Using of Microwaves at Investigation of Solid Materials Inhomogenities

Non-destructive testing (NDT) as a part of many technologies includes various techniques for detecting undesirable random events accompanying industrial and operating processes. These NDT techniques must be adjusted to individual needs and materials. From this point of view it would be serviceable to dispose of a technique applicable for as much as possible testings and also e.g. NDT application without a conducting transducers to test conductive materials, dielectrics and things like that. Among most occurring defects belong cracks more particular not only the traditional cracks in metals, but currently, with the developing automobile, aircraft and also ship industry and cracks detection in plastics is becoming important, too. More methods for such defects determination are used and we will mention only some of them. The electromagnetic non-destructive evaluation of metal surfaces can be accomplished using thin – eddy current, AC field measurement, and microwave techniques. Besides using microwaves on plastic NDT, a considerable attention is being given to the microwave NDT of metals. The main competing technologies with microwave NDT are ultrasound, eddy current and thermal imaging. Ultrasonic waves usually require a contacting media. Microwaves also allow the crack detection under various coating [1] without the need for coating removal prior to testing. Microwave can potentially generate higher resolution images with deeper penetration then the thermal and eddy current techniques [2]. More microwave techniques can be used for verifying their suitability for this purpose. Having considered these circumstances also with regards to the extensive area of using microwaves (e.g. [3] gives 25 investigations by means of microwaves) we decided on the basis of theoretical assumption to take heed of using microwaves for these purposes.