Non-destructive Estimation of Young's Modulus for Lumbers in Air Dry Condition from the Stress Wave Measurement at Green Condition

摘要

In this study, it was investigated that the non-destructive estimation method of Young's modulus for full-scale sawn lumber in air dry condition, which is very important index for timber used in wood construction, using stress wave measurement at green condition. Because it was well known that stress wave propagation velocity was strongly influenced by moisture content of wood, in this research, we especially derived the relationship between the moisture content (u) and the rate of change of stress wave propagation velocity (V_u/V_0) by numerical analysis using the experimental data of full-scale lumber of Japanese cedar. Furthermore, the accuracy of this relationship was verified. As a result, using the obtained u - V_u/V_0 relationship, Young's modulus of the full-scale sawn lumber in an air dry condition was estimated with very high precision; for experimental data of ρV~2 and MOE, the estimation accuracies were 1.01±0.10 and 1.14±0.12 respectively.