Detection and measurement of flaws play a major role in an emerging “fail-safe” philosophy of structural design and evaluation [1]. This philosophy allows the existence of flaws in parts in service but requires that the flaws be identified, measured and evaluated to determine if they could lead to catastrophic failure during the design life of the part. In this way greater use is made of the part, leading to considerable savings in materials and manufacturing costs. These savings come at the expense of the development of nondestructive inspection technologies that are required for flaw detection, identification and sizing
