Effect of attached weight on the measurement of the Young’s modulus and loss tangent of solid wood via the free and forced flexural vibration methods

Abstract

The Young’s modulus and loss tangent of a Sitka spruce wood sample in the longitudinal direction were determined using free flexural vibration (FRFV) and forced flexural vibration (FOFV) tests. During the tests, the attached weight and sample length were varied, and their effects on the Young’s modulus and loss tangent of the sample were examined. The Young’s modulus could be accurately and easily obtained from both the FRFV and FOFV tests using a modified Euler-Bernoulli’s equation, with the effect of the attached weight mitigated. No significant difference was observed between the two values of the Young’s modulus obtained from the two tests. The loss tangent slightly increased as the attached weight increased when the ratio of attached weight/sample weight was below 10%; however, it significantly increased with the increase in the attached weight when the ratio of the attached weight/sample weight exceeded 10%. The values of the loss tangent obtained from the FOFV tests for different samples were often higher than the corresponding values obtained from the FRFV tests, whereas the loss tangent values of different samples obtained from the FOFV tests were lower than the corresponding values obtained from the FRFV tests.