DIELECTRIC PROPERTIES OF WOOD AND HARDBOARD: VARIATION WITH TEMPERATURE, FREQUENCY, MOISTURE CONTENT, AND GRAIN ORIENTATION
DIELECTRIC PROPERTIES OF WOOD AND HARDBOARD: VARIATION WITH TEMPERATURE, FREQUENCY, MOISTURE CONTENT, AND GRAIN ORIENTATION
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木材和硬纸板的介电性能：随温度、频率、水分含量和纹理方向的变化
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
R. King
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文献类型：
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作者：
W. L. James;Y. Yen;R. King
在20赫兹（Hz）至50兆赫（MHz）的频率、从烘箱干燥至完全饱和的湿度条件、从-20 ℃至+90 ℃的温度下测量白色橡木、道格拉斯冷杉和四种商业硬质纤维板的介电常数和损耗角正切。对于天然木材，电场与三个主要结构方向一致。在电场垂直于板的表面的情况下测量硬质纤维板。研究的所有材料的行为在定性上相似。介电常数随含水率或温度的增加而增加，随频率的增加而减小。磁化强度的范围从高频率下冷的干燥材料的约2.0到低频率下温暖的浸水木材的近100万（平行于纹理）。损耗角正切在各种条件下都有最大值和最小值。无论是水分含量还是温度的增加，极端情况发生的频率通常都更高。损耗角正切在约0.01至约100的范围内。一个理论的基础上物理上合理的假设，并提供了充分的描述所观察到的频率对木材的介电性能的影响。本出版物中使用的贸易，公司或公司名称是为了读者的信息和方便。此类使用并不构成美国农业部对任何产品或服务的正式认可或批准，排除其他可能合适的产品或服务。木材和硬质纤维板的介电特性：随温度、频率、含水量和纹理方向的变化。詹姆斯，物理学家森林产品实验室，1美国农业部林务局
The dielectric constant and loss tangent of white oak, Douglas-fir, and four commercial hardboards were measured at frequencies from 20 Hertz (Hz) to 50 Megahertz (MHz), moisture conditions from ovendry to complete saturation, temperatures from -20 to +90° C., ,and, for the natural wood, with the electric field alined with three principal structural orientations. The hardboard was measured with the electric field perpendicular to the faces of the board. The behavior of all materials studied was qualitatively similar. The dielectric constant increased with increasing moisture content or temperature, and decreased with increasing frequency. Magnitudes ranged from about 2.0 for cold, dry material at high frequencies to near 1 million for warm, water-soaked wood at low frequencies (parallel to the grain). Loss tangent showed maximum and minimum values under various conditions. The frequencies at which extremes occurred generally were higher as either moisture content or temperature increased. The loss tangent ranged from about 0.01 to about 100. A theory based on physically plausible assumptions was developed, and provided adequate description of the observed influence of frequency on dielectric properties of wood. The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the U.S. Department of Agriculture of any product or service to the exclusion of others that may be suitable. DIELECTRIC PROPERTIES OF WOOD AND HARDBOARD: VARIATION WITH TEMPERATURE, FREQUENCY, MOISTURE CONTENT, AND GRAIN ORIENTATION By WILLIAM L. JAMES, Physicist Forest Products Laboratory, 1 Forest Service U.S. Department of Agriculture