Development of stress wave indices for heart-rot detection in teak tree

Heart rots severely degrade tree’s log quality. This study presents a development of stress wave indices which could be helpful for the detection of heart rots in trees with commercial stress wave CT equipment. To determine an accurate index telling sound or decayed wood, two tests were carried out. First, Dissimilarity Index (DI), based on difference in stress wave velocity between the measurements and the reference value on sound wood, was calculated with consideration of difference in velocity according to transducers’ angles. Second, average difference in velocity (ADV) between inner and outer zones of a cross section was calculated. For these two indices, the best method and threshold were determined. The ADV index could distinguish sound and heart-rot discs with high accuracy (89.5–94.7 %). DI did not show satisfactory accuracy in determining the presence of heart rots (63.6 %), but it showed a good feasibility of predicting the size of heart rot. The developed indices were expected to be able to be used as a decision-making criterion for heart-rot detection and a predictor of its sizes in teak trees while using stress wave CT equipment.