Growth layer and fibre orientation around knots in Norway spruce: a laboratory investigation
Growth layer and fibre orientation around knots in Norway spruce: a laboratory investigation
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挪威云杉节周围的生长层和纤维方向：实验室研究
DOI：
10.1007/s00226-017-0952-3
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发表时间：
2017
影响因子：
3.4
通讯作者：
H. Säll
中科院分区：
文献类型：
--
作者：
M. Hu;Andreas Briggert;A. Olsson;M. Johansson;J. Oscarsson;H. Säll
结构木材的强度在很大程度上取决于节子的出现和节子周围的局部材料方向。然而，缺乏建立当地物质方向的完整数据集的方法。本研究旨在开发和应用一种实验室方法，在含节木材试件的高分辨率3D网格中评估生长层的几何形状和纤维的取向。实验室方法是基于光学平板扫描和激光扫描，前者产生表面图像，后者利用管胞效应，在扫描表面的高分辨率网格中确定面内纤维角度。一个含有单节的矩形实木试件是从树上切下来的，这样就可以假定试件中存在一个对称面。通过将试件穿过该平面并穿过结的中心线，获得了两个具有假定相同但镜像性质的新试件。在其中一个新标本上，随后扫描了纵向-径向平面，并在另一个标本上扫描了纵向-切向平面。然后，通过在两个试件上反复刨出材料，然后扫描逐渐出现的新表面，获得沿不同生长层的3D坐标位置和3D网格中纤维的3D取向。检测到的纤维取向和生长层几何形状之间的比较被用于评估获得的关于3D纤维取向的准确性。结果表明，该方法非常适合于生长层表面的捕捉，并提供了接近结点的三维纤维取向的可靠信息。这些知识对于理解木材的性质，包括木节，是非常重要的。所获得的定量数据也可用于在接近结点的纤维取向上校准一般模型的模型参数。
Abstract The strength of structural timber largely depends on the occurrence of knots and on the local material directions in the surroundings of such knots. There is, however, a lack of methods for establishing a full dataset of the local material directions. The present research aims at the development and application of a laboratory method to assess the geometry of growth layers and the orientation of fibres in a high-resolution 3D grid within wood specimens containing knots. The laboratory method was based on optical flatbed scanning and laser scanning, the former resulting in surface images and the latter, utilizing the tracheid effect, resulting in in-plane fibre angles determined in high-resolution grids on scanned surfaces. A rectangular solid wood specimen containing a single knot was cut from a tree in such a way that it could be assumed that a plane of symmetry existed in the specimen. By splitting the specimen through this plane through the centre line of the knot, two new specimens with assumed identical but mirrored properties were achieved. On one of the new specimens, the longitudinal-radial plane was subsequently scanned, and the longitudinal–tangential plane was scanned on the other. Then, by repeatedly planing off material on both specimens followed by scanning of the new surfaces that gradually appeared, 3D coordinate positions along different growth layers and 3D orientation of fibres in a 3D grid were obtained. Comparisons between detected fibre orientation and growth layer geometry were used for the assessment of the accuracy obtained regarding 3D fibre orientation. It was shown that the suggested method is well suited to capture growth layer surfaces and that it provides reliable information on 3D fibre orientation close to knots. Such knowledge is of great importance for understanding the properties of timber including knots. The quantitative data obtained are also useful for calibration of model parameters of general models on fibre orientation close to knots.