Ultrasonic wave propagation in poly(vinyl alcohol) and articular cartilage
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An ultrasonic nondestructive evaluation (NDE) technique has been developed to characterize the superficial layer of articular cartilage. The technique utilizes the unique properties of surface waves to detect changes in mechanical properties of the surface layer of the test sample. Experiments were performed first on poly(vinyl alcohol) (PVA) hydrogels, a material used to model articular cartilage, to examine repeatability and the ability of wave propagation parameters to reflect changes in material properties. Dynamic shear and compression tests were performed on 20% and 25% PVA by weight hydrogels to examine the difference in material properties. Ultrasonic NDE tests with longitudinal, shear and surface waves were performed on the hydrogels. Wave speeds in the 20% and 25% hydrogels were compared. Results showed that ultrasonic NDE with surface waves was repeatable and the technique was able to detect material property changes in hydrogels. Ultrasonic NDE tests with surface waves were then performed on healthy and damaged bovine articular cartilage. Wave speeds in the healthy cartilage were compared to speeds in enzymatically digested cartilage. Results showed that ultrasonic NDE with surface waves was repeatable and the technique was able to detect material property changes in the superficial layer of articular cartilage. Findings suggest that the technique has potential to be a tool in diagnosing diseases involving cartilage degeneration, such as osteoarthritis.