Ultrasonic inspection of composite hydrogen reservoirs using frequency diversity techniques

The use of the signal processing techniques based on the principle of quasi-frequency diversity can be a suitable solution for the ultrasonic inspection of liquid hydrogen tanks manufactured out of composite materials. Nevertheless, the algorithms developed up to now suffer from limitations that restrict their large-scale use. The split-spectrum processing requires preliminary adjustments that are not always accessible to the user, while the cut-spectrum processing is not sensitive enough to eliminate the noise. We have thus developed an interesting alternative to these two filters. Based on the use of progressive low-pass filters, this algorithm, called low-spectrum processing, takes into account the physical characteristics of the ultrasonic wave propagation in a composite material. Its use in the inspection of tanks made in composites showed better performances.