The impulsive Reissner-Sagoci problem in a composite medium

The small-time Reissner-Sagoci problem in a bi-material elastic half-space under an impulsive twist is investigated. The problem is reduced to an integral equation, which, by asymptotic analysis and application of the Wiener-Hopf technique, is further reduced to a Fredholm integral equation of the second kind. Approximate analytical results, whose accuracy can be improved by retaining higher order terms in the approximations, are obtained for the free surface displacement outside the disc and the reactive couple necessary to keep the disc in the twisted position, for a bi-material medium with small shear wave speed disparity between the two media.