Evaluation of the internal decay of the Quercus castaneifolia Tree through the non - destructive test procedure of the acoustic tomography

Acoustic tomography technology is a non-destructive method that can reveal the hidden defects of trees. As a result, the aim of this study is to detect the internal defects of the oak tree (Quercus castaneifolia) using acoustic tomography. For this purpose, samples were randomly prepared from ten trees in the Asalem region of Gilan province and then discs were cut from trunks. Doe to the lack of natural decay, artificial cavities were drilled inside the disks in four stages: 25% - 50% - 75% - 100%.  Healthy and defective samples were obtained and the sound wave velocity was calculated using FAKOPP Microsecond Timer device. The results show that the average speed of sound waves passing through the oak wood is 1500 meters per second, which decreases greatly with increasing internal defects. If internal decay progresses from 25% to 100%, the amount of reduction in the speed of sound waves varies from 15% to 36%. The size of the crack or shake is also effective in reducing the speed of sound waves. In large shakes, the speed of waves was reduced by more than 50%. The speed of waves is different in the sapwood and the heartwood. Tomographic images are green in the healthy parts, yellow in the primary decay, and orange and red in the decay, and blue in the cavity parts. Generally, The Acoustic Tomograph accurately revealed the presence and magnitude of the defect without differentiating between decay and crack.