“Short-term” mechano-sorptive creep of well-defined spruce timber
“Short-term” mechano-sorptive creep of well-defined spruce timber
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DOI：
10.1007/s001070050483
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发表时间：
2001-04
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影响因子：
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通讯作者：
C. Bengtsson
中科院分区：
文献类型：
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作者：
C. Bengtsson
本文介绍了在相对湿度(RH)为30-90%的多变气候条件下的弯曲蠕变试验结果。测试了来自15棵有良好历史记录的速生和慢生树木的81个样本，45×70×1100 mm。蠕变试验的持续时间至少为42天。采用简单的统计方法对蠕变试验结果进行评价。对于材料的一部分，在1-1.5个水分循环后的短期蠕变与额外的水分循环后的相对蠕变进行了比较。1-1.5个水分循环后的相对蠕变是额外水分循环后相对蠕变的一个很好的预测指标。材料性能的大范围并没有完全反映在相对蠕变试验结果中。相对蠕变的变化似乎随着水分循环次数的增加而减小。从生长缓慢的林分和快速生长的林分中，不可能确认相对蠕变在统计学上的显著差异。对于假定含有幼龄材和成熟材的试件，在1-1.5、3-3.5和5-5.5个水分循环后，相对蠕变有统计学意义的差异。假定含有幼龄木材的试件显示出最大的相对蠕变值。在81个试件中，发现在第一次水分变化期间的变形变化为初始弹性变形的14%-97%。这种变形与材料参数之间的相关性很弱。然而，在第一次水分变化过程中，三棵树的样品获得了最大的变形。蠕变试验开始时的湿度条件(30%RH或90%RH)不是蠕变行为的控制因素。
In this paper creep test results in bending in a variable climate, 30-90% relative humidity (RH), are presented. Eighty-one specimens, 45× 70× 1100 mm, from fifteen both fast-grown and slow-grown trees with well-documented history were tested. The duration of the creep tests was at least 42 days. Simple statistical methods were used to evaluate the creep test results. For a part of the material the short-term creep, after 1-1.5 moisture cycles, was compared with relative creep after additional moisture cycles. The relative creep after 1-1.5 moisture cycles was a good predictor of the relative creep after additional moisture cycles. The wide range in material properties was not completely reflected in the relative creep test results. It seemed like the variation in relative creep decreased with increasing amount of moisture cycles. It was not possible to confirm a statistically significant difference in relative creep between specimens from the slow-grown and the fast-grown stands. For specimens assumed to contain juvenile wood and mature wood, there was a statistically significant difference in relative creep after 1-1.5, 3-3.5 and 5-5.5 moisture cycles. Specimens assumed to contain juvenile wood showed the largest relative creep values. In the test material, 81 specimens, a variation in deformation during the first moisture change of 14%-97% of the initial elastic deformation was found. The correlation between this deformation and material parameters was weak. However, the largest deformations during the first moisture change were obtained for specimens from three trees. The moisture conditions when the creep tests started (30% RH or 90% RH) were not a governing factor for the creep behaviour.