Measurement of strain distributions in white oak boards during drying using a digital image correlation method

To understand the optical measurement and digital image correlation (DIC) visualization of strain distribution during wood drying and to optimize wood drying schedules, the drying behaviors of white oak specimens, a refractory species, were investigated using an optical measurement system and a DIC method. White oak specimens were dried in a climate chamber, which was modified to be similar to a drying kiln. Strain distribution on the cross-sectional surface of the wood during drying was successfully visualized, and the position and timing of the stress reversals were detected. From the comparison of the strain distributions between mild and severe drying conditions, it was determined that the Theological deformation of wood under mild drying conditions is much more severe than under severe drying condition as the mild case required more time to dry. These results could be used in the development of a new drying schedule or for optimizing an existing drying schedule.