| Abstract: | A theoretical and practical framework of different problems has been discussed to explain advantages and limitations of techniques based on electrical sensing methods which are consistent to implement structure evaluation of materials. The term  structure evaluation is generally used here to mean extracting the quantitative information of interest of a material or an object to be examined from a physical measurement, or more typically from a set of physical measurements, that themselves may be only indirectly related to the quantitative information desired. The paper emphasizes the point that the structure evaluation is a typical inverse problem and as such is made more difficult, since inverse problems are characteristically illconditioned, that is, small errors in the measurement typically lead to large errors in the solution. Use of physically motivated a priori information to diminishing such ill-conditioning is discussed. Features of updated electrical sensing methods, particularly those used for nondestructive testing (NDT) are considered. Potential advantages of the electrical methods compared to other NDT techniques are that they offer inexpensive, safe, nonharmful, and fast testing. Some novel achievements including excitation with a number of complex electric field excitation patterns on the object together with computer-assisted information acquisition have considerably extended both the potential and the scope of the electrical methods which will still be recognized. In order to present an up-to-date perspective, some conceptual and methodologic aspects have been considered for two structure evaluation problems, i.e., for generating a) algorithms for determining structural parameters of materials, such as density, moisture content, polymerization degree, etc., from dielectric spectra; b) tomographic cross-sectional maps of electrical parameters of the object to be examined.Presented at the Ninth International Conference on the Mechanics of Composite Materials, Riga, October, 1995.Institute of Polymer Mechanics, Riga, Latvia. Published in Mekhanika Kompozitnykh Materialov, No. 1, pp. 124–134, January–February, 1996. |
