COMPARISON OF ELASTIC CONSTANTS OF WOOD DETERMINED BY ULTRASONIC WAVE PROPAGATION AND STATIC COMPRESSION TESTING

摘要

In Brazil, most reports on the elastic properties of wood include only the elastic modulus in the longitudinal direction. This is because of the difficulty in determining other properties through static testing. The purpose of this study was to evaluate the methodology for determining the three Young's moduli (El, Er, Et), the three shear moduli (Glr, Glt. Grt). and the six Poisson ratios (vlr, Vlt, Vrl, Vrt> Vtl> Vtr) using ultrasonic technology. For testing, we used specimens in the form of cubicprisms from the following species: Garapeira (Apuleia leiocarpa), Cupiuba (Goupia glabra), and Sydney Blue gum (Eucalyptus saligna). The ultrasonic tests were performed with plane transducers of longitudinal and transverse waves, both with a 1-MHz frequency. For comparison, the same specimens were tested by static compression. Based on the confidence intervals of the means, the results of the ultrasonic test produced values of longitudinal elasticity moduli (El, Er, and Et) and shear moduli (Gtr, Gtl, and Glr) statistically equivalent to those obtained with static compression. In the case of the Poisson ratio, the results, using the confidence intervals, indicated that Vrl, Vlr, and Vlt were not statistically equivalent to those obtained in static tests for any of the species. Conversely, Vxl, Vtr, and Vrt were statistically equivalent to those obtained in static tests for all the species. In conclusion, the ultrasonic test for determining the Young's and shear moduli of wood was found to be simpler and less expensive than the static compression test, and the results are equally useful.