Ultrasonic defect imaging and sizing technique

摘要

Defect sizing with ultrasound means for practical applications that depth and length extension of an ultrasonic reflector has to be determined exactly enough to be used by a fracture mechanical specialist. Under practical circumstances this leadsto the application of a concept including the use of conventional evaluation techniques (e. g. based on crack tip or half value extension or amplitude judgement) as well as applying some more specialized techniques like focussing probes, acousticholography, synthetic aperture focussing technique and others. This contribution describes some of the specialized techniques and the typical characteristic behaviour, the resolution and the limitations and applicability ranges. The description of aspecialized defect sizing approach does not mean that the application of one simple technique will solve the sizing or imaging problem in all cases. More often it is necessary to combine informations from different sources to derive a reliable answer tothe sizing question. If imaging is required in order to have a better understanding of the defect origins the resolution power of the special technique is a main criteria which must be regarded. Different approaches and corresponding applications will bedescribed in this contribution.