PARABOLIC BEHAVIOR OF THE YOUNG’S MODULI RATIO OF WOOD OBTAINED BY VIBRATION TESTS WITH TIME DURING DRYING
Keywords:bending vibration, longitudinal vibration, temporal change, TGH method, water distribution, Young’s modulus
A method to estimate the water distribution within wood lumber was developed using bending and longitudinal vibration tests. Sitka spruce and Japanese cedar green wood were left inside a controlled environment of 20°C and 65% relative humidity. The bending and longitudinal vibration tests were performed and the Young’s modulus was obtained by each testing method. And then, the temporal changes in the ratio of Young’s modulus based on the bending vibration to that based on the longitudinal vibration were investigated during drying. The ratio of Young’s modulus increased and then decreased with time during drying due to the difference between the Young’s modulus of the outer portion of wood and that of the inner portion. The temporal change in the ratio of Young’s modulus was similar to the estimate using a simple cross-sectional model developed in this study. The bending Young’s modulus calculated using Euler-Bernoulli’s elementary theory could be used instead of that using the Goens-Hearmon regression method based on the Timoshenko theory of bending.
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