Ultrasonic inspection and analysis techniques in green and dried lumber

Abstract

Ultrasonic inspection of lumber has been under investigation for over 20 years, with little commercial impact. Recently, the USDA Forest Products Laboratory (FPL) developed ultrasound-based scanning technology to examine both green and dried lumber. In green lumber, the bacterial infection called wetwood (a significant source of degradation in oak at the kiln-drying stage) was found with high accuracy using time-of-flight techniques. A similar approach was used to locate checking and honeycombing in dried lumber, defects that are often not apparent by external visual inspection. This technology has been licensed and is now being developed for commercial use by the Perceptron Inc., Ultrasound Technology Group, whose specialty is ultrasonic systems and signal processing. The current phase of the project involves a flexible testbed system that can: accommodate a wide range of lumber specimens; permit automated ultrasonic inspection; and account for the specimen’s width and thickness. The inspection provides complete sampling of the ultrasound waveform, so several different signal-processing strategies may be examined beyond the time-of-flight approach commonly used. Special display software allows the user to plot several analysis parameters as a function of position along the length of the specimen. A set of novel signal criteria indicative of different conditions within the wood specimens has been developed. This paper describes the design of the system and its unique features, the unique analysis approach, and results obtained to date.

Citation

Schafer, Mark E.; Ross, Robert J.; Brashaw, Brian K.; Adams, Roy D. 1999. Ultrasonic inspection and analysis techniques in green and dried lumber. Proceedings of the Eleventh International Symposium on Nondestructive Testing of Wood : September 9-11, 1998, Madison, Wisconsin. Madison, WI : USDA Forest Products Laboratory, 1999: pages 95-102.