Physico-chemical indicators of inter-specific variability in vibration damping of wood

Abstract

Abstract• The vibration damping coefficient (tanδ) of wood is an important property for acoustical uses, including musical instruments. Current difficulties in the availability of some of the preferred species call for diversification, but this comes up against the lack of systematic damping coefficient data.• Keeping in mind the possible factors affecting tanδ, could we predict its variations between species, by using indicators that are either easily measured and/or readily available for many species?• Vibrational properties, equilibrium moisture content and colorimetric parameters were assessed on 94 wood types belonging to 76 species. Experimental results were then related to data on chemical contents and physical properties from the CIRAD database. The "standard" relationship between tanδ and specific modulus of elasticity (E'/ρ) explained only half of the variations. Deviations from this trend were correlated to extractives content, yet effects were not directly quantitative. Damping deviations were also correlated to colour and moisture-related properties, especially so with fibre saturation point.• By taking into account a combination of moisture-related properties, colour -or extractives content, and the "standard" relationship between tanδ and E'/ρ, we could propose simple predictive models which explain up to 89% of observed variations in tanδ between 48 species.

Caractéristiques Biophysiques Du Bois De Pterocarpus Erinaceus (Poir.) en Zones Guinéenne Et Soudanienne Au Togo

“…La présence d'un taux d'extrait plus fort dans la zone centrale du tronc pourrait expliquer ce résultat ; cela concorde avec les résultats de Brémaud (2006) qui a montré l'influence du taux d'extrait notamment à l'alcool benzène sur le PSF (Brémaud et al, 2010). On note une très faible diminution de la densité en fonction de l'âge (R² = 0,11), ce qui est intéressant au plan technologique.…”

“…Ces résultats concordent avec ceux de Brémaud (2006) qui a travaillé sur différentes espèces tropicales utilisées pour la réalisation de xylophones (Brémaud et al, 2010). Par ailleurs, le PSF influe positivement sur les retraits tangentiel, radial et surfacique avec un effet plus marqué suivant la direction tangentielle (tableau III).…”

Radial variations of vibrational properties of three tropical woods

“…The damping coefficient, tanδ, is representative of the wood dissipative behavior. These properties were measured by free-free flexural vibration method (Hearmon, 1958), using an apparatus previously described (Brémaud et al, 2009;Brémaud et al, 2010c). E'/ρ was calculated from the resonance frequency of the first vibration mode based on EulerBernoulli beam theory such as,…”

“…8 Principle of the interpretation of log(tanδ) -log(E'/ρ) diagrams used by several authors Based on this hypothesis, wood specimens can be regrouped according to the difference between experimental tanδ and "standard" one predicted by equation (2), assuming that that these new groups should actually reflect the dependence of damping coefficient on the chemistry of matrix. Distances to "standard relation" (DSR) were previously found to be correlated to extractives content on 25 tropical hardwoods (Brémaud et al, 2010c) and to be quite good descriptors of species classification (Brémaud et al, 2009). DSR for each group of woods in this study is indicated in Fig.…”

“…These secondary constituents are determinant for some wood properties, such as color and durability. Additionally, they have been shown to influence wood viscoelastic behavior Brémaud et al, 2010a;Brémaud et al, 2010c;Minato et al, 2010), although this effect differs from case to case: some extractives induce a strong decrease of the damping coefficient, while some other slightly increase it (Obataya et al, 1999), and some have limited effect (Sakai et al, 1999).…”