원통형 대나무의 균열 방지를 위한 열처리

The Heat Treatment of Cylindrical Bamboo for a Prevention of Cracking

Abstract: In this study it was suggested a heat treatment of a cylindrical bamboo to prevent from cracking accompanied drying. Theoretical evaluation for the changes of the strain and the residual stress arisen from drying showed that cracking could be produced due to the difference of strains between the inner and outer surfaces and would be harder at a high temperature than at a low temperature because a plastic accommodation would be significant at a high temper-ature whereas it would be negligible at a low temperature. In addition, it was known that if crack was not found during cooling and very early time after heat treatment (high temperature drying) crack would not be produced thereafter. In order to conform these theoretical pre-dictions the heat treatments of cylindrical bamboos were carried out at 200°C for 0.5~3 hours and the heat treated and the untreated were kept at 60°C to see crack formation. As the result, the heat treated bamboos were not cracked whereas all of the untreated were cracked. The changes of the artificial cracks formed after heat treatment showed that the compressive residual stress was produced by absorption of moisture from air on the outer surface of bamboo 5 days after the heat treatment.