X-rays were initially used for the inspection of special-purpose wood pieces for quantitative evaluation of wood properties of different species. X-ray densitometry has had its use expanded in dendroclimatology of Picea engelmannii trees. Subsequent laboratories developed applications of X-ray densitometry for environmental, wood science and technology, and related areas. This paper describes the basic methodology of X-ray densitometry applied to the eucalypt wood analysis, as well as presenting the results of applications in three areas: (i) evaluation of wood biodegradation by white rot fungi, (ii) detection of sapwood and heartwood, and (iii) determination of the effect of management on wood properties. The wood decayed by white rot fungi was detected by X-ray densitometry with a decreasing wood density due to the biodegradation of cell wall components. The sapwood and heartwood of eucalypts were separated in response to the attenuation of X-rays, refl ected by the wood anatomical structure and chemical composition. Also, in eucalypt trees after the application of irrigation and fertilizationirrigation characteristic wood density profi les were detected. In addition, the signifi cant potential of X-ray densitometry for eucalypt wood research and analysis is discussed.
RESUMO -Este trabalho estudou a variação das retratibilidades volumétrica e linear da madeira de Eucalyptus grandis proveniente de talhões comerciais de quatro diferentes idades (10, 14, 20 e 25 anos) e posição radial. As amostras foram retiradas da tábua diametral, de cada uma das 16 árvores (quatro para cada idade), tomadas de quatro posições eqüidistantes (0, 33, 66 e 100%), no sentido medula-casca. Verificou-se, em todos os testes, o efeito da idade e da variação radial, observando uma correlação positiva dos efeitos em todos os parâmetros estudados. A espécie, como um todo, apresentou elevada instabilidade dimensional, com valores médios de retratibilidade volumétrica de 18,11% e retratibilidade radial, tangencial e longitudinal de 6,09%, 10,14% e 0,45%, respectivamente, além do fator anisotrópico de 1,71. À exceção da retratibilidade longitudinal e do fator anisotrópico, todos os demais parâmetros apresentaram tendência de crescimento com a idade e com a direção radial, no sentido medula-casca.Palavras-chave: Eucalyptus grandis, retratibilidade, idade e variação radial. INFLUENCE OF AGE AND RADIAL POSITION ON THE VOLUMETRIC AND LINEAR SHRINKAGE OF Eucalyptus grandis Hill ex. Maiden WOOD ABSTRACT -The objective of this work was to study the linear and volumetric shrinkage variation of theEucalyptus grandis wood, along the radial plane at four different ages (10, 14, 20 and 25 years), from commercial stands. The samples were removed from the diametrical board of each of the sixteen trees (four from each age), taken from four equidistant positions (0, 33, 66 and 100%)
Este trabalho teve como objetivo a caracterização anatômica e físico-mecânica da madeira de Liquidambar sp. Para tanto, foram utilizadas três árvores com oito anos de idade, provenientes de um arboreto localizado do município de Guaçuí, Espírito Santo. As características anatômicas analisadas foram as dimensões das fibras (comprimento, diâmetro total e do lume e espessura da parede), dos elementos de vasos (diâmetro tangencial e frequência) e dos raios (altura, largura e frequência). Para a caracterização físico-mecânica foram avaliadas a massa específica (básica, aparente a 12% de umidade e anidra), as contrações totais lineares e volumétrica, a resistência à flexão estática, à compressão paralela às fibras, ao cisalhamento e dureza Janka. Constatou-se frequência vascular numerosa com vasos de pequeno diâmetro tangencial, raios heterocelulares ocorrendo em baixa frequência, e fibras libriformes longas de paredes delgadas a espessas. A massa específica básica da madeira proveniente de discos retirados a 1,30 m do nível do solo foi de 0,48 g cm-3, sendo considerada média, a estabilidade dimensional foi considerada baixa, e houve grande influência da umidade nos valores de resistência da madeira. AbstractAnatomical and physical-mechanical characterization of Liquidambar sp. wood. This research aimed to improve anatomical, physical and mechanical characterization of Liquidambar sp.wood. Three trees were obtained, at eight years of age, from an arboretum located in Guaçuí, Espírito Santo State, Brazil. The analyzed variables were dimensions of the fibers (length, total diameter and diameter of the lumen and wall thickness), the vessel elements (tangential diameter and frequency), and ray (height, width and frequency). The specific gravity (basic, at 12% moisture content and dry), and total volumetric and linear shrinkages, resistance to bending, compression parallel to the fibers, shear and Janka hardness. For anatomical description it was found numerous vessels often with small tangential diameter, heterocellular rays occurring at low frequency, and long libriform fibers with thick to thin walls. The specific gravity of wood from disks taken at 1.30 m from ground level was 0.48 g cm-3, wich we considered average, the dimensional stability was low, and there was great influence of moisture in the resistance values in wood.Keywords: Anatomy; specific gravity; dimensional stability; mechanical strength.
27The main goal of this study was to analyze glue line on eucalyptus wood. In order to do 28 that, thickness of main and secondary glue lines were measured as well their interaction 29 with apparent density of elements glued with resorcinol-formaldehyde (RF) and castor 30 polyurethane (CP) adhesives. Anatomical wood characterization of Eucalyptus grandis 31 × Eucalyptus urophylla was performed by correlating glue line thickness. According to 32 normative instruction, specimens were produced for delamination tests. The experiment 33 was conducted in a completely random 2 × 2 design factorial scheme (two classes of 34 apparent density and two adhesives). Pearson correlation (t < 0.01) was performed 35 among variables. It was found that there was adhesive penetration into wood pots and 36 rays. Glue line thickness was higher in woods with density higher than 0.58 g cm -3 glued 37 with RF adhesive. There was low correlation among density, vessel diameter, main and 38 secondary glue lines (t < 0.01). 39 40 Keywords: apparent density; resorcinol-formaldehyde; castor polyurethane; laminated 41 wood; delamination 42 43 Introduction 44Glued laminated timber (Glulam) is a structural product obtained by gluing 45 pieces of timber with fibers parallel to each other [1]. The market still needs to know 46 more information about the mechanical resistance of this product; for that reason, to 47 understand how glulam will work it is important to evaluate the behavior of some 48 variables, such as, apparent density and timber glued with adhesive. 49Wood density provides information to support methods that should be adopted 50 during the gluing process. By its determination, it is possible to correlate adhesion 3 51 resistance with anatomic elements. Proportion of empty spaces combined with 52 dimensions and arrangement of cellular elements have influence on adhesive's mobility 53 and penetration into timber structure as well in the resistance of glue line to 54 delamination [2, 3, 4, 5,6, 34]. When low density (higher frequency and vessel 55 diameters, with high and wide radii), it may allow excessive penetration of adhesive, if it 56 does not present an ideal viscosity and formation of ravenous glue line [7, 8]. 57When species are anatomically unfavorable for gluing, there will be low 58 adhesive penetration and formation of a thick glue line [8, 9]. Both types of glue lines 59 are undesirable, because they reduce mechanical strength of glued joints causing 60 separation of adjacent layers. Variations on adhesive viscosity can correct this problem 61 [3]. 62 Physico-chemical adhesion phenomenon predicts an interaction mechanism 63 between solid surfaces glued by adhesive and the capacity of holding other materials 64 together [10]. Adhesives are used to join elements by flowing and filling empty spaces 65 between them. Thus, they can reduce distances and create interactions among glued 66 elements [11]. 67 It is important to understand the interaction between wood and adhesive, because 68 it helps to evaluate glueing quality [7],...
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