Adaptive ultrasonic technique for inspection of complex geometry components with a matrix array

Abstract

Ultrasonic phased-array technology is widely used in many NDT (Non-Destructive Testing) fields. Its ability to electronically steer and focus ultrasonic beams allows for comprehensive inspections with improved accuracy. However, the performances of an ultrasonic inspection may be degraded when the component being inspected exhibits an uneven surface. If the surface geometry is unknown, phased array technology is unable to correct the perturbations of acoustical beams using array settings. In this work, we present a new immersion adaptive inspection technique of large and complex-shaped components using a matrix array. In this approach, first, the unknown surface geometry of the inspected component is reconstructed from a series of 2D TFM images collected using only one row and one column of the matrix array acting as two independent orthogonal 1D arrays, in conjunction with mechanical 2D scanning. At this stage, the recorded 2D images are combined into a single wide-view 3D surface image by rotational SAFT algorithm, a simplified version of the standard SAFT method. The desired surface is extracted from the resulting image using an automatic global thresholding method. Then, based on the reconstructed surface and given the inspection probe trajectory, adapted focal laws to inspect the interior of the component are computed and applied at every location of the probe to correct the effect of the surface. The capabilities of the proposed inspection technique are illustrated by various simulated and experimental results carried out in a water tank. Its advantages and drawbacks will be discussed.