Volume 29, Issue 3 (May 2001)
Ultrasonic Technique for Experimental Evaluation of Structural Integrity
An approach for an entirely experimental evaluation of the structural integrity of components or structures is presented. The approach is based on measurement, through ultrasonic techniques, of the effects induced on the local stress field by the presence of flaws in a structure. Due to the phenomenon of acoustoelasticity, such effects produce a variation in ultrasonic wave propagation velocity. From measurement of the wave propagation time within the material it is possible to calculate directly the stress intensity factors KI and KII, even in the case of mixed mode. The typical measurement chains for classic ultrasonic inspection are utilized in this approach. It is suitable in particular for utilization in conjunction with automated ultrasonic inspection techniques, inserting high-frequency transducers in the array of probes, and utilizing suitable analysis software. The results of tests conducted on specimens with fatigue cracks in different load conditions are reported.