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木质材料无损检测的应用与研究进展 总被引:3,自引:0,他引:3
《林业工程学报》2016,(6)
木质材料无损检测主要包括缺陷无损检测和力学性能无损检测两个方面,其无损检测基本方法主要有应力波法、机械应力变形法、振动法、微钻阻力法、射线法、雷达波法等。笔者先从检测原理入手对目前常见的木质材料内部缺陷和力学性能无损检测方法作了归纳,同时对木材和人造板内部缺陷和力学性能无损检测的应用和研究现状进行了归纳分析。木材和活立木无损检测技术发展较快,锯材和单板应力分等技术已有较为完善的检测设备,在发达国家已被广泛应用;古建筑木构件和活立木内部缺陷无损检测实际应用也较多,但在检测精度和效率提高方面仍有广阔的发展空间。人造板无损检测的研究近年来主要集中在力学性能检测方面,实际应用较少。对已经有较好应用的无损检测技术,下一步科研的目标应是进一步提高检测精度和效率;对尚处在科研探索阶段的无损检测技术,下一步仍应从基础理论完善和技术实现角度坚持工作。 相似文献
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应力波用于木材和活立木无损检测的研究进展 总被引:2,自引:0,他引:2
在简单介绍应力波无损检测技术的基本原理、特点以及目前应力波主要的检测设备同时,对国内外应力波无损检测技术在木材和活立木领域的研究进展做了叙述,分析了现阶段应力波无损检测技术存在的问题,并对应力波无损检测技术进一步发展做了展望。 相似文献
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无损检测在木材分等到木材构件机械性能的现场评估范围内得到广泛应用。本文阐述了无损检测的基本概念,记述了无损检测在林产品中的早期研究成果,以及无损检测在现代工业中的应用及其研究工作状况。 相似文献
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木材无损检测的现状及展望 总被引:2,自引:0,他引:2
无损检测在木材分等到木材构件机械性能的现场评估范围得到广泛应用。本文阐述了无损检测的基本概念,记述了无损检测在林产品中的早期研究成果,以及无损检测在现代工业中的应用及其研究工作状况。 相似文献
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木质材料力学性能无损检测方法的研究现状与趋势 总被引:3,自引:1,他引:2
木质材料用途广泛,在建筑、家具和包装等领域发挥着重要作用。目前,木材无损检测技术发展很快,应用到木材性质检测的无损检测方法已达几十种,然而对木质材料力学性能的检测还处于相对初级阶段,具有较大的挑战性。本文对木质材料力学性能的无损检测方法和原理进行归纳与总结,阐述几种主要检测技术(如应力渡检测、超声渡检测、振动法检测)的国内外研究现状、检测特点及存在问题。在此基础上,提出木质材料力学性能无损检测技术的发展趋势。 相似文献
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木材无损检测技术及其应用与展望 总被引:10,自引:5,他引:10
对木材无损检测的基本原理和主要方法进行了简要论述,介绍了木材无损检测技术在当今木材科学研究和木材加工中的应用,并对无损检测技术在今后木材科学领域的应用前景做了展望。 相似文献
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Most fine woody debris (FWD) line-intersect sampling protocols and associated estimators require an approximation of the quadratic mean diameter (QMD) of each individual FWD size class. There is a lack of empirically derived QMDs by FWD size class and species/forest type across the U.S. The objective of this study is to evaluate a technique known as the graphical estimation (GE) method for estimating FWD QMDs across forests of the U.S. Results indicate tremendous inter- and intra-specific variation in small FWD diameters. In addition, GE model fitting results demonstrated a lack of substantial difference in FWD QMDs between common forest types. It is postulated that the mixing, fracturing, and decay of both tree and shrub downed woody debris in diverse forest types across the U.S. can homogenate FWD QMDs at state/national levels. In the absence of site-specific empirical measurement of FWD QMDs, it is suggested that a general national set of FWD QMDs derived from the GE method be adopted for large-scale FWD monitoring efforts. 相似文献
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探地雷达在植物根系研究中的应用 总被引:4,自引:0,他引:4
根系是植物的重要组成部分,研究根系对于水土保持和农林业生产具有重要的意义。目前,在野外自然条件下进行根系研究,与植物地上部分研究相比相对落后。其主要原因是研究方法问题,目前已知的研究方法,相当繁琐,耗时费力,而且所得结果又常常不太准确,使许多研究人员望而生畏。探地雷达作为一种地球物理探测工具,随着技术的发展,完全能够应用于根系研究,本文简单介绍了探地雷达的原理,以及探地雷达在根系研究应用中的进展情况。 相似文献
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应力波技术在木材性质检测中的研究进展 总被引:15,自引:4,他引:15
本文简要叙述了应力波检测技术的原理以及在木材性质检测方面的研究进展,在此基础上提出用于木材性质检测的应力波技术的发展趋势。 相似文献
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Litter quality and environmental effects on Scots pine (Pinus sylvestris L.) fine woody debris (FWD) decomposition were examined in three forestry-drained peatlands representing different site types along a climatic gradient from the north boreal (Northern Finland) to south (Southern Finland) and hemiboreal (Central Estonia) conditions. Decomposition (percent mass loss) of FWD with diameter ≤10 mm (twigs) and FWD with diameter >10 mm (branches) was measured using the litter bag method over 1–4-year periods. Overall, decomposition rates increased from north to south, the rate constants (k values) varying from 0.128 to 0.188 year−1 and from 0.066 to 0.127 year−1 for twigs and branches, respectively. On average, twigs had lost 34%, 19% and 19%, and branches 25%, 17% and 11% of their initial mass after 2 years of decomposition at the hemiboreal, south boreal and north boreal sites, respectively. After 4 years at the south boreal site the values were 48% for twigs and 42% for branches. Based on earlier studies, we suggest that the decomposition rates that we determined may be used for estimating Scots pine FWD decomposition in the boreal zone, also in upland forests. Explanatory models accounted for 50.4% and 71.2% of the total variation in FWD decomposition rates when the first two and all years were considered, respectively. The variables most related to FWD decomposition included the initial ash, water extractives and Klason lignin content of litter, and cumulative site precipitation minus potential evapotranspiration. Simulations of inputs and decomposition of Scots pine FWD and needle litter in south boreal conditions over a 60-year period showed that 72 g m−2 of organic matter from FWD vs. 365 g m−2 from needles accumulated in the forest floor. The annual inputs varied from 5.7 to 15.6 g m−2 and from 92 to 152 g m−2 for FWD and needles, respectively. Each thinning caused an increase in FWD inputs, up to 510 g m−2, while the needle inputs did not change dramatically. Because the annual FWD inputs were lowered following the thinnings, the overall effect of thinnings on C accumulation from FWD was slightly negative. The contribution of FWD to soil C accumulation, relative to needle litter, seems to be rather minor in boreal Scots pine forests. 相似文献
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Sangdae Lee Sang-Joon Lee Jong Su Lee Ki-Bok Kim Jun-Jae Lee Hwanmeyong Yeo 《Journal of Wood Science》2011,57(5):387-394
Most old buildings in Korea are wood framed and, with age, deterioration is found in all wood components of antique buildings.
Insects and rapid changes in humidity are among the main causes of deterioration. To preserve antique wooden buildings, nondestructive
testing (NDT) methods are required. Various methods of nondestructive evaluation (NDE) such as X-ray, stress wave, drilling
resistance test, and ultrasound are used to inspect the safety of wooden antique buildings. The ultrasonic method is relatively
simple, inexpensive, and accurate. The rafters are one of the main components of antique buildings and are seriously affected
by deterioration. This study aimed to develop a nondestructive ultrasonic technique for evaluation of wooden rafter deterioration.
Regression models describing the relationship between the artificial deterioration of the specimen and ultrasonic parameters
were proposed. The method was found to be reliable for evaluating wooden rafter deterioration. 相似文献
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Wood nondestructive testing technology is a new and multidisciplinary industry scientific research. It has attained fast development
and achievements in recent years. X-ray computed tomography (CT) scanning technology is a kind of wood nondestructive testing
technology in practice. CT scanning technology has been applied to the detection of internal defects in the logs for the purpose
of obtaining prior information, which can be used to reach better wood sawing decision. Fractal geometry and its extension
multifractal are used for describing, modeling, analyzing, and processing of different complex shapes and images. A method
in CT image edge detection using multifractal theory combined with fractal Brownian motion is applied in the paper. First,
its multifractal spectrum is estimated. Then, different types of pixels are classified by the spectrum; they are smoothing
edge points and singular edge points. From the images processed by multifractal spectrum theory and compared with each image
by different spectrum values, it can be seen that the larger the range of threshold is set, the more exact the edge can be
detected. The paper provides a new method to recognize the defect information and to saw it in the condition of nondestructive
wood. 相似文献
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Detection of tree roots and determination of root diameters by ground penetrating radar under optimal conditions 总被引:3,自引:0,他引:3
A tree's root system accounts for between 10 and 65% of its total biomass, yet our understanding of the factors that cause this proportion to vary is limited because of the difficulty encountered when studying tree root systems. There is a need to develop new sampling and measuring techniques for tree root systems. Ground penetrating radar (GPR) offers the potential for direct nondestructive measurements of tree root biomass and root distributions to be made. We tested the ability of GPR, with 500 MHz, 800 MHz and 1 GHz antennas, to detect tree roots and determine root size by burying roots in a 32 m3 pit containing damp sand. Within this test bed, tree roots were buried in two configurations: (1) roots of various diameters (1-10 cm) were buried at a single depth (50 cm); and (2) roots of similar diameter (about 5 cm) were buried at various depths (15-155 cm). Radar antennas were drawn along transects perpendicular to the buried roots. Radar profile normalization, filtration and migration were undertaken based on standard algorithms. All antennas produced characteristic reflection hyperbolas on the radar profiles allowing visual identification of most root locations. The 800 MHz antenna resulted in the clearest radar profiles. An unsupervised, maximum-convexity migration algorithm was used to focus information contained in the hyperbolas back to a point. This resulted in a significant gain in clarity with roots appearing as discrete shapes, thereby reducing confusion due to overlapping of hyperbolas when many roots are detected. More importantly, parameters extracted from the resultant waveform through the center of a root correlated well with root diameter for the 500 MHz antenna, but not for the other two antennas. A multiple regression model based on the extracted parameters was calibrated on half of the data (R2 = 0.89) and produced good predictions when tested on the remaining data. Root diameters were predicted with a root mean squared error of 0.6 cm, allowing detection and quantification of roots as small as 1 cm in diameter. An advantage of this processing technique is that it produces results independently of signal strength. These waveform parameters represent a major advance in the processing of GPR profiles for estimating root diameters. We conclude that enhanced data analysis routines combined with improvements in GPR hardware design could make GPR a valuable tool for studying tree root systems. 相似文献