Various Factors and Propagation Trends of Stress Waves in Cross Sections of Euphrates Poplar

Abstract

Various factors and propagation trends of stress waves in cross sections of wood need study to improve accuracy in the quality evaluation of wood and decay detection in standing trees. In this study, a Fakopp Microsecond Timer was used to measure the stress wave transmission time of Euphrates poplar (Populus euphratica Oliv.). Velocity was calculated to find the trend and make wavefront maps of stress waves. Results indicated that stress waves travel fastest in the radial direction and that velocity decreased as the angle between the two sensors increased. Velocity also increased as the number of annual rings increased. At the same time, the velocity in normal wood was higher than it was in tension wood, and it gradually increased in normal wood as the radial distance increased from pith to bark. Different influences on the stress wave propagation in wood were found when holes were made in the center of a cross section. Velocity showed little change with the increase in hole diameter when the angle between impacting and receiving sensors was 90°. At 180°, velocity was affected by hole diameter and rapidly decreased. Successful simulated wavefront maps of stress waves in cross sections of sound, hole, crack, and decay wood using two-dimensional contours were made. Three-dimensional maps were also reconstructed using Kriging interpolation and showed high similarity between cross sections.

The agreement in accuracy between tomograms, resistograms, and the actual condition of the wood from lime trees harvested from cities

“…Compared to all the other low values of the speeds, sometimes they have nothing to do with internal defects, as the wood is healthy. However, in the tangential direction, the propagation velocities are lower than those on the radial direction (Beldeanu 2008;Lin et al 2008;Kazemi et al 2009;Liang et al 2010;Feng et al 2014). In addition, the sections in which these values were recorded have an oval shape, which further supports the claims that the propagation velocities are closely related to the anatomical structure of the wood (Feng et al 2014;Alves et al 2015) and that an uneven width of the annual rings influences the density of the wood (Filipovici 1964;Sandoz and Lorin 1996;Beldeanu 2008).…”

Stress wave velocity patterns in the longitudinal–radial plane of trees for defect diagnosis

“…, where  is the ray angle, represents the azimuth of the v radial direction relative to the axis of the coordinate system, and  specifies the degree of anisotropy. Liang et al (2010) showed that stress waves traveled fastest in radial direction and that velocity decreased as the wave propagation path shifted toward to tangential direction. Velocity also increased as the number of annual rings increased.…”