Simulation and Analysis of Hygroscopic Warping of Sawn Timber by a Finite Element Method

有限元素法模擬與分析徑面與弦面板木材之濕翹曲

李世豪(Shih-Hao Lee)

《台灣林業科學》 27卷2期 (2012/06) Pp. 125-130

https://doi.org/10.7075/TJFS.201206.0125

摘要

木材含水率改變時，木材會因材料各部分收縮或膨脹差異而發生翹曲。木材因含水率變異而引起翹曲現象之主要原因是實木異方性與非均質性。此翹曲現象會造成相當大產品價值降低、生產者沮喪與消費者失去信心。因此翹曲是使用實木最重要問題，值得進一步探究。本研究目的是提出分析方法與研發三維有限元素模型應用在實木翹曲行為。使用ANSYS軟體開發三維有限元素模型來模擬與分析實木因含水率梯度而引起翹曲。透過功能強大ANSYS，實木有限元素模型與翹曲變形幾何能以圖示展現。文中詳盡說明公式化控制方程式、模型之研發與電腦模擬之結果。本研究成功地模擬與分析實木翹曲。這些結果顯示有限元素模型足以反應出弦與徑面板之濕翹曲，有助於業者瞭解複雜翹曲與激發如何減少翹曲之想法。

關鍵字

差異收縮 ； 有限元素法 ； 濕翹曲 ； 含水率梯度

並列摘要

Wood warps due to differential shrinkage or swelling when the moisture content (MC) of the wood changes. Anisotropy and non-homogeneity of solid wood are the main causes for this behavior of wood when it experiences variations in MCs. This warping phenomenon causes considerable reductions in product value, frustration for manufacturers, and loss of confidence by consumers. Therefore, the warping of wood is a leading technical problem and deserves further investigation. The objectives of this study were to propose an analytical method and develop a three-dimensional (3D) finite element model (FEM) to examine the warping behavior of solid wood.A 3D FEM was developed to simulate and analyze the hygroscopic warping of sawn timber with the commercial software, ANSYS (vers. 5.3; ANSYS, Canonsburg, PA). Through this potent tool, the FEM and the deformed geometry were graphically demonstrated. This specially developed FEM was applied here to understand warping due to MC gradients in solid wood. Formulation of the governing equations, detailed model development, computer simulation results are presented in the text.It appears that the simulation and analysis were successfully carried out in this study. These results suggest that this FEM adequately reflects hygroscopic deformations of flat-sawn and quarter-sawn plates and can help practitioners understand the complex warping behavior and generate ideas on how to reduce the magnitude of warping.

並列關鍵字

differential shrinkage ； finite element method ； hygroscopic warping ； moisture content gradient