Modelling the beam/defect interaction by sampling of the ultrasonic beam

We present here a model describing the behaviour of an ultrasonic focused beam when it is intercepted by a planar defect located in a structure with parallel faces. It is a 2D model, using a sampling of the acoustic pressure in the beam and based on the fact that in the focused area, waves surfaces are flat and perpendicular to the axis of propagation. The crossing of interfaces are taken into account through the coefficients of refraction/reflexion in the computation of amplitudes. This type of approach, in spite of its simplicity, allows realistic predictions on relative amplitudes of detection and echodynamic curves. Some experimental results allow to judge of the validity of the model, so far as initial assumptions are valid