AN IMPROVED ULTRASONIC TECHNIQUE FOR THREE DIMENSIONAL INCLUSIONS 0.1. Lobkis and K.I. Maslov Institute of Chemical Physics Russian Academy of Science Kosygin str.4, 117334 Moscow, Russia T. Kundu Department of Civil Engineering and Engineering Mechanics University of Arizona, Tucson, AZ 85721, USA P.V. Zinin Institute for Material Science and Structure Research University of Bremen, 28334 Bremen, Germany INTRODUCTION Conventional C-scan ultrasonic techniques are excellent for imaging two dimensional defects such as delaminations, cracks, and plate type inclusions [1]. This technique is most effective when these defects are oriented parallel to the scanning plane. However, for three-dimensional inclusions difficulties are encountered when the conventional scanning technique is adopted. If one wants to reconstruct the three dimensional inclusion from generated C-scan images at different depths a significant amount of error is introduced in its size and shape. Even for a simple 3D object such as a sphere it is often difficult to accurately estimate its size and location from its C-scan generated image. The V(z) curve method, used in acoustic microscopy, is an effective quantitative method for investigating planar objects [2] and not fully developed for nonplanar objects. The aim of this paper is to extend the V(z) curve method to spherical objects. It is shown that from the positions of different peaks in the V(z) curves one can determine the size and acoustical parameters of solid spherical particles in a liquid or a solid. THEORY First we consider the spherical particle in an immersion liquid. Review of Progress in Quantitative Norukstructive EvalUDlion. Vol. 14 Edited by D.O. Thompson and D.E. Chimenti. Plenum Press. New Yark. 1995 123