Effect of Focal Law Parameters on Probability of Detection in Phased Array Ultrasonic Testing Using a Simulation and Case Study Approach.

The growing energy industry has demands for high-quality, cost-effective solutions in design, fabrication, and inspection. Nondestructive testing (NDT) has always played a crucial role in the overall product integrity. Phased array ultrasonic testing (PAUT) is one of the advanced inspection technologies that promises to become the primary inspection technique for most applications in the industry. PAUT has immense inherent capabilities but, as a system, possesses controllable and uncontrollable variables, which influence its reproducibility, repeatability, and detection capability. In general, the challenge of NDT system capability is further compounded by the latest advancements in material and product diversities, which demand system validation. Validation using simulation software is likely to be a promising alternative to conventional validation techniques that utilize specimens with known reflectors. Simulation software takes into account most of the influential parameters involved during an inspection regarding the transducer, geometry, and material inspected. This paper provides outcomes on the effects of focal law parameters of PAUT on probability of detection in the aspects of detectability, resolution, and sizing of flaws. Several S-scan plans were formulated using focal parameters, including element quantity, pitch, focal depth, range of angle, and angle resolution. All of the scan plans were analyzed using simulation and practical trials to derive the best scan plan in terms of detectability, resolution, and sizing. Factors affecting the PAUT signal response due to the NDT system (probe configuration and scan plan), part (geometry and material properties), and flaw (size and orientation) were accounted for. However, other factors, including psychological and physiological human factors, were not considered. The study infers that for an effective PAUT examination, focal law parameters must be validated either through practical or simulation approach. In addition to proving the necessity of validating the focal law parameters, a simulation approach to evaluate the smallest detectable discontinuity based on effective scan plan was also done. [ABSTRACT FROM AUTHOR]