Tensile, Compressive, and Shearing Stresses Developed in Red Oak as It Dries

This analysis applies a mathematical method of calculating internal stresses that develop during drying of wood. It was applied to the initial phase of drying–that preceding the stage of stress reversal–using several red oak boards dried at five temperatures ranging from 80? to 140?F. It is recognized that the patterns of stress developed will depend to a considerable extent on the anatomical and physical characteristics of the boards as well as on other features of drying than dry bulb temperature alone. Some general conclusions were: 1) results agree quite well with previous studies involving recovery strains in that the pattern of stress distribution is generally similar to what might be expected from previous research; 2) the magnitude of stress development at any point on the cross section is affected by the drying temperature through its influence on both drying rate and mechanical behavior of the drying wood; 3) apparently there is a consistent relationship in location and magnitude between tensile and compressive stresses in both the width and thickness directions of the drying board and the associated shearing stresses over the range of drying temperatures considered; and 4) stresses developed in the width direction approach near what would be considered the failure level, especially at the lower drying temperatures. The rate at which severe stresses subside appears to increase with increasing temperature in the temperature range considered.

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