2022 Volume 68 Issue 3 Pages 124-131
For the purpose of developing a simple strength grade prediction method for lumber products at the log stage, the effectiveness of strength grade prediction for lumber products (lamina) by determining the strength grade of logs using estimated density for logs produced in Kyoto Prefecture was verified. The cost of determining the strength grade of logs at the mountain site was also verified. As a result, when the estimated density was used to determine the strength grade of logs, the appearance rate of lamina for each strength grade was not much different from that when the measured density was used. In addition, by selecting logs with a dynamic Young's modulus of 9 GPa or more, the appearance rate of L100 lamina increased 1.6 times, confirming the effectiveness of strength grade classification at the log stage in lamina production. Although the purchase unit price of logs increases due to the strength measurement cost, the logs whose strength grade are determined can be selectively purchased. As a result, the total purchase cost of the logs can be reduced by about 30% compared to the case where the strength grade is not determined. From the above, it can be judged that the strength grading of logs using the estimated density is a practical and effective method.
