Zou Zhen-zhu

Interaction of axially symmetric waves with an annular crack in an infinitely long hollow cylinder

In this paper an analysis of the interaction of longitudinal waves with an annular crack in an infinitely long hollow cylinder is presented. Using Fourier sine and cosine as well as Hankel integral transforms, formal complete solutions to the governing equations are given. By means of Abel integral transform, the problem is reduced to the solution of a Fredholm integral equation of the second kind which is, then, solved numerically for a range of values of the frequencies of the incident waves. The numerical values of the dynamic stress intensity factor at the rim of the crack have been calculated.

Dynamics of constrained mechanical systems and its application in robotics-implementation

Abstract In this paper, based on the orthogonality of the tangent space and normal space, the construction of the constrained system was studied and two implemental methods were proposed. These two methods make full use of recursive processes which reflect the hierarchical nature of the structure of the constrained system. Every recursive step has been standardized and the complexity in the dynamic analytical modelling and analysis has been greatly reduced. A hand-like multibody system is taken as an example to illustrate the usefulness and effectiveness of the methods proposed in this paper.

Impact response of a finite interface crack with adhesive tips

Of considerable importance in structural analysis is the transient response of a flaw to a time dependent stress field. A number of papers on the area of dynamic crack analysis have been reviewed in [ 1]. The impact response of a finite crack in plane extension has been considered in a paper by Sih and Embley [2]. Impact response of the interface crack is, however, a very complex problem due to the strong discontinuity of the material constants. The general elasticity solutions, that have been worked out for such a crack, involve oscillatory singularities which lead to wrinkling of the crack and overlapping of the materials [3]. These unreasonable phenomena have bothered scholars and research workers for a long time. In 1977, Comninou [4] proposed a frictionless contact model and solved the relevant static problem. The size of the contact region that is worked out according to the model is, however, too small to be acceptable to the assumption of continuum mechanics. In 1978, J.D. Achenbach [5] proposed another model which assumed that the crack faces are in adhesive contact near the tips. He solved the static problem and obtained some excellent results. The scattering of steady elastic waves by this kind of crack has been considered in a paper by Zhou Zhengong [6], and Rice [7] has further considered static contacting problems of the interface crack.

Axisymmetric Elastodynamic Response from a Penny-Shaped Interface Crack in Layered Composites

This paper is concerned with the scattering of time harmonic longitudinal wave by a penny-shaped interface crack in layered composites. By Hankel and Abel integral transform, the problem is reduced to a set of singular integral equations which are treated numerically by Jacobi polynomials. The improper integrals in the equations are delt with by contour integral technique so that the accuracy of numerically computing is guaranteed. As an example, the scattering surface displacement field of elastic wave by a penny-shaped interface crack in a layered half space has been investigated in far field case. The theoretical results show that the surface displacements are composed of Rayleigh-Like-Mode waves predominantly. The scattered amplitudes for the first two modes are plotted versus the incident frequency, and it is observed that the multi-resonances occur in a frequency range.