The application of nondestructive testing (NDT) to the engineering aspects of the fatigue phenomenon offers a classic example of the systems approach that is essential for the successful exploitation of nondestructive testing technology. NDT can make contributions in: the fracture mechanics-nondestructive testing design criteria and related product integrity determination; detection of property-stress gradients; early detection of fatigue damage; and evaluation of stresses.
Earlier work established the ascendancy of ultrasonic testing. Notable advancements in recent work have been in the refinement of data treatment of ultrasonic responses from defects aimed at accomplishing more reliable size assessment and in scanning of large components.
The following NDT methods have demonstrated potential for measurement of fatigue damage: exoelectron emission, acoustic emission, ultrasonic surface wave attenuation and velocity, surface potential difference, ellipsometric parameters, holographic surface correlation index, and positron life times.
Stresses play an important role in failure point detection, location, and growth, and in practical cases, must be measured for each part.
Effective utilization of nondestructive testing at any one portion of the product cycle as related to the fatigue problem requires that it be considered in a system connotation.