Propagation of plane harmonic waves through contact with a micro gap

Propagation of harmonic waves through a micro gap between two half-spaces with consideration of smooth contact is studied. When waves which are strong enough strike the surface of one of the solids, the two solids can come into contact and interact locally. By use of Fourier analysis method, the problem is solved analytically; and the gap effects are discussed in detail. The results exhibit some new features induced by the interface contacting. The relation between the higher harmonics and the initial gap width is developed which may be effective on non-destructive testing of a pre-existing gap.