Huang Yuying

Bifurcations of a cantilevered pipe conveying steady fluid with a terminal nozzle

This paper studies interactions of pipe and fluid and deals with bifurcations of a cantilevered pipe conveying a steady fluid, clamped at one end and having a nozzle subjected to nonlinear constraints at the free end. Either the nozzle parameter or the flow velocity is taken as a variable parameter. The discrete equations of the system are obtained by the Ritz-Galerkin method. The static stability is studied by the Routh criteria. The method of averaging is employed to examine the analytical results and the chaotic motions. Three critical values are given. The first one makes the system lose the static stability by pitchfork bifurcation. The second one makes the system lose the dynamical stability by Hopf bifurcation. The third one makes the periodic motions of the system lose the stability by doubling-period bifurcation.

Postbuckling analysis of plates on an elastic foundation by the boundary element method

Abstract The postbuckling behavior of plates on an elastic foundation is studied by using the boundary element method (BEM). A new fundamental solution of lateral deflection is derived through the resolution theory of a differential operator, and a set of boundary element formulae in incremental form is presented. By using these formulae, the BEM solution procedure becomes relatively simple. The results of a number of numerical examples are compared with existing solutions and good agreement is observed. It shows that the proposed method is effective for solving the postbuckling problems of plates with arbitrary shape and various boundary conditions.

New matrix method for response analysis of circumferentially stiffened non-circular cylindrical shells under harmonic pressure

Based on the governing equation of vibration of a kind of cylindrical shells written in a matrix differential equation of the first order, a new matrix method is presented for steady-state vibration analysis of a noncircular cylindrical shell simply supported at two ends and circumferentially stiffened by rings under harmonic pressure. Its difference from the existing works by Yamada and Irie is that the matrix differential equation is solved by using the extended homogeneous capacity precision integration approach other than the Runge-Kutta-Gill integration method. The transfer matrix can easily be determined by a high precision integration scheme. In addition, besides the normal interacting forces, which were commonly adopted by researchers earlier, the tangential interacting forces between the cylindrical shell and the rings are considered at the same time by means of the Dirac-δ function. The effects of the exciting frequencies on displacements and stresses responses have been investigated. Numerical results show that the proposed method is more efficient than the aforementioned method.

Vibration analysis of segmented shells coupled with liquid using a mixed FS-BE method

An analysis is presented for the coupled vibration of segmented shells submerged in or filled with liquid. To improve computing efficiency, the finite strip (FS) technique was used to analyze the segmented shell. As for the liquid area, a special boundary element (BE) was proposed. Compared to the classical boundary element method (BEM), this BE not only guarantees the continuity condition on the liquid-shell interaction plane, but also has fewer unknowns. By using Bernoullis law and the continuity conditions on the shell-liquid interaction plane, the influence of liquid area was simplified to an added mass matrix; therefore, the shell-liquid systems governing equations, shells FS equation, and liquids BE equation are decreased to a group of refined equations that has the same form of FS equation with a modified mass matrix. The method has been applied to a typical segmented shell-liquid system, and the natural frequencies, mode shapes, and response of vibration were calculated numerically. It shows that the method shown here has good efficiency and precision in computing and can analyze the arbitrary rotating shell-liquid system easily. *Communicated by Z. Mróz.

A New Ultra-low Frequency Passive Vertical Vibration Isolation System

A new ultra-low frequency passive vertical vibration isolation system is constructed by connecting the torsion spring isolator with a reverse pendulum. The theoretical analysis shows that the new system can achieve a much longer resonant period and have a smaller size than the current torsion spring isolators with the same geometric parameters.

A variational solution of coupled vibration for moderately thick floating plate seated on the sea floor with variable water depth

Based on Reissners plate theory, a localized variational principle for the coupled vibrations of moderately thick floating plates seated on the sea floor with variable water depth is presented in this paper. It will be a powerful tool to formulate various approximate methods of moderately thick floating plates. By means of this variational principle a formula for calculating the natural frequencies of moderately thick floating plates is also obtained. A numerical example shows that high accuracy and computational time saving may be achieved in calculation.

A Direct Method for Deriving Fundamental Solution of Half-plane Problem

A fundamental solution for half-plane problems which will play a key role in calculation of the stress concentration around a hole embedded in half-plane is derived by a method combining images with direct integrations. It is more intuitive than the Fourier transform method used by Gladwell[6]. In addition, the principle and procedure of boundary element method to solve the half-plane problems are also presented by means of Bettis reciprocal theorem in this paper.A fundamental solution for half-plane problems which will play a key role in calculation of the stress concentration around a hole embedded in half-plane is derived by a method combining images with direct integrations. It is more intuitive than the Fourier transform method used by Gladwell[6]. In addition, the principle and procedure of boundary element method to solve the half-plane problems are also presented by means of Bettis reciprocal theorem in this paper.It is shown that the computing procedure for half-plane problems is much more convenient using the fundamental solution presented here than the one adopted by C.A. Brebbia[1].

A direct method for deriving fundamental solution of half-plane problem

A fundamental solution for half-plane problems which will play a key role in calculation of the stress concentration around a hole embedded in half-plane is derived by a method combining images with direct integrations. It is more intuitive than the Fourier transform method used by Gladwell[6]. In addition, the principle and procedure of boundary element method to solve the half-plane problems are also presented by means of Bettis reciprocal theorem in this paper.A fundamental solution for half-plane problems which will play a key role in calculation of the stress concentration around a hole embedded in half-plane is derived by a method combining images with direct integrations. It is more intuitive than the Fourier transform method used by Gladwell[6]. In addition, the principle and procedure of boundary element method to solve the half-plane problems are also presented by means of Bettis reciprocal theorem in this paper.It is shown that the computing procedure for half-plane problems is much more convenient using the fundamental solution presented here than the one adopted by C.A. Brebbia[1].