Morteza Eskandari-Ghadi - Dept. of Engineering Science, Faculty of Engineering, University of Tehran, Tehran, Iran.
Mohammadreza Mahmoodian - Dept. of Civil Engineering, Science and Culture University, Tehran, Iran

A cylindrical cavity of finite length is considered in a transversely isotropic linear elastic half-space with depth wise axis of material isotropy. The purpose of the paper is to determine the displacements and stresses fields in the interior of the half-space when cylindrical cavity is under the effect of a timeharmonic torsion moment applied on a ring at an arbitrary depth on the surface of the cavity. Using cylindrical coordinate system, it is convenient to consider the response of the elastic solid in two separate regions, which have some continuity conditions. By considering the equation of motion in each region and with the aid of Fourier cosine integral transform, the boundary value problem for the fundamental solution is reduced to a generalized Cauchy singular integral equation. By solving the governing integral equation, the shear stress and the angular displacement are obtained at any point. To confirm theevaluation, comparisons with existing solution for the static case of isotropic material are included, where there exists an excellent agreement. To investigate the effect of material anisotropy and the frequency of excitation, the results are numerically evaluated and illustrated

Torsion, Transversely isotropic, Fourier cosine transform, Singular integral equation,Boundary value problem