ULTRASONIC CHARACTERIZATION OF FORMING FABRICS

Nondestructive ultrasonic testing techniques are applied to characteri ze paper machine forming fabrics. A dry-contact, in-plane ultrasonic m ethod is used to determine the velocity of longitudinal elastic waves propagating along the machine and cross-machine directions of forming fabric specimens. Two out-of-plane ultrasonic techniques, a dry-contac t method and an immersion method, are used to evaluate the velocity an d apparent velocity of thickness-direction longitudinal elastic waves, respectively. Stiffness properties are computed from velocity measure ments. Correlations between known parameters of forming fabrics and re sults gathered in this study are examined.