Abstract:

Ultrasonic techniques offer several unique advantages in nondestructive stress measurement. Most importantly, the ultrasonic energy propagates below the material surface, giving information on stress distributions away from the surface effects. Additionally, surface preparation requirements are minimal, enabling rapid collection of stress information from several locations in a component. Finally, the instrumentation necessary to collect and analyze the ultrasonic traveltimes required for stress evaluation is available in relatively light, compact, computer driven units that are easily moved into the industrial or laboratory work space. A brief overview will be given of the acoustoelastic effect, which is the basis for ultrasonic stress measurement. Both the acousticbirefringence (shear wave) and the critically refracted longitudinal wave (L[inf CR]) methods will be described. Examples of applications of the latter method for stress measurement in turbine components, rolled plate, ductile iron, and railroad rail and wheels will be described.