Application of an ultrasonic wave propagation field in the quantitative identification of cavity defect of log disc

• Ultrasonic propagation field was introduced and verified through experiments.
• Propagation paths on cavity log cross-section were simulated though isolines.
• Internal cavity was identified by overlapping ultrasonic wave fields.
• Location and size of cavity was effectively determined in a high accuracy.

This study introduced the concept of the ultrasonic propagation field in wood and verified its applicability through experiments conducted on a log disc. A green Betula costata log section was used in the ultrasonic propagation measurements. An ultrasonic wave detector (RSM-SY5) was used to measure the ultrasonic propagation time (UPT) on the cross section of the log sample. After the ultrasonication was completed on the non-defective log, five man-made cavities with diameters of 4, 8, 12, 16 and 20 cm were made sequentially in the heart of the same log and utilized in the ultrasonic test. The even UPT values were then approximately outlined as isolines. Based on the UPT isolines, the ultrasonic propagation field in the log disc was simulated using MATLAB software, and the cavity was identified by overlapping the ultrasonic wave fields from different directions. The size of the cavity defect was proven to be effectively determined by overlying the maps of the ultrasonic wave propagation field through a cross section of the wood. The results indicated that the accuracy of detection values for cavity sizes with diameters of 4, 8, 12, 16 and 20 cm were 83.2%, 84.8%, 94.0%, 95.8% and 96.2%, respectively.