Measurement of Wood Vibrational Properties by the Central Exciting Method

The vibrational properties of wood are determined by the free-free flexural vibration or cantilever vibration methods. On the other hand, for damping materials, these properties are generally determined by the central exciting method. The central exciting method is rarely used for wood. In the present study, we measured the dynamic Young’s modulus (E′) and the loss tangent (tanδ) for the same Sitka spruce specimens by the central exciting (JIS-certificated apparatus), the free-free flexural vibration and the cantilever vibration methods, and compared the results from the perspective of the fixed condition, vibrational modes and other aspects. A simplified experimental apparatus for measurement using the central exciting method was also designed and constructed. The simplified experimental apparatus and JIS-certificated apparatus were verified by measured values (E′ and tanδ). Measured values obtained by the simplified apparatus closely matched those obtained by the JIScertificated apparatus. The E′ values obtained by the central exciting method closely matched those obtained by the free-free flexural vibration method. The tanδ values obtained by the central exciting method were higher than those obtained by the free-free flexural vibration method but close to those obtained by the cantilever vibration method.