SCATTERING OF AN ULTRASONIC PULSE BY A TWO-DIMENSIONAL CRACK IN SOLID——GENERAL THEORETICAL ANALYSIS

Scattering of elastic waves by obstacles of various shapes, especially those having sharp edges, is an important problem in NDE. The problem of scattering of a plane longitudinal or SV ultrasonic pulse in a solid, by a crack of finite width but very large length and with free faces is investigated in this paper by applying Laplace transforms and the generalized Wiener-Hopf technique, and a solution in the Laplace domain for the scattered field is obtained. For a wide crack, an approximate form of the solution is formulated, which can be inverted by the Cagniard-de Hoop method. The approximate solution in the time-space domain gives the major features of scattering in the early time and hence of the near field. We have also experimentally studied the corresponding scattered ultrasonic field in glass by the use of the photoelastic visualizing technique, but the results are not included here.