• The capability of application of fl exural vibration test in nondestructive evaluation of wood drying was studied. Poplar timbers were conventionally kiln dried under three different drying schedules down to the
Inhomogeneities in wood and wood products are evident. Sometimes these inhomogeneities are combined with other inhomogeneities such as drilling. Each can have different effects on dynamic properties, and these footprints can cause hidden defects in wood and wood products. In this research, the effects of artificial inhomogeneity of density and drilling diameters (1 mm, 3 mm, 5 mm, and 10 mm) on dynamic properties of the beams produced from oak wood jointed with poplar blocks (one at the end and the other at the central part of the beam) were investigated. Free vibration on a free-free beam test was subjected for the evaluations. The results indicated that factors such as dynamic modulus of elasticity, acoustic coefficients, and damping capacity, were affected by both inhomogeneity and drillings. The acoustical converting efficiency showed the exact location of inhomogeneity. It also showed the level of drilling diameter.
The determination of the shear dynamic modulus in wood product panels is of greater importance than its determination in wood beams. Yet with regards to the effect of defects on the obtained values of shear modulus, this factor is used to detect the defects and the degree of the defects. In this study, the effect of gluing defects in two joint shapes (scarf (45°) and finger joints (10 mm length and 3 mm pitch) were evaluated non-destructively using the torsional vibration method. Rectangular wood specimens with dimensions of 20 mm × 40 mm × 360 mm (R × T × L) were prepared from clear eastern beech. The joints were located at similar positions in the middle of the beams. The results showed that creating a healthy joint did not significantly change the values obtained for the shear modulus in either of the joint shapes. However, reducing the adhesion level in both types of joints caused a significant reduction in the shear modulus values. The results show that the changes in the dynamic shear modulus values in both joint types, as a result of changes in the glue coverage rating (fully, medium and low-glued joints) allows the detection of the defects as well as the degree of the defects.
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