NDT for small defects by x-ray tomography.

Computer tomography (CT), originally developed for medical purposes is becoming increasingly applied to nondestructive testing. The main reason for this is its ability to produce shadow free, high contrast images of object slices, which is an advantage in comparison to radiography. This study proposes the methods for theoretically determining the kind of materials which can be scanned. This is a function of the CT-System at hand, and the interdependent contrast and spatial resolutions. The tradeoff between these two factors is discussed. Furthermore it is shown how the smallest detectable flaw sizes for given materials can be estimated. Ways to enhance the quality of a tomogram, with respect to resolution, noise, flaw detection and artifacts are discussed. Experimental results with a medial system and examples verifying the theoretical predictions will be discussed. Also presented are initial results obtained with a high resolution tomography system presently developed at the IzfP. (IZ FP)