Quantitative Measurement and Evaluation of High-Resolution Ultrasonic Sound Fields using a Novel Automated Ultrasonic Immersion Scanner

Ultrasonic probes are an integral part of the automated ultrasonic non-destructive inspection machines to detect and size the defects in a wide range of materials in production lines. A complete quantitative assessment of the performance characteristics of an application-specific ultrasonic probe is needed to be evaluated on the basis of the European Standard DIN EN ISO 22232-2. This requirement not only improves the quality assurance of the manufactured probes but also provides the useful technical data to the end-user to optimize the ultrasonic testing on-site. In addition, the evaluation of probe characteristics should be carried periodically throughout their service life. The main aim of this work is to develop and validate a novel ultrasonic immersion scanner for the quantitative measurement and evaluation of ultrasonic sound beam characteristics of an application-specific UT Probe. A novel ultrasonic immersion scanner integrated with high-precision motion control unit (Hexapod) with six axes is developed to measure the full ultrasonic probe characteristics, which include the squint angle measurement in three different planes (XY, XZ, and YZ), RF-signal and its frequency spectrum at watersteel interface and sound beam parameters including the angle of beam divergence in different directions. The automated scanning, data acquisition, evaluation, visualization and test report generation are performed based on DIN EN ISO 22232-2. The measured sound beam characteristics of both focused and non-focused applicationspecific ultrasonic probes with center frequencies ranging from 0.2 - 15 MHz using the pulse-echo technique on a 3 mm half-ball steel reflector are presented. The quantitative analysis of the measured sound field parameters and the acceptance criteria in accordance with DIN EN ISO 22232-2 are discussed. By using the newly developed automated immersion scanner, we achieved a few micrometer (~15 µm) spatial resolution in the measured sound field patterns and a good angular resolution (~0.05°) in the squint angle measurement of a wide range of UT probes.