. A first shell element connects to the disc at an interface. A second shell element connects to the first shell element. The second shell element has a plurality of meridional slits. A cylindrical shell element connects to the second shell element. The cylindrical shell element connects to the inner surface of the flywheel rim. A flywheel rim support having a disc connected an outer diameter of a shaft. Two optimally shaped shell elements connect to the optimally shaped disc at an interface. The interface defines a discontinuity in a meridional slope of said support. A cylindrical shell element connects to the two shell elements. The cylindrical shell element has an outer surface for connecting to the inner surface of the flywheel rim. A flywheel rim casing includes an annular shell connected to the central shaft. The annular shell connects to the flywheel rim. A composite shell surrounds the shaft, annular shell and flywheel rim.
Cylindrical rotating triboelectric nanogenerator.
Bai, Peng; Zhu, Guang; Liu, Ying; Chen, Jun; Jing, Qingshen; Yang, Weiqing; Ma, Jusheng; Zhang, Gong; Wang, Zhong Lin
2013-07-23
We demonstrate a cylindrical rotating triboelectric nanogenerator (TENG) based on sliding electrification for harvesting mechanical energy from rotational motion. The rotating TENG is based on a core-shell structure that is made of distinctly different triboelectric materials with alternative strip structures on the surface. The charge transfer is strengthened with the formation of polymer nanoparticles on surfaces. During coaxial rotation, a contact-induced electrification and the relative sliding between the contact surfaces of the core and the shell result in an "in-plane" lateral polarization, which drives the flow of electrons in the external load. A power density of 36.9 W/m(2) (short-circuit current of 90 μA and open-circuit voltage of 410 V) has been achieved by a rotating TENG with 8 strip units at a linear rotational velocity of 1.33 m/s (a rotation rate of 1000 r/min). The output can be further enhanced by integrating more strip units and/or applying larger linear rotational velocity. This rotating TENG can be used as a direct power source to drive small electronics, such as LED bulbs. This study proves the possibility to harvest mechanical energy by TENGs from rotational motion, demonstrating its potential for harvesting the flow energy of air or water for applications such as self-powered environmental sensors and wildlife tracking devices. PMID:23799926
Institute of Scientific and Technical Information of China (English)
张琪昌; 费杰; 冯晶晶
2012-01-01
为深入研究薄壁圆柱壳在流体脉动激励下的运动特性,应用Donnell简化壳理论,考虑阻尼、结构非线性和附加质量的影响,建立了薄壁圆柱壳在流体脉动激励下的非线性振动方程.基于Galerkin方法将偏微分方程转化为方便求解的常微分方程,利用多尺度法求解了系统主共振的一次近似解,得到了系统稳态响应的转迁集与分岔图,并通过奇异性分析,得到了系统工作稳定性和可靠性的结构参数区域.对薄壁圆柱壳在流体作用下的振动特性进行了数值模拟和实验研究,考察了阻尼系数、脉动频率、液体深度等对系统动力学特性的影响.研究表明,考虑阻尼、结构非线性和附加质量的非线性振动方程更能体现薄壁圆柱壳在流体脉动激励下完整的动力学特性,同时系统中存在多种分岔行为.%In order to further research the characteristics of thin cylindrical shell excited by pulsating flow, considering the influences of damping, geometric nonlinearity and added mass, a nonlinear vibration equation under pulsating flow excitation was established by using Donnell's shallow-shell theory. The partial differential equation was transformed into an ordinary differential equation by using Galerkin method. By means of the method of multiple scales, the first approximate solution of the primary resonance of the system was acquired. The transition variety and bifurcation diagram in the unfolding parametric plane were given, the singularity and stability of the system were analysed and the stable regions of structural parameters were achieved. Experiments and numerical simulations were accomplished to study the impact of system parameters, such as the damping the pulsating frequency, the depth of liquid, etc. . The results show that the nonlinear vibration equation presented in the paper is better to reflect the dynamic characteristics, and various bifurcation behaviors existing in the system are
Antennas on circular cylinders
DEFF Research Database (Denmark)
Knudsen, H. L.
1959-01-01
antenna in a circular cylinder. By a procedure similar to the one used by Silver and Saunders, expressions have been derived for the field radiated from an arbitrary surface current distribution on a cylinder surface coaxial with a perfectly conducting cylinder. The cases where the space between the two...... cylindrical surfaces have the sane characteristic constants and different constants are treated separately. Extensive numerical computations of the field radiated from the slot antennas described here are being carried out, but no numerical results are yet available...
Institute of Scientific and Technical Information of China (English)
王天霖; 唐文勇; 张圣坤
2007-01-01
The effect of axial shallow groove on the nonlinear dynamic response and buckling of laminated cylindrical shells subjected to radial compression loading was investigated.Based on the first-order shear deformation theory(FSDT),the nonlinear dynamic equations involving the transverse shear deformation and initial geometric imperfections were derived with the Hamilton philosophy.The axial shallow groove of the laminated composite cylindrical shell was treated as the initial geometric imperfections in the dynamic equations.A semi-analytical method of expanding displacements and loads along the circumferential direction and employing the finite difference method along the axial direction and in the time domain is used to solve the governing equations and obtain the dynamic response of the laminated shell.The B-R criterion was employed to determine the critical loads of dynamic buckhng of the shell.The effects of the parameters of the shallow groove on the dynamic response and buckling were discussed in this paper and the results show that the axial shallow grooves greatly affect the dynamic response and buckling.
International Nuclear Information System (INIS)
Information circulars are published from time to time under the symbol INFCIRC/. . . . for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A list of the circulars which were of current interest on 15 January 1969 is given below, followed by an index to their subject matter. Other circulars can be traced by reference to earlier issues of the present document.
Investigation of dynamic characteristics of shells with holes and added mass
Directory of Open Access Journals (Sweden)
Seregin Sergey Valer’evich
2014-04-01
Full Text Available Thin cylindrical shells are widely used in construction, engineering and other industries. In case of designing a reservoir for the isothermal storage of liquefied gases such cases are inevitable, when housing requires various technical holes. A point wise added mass can appear into practice in the form of suspended spotlights, radar, architectural inclusions in buildings and structures of various purposes. It is known, that the dynamic asymmetry as an initial irregular geometric shape, including holes, and the added mass leads to specific effects in shells. In the paper the impact of a cut on the frequency and form of its own vibrations of thin circular cylindrical shells is theoretically examined with the help of the equations of linear shallow shell theory. For modal equations with Nav’e boundary conditions, we used the Bubnov - Galerkin method. The authors have expressed a formula for finding the lowest of the split-frequency vibrations of a shell with a cutout. It is stated, that in case of an appropriate choice of added mass value the lower frequencies are comparable with the case of vibrations of a shell with a hole. By numerical and experimental modeling and finite element method in the environment of MSC "Nastran" oscillation frequencies a shell supporting a concentrated mass and a shell with a cutout were compared. It is shown, that the results of the dynamic analysis of shells with holes with a suitable choice of the attached mass values are comparable with the results of the analysis of shells carrying a point mass. It was concluded that the edges in the holes, significantly affect the reduction in the lowest frequency, and need to be strengthened.
International Nuclear Information System (INIS)
Information circulars are published from time to time under the symbol INFCIRC/... for the purpose of bringing matters of general interest to the attention of all Members of the Agency. The present revision contains INFCIRCs published up to mid-August 1994. A complete numerical list of information circulars is reproduced with their titles in the Annex
International Nuclear Information System (INIS)
The document summarizes the Information Circulars published by the IAEA for the purpose of bringing matters of general interest to the attention of all Members of the Agency. This revision contains INFCIRCs published up to mid-August 1992. A complete numerical lift of Information Circulars with their titles is reproduced in an Annex
International Nuclear Information System (INIS)
The document summarizes the Information Circulars published by the IAEA for the purpose of bringing matters of general interest to the attention of all Member States. This revision contains INFCIRCs published up to the end of May 1999, grouped by field of activity. A complete list of information circulars in numerical order is given in an annex
International Nuclear Information System (INIS)
Information circulars are published from time to time under the symbol INFCIRC/. for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A list of the circulars that were current on 31 December 1964 is given, followed by an index to their subject matter.
International Nuclear Information System (INIS)
The document summarizes the Information Circulars published by the IAEA for the purpose of bringing matters of general interest to the attention of all Member States. This revision contains INFCIRCs published up to February 1997, grouped by field of activity. A complete list of information circulars in numerical order is given in an annex
International Nuclear Information System (INIS)
Information circulars are published from time to time under the symbol INFCIRC/... for the purpose of bringing matters of general interest to the attention of all Members of the Agency. The present revision contains INFCIRCs published up to the end of April 2002. A complete numerical list of information circulars is reproduced with their titles in the Annex
Inflation of Stressed Cylindrical Tubes: An Experimental Study
Guo, Zhiming; Wang, Shibin; Li, Linan; Ji, Hongwei; Wang, Zhiyong; Cai, Songbao
2013-01-01
The inflation of an initially stressed cylindrical shell provides a good illustration of the phenomenon of the initiation and propagation of an instability, which shares the same mathematical and mechanical features with a variety of other strain localization phenomena in engineering structures and materials. The high speed CCD camera and digital image processing system were used to measure the 3D shape of the inflated cylindrical tube. The localized bulge of a cylindrical tube with closed en...
Institute of Scientific and Technical Information of China (English)
王路才; 周其斗; 纪刚
2013-01-01
采用结构有限元耦合流体边界元的附加质量附加阻尼算法，建立了加肋有限圆柱壳体的有限元模型，并采用该模型对十四种方案的水下振动和声辐射进行了分析，讨论了模型边界条件对其水下振动和声辐射的影响规律以及在采用舱段模型代替整艇模型进行噪声估算时中间舱段长度的选取原则。结果表明用一个舱段模拟整艇的动态特性容易造成低频整体模态振型的缺失，在舱段首阶弯曲振动的模态频率以上，采用舱段来预报整艇的表面振动和辐射声功率是可以接受的；当整艇艇长不超过中间舱段长度的两倍时，可以采用舱段模型代替整艇模型进行噪声估算。%An additional mass and damping approach combining Finite Element Method (FEM) with Bound-ary Element Method (BEM) is proposed to calculate underwater vibration and acoustic radiation from a ring stiffened cylindrical shell with different boundary conditions. The comparison and analysis of the results show that using a cabin model of submarine replacing a full-scale model for vibration and noise estimation would stride over the low modes. When the frequency is exceeding the cabin’s first bending model fre-quency or the full length is less than twice of the cabin’s, using a cabin model replacing a full-scale mod-el for vibration and noise estimation is feasible.
Seismic response of flexible cylindrical tanks
International Nuclear Information System (INIS)
An experimental study of the seismic behavior of thin shell circular cylindrical liquid storage tanks is described. The investigation was planned to evaluate the adequacy of present methods of tank design, and was conducted using the Earthquake Simulator Facility of the University of California, Berkeley. The model tank considered in this paper was 6 ft high by 12 ft in diameter, and was welded from thin sheet aluminum to simulate a steel tank 36 feet in diameter. During testing the tank had an open top, held 60 inches of water, and was subjected to a time scaled El Centro (1940) earthquake, amplified to a peak acceleration of 0.5 g. Both base free and base fixed conditions were studied. Results of the experiments demonstrate that fluid pressures included both impulsive and convective components, and that the wave sloshing followed basic theory quite closely. But it also was apparent that the tank flexibility influenced the hydrodynamic pressures, as indicated by pressure amplification in the clamped tank, and by a total change of pressure history in the unclamped case. Significant out of round distortions of the tank were developed, of a three lobe form or the free base case and with four lobes in the fixed base case. Uplift of the tank base was closely related to the out-of-round deformation of the unanchored tank, whereas initial eccentricities apparently caused the section distortions in the anchored system. Stresses in the tank wall do not follow the expected pattern of response to overturning moment; instead they seem to be mainly associated with the section distortions. At present there is no analytical procedure for predicting these distortions
National Oceanic and Atmospheric Administration, Department of Commerce — Circular Updates are periodic sequentially numbered instructions to debriefing staff and observers informing them of changes or additions to scientific and specimen...
International Nuclear Information System (INIS)
The document summarizes the information circulars published by the IAEA for the purpose of bringing matters of general interest to the attention of all Members of the Agency. In the main body of the document only those documents which are regarded as likely to be of current interest are listed. A complete numerical list of information circulars with their titles is reproduced in the Annex
Institute of Scientific and Technical Information of China (English)
夏齐强; 陈志坚
2013-01-01
The vibro-acoustic design of the joint-structure in double-layer cylindrical shells was done from the viewpoint of attenuating vibration-wave transmission. Applying the theory of vibration reduction and isolation and the Snowdon’s isolator model, a new rubber-mass type joint-structure connected in the cylindrical shells was proposed. This structure is approximately a mass-spring-damping vibration reduction system with the characteristics of high elasticity and damping. Then, the vibro-acoustic characteristics of a double-layer cylindrical shell were analyzed numerically. Finally the effect of stiffness, damping and additional mass of the joint-structure on the vibro-acoustic performance of the double-layer cylindrical shell was discussed. The results show that the new-type connection can depress vibration and sound radiation effectively, the variation of stiffness, damping and additional mass of the joint-structure have a larger influence on the vibration attenuation and noise reduction efficiency. The research results can become a reference for submarine acoustic stealth design.% 从衰减振动波传递入手，对双层壳间连接结构进行了声振设计。运用减振隔振原理和Snowdon隔振模型，提出具有高弹性、高阻尼的近似质量—弹簧—阻尼减振特性的橡胶—质量块新型壳间连接结构，并对双层壳声振特性进行了数值仿真分析，最后讨论了连接元件刚度、材料阻尼和中间质量块变化对双层壳声振传递特性的影响。研究表明：提出的新型壳间连接结构能有效降低双层壳振动声辐射；弹性连接元件的刚度、阻尼和附加中间质量变化对减振降噪效果有较大的影响。研究结果可供潜艇声隐身设计参考。
Energy Technology Data Exchange (ETDEWEB)
Etienne, St.
1999-09-01
To compute the viscous flow around flexible circular cylinders arrays, a numerical model has been set up so solve the Reynolds averaged Navier-Stokes equations (RANSE). A domain decomposition method has been chosen to ensure the great flexibility of structures in the fluid domain. It consists in solving the RANS equations in a Eulerian way near the bodies and in a Lagrangian way in the wake(s). Then, we concentrate calculations in interest areas and we avoid mesh distortions. The resolution in the turbulent regime has been realized with k - {omega} and k - {epsilon} models. Compared with experiments, mix k - {omega} and k - {epsilon} models give the best results. Applications concern with the modeling of shielding and vortex-induced vibrations (VIV) phenomena in arrays of flexible cylinders. Results are validated by comparisons with experimental data. (authors)
Rotation, inversion and perversion in anisotropic elastic cylindrical tubes and membranes
Goriely, A.
2013-03-06
Cylindrical tubes and membranes are universal structural elements found in biology and engineering over a wide range of scales.Working in the framework of nonlinear elasticity, we consider the possible deformations of elastic cylindrical shells reinforced by one or two families of fibres. We consider both small and large deformations and the reduction from thick cylindrical shells (tubes) to thin shells (cylindrical membranes). In particular, a number of universal parameter regimes can be identified where the response behaviour of the cylinder is qualitatively different. This include the possibility of inversion of twist or axial strain when the cylinder is subject to internal pressure. Copyright © The Royal Society 2013.
2003-01-01
Operational Circular N° 4 - April 2003 Conditions for use by members of the CERN personnel of vehicles belonging to or rented by CERN - This circular has been drawn up. Operational Circular N° 5 - October 2000 Use of CERN computing facilities - Further details on the personal use of CERN computing facilities Operational Circular N° 5 and its Subsidiary Rules http://cern.ch/ComputingRules defines the rules for the use of CERN computing facilities. One of the basic principles governing such use is that it must come within the professional duties of the user concerned, as defined by the user's divisional hierarchy. However, personal use of the computing facilities is tolerated or allowed provided : a) It is in compliance with Operational Circular N° 5 and not detrimental to official duties, including those of other users; b) the frequency and duration is limited and there is a negligible use of CERN resources; c) it does not constitute a political, commercial and/or profit-making activity; d) it is not...
Cylindrical Helix Spline Approximation of Spatial Curves
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
In this paper, we present a new method for approximating spatial curves with a G1 cylindrical helix spline within a prescribed tolerance. We deduce the general formulation of a cylindrical helix,which has 11 freedoms. This means that it needs 11 restrictions to determine a cylindrical helix. Given a spatial parametric curve segment, including the start point and the end point of this segment, the tangent and the principal normal of the start point, we can always find a cylindrical segment to interpolate the given direction and position vectors. In order to approximate the known parametric curve within the prescribed tolerance, we adopt the trial method step by step. First, we must ensure the helix segment to interpolate the given two end points and match the principal normal and tangent of the start point, and then, we can keep the deviation between the cylindrical helix segment and the known curve segment within the prescribed tolerance everywhere. After the first segment had been formed, we can construct the next segment. Circularly, we can construct the G1 cylindrical helix spline to approximate the whole spatial parametric curve within the prescribed tolerance. Several examples are also given to show the efficiency of this method.
International Nuclear Information System (INIS)
The document summarizes the Information Circulars published by the IAEA under the symbol INFCIRC/ for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A complete list of INFCIRCs in numerical order with their titles is given in the Annex
Theoretical and experimental stress analyses of ORNL thin-shell cylinder-to-cylinder model 4
International Nuclear Information System (INIS)
The last in a series of four thin-shell cylinder-to-cylinder models was tested, and the experimentally determined elastic stress distributions were compared with theoretical predictions obtained from a thin-shell finite-element analysis. The models in the series are idealized thin-shell structures consisting of two circular cylindrical shells that intersect at right angles. There are no transitions, reinforcements, or fillets in the junction region. This series of model tests serves two basic purposes: (1) the experimental data provide design information directly applicable to nozzles in cylindrical vessels, and (2) the idealized models provide test results for use in developing and evaluating theoretical analyses applicable to nozzles in cylindrical vessels and to thin piping tees. The cylinder of model 4 had an outside diameter of 10 in., and the nozzle had an outside diameter of 1.29 in., giving a d0/D0 ratio of 0.129. The OD/thickness ratios were 50 and 20.2 for the cylinder and nozzle respectively. Thirteen separate loading cases were analyzed. For each loading condition one end of the cylinder was rigidly held. In addition to an internal pressure loading, three mutually perpendicular force components and three mutually perpendicular moment components were individually applied at the free end of the cylinder and at the end of the nozzle. The experimental stress distributions for each of the 13 loadings were obtained using 157 three-gage strain rosettes located on the inner and outer surfaces. Each of the 13 loading cases was also analyzed theoretically using a finite-element shell analysis developed at the University of California, Berkeley. The analysis used flat-plate elements and considered five degrees of freedom per node in the final assembled equations. The comparisons between theory and experiment show reasonably good agreement for this model. (U.S.)
Theoretical and experimental stress analyses of ORNL thin-shell cylinder-to-cylinder model 3
International Nuclear Information System (INIS)
The third in a series of four thin-shell cylinder-to-cylinder models was tested, and the experimentally determined elastic stress distributions were compared with theoretical predictions obtained from a thin-shell finite-element analysis. The models are idealized thin-shell structures consisting of two circular cylindrical shells that intersect at right angles. There are no transitions, reinforcements, or fillets in the junction region. This series of model tests serves two basic purposes: the experimental data provide design information directly applicable to nozzles in cylindrical vessels; and the idealized models provide test results for use in developing and evaluating theoretical analyses applicable to nozzles in cylindrical vessels and to thin piping tees. The cylinder of model 3 had a 10 in. OD and the nozzle had a 1.29 in. OD, giving a d0/D0 ratio of 0.129. The OD/thickness ratios for the cylinder and the nozzle were 50 and 7.68 respectively. Thirteen separate loading cases were analyzed. In each, one end of the cylinder was rigidly held. In addition to an internal pressure loading, three mutually perpendicular force components and three mutually perpendicular moment components were individually applied at the free end of the cylinder and at the end of the nozzle. The experimental stress distributions for all the loadings were obtained using 158 three-gage strain rosettes located on the inner and outer surfaces. The loading cases were also analyzed theoretically using a finite-element shell analysis developed at the University of California, Berkeley. The analysis used flat-plate elements and considered five degrees of freedom per node in the final assembled equations. The comparisons between theory and experiment show reasonably good agreement for this model. (U.S.)
Division des ressources humaines
2000-01-01
N° 2 (Rev. 1) - March 2000Guidelines and procedures concerning recruitment and probation period of staff membersN° 9 (Rev. 2) - March 2000Staff members contractsN° 16 (Rev. 2) - January 2000TrainingN° 30 (Rev. 1) - January 2000Indemnities and reimbursements upon taking up appointment and termination of contractN° 32 - February 2000Principles and procedures governing complaints of harassmentThese circular have been amended (No 2, N° 9, N° 16 and N° 30) or drawn up (N° 32).Copies are available in the Divisional Secretariats.Note:\tAdministrative and operational circulars, as well as the lists of those in force, are available for consultation in the server SRV4_Home in the Appletalk zone NOVELL (as GUEST or using your Novell username and password), volume PE Division Data Disk.The Word files are available in the folder COM, folder Public, folder ADM.CIRC.docHuman Resources DivisionTel. 74128
Multipole Analysis of Circular Cylindircal Magnetic Systems
Energy Technology Data Exchange (ETDEWEB)
J Selvaggi
2006-01-09
This thesis deals with an alternate method for computing the external magnetic field from a circular cylindrical magnetic source. The primary objective is to characterize the magnetic source in terms of its equivalent multipole distribution. This multipole distribution must be valid at points close to the cylindrical source and a spherical multipole expansion is ill-equipped to handle this problem; therefore a new method must be introduced. This method, based upon the free-space Green's function in cylindrical coordinates, is developed as an alternative to the more familiar spherical harmonic expansion. A family of special functions, called the toroidal functions or Q-functions, are found to exhibit the necessary properties for analyzing circular cylindrical geometries. In particular, the toroidal function of zeroth order, which comes from the integral formulation of the free-space Green's function in cylindrical coordinates, is employed to handle magnetic sources which exhibit circular cylindrical symmetry. The toroidal functions, also called Q-functions, are the weighting coefficients in a ''Fourier series-like'' expansion which represents the free-space Green's function. It is also called a toroidal expansion. This expansion can be directly employed in electrostatic, magnetostatic, and electrodynamic problems which exhibit cylindrical symmetry. Also, it is shown that they can be used as an alternative to the Elliptic integral formulation. In fact, anywhere that an Elliptic integral appears, one can replace it with its corresponding Q-function representation. A number of problems, using the toroidal expansion formulation, are analyzed and compared to existing known methods in order to validate the results. Also, the equivalent multipole distribution is found for most of the solved problems along with its corresponding physical interpretation. The main application is to characterize the external magnetic field due to a six
Notched double-curvature shells with cracks under pulsating internal pressure
International Nuclear Information System (INIS)
In the present paper, a double-curvature thin-walled shell with a surface crack starting from the root of an external circular-arc notch under cyclic loading is examined. The stress-intensity factor (SIF) along the elliptical-arc crack front is computed through a three-dimensional finite element analysis, for several elementary polynomial stress distributions perpendicular to the crack faces. By using the power series expansion of the actual stress field and the superposition principle, an approximate expression of the SIF in the case of a generic complex loading can be determined. Then the effect of the notch stress concentration on the SIF (and on the fatigue) behaviour is analysed for both cylindrical and spherical shells under (pulsating) internal pressure.
Elliptic Cylindrical Invisibility Cloak, a Semianalytical Approach Using Mathieu Functions
Cojocaru, E.
2008-01-01
An elliptic cylindrical wave expansion method by using Mathieu functions is developed to obtain the scattering field for a two-dimensional elliptic cylindrical invisibility cloak. The cloak material parameters are obtained from the spatial transformation approach. A near-ideal model of the invisibility cloak is set up to solve the boundary problem at the inner boundary in the cloak shell. The proposed design provides a more practical cloak geometry when compared to previous designs of ellipti...
International Nuclear Information System (INIS)
In the bi-monthly issues of 'Shell Venster' (window on Shell) attention is paid to the activities of the multinational petroleum company Shell Nederland and the Koninklijke/Shell Groep by means of non-specialist articles
Fluid-structure interaction for nonlinear response of shells conveying pulsatile flow
Tubaldi, Eleonora; Amabili, Marco; Païdoussis, Michael P.
2016-06-01
Circular cylindrical shells with flexible boundary conditions conveying pulsatile flow and subjected to pulsatile pressure are investigated. The equations of motion are obtained based on the nonlinear Novozhilov shell theory via Lagrangian approach. The flow is set in motion by a pulsatile pressure gradient. The fluid is modeled as a Newtonian pulsatile flow and it is formulated using a hybrid model that contains the unsteady effects obtained from the linear potential flow theory and the pulsatile viscous effects obtained from the unsteady time-averaged Navier-Stokes equations. A numerical bifurcation analysis employs a refined reduced order model to investigate the dynamic behavior. The case of shells containing quiescent fluid subjected to the action of a pulsatile transmural pressure is also addressed. Geometrically nonlinear vibration response to pulsatile flow and transmural pressure are here presented via frequency-response curves and time histories. The vibrations involving both a driven mode and a companion mode, which appear due to the axial symmetry, are also investigated. This theoretical framework represents a pioneering study that could be of great interest for biomedical applications. In particular, in the future, a more refined model of the one here presented will possibly be applied to reproduce the dynamic behavior of vascular prostheses used for repairing and replacing damaged and diseased thoracic aorta in cases of aneurysm, dissection or coarctation. For this purpose, a pulsatile time-dependent blood flow model is here considered by applying physiological waveforms of velocity and pressure during the heart beating period. This study provides, for the first time in literature, a fully coupled fluid-structure interaction model with deep insights in the nonlinear vibrations of circular cylindrical shells subjected to pulsatile pressure and pulsatile flow.
LINEAR AND NONLINEAR BUCKLING ANALYSIS OF STIFFENED CYLINDRICAL SUBMARINE HULL
Directory of Open Access Journals (Sweden)
SREELATHA P.R
2012-06-01
Full Text Available Submarine is a watercraft capable of independent operation under water. Use of submarines includes marine science, offshore industry underwater exploration etc. The pressure hull of submarine is constructed as combination of cylinders and domes. The shell is subjected to very high hydrostatic pressure, which creates large compressive stress resultants. Due to this the structure is susceptible to buckling. The introduction of stiffeners in both directions considerably increases the buckling strength of the shell. Since the stiffened cylindrical shell is susceptible to initial imperfections, nonlinear analysis is essential. The objective of this work is the linear and nonlinear analysis of the stiffened cylindrical shell subjected to very high hydrostatic pressure.Finite element method is a powerful tool for analysis of complex structures. Finite element package ANSYS is used for modeling and analysis the submarine hull.
Leung, Ka-Ngo
2008-04-22
A cylindrical neutron generator is formed with a coaxial RF-driven plasma ion source and target. A deuterium (or deuterium and tritium) plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical neutron generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which contain many slots. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired. The plasma generator may be in the center and the neutron target on the outside, or the plasma generator may be on the outside and the target on the inside. In a nested configuration, several concentric targets and plasma generating regions are nested to increase the neutron flux.
Dual frequency launcher for circularly polarized antenna
Chen, Ming H.
1989-10-01
A dual frequency antenna feed is formed from a central, circular waveguide connected to the flat boundry of circular, disk-shaped resonant cavity. A second circular waveguide is connected one end of a disk-shaped resonant cavity. Energy of one frequency enters and exits the cavity along the common axis of the waveguides. Energy of the second frequency is introduced to the same resonant cavity by way of a plurality of bandpass filters, also connected to the cavity. This energy enters by way of slots in the cylindrical walls of the cavity. The central circular waveguide is propagating at one frequency but cut off at the second frequency. These bandpass filters are at this pass band for the second frequency, but at the rejection band for the first frequency. Therefore, the isolation between these two input ports are obtained.
International Nuclear Information System (INIS)
In a cosmic dusty plasma, the dust-acoustic-wave propagation may be described by a cylindrical Kadomtsev-Petviashvili equation. In this Letter, for such modeling of environments like supernova shells, Saturn's F-ring, etc., cylindrical nebulons and an auto-Baecklund transformation are presented via symbolic computation. Nebulon structures are discussed, and possibly observable effects are proposed for cosmic plasmas
Cylindrical metamaterial-based subwavelength antenna
DEFF Research Database (Denmark)
Erentok, Aycan; Kim, Oleksiy S.; Arslanagic, Samel
2009-01-01
A subwavelength monopole antenna radiating in the presence of a truncated cylindrical shell, which has a capped top face and is made of a negative permittivity metamaterial, is analyzed numerically by a method of moments for the volume-surface integral equation oil the one hand, and a finite...... element method on the other hand. It is shown that a center-fed truncated cylinder, in contrast to an infinite cylinder, provides subwavelength resonances, thus suggesting the possibility, of having a subwavelength antenna system....
轴向运动层合薄壁圆柱壳内共振的数值分析%Internal resonance of axially moving laminated thin cylindrical shells
Institute of Scientific and Technical Information of China (English)
张宇飞; 王延庆; 闻邦椿
2015-01-01
以轴向运动复合材料薄壁圆柱壳为研究模型，考虑其弹性模量随振动频率变化（动态弹性模量），据Donnell非线性扁壳理论及经典层合壳理论获得模型非线性振动微分方程。采用含四个广义模态坐标的位移展开式，利用Galerkin方法对振动微分方程离散化；用变步长四阶Runge－Kutta法对非线性模态方程组进行数值积分，研究复合材料圆柱壳1：1：1：1的内共振现象；讨论圆柱壳轴向运动速度、阻尼系数及外激励幅值对系统1：1：1：1内共振响应作用。%Athincompositecircularcylindricalshellmovinginaxialdirectionwasinvestigated.Basedonthe Donnell's nonlinear shallow-shell theory,together with the classical laminated shell theory,a nonlinear vibration equation of the system was derived,in which the effects of dynamic Young's modulus,damping and geometric large deformation were considered.The modal expansion with four generalized modal coordinates was adopted,and the vibration equation was discretized by using the Galerkin method.Applying variable step-size four-order Runge-Kutta method,the nonlinear modal equations of the system was solved,and the nonlinear frequency response curves,which show 1:1:1:1 internal resonance phenomenon in the system were obtained.The effects of moving speed,damping coefficients and amplitudes of external force on the nonlinear vibration response of the shell were also analysed.
Bílek, Michal; a, Ivana Ebrov\\'; a, Kateřina Bartoškov\\'
2014-01-01
CONTEXT. Many ellipticals are surrounded by round stellar shells originating probably from minor mergers. A new method for constraining gravitational potential in elliptical galaxies was recently suggested. It uses the spectral line profiles of these shells to measure the circular velocity at the edge of the shell and the expansion velocity of the shell itself. MOND is an alternative to the dark matter framework aiming to solve the missing mass problem. AIMS. We study how the circular and expansion velocities behave in MOND for large shells. METHODS. The asymptotic behavior for infinitely large shells is derived analytically. The applicability of the asymptotic results for finitely sized shells is studied numerically on a grid galaxies modeled by S\\' ersic spheres. RESULTS. Circular velocity asymptotically settles at a value determined by the baryonic mass of the galaxy forming the baryonic Tully-Fisher relation known for disk galaxies. Shell expansion velocity also becomes asymptotically constant. The expans...
Cylindrical wormholes with positive cosmological constant
Richarte, Mart'\\in G
2013-01-01
We construct cylindrical, traversable wormholes with finite radii by taking into account the cut-and-paste procedure for the case of cosmic string manifolds with a positive cosmological constant. Under reasonable assumptions about the equation of state of the matter located at the shell, we find that the wormhole throat undergoes a monotonous evolution provided it moves at a constant velocity. In order to explore the dynamical nonlinear behaviour of the wormhole throat, we consider that the matter at the shell is supported by anisotropic Chaplygin gas, anti-Chaplygin gas, or a mixed of Chaplygin and anti-Chaplygin gases implying that wormholes could suffer an accelerated expansion or contraction but the oscillatory behavior seems to be forbidden.
Parametric vibrations and stability of viscoelastic shells
Ilyasov, M. H.
2010-05-01
The problem of dynamic stability of viscoelastic extremely shallow and circular cylindrical shells with any hereditary properties, including time-dependence of Poisson’s ratio, are reduced to the investigation of stability of the zero solution of an ordinary integro-differential equation with variable coefficients. Using the Laplace integral transform, an integro-differential equation is reduced to the new integro-differential one of which the main part coincides with the damped Hill equation and the integral part is proportional to the product of two small parameters. Changing this equation for the system of two linear equations of the first order and using the averaging method, the monodromy matrix of the obtained system is constructed. Considering the absolute value of the eigen-values of monodromy matrix is greater than unit, the condition for instability of zero solution is obtained in the three-dimensional space of parameters corresponding to the frequency, viscosity and amplitude of external action. Analysis of form and size of instability domains is carried out.
The Levitating Buddha: Constructing a Realistic Cylindrical Mirror Pseudo Image
Caussat, María Alicia; Rabal, Héctor; Muramatsu, Mikiya
2006-10-01
There are several interesting experiments involving image formation that can be easily implemented using mirrored foil, a very inexpensive material. When the foil is somewhat bent by holding its opposite edges and slightly pulling them together, cylindrical surfaces are generated. They behave as cylindrical mirrors, and circular or elliptical cross sections can be made. A project that can be easily built with the mirror foil is the generation of a pseudo image that is so compelling in its apparent reality that it can easily be taken to be the object itself.
Institute of Scientific and Technical Information of China (English)
毛勇建; 李玉龙; 陈颖; 黄含军; 张青平; 苗应刚
2012-01-01
A loading test by explosive rods to simulate mechanical effects of pulsed X-ray was numerically simulated by fluid-structure interaction method.The 2-D numerical model including a cylindrical shell,two layers of rubbers,nineteen explosive rods and a layer of air was built.Therein,the two rubber materials were described by Ogden hyperelastic models,the explosive rods and their explosion product were described by High Explosive Burn model and JWL equation of state,and the air was described by polynomial equation of state.The numerical simulation was performed by the multi-material ALE method.The physical images,load transmission and structural responses were obtained.The results show that,in the loading test of Ф265 mm cylindrical shell by 19 explosive rods to simulate a cosine-distributed load induced by X-ray,the stress responses at typical locations are basically equivalent.Furthermore,the additive two rubber layers can affect the response characteristics of the shells,and tightly glued interactions can distort the structural responses of shells with small mass and/or low stiffness.%对炸药条加载圆柱壳模拟X射线力学效应的试验进行了流固耦合数值模拟。首先建立了包括圆柱壳、两层缓冲橡胶、炸药条和空气在内的二维数值模型,其中,两层橡胶采用Ogden超弹性本构模型描述,炸药条及其爆轰产物采用高能炸药燃烧（High Explosive Burn）模型和JWL状态方程描述,空气采用多项式状态方程描述。然后采用多物质ALE流固耦合算法进行计算,获得了爆炸加载的物理图像、载荷传递与结构响应。结果表明,采用19条炸药条加载Ф265mm的圆柱壳模拟X射线余弦载荷作用,特征点应力响应基本等效;试验附加的两层橡胶对结构响应特征具有影响,在壳体质量较小和（或）刚度较低的情况下,紧密粘接会引起结构响应失真。
Nonlinear vibrations of shallow shells with complex boundary: R-functions method and experiments
Kurpa, Lidia; Pilgun, Galina; Amabili, Marco
2007-10-01
Geometrically nonlinear vibrations of shallow circular cylindrical panels with complex shape of the boundary are considered. The R-functions theory and variational methods are used to study the problem. The R-functions method (RFM) allows constructing in analytical form the sequence of basis functions satisfying the given boundary conditions in case of complex shape of the boundary. The problem is reduced to a single second-order differential equation with quadratic and cubic nonlinear terms. The method developed has been initially applied to study free vibrations of shallow circular cylindrical panels with rectangular base for different boundary conditions: (i) clamped edges, (ii) in-plane immovable simply supported edges, (iii) classically simply supported edges, and (iv) in-plane free simply supported edges. Then, the same approach is applied to a shell with complex shape of the boundary. Experiments have been conducted on an aluminum panel with complex shape of the boundary in order to identify the nonlinear response of the fundamental mode; these experimental results have been compared to numerical results.
Bílek, M.; Jungwiert, B.; Ebrová, I.; Bartošková, K.
2015-03-01
Context. Many ellipticals are surrounded by round stellar shells probably stemming from minor mergers. A new method for constraining gravitational potential in elliptical galaxies has recently been suggested. It uses the spectral line profiles of these shells to measure the circular velocity at the edge of the shell and the expansion velocity of the shell itself. MOND is an alternative to the dark matter framework aiming to solve the missing mass problem. Aims: We study how the circular and expansion velocities behave in MOND for large shells. Methods: The asymptotic behavior for infinitely large shells is derived analytically. The applicability of the asymptotic results for finitely sized shells is studied numerically on a grid of galaxies modeled with Sérsic spheres. Results: Circular velocity settles asymptotically at a value determined by the baryonic mass of the galaxy forming the baryonic Tully-Fisher relation known for disk galaxies. Shell expansion velocity also becomes asymptotically constant. The expansion velocities of large shells form a multibranched analogy to the baryonic Tully-Fisher relation, together with the galactic baryonic masses. For many - but not all - shell galaxies, the asymptotic values of these two types of velocities are reached under the effective radius. If MOND is assumed to work in ellipticals, then the shell spectra allow many details of the history to be revealed about the formation of the shell system, including its age. The results pertaining to circular velocities apply to all elliptical galaxies, not only those with shells.
46 CFR 59.15-10 - Bagged or blistered shell plates.
2010-10-01
... 46 Shipping 2 2010-10-01 2010-10-01 false Bagged or blistered shell plates. 59.15-10 Section 59.15... shell plates. (a) When the shell plates of cylindrical boilers which are exposed to the radiant heat of... boiler. (b) Where the shell plate is bagged due to overheating, the Officer in Charge, Marine...
Polar POLICRYPS diffractive structures generate cylindrical vector beams
International Nuclear Information System (INIS)
Local shaping of the polarization state of a light beam is appealing for a number of applications. This can be achieved by employing devices containing birefringent materials. In this article, we present one such enables converting a uniformly circularly polarized beam into a cylindrical vector beam (CVB). This device has been fabricated by exploiting the POLICRYPS (POlymer-LIquid CRYstals-Polymer-Slices) photocuring technique. It is a liquid-crystal-based optical diffraction grating featuring polar symmetry of the director alignment. We have characterized the resulting CVB profile and polarization for the cases of left and right circularly polarized incoming beams
Polar POLICRYPS Diffractive Structures Generate Cylindrical Vector Beams
Alj, Domenico; Volpe, Giovanni; Caputo, Roberto; Umeton, Cesare
2015-01-01
Local shaping of the polarization state of a light beam is appealing for a number of applications. This can be achieved by employing devices containing birefringent materials. In this article, we present one such device that permits one to convert a uniformly circularly polarized beam into a cylindrical vector beam (CVB). This device has been fabricated by exploiting the POLICRYPS photocuring technique. It is a liquid-crystal-based optical diffraction grating featuring polar symmetry of the director alignment. We have characterized the resulting CVB profile and polarization for the cases of left and right circularly polarized incoming beams.
Polar POLICRYPS diffractive structures generate cylindrical vector beams
Energy Technology Data Exchange (ETDEWEB)
Alj, Domenico; Caputo, Roberto, E-mail: roberto.caputo@fis.unical.it; Umeton, Cesare [Department of Physics and CNR-NANOTEC University of Calabria, I-87036 Rende (CS) (Italy); Paladugu, Sathyanarayana [Soft Matter Lab, Department of Physics, Bilkent University, Ankara 06800 (Turkey); Volpe, Giovanni [Soft Matter Lab, Department of Physics, Bilkent University, Ankara 06800 (Turkey); UNAM-National Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey)
2015-11-16
Local shaping of the polarization state of a light beam is appealing for a number of applications. This can be achieved by employing devices containing birefringent materials. In this article, we present one such enables converting a uniformly circularly polarized beam into a cylindrical vector beam (CVB). This device has been fabricated by exploiting the POLICRYPS (POlymer-LIquid CRYstals-Polymer-Slices) photocuring technique. It is a liquid-crystal-based optical diffraction grating featuring polar symmetry of the director alignment. We have characterized the resulting CVB profile and polarization for the cases of left and right circularly polarized incoming beams.
Circularity and Lambda Abstraction
DEFF Research Database (Denmark)
Danvy, Olivier; Thiemann, Peter; Zerny, Ian
2013-01-01
In this tribute to Doaitse Swierstra, we present the rst transformation between lazy circular programs a la Bird and strict cir- cular programs a la Pettorossi. Circular programs a la Bird rely on lazy recursive binding: they involve circular unknowns and make sense equa- tionally. Circular...... unknowns from what is done to them, which we lambda-abstract with functions. The circular unknowns then become dead variables, which we eliminate. The result is a strict circu- lar program a la Pettorossi. This transformation is reversible: given a strict circular program a la Pettorossi, we introduce...
Directory of Open Access Journals (Sweden)
M. Nicolet
2011-11-01
Full Text Available Computations of the phase matrix elements for single water droplets and ice crystals in fixed orientations are presented to determine if circular depolarization δ_{±C} is more accurate than linear depolarization for phase discrimination. T-matrix simulations were performed to calculate right-handed and left-handed circular depolarization ratios δ_{+C}, respectively δ_{−C} and to compare them with linear ones. Ice crystals are assumed to have a circular cylindrical shape where their surface-equivalent diameters range up to 5 μm. The circular depolarization ratios of ice particles were generally higher than linear depolarization and depended mostly on the particle orientation as well as their sizes. The fraction of non-detectable ice crystals (δ < 0.05 was smaller considering a circular polarized light source, reaching 4.5%. However, water droplets also depolarized light circularly for scattering angles smaller than 179° and size parameters smaller than 6 at side- and backscattering regions. Differentiation between ice crystals and water droplets might be difficult for experiments performing at backscattering angles which deviate from 180° unlike lidar applications. If the absence of the liquid phase is confirmed, the use of circular depolarization in single particle detection is more sensitive and less affected by particle orientation.
Viscous growth of thin pressurized shells subjected to thermal cycling
International Nuclear Information System (INIS)
This presentation describes the ratchetting or progressive growth of thin pressurized cylindrical shells, due to thermal cycling. In particular the analysis can be directed to the problem of ratchetting growth of the cladding of nuclear fuel elements. (orig.)
Magnetically induced cylindrical stress waves in a thermoelastic conductor
Chian, C. T.; Moon, F. C.
1981-01-01
The problem of stress wave generation in a linear thermoelastic solid by a pulsed magnetic field is investigated both analytically and experimentally for a cylindrically symmetric conducting solid. A dynamic response analysis is developed to correlate magnetic, thermal, and stress fields in the solid with the time history of the electric current. In the experiment, a transient magnetic field was applied normal to a large conducting plate with a circular hole. Initially the field was confined to the interior of the circular hole. The field was generated by discharging a large capacitor bank through a solenoidal coil. The plane-stress cylindrical stress waves are 1-D in nature. The relative effects of the magnetic body force and thermoelastic stresses, both generated by the electromagnetic field, are assessed.
Buckling localization in a cylindrical panel under axial compression
DEFF Research Database (Denmark)
Tvergaard, Viggo; Needleman, A.
2000-01-01
Localization of an initially periodic buckling pattern is investigated for an axially compressed elastic-plastic cylindrical panel of the type occurring between axial stiffeners on cylindrical shells. The phenomenon of buckling localization and its analogy with plastic flow localization in tensile......, but where subsequently the load starts to increase again, it is found that near the local load minimum, the buckling pattern switches back to a periodic type of pattern. The inelastic material behavior of the panel is described in terms of J(2) corner theory, which avoids the sometimes unrealistically...
Institute of Scientific and Technical Information of China (English)
周臻; 孟少平; 吴京
2011-01-01
基于时域分析方法对预应力双层柱面网壳结构的风振响应进行研究，采用Welch谱分析法对谐波叠加法与线性滤波技术（AR法）模拟得到的脉动风速时程进行功率谱精度评价；分析了预应力双层柱面网壳的矢跨比、跨度、厚度、长宽比、支座弹性刚度、预应力取值等结构参数对结构风振响应的影响，结果表明：网壳的矢跨比、跨度、长宽比是影响预应力双层柱面网壳结构风振响应的主要因素；预应力拉索有效地减小了结构的脉动风响应，但由于平均风响应同时也大幅减小，其位移风振系数仍较普通网壳结构大。基于包络的概念，采用以最大动响应和最大平均风响应为控制指标的整体风振系数计算方法，研究了常见设计参数情况的预应力双层柱面网壳结构整体风振系数，可为预应力双层柱面网壳的抗风设计提供实用方法。%The wind-induced response of prestressed double-layer cylindrical reticulated shells is researched based on the time-domain analytical method. The Welch spectrum analysis method is presented to evaluate the power spectrum accuracy of the fluctuating wind speed time-history simulated by the harmony superposition method and linear filter technique （AR method）. The influence of structural design parameters on the wind-induced response is investigated, including rise-span-ratio, span, thickness, length-width-ratio and the elastic support stiffness of the structure. Results show that the rise-span-ratio, span and length-width-ratio are the main factors influencing the structural wind-induced response. The existing of prestressed cable efficiently reduces the fluctuating wind induced response of the structure, while the displacement wind vibration coefficient is still greater than that of common non-prestressed reticulated shells since the average wind induced response is also reduced greatly. The global wind vibration
Institute of Scientific and Technical Information of China (English)
SHEN Guo-quan; XIAO Yuan-chun
2003-01-01
@@ "Mo" literally means "rubbing between two things"and "eliminating". Circular-rubbing is one of the earliest manipulations used in clinical practice. Circular-rubbing differs from pressing actually. Pressing is a static manipulation and acts to inhibit motion; circular-rubbing is a movable manipulation and serves to eliminate stationary. Circular-rubbing can be performed by either the palm or the finger.
Multidisciplinary optimization of a stiffened shell by genetic algorithm
International Nuclear Information System (INIS)
Vibration analysis of simply supported rotating cross-ply laminated stiffened cylindrical shell is performed using an energy approach which includes variational and averaging method. The stiffeners include rings and stringers. The equations are obtained by Rayleigh-Ritz method and Sander's relations. To validate the present method, the results are compared to the results available in other literatures. A good adoption is observed in different type of results including isotropic shells, rotating laminated shells, stiffened isotropic shells and stiffened laminated shells. Then, the optimization of parameters due to shell and stiffeners is conducted by genetic algorithm (GA) method under weight and frequency constraints. Stiffener shape, material properties and dimensions are also optimized
Chirped microlens arrays for diode laser circularization and beam expansion
Schreiber, Peter; Dannberg, Peter; Hoefer, Bernd; Beckert, Erik
2005-08-01
Single-mode diode lasers are well-established light sources for a huge number of applications but suffer from astigmatism, beam ellipticity and large manufacturing tolerances of beam parameters. To compensate for these shortcomings, various approaches like anamorphic prism pairs and cylindrical telescopes for circularization as well as variable beam expanders based on zoomed telescopes for precise adjustment of output beam parameters have been employed in the past. The presented new approach for both beam circularization and expansion is based on the use of microlens arrays with chirped focal length: Selection of lenslets of crossed cylindrical microlens arrays as part of an anamorphic telescope enables circularization, astigmatism correction and divergence tolerance compensation of diode lasers simultaneously. Another promising application of chirped spherical lens array telescopes is stepwise variable beam expansion for circular laser beams of fiber or solid-state lasers. In this article we describe design and manufacturing of beam shaping systems with chirped microlens arrays fabricated by polymer-on-glass replication of reflow lenses. A miniaturized diode laser module with beam circularization and astigmatism correction assembled on a structured ceramics motherboard and a modulated RGB laser-source for photofinishing applications equipped with both cylindrical and spherical chirped lens arrays demonstrate the feasibility of the proposed system design approach.
Measurement of cylindrical parts
Knight, Paul Douglas, Jr.
The form of cylindrical parts has been traditionally evaluated using stylus-based mechanical instruments. The Tropel Corporation has developed a grazing incidence interferometer (GII) for the measurement of cylindrical parts. The repeatability of this instrument due to various instrument uncertainties was measured. Differing instrument configurations that produce the same systematic error were determined to produce a zonal calibration method for determining systematic error over the full range of the instrument, given knowledge of the error in a single zone. The effect of the aperture stop on the response of the imaging system to axially sinusoidal artifacts was simulated. Diamond-turned axially sinusoidal artifacts, with amplitude of order1 um and spatial wavelength of order10 mm, were measured to test the axial response of the interferometer. The modulation transfer function of the instrument's imaging system, measured using a knife edge test, predicts the response observed with the sinusoidal artifacts. A diffraction analysis predicts that the measured axial form is modified by a second order envelope function with phase that varies with the relative position of the imaging system focal plane and part position. A compensation method is proposed for this effect. A comparison of roundness measurements by both a traditional stylus-based instrument and the GII was performed demonstrating that the roundness measurements of the two instruments are equivalent when the measurements are properly corrected for the differing effects of surface finish.
Dynamic Strength of Fiber Glass Shells
Syrunin, M.; Fedorenko, A.; Ivanov, A
1997-01-01
This paper presents generalization of results, obtained by experimental investigations of dynamic response, strength, and load-bearing ability of cylindrical and spherical shells, manufactured from composite materials on the basis of fiber glass, under loading them by explosion of compact high-explosive charges on the inside. The paper describes mechanisms and criteria of destruction of such shells, methods to improve their specific load-bearing ability. Results of experiments concerning inve...
Recent developments in anisotropic heterogeneous shell theory
Grigorenko, Alexander Ya; Grigorenko, Yaroslav M; Vlaikov, Georgii G
2016-01-01
This volume focuses on the relevant general theory and presents some first applications, namely those based on classical shell theory. After a brief introduction, during which the history and state-of-the-art are discussed, the first chapter presents the mechanics of anisotropic heterogeneous shells, covering all relevant assumptions and the basic relations of 3D elasticity, classical and refined shell models. The second chapter examines the numerical techniques that are used, namely discrete orthogonalization, spline-collocation and Fourier series, while the third highlights applications based on classical theory, in particular, the stress-strain state of shallow shells, non-circular shells, shells of revolution, and free vibrations of conical shells. The book concludes with a summary and an outlook bridging the gap to the second volume.
Hydrodynamics around cylindrical structures
Sumer, B Mutlu
2006-01-01
This book discusses the subject of wave/current flow around a cylinder, the forces induced on the cylinder by the flow, and the vibration pattern of slender structures in a marine environment. The primary aim of the book is to describe the flow pattern and the resulting load which develops when waves or current meet a cylinder. Special attention is paid to circular cylinder. The development in the forces is related to the various flow patterns and is discussed in detail. Regular as well as irregular waves are considered, and special cases like wall proximities (pipelines) are also investigated
Effective thermoelastic properties of composites with periodicity in cylindrical coordinates
Chatzigeorgiou, George
2012-09-01
The aim of this work is to study composites that present cylindrical periodicity in the microstructure. The effective thermomechanical properties of these composites are identified using a modified version of the asymptotic expansion homogenization method, which accounts for unit cells with shell shape. The microscale response is also shown. Several numerical examples demonstrate the use of the proposed approach, which is validated by other micromechanics methods. © 2012 Elsevier Ltd. All rights reserved.
Eyere Emagbetere; Oluleke Oluwole
2013-01-01
Road tankers are the most used means of transporting petroleum product to end users due to its cost effectiveness and energy-efficiency. The cylindrical tank has been well designed for by ASME VIII division 1 and 2 using analytical equations. Petrol tankers are not circular but elliptical probably for stability during transportation. This paper has used the finite element method to investigate in-plane displacements and Von-Mises stresses in both circular and elliptical cylindrical tanks und...
Dynamics and Control of Adaptive Shells with Curvature Transformations
Tzou, H.S.; Bao, Y.
1995-01-01
Adaptive structures with controllable geometries and shapes are rather useful in many engineering applications, such as adaptive wings, variable focus mirrors, adaptive machines, micro-electromechanical systems, etc. Dynamics and feedback control effectiveness of adaptive shells whose curvatures are actively controlled and continuously changed are evaluated. An adaptive piezoelectric laminated cylindrical shell composite with continuous curvature changes is studied, and its natural frequencie...
Directory of Open Access Journals (Sweden)
M. Nicolet
2012-05-01
Full Text Available Computations of the phase matrix elements for single water droplets and ice crystals in fixed orientations are presented to determine if circular depolarization δ_{C} is more accurate than linear depolarization for phase discrimination. T-matrix simulations were performed to calculate right-handed and left-handed circular depolarization ratios δ_{+C}, respectively δ_{−C} and to compare them with linear ones. Ice crystals are assumed to have a circular cylindrical shape where their surface-equivalent diameters range up to 5 μm. The circular depolarization ratios of ice particles were generally higher than linear depolarization and depended mostly on the particle orientation as well as their sizes. The fraction of non-detectable ice crystals (δ<0.05 was smaller considering a circular polarized light source, reaching 4.5%. However, water droplets also depolarized light circularly for scattering angles smaller than 179° and size parameters smaller than 6 at side- and backscattering regions. Differentiation between ice crystals and water droplets might be difficult for experiments performed at backscattering angles which deviate from 180° unlike LIDAR applications. Instruments exploiting the difference in the P_{44}/P_{11} ratio at a scattering angle around 115° are significantly constrained in distinguishing between water and ice because small droplets with size parameters between 5 and 10 do cause very high circular depolarizations at this angle. If the absence of the liquid phase is confirmed, the use of circular depolarization in single particle detection is more sensitive and less affected by particle orientation.
Rotating cylindrical wormholes and energy conditions
Bronnikov, K A
2015-01-01
We seek wormholes among rotating cylindrically symmetric configurations in general relativity. Exact wormhole solutions are presented with such sources of gravity as a massless scalar field, a cosmological constant, and a scalar field with an exponential potential. However, none of these solutions are asymptotically flat, which excludes the existence of wormhole entrances as local objects in our Universe. To overcome this difficulty, we try to build configurations with flat asymptotic regions using the cut-and-paste procedure: on both sides of the throat, a wormhole solution is matched to a properly chosen region of flat space-time at some surfaces $\\Sigma_-$ and $\\Sigma_+$. It is shown, however, that if the source of gravity in the throat region is a scalar field with an arbitrary potential, then one or both thin shells appearing on $\\Sigma_-$ and $\\Sigma_+$ inevitably violate the null energy condition. Thus, although rotating wormhole solutions are easily found without exotic matter, such matter is still ne...
PUBLICATION OF ADMINISTRATIVE CIRCULAR
HR Department
2008-01-01
ADMINISTRATIVE CIRCULAR NO. 23 (REV. 2) – SPECIAL WORKING HOURS Administrative Circular No. 23 (Rev. 2) entitled "Special working hours", approved following discussion in the Standing Concertation Committee meeting of 9 December 2008, will be available on the intranet site of the Human Resources Department as from 19 December 2008: http://cern.ch/hr-docs/admincirc/admincirc.asp It cancels and replaces Administrative Circular No. 23 (Rev. 1) entitled "Stand-by duty" of April 1988. A "Frequently Asked Questions" information document on special working hours will also be available on this site. Paper copies of this circular will shortly be available in departmental secretariats. Human Resources Department Tel. 78003
Publication of administrative circular
HR Department
2009-01-01
ADMINISTRATIVE CIRCULAR NO. 23 (REV. 2) – SPECIAL WORKING HOURS Administrative Circular No. 23 (Rev. 2) entitled "Special working hours", approved following discussion in the Standing Concertation Committee on 9 December 2008, will be available on the intranet site of the Human Resources Department as from 19 December 2008: http://cern.ch/hr-docs/admincirc/admincirc.asp It cancels and replaces Administrative Circular No. 23 (Rev. 1) entitled "Stand-by duty" of April 1988. A "Frequently Asked Questions" information document on special working hours will also be available on this site. Paper copies of this circular will shortly be available in Departmental Secretariats. Human Resources Department Tel. 78003
Raybould, T. A.; Fedotov, V. A.; Papasimakis, N.; Kuprov, I.; Youngs, I. J.; Chen, W. T.; Tsai, D. P.; Zheludev, N. I.
2016-07-01
We demonstrate that the induced toroidal dipole, represented by currents flowing on the surface of a torus, makes a distinct and indispensable contribution to circular dichroism. We show that toroidal circular dichroism supplements the well-known mechanism involving electric dipole and magnetic dipole transitions. We illustrate this with rigorous analysis of the experimentally measured polarization-sensitive transmission spectra of an artificial metamaterial, constructed from elements of toroidal symmetry. We argue that toroidal circular dichroism will be found in large biomolecules with elements of toroidal symmetry and should be taken into account in the interpretation of circular dichroism spectra of organics.
Dynamics and Control of Adaptive Shells with Curvature Transformations
Directory of Open Access Journals (Sweden)
H.S. Tzou
1995-01-01
Full Text Available Adaptive structures with controllable geometries and shapes are rather useful in many engineering applications, such as adaptive wings, variable focus mirrors, adaptive machines, micro-electromechanical systems, etc. Dynamics and feedback control effectiveness of adaptive shells whose curvatures are actively controlled and continuously changed are evaluated. An adaptive piezoelectric laminated cylindrical shell composite with continuous curvature changes is studied, and its natural frequencies and controlled damping ratios are evaluated. The curvature change of the adaptive shell starts from an open shallow shell (30° and ends with a deep cylindrical shell (360°. Dynamic characteristics and control effectiveness (via the proportional velocity feedback of this series of shells are investigated and compared at every 30° curvature change. Analytical solutions suggest that the lower modes are sensitive to curvature changes and the higher modes are relatively insensitive.
THE STRUCTURAL ANALYSIS OF STEEL SILOS WITH CYLINDRICAL-WALL BEARING AND PROFILE-STEEL BEARING
Zhengjun Tang; Daibiao Zhou; Chenwei Peng; Wenping Wu
2015-01-01
The silos are widely used in bulk material in many fields such as agriculture, mining, chemical, electric power storage, etc. Thin metal cylindrical silo shells are vulnerable to buckling failure caused by the compressive wall friction force. In this paper, the structural analysis of two types of steel silo with cylindrical-wall bearing and profile-steel bearing is implemented by Abaqus finite element analysis. The results indicate that under the same loading conditions, steel silos with prof...
Thin shells joining local cosmic string geometries
Eiroa, Ernesto F; Simeone, Claudio
2016-01-01
In this article we present a theoretical construction of spacetimes with a thin shell that joins two different local cosmic string geometries. We study two types of global manifolds, one representing spacetimes with a standard thin shell and the other corresponding to wormholes which are not symmetric across the throat located at the shell. We analyze the stability of the static configurations under perturbations preserving the cylindrical symmetry. For both types of geometries we find that the static configurations can be stable for suitable values of the parameters.
Vessel for cryogenic liquid with a flexible vacuum shell
International Nuclear Information System (INIS)
A 100 l vessel for a cryogenic liquid is described. Specific feature of its design is the substitution of a rigid cylindrical shell of vacuum jacket with a flexible shell made of 0.34 mm lawsan foil. Heat influx for a 82 l hydrogen vessel was 65 Wt. Inside the vessel an additional shell is mounted which diminishes 6 fold the heat influx to liquid hydrogen at an instant filling up of a vacuum space with air
DEFF Research Database (Denmark)
Hansen, Lennard Højbjerg
2014-01-01
It has been an accepted precept in film theory that specific stylistic features do not express specific content. Nevertheless, it is possible to find many examples in the history of film in which stylistic features do express specific content: for instance, the circular camera movement is used...... circular camera movement. Keywords: embodied perception, embodied style, explicit narration, interpretation, style pattern, television style...
New optical cylindrical microresonators
Gun'ko, Yurii K.; Balakrishnan, Sivakumar; McCarthy, Joseph E.; Rakovich, Yuri P.; Donegan, John F.; Perova, Tatiana S.; Melnikov, Vasily
2007-10-01
In this paper we describe a novel technique for the fabrication of aluminosilicate microfibres and microtubes which are shown to act as optical cylindrical microresonators. The alumosilicate microfibres and microtubes were fabricated by using vacuum-assisted wetting and filtration of silica gel through a microchannel glass matrix. The microfibres and microtubes were studied using Scanning Electron Microscopy (SEM), micro-photoluminescence spectroscopy and fluorescence lifetime imaging confocal microscopy. In the emission spectra of the micro-resonators we find very narrow periodic peaks corresponding to the whispering gallery modes of two orthogonal polarizations with quality factors up to 3200. A strong enhancement in photoluminescence decay rates at high excitation power demonstrates the occurrence of amplified spontaneous emission from a single microtube. These microtubes show a large evanescent field extending many microns beyond the tube radius. Potential applications for these novel microresonators will be in the area of optical microsensors for a single molecule detection of biological and chemical species, including anti-terrorism and defense sectors.
Perfect Circular Dichroic Metamirrors
Wang, Zuojia; Liu, Yongmin
2015-01-01
In nature, the beetle Chrysina gloriosa derives its iridescence by selectively reflecting left-handed circularly polarized light only. Here, for the first time, we introduce and demonstrate the optical analogue based on an ultrathin metamaterial, which we term circular dichroic metamirror. A general method to design the circular dichroic metasmirror is presented under the framework of Jones calculus. It is analytically shown that the metamirror can be realized by two layers of anisotropic metamaterial structures, in order to satisfy the required simultaneous breakings of n-fold rotational (n>2) and mirror symmetries. We design an infrared metamirror, which shows perfect reflectance for left-handed circularly polarized light without reversing its handedness, while almost completely absorbs right-handed circularly polarized light. These findings offer new methodology to realize novel chiral optical devices for a variety of applications, including polarimetric imaging, molecular spectroscopy, as well as quantum ...
International Nuclear Information System (INIS)
Dusty plasmas have been found almost everywhere in the Universe. In such cosmic dusty-plasma environments as the supernova shells and Saturn's F-ring, a cylindrical Kadomtsev-Petviashvili model is derived with symbolic computation for the dust ion-acoustic waves with azimuthal perturbation. Cylindrical nebulon structures are symbolically obtained, including the supernova-shell-typed expanding and shrinking bright nebulons and Saturn's-F-ring-typed expanding and shrinking dark nebulons. Possibly-observable nebulonic effects for the future cosmic plasma experiments are proposed
The dynamics of cylindrical samples in dual wind-up extensional rheometers
DEFF Research Database (Denmark)
Yu, Kaijia; Rasmussen, Henrik K.; Marín, Jose Manuel Román; Hassager, Ole
2011-01-01
Numerical computations of the extension of circular cylindrical shaped samples in a dual wind-up drum rheometer of Sentmanat extensional rheometer type M. L. Sentmanat, Rheol. Acta 43, 657 (2004); R. Garritano and H. Berting, US Patent No. 7,096,728 (08/29/2006) are presented. These time...
Structural shell analysis understanding and application
Blaauwendraad, Johan
2014-01-01
The mathematical description of the properties of a shell is much more elaborate than those of beam and plate structures. Therefore many engineers and architects are unacquainted with aspects of shell behaviour and design, and are not familiar with sufficiently reliable shell theories for the different shell types as derived in the middle of the 20th century. Rather than contributing to theory development, this university textbook focuses on architectural and civil engineering schools. Of course, practising professionals will profit from it as well. The book deals with thin elastic shells, in particular with cylindrical, conical and spherical types, and with elliptic and hyperbolic paraboloids. The focus is on roofs, chimneys, pressure vessels and storage tanks. Special attention is paid to edge bending disturbance zones, which is indispensable knowledge in FE meshing. A substantial part of the book results from research efforts in the mid 20th century at Delft University of Technology. As such, it is a valua...
Optimization of Cylindrical Hall Thrusters
International Nuclear Information System (INIS)
The cylindrical Hall thruster features high ionization efficiency, quiet operation, and ion acceleration in a large volume-to-surface ratio channel with performance comparable with the state-of-the-art annular Hall thrusters. These characteristics were demonstrated in low and medium power ranges. Optimization of miniaturized cylindrical thrusters led to performance improvements in the 50-200W input power range, including plume narrowing, increased thruster efficiency, reliable discharge initiation, and stable operation.
Pewsey, Arthur; Ruxton, Graeme D
2013-01-01
Circular Statistics in R provides the most comprehensive guide to the analysis of circular data in over a decade. Circular data arise in many scientific contexts whether it be angular directions such as: observed compass directions of departure of radio-collared migratory birds from a release point; bond angles measured in different molecules; wind directions at different times of year at a wind farm; direction of stress-fractures in concretebridge supports; longitudes of earthquake epicentres or seasonal and daily activity patterns, for example: data on the times of day at which animals are c
Inflation of stressed cylindrical tubes: an experimental study
Guo, Zhiming; Wang, Shibin; Li, Linan; Ji, Hongwei; Wang, Zhiyong; Cai, Songbao
2014-06-01
The inflation of an initially stressed cylindrical shell provides a good illustration of the phenomenon of the initiation and propagation of an instability, which shares the same mathematical and mechanical features with a variety of other strain localization phenomena in engineering structures and materials. The high speed CCD camera and digital image processing system were used to measure the 3D shape of the inflated cylindrical tube. The localized bulge of a cylindrical tube with closed ends forms when the internal pressure reaches a critical value Pcr. As more air is filled into the tube, the pressure drops but the radius at the centre of the bulge will increase until it reaches a maximum value rmax. With continued inflation, the pressure stays at a constant value Pp. The purpose of this study is to investigate the critical and propagation pressures in the tubes and the profile outside when the shells under axial tension and internal pressure were inflating. We focus on the influence of the axial tension on the critical pressure. In this paper the problem is explored through experimental efforts. A series of experiments were conducted on commercially available natural rubber latex tubes involving different geometries and initial axial tensions, which were regarded as isotropic, homogeneous, incompressible and hyper-elastic materials.
Creep deformations of shells of revolution under asymmetrical loading
International Nuclear Information System (INIS)
The numerical analysis of creep deformations of shells of revolution under unsymmetrical loads is described with application to a cylindrical shell. The analytical formulation of the creep of axisymmetric undergoing unsymmetrical deformations is developed for two hardening laws: the time hardening law and the strain hardening law. The method is based on the creep power law, and on the assumption of plane stress condition and the Euler-Bernoulli hypothesis used in the ordinary thin shell theory. The basic differential equations derived for incremental values with respect to time are numerically solved by a finite difference method and the solutions at any time are obtained by integration of the incremental values. In conclusion the computer programs are developed which can be used to predict the creep deformations of arbitrary axisymmetrical shells. As a numerical example the creep deformation of cylindrical shell of importance in practical use is treated, and the variations of displacements and internal forces with the lapse of time are discussed
DEFF Research Database (Denmark)
Almegaard, Henrik
2004-01-01
A new statical and conceptual model for membrane shell structures - the stringer system - has been found. The principle was first published at the IASS conference in Copenhagen (OHL91), and later the theory has been further developed (ALMO3)(ALMO4). From the analysis of the stringer model it can be...... concluded that all membrane shells can be described by a limited number of basic configurations of which quite a few have free edges....
Singularities and nonuniqueness in cylindrical flow of nematic liquid crystals
Van Hout, R.; Vilucchi, E
2001-01-01
The subject of this paper is the behavior of the director field of a nematic liquid crystal in flow through a tube with circular cross-section. Both the flow and the director field are assumed to have cylindrical symmetry. The requirement of finite Frank-Oseen energy forces ``admissible" director fields to be axially directed at the location of the symmetry axis. Thus, the angle between the axis and the director field at the location of the axis amounts to $k\\pi$, $k$ being an ...
Dynamic viscoelastic effects on sound wave scattering by an eccentric compound circular cylinder
Hasheminejad, Seyyed M.; Kazemirad, Siavash
2008-12-01
The classical method of separation of variables in conjunction with the translational addition theorem for cylindrical wave functions are employed to obtain an exact solution for two-dimensional interaction of a harmonic plane acoustic wave with an infinitely long (visco)elastic circular cylinder which is eccentrically coated by another (visco)elastic material and is submerged in an ideal unbounded acoustic medium. The novel features of Havriliak-Negami model for dynamic viscoelastic material behaviour are used to take the rheological properties of the coating (and/or core) material into consideration. The analytical results are illustrated with numerical examples in which a steel rod eccentrically coated with (an eccentric steel shell filled with) dissipative materials of distinct viscoelastic properties is insonified by plane sound waves at selected angles of incidence. The effects of incident wave frequency, angle of incidence, core eccentricity and dynamic viscoelastic material properties on the backscattered form function spectra are examined. Limiting cases are considered and fair agreements with available solutions are obtained.
Marston, Philip L.; Daniel, Timothy D.; Abawi, Ahmad T.; Kirsteins, Ivars
2015-11-01
The modulated radiation pressure (MRP) of ultrasound has been used for decades to selectively excite low frequency modes associated with surface tension of fluid objects in water. Much less is known about the excitation of low frequency modes of less compliant metallic objects. Here we use MRP of focused ultrasound to excite resonant flexural vibrations of a circular metal plate in water. The source transducer was driven with a double-sideband suppressed carrier voltage as in. The response of the target (detected with a hydrophone) was at twice the modulation frequency and proportional to the square of the drive voltage. Since the radiation pressure of focused beams is spatially localized, mode shapes could be identified by scanning the source along the target while measuring the target's response. Additional measurements were done with an open-ended water-filled copper circular cylindrical shell in which resonant frequencies and mode shapes were also identified. These experiments show how focused ultrasound can be used to identify low-frequency modes of elastic objects without direct contact. Supported by ONR.
Low Dimensional Models of Shell Vibrations. Parametrically Excited Vibrations of Cylinder Shells
Popov, A. A.; Thompson, J. M. T.; McRobie, F. A.
1998-01-01
Vibrations of cylindrical shells parametrically excited by axial forcing are considered. The governing system of two coupled non-linear partial differential equations is discretized by using Lagrange equations. The computation is simplified significantly by the application of computer algebra and as a result low dimensional models of shell vibrations are readily obtained. After applying numerical continuation techniques and ideas from dynamical systems theory, complete bifurcation diagrams are constructed. The principal aim is to investigate the interaction between different modes of shell vibration. Results for system models with two of the lowest modes are discussed.
Special features of embrittlement of welded joints in shells of VVER-type reactors
International Nuclear Information System (INIS)
At present, the atomic power engineering of Russia and Ukraine is based on water-water energy reactors of the VVER-440 and VVER-1000 type, with the electric power of 440 and 1000 MW, respectively. The majority of the VVER-440 reactors are installed in Russia, and VVER-1000 reactors operate in Ukraine. The reactors' shell (RS) is produced from cylindrical shells and a dished end welded together by circular joints under a flux. The RS of the VVER-440 reactor is produced from 15Kh3MFA steel, and the VVER-1000 reactors are produced from 15Kh2NMFA steel. The shell of the VVER-1000 reactor has an internal austenite coating. The condition of the RS metal is determined mainly by the critical brittleness temperature Tb at which the impact toughness of specimens with a sharp notch reaches 60 J/cm2. The energy reactors, working in western countries, are characterised by a service life of 40 years and discussion is being carried out to extend this lifetime to 60 years. The design service life of the domestic reactors varies from 30 (RS VVER-440) to 40 (RS VVER-1000) years. According to investigations, the service life of the shells of these reactors is restricted by the properties of welded joints which are characterised by higher susceptibility to embrittlement than that of the parent metal, especially due to a higher content in the weld of phosphorus (RS VVER-440) or nickel (RS VVER-1000). Therefore, some experts believe that the actual service life of the RS is shorter than the design life. The accurate evaluation of the service life of welded joints in the RS is very important for the safety of service and also in the economic aspects, because the unjustified decrease of the permissible service life and premature shutdown of units of the nuclear power station result in huge losses
Mikkelsen, Paula M
2002-01-01
In his contributions to the monographic series "Manual of Conchology", Henry Pilsbry reviewed the subgroup Tectibranchiata, comprising those opisthobranch snails that (at least primitively) still possess a shell (Pilsbry, 1894-1896). Exemplified by the Cephalaspidea (bubble shells), others included in this group at Pilsbry's time and since were Anaspidea (sea hares) and the shelled members of Notaspidea (side-gilled slugs) and Sacoglossa (leaf slugs). Pilsbry (and others since his time) considered tectibranchs to be the "root stock" from which more advanced gastropods such as Nudibranchia and Pulmonata were derived. Tectibranch systematics is firmly based on conchology and most species were originally described from empty shells. However, soft-anatomical characters were acknowledged quite early on as equally important in tectibranchs, due to the reduction of their shells and their evolutionary proximity to unshelled gastropods. Today, Tectibranchiata is not recognized as a natural taxon although the word "tectibranch" (like "prosobranch" and "mesogastropod") continues in vernacular use. Shelled opisthobranchs have been redistributed among various taxa, including several new ones--the unresolved basal opisthobranchs (Architectibranchia) and the "lower Heterobranchia", an enigmatic and currently much-studied group of families considered basal to all of Euthyneura (Opisthobranchia and landsnails (Pulmonata)). Despite their polyphyletic status, shelled opisthobranchs remain important subjects in evolutionary studies of gastropods--as the most basal members of nearly every opisthobranch clade and as organisms with mosaic combinations of primitive and derived features within evolutionary "trends" (e.g., loss of the shell, detorsion, concentration of the nervous system, ecological specialization, etc.). Although they play a pivotal role, the shelled opisthobranchs have received minimal attention in more comprehensive gastropod studies, often relegated to token
Directory of Open Access Journals (Sweden)
V. González Fernández
2001-07-01
Full Text Available Este trabajo se inserta en el desarrollo de los proyectos de estructuras cilíndricas presurizadas, evaluando y complementando losrecursos existentes para el proyecto de superficies de revolución sometidas a presión externa y considerando las formulacionesanalíticas que toman en cuenta los comportamientos no lineales, tanto geométrico como físico, importantes cuando se desea verificarel colapso de este tipo de estructuras.Con este trabajo se pretende la aplicación de métodos probabilísticos de análisis de resistencia al caso de estructuras en forma desuperficies de revolución sometidas a presión externa. Para cumplir este objetivo serán determinadas las cargas críticas con laformación de lóbulos circunferenciales según la teoría de Reynolds, tomando en consideración las variaciones de algunos parámetrosgeométricos que influyen en esta carga.Palabras claves: Estructura, estabilidad, falla estructural, imperfección geométrica, superficie a presión.______________________________________________________________________________Abstract:This work is inserted in the development of the projects of cylindrical structure under pressure, evaluating and supplementing theexistent resources for the project of circular cylindrical surface under external pressure. In the same are considered the analyticformulations to take into account the non-linear behaviours, (geometric and physic when is necessary to verify the collapse of thistype of structures.The application of probabilistic methods of resistance analysis to the case of structures with shape of cylindrical shell under externalpressure is sought. To complete this objective the critical loads are determined according to Reynolds’s theory taking intoconsideration the variations of some geometric parameters with influence in this load.Key words: Structures, stability, structural failures, imperfections, cylindrical shell under external pressure.
Cylindrical active coated nano-particles excited by electric and magnetic line sources
DEFF Research Database (Denmark)
Arslanagic, Samel; Liu, Y.; Malureanu, Radu;
2011-01-01
Cylindrical active coated nano-particles comprised of a silica nano-cylinder core covered with a plasmonic nano-shell are investigated with regard to their near- and far-field properties. The source of excitation is taken to be an electric or a magnetic line current, while three different plasmonic...
Cylindrical acoustic levitator/concentrator
Energy Technology Data Exchange (ETDEWEB)
Kaduchak, Gregory (Los Alamos, NM); Sinha, Dipen N. (Los Alamos, NM)
2002-01-01
A low-power, inexpensive acoustic apparatus for levitation and/or concentration of aerosols and small liquid/solid samples having particulates up to several millimeters in diameter in air or other fluids is described. It is constructed from a commercially available, hollow cylindrical piezoelectric crystal which has been modified to tune the resonance frequency of the breathing mode resonance of the crystal to that of the interior cavity of the cylinder. When the resonance frequency of the interior cylindrical cavity is matched to the breathing mode resonance of the cylindrical piezoelectric transducer, the acoustic efficiency for establishing a standing wave pattern in the cavity is high. The cylinder does not require accurate alignment of a resonant cavity. Water droplets having diameters greater than 1 mm have been levitated against the force of gravity using; less than 1 W of input electrical power. Concentration of aerosol particles in air is also demonstrated.
Free vibration analysis of delaminated composite shells using different shell theories
International Nuclear Information System (INIS)
Free vibration response of laminated composite shells with delamination is presented using the finite element method based on first order shear deformation theory. The shell theory used is the extension of dynamic, shear deformable theory according to the Sanders' first approximation for doubly curved shells, which can be reduced to Love's and Donnell's theories by means of tracers. An eight-noded C0 continuity, isoparametric quadrilateral element with five degrees of freedom per node is used in the formulation. For modeling the delamination, multipoint constraint algorithm is incorporated in the finite element code. The natural frequencies of the delaminated cylindrical (CYL), spherical (SPH) and hyperbolic paraboloid (HYP) shells are determined by using the above mentioned shell theories, namely Sanders', Love's, and Donnell's. The validity of the present approach is established by comparing the authors' results with those available in the literature. Additional studies on free vibration response of CYL, SPH and HYP shells are conducted to assess the effects of delamination size and number of layers considering all three shell theories. It is shown that shell theories according to Sanders and Love always predict practically identical frequencies. Donnell's theory gives reliable results only for shallow shells. Moreover, the natural frequency is found to be very sensitive to delamination size and number of layers in the shell.
Vibrations of moderately thick shallow spherical shells at large amplitudes
Sathyamoorthy, M.
1994-04-01
A shallow shell theory is presented for the geometrically nonlinear analysis of moderately thick isotropic spherical shells. Effects of transverse shear deformation and rotatory inertia are included in the governing equations of motion by means of tracing constants. When these effects are ignored, the governing equations readily reduce to those applicable for thin shallow spherical shells. Solutions to the system of thick shell equations are obtained by means of Galerkin's method and the numerical Runge-Kutta procedure. Numerical results are presented for certain cases of shallow spherical shells considering different geometric shell parameters. Transverse shear and rotatory inertia effects are found to be important in linear as well as nonlinear responses of shallow spherical shells. The nonlinear frequency-amplitude behavior is of the softening type for shallow spherical shells and of the hardening type for circular plates. Frequency ratios are lower at any given amplitude when the effects of transverse shear and rotatory inertia are included in the analysis.
Compact waveguide circular polarizer
Energy Technology Data Exchange (ETDEWEB)
Tantawi, Sami G.
2016-08-16
A multi-port waveguide is provided having a rectangular waveguide that includes a Y-shape structure with first top arm having a first rectangular waveguide port, a second top arm with second rectangular waveguide port, and a base arm with a third rectangular waveguide port for supporting a TE.sub.10 mode and a TE.sub.20 mode, where the end of the third rectangular waveguide port includes rounded edges that are parallel to a z-axis of the waveguide, a circular waveguide having a circular waveguide port for supporting a left hand and a right hand circular polarization TE.sub.11 mode and is coupled to a base arm broad wall, and a matching feature disposed on the base arm broad wall opposite of the circular waveguide for terminating the third rectangular waveguide port, where the first rectangular waveguide port, the second rectangular waveguide port and the circular waveguide port are capable of supporting 4-modes of operation.
Cloaking by shells with radially inhomogeneous anisotropic permittivity.
Reshetnyak, V Yu; Pinkevych, I P; Sluckin, T J; Evans, D R
2016-01-25
We model electromagnetic cloaking of a spherical or cylindrical nanoparticle enclosed by an optically anisotropic and optically inhomogeneous symmetric shell, by examining its electric response in a quasi-static uniform electric field. When the components of the shell permittivity are radially anisotropic and power-law dependent (ε~rm) whereris distance to the shell center, and m a positive or negative exponent which can be varied), the problem is analytically tractable. Formulas are calculated for the degree of cloaking in the general case, allowing the determination of a dielectric condition for the shells to be used as an invisibility cloak. Ideal cloaking is known to require that homogeneous shells exhibit an infinite ratio of tangential and radial components of the shell permittivity, but for radially inhomogeneous shells ideal cloaking can occur even for finite values of this ratio. PMID:26832575
Phase transition properties of a cylindrical ferroelectric nanowire
Indian Academy of Sciences (India)
Wang Ying; Yang Xiong
2013-11-01
Based on the transverse Ising model (TIM) and using the mean-field theory, we investigate the phase transition properties of a cylindrical ferroelectric nanowire. Two different kinds of phase diagrams are constructed. We discuss systematically the effects of exchange interactions and the transverse field parameters on the phase diagrams. Moreover, the cross-over features of the parameters from the ferroelectric dominant phase diagram to the paraelectric dominant phase diagram are determined for the ferroelectric nanowire. In addition, the polarizations of the surface shell and the core are illustrated in detail by modifying the TIM parameters.
Rotating cylindrical wormholes: a no-go theorem
Bronnikov, K. A.
2016-02-01
The existing solutions to the Einstein equations describing rotating cylindrical wormholes are not asymptotically flat and therefore cannot describe wormhole entrances as local objects in our Universe. To overcome this difficulty, flat asymptotic regions are added to wormhole solutions by matching them at some surfaces ∑- and ∑+. It is shown, however, that if the wormhole solution is obtained for scalar fields with arbitrary potentials, possibly interacting with an azimuthal electric or magnetic field, then the matter content of one or both thin shells appearing on ∑- and ∑+ violate the Null Energy Condition. Thus exotic matter is still necessary for obtaining a twice asymptotically flat wormhole.
Rotating cylindrical wormholes: a no-go theorem
Bronnikov, K A
2015-01-01
The existing solutions to the Einstein equations describing rotating cylindrical wormholes are not asymptotically flat and therefore cannot describe wormhole entrances as local objects in our Universe. To overcome this difficulty, flat asymptotic regions are added to wormhole solutions by matching them at some surfaces $\\Sigma_-$ and $\\Sigma_+$. It is shown, however, that if the wormhole solution is obtained for scalar fields with arbitrary potentials, possibly interacting with an azimuthal electric or magnetic field, then the matter content of one or both thin shells appearing on $\\Sigma_-$ and $\\Sigma_+$ violate the Null Energy Condition. Thus exotic matter is still necessary for obtaining a twice asymptotically flat wormhole.
The cylindrical \\delta-potential and the Dirac equation
Loewe, M.; Marquez, F.; Zamora, R.
2011-01-01
In this article we discuss the Dirac equation in the presence of an attractive cylindrical \\delta-shell potential V(\\rho)=-a\\delta(\\rho-\\rho_0), where \\rho is the radial coordinate and a>0. We present a detailed discussion on the boundary conditions the wave function has to satisfy when crossing the support of the potential, proceeding then to explore the dependence of the ground state on the parameter a, analyzing the occurrence of supercritical effects. We also apply the Foldy-Wouthuysen tr...
WEIR COEFFICIENT FOR CYLINDRICAL WEIRS
Directory of Open Access Journals (Sweden)
Senayi DÖNMEZ
2002-01-01
Full Text Available In this study, the weir coefficient for cylindrical weirs was experimentally investigated. Experiments were conducted for both free and submerged overflow conditions. Experimental results have indicated that the weir coefficient is about 3.50-3.80 for the free overflow condition. The weir coefficient for the submerged overflow condition varies with the amount of submergence.
Optics Demonstrations Using Cylindrical Lenses
Ivanov, Dragia; Nikolov, Stefan
2015-01-01
In this paper we consider the main properties of cylindrical lenses and propose several demonstrational experiments that can be performed with them. Specifically we use simple glasses full of water to demonstrate some basic geometrical optics principles and phenomena. We also present some less standard experiments that can be performed with such…
Finite-amplitude dynamics of coupled cylindrical menisci.
Cox, B L; Steen, P H
2011-10-01
The cylindrical meniscus is a liquid/gas interface of circular-cap cross-section constrained along its axis and bounded by end-planes. The inviscid motions of coupled cylindrical menisci are studied here. Motions result from the competition between inertia and surface tension forces. Restriction to shapes that are of circular-cap cross-section leads to an ordinary differential equation (ode) model, with the advantage that finite-amplitude stability can be examined. The second-order nonlinear ode model has a Hamiltonian structure, showing dynamical behavior like the Duffing-oscillator. The energy landscape has either a single- or double-welled potential depending on the extent of volume overfill. Total liquid volume is a bifurcation parameter, as in the corresponding problem for coupled spherical-cap droplets. Unlike the spherical-cap problem, however, axial disturbances can also destabilize, depending on overfill. For large volumes, previously known axial stability results are applied to find the limit at which axial symmetry is lost and comparison is made to the Plateau-Rayleigh limit. PMID:21723560
Wiimote Experiments: Circular Motion
Kouh, Minjoon; Holz, Danielle; Kawam, Alae; Lamont, Mary
2013-01-01
The advent of new sensor technologies can provide new ways of exploring fundamental physics. In this paper, we show how a Wiimote, which is a handheld remote controller for the Nintendo Wii video game system with an accelerometer, can be used to study the dynamics of circular motion with a very simple setup such as an old record player or a…
Rotating cylindrical wormholes and energy conditions
Bronnikov, K. A.; Krechet, V. G.
2016-01-01
We seek wormholes among rotating cylindrically symmetric configurations in general relativity. Exact wormhole solutions are presented with such sources of gravity as a massless scalar field, a cosmological constant, and a scalar field with an exponential potential. However, none of these solutions are asymptotically flat, which excludes the existence of wormhole entrances as local objects in our Universe. To overcome this difficulty, we try to build configurations with flat asymptotic regions using the cut-and-paste procedure: on both sides of the throat, a wormhole solution is matched to a properly chosen region of flat space-time at some surfaces Σ- and Σ+. It is shown, however, that if the source of gravity in the throat region is a scalar field with an arbitrary potential, then one or both thin shells appearing on Σ- and Σ+ inevitably violate the null energy condition. Thus, although rotating wormhole solutions are easily found without exotic matter, such matter is still necessary for obtaining asymptotic flatness.
Resonance scattering of canonical elastic shells in absorbing fluid medium
Institute of Scientific and Technical Information of China (English)
ZHUO Linkai; FAN Jun; TANG Weilin
2008-01-01
Resonance scattering of elastic spherical shell and cylindrical shell while the sur-rounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable resul twould be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surround-ing fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little in fluence on the low-frequency resonance scattering induced by the filler inside the shell.
On the definition of cylindrical symmetry
Carot, J.; Senovilla, J. M. M.; Vera, R
1999-01-01
The standard definition of cylindrical symmetry in General Relativity is reviewed. Taking the view that axial symmetry is an essential pre-requisite for cylindrical symmetry, it is argued that the requirement of orthogonal transitivity of the isometry group should be dropped, this leading to a new, more general definition of cylindrical symmetry. Stationarity and staticity in cylindrically symmetric spacetimes are then defined, and these issues are analysed in connection with orthogonal trans...
An asymptotically exact theory of functionally graded piezoelectric shells
Le, Khanh Chau
2016-01-01
An asymptotically exact two-dimensional theory of functionally graded piezoelectric shells is derived by the variational-asymptotic method. The error estimation of the constructed theory is given in the energetic norm. As an application, analytical solution to the problem of forced vibration of a functionally graded piezoceramic cylindrical shell with thickness polarization fully covered by electrodes and excited by a harmonic voltage is found.
Roy, Kenneth I.; Kennedy, Robert G., III; Fields, David E.
2013-02-01
The traditional concept of terraforming assumes ready availability of candidate planets with acceptable qualities: orbiting a star in its "Goldilocks zone", liquid water, enough mass, years longer than days, magnetic field, etc. But even stipulating affordable interstellar travel, we still might never find a good candidate elsewhere. Whatever we found likely would require centuries of heavy terraforming, just as Mars or Venus would here. Our increasing appreciation of the ubiquity of life suggests that any terra nova would already possess it. We would then face the dilemma of introducing alien life forms (us, our microbes) into another living world. Instead, we propose a novel method to create habitable environments for humanity by enclosing airless, sterile, otherwise useless planets, moons, and even large asteroids within engineered shells, which avoids the conundrum. These shells are subject to two opposing internal stresses: compression due to the primary's gravity, and tension from atmospheric pressure contained inside. By careful design, these two cancel each other resulting in zero net shell stress. Beneath the shell an Earth-like environment could be created similar in almost all respects to that of Home, except for gravity, regardless of the distance to the sun or other star. Englobing a small planet, moon, or even a dwarf planet like Ceres, would require astronomical amounts of material (quadrillions of tons) and energy, plus a great deal of time. It would be a quantum leap in difficulty over building Dyson Dots or industrializing our solar system, perhaps comparable to a mission across interstellar space with a living crew within their lifetime. But when accomplished, these constructs would be complete (albeit small) worlds, not merely large habitats. They could be stable across historic timescales, possibly geologic. Each would contain a full, self-sustaining ecology, which might evolve in curious directions over time. This has interesting implications
Quantum Solitons with Cylindrical Symmetry
Chepilko, N.; Kobushkin, A.; Syamtomov, A.
1993-01-01
Soliton solutions with cylindrical symmetry are investigated within the nonlinear $\\sigma $-model disregarding the Skyrme-stabilization term. The solitons are stabilized by quantization of collective breathing mode and collapse in the $\\hbar \\to 0$ limit. It is shown that for such stabilization mechanism the model, apart from solitons with integer topological number $B$, admits the solitons with half-odd $B$. The solitons with integer $B$ have standard spin-isospin classification, while $B={\\...
Laser welding of cylindrical parts
Närhi-Ratkovskaia, Olga
2011-01-01
The purpose of this paper is to conduct the laser welding work of the cylindrical parts, particularly fuel filters, according to the safety instructions. The welding was followed by the additional test for a gas resistance of filters. The topic was commissioned by the company Laserplus Oy, located in Hämeenlinna. The aim of the project on laser welding of filters was to find out optimum parameters for the company’s welding. Optimum parameters include the minimum laser power with optimum ...
Cylindrical Collapse and Gravitational Waves
Herrera, L
2005-01-01
We study the matching conditions for a collapsing anisotropic cylindrical perfect fluid, and we show that its radial pressure is non zero on the surface of the cylinder and proportional to the time dependent part of the field produced by the collapsing fluid. This result resembles the one that arises for the radiation - though non-gravitational - in the spherically symmetric collapsing dissipative fluid, in the diffusion approximation.
Relativistically expanding cylindrical electromagnetic fields
Gourgouliatos, K. N.
2009-01-01
We study relativistically expanding electromagnetic fields of cylindrical geometry. The fields emerge from the side surface of a cylinder and are invariant under translations parallel to the axis of the cylinder. The expansion velocity is in the radial direction and is parametrized by $v=R/(ct)$. We consider force-free magnetic fields by setting the total force the electromagnetic field exerts on the charges and the currents equal to zero. Analytical and semi-analytical separable solutions ar...
Modelling apical constriction in epithelia using elastic shell theory.
Jones, Gareth Wyn; Chapman, S Jonathan
2010-06-01
Apical constriction is one of the fundamental mechanisms by which embryonic tissue is deformed, giving rise to the shape and form of the fully-developed organism. The mechanism involves a contraction of fibres embedded in the apical side of epithelial tissues, leading to an invagination or folding of the cell sheet. In this article the phenomenon is modelled mechanically by describing the epithelial sheet as an elastic shell, which contains a surface representing the continuous mesh formed from the embedded fibres. Allowing this mesh to contract, an enhanced shell theory is developed in which the stiffness and bending tensors of the shell are modified to include the fibres' stiffness, and in which the active effects of the contraction appear as body forces in the shell equilibrium equations. Numerical examples are presented at the end, including the bending of a plate and a cylindrical shell (modelling neurulation) and the invagination of a spherical shell (modelling simple gastrulation). PMID:19859751
WHIPPO. WALTER B.; Rohrkaste, G. R.; Miller, John E.
1989-01-01
Shape gauge and associated computer constitute system measuring deviations of large cylinders from roundness. Shaped and held somewhat like crossbow, measures relative locations of three points on surface of large, round object. By making connected series of measurements around periphery technician using gauge determines deviation of object from perfect circularity. Used to measure straightness, roundness, or complicated shapes of such large geometrical objects as surfaces of aircraft and hulls of ships.
RESEARCH ON THE CYLINDRICAL PARTICULATE FLOWS
Institute of Scientific and Technical Information of China (English)
LIN Jian-zhong
2005-01-01
The study of cylindrical particulate flows has wide industrial applicability and hence received much attention. The purpose of the present paper is to provide a review on the motion of cylindrical particles in shear layer, converging channel and jet flows, the dynamic of cylindrical particles sedimentation in a Newtonian fluid, the characterization of turbulent cylindrical particulate flows, the property of interaction between the particles, the structural feature and rheology of suspensions, the analysis of hydrodynamic instability of cylindrical particle suspensions. Finally, the concluding remarks are given.
Bo, Pengbo
2011-07-01
The most important guiding principle in computational methods for freeform architecture is the balance between cost efficiency on the one hand, and adherence to the design intent on the other. Key issues are the simplicity of supporting and connecting elements as well as repetition of costly parts. This paper proposes so-called circular arc structures as a means to faithfully realize freeform designs without giving up smooth appearance. In contrast to non-smooth meshes with straight edges where geometric complexity is concentrated in the nodes, we stay with smooth surfaces and rather distribute complexity in a uniform way by allowing edges in the shape of circular arcs. We are able to achieve the simplest possible shape of nodes without interfering with known panel optimization algorithms. We study remarkable special cases of circular arc structures which possess simple supporting elements or repetitive edges, we present the first global approximation method for principal patches, and we show an extension to volumetric structures for truly threedimensional designs. © 2011 ACM.
Switchable circular beam deflectors
Shang, Xiaobing; Joshi, Pankaj; Tan, Jin-Yi; De Smet, Jelle; Cuypers, Dieter; Baghdasaryan, Tigran; Vervaeke, Michael; Thienpont, Hugo; De Smet, Herbert
2016-04-01
In this work, we report two types of electrically tunable photonic devices with circularly symmetric polarization independent beam steering performance (beam condensing resp. beam broadening). The devices consist of circular micro grating structures combined with nematic liquid crystal (LC) layers with anti-parallel alignment. A single beam deflector converts a polarized and monochromatic green laser beam (λ =543.5 nm) into a diffraction pattern, with the peak intensity appearing at the third order when 0~{{V}\\text{pp}} is applied and at the zeroth order (no deflection) for voltages above 30~{{V}\\text{pp}} . Depending on the shape of the grating structure (non-inverted or inverted), the deflection is inwards or outwards. Both grating types can be made starting from the same diamond-tooled master mold. A polarized white light beam is symmetrically condensed resp. broadened over 2° in the off state and is passed through unchanged in the on state. By stacking two such devices with mutually orthogonal LC alignment layers, polarization independent switchable circular beam deflectors are realized with a high transmittance (>80%), and with the same beam steering performance as the polarization dependent single devices.
Recollision with circular polarization
Mauger, Francois; Kamor, Adam; Bandrauk, Andre; Chandre, Cristel; Uzer, Turgay
2013-05-01
Since its identification in the 90s, the recollision scenario has revealed to be very helpful in explaining many phenomena in atomic and molecular systems subjected to strong and short laser pulses, and it is now at the core of the strong field physics and attosecond science. For linearly polarized laser fields, the recollision scenario has been able to explain nonsequential double ionization (NSDI), high harmonic generation (HHG) and laser induced diffraction (LIED), just to cite them. The same scenario also predicts the absence of recollision when the field is circularly polarized, therefore leading to the absence of NSDI, HHG or LIED. Recently, the influence of the ellipticity of the laser has drawn an increasing level of interest in the strong field community as it is seen as a way to control the electronic dynamics and, for instance, HHG. Using classical models, the common belief of the absence of recollision with circularly polarized laser fields has been proven wrong. In my talk I will present classical and quantum evidence of the presence of recollision with circular polarization. I will discuss the conditions under which such recollisions happen and what they imply.
Energy Technology Data Exchange (ETDEWEB)
Puckett, A.D.
2000-09-01
The ability to model wave propagation in circular cylindrical bars of finite length numerically or analytically has many applications. In this thesis the capability of an explicit finite element method to model longitudinal waves in cylindrical rods with circular cross-sections is explored. Dispersion curves for the first four modes are compared to the analytical solution to determine the accuracy of various element sizes and time steps. Values for the time step and element size are determined that retain accuracy while minimizing computational time. The modeling parameters are validated by calculating a signal propagated with a broadband input force. Limitations on the applicability are considered along with modeling parameters that should be applicable to more general geometries.
Dynamical analysis of multi-layered anisotropic cylindrical panels under thermal load
International Nuclear Information System (INIS)
The increased use of composite materials in aerospace and mechanical engineering structures is due to their high stiffness and strength-to-weight ratio. Studies involving the thermoelastic behavior of composite plates and shells have received great attention in recent years. Thermoelastic problems of reinforced rectangular panels was investigated by Birman. In this paper the static response of isotropic reinforced panels in non-uniform thermal field is discussed. An exact three-dimensional thermoelasticity solution for a cross-ply cylindrical panel has been obtained by Huang and Tauchert using the power series method. Three-dimensional thermal stress analysis of laminated panels have been studied by Saha and Pabitra. Analytical three-dimensional thermoelasticity solutions are presented for static problems of simply supported sandwich panels and cylindrical shells subjected to mechanical load and temperature gradient with constant intensity at inner or outer surfaces by Scott and Noor. Thermoelasticity solution of multilayer anisotropic shells was studied by Shvets and Flyachok. In this paper , the complete system of basic equations of linear dynamic theory of thermal stresses in multilayer shells is developed with the allowance for transverse anisotropy of the material for each layer. In this paper the governing differential equations of motion in term of displacements for each layer of cylindrical panel are solved by enforcing continuity conditions and using Galerkin finite element method. Refs. 5 (author)
Waves on fluid-loaded shells and their resonance frequency spectrum
DEFF Research Database (Denmark)
Bao, X.L.; Uberall, H.; Raju, P.K.;
2005-01-01
Technical requirements for elastic (metal) cylindrical shells include the knowledge of their natural frequency spectrum. These shells may be empty and fluid-immersed, or fluid-filled in an ambient medium of air, or doubly fluid-loaded inside and out. They may support circumferential waves, or axi...... axial direction if the cylindrical shell is terminated at both ends. In this way, we obtain (circumferential and axial wave) eigenfrequency spectra for water filled aluminum and steel shells, and also for brass shells (axial-wave resonances only).......Technical requirements for elastic (metal) cylindrical shells include the knowledge of their natural frequency spectrum. These shells may be empty and fluid-immersed, or fluid-filled in an ambient medium of air, or doubly fluid-loaded inside and out. They may support circumferential waves, or...... axially propagating waves both in the shell material, and in the fluid loading. Previous results by Bao et al. (J. Acoust. Soc. Am. 105 (1999) 2704) were obtained for the circumferential-wave dispersion curves on doubly loaded aluminum shells; the present study extends this to fluid-filled shells in air...
Confirmation of Cylindrical Perfect Invisibility Cloak Using Fourier-Bessel Analysis
Ruan, Zhichao; Yan, Min; Neff, Curtis W.; Qiu, Min
2007-01-01
A cylindrical wave expansion method is developed to obtain the scattering field for an ideal two-dimensional cylindrical invisibility cloak. A near-ideal model of the invisibility cloak is set up to solve the boundary problem at the inner boundary of the cloak shell. We confirm that a cloak with the ideal material parameters is a perfect invisibility cloak by systematically studying the change of the scattering coefficients from the near-ideal case to the ideal one. However, due to the slow c...
Equation of spin motion in storage rings in a cylindrical coordinate system
Silenko, A. J.
2004-01-01
The exact equation of spin motion in a cylindrical coordinate system with allowance for electric dipole moments of particles has been derived. This equation is convenient for analytical calculations of spin dynamics in circular storage rings when the configuration of main fields is simple enough. The generalized formula for the influence of a vertical betatron oscillation on the angular velocity of spin rotation has been found. This formula agrees with the previously obtained result and conta...
Exploring the cylindrical photo-bending shape in polydomain nematic glass
Xuan, Chen; Huo, Yongzhong
2016-01-01
This paper explores different photo-bending shapes in polydomain nematic glass. The motivation is to explain the phenomenon in experiment [1] under polarized light in which a nematic film curls into an circular arc, like part of a cylindrical surface. Polarized light triggers photo-isomerization and therefore makes liquid crystals (LCs) contract along their directors. We apply the Sachs limit to homogenize the deformation of polydomain LC glass. Photo-strain can be either contraction or expansion through the material. Bending shapes can be anticlastic, bowl-shaped and cylindrical affected by Poisson ratio and illumination intensity. An explanation for the cylindrical bend and ways to observe other shapes are given in a parameter plane.
Investigation of spherical and cylindrical Luneburg lens antennas by the Green's function method
Knyazev, S.; Korotkov, A.; Panchenko, B.; Shabunin, S.
2016-03-01
Luneburg lens antenna radiation fields are calculated with Green's functions of spherical and cylindrical layered structures. Electric field components of spherical and cylindrical Luneburg lenses excited by linear and circular polarized incident field are analysed. Dipole, slot and aperture antennas are described by electric and magnetic extraneous currents. Radiation patterns of cylindrical and spherical Luneburg lens are analysed. Co-polarized and cross-polarized field radiation patterns are shown. The proposed method significantly reduces the computing time for multi-layered lenses in comparison with the most commonly used in antenna design. The first step antenna structure optimization may be performed for a shorter time. The results may be used as the first approximation for Ansys HFSS and other software.
Near-Field Characterization of Radial and Axial Blast Waves From a Cylindrical Explosive Charge
McNesby, Kevin; Homan, Barrie
This paper uses experiment (high speed imaging) and simulation (ALE-3D) to investigate radial and axial blast waves produced by uncased, cylindrical charges of TNT (trinitrotoluene). Recently there has been work reported on predicting secondary blast waves in the explosive mid-field (approximately 1 meter from charge center of mass) for cylindrical charges of RDX (trimethylenetrinitramine)/binder formulations. The work we will present seeks to provide complementary information in the explosive near-field, including the approach to chemical ``freeze out'', for end-detonated, right circular cylinders of TNT. Additionally, this work attempts to retrieve state variables (temperature, pressure, velocities) from high-definition images of the explosive event. Keywords: cylindrical charges, blast, shock waves
Simplified vibration analysis method of shells of revolution using beam model
International Nuclear Information System (INIS)
A simplified vibration analysis method for the shells of revolution using the beam model is now under consideration. In the beam model, the relations between the shear forces and horizontal deformations are used for the calculations of the shear area and the relations between the overturning moments and rotation angles are for those of the inertia moment. The calculations of the vibration characteristics of the cylindrical shell, spherical shell and the cylindrical shell with the spherical cap were conducted to verify the accuracy of the beam model. The natural frequencies and the vibration modes of the proposed method are in good agreement with that of the FEM analysis using the axisymmetrical shell model. The proposed method is easily applicable to the vibration analysis of actual shell structures. (author)
Buckling Characteristics of Cylindrical Pipes
Institute of Scientific and Technical Information of China (English)
Toshiaki Sakurai
2015-01-01
This paper describes the buckling pattern of the body frame by energy absorbed efficiency of crashworthiness related toresearch of the buckling characteristics of aluminum cylindrical pipes with various diameters formed mechanical tools. Experimentswere performed by the quasi-static test without lubrication between specimen and equipment. According to the change in the radiusversus thickness of the specimen, the buckling phenomena are transformed from folding to bellows and the rate of energy absorptionis understood. In crashworthiness, frames are characterized by the folding among three patterns from the absorbed energy efficiencypoint of view and weight reduction. With the development of new types of transport such as electric vehicles, innovated bodystructure should be designed.
Gao, Steven; Zhu, Fuguo
2013-01-01
This book presents a comprehensive insight into the design techniques for different types of CP antenna elements and arrays In this book, the authors address a broad range of topics on circularly polarized (CP) antennas. Firstly, it introduces to the reader basic principles, design techniques and characteristics of various types of CP antennas, such as CP patch antennas, CP helix antennas, quadrifilar helix antennas (QHA), printed quadrifilar helix antennas (PQHA), spiral antenna, CP slot antennas, CP dielectric resonator antennas, loop antennas, crossed dipoles, monopoles and CP horns. Adva
International Nuclear Information System (INIS)
Tube-in-shell heat exchangers normally comprise a bundle of parallel tubes within a shell container, with a fluid arranged to flow through the tubes in heat exchange with a second fluid flowing through the shell. The tubes are usually end supported by the tube plates that separate the two fluids, and in use the tube attachments to the tube plates and the tube plates can be subject to severe stress by thermal shock and frequent inspection and servicing are required. Where the heat exchangers are immersed in a coolant such as liquid Na such inspection is difficult. In the arrangement described a longitudinally extending central tube is provided incorporating axially spaced cylindrical tube plates to which the opposite ends of the tubes are attached. Within this tube there is a tubular baffle that slidably seals against the wall of the tube between the cylindrical tube plates to define two co-axial flow ducts. These ducts are interconnected at the closed end of the tube by the heat exchange tubes and the baffle comprises inner and outer spaced walls with the interspace containing Ar. The baffle is easily removable and can be withdrawn to enable insertion of equipment for inspecting the wall of the tube and tube attachments and to facilitate plugging of defective tubes. Cylindrical tube plates are believed to be superior for carrying pressure loads and resisting the effects of thermal shock. Some protection against thermal shock can be effected by arranging that the secondary heat exchange fluid is on the tube side, and by providing a thermal baffle to prevent direct impingement of hot primary fluid on to the cylindrical tube plates. The inner wall of the tubular baffle may have flexible expansible region. Some nuclear reactor constructions incorporating such an arrangement are described, including liquid metal reactors. (U.K.)
A probabilistic method for the buckling assessment of stiffened composite shells
Shiao, Michael C.; Abumeri, Galib H.; Singhal, Surendra N.; Chamis, Christos C.
1993-01-01
A method is described to computationally simulate probabilistic buckling behavior of multilayered composite shells. The simulation accounts for all naturally-occurring uncertainties including those in constituent (fiber/matrix) material properties, fabrication variables, and structure geometry. The method is demonstrated for probabilistically assessing the buckling survivability of a specific case of a stiffened composite cylindrical shell with and without cutouts. The sensitivities of various uncertain variables on the buckling survivability are evaluated at specified reliability. The results show that the buckling survivability for a shell without cutouts depends primarily on shell skin related uncertainties. However, stringer related uncertainties become important for a shell with cutouts.
Traveling circumferential unstable wave of cylindrical flame front
Trilis, A. V.; Vasiliev, A. A.; Sukhinin, S. V.
2016-06-01
The researches of stability of cylindrical front of deflagration combustion in an annular combustion chamber were made using phenomenological model. The flame front is described as discontinuity of gasdynamic parameters. It is considered that the combustion products are under chemical equilibrium. The combustible mixture and the combustion products are ideal gases. The velocity of deflagration combustion is determined using the Chapman-Jouget theory. It depends on the temperature of combustible mixture only. It is found that the combustible flame front is unstable for several types of small disturbances in the system Mechanics of instabilities are examined using both the numeric and analytical methods. The cases of evolution of the unstable waves rotating in circular channel are presented.
Circumferential buckling instability of a growing cylindrical tube
Moulton, D.E.
2011-03-01
A cylindrical elastic tube under uniform radial external pressure will buckle circumferentially to a non-circular cross-section at a critical pressure. The buckling represents an instability of the inner or outer edge of the tube. This is a common phenomenon in biological tissues, where it is referred to as mucosal folding. Here, we investigate this buckling instability in a growing elastic tube. A change in thickness due to growth can have a dramatic impact on circumferential buckling, both in the critical pressure and the buckling pattern. We consider both single- and bi-layer tubes and multiple boundary conditions. We highlight the competition between geometric effects, i.e. the change in tube dimensions, and mechanical effects, i.e. the effect of residual stress, due to differential growth. This competition can lead to non-intuitive results, such as a tube growing to be thinner and yet buckle at a higher pressure. © 2011 Elsevier Ltd. All rights reserved.
Antimicrobial Peptides in Toroidal and Cylindrical Pores
Mihajlovic, Maja; Lazaridis, Themis
2010-01-01
Antimicrobial peptides (AMPs) are small, usually cationic peptides, which permeabilize biological membranes. Their mechanism of action is still not well understood. Here we investigate the preference of alamethicin and melittin for pores of different shapes, using molecular dynamics (MD) simulations of the peptides in pre-formed toroidal and cylindrical pores. When an alamethicin hexamer is initially embedded in a cylindrical pore, at the end of the simulation the pore remains cylindrical or ...
Cylindrical Superlens by a Coordinate Transformation
Yan, Min; Yan, Wei; Qiu, Min
2008-01-01
Cylinder-shaped perfect lens deduced from the coordinate transformation method is proposed. The previously reported perfect slab lens is noticed to be a limiting form of the cylindrical lens when the inner radius approaches infinity with respect to the lens thickness. Connaturality between a cylindrical lens and a slab lens is affirmed by comparing their eigenfield transfer functions. We numerically confirm the subwavelength focusing capability of such a cylindrical lens with consideration of...
Computing Cylindrical Algebraic Decomposition via Triangular Decomposition
Chen, Changbo; Maza, Marc Moreno; Xia, Bican; Yang, Lu
2009-01-01
Cylindrical algebraic decomposition is one of the most important tools for computing with semi-algebraic sets, while triangular decomposition is among the most important approaches for manipulating constructible sets. In this paper, for an arbitrary finite set $F \\subset {\\R}[y_1, ..., y_n]$ we apply comprehensive triangular decomposition in order to obtain an $F$-invariant cylindrical decomposition of the $n$-dimensional complex space, from which we extract an $F$-invariant cylindrical algeb...
Impact of the Excitation Source and Plasmonic Material on Cylindrical Active Coated Nano-Particles
Directory of Open Access Journals (Sweden)
Richard W. Ziolkowski
2011-09-01
Full Text Available Electromagnetic properties of cylindrical active coated nano-particles comprised of a silica nano-cylinder core layered with a plasmonic concentric nano-shell are investigated for potential nano-sensor applications. Particular attention is devoted to the near-field properties of these particles, as well as to their far-field radiation characteristics, in the presence of an electric or a magnetic line source. A constant frequency canonical gain model is used to account for the gain introduced in the dielectric part of the nano-particle, whereas three different plasmonic materials (silver, gold, and copper are employed and compared for the nano-shell layers.
Pi, Archimedes and circular splines
Sablonnière, Paul
2013-01-01
In the present paper, we give approximate values of $\\pi$ deduced from the areas of inscribed and circumscribed quadratic and cubic circular splines. Similar results on circular splines of higher degrees and higher approximation orders can be obtained in the same way. We compare these values to those obtained by computing the {\\em perimeters} of those circular splines. We observe that the former are much easier to compute than the latter and give results of the same order. It also appears tha...
A reinforcement design method based on analysis of large openings in cylindrical pressure vessels
International Nuclear Information System (INIS)
The analytical solution is given for two orthogonally intersecting cylindrical shells with large diameter ratio d/D subjected to internal pressure. The modified Morley equation is used for the shell with cutout and the Love equation for the tube with nonplanar end. The continuity conditions of forces and displacements at the intersection are expressed in 3-D cylindrical coordinates (ρ, θ, z), and are expanded in Fourier series of θ. The Fourier coefficients are obtained by numerical quadrature. The present results are in good agreement with those obtained by tests and by FEM for ρ0 = d/D ≤ 0.8. The typical curves of SCF versus t/T and d/√(DT) and reinforcement coefficients g, h versus D/T0 for each ρ0 are given on the present method
Propagation Mechanism of Cylindrical Cellular Detonation
Han, Wen-Hu; Wang, Cheng; Ning, Jian-Guo
2012-10-01
We investigate the evolution of cylindrical cellular detonation with different instabilities. The numerical results show that with decreasing initial temperature, detonation becomes more unstable and the cells of the cylindrical detonation tend to be irregular. For stable detonation, a divergence of cylindrical detonation cells is formed eventually due to detonation instability resulting from a curved detonation front. For mildly unstable detonation, local overdriven detonation occurs. The detonation cell diverges and its size decreases. For highly unstable detonation, locally driven detonation is more obvious and the front is highly wrinkled. As a result, the diverging cylindrical detonation cell becomes highly irregular.
International Nuclear Information System (INIS)
In this study, the buckling analysis of the simply supported truncated conical shell made of functionally graded materials (FGMs) is presented. The FGM truncated conical shell subjected to an axial compressive load and resting on Winkler-Pasternak type elastic foundations. The material properties of functionally graded shells are assumed to vary continuously through the thickness. The modified Donnell type stability and compatibility equations are solved by Galerkin's method and the critical axial load of FGM truncated conical shells with and without elastic foundations have been found analytically. The appropriate formulas for homogenous and FGM cylindrical shells with and without elastic foundations are found as a special case. Several examples are presented to show the accuracy and efficiency of the formulation. Finally, parametric studies on the buckling of FGM truncated conical and cylindrical shells on elastic foundations are being investigated. These parameters include; power-law and exponential distributions of FGM, Winkler foundation modulus, Pasternak foundation modulus and aspect ratios of shells.
A robust shell element in meshfree SPH method
Institute of Scientific and Technical Information of China (English)
Fu-Ren Ming; A-Man Zhang; Xue-Yan Cao
2013-01-01
With the incorporation of total Lagrangian smoothed particle hydrodynamics (SPH) method equation and moving least square (MLS) function,the traditional SPH method is improved regarding the stability and consistency.Based on Mindlin-Ressiner plate theory,the SPH method simulating dynamic behavior via one layer of particles is applied to plate's mid-plane,i.e.,a SPH shell model is constructed.Finally,through comparative analyses on the dynamic response of square,stiffened shells and cylindrical shells under various strong impact loads with common finite element software,the feasibility,validity and numerical accuracy of the SPH shell method are verified.Consequently,further researches on SPH shell may well pave the way towards solving problems involving dynamic plastic damage,tearing or even crushing.
Low-Q whispering gallery modes in anisotropic metamaterial shells
Díaz-Rubio, Ana; Torrent, Daniel; Sánchez-Dehesa, José
2013-01-01
Anisotropic and inhomogeneous metamaterial shells are studied in order to exploit all their resonant mode richness. These multilayer structures are based on a cylindrical distribution of radially dependent constitutive parameters including an inner void cavity. Shell, cavity and whispering gallery modes are characterized, and special attention is paid to the latter ones. The whispering gallery modes are created at the boundary layers of the shell with the background and energy localization is produced with highly radiative characteristics. These low-Q resonant states have frequencies that are independent of the shell thickness. However, their quality factors can be controlled by the number of layers forming the shell, which allows confining electromagnetic waves at the interface layers (internal or external), and make them suitable for the harvesting of electromagnetic energy.
Impact of the Excitation Source and Plasmonic Material on Cylindrical Active Coated Nano-Particles
Ziolkowski, Richard W.; Radu Malureanu; Samel Arslanagic; Yan Liu
2011-01-01
Electromagnetic properties of cylindrical active coated nano-particles comprised of a silica nano-cylinder core layered with a plasmonic concentric nano-shell are investigated for potential nano-sensor applications. Particular attention is devoted to the near-field properties of these particles, as well as to their far-field radiation characteristics, in the presence of an electric or a magnetic line source. A constant frequency canonical gain model is used to account for the gain introduced ...
Circular PVDF Airborne Transducer
Institute of Scientific and Technical Information of China (English)
JIAO Li-hua; XU Li-mei; HONG Hu
2007-01-01
With the required increased audio pressure of the parametric ultrasonic transducer array and the difficulty to theoretically analyse the complex ultrasonic structure in audio beam application, an computafionally efficient model is desired to describe the characteristic of the parametric ultrasonic transducer array for the system design and optimization. By applying the symmetry boundary conditions at the mid-plane in the thickness direction, a finite element model based on the half thickness simplification is presented to analyze the parametric circular transducer which is designed by gluing the poly Vinylidene fluoride film (PVDF). The validity of the proposed model is confirmed by a comparison of finite element aalysis results with the theoretical value and experimental data, which show that they are making a good agreement with each other.
Coupled dilaton and electromagnetic field in cylindrically symmetric spacetime
Indian Academy of Sciences (India)
A Banerjee; S Chatterjee; Tanwi Ghosh
2000-03-01
An exact solution is obtained for coupled dilaton and electromagnetic ﬁeld in a cylindrically symmetric spacetime where an axial magnetic ﬁeld as well as a radial electric ﬁeld both are present. Depending on the choice of the arbitrary constants our solution reduces either to dilatonic gravity with pure electric ﬁeld or to that with pure magnetic ﬁeld. In the ﬁrst case we have a curvature singularity at a ﬁnite distance from the axis indicating the existence of the boundary of a charged cylinder which may represent the source of the electric ﬁeld. For the second case we have a singularity on the axis. When the dilaton ﬁeld is absent the electromagnetic ﬁeld disappears in both the cases. Whereas the contrary is not true. It is further shown that light rays except for those proceeding in the radial direction are either trapped or escape to inﬁnity depending on the magnitudes of certain constant parameters as well as on the nature of the electromagnetic ﬁeld. Nature of circular geodesics is also studied in the presence of dilaton ﬁeld in the cylindrically symmetric spacetime.
Operational circular No. 1 (Rev. 1) – Operational circulars
HR Department
2011-01-01
Operational Circular No. 1 (Rev. 1) is applicable to members of the personnel and other persons concerned. Operational Circular No. 1 (Rev. 1) entitled "Operational circulars", approved following discussion at the Standing Concertation Committee meeting on 4 May 2011, is available on the intranet site of the Human Resources Department: https://hr-docs.web.cern.ch/hr-docs/opcirc/opcirc.asp It cancels and replaces Operational Circular No. 1 entitled "Operational Circulars” of December 1996. This new version clarifies, in particular, that operational circulars do not necessarily arise from the Staff Rules and Regulations, and the functional titles have been updated to bring them into line with the current CERN organigram. Department Head Office
Diffusion from cylindrical waste forms
International Nuclear Information System (INIS)
The diffusion of a single component material from a finite cylindrical waste form, initially containing a uniform concentration of the material, is investigated. Under the condition that the cylinder is maintained in a well-stirred bath, expressions for the fractional inventory leached and the leach rate are derived with allowance for the possible permanent immobilization of the diffusant through its decay to a stable product and/or its irreversible reaction with the waste form matrix. The usefulness of the reported results in nuclear waste disposal applications is emphasized. The results reported herein are related to those previously derived at Oak Ridge National Laboratory by Bell and Nestor. A numerical scheme involving the partial decoupling of nested infinite summations and the use of rapidly converging rational approximants is recommended for the efficient implementation of the expressions derived to obtain reliable estimates of the bulk diffusion constant and the rate constant describing the diffusant-waste form interaction from laboratory data
Implementing circularity using partial evaluation
DEFF Research Database (Denmark)
Lawall, Julia Laetitia
2001-01-01
Complex data dependencies can often be expressed concisely by defining a variable in terms of part of its own value. Such a circular reference can be naturally expressed in a lazy functional language or in an attribute grammar. In this paper, we consider circular references in the context of an...
Observations of ion-acoustic cylindrical solitons
Hershkowitz, N.; Romesser, T.
1974-01-01
Experimental observations of cylindrical solitons in a collisionless plasma are presented. The data obtained show that cylindrical solitonlike objects exist and that their properties are consistent with those of one- and three-dimensional solitons. It is found that compressive density perturbations evolve into solitons. The number of the solitons is determined by the width and amplitude of the applied pulse.
Magnetic guns with cylindrical permanent magnets
DEFF Research Database (Denmark)
Vokoun, David; Beleggia, Marco; Heller, Luděk
2012-01-01
The motion of a cylindrical permanent magnet (projectile) inside a tubular permanent magnet, with both magnets magnetized axially, illustrates nicely the physical principles behind the operation of magnetic guns. The force acting upon the projectile is expressed semi-analytically as derivative of...... the generated forces and motion of the inner cylindrical magnet....
Brans-Dicke cylindrical wormholes
International Nuclear Information System (INIS)
Static axisymmetric thin-shell wormholes are constructed within the framework of the Brans-Dicke scalar-tensor theory of gravity. Examples of wormholes associated with vacuum and electromagnetic fields are studied. All constructions must be threaded by exotic matter, except in the case of geometries with a singularity of finite radius, associated with an electric field, which can have a throat supported by ordinary matter. These results are achieved with any of the two definitions of the flare-out condition considered.
Circular chemiresistors for microchemical sensors
Ho, Clifford K.
2007-03-13
A circular chemiresistor for use in microchemical sensors. A pair of electrodes is fabricated on an electrically insulating substrate. The pattern of electrodes is arranged in a circle-filling geometry, such as a concentric, dual-track spiral design, or a circular interdigitated design. A drop of a chemically sensitive polymer (i.e., chemiresistive ink) is deposited on the insulating substrate on the electrodes, which spreads out into a thin, circular disk contacting the pair of electrodes. This circularly-shaped electrode geometry maximizes the contact area between the pair of electrodes and the polymer deposit, which provides a lower and more stable baseline resistance than with linear-trace designs. The circularly-shaped electrode pattern also serves to minimize batch-to-batch variations in the baseline resistance due to non-uniform distributions of conductive particles in the chemiresistive polymer film.
Shell galaxies: kinematical signature of shells, satellite galaxy disruption and dynamical friction
Ebrova, Ivana
2013-01-01
Stellar shells observed in many giant elliptical and lenticular as well as a few spiral and dwarf galaxies presumably result from radial minor mergers of galaxies. We show that the line-of-sight velocity distribution of the shells has a quadruple-peaked shape. We found simple analytical expressions that connect the positions of the four peaks of the line profile with the mass distribution of the galaxy, namely, the circular velocity at the given shell radius and the propagation velocity of the shell. The analytical expressions were applied to a test-particle simulation of a radial minor merger, and the potential of the simulated host galaxy was successfully recovered. Shell kinematics can thus become an independent tool to determine the content and distribution of dark matter in shell galaxies up to ~100 kpc from the center of the host galaxy. Moreover we investigate the dynamical friction and gradual disruption of the cannibalized galaxy during the shell formation in the framework of a simulation with test p...
Electromagnetic response of buried cylindrical structures for line current excitation
Pajewski, Lara; Ponti, Cristina
2013-04-01
The Cylindrical-Wave Approach (CWA) rigorously solves, in the spectral domain, the electromagnetic forward scattering by a finite set of buried two-dimensional perfectly-conducting or dielectric objects [1]-[2]. In this technique, the field scattered by underground objects is represented in terms of a superposition of cylindrical waves. Use is made of the plane-wave spectrum [1] to take into account the interaction of such waves with the planar interface between air and soil, and between different layers eventually present in the ground [3]. Obstacles of general shape can be simulated through the CWA with good results, by using a suitable set of small circular-section cylinders [4]. Recently, we improved the CWA by facing the fundamental problem of losses in the ground [5]: this is of significant importance in remote-sensing applications, since real soils often have complex permittivity and conductivity, and sometimes also a complex permeability. While in previous works concerning the CWA a monochromatic or pulsed plane-wave incident field was considered, in the present work a different source of scattering is present: a cylindrical wave radiated by a line source. Such a source is more suitable to model the practical illumination field used in GPR surveys. The electric field radiated by the line current is expressed by means of a first-kind Hankel function of 0-th order. The theoretical solution to the scattering problem is developed for both dielectric and perfectly-conducting cylinders buried in a dielectric half-space. The approach is implemented in a Fortran code; an accurate numerical evaluation of the involved spectral integrals is performed, the highly-oscillating behavior of the homogeneous waves is correctly followed and evanescent contributions are taken into account. The electromagnetic field scattered in both air and ground can be obtained, in near- and far-field regions, for arbitrary radii and permittivity of the buried cylinders, as well as for
An Analytical Solution for Cylindrical Concrete Tank on Deformable Soil
Directory of Open Access Journals (Sweden)
Shirish Vichare
2010-07-01
Full Text Available Cylindrical concrete tanks are commonly used in wastewater treatment plants. These are usually clarifier tanks. Design codes of practice provide methods to calculate design forces in the wall and raft of such tanks. These methods neglect self-weight of tank material and assume extreme, namely ‘fixed’ and ‘hinged’ conditions for the wall bottom. However, when founded on deformable soil, the actual condition at the wall bottom is neither fixed nor hinged. Further, the self-weight of the tank wall does affect the design forces. Thus, it is required to offer better insight of the combined effect of deformable soil and bottom raft stiffness on the design forces induced in such cylindrical concrete tanks. A systematic analytical method based on fundamental equations of shells is presented in this paper. Important observations on variation of design forces across the wall and the raft with different soil conditions are given. Set of commonly used tanks, are analysed using equations developed in the paper and are appended at the end.
Feasibility of Pulverized Oyster Shell as a Cementing Material
Directory of Open Access Journals (Sweden)
Chou-Fu Liang
2013-01-01
Full Text Available This research intends to study the cementing potential of pulverized oyster shell, rich in calcium, when mixed with fly ash and soil. Cylindrical compacted soil and cubic lime specimens with different proportions of the shells and fly ash are made to study the strength variance. Soil, which is classified as CL in the USCS system, commercialized pulverized oyster shell, F-type fly ash, and lime are mixed in different weight percentages. Five sample groups are made to study the compressive strength of soil and lime specimens, respectively. The lime cubes are made with 0.45 W/B ratio and the cylindrical soils are compacted under the standard Procter compaction process with 20% moisture content. The results show that increment of shell quantity result to lower strength on both the soil and lime specimens. In a 56-day curing, the compressive strength of the lime cubes containing fly ash increases evidently while those carrying the shell get little progress in strength. The soil specimens containing fly ash gradually gain strength as curing proceeds. It suggests that mixtures of the shell and fly ash do not process any Pozzolanic reaction nor help to raise the unconfined strength of the compacted soil through the curing.
International Nuclear Information System (INIS)
During the irradiation tests of materials, all the components of a cylindrical structure with multiple specimens act like heat sources due to a high gamma flux. The thermal stress is induced by a temperature difference among the heat sources. In this study, the thermal stress of a cylindrical structure is minimized by using an optimization method regarding the geometric variables. The rectangular and circular shapes of the multi-specimens are investigated. For the thermal analysis of the structure, the finite element method code, ANSYS 8.1 is used. A sub-problem approximation method is used for the structural design optimization. (author)
AUTHOR|(CDS)2108454; Zimmermann, Frank
2015-01-01
In response to a request from the 2013 Update of the European Strategy for Particle Physics, the global Future Circular Collider (FCC) study is preparing the foundation for a next-generation large-scale accelerator infrastructure in the heart of Europe. The FCC study focuses on the design of a 100-TeV hadron collider (FCC-hh), to be accommodated in a new ∼100 km tunnel near Geneva. It also includes the design of a high-luminosity electron-positron collider (FCC-ee), which could be installed in the same tunnel as a potential intermediate step, and a lepton-hadron collider option (FCC-he). The scope of the FCC study comprises accelerators, technology, infrastructure, detectors, physics, concepts for worldwide data services, international governance models, and implementation scenarios. Among the FCC core technologies figure 16-T dipole magnets, based on Nb3Sn superconductor, for the FCC-hh hadron collider, and a highly efficient superconducting radiofrequency system for the FCC-ee lepton collider. The interna...
AUTHOR|(CDS)2108454; Zimmermann, Frank
2015-01-01
In response to a request from the 2013 Update of the European Strategy for Particle Physics, the global Future Circular Collider (FCC) study is preparing the foundation for a next-generation large-scale accelerator infrastructure in the heart of Europe. The FCC study focuses on the design of a 100-TeV hadron collider (FCC-hh), to be accommodated in a new ∼100 km tunnel near Geneva. It also includes the design of a high-luminosity electron-positron collider (FCC-ee), which could be installed in the same tunnel as a potential intermediate step, and a lepton-hadron collider option (FCC-he). The scope of the FCC study comprises accelerators, technology, infrastructure, detector, physics, concepts for worldwide data services, international governance models, and implementation scenarios. Among the FCC core technologies figure 16-T dipole magnets, based on Nb3Sn superconductor, for the FCC-hh hadron collider, and a highly efficient superconducting radiofrequency system for the FCC-ee lepton collider. The internat...
Towards Future Circular Colliders
AUTHOR|(CDS)2108454; Zimmermann, Frank
2015-01-01
The Large Hadron Collider (LHC) at CERN presently provides proton-proton collisions at a centre-of-mass (c.m.) energy of 13 TeV. The LHC design was started more than 30 years ago, and its physics programme will extend through the second half of the 2030’s. The global Future Circular Collider (FCC) study is now preparing for a post-LHC project. The FCC study focuses on the design of a 100-TeV hadron collider (FCC-hh) in a new ∼100 km tunnel. It also includes the design of a high-luminosity electron-positron collider (FCC-ee) as a potential intermediate step, and a lepton-hadron collider option (FCC-he). The scope of the FCC study comprises accelerators, technology, infrastructure, detectors, physics, concepts for worldwide data services, international governance models, and implementation scenarios. Among the FCC core technologies figure 16-T dipole magnets, based on $Nb_3Sn$ superconductor, for the FCC-hh hadron collider, and a highly efficient superconducting radiofrequency system for the FCC-ee lepton c...
Investigation of Buckling Behavior of Composite Shell Structures with Cutouts
Arbelo, Mariano A.; Herrmann, Annemarie; Castro, Saullo G. P.; Khakimova, Regina; Zimmermann, Rolf; Degenhardt, Richard
2015-12-01
Thin-walled cylindrical composite shell structures can be applied in space applications, looking for lighter and cheaper launcher transport system. These structures are prone to buckling under axial compression and may exhibit sensitivity to geometrical imperfections. Today the design of such structures is based on NASA guidelines from the 1960's using a conservative lower bound curve generated from a database of experimental results. In this guideline the structural behavior of composite materials may not be appropriately considered since the imperfection sensitivity and the buckling load of shells made of such materials depend on the lay-up design. It is clear that with the evolution of the composite materials and fabrication processes this guideline must be updated and / or new design guidelines investigated. This need becomes even more relevant when cutouts are introduced to the structure, which are commonly necessary to account for access points and to provide clearance and attachment points for hydraulic and electric systems. Therefore, it is necessary to understand how a cutout with different dimensions affects the buckling load of a thin-walled cylindrical shell structure in combination with other initial geometric imperfections. In this context, this paper present some observations regarding the buckling load behavior vs. cutout size and radius over thickness ratio, of laminated composite curved panels and cylindrical shells, that could be applied in further recommendations, to allow identifying when the buckling of the structure is dominated by the presence of the cutout or by other initial imperfections.
Self-regulating characteristics of cold neutron source with annular cylindrical moderator cell
International Nuclear Information System (INIS)
The conditions, in which the ORPHEE type cold neutron source with an annular cylindrical moderator cell could have self-regulating characteristics, were obtained through thermodynamic considerations. From a viewpoint of engineering, it is not easy to establish these conditions because three parameters are involved even in an idealized system without the effect of the mass transfer resistance in the moderator transfer tube between the condenser and the moderator cell. The inner shell of the ORPHEE moderator cell is open in the bottom, but it is expected that only hydrogen vapor is contained in the inner shell and liquid hydrogen in the outer shell. The thermodynamic considerations show that such a state is maintained only when a liquefaction capacity of the condenser is large compared to heat lead and three parameters are optimized with a good balance. We proposed another type of a moderator cell, which has an inner cylindrical cavity with no hole in the bottom but a vapor inlet opening at the uppermost part of the cavity. In this structure, a self-regulating characteristic is established easily and the liquid level in the outer shell is maintained almost constant against thermal disturbances. Therefore it is enough to control one parameter, that is, the reservoir tank pressure corresponding to the liquefaction capacity of the condenser given by the refrigeration power of the helium refrigerator. (author)
Passive jet control of flow around a circular cylinder
Chen, Wen-Li; Gao, Dong-Lai; Yuan, Wen-Yong; Li, Hui; Hu, Hui
2015-11-01
In the present study, a passive flow control method, which is featured by passive windward suction combined with leeward jet over a circular cylinder for drag reduction and dynamic wind loading suppression, was experimentally investigated to manipulate unsteady wake vortex shedding from a circular cylinder. Four perforated pipe designs with different numbers of suction/jet holes (i.e., from 2 to 24 suction/jet holes) were used to create flow communicating channels between the windward and leeward stagnation points of a cylindrical test model. The experimental study was performed in a wind tunnel at a Reynolds number of Re = 4.16 × 104 based on the cylinder diameter and oncoming airflow speed. In addition to measuring surface pressure distributions to determine the dynamic wind loads acting on the test model, a digital particle image velocimetry (PIV) system was also used to quantify the wake flow characteristics in order to assess the effectiveness of the passive jet control method with different perforated pipe designs, in comparison with a baseline case without passive jet control. It was found that the passive jet control method is very effective in manipulating the wake vortex shedding process from the circular cylinder. The perforated pipe designs with more suction/jet holes were found to be more effective in reducing drag and suppressing fluctuating amplitude of the dynamic wind loads acting on the test model. With 24 suction/jet holes evenly distributed over the cylindrical test model (i.e., the N13 design of the present study), the passive jet control method was found to be able to achieve up to 33.7 % in drag reduction and 90.6 % in fluctuating wind loading suppression, in comparison with the baseline case. The PIV measurement results revealed clearly that the passive jet control method would cause airflow jets into the cylinder wake and change the shedding modes of the wake vortex structures from the cylindrical test model. Because of the dynamic
Strength of protective ferroconcrete shells with an internal explosive load
International Nuclear Information System (INIS)
Ferroconcrete cylindrical containment vessels of height equal to the diameter with an elliptical lid are most widely used at Russian atomic power stations. They are designed to withstand the action of internal static pressure. Although the action of explosive internal loads on their internal surface is possible in an accident, no experimental studies of this situation are known. As a first approximation, the integral characteristic K = M/mex used to estimate the permissible explosive load of ferroconcrete explosion chambers was suggested as a first approximation in estimating the dynamic strength of shells under an explosive load; here M is the mass of the shell and mex is the mass of the explosive charge. Practical experience with explosion chambers indicates that they remain intact under multiple explosions if K ≥ 103. In their work, the failure of cylindrical ferroconcrete shells (rings) under an internal explosive load is experimentally studied, and the results are used to predict the explosion stability of the containment vessels of atomic power plants. In the pressure-momentum plane of the load, there are regions corresponding to damage to the ring at three levels: the presence of partial and through cracks and failure of the reinforcement. The boundaries of the regions (isodamage curves) are the geometric loci of all possible combinations of load parameters corresponding to the same final state of the ring on the chosen scale. A procedure has been described for plotting isodamage curves for thin rings of arbitrary radius on the basis of the experimental results. By plotting such curves for the example of a hypothetical cylindrical shell close in size to the cylindrical section of the containment vessel at the fifth unit of the Novo-Voronezh atomic power plant (Ro = 23 m, H = 40 m, σ = 1.2 m), it has been shown that this shell remains intact under the explosion of a TNT charge of mass up to 3.5 ton
Aluminium Alloy Cast Shell Development for Torpedoes
Directory of Open Access Journals (Sweden)
Vijaya Singh
2005-01-01
Full Text Available The sand-cast aluminium alloy cylindrical shells were developed for the advanced experimental torpedo applications. The components had intricate geometry, thin-walled sections, and stringent property requirements. The casting defects, such as shrinkage, porosity, incomplete filling of thin sections, cold shuts, inclusions and dimensional eccentricity, etc were found inthe initial castings trials. improvements in casting quality were achieved through modified methodology, selective chilling, risering, and by introducing ceramic-foam filters in the gatingsystem. The heat-treated and machined components met radiographic class I grade C/E standards, mechanical properties to BS1490 specifications, and leakage and hydraulic pressure testrequirements relevant for such applications.
A circular aperture array for ultrasonic tomography and quantitative NDE
Energy Technology Data Exchange (ETDEWEB)
Nielsen, S.A.
1998-08-01
The main topics of this thesis are ultrasonic tomography and ultrasonic determination of elastic stiffness constants. Both issues are based on a synthetic array with transducer elements distributed uniformly along a circular aperture, i.e., a circular aperture array. The issues are treated both theoretically and experimentally by broadband pulse techniques. Ultrasonic tomography, UCT, from a circular aperture is a relatively new imaging technique in Non-destructive Evaluation (NDE) to acquire cross sectional images in bulk materials. A filtered back-projection algorithm is used to reconstruct images in four different experiments and results of attenuation, velocity and reflection tomograms in Plexiglas of AlSi-alloy cylinders are presented. Two kinds of ultrasonic tomography are introduced: bistatic and monostatic imaging. Both techniques are verified experimentally by Plexiglas cylinders. Different reconstruction artifacts are discussed and theoretical resolution constraints are discussed for various configurations of the circular aperture array. The monostatic technique is used in volumetric imaging. In the experimental verification artificial and real discontinuities in a cylindrical AlSi-alloy are compared with similar discontinuities in a Plexiglas specimen. Finally, some limitations to UCT are discussed. The circular aperture array is used to determine five independent elastic stiffness constants of a unidirectional glass/PET (Poly Ethylene Teraphtalate) laminate. Energy flux propagation and attenuation of ultrasonic waves are considered and velocity surfaces are calculated for different planes of interest. Relations between elastic stiffness constants and engineering constants (i.e., Young`s moduli, shear moduli and Poisson`s ratios) are discussed for an orthotropic composite. Six micromechanical theories are reviewed, and expressions predicting the elastic engineering constants are evaluated. The micromechanical predicted elastic stiffness constants for the
International Nuclear Information System (INIS)
An analytical procedure has been developed to solve two-group transport problems in cylindrical and spherical one-dimensional finite geometries. Both first and second order transform procedures are utilized to reduce the two-group integral transport equation to a form which can be solved using the method of singular eigenfunction expansion. The applications to specific examples include the spherical shell-source problem, the cylindrical critical problem and the cylindrical shell-source problem. In order to explore a more universal procedure of dealing with convex geometries, a second-order transform technique is discussed diversely. With application to both sperhical and cylindrical geometries, this procedure is demonstrated to be equivalent to the more specialized first-order transform procedure applicable only to spherical problems. A numerical algorithm for the spherical shell-source problem is incorporated in a computer code, TWOSS. The total neutron densities, angular flux, net current and macroscopic neutron balance can be obtained from this computation. The accuracy of TWOSS is investigated by a comparison of the total flux with the values obtained using a discrete ordinates code ANISN. Agreement was achieved to within the numerical accuracy of the model. Also the advantage of TWOSS over a discrete ordinates calculation is demonstrated since the contribution to the density from the discrete and continuous eigenfunctions is shown separately. Since the discrete solution closely approximates the diffusion theory, the errors incurred near the sources and boundaries in using the diffusion approximation are readily quantified
Rational Roll Forming Visco-Plastic of Shells at Act of Loadings of Explosive Type
Directory of Open Access Journals (Sweden)
Nemirovskii Yu.V.
2007-03-01
Full Text Available The problem a visco-plastic dynamic straining of isotropic shells is formulated. The method of a numerical in-tegration of the put initial-bending problem is developed. Efficiency of this method is shown on calculations of non-elastic dynamics of cylindrical shells of a constant and variable thickness. It is shown, that due to a rational roll forming of short shells the maximum magnitude of their residual bending flexures can be reduced in some times, and long shells of constant thickness are close to rational designs.
Double-negative acoustic metamaterials based on quasi-two-dimensional fluid-like shells
Gracia Salgado, Rogelio; Torrent Martí, Daniel; Sánchez-Dehesa Moreno-Cid, José
2012-01-01
A structured cylindrical scatterer with low-frequency resonances in both the effective bulk modulus and the dynamical mass density is designed and characterized. The proposed scattering unit is made of a rigid cylinder surrounded by a fluid-like shell embedded in a two-dimensional waveguide of height less than the length of the cylindrical scatterer. It is demonstrated that the acoustic metamaterials based on this building unit have negative acoustic parameters in a broad range of frequencies...
Coloring fuzzy circular interval graphs
Eisenbrand, Friedrich; Niemeier, Martin
2012-01-01
Computing the weighted coloring number of graphs is a classical topic in combinatorics and graph theory. Recently these problems have again attracted a lot of attention for the class of quasi-line graphs and more specifically fuzzy circular interval graphs. The problem is NP-complete for quasi-line graphs. For the subclass of fuzzy circular interval graphs however, one can compute the weighted coloring number in polynomial time using recent results of Chudnovsky and Ovetsky and of King and Re...
Energy dissipation in circular tube
A.D. Girgidov
2012-01-01
Energy dissipation distribution along the circular tube radius is important in solving such problems as calculation of heat transfer by the air flow through building envelope; calculation of pressure loss in spiral flows; calculation of cyclones with axial and tangential supply of dust-containing gas.Two types of one-dimensional radially axisymmetric flows in circular tube were considered: axial flow and rotation about the axis (Rankine vortex). Relying on two- and four-layer description of a...
Cylindrical-shaped nanotube field effect transistor
Hussain, Muhammad Mustafa
2015-12-29
A cylindrical-shaped nanotube FET may be manufactured on silicon (Si) substrates as a ring etched into a gate stack and filled with semiconductor material. An inner gate electrode couples to a region of the gate stack inside the inner circumference of the ring. An outer gate electrode couples to a region of the gate stack outside the outer circumference of the ring. The multi-gate cylindrical-shaped nanotube FET operates in volume inversion for ring widths below 15 nanometers. The cylindrical-shaped nanotube FET demonstrates better short channel effect (SCE) mitigation and higher performance (I.sub.on/I.sub.off) than conventional transistor devices. The cylindrical-shaped nanotube FET may also be manufactured with higher yields and cheaper costs than conventional transistors.
Effect of temperature on pyrolysis products from four nut shells
Energy Technology Data Exchange (ETDEWEB)
Demirbas, Ayhan [Department of Chemical Engineering, Selcuk University, Konya (Turkey)
2006-06-01
This article deals with slow pyrolysis of four shells such as hazelnut, walnut, almond and sunflower at the range of temperature 500-1200K in a cylindrical reactor batch reactor. The aim of this work was to experimentally investigate how the temperature affects char, liquid and gaseous product yields from different shells via pyrolysis. The amount of char from pyrolysis of the shell samples decreases with increasing the pyrolysis temperature. The highest liquid yields were obtained from the samples between 650 and 800K. The yield and the chemical composition of char can be calculated as functions of the pyrolysis temperature. The char components and higher heating values (HHVs) of shell fuels were correlated with pyrolysis temperatures. There were highly significant linear correlation between the pyrolysis temperature of the fuel and the fixed carbon content and HHV of char. (author)
Creep deformations of shells of revolution under asymmetrical loading
International Nuclear Information System (INIS)
In this paper the analytical formulation on the creep of axisymmetric shells undergoing unsymmetrical deformations is developed for two hardening laws: the time hardening law and the strain hardening law. The method is based on the creep power law, and on the assumption of plane stress condition and the Euler-Bernoulli hypothesis used in the ordinary thin shell theory. The basic differential equations derived for incremental values with respect to time are numerically solved by a finite difference method and the solutions at any time are obtained by integration of the incremental values. In conclusion the computer programs are developed which can be used to predict the creep deformations of arbitrary axisymmetrical shells. As a numerical example the creep deformation of cylindrical shell of importance in practical use is treated, and the variations of displacements and internal forces with the lapse of time are discussed. (Auth.)
Scattering from a Buried Circular Cylinder Illuminated by a Three-Dimensional Source
DEFF Research Database (Denmark)
Hansen, T.B.; Meincke, Peter
2002-01-01
We employ plane and cylindrical wave expansions with the fast Fourier transform to solve scattering problems involving a circular cylinder buried in soil. The illumination is provided by a three-dimensional source located in air above ground. Plane wave expansions describe transmitted and reflected...... fields at the air-soil interface, and cylindrical wave expansions describe the fields scattered by the cylinder. The two types of expansions are joined by employing explicit expressions that relate cylindrical and plane waves. We neglect multiple interactions between the cylinder and the interface. The...... cylinder and soil can have frequency-dependent permittivities and conductivities. With the formulas cast in a special form the scattered fields can be computed rapidly for fixed-offset configurations in which the location of the source is different for each observation point. Fixed offset is the most...
Cylindrical contact homology and topological entropy
Alves, Marcelo R. R.
2014-01-01
We establish a relation between the growth of the cylindrical contact homology of a contact manifold and the topological entropy of Reeb flows on this manifold. We show that if a contact manifold $(M,\\xi)$ admits a hypertight contact form $\\lambda_0$ for which the cylindrical contact homology has exponential homotopical growth rate, then the Reeb flow of every contact form on $(M,\\xi)$ has positive topological entropy. Using this result, we provide numerous new examples of contact 3-manifolds...
Cylindrical microemulsions: a polymer-like phase ?
Safran, S. A.; Turkevich, L.A.; Pincus, P
1984-01-01
The regions of stability of spherical, cylindrical, and lamellar phases of microemulsions are calculated within mean-field theory. In the cylindrical phase, thermal fluctuations determine a temperature dependent persistence length below which the cylinders are rigid (rod-like) and above which the cylinders are flexible (polymer-like). The length of the polymer-like chains depends on concentration and temperature. The radii of gyration of these flexible microemulsions are also calculated.
Shell ontogeny in radiolarians
Digital Repository Service at National Institute of Oceanography (India)
Anderson, O.R.; Gupta, S.M.
The ontogeny of the shells in modern and ancient radiolarian species, Acrosphaera cyrtodon were observed by scanning and transmission electron microscopy. The shells of A. cyrtodon were obtained from core samples collected from the Central Indian...
Spin and orbital angular momentum and their conversion in cylindrical vector vortices.
Zhu, Jiangbo; Chen, Yujie; Zhang, Yanfeng; Cai, Xinlun; Yu, Siyuan
2014-08-01
The generation of light beams carrying orbital angular momentum (OAM) has been greatly advanced with the emergence of the recently reported integrated optical vortex emitters. Generally, optical vortices emitted by these devices possess cylindrically symmetric states of polarization and spiral phase fronts, and they can be defined as cylindrical vector vortices (CVVs). Using the radiation of angularly arranged dipoles to model the CVVs, these beams as hybrid modes of two circularly polarized scalar vortices are theoretically demonstrated to own well-defined total angular momentum. Moreover, the effect of spin-orbit interactions of angular momentum is identified in the CVVs when the size of the emitting structure varies. This effect results in the diminishing spin component of angular momentum and purer OAM states at large structure radii. PMID:25078196
Wang, Xiahui; Xu, Miao; Ren, Hongwen; Wang, Qionghua
2013-07-01
We report a simple method to prepare an array of polarization converters using a twisted-azimuthal nematic liquid crystal (NLC) in cylindrical polymer cavities. When a NLC is filled in a cylindrical polymer cavity, LC in the cavity presents concentrically circular orientations. By treating LC on one side of the cavity with homogeneous alignment, a twisted-azimuthal texture is formed. Such a LC texture can convert a linear polarization light to either radial or azimuthal polarization light depending on the polarization direction of the incident light. The LC surface on the other side of the cavity is convex, so the light after passing through the cavity can be focused as well. The LC texture can be fixed firmly using polymer network. In comparison with previous polarization converters, our polarization converter has the merits of individually miniature size, array of pattern, and lens character. Our polarization converter array has potential applications in tight focusing, imaging, and material processing. PMID:23842407
Circular dichroism in XUV + IR multiphoton ionization of atoms
International Nuclear Information System (INIS)
Circular dichroism (CD) is theoretically considered for two-colour multiphoton ionization of arbitrary atomic subshells. In particular, p-subshell ionization is analysed and compared with s-subshell ionization. Simple analytical expressions for the CD are obtained for both s- and p-subshell ionization. The calculations performed for Ne(2p) ionization by an extreme ultraviolet pulse in the presence of an infrared laser pulse show that the CD in this case is appreciably larger than in previously discussed s-shell ionization. It makes this case favourable for applications as a sensitive tool for measuring the helicity of short-wavelength free-electron laser beams. (paper)
The covariant electromagnetic Casimir effect for real conducting spherical shells
Razmi, H
2016-01-01
Using the covariant electromagnetic Casimir effect (previously introduced for real conducting cylindrical shells [1]), the Casimir force experienced by a spherical shell, under Dirichlet boundary condition, is calculated. The renormalization procedure is based on the plasma cut-off frequency for real conductors. The real case of a gold (silver) sphere is considered and the corresponding electromagnetic Casimir force is computed. In the covariant approach, there isn't any decomposition of fields to TE and TM modes; thus, we do not need to consider the Neumann boundary condition in parallel to the Dirichlet problem and then add their corresponding results.
Energy Technology Data Exchange (ETDEWEB)
Takehiro, Shin-ichi, E-mail: takepiro@gfd-dennou.or [Research Institute for Mathematical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan)
2010-10-15
The kinetic energy budget analysis of spiraling columnar critical convection emerging in a rapidly rotating spherical shell is performed. In the cylindrical-radially elongated spiraling convection mode appearing as a critical mode at small Prandtl numbers, the kinetic energy generated in the inner region of the spherical shell is transported in a cylindrically radial manner and is dissipated near the outer boundary around the equator. However, when the Prandtl number is increased, the dynamical energy flux turns in the axial direction rather than in the cylindrically radial direction. The kinetic energy generated inside the shell is transported in the direction of the rotating axis and is dissipated near the outer boundary at the same cylindrically radial location. The existence of the axial component of the dynamical energy flux is attributed to the ageostrophic flows in the columnar vortices induced by viscous damping and buoyancy force. In spite of the existence of the axial component of dynamical energy flux, the obtained geometry of the axially integrated kinetic energy budget is consistent with the results using a two-dimensional rotating annulus model. Therefore, the interpretation of spiraling structure with the radial propagation properties of topographic Rossby waves is applicable to the three-dimensional spiraling columnar convection emerging in a rotating spherical shell. Flow patterns calculated from the dispersion relation of two-dimensional topographic Rossby waves in a rotating spherical shell well explain the structure of the three-dimensional spiraling columnar convection.