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首页> 外文期刊>Wood and Fiber Science >Recovery of mechanically induced residual stresses in densified softwoods created during a densification process.
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Recovery of mechanically induced residual stresses in densified softwoods created during a densification process.

机译：在致密化过程中产生的致密软木中机械诱导的残余应力的恢复。

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摘要

Mechanical densification technology has been used to increase density and mechanical properties of low-density wood. After the densification process, some internal stresses created during densification can be temporally "locked" in wood, which is defined as mechanically induced residual stresses. When the densified wood is exposed to wet conditions, these mechanically induced residual stresses along with swelling stresses can be released with time, which might result in dimensional instability causing warping. This study aimed at examining mechanically induced residual stresses in densified softwoods and simulating the stress-releasing process by means of a mathematical model. Balsam fir and eastern white pine were used for undensified wood specimens and densified wood specimens that were compressed at three compression ratios (CRs) of 0.25, 0.50, and 0.60. Specimens compressed at 0.50 and 0.60 CR plus one control group of undensifed specimens (ie CR=0) was used to calculate model parameters, and ones at 0.25 CR were used to verify the model developed. Total residual stresses were directly measured by soaking softwood specimens in hot water of 60 degrees C. It was found that (1) about 50% of maximum total residual stress in densified fir and pine specimens could be released in the first several minutes after soaking in the hot water; (2) the mechanically induced residual stresses increased with increasing CR; (3) the mechanically induced residual stresses released from pine were slightly larger than those from fir; and (4) the mathematical model developed in terms of CR could well simulate the release of mechanically induced residual stress with increasing time.
机译：机械致密化技术已用于提高低密度木材的密度和机械性能。在致密化过程之后，致密化过程中产生的一些内部应力可以暂时“锁定”在木材中，这被定义为机械引起的残余应力。当致密化的木材暴露于潮湿条件下时，这些机械诱导的残余应力以及膨胀应力会随着时间的流逝而释放，这可能会导致尺寸不稳定，从而导致翘曲。这项研究旨在检查致密软木中机械引起的残余应力，并通过数学模型模拟应力释放过程。香脂冷杉和东部白松树分别用于未压缩的木材样本和以0.25、0.50和0.60的三个压缩比（CR）压缩的压缩的木材样本。在0.50和0.60 CR压缩的样品加上一个对照组的未压缩样品（即CR = 0）用于计算模型参数，而在0.25 CR的样品用于验证建立的模型。通过将软木试样浸泡在60摄氏度的热水中直接测量总残余应力。发现（1）浸泡在杉木和松木中的致密化试样在最初的几分钟内可以释放约50％的最大总残余应力。热水; （2）机械诱导的残余应力随着CR的增加而增加; （3）松树释放的机械诱导残余应力比冷杉释放的略大; （4）根据CR开发的数学模型可以很好地模拟机械诱导的残余应力随时间的释放。

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