The hygroscopic and moisture-dependent mechanical characteristics of small-leaved lime wood (Tilia cordata) were investigated experimentally. This study includes sorption, swelling and shrinkage experiments, as well as tension and compression tests in the three principal anatomical directions at four relative humidity levels. Four sample groups from trees of three different locations in Germany were used. The findings are comparable to those of earlier studies. The hygro-expansion anisotropy is relatively small. Young’s moduli at tension/compression decreased by about 52 %/64 % in radial, 19 %/48 % in tangential and 16 %/58 % in longitudinal direction for an increase of moisture content from 10 % (65 % RH) to 20 % (95 % RH). Tension strengths/compression yield stresses decreased by about 25 %/45 % in radial, 9 %/42 % in tangential, and 32 % (compression) in longitudinal direction, respectively. These parameters increased with an increasing density. Based on the mechanical tests, Young’s modulus, tension strength and compression yield stress were derived as density- and moisture-dependent material model parameters. Shear modulus and shear strength were estimated by a theoretical approach. The experimental and modelling study was accompanied by a literature survey on characteristics of lime wood relevant for hygro-mechanical material modelling.

中文翻译：

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椴木（Tilia cordata）在主要解剖方向上的短期湿度机械行为

小叶椴木的吸湿性和湿度依赖性机械特性（紫椴）进行了实验研究。这项研究包括吸附、膨胀和收缩实验，以及四个相对湿度水平下三个主要解剖方向的拉伸和压缩测试。使用来自德国三个不同地点的树木的四个样本组。研究结果与早期研究结果相当。吸湿膨胀各向异性相对较小。当含水量从 10 % (65 % RH) 增加到 20 % 时，拉伸/压缩杨氏模量径向降低约 52 %/64 %，切向降低 19 %/48 %，纵向降低 16 %/58 % （95% 相对湿度）。径向拉伸强度/压缩屈服应力分别降低约 25%/45%，切向降低 9%/42%，纵向降低 32%（压缩）。这些参数随着密度的增加而增加。根据机械测试，得出杨氏模量、拉伸强度和压缩屈服应力作为与密度和湿度相关的材料模型参数。通过理论方法估计剪切模量和剪切强度。实验和建模研究伴随着与湿力学材料建模相关的石灰木特性的文献调查。