Natural Resources Research Institute Technical Report

Prepared for: USDA Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI 53705Existing log grading procedures in the United States make only visual assessments of log quality. These procedures do not incorporate estimates of the modulus of elasticity (MOE) oflogs. It is questionable whether the visual grading procedures currently used for logs adequately assess the potential quality of structural products manufactured from them, especially those in which MOE is of primary concern. The purpose of this study was to investigate the use of stress wave nondestructive evaluation (NDE) techniques to sort red maple logs for the potential quality of lumber obtained from them. Twenty red maple logs were nondestructively evaluated using longitudinal stress wave techniques and sorted into four stress wave grades. The logs were then sawn into lumber. Finally, the lumber specimens were dried and graded a final time using longitudinal stress wave techniques. The results of this study showed that good relationships existed between stress wave times measured in logs and the lumber produced from the logs. It was found that log stress wave grades have a positive relationship with the lumber grades. Logs with high stress wave grades produced high grade lumber. These findings indicate that the longitudinal stress wave technique could be used in sawmills to sort logs/cants for the production of high MOE products.Natural Resources Research Institute, University of Minnesota, Duluth, 5013 Miller Trunk Highway, Duluth, Minnesota 5581