Global total focusing method through digital twin and robotic automation for ultrasonic phased array inspection of complex components

This paper tackles the challenging ultrasonic inspection of parts with complex geometries by proposing a novel global TFM (gTFM) approach. In this method, a digital twin is used to optimize and control the inspection, which consists of the probe being scanned around a complex part using a robotic arm, finally rendering a gTFM image by combining all acquisitions. To verify its validity, an aerospace disk forging mock-up, with side-drilled holes (SDH), was used. The mock-up geometry comprised multiple concave and convex surfaces. A comparison of different scan plans showed that adapting the probe position to the surface profile improved the imaging performance. Furthermore, by using a typical constant probe standoff, strong reconstruction artifacts were generated, inevitably rendering the inspection unreliable. On the other hand, by using an optimal scan plan, the gTFM image showed a sharp image of the SDHs. Compared to the other strategies, the optimal scan plan achieved a 40% increase in the mean contrast-to-noise ratio (CNR), a 70% reduction in the position error (only 0.1 mm), and a reduction of 33% in the array performance indicator (API). Inspection coverage was achieved efficiently, depicting the complete cross-section of the specimen using only 7 probe positions.