EVALUATION OF WOOD QUALITY OF PINUS MONTEZUMAE LAMB. IN A DISTURBED FOREST USING NON-DESTRUCTIVE ACOUSTIC METHODS

The objective of this study was to evaluate the modulus of elasticity and wood quality for structural use in standing trees of Pinus montezumae Lamb. in a natural forest. An acoustic method was used, measuring the ultrasonic flight time for one cross-sectional and two longitudinal sections in 70 trees. Significant differences were found between the two longitudinal moduli of elasticity, and the P. montezumae trees in the study area show potential for structural use according to the modulus of elasticity. It is concluded that for sustainable management, wood of medium quality would be obtained in the same proportion for the first two sections of the tree stems, while high-quality logs would be obtained in the second longitudinal section (2–4 m)

Prediction of bending properties for some softwood species grown in Turkey using ultrasound

Ultrasound has been used in prediction of bending properties for some important wood species grown in Turkey including Calabrian pine, Anatolian black pine, Cedar and Oriental Spruce. Sound velocities of small clear wood specimens were determined using EPOCH 650 ultrasonic flaw detector with 2.25 MHz contact longitudinal transducers at constant moisture content. Following non-destructive measurements, specimens were subjected to three point bending tests. The measured average sound velocities for species tested in L directions were ranged from 4510 to 5254 m∙s-1. Although spruce had the lowest density (425 kg∙m-3), it had the highest sound velocity. The predicted average dynamic modulus of elasticity (Edyn) values for the species tested varied from 10137 to 12856 N∙mm-2. The correlation coefficients between Edyn values and MOE values were higher than those between Edyn and MOR. Edyn values are higher than calculated MOE values. The correlation coefficient between predicted Edyn and calculated MOE values ranged from 0.81 to 0.89. The correlation coefficient between Edyn and MOR varied from 0.78 to 0.88 for the species tested. Results indicated that there was no certain relationship between the density and wave velocity except Calabrian pine which showed negative weak correlation. MOE is better indicator of MOR than Edyn as expected.

Water distribution during ultrasound-assisted vacuum drying of wood

Wood ultrasound drying is an innovation method, it can reduce overall drying time, increase the mass transfer rate, and increase the effective water diffusivity. In this paper, poplar was taken as experimental material. The drying process was carried out under the conditions that the drying medium temperature is 60°C, the absolute pressure is 0.02 MPa, the ultrasound power is 100 W and the ultrasound frequency is 20 kHz. The moisture content distribution and water diffusion coefficient were studied, and the model among wood moisture content variation, drying time and water diffusion coefficient was established. Results indicated that the moisture gradient increases along with the increase of drying time during the drying process, free water and bound water are dried simultaneously when wood moisture content is above the fiber saturation point; Wood moisture decreased linearly when moisture is above the fiber saturation point, while the descending rate decreases when the moisture content is below the fiber saturation point. The water diffusion coefficient decreases along with the increase of drying time and increases exponentially along with the increase of moisture content. The moisture diffusion coefficient is 2.89×10-4 at the beginning stage, it is 3.02×10-6 when the moisture content is at the fiber saturation point, and it is 2.27×10-7 cm2.s-1 when the moisture content is 10 %; The equation between the water diffusion coefficient and the moisture content was established and it could be used to predict the water diffusion coefficient during ultrasound-assisted vacuum drying.

Physico-acoustic characteristics of spruce and larche wood

This study deals with non-destructive measurement of wood, i.e. physico-acoustic characteristics (density, dynamic modulus of elasticity, acoustical constant, speed of sound propagation in material and logarithmic dumping decrement). We used two species spruce and larch for measurements. We took wood from two main areas: from Slovakian higher latitudes and from Russia – Siberian areas. Spruce is the main species for the boards of musical instruments and we tried to find another species to replace this one. We measured physico-acoustic properties by two devices: The ultra-sonic tester and device “MEARFA” based on searching correct frequency for each sample. The results show that spruce for top instruments has acoustic constant approx. 12 m4∙kg-1∙s-1 and the “best” value for larch was approx. 10 m4∙kg-1∙s-1. If we compare the methods of measurement of the sound velocity through samples the results for ultrasonic testing are much higher than those provided by resonance-dynamic method. The article also describes differences between physico-acoustical characteristics of sap wood and heart wood, and differences between species.

Moisture dependent elastic constants of particleboard layers by ultrasound and compression tests

Elastic constants of particleboard layers were investigated using by means of ultrasonic waves and compression tests under different humidity regimes. Three Young’s modulus, three shear modulus and six Poisson ratios were determined. Three longitudinal and six shear wave velocities propagating along the principal axes of anisotropy, and additionally, three quasi-shear wave velocities at 45° angle with respect to the main axes of anisotropy were measured. Compression tests were also conducted in order to measure the accuracy of ultrasonic method. Comparing with calculated values, the predicted Young’s modulus values in the principle directions are acceptable. The shear values calculated using ultrasonic method are higher than those determined from compression tests, particularly in the perpendicular directions. Some of the Poisson’s ratios predicted by ultrasound seem to be extreme. The influence of moisture content on Poisson’s ratios is variable. It can be concluded that ultrasonic method can be used as alternative in determination of elastic modulus for particleboard layers at different moisture conditions. The accuracy of ultrasound for determining the Poisson’s ratios of particleboard layers is questionable.