Analysis of acoustic field characteristics to detect internal pipeline corrosion based on ultrasonic full-focus

Abstract Seawater pipelines are an important part of ship structures. After a certain period of service, corrosion becomes a serious problem. Ultrasonic corrosion detection has good applicability in seawater pipeline corrosion detection. Aiming at the focusing problem of ultrasonic arrays in pipeline inspection, the sound pressure characteristics and acoustic field directivity in the propagation process were analyzed. A mathematical model of the acoustic field propagation characteristics was established, and the influence of deflection, focusing of the sound beam, and geometric characteristics of the array element on the characteristics of the ultrasonic acoustic field were analyzed through simulation calculations. An ultrasonic array focusing transducer was used to test the corrosion of a Φ168 pipeline. The results show that the number, size, and focal length of the working array significantly affect the focused acoustic field characteristics of the ultrasonic array. The ultrasonic full-focus method can effectively detect local corrosion of pipelines, and the defect detection accuracy has a nonlinear relationship with the number of working array elements and the focal length of the focus. Within a certain range, with an increase in the number of working elements, the overall tendency of the average error of defect detection gradually decreases. With the increase in focal length, the overall tendency of defect detection error first decreases and then increases, and there is a focal length range with the best detection accuracy. In pipeline inspection, the best working parameters can be selected according to the actual size of the pipeline.