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Strength grading of hardwoods using transversal ultrasound
European Journal of Wood and Wood Products ( IF 2.6 ) Pub Date : 2020-08-14 , DOI: 10.1007/s00107-020-01573-2
A. Kovryga , A. Khaloian Sarnaghi , J. W. G. van de Kuilen

Detection of local wood inhomogeneities is important for accurate strength and stiffness prediction. In hardwood specimens, visual characteristics (e.g. knots or fibre deviation) are difficult to detect, either with a visual surface inspection or by the machine. Transversal ultrasound scan (TUS) is a non-destructive evaluation method with high potential for hardwoods. The method relies on differences in ultrasound wave propagation in perpendicular to the grain direction. The aim of this study is to estimate and analyse the capabilities of TUS for defect detection in hardwoods and prediction of mechanical property values. In the current paper, the TUS was applied to the hardwood species European ash (Fraxinus excelsior L.), Norway maple (Acer platanoides L.) and sycamore maple (Acer pseudoplatanus L.). In total, 16 boards of both specimens were completely scanned perpendicular to the grain using a laboratory scanner with dry-coupled transducers. The measurements were processed to 2D scan images of the boards, and image processing routines were applied to further feature extraction, defect detection and grading criteria calculation. In addition, as a reference for each board, all relevant visual characteristics and mechanical properties from the tensile test were measured. Using the TUS global fibre deviation, the size and the position of the knots can be detected. Knottiness correlates to the strength properties similarly or even better compared to the manual knottiness measurement. Between the global fibre angle measured using TUS and measured on the failure pattern, no correlation could be found. The ultrasound modulus of elasticity perpendicular to the grain does not show any meaningful correlation to the elastic properties parallel to the grain. In overall, TUS shows high potential for the strength grading of hardwoods.



中文翻译:

横向超声对硬木强度分级

木材局部不均匀性的检测对于准确的强度和刚度预测很重要。在硬木样品中,无论是通过视觉表面检查还是通过机器,都很难检测到视觉特征(例如,打结或纤维偏斜)。横向超声扫描(TUS)是一种非破坏性评估方法,对硬木具有很高的潜力。该方法依赖于垂直于晶粒方向的超声波传播差异。这项研究的目的是评估和分析TUS在硬木中进行缺陷检测和预测机械性能值的能力。在当前的论文中,TUS应用于硬木树种欧洲白蜡木(Fraxinus excelsior L.),挪威枫树(Acer platanoides L。)和无花果树种(Scacamore Maple)。伪宏cer)。总共,使用带有干耦合传感器的实验室扫描仪,垂直于谷物垂直扫描了两个样品的16个板。将测量结果处理为电路板的2D扫描图像,并将图像处理例程应用于进一步的特征提取,缺陷检测和等级标准计算。另外,作为每个板的参考,测量了拉伸试验中所有相关的视觉特性和机械性能。使用TUS全局纤维偏差,可以检测出结的大小和位置。与手动打结度测量相比,打结度与强度特性的相关性相似甚至更好。在使用TUS测量的整体光纤角度与在故障模式上测得的总光纤角度之间,没有发现相关性。垂直于晶粒的超声弹性模量与平行于晶粒的弹性特性没有任何有意义的关联。总体而言,TUS对硬木的强度分级显示出很高的潜力。

更新日期:2020-08-14
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