Measurement of velocity and attenuation for ultrasonic longitudinal waves in the polyethylene samples

The plastics pipes are used widely for water and gas supplies and for different applications in industry. The non-destructive testing (NDT) of the welded joints of such pipelines is very important for the safety and long life time of them. The main technique used for it is ultrasonic NDT. The specific physical-mechanical properties of the plastics used for manufacturing of the pipes require the ultrasonic properties of them to be well known. The aim of investigations described in this article is measurement of the velocity and the attenuation of ultrasonic longitudinal waves in the material of plastic pipes. The set of polyethylene PE80 test samples of different thickness in the range from 2.5 mm up to 20.0 mm were investigated. The measurements were performed using contact through-transmission technique and ultrasonic transducers with the central frequencies 1.0 MHz, 3.0 MHz and 5.0 MHz. The measurement results demonstrate dependences of the measured ultrasonic properties on frequency. It was determined that the velocity of ultrasonic longitudinal waves varies from 2030 m/s to 2060 m/s when the frequency is changing from 1.0 MHz to 3.5 MHz. The attenuation of ultrasonic longitudinal waves in the same range of frequencies varies from 0.3 dB/mm up to 1.5 dB/mm.