Effect of solid couplants made of hydrophilic polymers in ultrasonic testing

Çetin, Mustafa İlker
This thesis investigates the effect of hydrophilic polymers as novel solid couplants in ultrasonic inspection. These polymers can absorb large quantities of water, thus become soft and flexible, and also adapt themselves very well to applications. In this study, experiments were carried out by preparing three different types of polymer membranes namely [Poly(HEMA), Poly(HEMA-co-GMA), Poly(HEMA-NN'-dH2O)] with different thicknesses and monomer contents. Swelling ratios were determined in deionized water using 9mm diameter samples, cut from each polymer. Ultrasonic velocity and sound attenuation measurements were performed with pulse-echo and immersion techniques. These results were analyzed and compared with water, typical plastics and rubbers. In order to evaluate the coupling performance of hydrophilic polymers, weights of 50g, 200g, 500g and 1 kg were used as loading conditions to change the pressure applied to the transducer. Results obtained with this study showed that hydrophilic polymers offer low attenuation at high frequencies and couple effectively while eliminating the risk of test piece contamination. The study also revealed that velocities of polymers decrease by increasing the water content. This research can be used as a guideline for an alternative choice of couplant while testing water sensitive materials in safety critical structures or where the test piece is avoided from contamination and also can be used for rough surfaces.


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Citation Formats
M. İ. Çetin, “Effect of solid couplants made of hydrophilic polymers in ultrasonic testing,” M.S. - Master of Science, Middle East Technical University, 2003.