Ultrasonic Characterization of Horizontal Density Variations in Oriented Strandboard1

Random flake deposition in mat forming of oriented strandboard (OSB) results in inherent horizontal density variation that affects the panel strength quality. In this paper, a silicon gel coupled ultrasonic transmission (UT) was used to locate, map, and validate the horizontal density distribution in laboratory-made OSB. Two test boards were manufactured at each of three nominal density (ND) and three resin content (RC) levels. The UT variables velocity, attenuation, and root mean square voltage formed excellent complementary predictors of density for all RC and panel types. Based on the allowable 610% variation in the average measured densities, both the general and polynomial models provided improved density prediction for boards at higher RC and ND levels. Using the contour and out-of-limits plots, the predicted horizontal densities gave a reasonable spatial approximation to the measured densities. All 6% RC panels with densities of 0.60 g/cm3 or greater conformed well to the limits, with declining conformity towards the lower RC panels.