Relationship Between Log Mechanical Properties And Stress Wave Propagation Parameters

With the annual growth of wood structures, how to test and evaluate the mechanical properties of structure wood more conveniently and efficiently has already become an urgent problem for the workers engaging in the lumber and building materials fields. At present it is constantly increasing that each kind of non-destructive testing technology is used for the research of structure plates'and historic building structure timbers'mechanical properties, however, the relative report for structure logs is rare. In this paper poplar (Populus tomentosa) and larch(Larix gmelinii) logs samples were selected as the objects of study. First evaluated the samples'mechanical properties with stress wave non-destructive instruments, and then obtained the samples'static mechanical properties by intelligent mechanics testing machine, finally analyzed the experimental data through the statistical analysis software and acquired the correlation between logs'mechanical properties and stress wave propagation parameters. The results indicated that:In the poplar and larch log samplings the stress wave radial velocity was much less than the longitudinal; in addition the radial velocity had a linear correlativity both with the velocity of longitudinal heartwood and with the sapwood. The stress wave tangential velocity also had a remarkable quadratic function relationship with the detection angles, moreover the maximum value both appeared in the position of 1/2Ï€, meanwhile the minimum value separately appeared in the position of both sides'1/8Ï€and 7/8Ï€. The stress wave longitudinal heartwood and sapwood as well as radial velocity had different correlation with diameter, moisture content and density respectively; however they all had significant correlation with the combined effects of the three factors. The same situation was for the dynamic modulus of elasticity E1, E2 and E3.In the poplar and larch log samplings, there were certain correlations between compressive strength and bending strength, modulus of elasticity in compression and modulus of elasticity in bending, but they were not very remarkable. In larch log samplings there was the most remarkable correlation between E2 and compression strength. In the two log samplings, bending strength and modulus of elasticity in bending both had considerable linear correlation with E3; compression strength and modulus of elasticity in compression also both had remarkable linear relationship with E2.