Sydor Maciej, Majka Jerzy, Rychlik Michał, Turbański Wojciech
Department of Woodworking and Fundamentals of Machine Design, Faculty of Forestry and Wood Technology, Poznań University of Life Sciences, 60-637 Poznań, Poland.
Euroline sp. z o.o., 64-100 Leszno, Poland.
Materials (Basel). 2023 Mar 2;16(5):2053. doi: 10.3390/ma16052053.
Swelling and shrinkage anisotropy affect the susceptibility to an assembly of wooden elements by changing designed clearances or interference fits. This work described the new method to measure mounting holes' moisture-induced shape instability and its verification using three sets of twin samples made of Scots pinewood. Each set of samples contained a pair with different grain patterns. All samples were conditioned under reference conditions (relative air humidity-RH = 60% and temperature 20 °C), and their moisture content (MC) reached equilibrium (10.7 ± 0.1%). On the side of each sample, the seven mounting holes of 12 mm in diameter were drilled. Immediately after drilling, Set 1 was used to measure the effective hole diameter with 15 cylindrical plug-gauges with diameters of 0.05 mm step, while Set 2 and Set 3 were separately re-seasoned by six months in two extreme conditions. Set 2 was conditioned with air at 85% RH (reached an equilibrium MC of 16.6 ± 0.5%), while Set 3 was exposed to air at 35% RH (reached an equilibrium MC of 7.6 ± 0.1%). Results of the plug gauge tests highlighted that holes in the samples subjected to swelling (Set 2) increased an effective diameter in the range of 12.2-12.3 mm (1.7-2.5%), while samples subjected to shrinking (Set 3) reduced the effective diameter to 11.9-11.95 mm (0.8-0.4%). To accurately reproduce the complex shape of the deformation, gypsum casts of holes were made. The 3D optical scanning method was used to read the gypsum casts' shape and dimensions. The 3D surface map of deviations analysis provided more detailed information than the plug-gauge test results. Both the shrinking and swelling of the samples changed the shapes and sizes of the holes, but shrinking reduced the effective diameter of the hole more than swelling increased it. The moisture-induced changes in the shape of holes are complex: the holes ovalized with a different range, depending on the wood grain pattern and hole depth, and were slightly extended in diameter at the bottom. Our study provides a new way to measure 3D hole initial shape changes in wooden elements during desorption and absorption.
膨胀和收缩各向异性通过改变设计间隙或过盈配合来影响木制构件组装的易感性。本文描述了一种测量安装孔因水分引起的形状不稳定性的新方法，并使用三组由苏格兰松木制成的双样本进行了验证。每组样本包含一对具有不同纹理模式的样本。所有样本均在参考条件（相对空气湿度-RH = 60%，温度20°C）下进行调湿处理，其含水率（MC）达到平衡（10.7±0.1%）。在每个样本的一侧，钻出7个直径为12毫米的安装孔。钻孔后立即使用第1组样本，用15个直径以0.05毫米步长变化的圆柱形塞规测量有效孔径，而第2组和第3组样本分别在两种极端条件下重新调湿6个月。第2组样本在85% RH的空气中进行调湿处理（达到平衡含水率16.6±0.5%），而第3组样本暴露在35% RH的空气中（达到平衡含水率7.6±0.1%）。塞规测试结果表明，经历膨胀的样本（第2组）中的孔有效直径增加到12.2 - 12.3毫米（增加了1.7 - 2.5%），而经历收缩的样本（第3组）中的孔有效直径减小到11.9 - 11.95毫米（减小了0.8 - 0.4%）。为了准确再现变形的复杂形状，制作了孔的石膏模型。使用三维光学扫描方法读取石膏模型的形状和尺寸。三维表面偏差分析图提供了比塞规测试结果更详细的信息。样本的收缩和膨胀都改变了孔的形状和尺寸，但收缩使孔的有效直径减小的幅度大于膨胀使其增加的幅度。水分引起的孔形状变化很复杂：孔会根据木材纹理模式和孔深不同程度地椭圆化，并且在底部直径略有增大。我们的研究提供了一种测量木制构件在解吸和吸收过程中三维孔初始形状变化的新方法。
