Abstract

Freshly cut 30-mm-thick wood disks of Scots pine, Caucasian elm, narrow-leafed ash, wild cherry, black walnut, and European alder with various natural grade defects were dried together in a radiofrequency-vacuum (RF/V) dryer. A mild four-step drying schedule at the maximum temperature of 45 °C and power density in the range of 1-2 kWm

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with an “on-off” control of RF radiation at the final step was used. The moisture content of the disks at the end of drying ranged from 10.6% to 13.4%. An almost uniform radial moisture gradient developed in the dried disks. The six wood species, however, exhibited variations in checking. The RF/V drying schedule used here was able to completely inhibit near-bark radial checking in all disks but pine and elm, whereas it failed to efficiently prevent V-cracking in pine and ash with a high mean tangential to radial shrinkage anisotropy (S_T/S_R). A strong positive correlation was also found between S_T/S_R and the proportion of V-cracked disks. The occurrence of ring failure within the reaction wood-containing disks of walnut, pine, and elm was almost completely prevented by the drying schedule, but a significant correlation was observed between the pith eccentricity and V-crack length in the compression wood-containing disks of pine. All other natural defects, i.e., scar in cherry, bark pocket, double or triple pithing in walnut and elm, sound knots in pine, and roundness deviation, exhibited no statistically significant effect (p > 0.05) on check formation.

中文翻译：

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射频真空 (RF/V) 技术对具有固有缺陷的木盘混合品种干燥的效率

摘要

在射频真空 (RF/V) 干燥机中将新鲜切割的 30 毫米厚的苏格兰松、高加索榆树、窄叶梣木、野樱桃、黑胡桃和欧洲桤木与各种天然等级缺陷的木盘一起干燥。温和的四步干燥程序，最高温度为 45 °C，功率密度在 1-2 kWm 范围内

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使用了在最后一步对射频辐射进行“开-关”控制。干燥结束时圆盘的水分含量在 10.6% 到 13.4% 之间。在干燥的圆盘中形成了几乎均匀的径向水分梯度。然而，这六种木材在检查方面表现出差异。这里使用的 RF/V 干燥计划能够完全抑制除松树和榆树之外的所有圆盘的近树皮径向检查，但它未能有效地防止具有高平均切向径向收缩各向异性的松树和白蜡树的 V 形开裂（S _T /SR _）。_{S T} /S _R之间也存在强正相关和 V 型裂纹磁盘的比例。干燥计划几乎完全防止了核桃、松树和榆木的反应含木盘内环断裂的发生，但在压缩含木盘中的髓偏心距和 V 形裂纹长度之间观察到显着相关性松树。所有其他自然缺陷，即樱桃中的疤痕、树皮袋、核桃和榆树的双核或三核、松木的健全节和圆度偏差， 对检查形成没有统计学意义( p >0.05)。