Abstract:Quality assessment of hardwood log can provide the best usage value of broad-leaved wood resources for industry, but a low-cost, convenient and fast method to evaluate quality of hardwood log is a serious challenge. Here, a quality evaluation method based on impact stress wave testing was proposed. The moment analysis and wavelet transform were used to extract two acoustic evaluation parameters of time centroid and damping ratio, and derive the extraction process of damping ratio based on the continuous wavelet transform in detail. The proposed method was applied to classify samples of hardwood log. The cutting results of log boards showed that for log quality’s predicted grade results based on time centroid and damping ratio, respectively, in high quality log groups, high-grade boards occupancies are 74.2% and 74.0%, respectively, while low-grade boards occupancies are 3.2% and 3.3%, respectively; however, in low-quality log groups, high-grade boards occupancies are 21.8% and 28.5%, respectively, while low-grade boards occupancies are 11.2% and 8.3%, respectively; compared with log quality’s predicted grade results according to the traditional acoustic velocity, in high quality log groups, high-grade boards occupancy is increased by about 26%, while in low-quality log groups, high-grade boards occupancy is decreased by more than 15%; in view of the variability of wood and the diversity of hardwood defects, comprehensively considering the predicted grade results according to various parameters may be the best choice.
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