DIRECTIONALITY OF THE SCATTERING OF THE A0 LAMB WAVE MODE AT CRACKS

Localized and distributed array systems for guided ultrasonic waves offer an efficient way for the long‐term monitoring of the structural integrity of large structures. However, the detection sensitivity for fatigue cracks depends on the orientation of the crack relative to the position of the transducer elements. Finite Element (FE) simulations show that for cracks and slots no energy is scattered in certain directions from the defect. Crack‐like defects have a directionality pattern of the scattered field depending on the angle of the incident wave relative to the crack orientation and on the ratio of the characteristic defect size and depth to wavelength. Simulation predictions are compared to laser measurements of the scattered wave field at machined part‐through and through thickness notches. Good agreement is found and the directionality pattern can be predicted accurately. These results provide the basis for the quantification of the detection sensitivity for defects in plate structures using guide...