Résumé
Ultrasounds overestimate the MOE value. This paper analyses the causes of this difference and opens the perspective for a novel method allowing the calculation of the correct MOE from ultrasounds or NIRS measurements on cores.
Standardized methods for determining wood modulus of elasticity (MOE) are destructive and require many replicates. Other methods such as NIRS and ultrasound have been developed to characterize wood properties and overcome these constraints.
The aim of this study was to compare the two MOE measurement methods (NIRS and ultrasound) applied to cores of wood taken from standing trees (Liquidambar styraciflua).
MOE, measured by an acoustic method in standard samples (360 x 20 x 20 mm), was used as a reference. Then MOE was predicted by an NIRS model and determined using ultrasound in standard samples (360 x 20 x 20 mm), small samples (10 x 20 x 20 mm), and cores (15 mm in diameter).
MOE values determined by acoustic method on standard samples and by ultrasonic method on small samples were correlated (R (2) = 0.72) and were not statistically different. The NIRS PLS regression yielded a model with R (2) (cv) = 0.80. The link between NIRS and ultrasound on cores was statistically significant (R (2) = 0.68).
The ultrasonic technique determines an apparent modulus enables comparative data analysis. This apparent modulus can be used for quantitative analysis if a corrective model is used. A correction formula to ultrasonic MOE was proposed in the case of a prismatic geometry.