Evaluation of lumber properties by applying stress waves to larch logs grown in Korea.

Even though extensive research has attempted to establish nondestructive evaluation (NDE) techniques for lumber, little effort has focused on NDE of log quality. If an NDE procedure is established for grading and sorting logs, a significant savings of time and money can be realized and potentially valuable wood waste can be reduced. In this study, a stress wave technique was applied to 20 larch logs with diameters of 25 cm to 30 cm to compare the dynamic modulus of elasticity (MOE) of logs to structural properties of 2 by 4 lumber produced from the same logs. Following stress wave tests, the logs were sawn to 2 by 4 lumber and dried to a moisture content of 15 percent. The lumber was tested by various nondestructive testing (NDT) methods to obtain dynamic MOE; next, static MOE and MOR were obtained by static bending tests. Dynamic MOE of a log was calculated from stress wave velocity for the log and compared with dynamic and static MOE and MOR measured for lumber produced from the same log. Stress waves, ultrasonics, and transverse vibration techniques were employed as NDT methods applied to lumber. As a result ofcomparing the dynamic MOE of logs with the static and dynamic MOE and MOR of lumber, a reasonable relationship was found between the nondestructive parameter of logs and the nondestructive and destructive parameters of lumber.