Impact-echo from a unilateral interlayer crack. LCP-BEM modelling and neural identification

The reflection of elastic waves from subsurface interlayer unilateral crack s, with the possibility of crack closing (contact) and frictional effects, is studied by dynamic boundary element method (BEM) combined with a linear complementarity problem (LCP) formulation. The effect of the unilateral cra ck on the impact-echo response is studied by means of numerical experiments . Further, a neural network model is proposed and tested for the classifica tion of the data based on the numerically generated waveforms, The position or the size of the sublayer crack can be identified from the trained neura l network. (C) 1998 Elsevier Science Ltd. All rights reserved.