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.
