Non-destructive methodologies for the evaluation of moisture content in sawn timber structures: ground-penetrating radar and ultrasound techniques
Non-destructive methodologies for the evaluation of moisture content in sawn timber structures: ground-penetrating radar and ultrasound techniques
复制标题
DOI：
10.3997/1873-0604.2010048
复制
发表时间：
2010-12
影响因子：
1.6
通讯作者：
I. Rodriguez-Abad;R. Martinez-Sala;F. García-García-F.-García-García-66051700;R. Capuz-Lladro
中科院分区：
文献类型：
--
作者：
I. Rodriguez-Abad;R. Martinez-Sala;F. García-García-F.-García-García-66051700;R. Capuz-Lladro
含水率（MC）是木材大多数物理和化学病理的关键参数，在结构木材的情况下，MC低于20%对任何承重结构都是危险的。在木材使用过程中，通过现有方法（烘箱干燥和阻力木材计）评估MC的复杂性促使我们在现场测试非破坏性技术来评估该参数。考虑到这一点，使用两种非破坏性技术，即探地雷达和超声波，对Pinus pinaster Ait的托梁进行了测量。从它们的初始绿色状态到吸湿平衡含水量点。特别是，本文的分析侧重于每种技术在木材干燥过程中记录其波的速度变化的能力。在GPR分析之前，有必要区分木材各向异性引起的电磁波传播速度差异和MC变化引起的电磁波传播速度差异。电磁波的传播速度总是被发现当电场平行于木纹时比垂直于木纹时要低。而当电场垂直时，无论是径向还是切向，对(v)电磁均无显著影响。直接测量表明，探地雷达技术能够表征木材的MC，因为MC的明显减少导致(v) EM的增加。两个参数与测定系数呈较强的相关性，r2为90%。利用超声技术测定了木材干燥过程中的纵向弹性波速。尽管（vp）随各托梁MC的减小而增大，但这两个变量之间的决定系数很低。本文的分析是探地雷达技术在木材物理性质研究中的成功应用，在木材MC的无损现场分析中具有广阔的应用前景。
The moisture content ( MC ) is a critical parameter for most physical and chemical pathologies of timber and, in the case of structural wood, a MC > 20% can be dangerous for any load-bearing construction. The complexity of evaluating MC while timber is in use by means of the current methods (oven-drying and resistance wood meter) led us to test non-destructive techniques to evaluate this parameter on site. With this in mind, measurements with two non-destructive techniques, ground-penetrating radar (GPR) and ultrasound, were carried out on joists of Pinus pinaster Ait. from their initial green state until the point of hygroscopic equilibrium moisture content. In particular, the analysis presented in this paper focuses on the capacity of each technique to register the velocity variations of their waves during the timber drying process. Prior to the GPR analysis, it was necessary to distinguish between differences in the propagation velocity of electromagnetic waves ( v EM ) attributable to the wood anisotropy and those due to variations in MC . The propagation velocity of the electromagnetic waves was always found to be lower when the electrical field was parallel to the grain of the wood than when it was perpendicular to it. However, when the field was perpendicular, its direction whether radial or tangential, did not significantly affect the ( v EM . The direct measurements illustrate the ability of the GPR technique to characterize the MC of timber as a clear decrease in the MC resulted in an increase in the ( v EM . A strong correlation was obtained between the two parameters with coefficients of determination, R 2 > 90%. Longitudinal elastic wave velocities ( v P ) were assessed by means of a ultrasound technique during the timber drying process. Despite the fact that the ( v P increased with the decreasing MC of each joist, the determination coefficient between these two variables was very low. The analysis presented in this paper is a successful application of the GPR technique to the study of wood’s physical properties and has a promising future for the non-destructive, on-site analysis of timber MC .