Zhong Weifang

Computation of Young’s moduli for chiral single-walled carbon nanotubes

An energy-equivalent model is proposed to establish the computational formula of Young’s modulus for chiral single-walled carbon nanotubes (SWCNTs). First, the total system potential energy is obtained using the principle of molecular mechanics. Then, the computing formula of Young’s modulus of chiral SWCNT is obtained by comparing the total molecular potential energy with the strain energy of a corresponding thin cylinder. It is found that Young’s modulus of a chiral SWCNT is affected both by its diameter and chiral angle.

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.

Low velocity impact response analysis of shape memory alloy reinforced composite beam

The low velocity impact responses of shape memory alloy (SMA) reinforced composite beams were analyzed by employing the finite element method. The finite element dynamic equation was solved by the Neumark direct integration method, the impact contact force was determined using the Hertzian contact law, and the influence of SMA fibers on stiffness matrix is studied. Numerical results show that the SMA fibers can effectively improve the low velocity impact response property of composite beam.

Linearized inverse scattering for elastic parameters in a half-space with reflection data

The multi-parameter inversion of elastic wave equation in a half-space within the Born approximation is studied. A method of simultaneously reconstructing the configurations of the density and Lamé parameters of the medium was presented by use of a wideband measuring schemes in which transmitters and receivers scan over the half-space surface. It is shown that the reflected waves generated by horizontal and vertical pulses on the surface can be decomposed into P→P, P→S, S→P and S→S types of scattering components. As is expected, these components contain enough information for desired restruction. From them the density and two Lamé parameters are determined explicitly, and the results obtained have the form of filtered back-propagation as in the acoustic diffraction tomography.

CRACKED STRUCTURE-ACOUSTIC COUPLING PROBLEMS BY HYBRID FRACTAL FE AND BE METHODS

Evaluation of the sound-structure interaction is important for effective control of noise and vibration in structural acoustic systems. Cracked elastic structure-sound interaction problems are studied by employing the hybrid fractal FEM and BEM. The degrees of freedom of the system can be reduced greatly through adopting fractal FEM in discretizing the cracked elastic structure; while the exterior acoustic field is calculated by BEM, which automatically satisfies Sommerfeld’s radiation condition. Numerical examples are given and show that the resonant frequencies of the structure-acoustic coupled system decrease as the depth of the crack increases, and that the crack has a significant effect on the acoustical field in the vicinity of the crack tip.

MODE ANALYSIS OF STRUCTURES USING THE FOURIER P-ELEMENT METHOD

The Fourier p-element method is an improvement to the finite element method, and is particularly suitable for vibration analysis due to the well-behaved Fourier series. In this paper, an iteration procedure is presented for solving the resulting nonlinear eigenvalue problem. Three types of Fourier version shape functions are constructed for analyzing the circular shaft torsional vibration, the plate in-plane vibration and annular plate flexural vibration modes, respectively. The numerical results show that this method can achieve higher accuracy and converge much faster than the FEM based on polynomial interpolation, especially for higher mode analysis.

On the method of equivalent inclusions in elastodynamics and the scattering fields of two ellipsoidal inhomogeneities

Gurtins variational principle is used to derive the equivalence equations for general linear elastodynamical problems of multiple inhomogeneities. An approximate expression on scattering field of two ellipsoidal inhomogeneities is obtained by the method of equivalent inclusions. And some numerical examples are presented.