连续压缩载荷下木材力学性能及微观结构变化定量表征
|
摘要
木材与木质材料的力学性能在很大程度上取决于其内部结构特征。为了更好的了解和掌握木材力学性能与其微观结构的关系,本论文采用自主研发的原位检测平台,研究了不同条件下木材受连续压缩时力学性能及其微观结构的实时变化情况,并着重分析了两者之间的相互关系。
本论文首先归纳了原位检测方法在木材组织力学水平上的应用,分析了现有原位检测技术存在的问题及可实现的解决方法;随后重点介绍了自主研发的原位检测平台的构架及实施方式、图像采集系统等重要部位的工作原理;并借助具体试验,综合分析了该平台可实现的技术特点;然后通过该原位检测平台,以人工林杉木(Cunninghamia lanceolata)小试样[5mm(L)×X mm(R)×5mm(T)]为研究对象,系统研究了不同生长轮早材在连续横纹径向压缩时的力学行为及其微观结构变化;并进一步研究了不同加载速度、温度和含水率条件下,早材在连续加载时的力学性能及其与内部微观结构变化的关系。
本论文的主要研究结论如下:
(1)自主研发的原位检测平台包括两个系统,一是加载系统,二是图像采集系统,两个系统通过时间参数并行统一。图像采集系统能在连续加载的过程中自动聚焦并实时拍摄木材变形的照片,并借助于测量与计算软件对照片进行定量分析,从而实现木材的力学性能及其微观结构变化的动态检测。
(2)杉木各生长轮间早材横纹径向抗压屈服强度(σc)和横纹径向抗压弹性模量(Ec)从心材到边材呈逐渐减小趋势。不同部位(心材、边心材交界和边材)间σc与Ec存在显著的差异性。对三个部位(心材、边心材交界和边材)连续受压产生首次屈服永久变形(塑性变形)的微观结构位置进行定量研究结果表明:第7生长轮与第11生长轮出现首次屈服变形的位置一致,均在距被加载表面第15-20层早材细胞处(平均距离分别为643μm和689μm);而第17生长轮在距被加载表面第5-10层早材细胞处(平均距离为153μm)产生首次屈服变形。不同生长轮间早材微观结构的不同影响其横纹抗压力学性能在径向方向上的变化。
(3)在不同加载速度(1mm/min,10mm/min和50mm/min)条件下,早材产生首次屈服变形的位置与被加载表面之间平均距离分别为689μm,166μm和23μm。不同加载速度下早材小试样的σc与Ec均差异显著,与试样产生首次屈服变形的位置有关。低速加载下(1mm/min),木材内部最脆弱部位首先产生屈服变形,得到的σc与Ec相对较小,平均值分别为3.16MPa和45.79MPa;较高加载速度下(10mm/min和50mm/min),木材内部非最脆弱部位首先产生屈服变形,得到的σc与Ec相对较大,平均值分别为3.71MPa和56.04MPa,4.51MPa和75.53MPa。
(4)在不同温度(-20OC、20OC、60oC、80OC和120OC)条件下,早材σc与Ec的变化趋势一致。在负温度下(-20OC)得到σc与Ec均比正温度下的σc与Ec大。一般来说,随着温度的升高,σc与Ec逐渐减小。同时,不同温度下σc与Ec差异比较显著。较低温度(≤60oC)下与较高温度(≥80 oC)下,早材的破坏方式不同。温度≤60oC时,趋于刚性屈服;温度≥80OC时,趋于柔性屈服;不同温度(-20OC、20OC和60OC)下,出现首次屈服变形的位置相同,均为距被加载表面第17-20层早材细胞处(距被加载表面的平均距离分别为667μm、689μm和643μm),表明在较低温度(≤60OC)范围内,温度的变化并未改变木材内部最脆弱部位的位置,但最脆弱部位木材的力学性能发生变化。
(5)在不同含水率(绝干、气干与饱水状态)条件下,早材σc与Ec差异均显著。σc与Ec随着含水率增加呈逐渐减小的趋势。由绝干到气干状态,早材产生首次屈服变形的位置未发生变化,均在距被加载表面第17-20层早材细胞处(距被加载表面的平均距离分别为664μm和689μm);在饱水状态下,加载过程中压出的水分影响微观结构的拍摄和检测。在不同含水率条件下,木材产生首次屈服变形时的破坏方式不同。在绝干和气干条件下,趋于刚性屈服;而在饱水条件下,趋于柔性屈服。在绝干与气干条件下,含水率变化并未改变木材内部最脆弱部位的位置,但最脆弱部位木材的力学性能发生变化。
综上所述,本研究通过自主研发的原位检测平台,实现了连续加载条件下木材微观结构变化的实时检测,并较好解释了不同条件下木材横纹径向压缩力学性能变化的解剖学原因,为连续加载条件下木材力学行为的有效检测和预测提供了技术基础和理论依据。
Mechanical properties of wood and wood products are highly depended upon the interior structural features. Based on this theory, this paper introduced research methods and tendency of testing on wood mechanical properties, then introduced the applying of in-situ inspection on wood tissue mechanical level and analyzed the existing and unsolved problems of the present in-situ inspection system. A self-developed in-situ inspection platform had been developed, and then the structures of the platform and its implement methods were descried in detail. The mechanism of auto-focus photo-shooting system was given in the paper. By means of wood mechanical tests, detailed descriptions of the platform on how to achieve the variable technical characteristics had been obtained, and technical advantages of this platform were comprehensive analyzed.
By virtue of the self-developed in-situ inspection system and earlywood simples in each growth ring of Chinese fir, wood mechanical behavior variations under continuous compressive loading and auto-focused in-situ inspection on microstructure characteristics of wood deformation had been systematically analyzed. Meanwhile, through the change of outer environment conditions, i.e. loading rate, temperature and moisture conditions, variations on mechanical properties in these situations were obtained, and quantitative analysis on microstructure variances were investigated with the help of the measuring and calculating software. The main conclusions of the paper are as follows:
(1) The in-situ inspection system can be divided into two parts, one part is the loading system, and the other part is the picture-collection system. The two parts can be combined by the parameter of time. The picture collection system can automatically take photos of materials’surface deformation during the loading process. Meanwhile, by means of the quantitative calculation and measuring on the photos, the system can directly and precisely achieve the simulations of wood mechanical properties.
(2) By using early wood samples in each growth ring, the result that yield strength and modulus of elasticity under radial compression are decreasing from heartwood to sapwood. Significant variations were observed among mechanical properties of different parts, i.e. heartwood, transition wood and sapwood. The in-situ inspection on wood micro-structural deformation and quantitative analysis results showed that the first yield positions of both heartwood and transition wood occurred at 15-20 cell layer of earlywood (643μm and 689μm from the surface of loading compression, respectively), while the first yield position of sapwood occurred at 5-10 cell layer of earlywood (153μm from the surface of loading compression).
(3) The yield strength and modulus of elasticity at different loading rates are relevant to the first yield position. Loading rates of 1mm/min, 10mm/min and 50mm/min was adopted respectively for mechanical testing of typical softwood of Chinese fir (Cunninghamia lanceolata). The results indicated that the variations of wood mechanical performance at different loading rates were generated from the different position of the first yield point (689μm, 166μm and 23μm, respectively); the in-situ inspecting system could accurately characterize the variations of microstructure deformation. Furthermore, the microstructure characteristics could be used to explain mechanical behavior of wood suffered from different loading rates.
(4) Mechanical properties, i.e. yield strength and modulus of elasticity, have the same tendency with the variation of temperature conditions. Mechanical properties at negative temperature are higher than that of at positive temperatures. Generally speaking, yield strength and modulus of elasticity are decreasing with the increase of temperature. The fracture behaviors are different at relatively low (≤60OC)and high temperature(s≥80OC).At relatively low temperatures (including -20OC,20OC and 60OC), the fracture behavior is tend to in a rigid way; While at relatively high temperatures (including 80OC and 120OC), the fracture behavior is tend to in a flexible way. At different temperatures(-20OC,20OC and 60OC), the first yield position is similar, which occurred at 15-20 cell layer of the earlywood (667μm,689μm and 643μm from the surface of loading compression, respectively), which inferred that the temperature had not affect the most vulnerable area in the sample.
(5) The yield strength and modulus of elasticity are variable at different moisture conditions. Generally, the yield strength and modulus of elasticity are decreasing from fully dry to air-dry and then to fiber saturate condition. The first yield positions were similar at air-dry and full-dry moisture conditions, which occurred at 15-20 cell layer of the earlywood (664μm and 689μm from the surface of loading compression, respectively); while at firber saturate moisture condition, the free water in cell walls or cavities was compressed out which made it impossible to see the fracture surface.The fracture behaviors are different between the relatively low (fully-dry and air-dry)and high moisture conditions(fiber saturate).At relatively low moisture conditions, the fracture behavior is tend to be in a rigid way; While at relatively high moisture condition, the fracture behavior is tend to be in a flexible way.
Above all, the self-developed inspecting method can help us understand and master the microstructure characteristics of wood deformation under continuous compressive loading, and can explain the variations of mechanical properties during continuous compression. The system can realize the effective anticipations of wood mechanical properties suffered from various compression conditions, and can quantitatively analyze the variance of wood microstructure characteristics.
本论文首先归纳了原位检测方法在木材组织力学水平上的应用,分析了现有原位检测技术存在的问题及可实现的解决方法;随后重点介绍了自主研发的原位检测平台的构架及实施方式、图像采集系统等重要部位的工作原理;并借助具体试验,综合分析了该平台可实现的技术特点;然后通过该原位检测平台,以人工林杉木(Cunninghamia lanceolata)小试样[5mm(L)×X mm(R)×5mm(T)]为研究对象,系统研究了不同生长轮早材在连续横纹径向压缩时的力学行为及其微观结构变化;并进一步研究了不同加载速度、温度和含水率条件下,早材在连续加载时的力学性能及其与内部微观结构变化的关系。
本论文的主要研究结论如下:
(1)自主研发的原位检测平台包括两个系统,一是加载系统,二是图像采集系统,两个系统通过时间参数并行统一。图像采集系统能在连续加载的过程中自动聚焦并实时拍摄木材变形的照片,并借助于测量与计算软件对照片进行定量分析,从而实现木材的力学性能及其微观结构变化的动态检测。
(2)杉木各生长轮间早材横纹径向抗压屈服强度(σc)和横纹径向抗压弹性模量(Ec)从心材到边材呈逐渐减小趋势。不同部位(心材、边心材交界和边材)间σc与Ec存在显著的差异性。对三个部位(心材、边心材交界和边材)连续受压产生首次屈服永久变形(塑性变形)的微观结构位置进行定量研究结果表明:第7生长轮与第11生长轮出现首次屈服变形的位置一致,均在距被加载表面第15-20层早材细胞处(平均距离分别为643μm和689μm);而第17生长轮在距被加载表面第5-10层早材细胞处(平均距离为153μm)产生首次屈服变形。不同生长轮间早材微观结构的不同影响其横纹抗压力学性能在径向方向上的变化。
(3)在不同加载速度(1mm/min,10mm/min和50mm/min)条件下,早材产生首次屈服变形的位置与被加载表面之间平均距离分别为689μm,166μm和23μm。不同加载速度下早材小试样的σc与Ec均差异显著,与试样产生首次屈服变形的位置有关。低速加载下(1mm/min),木材内部最脆弱部位首先产生屈服变形,得到的σc与Ec相对较小,平均值分别为3.16MPa和45.79MPa;较高加载速度下(10mm/min和50mm/min),木材内部非最脆弱部位首先产生屈服变形,得到的σc与Ec相对较大,平均值分别为3.71MPa和56.04MPa,4.51MPa和75.53MPa。
(4)在不同温度(-20OC、20OC、60oC、80OC和120OC)条件下,早材σc与Ec的变化趋势一致。在负温度下(-20OC)得到σc与Ec均比正温度下的σc与Ec大。一般来说,随着温度的升高,σc与Ec逐渐减小。同时,不同温度下σc与Ec差异比较显著。较低温度(≤60oC)下与较高温度(≥80 oC)下,早材的破坏方式不同。温度≤60oC时,趋于刚性屈服;温度≥80OC时,趋于柔性屈服;不同温度(-20OC、20OC和60OC)下,出现首次屈服变形的位置相同,均为距被加载表面第17-20层早材细胞处(距被加载表面的平均距离分别为667μm、689μm和643μm),表明在较低温度(≤60OC)范围内,温度的变化并未改变木材内部最脆弱部位的位置,但最脆弱部位木材的力学性能发生变化。
(5)在不同含水率(绝干、气干与饱水状态)条件下,早材σc与Ec差异均显著。σc与Ec随着含水率增加呈逐渐减小的趋势。由绝干到气干状态,早材产生首次屈服变形的位置未发生变化,均在距被加载表面第17-20层早材细胞处(距被加载表面的平均距离分别为664μm和689μm);在饱水状态下,加载过程中压出的水分影响微观结构的拍摄和检测。在不同含水率条件下,木材产生首次屈服变形时的破坏方式不同。在绝干和气干条件下,趋于刚性屈服;而在饱水条件下,趋于柔性屈服。在绝干与气干条件下,含水率变化并未改变木材内部最脆弱部位的位置,但最脆弱部位木材的力学性能发生变化。
综上所述,本研究通过自主研发的原位检测平台,实现了连续加载条件下木材微观结构变化的实时检测,并较好解释了不同条件下木材横纹径向压缩力学性能变化的解剖学原因,为连续加载条件下木材力学行为的有效检测和预测提供了技术基础和理论依据。
Mechanical properties of wood and wood products are highly depended upon the interior structural features. Based on this theory, this paper introduced research methods and tendency of testing on wood mechanical properties, then introduced the applying of in-situ inspection on wood tissue mechanical level and analyzed the existing and unsolved problems of the present in-situ inspection system. A self-developed in-situ inspection platform had been developed, and then the structures of the platform and its implement methods were descried in detail. The mechanism of auto-focus photo-shooting system was given in the paper. By means of wood mechanical tests, detailed descriptions of the platform on how to achieve the variable technical characteristics had been obtained, and technical advantages of this platform were comprehensive analyzed.
By virtue of the self-developed in-situ inspection system and earlywood simples in each growth ring of Chinese fir, wood mechanical behavior variations under continuous compressive loading and auto-focused in-situ inspection on microstructure characteristics of wood deformation had been systematically analyzed. Meanwhile, through the change of outer environment conditions, i.e. loading rate, temperature and moisture conditions, variations on mechanical properties in these situations were obtained, and quantitative analysis on microstructure variances were investigated with the help of the measuring and calculating software. The main conclusions of the paper are as follows:
(1) The in-situ inspection system can be divided into two parts, one part is the loading system, and the other part is the picture-collection system. The two parts can be combined by the parameter of time. The picture collection system can automatically take photos of materials’surface deformation during the loading process. Meanwhile, by means of the quantitative calculation and measuring on the photos, the system can directly and precisely achieve the simulations of wood mechanical properties.
(2) By using early wood samples in each growth ring, the result that yield strength and modulus of elasticity under radial compression are decreasing from heartwood to sapwood. Significant variations were observed among mechanical properties of different parts, i.e. heartwood, transition wood and sapwood. The in-situ inspection on wood micro-structural deformation and quantitative analysis results showed that the first yield positions of both heartwood and transition wood occurred at 15-20 cell layer of earlywood (643μm and 689μm from the surface of loading compression, respectively), while the first yield position of sapwood occurred at 5-10 cell layer of earlywood (153μm from the surface of loading compression).
(3) The yield strength and modulus of elasticity at different loading rates are relevant to the first yield position. Loading rates of 1mm/min, 10mm/min and 50mm/min was adopted respectively for mechanical testing of typical softwood of Chinese fir (Cunninghamia lanceolata). The results indicated that the variations of wood mechanical performance at different loading rates were generated from the different position of the first yield point (689μm, 166μm and 23μm, respectively); the in-situ inspecting system could accurately characterize the variations of microstructure deformation. Furthermore, the microstructure characteristics could be used to explain mechanical behavior of wood suffered from different loading rates.
(4) Mechanical properties, i.e. yield strength and modulus of elasticity, have the same tendency with the variation of temperature conditions. Mechanical properties at negative temperature are higher than that of at positive temperatures. Generally speaking, yield strength and modulus of elasticity are decreasing with the increase of temperature. The fracture behaviors are different at relatively low (≤60OC)and high temperature(s≥80OC).At relatively low temperatures (including -20OC,20OC and 60OC), the fracture behavior is tend to in a rigid way; While at relatively high temperatures (including 80OC and 120OC), the fracture behavior is tend to in a flexible way. At different temperatures(-20OC,20OC and 60OC), the first yield position is similar, which occurred at 15-20 cell layer of the earlywood (667μm,689μm and 643μm from the surface of loading compression, respectively), which inferred that the temperature had not affect the most vulnerable area in the sample.
(5) The yield strength and modulus of elasticity are variable at different moisture conditions. Generally, the yield strength and modulus of elasticity are decreasing from fully dry to air-dry and then to fiber saturate condition. The first yield positions were similar at air-dry and full-dry moisture conditions, which occurred at 15-20 cell layer of the earlywood (664μm and 689μm from the surface of loading compression, respectively); while at firber saturate moisture condition, the free water in cell walls or cavities was compressed out which made it impossible to see the fracture surface.The fracture behaviors are different between the relatively low (fully-dry and air-dry)and high moisture conditions(fiber saturate).At relatively low moisture conditions, the fracture behavior is tend to be in a rigid way; While at relatively high moisture condition, the fracture behavior is tend to be in a flexible way.
Above all, the self-developed inspecting method can help us understand and master the microstructure characteristics of wood deformation under continuous compressive loading, and can explain the variations of mechanical properties during continuous compression. The system can realize the effective anticipations of wood mechanical properties suffered from various compression conditions, and can quantitatively analyze the variance of wood microstructure characteristics.
引文
[1]成俊卿.木材学.北京:中国林业出版社, 1985.
[2] Salmen L, Burgert I. cell wall features with regard to mechanical performance. Holzforschung, 2009,63(1):121-129.
[3] Hofstetter K, Gamstedt K E . Hierarchical modeling of microstructural effects on mechanical properties of wood.A review.Holzforschung, 2009,63(1):130-138.
[4] Bodig J. The effect of anatomy on the initial stress-strain relationship in transverse compression. Forest Product Journal. 1965, 15(5):197-202.
[5] Tabarsa T, Chui Y H. Characteristic microscopic behavior of wood under transverse compression part 1: method and preliminary test results. Wood and Fiber Science.2000, 32(2):144-152.
[6] Gong, M., Li, L., Chui, Y.H., Li, K.C, and Yuan, N.X. 2008. Modelling of recovery of residual stresses in densified softwoods. Proceedings of the 10th World Conference on Timber Engineering. Miyazaki, Japan. On Proceedings CD.
[7] Burgert I, keckes J, Fruhmann K, Fratzl P, Tschegg S. Acomparison of two techniques for wood fiber isolation-evaluation by tensile tests on single fibers with different micro fibril angle. Plant Biol, 2002, 4:9-12.
[8] Burgert, I.,Gierlinger,N., Zimmermann,T. Poperties of chemically and mechanically isolated fibers of spuce(Picea abies L.karst).Part I: structural and chemical characterization. Holzforschung, 2005,50:240-246.
[9] Burgert I, Fruhmann K, Keckes J. Structure-function relationships of four compression wood types: micromechanical properties at the tissue and fiber level. Trees, 2004, 18: 480-485.
[10] Tabarsa T, Chui Y Hi. Characteristic microscopic behavior of wood under transverse compression part 2: effects of species and loading direction. Wood and Fiber science. 2001, 33(2):223-232.
[11] Gindl W. Comparing mechanical properties of normal and compression wood in Norway spruce: the role of lignin in compression parallel to the grain. Holzforschung,2002,56:395-401.
[12] Gindl W, Schoberl T. The significance of the elastic modulus of wood cell walls obtained fromnanoidentation measurements. Composites Part A: Appl. Sci. Manufac, 2004,35:1345-1349.
[13] Wimmer R, Lucas B N and Tsui T Y. Longitudinal hardness and Young’s modulus of spruce tracheid secondary walls using nanoindentation technique. Wood Science and Technology, 1997, 31(2):131-141.
[14] Choi, D., J.L. Thorpe, W.A. Quantification of compression failure propagation in wood using digital image pattern recognition. Forest Prod.J, 1996, 46(10):87-93.
[15] Mott,L., S.M. Schaler and L.H. Groom. A technique to measure strain distributions in single wood pulp fibers. Wood and Fiber Science 1996,28(4):429-437.
[16] Mark R E. Cell wall mechanics of tracheids Yale University. Press 1967.
[17]中国科学技术协会. 2006-2007力学学科发展报告.北京:中国科学技术出版社,2007
[18] Johansson L, Peng F, Simonson R. Effects of temperature and sulfonation on shear deformation of spruce wood. Wood science and technology, 1997,31:105-117.
[19] Eillis S, Steiner P. The behavior of five wood species in compression. IAWA Journal, 2002,23(2):201-211.
[20] Kohler L, Spatz H C. Micromechanics of plant tissues beyond the linear-elastic range. Planta, 2002,215:33-40.
[21] Singh A P, Anderson C R, Warnes J M. The effect of planning on the microscopic structure of pinus radiata wood cells in relation to penetration of PVA glue. Holz als Roh- und Werkstoff, 2002,60:333-341.
[22] Muller U, Gindl W, Teischinger A. Effects of cell anatomy on the plastic and elastic behavior of different wood species loaded perpendicular to grain. IAWA Journal, 2003,24(2):117-128
[23] Kifetew G, Thuvander F, Berglund L. The effects of drying on wood fracture surfaces form specimens loaded in wet condition. Wood science and technology.1998,32:83-94.
[24] Gong, M., Li, L., Chui, Y.H., Li, K.C, and Yuan, N.X. 2008. Modelling of recovery of residual stresses in densified softwoods. Proceedings of the 10th World Conference on Timber Engineering. Miyazaki, Japan. On Proceedings CD.
[25]刘君良,李坚,刘一星.高温水蒸汽处理固定大青杨木材横纹压缩变形的研究.林业科学,2003.39(1):126-131.
[26]赵钟声,刘一星,井上雅文,东原贵志.水蒸气前处理对杨木等5个树种木材压缩变形恢复率及力学性能影响的研究.林业机械和木工设备, 2003,5: 23-27.
[27]魏新莉,向仕龙,何华.水热预处理对杨木压缩木物理力学性能的影响.木材工业,2004,18(3):20-22.
[28]黄广华,陈瑞英.人工林巨尾桉木材压缩密化的研究.福建林学院学报,2007, 27(4):48-52.
[29]吴振锋,左洪福,邱根良,等.显微镜一种新的自动聚焦算法[J].数据采集与处理. 2000, 15(3): 351-354.
[30]方以,郑崇勋,闫相国.显微镜自动聚焦算法的研究.仪器仪表学报. 2005, 26(12): 1275-1277.
[31] Herajarvi H. Static bending properties of Finnish Birch wood. Wood Sci. Technol, 2004,37:523~530.
[32] Hernandez R E, Koubaa A, Beaudoin M et al. 1998. Selected mechanical properties of fast growing poplar hybrid clones. Wood and Fiber Sci,30(2):138~147.
[33] Schniewind A P. Mechanical behavior and properties of wood. In: Wangaard F F eds. Wood: its structure and properties. Educational modules for materials science and engineering (EMMSE) project, Materials Research Laboratiory, Pennsylvania State University, PA, 1:1979, 233~270.
[34]江泽慧,姜笑梅著. 2008.木材结构与其品质特性的相关性.北京:科学出版社.
[35] Chowdhury MQ, Ishiguri F, Iizuka K Radial variations of wood properties in Casuarina equisetifolia growing in Bangladesh. J Wood Sci ,2009,55:139-143.
[36] Bao FC, Jiang ZH.Wood properties of main tree species from plantation in China. China Forestry Publishing House, Beijing. 1998,4pp. In Chinese.
[37] Andrey S, Berglund LA. Shear coupling effects on stress and strain distributions in wood subjected to transverse compression. Composites Science and Technology, 2007,67 :1362–1369.
[38]戴秋莲.奥贝球铁的冲击断口分析.材料科学与工程,1999,03(1):59-62.
[39]贾江滢,徐家福,富东慧,王忠保,侯振德.加载速率对6020铝合金材料力学性能影响的实验研究[J].实验力学, 2008,23(1):77-83.
[40]方钦志,李慧敏,欧阳小东.加载速率对PC/ ABS拉伸性能的影响.高分子材料科学与工程, 2006,22 (1):131-134.
[41]罗国清,乔生儒,加载速率对3D2C/ SiC不同温度拉伸性能的影响.材料工程, 2003,10:9-10,39.
[42]李华,胡国程,肖俊玲.不同加载速度对热轧带肋钢筋σs、σb测试值的影响.金属材料与冶金工程,2010,01(1):12-14.
[43]张莉,张玉凤,霍立兴.加载速率对结构钢力学性能和断裂韧度的影响.焊接学报, 2003,24 (1):94-96.
[44]龚蒙,徐永吉,唐海波.木材顺拉弹性模量测定方法的研究—加载速度的选择.南京林业大学学报, 1995,19(4):93-96.
[45]朱南峰.加载速度对静曲强度数值的影响.林业科技开发, 1996, 13(3): 25-26
[46]张心安,朱一辛.竹材增强单板层积材的动态与静态弯曲性能.南京林业大学学报(自然科学版), 2006, 30(1):69-71.
[47]江泽慧,任海青,胡一贯,刘刚,阚娅.木材断裂过程的研究.核技术, 2000, 23(8):572-576.
[48]任海青,江泽慧.人工林杉木、马尾松木材的断裂特性.林业科学, 2001, 37(3):118-122.
[49]殷亚方,边明明,刘波,姜笑梅.连续压缩载荷下木材微观结构变化自动检测.建筑材料学报,2011,14(3):442-446.
[50] Johansson L, Peng F, Simonson R. Effects of temperature and sulfonation on shear deformation of spruce wood. Wood science and technology, 1997,31:105-117.
[51] Morookat T,Norimoto M. Influence of thermal softening and degradation on the radial compression behavior of wet spruce. International Journal of wood and wood products, 1998,12(1):45-52.
[52] Boonstra M.J. J.Blomberg. Semi-isostatic densification of heat-treated radiata pine Wood Sci Technol,2007,41:607–617.
[53] B.F.T jeerdsma H.Militz. Chemical changes in hydrothermal treated wood:FTIR analysis of combined hydrothermal and dry heat-treated wood,Holz als Roh-und Werksto,2005,63:102–111.
[54] Seppo Andersson.Ritva Serimaa·Timo PaakkariPekka Saranp Erkki Pesonen.Crystallinity of wood and the size of cellulose crystallites in Norway spruce(Picea abies) J Wood Sci, 2003,49:531–537.
[55] Kentaro Abe·Hiroyuki Yamamoto.Change in mechanical interaction between cellulose microfibril and matrix substance in wood cell wall induced by hygrothermal treatment. J Wood Sci,2006,52:107–110.
[56] Tang Xiaoshu, Zhao Guangjie, Nakao Tetsuya. Changes of Chemical Composition and Crystalline of Compressed Chinese Fir Wood in Heating Fixation. Forestry Studies in China,2008,6(4):39–44.
[57] Grossman, P.U.A. Requirements for a model that exhibits mechano-sorptive behavior. Wood Sci.Technol.1976,10:163-168
[58] Armstrong, L., Kingston, R.S.T. Effect of moisture changes on creep in wood. Nature,1960,18:862-863.
[59] Chaplin, M.. Non linear fracture mechanics in wood . In:proceedings of the international conference on integrated approach to wood structure. Behaviour and application joint meeting of ESWM and COST Action E35, Florence,Italy, Eds. Fioravanti,M., Macchionni. 2006. N.pp.218-227.
[60] Hoffmeyer, P..Failure of wood as influenced by moisture and duration of load. PhD thesis, State University of New York, College of Environmental Science and Forestry Syracuse, New York.1990.
[61] Hankijawi, A., Hunt, D.. Experimental indication of interaction between viscoelastic and mecahano-sorptive creep. Wood Sci. Technol.1998,32:57-80.
[62] Hunt,D., Gril,J.. Evidence of a physical ageing phenomenon in wood. J. Mater. Sci. 1986, 15:80-82.
[63] Navi P., Pitter V.,Plummer CJG. Transient moisture effects on wood creep. Wood Sci. Technol. ,1995, 36:447-462.
[64] Fioravanti M, Sodini N, Navi P. Investigation of the influecne of hemicelluloses on time dependent behavior of wood. In:proceedings of the international conference on integrated approach to wood structure. Behaviour and application joint meeting of ESWM and COST Action E35, Florence,Italy, Eds. Fioravanti,M., Macchionni. 2006. N.pp.190-194.
[2] Salmen L, Burgert I. cell wall features with regard to mechanical performance. Holzforschung, 2009,63(1):121-129.
[3] Hofstetter K, Gamstedt K E . Hierarchical modeling of microstructural effects on mechanical properties of wood.A review.Holzforschung, 2009,63(1):130-138.
[4] Bodig J. The effect of anatomy on the initial stress-strain relationship in transverse compression. Forest Product Journal. 1965, 15(5):197-202.
[5] Tabarsa T, Chui Y H. Characteristic microscopic behavior of wood under transverse compression part 1: method and preliminary test results. Wood and Fiber Science.2000, 32(2):144-152.
[6] Gong, M., Li, L., Chui, Y.H., Li, K.C, and Yuan, N.X. 2008. Modelling of recovery of residual stresses in densified softwoods. Proceedings of the 10th World Conference on Timber Engineering. Miyazaki, Japan. On Proceedings CD.
[7] Burgert I, keckes J, Fruhmann K, Fratzl P, Tschegg S. Acomparison of two techniques for wood fiber isolation-evaluation by tensile tests on single fibers with different micro fibril angle. Plant Biol, 2002, 4:9-12.
[8] Burgert, I.,Gierlinger,N., Zimmermann,T. Poperties of chemically and mechanically isolated fibers of spuce(Picea abies L.karst).Part I: structural and chemical characterization. Holzforschung, 2005,50:240-246.
[9] Burgert I, Fruhmann K, Keckes J. Structure-function relationships of four compression wood types: micromechanical properties at the tissue and fiber level. Trees, 2004, 18: 480-485.
[10] Tabarsa T, Chui Y Hi. Characteristic microscopic behavior of wood under transverse compression part 2: effects of species and loading direction. Wood and Fiber science. 2001, 33(2):223-232.
[11] Gindl W. Comparing mechanical properties of normal and compression wood in Norway spruce: the role of lignin in compression parallel to the grain. Holzforschung,2002,56:395-401.
[12] Gindl W, Schoberl T. The significance of the elastic modulus of wood cell walls obtained fromnanoidentation measurements. Composites Part A: Appl. Sci. Manufac, 2004,35:1345-1349.
[13] Wimmer R, Lucas B N and Tsui T Y. Longitudinal hardness and Young’s modulus of spruce tracheid secondary walls using nanoindentation technique. Wood Science and Technology, 1997, 31(2):131-141.
[14] Choi, D., J.L. Thorpe, W.A. Quantification of compression failure propagation in wood using digital image pattern recognition. Forest Prod.J, 1996, 46(10):87-93.
[15] Mott,L., S.M. Schaler and L.H. Groom. A technique to measure strain distributions in single wood pulp fibers. Wood and Fiber Science 1996,28(4):429-437.
[16] Mark R E. Cell wall mechanics of tracheids Yale University. Press 1967.
[17]中国科学技术协会. 2006-2007力学学科发展报告.北京:中国科学技术出版社,2007
[18] Johansson L, Peng F, Simonson R. Effects of temperature and sulfonation on shear deformation of spruce wood. Wood science and technology, 1997,31:105-117.
[19] Eillis S, Steiner P. The behavior of five wood species in compression. IAWA Journal, 2002,23(2):201-211.
[20] Kohler L, Spatz H C. Micromechanics of plant tissues beyond the linear-elastic range. Planta, 2002,215:33-40.
[21] Singh A P, Anderson C R, Warnes J M. The effect of planning on the microscopic structure of pinus radiata wood cells in relation to penetration of PVA glue. Holz als Roh- und Werkstoff, 2002,60:333-341.
[22] Muller U, Gindl W, Teischinger A. Effects of cell anatomy on the plastic and elastic behavior of different wood species loaded perpendicular to grain. IAWA Journal, 2003,24(2):117-128
[23] Kifetew G, Thuvander F, Berglund L. The effects of drying on wood fracture surfaces form specimens loaded in wet condition. Wood science and technology.1998,32:83-94.
[24] Gong, M., Li, L., Chui, Y.H., Li, K.C, and Yuan, N.X. 2008. Modelling of recovery of residual stresses in densified softwoods. Proceedings of the 10th World Conference on Timber Engineering. Miyazaki, Japan. On Proceedings CD.
[25]刘君良,李坚,刘一星.高温水蒸汽处理固定大青杨木材横纹压缩变形的研究.林业科学,2003.39(1):126-131.
[26]赵钟声,刘一星,井上雅文,东原贵志.水蒸气前处理对杨木等5个树种木材压缩变形恢复率及力学性能影响的研究.林业机械和木工设备, 2003,5: 23-27.
[27]魏新莉,向仕龙,何华.水热预处理对杨木压缩木物理力学性能的影响.木材工业,2004,18(3):20-22.
[28]黄广华,陈瑞英.人工林巨尾桉木材压缩密化的研究.福建林学院学报,2007, 27(4):48-52.
[29]吴振锋,左洪福,邱根良,等.显微镜一种新的自动聚焦算法[J].数据采集与处理. 2000, 15(3): 351-354.
[30]方以,郑崇勋,闫相国.显微镜自动聚焦算法的研究.仪器仪表学报. 2005, 26(12): 1275-1277.
[31] Herajarvi H. Static bending properties of Finnish Birch wood. Wood Sci. Technol, 2004,37:523~530.
[32] Hernandez R E, Koubaa A, Beaudoin M et al. 1998. Selected mechanical properties of fast growing poplar hybrid clones. Wood and Fiber Sci,30(2):138~147.
[33] Schniewind A P. Mechanical behavior and properties of wood. In: Wangaard F F eds. Wood: its structure and properties. Educational modules for materials science and engineering (EMMSE) project, Materials Research Laboratiory, Pennsylvania State University, PA, 1:1979, 233~270.
[34]江泽慧,姜笑梅著. 2008.木材结构与其品质特性的相关性.北京:科学出版社.
[35] Chowdhury MQ, Ishiguri F, Iizuka K Radial variations of wood properties in Casuarina equisetifolia growing in Bangladesh. J Wood Sci ,2009,55:139-143.
[36] Bao FC, Jiang ZH.Wood properties of main tree species from plantation in China. China Forestry Publishing House, Beijing. 1998,4pp. In Chinese.
[37] Andrey S, Berglund LA. Shear coupling effects on stress and strain distributions in wood subjected to transverse compression. Composites Science and Technology, 2007,67 :1362–1369.
[38]戴秋莲.奥贝球铁的冲击断口分析.材料科学与工程,1999,03(1):59-62.
[39]贾江滢,徐家福,富东慧,王忠保,侯振德.加载速率对6020铝合金材料力学性能影响的实验研究[J].实验力学, 2008,23(1):77-83.
[40]方钦志,李慧敏,欧阳小东.加载速率对PC/ ABS拉伸性能的影响.高分子材料科学与工程, 2006,22 (1):131-134.
[41]罗国清,乔生儒,加载速率对3D2C/ SiC不同温度拉伸性能的影响.材料工程, 2003,10:9-10,39.
[42]李华,胡国程,肖俊玲.不同加载速度对热轧带肋钢筋σs、σb测试值的影响.金属材料与冶金工程,2010,01(1):12-14.
[43]张莉,张玉凤,霍立兴.加载速率对结构钢力学性能和断裂韧度的影响.焊接学报, 2003,24 (1):94-96.
[44]龚蒙,徐永吉,唐海波.木材顺拉弹性模量测定方法的研究—加载速度的选择.南京林业大学学报, 1995,19(4):93-96.
[45]朱南峰.加载速度对静曲强度数值的影响.林业科技开发, 1996, 13(3): 25-26
[46]张心安,朱一辛.竹材增强单板层积材的动态与静态弯曲性能.南京林业大学学报(自然科学版), 2006, 30(1):69-71.
[47]江泽慧,任海青,胡一贯,刘刚,阚娅.木材断裂过程的研究.核技术, 2000, 23(8):572-576.
[48]任海青,江泽慧.人工林杉木、马尾松木材的断裂特性.林业科学, 2001, 37(3):118-122.
[49]殷亚方,边明明,刘波,姜笑梅.连续压缩载荷下木材微观结构变化自动检测.建筑材料学报,2011,14(3):442-446.
[50] Johansson L, Peng F, Simonson R. Effects of temperature and sulfonation on shear deformation of spruce wood. Wood science and technology, 1997,31:105-117.
[51] Morookat T,Norimoto M. Influence of thermal softening and degradation on the radial compression behavior of wet spruce. International Journal of wood and wood products, 1998,12(1):45-52.
[52] Boonstra M.J. J.Blomberg. Semi-isostatic densification of heat-treated radiata pine Wood Sci Technol,2007,41:607–617.
[53] B.F.T jeerdsma H.Militz. Chemical changes in hydrothermal treated wood:FTIR analysis of combined hydrothermal and dry heat-treated wood,Holz als Roh-und Werksto,2005,63:102–111.
[54] Seppo Andersson.Ritva Serimaa·Timo PaakkariPekka Saranp Erkki Pesonen.Crystallinity of wood and the size of cellulose crystallites in Norway spruce(Picea abies) J Wood Sci, 2003,49:531–537.
[55] Kentaro Abe·Hiroyuki Yamamoto.Change in mechanical interaction between cellulose microfibril and matrix substance in wood cell wall induced by hygrothermal treatment. J Wood Sci,2006,52:107–110.
[56] Tang Xiaoshu, Zhao Guangjie, Nakao Tetsuya. Changes of Chemical Composition and Crystalline of Compressed Chinese Fir Wood in Heating Fixation. Forestry Studies in China,2008,6(4):39–44.
[57] Grossman, P.U.A. Requirements for a model that exhibits mechano-sorptive behavior. Wood Sci.Technol.1976,10:163-168
[58] Armstrong, L., Kingston, R.S.T. Effect of moisture changes on creep in wood. Nature,1960,18:862-863.
[59] Chaplin, M.. Non linear fracture mechanics in wood . In:proceedings of the international conference on integrated approach to wood structure. Behaviour and application joint meeting of ESWM and COST Action E35, Florence,Italy, Eds. Fioravanti,M., Macchionni. 2006. N.pp.218-227.
[60] Hoffmeyer, P..Failure of wood as influenced by moisture and duration of load. PhD thesis, State University of New York, College of Environmental Science and Forestry Syracuse, New York.1990.
[61] Hankijawi, A., Hunt, D.. Experimental indication of interaction between viscoelastic and mecahano-sorptive creep. Wood Sci. Technol.1998,32:57-80.
[62] Hunt,D., Gril,J.. Evidence of a physical ageing phenomenon in wood. J. Mater. Sci. 1986, 15:80-82.
[63] Navi P., Pitter V.,Plummer CJG. Transient moisture effects on wood creep. Wood Sci. Technol. ,1995, 36:447-462.
[64] Fioravanti M, Sodini N, Navi P. Investigation of the influecne of hemicelluloses on time dependent behavior of wood. In:proceedings of the international conference on integrated approach to wood structure. Behaviour and application joint meeting of ESWM and COST Action E35, Florence,Italy, Eds. Fioravanti,M., Macchionni. 2006. N.pp.190-194.