Showing papers in "Wood Science and Technology in 1967"
TL;DR: In this article, the present status of the chemistry of wood hemicelluloses is summarized, with special emphasis on recent contributions, and problems still to be solved in wood chemistry are discussed, and an attempt is made to predict future developments in this field.
Abstract: Following a brief review of the general chemical composition of wood, the present status of the chemistry of the wood hemicelluloses is summarized, with special emphasis on recent contributions. The distribution of the hemicelluloses in the various wood tissues and wood cells and over the cell wall of tracheids and fibers is discussed in somewhat more detail. In conclusion, problems still to be solved in the chemistry of wood hemicelluloses are mentioned, and an attempt is made to predict future developments in this field.
813 citations
TL;DR: In this article, the fiber saturation point of nine species of tropical trees was analyzed using a series of neutral solvents, and it was shown that the extraction of extractives reduced fiber saturation points by about one-half in desorption and by 7/8 in adsorption.
Abstract: The woods of different species vary widely in the nature and amount of their extractive content with a resultant variation in their sorption characteristics. This is particularly evident in the case of tropical woods, many of which are characterized by high extractive content. The nine species included in this study ranged from 3... 17 percent in extractive content. As determined from their desorption isotherms these species ranged from 20.5... 32.8 percent in fiber saturation point prior to extraction, and from 30.4... 38.0 percent after the removal of extractives with a series of neutral solvents. An analysis of variance showed that the variation in fiber saturation point among these species was reduced by about one-half following extraction in desorption and by approximately 7/8 in adsorption.
88 citations
TL;DR: The structure of bordered pits in springwood and summerwood tracheids ofAbies alba, Picea abies, Pinus silvestris andThuja occidentalis has been investigated in relation to their behaviour during pit closure microscopically as well as by penetrability studies.
Abstract: The structure of bordered pits in springwood and summerwood tracheids ofAbies alba, Picea abies, Pinus silvestris andThuja occidentalis has been investigated in relation to their behaviour during pit closure microscopically as well as by penetrability studies.
87 citations
TL;DR: In this paper, the authors divided the review into two parts, Part I covers flow of fluids and part II diffusion, and concluded that the conclusions drawn here involve Part I only.
Abstract: The flow of fluids and diffusion through wood follow different laws and vary in effectiveness through different structures. For this reason this review has been divided into two parts, Part I covers flow of fluids and part II diffusion. The conclusions drawn here involve Part I only.
53 citations
TL;DR: In this article, small beams of Douglas-fir were subjected to constant loads and the time to failure was investigated while the specimens were subject to cyclicly varying conditions of relative humidity and temperature.
Abstract: Small beams of Douglas-fir were subjected to constant loads and the time to failure was investigated while the specimens were subjected to cyclicly varying conditions of relative humidity and temperature. At a given load level, periodic variations in environment led to significant reductions in the average time to failure. The extent ofthis reduction was primarily related to the range in integral moisture content attained by the specimens.
46 citations
TL;DR: From the microscopic evidence, the modifications observed certainly indicate that the structures viewed are temperature-sensitive, although the critical temperature is still to be determined as discussed by the authors, and this sensitivity may be linked only to a change from a solid to a liquid state.
Abstract: From the microscopic evidence, the modifications observed certainly indicate that the structures viewed are temperature-sensitive, although the critical temperature is still to the determined. This sensitivity may be linked only to a change from a solid to a liquid state, and visual indications support such a tenet. This does not perclude, however, the possibility of thermo-chemical changes occurring at the elevated temperatures used.
26 citations
Journal Article•
23 citations
TL;DR: In this article, a set of creep equations for the multi-axial state of stress for an orthotropic medium, based on an invariant proposed by Hill for theory of plasticity, is presented.
Abstract: Creep equations have been formulated for the multi-axial state of stress for an orthotropic medium, based on an invariant proposed by Hill for theory of plasticity. Anyone of the numerous creep laws suggested from time to time by different investigators on the basis of experiments can then be used in these equations giving a complete set of equations for the solution of creep problems in orthotropic medium. Two simple applications are also discussed. An example in which principal axes of stress do not coincide with axes of anisotropy tension of a bar is discussed. Another example, that of compression under conditions of plane strain, illustrates variation of stress with time although load is kept constant. It is shown that in this case {ie142-1} relaxes to the final value {ie142-2} after a few times the retardation time.
22 citations
TL;DR: One of the most important tasks of wood engineering concerning the determination of permissible stresses in the design of wooden structural parts is to take into consideration the influence of the duration of loading on the strength properties of structural timber as discussed by the authors.
Abstract: One of the most important tasks of wood engineering concerning the determination of permissible stresses in the design of wooden structural parts is to take into consideration the influence of the duration of loading on the strength properties of structural timber.
14 citations
TL;DR: In this paper, the swelling rate of Engelmann spruce (Picea engelmannii Parry) in water was determined on cross sectional, quartersawn, and flatsawn samples.
Abstract: The swelling rate of Engelmann spruce (Picea engelmannii Parry) in water was determined on cross sectional, quartersawn, and flatsawn samples. The rate of swelling from six initial moisture content levels to saturation was measured in both the tangential and radial directions.
14 citations
TL;DR: In this paper, the shearing forces arising at the edge of the boundary between earlywood and latewood in the longitudinal and in the tangential directions of wood were determined according to the theory of statically indeterminate systems.
Abstract: The wood, composed of alternate earlywood and latewood lamellae, forms a statically indeterminate system with two redundants. The redundant forces are the shearing forces arising at the edge of the boundary between earlywood and latewood in the longitudinal and in the tangential directions of wood. By determining the redundant forces according to the theory of statically indeterminate systems, we know the state of stress and the state of detormation of the wood element and thus can determine its shrinkage and stresses in the longitudinal, tangential and radial directions.
TL;DR: The possibility of using microtomed longitudinal sections of wood for the study of longitudinal shrinkage has been investigated using hoop pine (Araucaria cunninghamii Ait).
Abstract: The possibility of using microtomed longitudinal sections of wood for the study of longitudinal shrinkage has been investigated using hoop pine (Araucaria cunninghamii Ait.). Cutting of the sections was shown to distort them and to affect their subsequent shrinkage. However, by increasing the inclination angle of the microtome knife, sections could be cut without change in longitudinal dimensions. The longitudinal shrinkage behaviour of such sections more than 80 μm thick was little different from that of thicker sawn specimens.
TL;DR: In this article, the effect of specific gravity and fiber-saturation point (FSP) on the volumetric shrinkage of wood has been analyzed with reference to specific gravity.
Abstract: Shrinkage observed on small clear specimens in radial and tangential directions and volumetric shrinkage obtained under the evaluation of physical and mechanical properties of wood have been analysed with reference to specific gravity and fibre-saturation point (FSP) It is observed that tangential shrinkage is 14 to 3 times that of radial shrinkage The difference between FSP in radial and tangential direction is not so predominant; it is possibly governed by variation in specific gravity of the wood substance The volumetric shrinkage is noted to be approximately equal to the sum of radial and tangential shrinkages Shrinkage is found to depend on both the specific gravity of wood and FSP Unlike Stamm's theory, their effect is found to be additive The effect of specific gravity is found to be more than the effect of FSP
TL;DR: In this article, it is pointed out that for the best and most reliable statement on the object the cutting of serial sections is indispensable, which can be reduced by suitable embedding and by choosing the most suitable knife to a minimum.
Abstract: Forced by the progressive perfectionation of the ultramicrotomes and by the improvement of preparation methods, the ultrathin sectioning technique has gained high importance for the electron-microscopical studies of the fine structure of wood cell walls. Wood has its own problems for ultramicrotomy. During cutting, the inhomogeneity of the cell wall and its chemical nature result in the formation of wrinkles and holes in the ultrathin sections. These artefacts are not completely avoidable but can be reduced by suitable embedding and by choosing the most suitable knife to a minimum. It is pointed out that for the best and most reliable statement on the object the cutting of serial sections is indispensable.
TL;DR: In this paper, it was shown that the magnitude of shear deflection depends on both the span to depth ratio of the beam and the elastic properties of the species involved, and failure to take it into consideration may introduce errors of considerable magnitude in determining the distortion of a beam.
Abstract: In addition to the deflection due to pure bending in a beam, there is a shear force in all cases of non-uniform bending and a further deflection, due to shear stresses. This additional shear deflection usually is assumed to be negligible and is not considered in computing the total deflection of a beam. In the case of two-species laminated wood beams, due to the development of greater shear stresses, the percentage of shear deflection further increases and failure to take it into consideration may introduce errors of considerable magnitude in determining the distortion of the beam. It is shown here that the percentage of shear deflection can be considerable, approaching the amount due to pure bending. Furthermore it is shown that the magnitude of shear deflection depends on both the span to depth ratio of the beam and the elastic properties of the species involved. It increases as the effective span to depth ratio of the composite beam decreases and as the core ratio of pure modulus of elasticity to modulus of rigidity increases.
TL;DR: In this paper, the temperature distribution on the surface and inside of dry samples of beech and spruce was determined at one-sided short and long wave infrared radiation in dependency on time and intensity of radiation and on the thickness of the wood.
Abstract: By means of a newly developed measuring device the temperature distribution on the surface and inside of dry samples of beech and spruce was determined at one-sided short and long wave infrared radiation in dependency on time and intensity of radiation and on the thickness of the wood. Furthermore, the surface temperatures of moist samples were measured as a function of moisture content. The results which are important for the practice of infrared radiation were plotted in diagrams from which e. g. the increase of the temperature at the radiated surface in dependence on thickness and species of the wood and on the duration and intensity of short and long wave infrared radiation can be read. The drying tests, made on wood samples of different thickness by means of one- and two-sided short and long wave infrared radiation, gave valuable information on the practical application of infrared wood drying.
TL;DR: In this article, the authors extended the models put forward by Preston and Kelsey to represent the longitudinal shrinkage of wood to take into account shearing stresses between microfibrils and between fibres.
Abstract: Models put forward by Preston and Kelsey to represent the longitudinal shrinkage of wood have been extended to take into account shearing stresses between microfibrils and between fibres. Mathematical relationships have been developed and previous models shown to be approximations to that developed here.
TL;DR: In this article, some variables affecting the bleedthrough of phenolic resin adhesives in hardwood plywood were studied quantitatively, including resin age, age of adhesive mix, extender/water ratio, amount of glue spread, aseembly time, veneer moisture content, species differences, grain angle, platen pressure, pressure cycle and platen temperature and rate of temperature rise.
Abstract: Some variables affecting the bleedthrough of phenolic resin adhesives in hardwood plywood were studied quantitatively. Variables included resin age, age of adhesive mix, extender/water ratio, amount of glue spread, aseembly time, veneer moisture content, species differences, grain angle, platen pressure, pressure cycle, platen temperature and rate of temperature rise.