RELATIONSHIP BETWEEN MOISTURE CONTENT AND ULTRASONIC WAVE SPEED DURING KILN DRYING OF BASSWOOD LUMBER

Ultrasonic wave speed was measured in the longitudinal direction of Basswood on the top and bottom surfaces and center of lumbers during kiln drying in 3 Kiln load programs with final dry bulb of 80oC and different relative humidities. On the surfaces, wave speed decreased rapidly with MC declining from green to FSP, but from FSP down to 7% moisture content wave speed did increased slowly. In the center of lumber, with decreasing MC from green to FSP, wave speed increased slowly, but by reducing MC to 7%, wave speed was rapidly increased. 5% MC, on the three surface of lumber, wave speed had no drastic difference. Results indicated that ultrasonic wave speed and MC of wood show a parabolic relationship. Further, results have shown that measuring ultrasonic wave speed is an appropriate method to control kiln drying program for hardwood lumber