1993 年 42 巻 473 号 p. 141-146
To make the use of timber more efficient, it is considered that the log should be selected based on the structural characteristics before carried into the saw mill, and the log-sawing design should be determined suitable to the wood products in the mill. The natural frequency of longitudinal wave due to sound when hitting cross section of log and lumber was measured to determine the modulus of elasticity (Et). Et was recognized to be highly linear to the modulus of elasticty due to static bending test (Es). The potential application of the relationship between the Et of log and that of sawn lumber and laminae gained from the log was discussed from practical aspect.
As a high correlation between Et of log and structural properties of sawn lumber is recognized, measuring Et of log could be one of the mechanical gradings which would be effective and easy to conduct on site before carrying to the saw mill. Since Et of log practically was presented as the average value of Et of laminae, the design of sawing for laminae should be considered based on the estimated distribution of modulus of elasticity of laminae within log. It could be effective as a rough classification for mechanical grading of lumber and quality control of selecting log for the laminae of glue laminated lumber in the mill.