Round timber is often used for hydraulic engineering works, but the strength grading of round logs is not as well developed as that of sawn timber. The advantages of using defined strength classes, as well as the proper selection of the raw material, could be applicable to hydraulic works as well. In this study, the methods and rules developed for sawn timber were applied to the mechanical selection of oak round logs, paying particular attention to the issue of the simplicity of grading operations and the moisture content of the timber. Both the acoustic velocity and dynamic modulus of elasticity of oak logs were measured with different instruments before performing destructive bending tests; machine settings were derived for both properties and dry and wet grading operations were simulated to compare efficiency. The use of the dynamic modulus of elasticity makes machine grading more efficient. On the other hand, the use of acoustic velocity alone is feasible and makes the procedure much faster, even if wet grading resulted in very conservative estimations. The yields obtained were similar for lower grades, but to achieve higher strength classes, the dynamic modulus was preferable. For very fast and less expensive measurements, velocity could be considered an appropriate method, as an improvement over the use of unselected material.

中文翻译：

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机械强度分级系统在水利工程圆木中的应用

圆木通常用于水利工程，但是圆木的强度等级不如锯木强。使用定义的强度等级以及正确选择原材料的优势也可以适用于水利工程。在这项研究中，将为锯材开发的方法和规则应用于橡木圆木的机械选择，尤其要注意分级操作的简便性和木材的水分含量。在进行破坏性弯曲试验之前，用不同的仪器测量了橡树原木的声速和动态弹性模量。得出机器设置的特性，并模拟干法和湿法分级操作以比较效率。动态弹性模量的使用使机器分级更为有效。另一方面，仅使用声速是可行的，并且即使湿法分级导致非常保守的估计，也可以使该过程更快。对于较低等级，获得的产量相似，但是要获得更高的强度等级，动态模量是优选的。对于非常快速且较便宜的测量，可以将速度视为一种适当的方法，作为对使用非选定材料的一种改进。动态模量是优选的。对于非常快速且较便宜的测量，可以将速度视为一种适当的方法，作为对使用非选定材料的一种改进。动态模量是优选的。对于非常快速且较便宜的测量，可以将速度视为一种适当的方法，作为对使用非选定材料的一种改进。