Bertoldo Cinthya, Pereira Geise Aparecida, Gonçalves Raquel
Laboratory of Nondestructive Testing-LabEND, School of Agricultural Engineering-FEAGRI, University of Campinas-UNICAMP, Av. Cândido Rondon, 501-Barão Geraldo, Campinas 13083-875, Brazil.
Materials (Basel). 2023 Jul 7;16(13):4870. doi: 10.3390/ma16134870.
The complete characterization of wood, with the determination of the 12 elastic constants that represent its orthotropy, is greatly relevant in applications employing structural calculation software programs. Ultrasound allows for such characterization with relative simplicity when compared to other methods. The polyhedron is considered the most appropriate specimen format for allowing the 12 constants to be calculated with a single specimen, and the traditionally used one is the 26-sided polyhedron, which, to be produced manually with more precision in directing the main directions of the wood, needs larger faces. The accuracy of this technique tends to be reduced when increasing the growth rings' inclination since the waves deviate from the main directions of orthotropy. This research aimed to verify whether it is possible to reduce the polyhedra dimension without affecting the results of the elastic parameters obtained in wood characterization by ultrasound. The results indicate that the dimension of the polyhedron can be reduced without prejudice to the results of the elastic parameters obtained by the ultrasound test and that, in the manual production process of the specimen, the best way to make this reduction is to eliminate the faces unused in the test, changing the polyhedron to 18 faces instead of 26. Reducing the number of faces simplifies the manufacturing process and thus increases the possibility of producing specimens with straighter growth rings and better-directed symmetry axes.
木材的完整表征，包括确定代表其正交各向异性的12个弹性常数，在使用结构计算软件程序的应用中具有重大意义。与其他方法相比，超声能够相对简单地实现这种表征。多面体被认为是最适合的试样形式，以便用单个试样计算出12个常数，传统上使用的是26面体，为了更精确地手动制作并引导木材的主方向，需要更大的面。当增加年轮倾斜度时，由于波偏离正交各向异性的主方向，该技术的精度往往会降低。本研究旨在验证是否有可能在不影响通过超声进行木材表征所获得的弹性参数结果的情况下减小多面体尺寸。结果表明，可以减小多面体尺寸而不影响超声测试获得的弹性参数结果，并且在试样的手工制作过程中，实现这种减小的最佳方法是去除测试中未使用的面，将多面体改为18面而不是26面。减少面的数量简化了制造过程，从而增加了生产具有更直的年轮和更好定向对称轴的试样的可能性。
