Acoustic tomography for decay detection in red oak trees
USDA, Forest Service, Forest Products Laboratory, 2007 - Medical - 7 pages
The science of tree stability analysis uses both biological and engineering principles in attempting to rate a tree's structural soundness and make reasonable predictions of potential for failure. In such analysis, arborists are often challenged by internal structural defects hidden from view within the trunks. This paper reports the results of an investigation using acoustic tomography to detect internal decay in park trees. Two century-old red oak (Quercus rubra) trees located at the Capitol Park in Madison, Wisconsin, were nondestructively evaluated using an acoustic tomography technique. The trees were subsequently felled, and a disk at each test location was obtained and examined. We found that the light-colored zones in the tomograms were larger than the true decay present in the disks. The oversized light-colored areas were the composite effects of both decay and large internal cracks. The results of this study demonstrated that acoustic tomography cannot distinguish between large internal cracks and heartwood decay. To make a better assessment of internal condition for urban trees, resistance microdrilling should also be used prior to tree removal.
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100-cm elevation acoustic tomograms Acoustic tomography techniques acoustic velocities adjacent sensors Allison arborists bulging ribs century-old red oak cm tree 123 colored zones Comparison of acoustic cracks and heartwood decay and cracks decay areas presented decay detection decay zones shown detect internal decay disk distance between adjacent dominating defects eleva extensive heartwood decay Figure Forest Products Laboratory fungal conks fungal growth extending geometry Gilbert and Smiley half tomograms combined inspection and resistance large internal cracks light-colored decay zones light-colored zones number oak tree 123 oak tree 307 oak trees tested park trees PiCUS Q70 software PiCUS Sonic Tomograph red oak trees resistance microdrilling Resistance profile ribs and cracks Root collar sapwood Sensor arrangement sensors were measured snake crack south side stress-wave three elevations three-dimensional tomogram tomogram taken tomograms with photographs tree trunk trunk at 100-cm two-dimensional tomogram ultrasonic upper cross section urban trees visual inspection Wang Wisconsin wood decay