Modeling Shrinkage Response to Tensile Stresses in Wood Drying III. Stress—Tensile Set Correlation in Short Pieces of Lumber

Abstract

This article reports on the correlation between tensile stresses, temperature, and target moisture content in short pieces of lumber based on relationships developed on experiments made on small wood strips subjected to different types of restraints. Linear motion position sensors were placed around a tested specimen using a frame connected to a support body. A wireless moisture and temperature monitoring system was used to record wood moisture and temperature changes. All measurements were performed perpendicular to fiber grain while drying at 40, 60, and 80°C in an environment set for a target moisture content of 5%; the experiments were stopped when the average moisture content of the lumber was around 10%. High stress values were obtained for specimens dried at 60°C and a low relative humidity, whereas a high reduction in stress level could be obtained for 80°C. The findings are intended to be used in further studies of the shrinkage process as an indicator of the tensile stresses generated in the early stages of wood drying.

Keywords:

• Perpendicular to fiber grain
• Shrinkage
• Tensile stresses
• Western hemlock
• Wood drying

ACKNOWLEDGMENTS

This research was financially supported by a Natural Sciences and Engineering Research Council of Canada CRD grant and by a Research Grant-in-Aid from FP Innovations, Forintek Division.