Ultrasonic stress measurement using PC based and commercial flaw detectors

The determination of the stress field inside metallic parts is one of the most important challenges to the designer. Although the prediction of the stress distribution can be done by several numerical and empirical methods, the real stress value is almost always unknown. Several destructive and nondestructive techniques have been tested to accomplish this task, including the application of x rays, saw cut, neutron diffraction and so on, but none of them seems to have a suitable correlation between cost and applicability. Ultrasonic techniques have been used for flaw detection since the 1950s. The main application was in the identification of cracks and voids. In this work we present the application of ultrasound in the evaluation of a one-dimensional stress field using the longitudinal critically refracted waves (LCR). A new ultrasonic LCR probe is presented and its performance is evaluated using PC based instrumentation. Also, the LCR waves’ sensitivity is verified using a low cost commercial flaw detect...