Stress-wave nondestructive evaluation of green veneer: Southern yellow pine and Douglas fir

The potential of using stress wave nondestructive evaluation techniques to sort green southern yellow pine and DOuglas fir veneer into stress grades was evaluated. Stress wave nondestructive evaluation was used to separate green veneer into several grades for use in manufacturing engineered wood composites, most notably laminated veneer lumber. The effect of moisture content and preservative treatment on stress wave determined properties of green (wet) southern yellow pine and Douglas fir veneer was investigated during the preliminary stages of the project. A digital oscilloscope and a commercial stress wave timer were used to measure the transit time it took for an induced stress wave to travel the longitudinal length of each veneer. Stress wave transit times were measured in each piece in the wet condition, during drying, and at a dry equilibrated moisture content of approximately 10 percent. Strong correlative relationships exist between stress wave velocity measured in untreated and preservative treated green (wet) and dry veneer.