Surface-checking occurring conditions in air-drying off softwood lumber for construction use.

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This year is the final year for this research. The final research report was published in the form of a booklet. Research results for this year were described as below by referencing the research items 1, 2 and 3 in this year's application of execution.1.Relation between surface-checking and tension strength perpendicular to grain of wood Drying stress was measured by strain gauges along with the width direction of board, which sizes are 10cm in width, 5cm in thickness, and 35cm in length, respectively and the drying stress distribution was found in the width direction as the result. Tension stress was also found in the fiat main dried-board. The board with semi-straight grain has the possibility to occur the compressive stress caused by absorption of moisture besides the tension stress which is the reason of surface checking. However this phenomenon is not clear. So it needs the more correct examination.2.Examination of surface-checking under 0℃ drying condition.This examination could not be accomplished. This remains for the future research.3.Relations between the climate in Japan and surface-checking of lumberThe paper named "Surface checking in air-drying of boxed-heart softwood in Japan" was submitted to Forest. Products Journal, which is an International Journal for Wood Sciences, and is in print.Future subject : Effect of temperature under 0 ℃ and wind velocity on the surface checking remained as the future subject.