Application of ultrasonic technology for predicting the final MC of kiln-dried softwoods

Western hemlock and Douglas-fir samples were dried to achieve a wide range of final moisture contents. The parameters related to final moisture content, such as green weight, green moisture content, time of flight (TOF) in green, slope of grain, and basic density, were investigated. For ultrasonic testing, two timers and five pairs of transducers were examined to determine the best combination. Among the evaluated parameters, green weight was the best predictor of final moisture content, although the regression correlation was relatively low. However, correlation was improved when boards were assessed within three grain pattern categories. A two-variable regression model including green weight and TOF showed better correlation with final moisture content than did any of the univariate models. Some multiple regression models with high correlation coefficients were obtained.