A MODEL FOR PREDICTING EFFECTS OF SURFACE-WAVE PROPAGATION ON THE ECHO RESPONSE FROM PLANAR CRACKS

A system model is presented for predicting surface wave effects arisin g in crack diffraction. The model includes the computation of the time -dependent field incident upon the crack, radiated through the interfa ce between the coupling medium and the piece. The crack scattering is computed by the Geometrical Theory of Diffraction (GTD) extended to th e transient case for treating wideband transducers, typical of those u sed in nondestructive measurements. A transient model for reception by the transducer of the scattered field is developed for the prediction of inspection in immersion testing. It accounts for the specific symm etry of the diffracted waves (cylindrical waves arising from the near and far tips of the crack). Numerical results for a realistic testing configuration are given and discussed. (C) 1998 Elsevier Science B.V.