Quantification of slip planes in the stem wood of Eucalyptus grandis

Holzforschung ◽  
2019 ◽  
Vol 73 (3) ◽  
pp. 269-275
Author(s):  
Jordão Cabral Moulin ◽  
José Tarcísio Lima
Keyword(s):  
Tensile Stress ◽  
Slip Plane ◽  
Microfibril Angle ◽  
Eucalyptus Grandis ◽  
Natural Occurrence ◽  
Plane Angle ◽  
Wood Fibers ◽  
Stem Wood ◽  
Stress Region ◽  
Slip Planes

AbstractThe objective of this work was to analyze the natural occurrence of slip planes (SPs) inEucalyptus grandiswood fibers in terms of their characterization, distribution in the stem and associations with other wood characteristics. A 28-year-oldE. grandiswas studied, whose stems were sampled in the base-top direction. The longitudinal compressive stress regions (LCompSR, in the inner part of the stem) and longitudinal tensile stress region (LTensSR, in the outer parts of the stem) were separately considered. The following parameters were measured: microfibril angle (MFA), slip plane angle (SPA), number of SPs per millimeter (SP mm−1), slip plane index (SPI) and the relative abundance of SP in the fiber. The SPAs differ only slightly between LCompSR (76°) and LTensSR (77°). The base of the stem, which supports a larger mass, contains the most SPs and the number of SPs decreases from the base to the top. In the LCompSR, the SPI reduction was from 21 to 8%, and in the LTensSR, from 18 to 7%.

A Study of Eucalyptus Grandis and Eucalyptus Globulus Branch wood Microstructure

IAWA Journal ◽  
2005 ◽  
Vol 26 (2) ◽  
pp. 203-210 ◽  
Author(s):  
Russell Washusen ◽  
Robert Evans ◽  
Simon Southerton
Keyword(s):  
Tension Wood ◽  
Microfibril Angle ◽  
Eucalyptus Grandis ◽  
Local Variation ◽  
Experimental Measurements ◽  
X Ray ◽  
Stem Wood ◽  
Opposite Wood ◽  
Cellulose Crystallite ◽  
Branch Wood

Experimental measurements of cellulose crystallite width and microfibril angle (MFA) by X-ray diffractometry on SilviScan-2 and by conventional microtechniques revealed that the branch wood of the two species exhibited very similar trends in cellulose crystallite width and MFA. Cellulose crystallite width was greater on the upper side of the branches. Tension wood, as defined by the occurrence of gelatinous fibres, was found where cellulose crystallite width was greater than 3.0 nm and 3.1 nm in Eucalyptus grandis and E. globulus respectively. In the tension wood zones, MFA was lower than in the rest of the samples and so could be used to differentiate tension wood. On the lower side of the branches MFA determined from X-ray diffractometry unexpectedly exceeded 40° and fibres were often buckled in both the tangential and radial directions in both species. This local variation in the direction of the fibre axes contributed only slightly to the magnitude of the MFA determined by SilviScan-2. Even given this misalignment, the additional evidence gained from pit angles and cracks in fibre walls suggested that the MFA was indeed around 40° in the lower radius of the branches. This MFA is considerably larger than would be expected for eucalypt stem wood and it is suggested that opposite wood in eucalypt branches may provide a complimentary structural role to that of the tension wood. Experimental measurements of crystallite width produced by SilviScan-2 may be used to accurately locate tension wood zones in both species.

Microfibril angle, crystalline characteristics, and chemical compounds of reaction wood in stem wood of Pinus densiflora

2019 ◽  
Vol 54 (1) ◽  
pp. 123-137
Author(s):  
Byantara Darsan Purusatama ◽  
Jung Kee Choi ◽  
Seung Hwan Lee ◽  
Nam Hun Kim
Keyword(s):  
Pinus Densiflora ◽  
Microfibril Angle ◽  
Chemical Compounds ◽  
Reaction Wood ◽  
Stem Wood

Basal Plane Dislocation Multiplication via the Hopping Frank-Read Source Mechanism and Observations of Prismatic Glide in 4H-SiC

2012 ◽  
Vol 717-720 ◽  
pp. 327-330 ◽  
Author(s):  
Huan Huan Wang ◽  
Sha Yan Byrapa ◽  
F. Wu ◽  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
...  
Keyword(s):  
Shear Stress ◽  
Slip Plane ◽  
Opposite Direction ◽  
Edge Dislocation ◽  
Basal Plane ◽  
Detailed Mechanism ◽  
Slip Planes ◽  
Basal Plane Dislocation ◽  
Edge Dislocations ◽  
Dislocation Multiplication

In this paper, we report on the synchrotron white beam topographic (SWBXT) observation of “hopping” Frank-Read sources in 4H-SiC. A detailed mechanism for this process is presented which involves threading edge dislocations experiencing a double deflection process involving overgrowth by a macrostep (MP) followed by impingement of that macrostep against a step moving in the opposite direction. These processes enable the single-ended Frank-Read sources created by the pinning of the deflected basal plane dislocation segments at the less mobile threading edge dislocation segments to “hop” from one slip plane to other parallel slip planes. We also report on the nucleation of 1/3< >{ } prismatic dislocation half-loops at the hollow cores of micropipes and their glide under thermal shear stress.

Vulcanization of Guayule Rubber

1981 ◽  
Vol 54 (1) ◽  
pp. 24-33 ◽  
Author(s):  
L. F. Ramos-De Valle
Keyword(s):  
Tensile Stress ◽  
Kinetic Analysis ◽  
Tensile Properties ◽  
Natural Occurrence ◽  
Different Types

Abstract The vulcanization characteristics of natural guayule rubber (GR) were compared to those of natural hevea rubber (HR). In the case of purified rubbers, vulcanization and tensile properties were shown to be very similar, whereas in the unpurified raw rubbers, HR was faster in vulcanization and attained a higher modulus than GR. These differences between raw rubbers were most pronounced in conventional vulcanization systems using MBT as the sole accelerator. As a result of a variety of different types of measurements on raw and purified rubbers, (relaxed tensile stress [MOD], Monsanto Rheometer curves, degree of crosslinking measurements, and kinetic analysis) it was concluded that the differences between HR and GR were due to the natural occurrence in HR (and absence in GR) of a vulcanization activator of a type similar to a basic secondary accelerator. Finally, in any formulation, the addition of very small quantities of activator or basic secondary accelerator is recommended in GR in order to attain similar properties to those of HR.

Effects of leaf and branch removal on carbon assimilation and stem wood density of Eucalyptus grandis seedlings

Trees ◽  
2006 ◽  
Vol 20 (6) ◽  
pp. 725-733 ◽  
Author(s):  
D. S. Thomas ◽  
K. D. Montagu ◽  
J. P. Conroy
Keyword(s):  
Wood Density ◽  
Eucalyptus Grandis ◽  
Carbon Assimilation ◽  
Stem Wood

scholarly journals Comparative studies on wood structure and microtensile properties between compression and opposite wood fibers of Chinese fir plantation

2021 ◽  
Vol 67 (1) ◽  
Author(s):  
Zhu Li ◽  
Tianyi Zhan ◽  
Michaela Eder ◽  
Jiali Jiang ◽  
Jianxiong Lyu ◽  
...  
Keyword(s):  
Cellulose Microfibril ◽  
Microfibril Angle ◽  
Tensile Modulus ◽  
Scientific Basis ◽  
Ultimate Tensile Stress ◽  
Chinese Fir ◽  
Cellulose Content ◽  
Wood Fibers ◽  
Opposite Wood ◽  
Chinese Fir Plantation

AbstractThe microtensile properties of mechanically isolated compression wood (CW) and opposite wood (OW) tracheids of Chinese fir (Cunninghamia lanceolata) were investigated and discussed with respect to their structure. Major differences in the tensile modulus and ultimate tensile stress were found between CW and OW fibers. Compared to OW, CW showed a larger cellulose microfibril angle, less cellulose content and probably more pits, resulting in lower tensile properties. These findings contribute to a further understanding of the structural–mechanical relationships of Chinese fir wood at the cell and cell wall level, and provide a scientific basis for better utilization of plantation softwood.

Reinforcement design for the anchorage of externally prestressed bridges with "tensile stress region"

2013 ◽  
Vol 11 (5) ◽  
pp. 383-397
Author(s):  
C. Liu ◽  
D. Xu ◽  
B. Jung ◽  
G. Morgenthal
Keyword(s):  
Tensile Stress ◽  
Stress Region ◽  
Reinforcement Design

Anatomical and chemical factors affecting tensile growth stress in Eucalyptus grandis plantations at different latitudes in Brazil

2012 ◽  
Vol 42 (1) ◽  
pp. 134-140 ◽  
Author(s):  
Miho Kojima ◽  
Hiroyuki Yamamoto ◽  
Koichiro Saegusa ◽  
Fabio Minoru Yamaji ◽  
Masato Yoshida ◽  
...  
Keyword(s):  
Lignin Content ◽  
Microfibril Angle ◽  
Eucalyptus Grandis ◽  
Middle Layer ◽  
Growth Stress ◽  
Cellulose Content ◽  
Factors Affecting ◽  
Wide Range ◽  
Chemical Factors ◽  
Processing Defects

The key to using planted Eucalyptus as timber lies in controlling the characteristic high tensile growth stress that often causes serious processing defects in sawn logs and lumber. In the present study, we investigated variations in the longitudinal released strain (RS) of surface growth stress in stems of Eucalyptus grandis W. Hill ex Maiden planted in a wide range of latitudes in Brazil and established relationships between RS measurements and anatomical and chemical factors. Cellulose and lignin content, RS, and the microfibril angle (MFA) of the middle layer of the secondary wall (S2 layer) differed among latitudes. The increase in cellulose content and decrease in MFA were correlated with the contractive value of RS, which explained the higher tensile growth stress in stems from high-latitude plantations where higher cellulose content and lower MFA were observed. To reduce processing defects due to tensile growth stress, the factors controlling MFA values and cellulose content must be identified.

scholarly journals Characterization of eucalyptus clones subject to wind damage

2017 ◽  
Vol 52 (11) ◽  
pp. 969-976
Author(s):  
Antônio José Vinha Zanuncio ◽  
Amélia Guimarães Carvalho ◽  
Angélica de Cassia Oliveira Carneiro ◽  
Paulina Valenzuela ◽  
William Gacitúa ◽  
...  
Keyword(s):  
Pearson Correlation ◽  
Microfibril Angle ◽  
Eucalyptus Grandis ◽  
Basic Density ◽  
Middle Lamella ◽  
Growth Stress ◽  
Wind Damage ◽  
Modulus Of Rupture ◽  
Tree Resistance

Abstract: The objective of this work was to test a new methodology to assess the resistance of trees to wind damage and determine the characteristics that increase clone resistance to winds. Tree resistance to breakage, basic density, ultrastructure, anatomy, mechanical properties, and wood growth stress have been evaluated in seven Eucalyptus grandis × Eucalyptus urophylla clones, collected from a region with a high incidence of wind damage. The Pearson correlation coefficient between the tree resistance to breakage and the ratio between the area damaged by the winds and the total planted area was -0.839, showing the efficiency of the methodology adopted and that high breaking strength results in a smaller area affected by wind damage. Trees with a high basic density, cell wall fraction, modulus of elasticity of the middle lamella and fibers, fiber hardness, modulus of rupture, growth stress and low microfibril angle and height and width of the rays showed greater resistance to wind damage. Therefore, the selection of clones with these features may reduce the incidence of damage by winds in Eucalyptus plantations.

Application of X-ray diffraction to assess the microfibril angle of green and dry Eucalyptus grandis wood

Trees ◽  
2021 ◽  
Author(s):  
Naiara Conceição Marques de Souza ◽  
José Tarcísio Lima ◽  
Bruno Charles Dias Soares
Keyword(s):  
Microfibril Angle ◽  
Eucalyptus Grandis ◽  
X Ray Diffraction ◽  
X Ray
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