Pulse Compression Ultrasonic Non Destructive Evaluation of Thick Polymer Samples

The use of ultrasonic signals at sub-MHz frequencies for Non Destructive Evaluation of thick polymer samples is described. It will be shown that the combination of low-frequency coded signals such as chirps, together with appropriate signal processing methods such as pulse compression, can provide a powerful tool for ultrasonic NDE. To achieve this goal, it is essential that the measurement system bandwidth is as wide as possible, and matched to the type of waveform chosen for the measurement. In this work, the required bandwidth is achieved by using piezo-composite probes and it will be demonstrated how the combination of pulse compression techniques and broadband probes can be used to inspect highly attenuating materials such as thick polymers. In particular, the application of pulse compression is shown to help in the NDE of flexible riser stiffeners, used extensively in the offshore oil and gas industries.