Ultrasonic detection of knots, cross grain and bark pockets in wooden pallet parts

Abstract

This study investigates defect detection in wooden pallet parts using ultrasonic scanning. Yellow-poplar (Liriodendron tulipifera, L.) deckboards were scanned using two rolling transducers in a pitch-catch arrangement to detect unsound and sound knots, bark pockets and cross grain. Data were collected, stored, and processed using LabView? software. Six ultrasonic parameters-three involving time-of-flight, two involving ultrasound pulse energy, and one using ultrasound pulse duration-were measured for each defect type. Four of the six parameters were affected by transmission through unsound knot regions. Sound knots also showed decreased values forthe energy-related parameters. All ultrasonic parameters changed sharply for bark pockets. Cross grain also affected ultrasound energy transmission. Small coefficients of variation for repeated measurements indicates that this scanning arrangement is stable and scanning rate has little effect on the measurements. Results indicate that on-line detection of these defects is possible by ultrasonic scanning.

Citation

Kabir, Mohammed F.; Schmoldt, Daniel L.; Schafer, Mark E. 2000. Ultrasonic detection of knots, cross grain and bark pockets in wooden pallet parts. Proceedings, World Conference on Timber Engineering 2000