Non-destructive measurement of spiral grain with computed tomography

Abstract: Spiral grain is a wood feature that is formed in the living tree. Timbers sawn from trees with severe spiral grain have a great tendency to twist when the moisture content changes. This is a big problem in the wood products manufacturing process. Some of these problems could be avoided if the magnitude of the spiral grain angle could be measured early in the manufacturing process and logs with severe spiral grain sorted out. However, a non-destructive method for measurement of spiral grain in logs is lacking both for industrial purposes and for research purposes. The main objective of this work was to develop and evaluate a non-destructive method for measurement of spiral grain in logs for research purposes and to analyse if there are any possibilities to develop a method that can be used in the industry. Computed Tomography (CT) has been used for non-destructive measurement of spiral grain in this work. The CT-method has been compared with the destructive Splitting method. The most important conclusions of the work presented in this thesis are: CT-scanning is a powerful new research tool for non-destructive measurement of spiral grain in logs. The CT-method for spiral grain measurement works both for Scots pine and for Norway spruce. Attempts to model and predict the magnitude of the spiral grain angle have shown that it might be possible to measure spiral grain with an industrial X-ray LogScanner in the future. It is very efficient to use data from the Stem Bank databases for test and analyses of different measurement methods.