Vibration method for grading of large cross-section coniferous timber species

Abstract

The non-destructive testing (NDT) of timber using the longitudinal vibration method is based on the natural frequency of wood which is in relation to its quality. In the present paper, the suitability of this tool is investigated and the results of grading 395 pieces are presented. Structural timber of Radiata pine ( Pinus radiata D. Don.), Scots pine ( Pinus sylvestris L.), and Laricio pine [ Pinus nigra ssp. salzmannii (Dunal) Franco] from Spanish sources were investigated. The specimens were tested for bending according to the European standard EN 408 (2003) and the values of strength and stiffness were compared with the results estimated by means of NDT. The vibration equipment applied permits the measurement of the longitudinal natural frequency and mass of the specimen, and then the density and the dynamic modulus of elasticity can be calculated. There is a strong relationship between the static modulus of elasticity obtained from the bending test and the dynamic modulus of elasticity obtained by the NDT technique. There is an acceptable relationship between modulus of rupture and dynamic modulus of elasticity if the visual defects (knot sizes) are taken into account. Acoustic measurements have become widely acceptable, and they have great potential for stress grading of coniferous timber.

Determination of the mechanical properties of radiata pine timber by means of longitudinal and transverse vibration methods

“…Later, the suitability of this tool was tested in a wider set of coniferous species [395 pieces of radiata pine, Scots pine, and Corsican pine (Pinus nigra subsp. laricio)] from Spanish sources, and the great potential for stress grading of coniferous timber was demonstrated in agreement with European Standard EN 14081-2 (2005) (Arriaga et al 2012). The quoted standard specifies requirements for initial-type testing of machine-graded structural timber and for strength grading machines.…”

Influence of moisture content on estimating Young’s modulus of full-scale timber using stress wave velocity

“…For the Young's modulus after drying, comparing the ρ a(o) V a(o) 2 , calculated from density and stress wave propagation velocity and the MOE a(o) , ρV 2 was larger than MOE by 8.3% at the measurement points of pith and by 13.9% at the mature wood, respectively. It is considered that this tendency, which was also observed in the previous study [16], is due to the frequency-dependent (time-dependent) influence of the Young's modulus caused by the viscoelasticity of the timber.…”

Destructive and non-destructive evaluation of seven hardwoods and analysis of data correlation

“…The methods are helpful for rapid testing and grading in practice, especially for high priced logs. Arriaga et al (2012) also observed a strong relationship between MOD stat obtained from bending test and MOD dyn by NDT (longitudinal vibration method applied for three conifer species). Similar correlations were also found in timber grading tests performed in poplar wood samples by Casado et al (2012).…”

“…In the last decades, much attention was paid to the non-destructive evaluation of wood properties, especially with regard to mechanical grading. In this context, non-destructive (NDT) and semi-destructive techniques (SDT) can be differentiated for evaluating wood and woodbased materials, which are useful for the assessment of standing trees or in-place structures (Brashaw et al 2009;Biechele et al 2011;Arriaga et al 2012;Casado et al 2012). These techniques are reasonably good predictors of timber properties under field conditions and detection of decay.…”

“…This equipment is very simple to use on logs and at timber sales outlets. TMT is a good candidate for wood grading (Arriaga et al 2012;Casado et al 2012).…”