Inspired by the use of rift-sawn softwood board for covering curved surfaces in Kokerabuki, a traditional Japanese roofing method, we investigated the flexural anisotropy of wood caused by its end-grain orientation. We measured the flexural displacement of softwood species, Chamaecyparis obtusa and Cryptomeria japonica, and hardwood species, Populus suaveolens and Cerasus serrulata. For the softwood species, this was approximately five times longer for the rift-sawn specimens than for the other grain patterns. Using the replica method to measure the softwood tracheid deformation with different flexural displacements, we confirmed the different deformation mechanisms of the tracheid in the flat- and quarter-sawn specimens, and rift-sawn specimens. In the flat- and quarter-sawn woods, on-axis loading was generated, in which the stress was concentrated on the radial and tangential cell walls parallel to the direction of tension or compression. By contrast, in the rift-sawn wood, off-axis loading was generated, in which the stress was evenly distributed throughout the corner cell walls without the wall directly resisting the tensile and compressive forces. We also concluded that the tapered shape of the tracheid walls contributes to the excellent flexibility of rift-sawn softwood.

中文翻译：

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端粒取向引起裂谷软木板的挠曲各向异性

受到日本传统屋面瓦楞纸技术中裂谷软木板覆盖弯曲表面的启发，我们研究了由木材的端粒取向引起的弯曲各向异性。我们测量了软木树种Chamaecyparis obtusa和Cryptomeria japonica以及硬木树种Populus suaveolens和Cerasus serrulata的挠曲位移。对于软木树种来说，裂谷锯的标本比其他木纹的大约要长五倍。使用复制法测量具有不同挠曲位移的针叶木气管的变形，我们证实了在平锯，四分之一锯片和裂谷锯片中气管的不同变形机制。在平锯和四分之一锯材中，产生了轴向载荷，其中应力集中在平行于拉伸或压缩方向的径向和切向孔壁上。相反，在裂谷木材中，产生了轴外载荷，其中应力均匀分布在整个角单元壁上，而壁不直接抵抗拉伸力和压缩力。我们还得出结论，气管壁的锥形形状有助于裂谷锯材的出色柔韧性。