Nondestructive evaluation of veneer quality using acoustic wave measurements

Two nondestructive evaluation methods, impact-induced stress wave techniques and ultrasonics, were investigated to detect lathe checks and knots in veneer, which were identified as key veneer quality properties for some engineered applications. Measurements included wave velocity and attenuation in the directions parallel and perpendicular to the grain. The results showed that both techniques were sensitive to lathe checks when using wave propagation perpendicular to grain. For wave transmission parallel to grain, signals showed some sensitivity to knots. There was no significant difference in wave velocity measurements between stress wave and ultrasonic techniques. Regression models based on stress wave velocities in these two orthogonal directions were developed to estimate the veneer quality index giving a coefficient of determination ranging between 0.39 and 0.50.