Nondestructive damage characterization with examples of thermal aging, neutron degradation and fatigue

Nondestructive Testing (NDT) in the engineering community is normally associated with the objective to detect, to classify and to size material nonconformities - for instance beginning with nonmetallic inclusions of a size of some ten µm in steel of Aluminum alloys up to so-called 'material defects' like macroscopic cracks of some mm size. This objective, however, is at the top of the list of activities concerning the number of applications in nondestructive material testing worldwide. Methodologies like UT(Ultrasonic Testing) and RT (Radiographic Testing) of MT (Magnetic Testing) are well introduced in a wide field of product and component examination standards. In the last 15 to 20 years, the NDT technology was also developed for characterizing materials, for instance in terms of microstructure parameters, i.e. lattice defects, like distributions and densities of dislocations, precipitates, micro-voids, in order to describe strengthening and/or softening in materials, mainly in metal alloys, but also to measure the applied and residual stresses (Dobmann et al., 1989).