Characterization of tangential shrinkage stresses of wood during drying under superheated steam above 100 °C

Document Type

Article

Publication Date

11-1-2007

Abstract

The characteristics of tangential stresses experienced by Japanese sugi (Cryptomeria japonica D. Don) during drying under superheated steam with high temperature and pressure were examined in this study. A load cell capable of operating under high temperature and pressure inside an autoclave was used to measure the shrinkage stresses of water-saturated specimens under various drying conditions. The results showed that significant shrinkage stresses occurred even at 100 percent relative humidity (RH), probably due to decomposition and/or modification of wood components. The relationships between tangential shrinkage stresses and moisture content change at various RHs from high-temperature saturated steam drying were significantly different from those of the radial stresses reported in an early study. The occurrence of these stresses had a strong effect on the overall stress development during wood drying under high RH conditions. The shrinkage stresses were significantly reduced by pretreatment using high-temperature saturated steam to prevent drying defects such as surface checks. The occurrence of shrinkage stresses were also effectively restrained by drying under high-temperature steam. The study showed that temperature and RH level had no direct effect on the maximum tangential shrinkage stresses for drying wood above 20 percent RH and within 160 to 180°C. © Forest Products Society 2007.

Publication Source (Journal or Book title)

Forest Products Journal

First Page

39

Last Page

43

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