Stress wave nondestructive evaluation of logs to predict structural product quality

Past nondestructive evaluation (NDE) research efforts have paved the way for the successful use of NDE for determining the quality of finished wood products. However, little effort has been expended on developing NDE techniques for use in grading or sorting logs for internal soundness and structural quality. We recently conducted a study to address this area. This paper describes our study and the results obtained from it. In our study, longitudinal stress wave NDE techniques were used to evaluate the quality of approximately 197 balsam fir and eastern spruce logs prior to processing into lumber. Longitudinal speed-of-sound transmission was used to determine the modulus of elasticity (MOE) for each log. The MOE of each piece of structural lumber cut from the logs was then determined using transverse vibration NDE techniques. A strong relationship was observed between the MOE of the logs and the lumber obtained from the logs.