Age trends and correlations of growth and wood properties in clone of Eucalyptus urophylla × E. grandis in Guangdong, China

We assessed growth traits and wood properties ofDH32-29, a clone of Eucalyptus urophylla x E. grandis, at age of two to six years in Guangdong in China. Analysis of variance of studied traits showed that there were significant differences （1% level） on all studied traits among ages except for wood basic density. Analysis of age trends of growth traits and wood properties revealed that rotation length of DH32-29 should be more than six years or longer. Phenotypic correlations among traits at individual ages indicated that correlations between growth traits were strongly positive. There was significant change in relationship between growth and wood basic density with increasing age, ranging from -0.03 to -0.54 at 2 and 5 year and 0.003 to 0.3 at 3, 4 and 6 year. Correlations between Pilodyn pin penetration and basic density measured on increment cores showed that Pilodyn could rank or group genotypes or sites into density classes, but failure to predict individual tree and individual clone.

Nondestructive testing method of wood moisture content based on a planar capacitance sensor model

For our research, a new hybrid experimental-computational method is presented. We applied a least squares fitting method （LSFM） to reconstruct the wood moisture content （WMC） from the data measured with a planar capacitance sensor. A boundary element method （BEM） was used to compute the relationship between capacitance and the dielectric constant. A functional relationship between MC and the dielectric constant was identified by LSFM. The agreement of this final computation result with the experimental data indicates that this method can be used to estimate the WMC quickly and effectively with engineering analysis. Compared with popular statistical methods, a large number of experiments are avoided, some costs of testing are reduced and the efficiency of testing is enhanced.

Application of Non-destructive Techniques in Evaluation of Wood Properties

With the increase of wood and wood products demands in the world, non-destructive evaluation techniques of wood are more and more important. This article clarifies the importance and present situation of non-destructive evaluation and introduces some instruments about non-destructive evaluation, and some advice and ideas are put forward.

Analysis on Volatiles Release Behavior of Poplar Wood Powder at Different Temperature by TD-GC/MS and Environmental Protection Evaluation

The volatiles release behavior of poplar powder has been studied by TD-GC/MS online technique at different temperatures.The results show that the proportion of main harmful components was higher than that of beneficial in the volatiles of poplar powder at 40℃ and 90℃,the harmful components was 1.7 times higher than beneficial components. The proportions of main beneficial and harmful components were equivalent at 60℃,while the main beneficial components was 5.42 times higher than that of harmful.Taking poplar wood powder as substrate to prepare wood powder-based composites by high-pressure no-gel molding compaction between the temperature of lignin softening point and wood materials carbonization(about 150-180℃) can present a satisfactory environmental friendliness.

Terahertz Spectroscopic Characterization and Thickness Evaluation of Internal Delamination Defects in GFRP Composites

The use of terahertz time-domain spectroscopy(THz-TDS)for the nondestructive testing and evaluation(NDT&E)of materials and structural systems has attracted significant attention over the past two decades due to its superior spatial resolution and capabilities of detecting and characterizing defects and structural damage in non-conducting materials.In this study,the THz-TDS system is used to detect,localize and evaluate hidden multi-delamination defects(i.e.,a three-level multi-delamination system)in multilayered GFRP composite laminates.To obtain accurate results,a wavelet shrinkage de-noising algorithm is used to remove the noise from the measured time-of-flight(TOF)signals.The thickness and location of each delamination defect in the z-direction(i.e.,through-the-thickness direction)are calculated from the de-noised TOF signals considering the interaction between the pulsed THz waves and the different interfaces in the GFRP composite laminates.A comparison between the actual and the measured thickness values of the delamination defects before and after the wavelet shrinkage denoising process indicates that the latter provides better results with less than 3.712%relative error,while the relative error of the non-de-noised signals reaches 16.388%.Also,the power and absorbance levels of the THz waves at every interface with different refractive indices in the GFRP composite laminates are evaluated based on analytical and experimental approaches.The present study provides an adequate theoretical analysis that could help NDT&E specialists to estimate the maximum thickness of GFRP composite materials and/or structures with different interfaces that can be evaluated by the THz-TDS.Also,the accuracy of the obtained results highlights the capabilities of the THz-TDS for the NDT&E of multilayered GFRP composite laminates.

基于红外热成像的古建筑墙内暗柱材料缺失检测

【目的】墙内暗柱是木结构古建筑的重要承重构件之一,因其处于潮湿和缺乏通风的环境,故多存在腐朽及由严重腐朽导致的材料缺失等缺陷,容易失去原有的承载能力和稳定性。墙内暗柱自身构造导致现有的检测手段受限,易造成不可逆的损坏。故本研究基于红外热成像原理开展墙内暗柱材料缺失缺陷检测理论与试验研究,以期为基于红外热成像的墙内暗柱缺陷状况无损检查方法的建立奠定部分前期基础。【方法】首先,从理论角度探讨古建筑墙内暗柱传热过程,推导稳态下木柱区域与纯墙体区域的温度公式,分析影响木柱材料缺失缺陷区域温度变化的因素;然后,建立试验模型,进行墙内暗柱缺陷红外检查试验,采集红外图像;最后,通过分析所获得的红外热图,探讨墙内暗柱材料缺失缺陷大小与墙体表面温度分布之间的关系。【结果】(1)理论研究表明:由于木材的横向导热系数远小于墙体导热系数,加热面加热温度相同的情况下,木柱墙体外表面所对应的温度偏低;墙内暗柱的检测效果主要受到缺陷尺寸,即缺陷高度、缺陷深度的影响。(2)试验结果表明:在稳态热传导下,木柱处的墙体外表面温度要低于纯墙体,即木柱处红外图像的颜色更浅;木柱缺陷的存在会使缺陷处墙体表面温度变高,红外图像颜色变深;木柱缺陷高度越大,缺陷导致的高温范围越大;木柱缺陷深度越大,缺陷区域温度值越高。(3)在非稳态热传导下,木柱中线温差分别与木柱缺陷高度(R^(2)≥0.964)、深度(R^(2)≥0.951)呈极强的正相关。(4)在木柱缺陷较小的情况下,墙体表面温度不因缺陷的存在而发生明显改变。【结论】木柱的缺陷高度与深度是影响缺陷红外热成像检测效果的主要因素,红外热成像法应用于古建筑墙内暗柱材料缺失缺陷的筛查与评估是可行的。

无损检测指标与木材横纹局部抗压强度和密度的相关性

【目的】探索不同类型和数量的无损检测(NDT)指标与木材横纹局部抗压强度和密度的相关性差异,确定最优NDT指标组合,为基于无损检测手段评估木材横纹局部抗压强度和密度的研究提供参考。【方法】以某典型藏式古建筑木结构梁构件为研究对象,锯解得到横纹局部抗压无疵试样。通过物理力学试验和NDT试验,获得无疵试样的密度ρ、横纹局部抗压强度f_(lc),以及顺纹应力波速v_(l)、横纹应力波速v和微钻阻力F,计算不同NDT指标或指标组合与ρ、f_(lc)的线性相关系数,进而对比讨论。【结果】(1)使用单一NDT指标预测ρ时,v_(l)效果较好,两者相关系数绝对值为0.662,补充微钻阻力均值Fm后可提高15.56%,达到0.765;使用单一NDT指标预测f_(lc)时,Fm效果较好,两者相关系数为0.526,在此基础上补充横纹应力波速均值v_(m),二者相关系数提升26.80%,达到0.667,进一步补充v_(l)后相关系数继续提升7.20%,达到0.715。(2)当两组NDT指标中的基本指标构成一致时,即便基本指标的形式存在差异,两组NDT指标与被预测参数的相关系数也近似。(3)当两个与被预测参数相关性较好的NDT指标组合时,相关系数可能进一步提高;当相关性较好的指标与较差的指标组合时,相关系数接近于前者;当相关性较差的指标与不相关指标组合时,相关系数可能大幅提升,也可能仍然较低;当两个均不显著相关的指标组合时,指标组合与被预测参数仍不具有显著相关性。【结论】确定合理的NDT指标比一味增加指标数量对相关系数的提高影响更大。综合考虑相关系数提升效果以及由此可能增加的测试工作量,预测木材密度和横纹局部抗压强度时建议分别使用“v_(l),F_(m)”和“F_(m),v_(m)”的NDT指标组合。

生长和木材性状耦合评价红松半同胞家系

红松(Pinus koraiensis)是东北地区重要的果材兼用树种,但由于生长周期长,遗传改良进展缓慢,为评价和筛选优质红松种质资源,以吉林省永吉县西阳林木种子园内36个20年生红松半同胞家系为材料,对其生长性状和木材性状进行测定。方差分析结果表明,各性状在家系间差异均达显著水平(P<0.01),各性状表型变异系数为5.89%~45.21%;除通直度(0.46)外,其他性状的家系遗传力均超过0.5,属于高遗传力。相关分析结果表明,树高、胸径等生长性状间均达极显著正相关水平(r>0.663),木材性状间半纤维素、纤维素和综纤维素含量间达显著相关水平,而生长性状与木材性状间仅纤维素含量、综纤维素含量与部分生长性状呈显著负相关。主成分分析结果表明,14个性状构成5个主成分,累计贡献率为79.24%。利用综合评价法对36个半同胞家系进行评价,以10%的入选率,依据生长性状,初步筛选3个优良家系(家系PK61、PK29和PK22),各生长性状遗传增益为6.41%~33.91%;依据木材性状,初步筛选3个优良家系(家系PK16、PK78和PK10),各木材性状遗传增益为1.08%~6.72%;结合生长和木材性状初步筛选出3个优良家系(家系PK61、PK29和PK44),各指标遗传增益为0.27%~37.28%。该研究选出的优良家系可为红松良种选用提供基础。

基于激光超声的铝合金组织性能无损检测研究

目前对铝合金析出相和力学性能的检测主要采用扫描电镜(SEM)、透射电镜(TEM)、万能试验机等方式,费时费力且属于破坏性检测。采用激光超声无损检测技术对Al-Cu-Mg铝合金进行检测,通过变分模态分解法(Variational Modal Decomposition,VMD)对时域下的激光超声信号进行降噪处理,得到激光超声信号的衰减系数和声速等特征值,同时采用扫描电镜、电子背散射衍射(EBSD)、静拉伸实验获得Al-Cu-Mg铝合金的析出相和力学性能,将激光超声信号特征值与Al-Cu-Mg铝合金的析出相和力学性能进行耦合。结果发现:激光超声信号特征值与Al-Cu-Mg铝合金的析出相、晶粒尺寸、屈服强度以及显微硬度有较好的相关性。这为Al-Cu-Mg铝合金的微观组织和力学性能快速无损检测提供了一种新方法。

Enhanced air-coupled impact echo technique by phase analysis of signals from multiple sensors

This paper presents an air-coupled impact echo(IE)technique that relies on the phase spectrum of the collected data to find the frequencies corresponding to the reflections from delaminations.The proposed technique takes advantage of the fact that the IE compression wave is not a propagating wave,but it is the 1st order symmetrical(S1)mode Lamb wave at zero group velocity(S1-ZGV).Therefore,it searches the phase spectra of the data collected by multiple sensors to locate the frequency corresponding to the lowest phase difference.As a result,the technique reduces the effect of propagating waves,including the direct acoustic wave and ambient noise.It is named the Constant Phase IE(CPIE).The performance of the CPIE is experimentally compared with the regular amplitude spectrum-based IE technique and two other multisensor IE techniques.The CPIE shows a performance advantage,especially in a noisy environment.

马大相思无性系材性变异研究与综合评价

研究马大相思无性系材性性状遗传变异情况并综合评价其优良无性系,以期为马大相思工业用材林定向培育和木材利用提供理论依据。测定广东四会大南山林场马大相思5年生9个无性系材性性状(木材基本密度、木材纤维形态、木材组织比量),对测得的12个材性性状进行遗传变异分析、相关性分析和聚类分析,并利用主成分分析法综合评价马大相思9个无性系木材品质。结果表明:12个材性性状的变异系数在2%~14%之间,其中腔径比的变异系数最小,导管比量的变异系数最大,基本平均密度为0.506g·cm^(-3),变异幅度为0.459~0.569g·cm^(-3);各材性性状指标间存在不同程度的相关性。主成分分析提取了3个主成分,累积贡献率为85.0%,基本可以代表全部的遗传信息。根据3个主成分得分和相应的权重进行线性加权,建立了马大相思9个无性系木材品质综合评价模型,综合得分排名前三的是2号、8号和9号无性系;聚类分析将马大相思9个无性系分为3类,与主成分分析结果基本一致。

槽钢加固上海市南市区图书馆旧址整体移位数值分析及其关键部位变形监测

石库门里弄住宅是近现代重要史迹及沪上代表性建筑,展示着特定时期城市文化的沉淀。以上海市南市区图书馆旧址工程为例,采用槽钢内撑外拉的方式对整体结构进行了加固,利用既有建筑整体移位技术对该砖-木混合结构进行了顶升和平移,采用位移传感器监测了结构在平移过程中关键部位的位移响应;采用ABAQUS有限元软件建立了上海市南市区图书馆旧址工程的整体有限元模型,得到了结构在顶升、平移过程中关键部位的位移响应,并将模拟结果与实际位移监测结果进行了对比;基于验证的有限元模型,开展了参数分析研究,分析了顶升和平移速率及地面平整度对结构位移响应的影响,评估了结构的受力和安全状态。研究可为城市更新中历史建筑的整体移位技术提供参考。

应力波和超声波检测在木拱廊桥安全评估中的应用

木拱廊桥是木结构古建筑中重要的文化遗产,现存的部分木拱廊桥仍在使用中.为保护木拱廊桥,考虑各种复杂的环境因素和结构条件,将应力波和超声波检测技术应用于真实环境下的木拱廊桥检测中.挑选福州市闽侯县远济桥的承重木柱作为研究对象,针对木柱内部缺陷采用应力波检测与超声波检测.检测结果表明应力波和超声波检测木材缺陷时,超声波的检测精度更高,二者检测结果存在相似性;远济桥检测样本的承重木柱存在空洞、裂纹、虫蛀等缺陷,建议对远济桥的安全性进行优化和改进.基于木拱廊桥所处环境的实际情况,利用应力波和超声波检测相对照的检测方法,提出针对木拱廊桥的安全性等级进行划分,使应力波和超声波检测技术更好地应用于木拱廊桥的保护工程中.

不同菌材栽培天麻的氨基酸含量分析及营养评价

目的:探究不同菌材对不同品种天麻品质的影响。方法:以青冈和旱冬瓜作为菌材栽培的乌天麻(Gastrodia elata Bl.f.glauca)和红天麻(Gastrodia elata Bl.f.elata)为研究对象,进行了天麻素、重金属元素、矿质元素及氨基酸种类和含量测定,结合氨基酸比值系数法并参考全鸡蛋蛋白模式和FAO/WHO模式进行营养价值分析。结果:青冈和旱冬瓜栽培的天麻中天麻素含量基本无差异,氨基酸总量在339.52~1365.71 mg/100 g。药用氨基酸和呈味氨基酸含量丰富,鲜甜味氨基酸含量较高,在整个氨基酸中所占比例可达73.73%~83.09%。2号旱冬瓜栽种的乌天麻和3号青冈栽种的红天麻中药用氨基酸含量分别为941.13 mg/100 g和992.91 mg/100 g,在氨基酸总量中所占比例分别达74.71%和72.70%,其中含量最多的是天冬氨酸和谷氨酸。结论:不同的天麻品种在栽培时可选择相应适宜的菌材,天麻中氨基酸含量的分析可作为评价天麻营养价值的重要指标,也可作为衡量天麻栽培中菌材选择的重要依据。

基于红外光谱结合化学计量学的美洲大蠊精制物CⅡ-3无损质量评价方法

目的:以美洲大蠊精制物CⅡ-3为研究对象,基于红外光谱结合化学计量学建立其品质无损的简易评价方法。方法:采用红外光谱法建立10批CⅡ-3样品的红外光谱,并进行基线矫正、纵坐标归一化和15点平滑等预处理方法优化光谱图;运用Origin 9.1软件对光谱数据进行表征和解析,建立10批CⅡ-3样品的指纹图谱,并进行相似度分析和主成分分析。结果:10批CⅡ-3样品红外光谱的官能团区主要特征峰为3300、2960、2930、1660、1630、1550、1450、1390 cm-1,指纹区主要特征峰为1240、1080、621、546 cm-1。不同批次CⅡ-3样品红外光谱的峰形、峰位和峰强相似,相关系数均在0.960以上。主成分分析结果显示10批CⅡ-3样品聚为一类。结论:该方法操作简单、专属性强、不破坏样品,可实现CⅡ-3样品的无损质量评价。

基于波干涉技术的早龄混凝土强度及刚度监测方法研究

精准监测早龄期混凝土的强度和刚度,对于装配式建筑的施工和应用至关重要。文中提出一种无损技术,用于监测早龄期混凝土强度和刚度的发展过程。首先在混凝土试样浇注后进行水或空气养护,之后通过超声波技术获取早龄期混凝土中波的相对速度变化,分析动态弹性模量和抗压强度随养护龄期的变化影响。结果表明,混凝土养护龄期对相对速度影响较大,养护28 d后,水养护和空气养护试样的相对速度变化分别逐渐增加到9.0%和5.3%;双峰测试技术和伸缩测试技术2种固化方法的相对速度变化值相似,窗宽几乎不会影响相对速度变化的估算;固化28 d时,水固化试样的抗压强度比空气固化试样高19.7%,动态弹性模量比空气固化试样高13.5%,水固化试样的相对速度变化高出约3.9%,波干涉测量技术能够有效区分2种固化方法的影响;相对抗压强度和相对弹性模量均与相对速度变化间存在较强线性相关性。

基于“双碳”目标的木材节约代用综合效能评价方法研究

该文立足我国碳达峰、碳中和目标,从森林这一实现该目标的主体为对象,定性分析了传统木材节约代用思路和“双碳”背景下的木材节约代用思路。进而以木材碳效益、净化空气效益等为要素建立了木材节约代用的效益分析模型,以木材代用碳成本、经济效益成本为要素等建立了木材节约代用的成本分析模型。基于“双碳”目标,建立了木材节约代用成本效益分析综合效能评价模型。最后,以木制筷子的塑料化替代为例,利用木材节约代用成本效益分析综合效能评价模型计算得到:塑料制品替代木筷消耗的1 m^(3)林木时将增加0.96 t碳,应该摒弃这种传统的木材节约代用路径。

Recent developments in photoacoustic imaging and sensing for nondestructive testing and evaluation

Photoacoustic(PA)imaging has been widely used in biomedical research and preclinical studies during the past two decades.It has also been explored for nondestructive testing and evaluation(NDT/E)and for industrial applications.This paper describes the basic principles of PA technology for NDT/E and its applications in recent years.PA technology for NDT/E includes the use of a modulated continuous-wave laser and a pulsed laser for PA wave excitation,PA-generated ultrasonic waves,and all-optical PA wave excitation and detection.PA technology for NDT/E has demonstrated broad applications,including the imaging of railway cracks and defects,the imaging of Li metal batteries,the measurements of the porosity and Young’s modulus,the detection of defects and damage in silicon wafers,and a visualization of underdrawings in paintings.

Analytical model of tilted driver–pickup coils for eddy current nondestructive evaluation

A driver-pickup probe possesses better sensitivity and flexibility due to individual optimization of a coil.It is fre-quently observed in an eddy current(EC)array probe.In this work,a tilted non-coaxial driver-pickup probe above a multilayered conducting plate is analytically modeled with spatial transformation for eddy current nondestructive evalua-tion.Basically,the core of the formulation is to obtain the projection of magnetic vector potential(MVP)from the driver coil onto the vector along the tilted pickup coil,which is divided into two key steps.The first step is to make a projection of MVP along the pickup coil onto a horizontal plane,and the second one is to build the relationship between the pr,ojected MVP and the MVP along the driver coil.Afterwards,an analytical model for the case of a layered plate is established with the reflection and transmission theory of electromagnetic fields.The calculated values from the resulting model indicate good agreement with those from the finite element model(FEM)and experiments,which validates the developed analytical model.

Evaluation of fracture damage of SUS306 structural steel using ultrasonic testing

High frequency ultrasonic nondestructive testing was conducted using a direct contact method for SUS306 stainless steel treated by high temperature and fracture tensile tests. Reflected ultrasonic echoes were analyzed. The relationships between the ultrasonic attenuation coefficient, strength of backscattering wave and the elongation at break of the samples were obtained. The damages were evaluated by using these results together with the analysis of microstructure and mechanics of the tested material.