Content directory:
The composition of the first section of the tree
Section 2 Wood Construction
Identification of the third tree species
Section 4 Wood Properties
Composition of trees
Trees are made up of three parts: roots, trunks, and crowns.
1. The root of the tree, the root of the tree is the lower part of the tree, that is, the underground part, which accounts for 5%~25% of the wood volume. Its function is: (1) absorb water and minerals from the soil and transport it from bottom to top along the trunk to the branches and leaves. With photosynthesis by light and chlorophyll, organic nutrients are produced and transported down the trunk phloem to the root of the trunk. (2) Storage of spare nutrients that are lowered by the phloem of the trunk. (3) Stabilize the trunk and fix the trees on the land to maintain the stable growth of the trees. In addition, the roots are used for fuelwood. With the development of the economy and scientific progress, the roots have become a good material for art. Root carving, and some roots such as pine cutting, can extract turpentine and rosin.
2. The trunk and trunk are the most important part of the tree, that is, the wood part of the tree, which occupies 50%~90% of the wood volume. The effect is: (1) The trunk and the tree root are integrated to support the canopy. (2) transporting water and minerals from the roots of the tree, and transporting organic nutrients from the canopy down through the phloem. (3) Storage of nutrients for the growth and reproduction of trees. In addition, the xylem formed by trees is the most trunk, and the wood is mainly from the trunk, which has important use value.
3. Crowns, crowns are the general term for branches and leaves, located in the uppermost part of the tree, occupying 5% to 25% of the wood volume. The effect is: (1) the leaves are extracted from the soil by carbon dioxide taken from the air and through the roots. The water and minerals come from photosynthesis by means of chlorophyll under the radiation of sunlight, and nutrients are made by photosynthesis for the growth of trees. (2) The branches can transport and store water and nutrients up and down, and support the leaves. In addition, branches can be used as small-diameter wood, generally more fuelwood, but with the increase of the use of surplus materials, branches can also be used as raw materials for shavings, paper, fiberboard, particleboard; leaves can be used as feed, but also from Extract chemicals and so on.
Composition of the trunk
Viewed from the cross-section of the trunk, the trunk is composed of bark, forming layers, xylem, and marrow.
1. Bark, the bark is the outermost layer of the trunk, that is, all the tissues outside the formation are called bark. Bark is usually divided into skin, pericarp and endothelium. There is a thin skin between the outer skin and the endothelium, called the pericarp (not visible to the naked eye). The outer skin is called the outer skin, also known as the dead skin. It is usually darker in color and plays a role in protecting trees from external factors and weakening mechanical damage. The inner skin is called the endothelium, that is, the phloem is the living tissue in the trees. It has the function of transporting nutrients downward during the growth process. (1) Bark composition: rind, pericarp and endothelium.
(2) Bark action, to prevent the evaporation of water from trees, to transport nutrients produced by leaves and to store nutrients, is a protective layer of trees. In addition, the bark of different tree species has different effects. For example, birch bark can be used to make birch tar, which is used for medicine and tanning; bark of tree species such as magnolia, bitter wood, and Eucommia are valuable medicinal materials. At the same time, bark is one of the main basis for on-site identification of wood because the external shape, thickness, color, texture, peeling, smell and taste of the bark are different.
2. A layer is formed which is a layer of narrow and subdivided cells located between the phloem and the xylem. A mother cell having a dividing ability in the layer is formed, and the daughter cells are continuously divided. The mother cells divide the phloem outward to form a bark; the xylem is inwardly formed to form wood, and thus it is the source of wood. (1) Forming the composition of the layer, the layer forming cells are composed of primitive cells, and the original cells can be further divided into spindle-shaped primitive cells and radiation-shaped primitive cells. (2) The role of forming a layer, which has the function of dividing cells, that is, has a meristematic effect.
3. The xylem, the xylem is located in the middle of the formation and the medulla, is the most economical part of the trunk, and is the most important part of the wood. (1) The composition of the xylem, according to the source of the cell composition, the xylem can be divided into primary xylem and secondary xylem. The primary xylem originates from the apical meristem and has a very small component that surrounds the medulla; the secondary xylem is derived from the formation. The majority of the xylem is the secondary xylem. It can also be said that the secondary xylem of the trunk is the most valuable. (2) The role of the xylem, the absorption of water and minerals from the ground, the transport and storage of nutrients, is the source of the formation of wood.
4. The marrow, the pulp is located in the center of the trunk (often eccentric), surrounded by xylem, the marrow (which is a thin-walled tissue) and the first-born xylem of the first year to form the medulla. The shape, size, color, structure, etc. of the medulla are different depending on the species, and are one of the basis for identifying wood. (1) The shape of the medulla, the core of most tree species is round or elliptical in cross section, such as masson pine, eucalyptus, color wood and so on. But there are also special shapes, such as star-shaped eucalyptus, sweetgum, rhomboid large leaves, boxwood, and pentagonal poplar. (2) The color of the medulla, the heart of most tree species is brown or light brown, but also has a special color, such as the medulla of the paulownia is white. (3) The size of the medulla, the core of the coniferous species is generally small, about 3 to 5 mm, and the difference is not large; the broad-leaved tree has a large and small medulla, and the large core can reach several centimeters. (4) The structure of the medulla, the structure of the medulla is different depending on the species of the tree, such as eucalyptus, hollow, such as paulownia, filled with soft and thin-walled tissue such as paulownia. In addition, the core tissue is soft, low in strength, and easy to crack. Therefore, it has an effect on the material with higher quality requirements, but has little effect on the general material.
Section 2 Wood Construction
Three sections of wood
Trees are organisms. They are composed of countless cells of different shapes, sizes, and arrangements. These cells exist in a three-dimensional state in wood tissue. Therefore, in order to correctly understand the structure of wood, it is necessary to carry out three sections. Observed. The three sections are the transverse section, the diameter section, and the string section. Among them, the cross section is the most important aspect of the wood.
(1) The cross section, the section perpendicular to the main axis of the trunk is called the cross section. In addition to the annual rings, the characteristics of the wood texture are exposed on this cut surface. The cross-section is the most important cut surface for identifying wood. This cut surface is hard and wear-resistant and can be used as paving blocks.
(2) The radial section is parallel to the main axis of the trunk, and the section through the medulla is called the radial section. The cut sheet has small shrinkage and is not easy to warp, and is suitable for making wooden rulers and musical instrument soundboards.
(3) Chord section, parallel to the main axis of the trunk, the section that does not pass through the medulla and is tangent to the annual ring is called the chord section. It is the tangent of an annual ring and the string of another annual ring. Different structures of wood can be observed on different sections. For example, the width and length of the wood ray and the interrelationship between the wood cells can be observed on the cross section; the annual ring can be observed as strips, parallel to each other, and perpendicular to the wood ray; the year can be observed on the chord The wheel is in a "V" shape.
Wood structure characteristics
The term "wood structure" as used herein refers to a wood macrostructure or a macroscopic structure, which can be observed with the naked eye or a magnifying glass.
(1) Heartwood, sapwood
From the cross-section, around the medulla, the part with darker color and less water content is called heartwood; near the bark, the part with lighter color and more water content is called sapwood.
(2) Growth wheel, annual ring, early wood, and late wood
A layer of wooden ring wheels formed by trees during a growth cycle, called a growth wheel. For trees in temperate and cold regions, the growth wheel only appears once a year, so the growth wheel is also called the annual ring; for the trees in the tropics, the annual growth wheel can appear several times, so it is generally not called the annual ring, only the growth wheel.
The wood formed in the early growing season is called early wood. Its characteristics are: fast cell division, large volume, thin cell wall, soft material and light color; the wood formed in the late growth season is called late wood, its characteristics: cell division The speed is slow, the splitting ability is weakened, the cell wall is thick, the material is dense, hard, and the material color is deep.
(3) wood ray
Wood ray is the only radiation-like, horizontally aligned structure in wood that acts as a lateral transport and storage nutrient during the growth of trees. At the same time, wide wood ray wood is a good material for making furniture. In addition, the wood ray is composed of thin-walled cells, which are the weaker and less strong parts of the wood, especially when the wood is dried, it is easy to crack along the wood ray, which reduces its use value.
(4) Tube hole, intercellular channel
Tube holes are an important basis for identifying needles and broad-leaved species. Coniferous species have no tube holes, also known as non-porous materials; broad-leaved trees have tube holes, also known as perforated materials. The catheter has a hole-like shape on the transverse section, which is called a tube hole. The distribution, combination and arrangement of the tube hole are one of the main features for identifying broad-leaved tree species.
(1) The type of tube hole is divided into:
Ring hole material means that in an annual ring, the early material tube hole is obviously larger than the late material tube hole, and is arranged in a ring shape along the annual ring.
The loose hole material means that there is no obvious difference in the size of the early and late material tube holes in one annual ring, and the distribution is uniform or relatively uniform.
The semi-dispersion (ring) hole material means that in an annual ring, the arrangement of the tube holes is between the loose hole material and the ring hole material, that is, the early material tube holes are slightly larger and slightly arranged in a ring shape, from early on. The tube hole of the material to the late material gradually becomes smaller and the boundary is not obvious.
Radiation pore material means that there is no significant difference in the pore size of the early and late tube, and its arrangement is radial in the radial direction, passing through an annual ring to several annual rings.
The tangential hole material means that all the pipe holes are in a series of chord chains in one annual ring.
2) The type of tube hole is divided into:
Single hole means that one tube hole is completely surrounded by other molecules and is distributed separately in the annual ring.
The double hole means that two or more pipe holes are closely connected in the radial direction, except that the pipe holes at both ends are still circular, and the pipe holes at the intermediate connection are flat.
The tube hole group means that the tube holes are irregularly aggregated together.
The tube hole chain is an exponential tube hole arranged radially, and each tube hole remains in its original shape.
(3) The type of tube hole is divided into:
Star scatter means that most of the tube holes are separate and evenly or evenly distributed, such as ash, and wood.
The eucalyptus shape refers to a string of tubes that are continuously wavy or slanted in a chordwise arrangement, slightly parallel to the annual rings and tangential, such as eucalyptus.
The flaming shape means that the early material tube holes are larger, the tube holes are arranged like a flame, and the late material tube holes are small, and the shape is like a fire tongue, such as chestnut.
The "" shape refers to the regular arrangement of the tube holes in the oblique column, which is in the shape of "", such as berberine.
Non-structural features of wood
(1) Material color
(2) smell and taste
(3) Structure
(4) texture
(5) gloss
(6) Weight and hardness
Identification of the third tree species
Wood species identification is a suitable technique for identifying tree species through the internal and external characteristics of wood. It is the foundation and an indispensable part of wood inspection and plays a very important role in the production, circulation and use of wood.
Commercial tree species
1. species
Tree species are species that are classified according to the taxonomy of trees, ie, species of trees, such as Korean pine, larch, Pinus sylvestris, ash, poplar, and elm. It can also be said that tree species refer to the name of the tree as a biological species.
2. Commercial tree species
The name of the wood used for the production, processing, distribution, and use of wood as a commodity is called the name of the commodity. It is one of the main bases for the classification of timber prices, and it is also the general term for the circulation of timber as a commodity.
The name of the commodity material itself reflects the two aspects of wood classification and naming. The categorization of the wood of many tree species into a small number of classes, with the "class" and "species", can meet the rational use of wood, and can take care of the convenience of production.
The name of the commodity material can be borrowed from the name of “tree speciesâ€, but this “tree species†should be the commodity tree species. Therefore, the tree species in the wood standard are commodity wood species. Commodity wood species are classified according to the principle that wood appearance characteristics are similar, structure and materiality are similar.
3. Product tree species naming principle
(1) Classification based on the genus of tree classification.
(2) The principle of classification based on materials.
(3) The name of the tree species classified by trees is the name of the commodity.
(4) Use the custom name of the production unit as the name of the commodity.
(5) The principle of classification of a few tree species of different genus in the same family.
Tree species identification method
1. Identification by bark and material table.
2. Identification by wood construction and non-structural features.
3. Identification by wood identification search table, wood specimens, and scientific identification.
Tree identification tool
A sharp shovel and a ten-fold magnifying glass.
Tree species identification points
1. Conifer species
The coniferous material belongs to the gymnosperm subphylum. The outer skin of the bark is mostly scaly and the endothelium is thin. The wood is almost entirely composed of tracheids, without a catheter, and the difference between the heart and the sapwood is obvious or not obvious. The difference between early and late in the growth wheel is obvious, the early wood color is light, the late wood color is deep, the wood is light and soft, and some wood has resin channel and special smell. The texture is straight and the structure is fine. The material table is smooth.
(1) Korean pine (Pinaceae. Pinus)
(2) Xing'an larch (Pinaceae. Larch)
(3) Pinus sylvestris (Pinaceae. Pinus)
(4) Masson pine (Pinaceae. Pinus)
(5) Spruce (Pinaceae. Spruce)
(6) Fir (Pinaceae. Abies)
(7) Hemlock (Songko. Hemlock)
(8) Chinese fir (Firaceae. Chinese fir)
2. Broadleaf species
The broad-leaved genus Angiosperm, the subgenus dicotyledon, has a wide variety. The biggest feature of conifers is that they have tube holes. The wood rays are wide, thin and thin-walled. Some trees have gum lanes and odors. The wood structure is coniferous. complex.
(1) Alder (Alderaceae, Alder)
(2) Poplar (Willowaceae. Populus)
(3) Birch (Birchaceae. Birch)
(4) 柞木 (Fagida. æ Ž)
(5) Fraxinus mandshurica (Oleaceae, genus)
(6) Huang Boluo (Symphaea, Astragalus)
(7) Alder (Amaranthus, Eucalyptus)
(8) 樟木(樟科,樟属)
Tree identification step
Tree species identification should be practiced, carefully summarized, accumulated experience, and should not be understood. When identifying tree species, you need to have a sharp small blade and a 10x magnification mirror to observe the wood construction. The steps to identify are as follows:
Observe if there is a catheter, separate the needle, and broadleaf. Conservatives are broad-leaved trees; conicals are conifers.
If it is determined to be a broad-leaved tree, then observe the distribution of the tube hole on the cross-section and the shape of the arrangement, and then step-by-step decomposition observation until the tree species name.
If it is determined to be a conifer, then observe if there is a resin track. The resin road is a genus of pine, larch, spruce, yellow fir, silver fir, and oil fir; the resin-free road is a genus of fir, hemlock, fir, cypress. Then follow the step by step until the tree species.
In short, when observing the characteristics of wood, it is necessary to grasp the characteristics of the more stable, distinguish the primary and secondary, and list the characteristics with the greatest stability in the front, and check the wood identification list from the primary to the secondary until the tree species name.
Section 3 Wood Physical Properties
Wood chemistry
The chemical properties of wood refer to the properties that can be understood through chemical decomposition, including the chemical composition of wood and the characteristics of the main chemical components of wood. The chemical composition of wood is very complex and there are two general categories.
1. Organic matter (1) Cellulose, (2) Hemicellulose, (3) Lignin, (4) Intrusion; 2. Inorganic matter, inorganic matter exhibits ash in wood. When wood is burned, ash is produced. The chemical components of the ash are potassium carbonate, sodium carbonate, calcium carbonate, phosphorus, inorganic salts and the like.
Wood physical properties
The physical properties of wood refer to the properties that can be understood without changing the chemical composition of the wood or destroying its integrity.
Moisture content
(1) Free water.
(2) Attached water.
The chemical composition of free water and attached water is exactly the same, except that the parts present in the material cells are different, and the attached water is the main factor affecting the wood.
(3) Moisture content (water content), the calculation of water content in wood is measured by water content (or water content). The amount of moisture in the wood is called the water content (or water content). Water content is divided into absolute moisture content (W) relative water content (W0)
Absolute moisture content (W) = (water-based wood weight - absolute dry weight) / absolute dry weight × 100%
Relative moisture content (W0) = (water-based wood weight - absolute dry weight) / water-containing wood weight × 100%
The absolute moisture content is mostly applied in engineering; the relative water content is mostly applied in scientific experiments. Absolute moisture content is often referred to as moisture content and can be converted to relative moisture content.
W= 100 W0/ (100—W0 )
W0= 100W / (100+W)
(4) Wood is classified by moisture content
Wet material refers to wood that has been immersed in water for a long time, and its moisture content is higher than that of raw materials.
Raw wood refers to wood that has just been harvested, and its moisture content is 70% to 140%.
Air dry material refers to wood that is naturally dry in the air. Its moisture content depends on the air humidity, and the water content is between 12% and 18%, with an average of 15%.
Kiln dry material refers to the extent that the wood is dried in a dry kiln below the air dry material, and the water content is 4% to 12%.
Absolute dry materials, also known as full dry materials, refer to wood that is placed in an oven at 100 to 1050 C to a moisture content of zero.
(5) Wood fiber saturation point
definition
When the free water is completely evaporated and the attached water in the cell wall is saturated, the water content is between 25% and 35%, with an average of 30%.
significance
The significance of fiber saturation point is not only the size of its water content, but mainly because it is the turning point of wood strength, expansion and contraction, conductivity and other material changes.
2. Hygroscopicity
The property of dry wood to absorb water vapor from the air is called moisture absorption; the performance of wet wood to evaporate water vapor into the air is called desorption. These two phenomena together are called the hygroscopicity of wood.
The wood is placed in the air, and when the humidity of the wood is greater than the humidity of the air, the moisture in the wood evaporates into the air. Conversely, when the humidity of the wood is less than the humidity of the air, the wood absorbs moisture from the air. Under normal circumstances, the wood evaporates more water than it absorbs. As the wood dries and evaporates slowly, it finally reaches the state of not absorbing moisture from the air or losing moisture, that is, the wood humidity is equal to the air humidity. The moisture content of the wood at this time is called the equilibrium moisture content.
3. Water absorption
The ability of wood to absorb water when immersed in water is called water absorption.
The degree of water absorption depends mainly on the time the wood stays in the water, and at the same time it varies with tree species, porosity, capacity, and the like. For example, wood with a large volume is slower and less absorbent than wood with a small bulk density, and the heartwood has poor water absorption properties than the sapwood. Understand the water absorption of wood, and contribute to the preservation and transportation of wood.
4. Water permeability
The water permeability of wood, also known as water conductivity, refers to the ability of one side of the wood to contact water and the other side to contact the air, allowing the water to pass through the wood under hydrostatic pressure or other pressure.
The size of wood permeability depends on the species, the direction of the cut surface, whether it is heartwood or sapwood and moisture content.
5. Dry shrinkage and swelling
When the moisture content of the wood is below the fiber saturation point, the shrinkage and swelling of the wood can be talked about. From the point of fiber saturation, the wood continues to dry, the attached water evaporates, and the wood shrinks until it is dry. This process is called shrinkage. From the dry state, the wood absorbs moisture or absorbs water, and the wood expands until the fiber is saturated. This process is called swelling. Therefore, the expansion and contraction of wood refers to the performance of changing the size of the wood when the moisture content of the wood is below the fiber saturation point as the moisture increases or decreases.
6. Density
Wood Density = Test Piece Dry Material Quality / Test Piece Saturated Water Volume
The density of the wood depends on the size of the wood voids and the thickness of the cell walls. The wood has small voids, thick cell walls, dense tissue, and large wood density; wood has large voids, thin cell walls, loose tissue, and low wood density. The strength of the wood can also be used to estimate the strength of the wood. Some people also refer to the density of wood as the bulk density of wood.
7. Wood thermal conductivity
The thermal conductivity of wood is expressed in terms of thermal conductivity. Thermal conductivity, which is the amount of heat required to cause a 10C temperature difference between two sides of a wood through the unit area and unit length of wood per unit time.
8. Conductivity
The conductivity of the wood is very small, and the dry material is almost non-conductive.
9. Sounding
Wood has sound transmission properties. Because there are many gaps in the wood, it becomes the runway of the air, and the air can spread the sound.
Another important property of wood is resonance, because wood is made up of tubular cells. The resonance of wood differs depending on its density, elasticity, structural uniformity, and the like. The wood with uniform annual rings, dense materials and straight texture has good resonance, such as spruce is a good material for musical instruments.
Several terms of the mechanical properties of wood
Ultimate strength refers to the maximum external force that wood can withstand from stress to damage.
Hardness refers to the ability of wood to resist the intrusion of other solids.
Elasticity refers to the ability of a piece of wood to return to deformation after being stressed.
Rigidity refers to the ability of wood to resist deformation or maintain its original shape.
Plasticity refers to the ability of a wood to be unable to return to its original shape after being stressed.
Toughness refers to the ability of wood to undergo maximum deformation without damage.
Processability refers to the ability of wood to resist smashing, nailing, and grinding.
The wood quality coefficient refers to the ultimate strength of the wood against static and smooth pressure, that is, the ratio of the ultimate strength of the wood to the volumetric weight.
Factors affecting the mechanical properties of wood
There are many factors affecting the mechanical properties of wood. The main factors are wood defects, density, water content, and growth conditions. In general, the density is large and the strength is large. However, due to the different wood structure and inclusions of various tree species, the strength of wood with the same density may also differ.
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