Effect of Sample Geometry on EMC And Moisture Hysteresis of Red Oak (<i>QUERCUS</i> SP.)
Keywords:
Wood moisture content, drying hysteresis, drying size effect, drying stress, <i>Quercus</i> spAbstract
Past researchers have shown that equilibrium moisture content (EMC) is influenced by mechanical stress. It has also been widely demonstrated that the size effect in drying produces varying amounts of stress. This experiment related the internal stress developed during drying to the EMC of red oak (Quercus sp.) samples. The results indicated that larger pieces, with larger potential differential stresses, had significantly different EMCs than relatively smaller pieces. The influence of sample size on hysteresis ratio was also examined. The difference between the adsorbing and desorbing EMCs increased with sample size. As sample thickness decreased to 50 μm, the hysteresis ratio reached unity. Thus as internal drying stresses were eliminated from the wood, the hysteresis effect was eliminated. This behavior suggests that differential drying stresses and/or strains are a causal agent for the observed moisture hysteresis in wood.References
Barkas, W. W. 1949. The swelling of wood under stress. Gt. Brit. Department of Science Industrial Research in Forest Products Research, London, UK.nLibby, T. B., and J. G. Haygreen. 1967. Moisture content change induced by tensile stress in whole wood. Inst. Wood Sci. J.3(18):54-60.nMason, O., and E. S. Richards. 1906. Proc. Roy. Soc. London. A78, 412. Cited in Stamm, 1964.nSkaar, C. 1972. Water in wood. Syracuse University Press, Syracuse, NY. 218 pp.nSimpson, W. T. 1971. Moisture changes induced in red oak by transverse stress. Wood Fiber3(1): 13-21.nSimpson, W. T. 1991. Dry kiln operators manual. USDA Forest Service. Superintendent of Documents, Washington, DC.nStamm, A. J. 1964. Wood and cellulose science. Ronald Press, New York, NY. 549 pp.n
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