Temporal Change in Surface-strain Distribution of Sugi (Cryptomeria japonica) Square Timber during High-Temperature Drying

In this study, the surface-strain distribution behavior of sugi (Cryptomeria japonica) square timber under high-temperature drying was determined. The surface-strain distribution was measured using the mark-tracking method, which is an image analysis technique. Boxed-heart and pithless timbers with a cross-sectional dimension of 132 mm × 132 mm were dried under three types of drying condition. In each condition, the values of surface strain at the center of the timber were higher than those at the edge. This tendency was remarkable in the case of high-temperature drying of boxed-heart timber. The surface drying set, which was measured after drying, showed a positive correlation to the surface strain. This indicated that the surface strain could be used to rough estimation of the amount of the drying set under kiln drying. By measuring the surface-strain distribution using the image analysis technique, the temporal change in the surface strain during the high-temperature drying was clarified in detail.