Monitoring the natural drying process of felled sugi trees by measuring the stress wave propagation time
2017
Kiribayashi, M. (Tottori Prefecture Forestry Research Center (Japan)) | Fujimoto, T.
The sugi (Cryptomeria japonica) tree, which is native to Japan, is an excellent source of timber ; however, its water content is high and it must be dried, often via kiln drying, prior to use. The 'Hagarashi' (natural drying) is a traditional method in which timber is allowed to dry naturally after felling. Unfortunately, there are no methods with which to nondestructively measure the change in water content during the drying process. However, there is a strong, significant correlation between the weight of logs during drying and the stress wave propagation time (SPT). Thus, in this study, we measured the SPT of felled sugi trees during natural drying. We found that the SPT decreased rapidly for approximately 2 months after felling and then it reached equilibrium. Furthermore, the water content of the felled trees declined for approximately 2 months, and then it became stable. Our results demonstrate that one can nondestructively determine the water content of sugi logs by measuring the SPT.
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