Loveday, PW; Fromme, P; (2024) Measurement of Lamb wave phase velocity using lowcost equipment. In: Hoffmann, J and Venter, MP, (eds.) Proceeding of the 13th South African Conference on Computational and Applied Mechanics, SACAM 2024. (pp. pp. 150-157). South African Association of Theoretical and Applied Mechanics: Mostertsdrif Stellenbosch, South Africa.

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Abstract

Lamb waves are a family of guided ultrasonic waves that propagate in plate structures. The phase velocity is an important characteristic for material characterisation and locating defects in nondestructive testing applications. The phase velocity may be measured by exciting the Lamb wave at one location and then measuring the response at a set of equally spaced points extending radially from the source. These measurements are often performed using a fixed piezoelectric excitation transducer and a non-contact laser vibrometer to measure the response at several points. This research aims to use lowcost equipment to perform these measurements by replacing the laser vibrometer with a moving piezoelectric transducer or electromagnetic acoustic transducer (EMAT). It was previously found that the piezoelectric transducer had limited repeatability, and this is investigated further. An EMAT was developed and compared to the piezoelectric transducer. The EMAT has poor signal to noise ratio and a high number of averages was required. Measurements at a single location showed repeatability similar to the piezoelectric transducer. When the EMAT was moved to a series of measurement positions the performance was not better than that of the piezoelectric transducer and development of a more accurate positioning technique is required.

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