Abstract
Crack is the most dangerous defect in machines and structures. Cracking often initiates from the surface of materials, since the surface stress is often higher than the stress of inside when a metal is under load. Nondestructive evaluation of a small crack is always regarded as a difficult but an utmost important issue for the integrity assessment of structural components. Recently, small cracks have been detected successfully by using microwaves under a condition of no contact and without any coupling medium, and a dual frequency technique has been developed to evaluate the size of surface cracks in metals. In the present paper, a study of evaluation of the shape and size of 3-D cracks using an enhanced microwave dual frequency technique is reported.
