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16 September 1999 Methods for detecting compression wood in green and dry conditions
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Proceedings Volume 3826, Polarization and Color Techniques in Industrial Inspection; (1999)
Event: Industrial Lasers and Inspection (EUROPTO Series), 1999, Munich, Germany
The living softwood tree forms compression wood to compensate for external loads during growth, which creates wood fibers with higher longitudinal shrinking and swelling than normal wood at moisture content changes. This is often the cause of undesirable warping of sawn wood products after drying. An automatic detection of severe compression wood is thus useful to reject unwanted pieces. Detection in green condition is often preferred in a sawmill while detection in dry condition is needed in other applications. Three different non- destructive scanning methods were evaluated on both green and dry wood surfaces. The methods used were RGB (red, green, blue) color scanning, tracheid-effect scanning and x-ray scanning. The color and x-ray methods were evaluated on Southern yellow pine lumber, while the tracheid-effect scanning was tested on Norway spruce. For scanning in green condition detection of compression wood was good using the tracheid-effect and color scanning. X-ray scanning was not useful because of the uneven moisture distribution in green lumber. After drying the result changes, tracheid-effect and x-ray scanning have good detection ability while RGB color does not provide sufficient information for reliable detection.
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Jan Nystrom and Olle Hagman "Methods for detecting compression wood in green and dry conditions", Proc. SPIE 3826, Polarization and Color Techniques in Industrial Inspection, (16 September 1999);

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