An investigation into ultrasonic probes for high resolution non-destructive testing
This thesis describes a theoretical and experimental investigation into compressional wave ultrasonic probes for use in high resolution non-destructive testing. In the theoretical section, the pulse performance of the ultrasonic probe is analysed in detail. The response of the piezoelectric transducer is initially determined by direct time domain analysis of electrical equivalent circuits and specially devised computer programs are then used ito predict the performance of various probe constructions The effects of intermediate layers lying between the transducer and the backing and between the transducer and the job are included. In the experimental section, the design, construction and subsequent performance of high resolution probes is described. Both contact and immersion probes are included, the former having a resonant frequency of 5MHz, and the latter having resonant frequencies of 5MHz and 10MHz. Whilst the computer analysis does not extend to contact probes, agreement between predicted pulse shapes and those obtained experimentally is excellent in the case of immersion probes. In addition to pulse shapes, full details of such aspects as repeatability of probe performance, suppression of acoustic waves in the backing and experimentally observed beam-profiles are also given. Finally, the performance of a single immersion probe having a resonant frequency of 20MHz is described and some suggestions for further work are given.