Key message Mechanical properties of small-diameter round timber from hardwood thinnings of common alder ( Alnus glutinosa (L.) Gaertn.), European ash ( Fraxinus excelsior L.), European birch ( Betula pendula Roth. and Betula pubescens Ehrh.), and sycamore ( Acer pseudoplatanus L.) can be evaluated by non-destructive testing on either standing trees or green logs without wood density determination. Velocity differences between acoustic and resonance methods are influenced by tree species and age. Tree diameter improves the estimation of bending strength but not of stiffness. Context There is a need for a reliable, fast, and inexpensive evaluation method to better sort hardwood thinnings according to mechanical properties for use in potential added-value applications. Aims The estimation by non-destructive testing of mechanical properties of round small-diameter timber of four hardwood species (common alder, European ash, European birch, and sycamore). Methods Acoustic velocity was measured in 38 standing trees and resonance velocity was recorded in green logs from these trees. The logs were then dried and tested in bending. Estimation models to predict mechanical properties from non-destructive testing measurements were developed. Results Large differences between velocities from acoustic and resonance techniques were found. Models based on both non-destructive testing velocities together with a species factor are well correlated with bending modulus of elasticity while models including tree diameter are moderately well correlated with bending strength. Inclusion of density in the models does not improve the estimation. Conclusion Models based on acoustic measurements on standing trees or resonance on green logs together with tree species and diameter provide reliable estimates of mechanical properties of round timber from hardwood thinnings. This methodology can be easily used for pre-sorting material in the forest.

中文翻译：

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使用无损检测方法对爱尔兰硬木立木和小直径圆材进行机械性能预测

关键信息 来自普通桤木 (Alnus glutinosa (L.) Gaertn.)、欧洲白蜡 (Fraxinus excelsior L.)、欧洲桦木 (Betula pendula Roth. 和 Betula pubescens Ehrh.) 的硬木间伐的小直径圆材的机械性能，和 sycamore ( Acer pseudoplatanus L.) 可以通过对立木或绿原木的无损测试进行评估，而无需确定木材密度。声学和共振方法之间的速度差异受树种和年龄的影响。树木直径提高了弯曲强度的估计，但没有提高刚度。背景 需要一种可靠、快速且廉价的评估方法，以根据机械性能更好地对硬木间伐材料进行分类，以用于潜在的增值应用。目的 通过无损检测对四种硬木（普通桤木、欧洲白蜡木、欧洲桦木和梧桐树）的圆形小直径木材的机械性能进行评估。方法 测量 38 棵立树的声速，并记录这些树木的绿原木的共振速度。然后将原木干燥并进行弯曲测试。开发了用于预测非破坏性测试测量的机械性能的估计模型。结果 发现来自声学和共振技术的速度之间存在很大差异。基于非破坏性测试速度和物种因子的模型与弹性弯曲模量密切相关，而包括树木直径在内的模型与弯曲强度适度密切相关。在模型中包含密度不会改进估计。结论 基于立树声学测量或绿原木共振以及树种和直径的模型提供了对硬木间伐的圆材机械性能的可靠估计。这种方法可以很容易地用于对森林中的材料进行预分拣。