Effect of Finger Joint and Scarf Joint on Ultrasonic Parameters

In this research، nondestructive evaluation of finger and scarf joints manufactured with beech wood were performed using through transmission ultrasonic technique. For this purpose، sound joints were manufactured. Then ultrasonic parameters including ultrasonic wave velocity، coefficient of attenuation، maximum amplitude and root mean squares (RMS) voltage were measured in longitudinal and perpendicular direction of joints. Through- Transmission technique with transducers of 40 kHz was used for all measurements. Results showed that there was no significant different between ultrasonic parameters in perpendicular direction of the specimens with and without joints، however in longitudinal direction، the wood specimens (without joint) exhibited significantly higher ultrasonic velocity. Higher coefficient of attenuation and the lower maximum amplitude and RMS voltage were obtained in longitudinal direction of the specimens with finger joints in comparison with specimens without joint as well as with scarf joints.