Thermographic Measurement of Slope of Grain by Thermal Anisotropy of Wood

When the longitudinal surface of wood is heated within a small circle, it must show an elliptical pattern of temperature rise around the heat source elongated along the grain due to the thermal anisotropy of wood. This implies that the slope of grain could be estimated by a thermographic technique including the thermal stimulation of surfaces and the temperature measurement by an infrared camera. The feasibility of this technique was examined theoretically using finite element method (FEM) and experimentally for wood surfaces heated by a hot cylinder of brass with a diameter of 5 mm.

temperature distribution

Fig.1 Temperature distribution by thermographic measurement
temperature distribution determined by FEM

Fig.2 Temperature distribution determined by FEM
relationship between slope of grain and LS ratio

Fig.3 Relationship between slope of grain and LS ratio

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