Presentation on technology on the topic "Professions related to wood processing. Defects of wood" (grade 6). Work related to the processing and removal of trees (arboriculture) Professions related to wood processing presentation

Professions,
Related
processing
wood
Vices
wood
2017

Lesson objectives:
Get to know the professions
Describe each
professions
Define the concept
"Defect of wood";
Learn to recognize the main
external wood defects
mind;
Form a technological
culture.

Profession (lat. professio; from profiteor
“I declare my business”) - gender
human labor activity,
preparation.
owning the complex
theoretical knowledge and skills,
purchased during a special

Related professions
with processing
wood
Carpenter
Furniture maker
A carpenter
Builder
Master of wood carving or painting
Sawing machine
Cooper
Basket maker, wicker weaver
Music maker
instruments (Stradivarius)

Working with wood
people like that
professions:
Restorer Cabinetmaker
Lumberjack
Gardener Forester
Agronomist Tokar (by
tree)
Furniture designer Sculptor
Engineer, woodworking master
Landscape architect

Professions related to
wood processing

Forestry operator
combine (harvester)
Logging
combine, there is also
Anglicism "harvester"
harvester, from harvest “to collect”
harvest") - machine,
performing four or more
operations (felling, trimming
branches, skidding,
bucking, sorting). If
less than four is called
felling machine.
Cabin mounted
the computer operator allows
control the head operation
combine and set lengths
chopped assortments.
The program has
automatic mode for
achieving maximum
yield of industrial wood at
cutting, keeps track of quantity
harvested wood and its
breed composition.

Feller
forests
Forest feller -
specialist,
engaged in
timber harvesting.

Table
yar
Carpenter - professional
worker, craftsman,
woodworker,
grinding and
making products from
wood or products based on
tree. The carpenter is engaged
carpentry work:
manufacturing complex
furniture, doors, windows, arches,
stairs and other products from
solid wood with
possible application
veneering, veneering,
lamination, without thread
manually. Carpenter performs
more precise, delicate work,
than a carpenter, and no less than
carver (or sculptor)
tree. The carpenter can
perform unique work
on microsimulation on
wooden base.

Furniture maker A furniture maker must have
some set of elementary
geometric knowledge, well developed
spatial thinking, good
eye and coordination of movements.
To successfully master the profession, he
aesthetic sense and
artistic taste, good eyesight and
color perception, scrupulousness,
thoroughness bordering on
pedantry, patience, good
memory for shades of different colors.

A carpenter
A carpenter -
profession, one of
the most ancient
crafts, which
associated with
mechanical
wood processing and
transformation
raw
wood in detail,
designs and
building materials

Builder
Construction profession
is very ancient.
Thanks to historical
architectural buildings
we can learn a lot about
life and culture of ancestors. Before
a lot of our days have come
structures, age
which is measured
for thousands of years. Your experience
construction masters
passed down from generation to
generation.
Every year in our country
being built everywhere
a large number of
various buildings. This and
residential complexes, and
cottage villages,
institutions, industrial
enterprises, etc. That's why
demand for the profession
the builder is obvious.
Engineering and design
personnel
Performers.

Master carver or
wood paintings
Wood carving -
view
arts and crafts
wow art
(also carving
is one of
species
artistic
wood processing
along with
sawing,
turning), and
also arts in
overall (this is an antique
folk craft).

Sawing machine
SAWING VSHCHIK,
worker, busy
sawing,
sawing something

Bond
ry
Boendar is a craftsman,
barrel maker, sometimes craftsman
for the manufacture of ship masts.
The craft is called cooperage. Previously
it was widespread
spreading. In the 21st century
the cooper's profession is still
necessary because real
wooden barrels are required for
production of wine and cognac.
Cooper with an ax and
other carpentry tools
adjusts the rivets of the barrel one to the other
another one, whittles them out, makes them
folds (zautori) with a zautornik, in them
drives the bottom in and ties everything together
wooden or iron
hoops.

Basket maker, master
wickerwork
Wicker weaving - craft
making wickerwork
from vine: household utensils and
containers for various purposes,
such as boxes, baskets, vases and
etc., furniture (tables, chairs,
chests, cradles), etc. Under
vine means any
natural material
plant origin,
capable under certain conditions
easy to bend, and
keep under normal conditions
form. Name of the material - "
vine" comes from
grapevine from which
weaved baskets. Often
the material for weaving is
willow twig, it is used for
weaving both in Europe and in
Asia, in addition, in Asia they weave
from a material such as rattan
and bamboo. Weaving technique
the vines may be the most
diverse.

manufacturing
musical
tools
(Stradivarius)
The guitar master is
narrow specialization within
profession "master"
plucked musical
instruments." To plucked
instruments other than guitars
include harps, harps, and
balalaikas, domras, etc.
Therefore, masters
production of these
tools are
guitar colleagues
masters
Another related one
specialty: violin
master - specialist in
manufacturing and repair
bowed musical
instruments (violins,
violas, cellos).

Wood defects
Wood defects are features and disadvantages
wood, both the entire tree trunk and individual
its sections, worsening its properties and
limiting the possibilities of its use.

To the main vices
wood include:
Cracks;
Insect damage;
Changing the shape of the trunk and
wood structure;
Knots;
Rot.

In most cases, metal is either durable or expensive and difficult to process. Working with it requires knowledge, skills, qualifications and responsibility. That is why professions related to metal are respected, which is why these professions are in demand on the labor market.

If you stretch your imagination, a connection with metal can be found in any profession. Even the announcer can read an important message with a hint of metal in his voice. But we will only consider professions that are directly related to this substance.

It would be interesting to go through the chain - from obtaining metal to producing finished products from it.

The difficulty is that different metals are “born” in different ways. Some lie deep in the earth in the form of polymetallic ores, such as gold, and then miners extract it, while others come to the surface and are mined open method.

Let's skip several stages associated with ore mining, enrichment, chemical or mechanical separation of the charge suitable for smelting.

Let's start with metallurgist profession – very difficult and very honorable. Difficult because you have to deal with huge volumes of metal, huge equipment that operates in a continuous mode and consumes a huge amount of energy.

Metallurgist is a very broad concept. It includes all professions associated with ore beneficiation and smelting pure metal.

Steelmaker in a steel or copper smelting industry or a galvanist who conducts the electrolysis of molten salt - metallurgists.

A metallurgist needs to thoroughly know all the intricacies of the process, have vast experience and a keen eye in order to catch the moment when the welded metal acquires the optimal composition. It is important not to miss this moment, otherwise the value of the melt and the grade of the resulting metal are reduced, material resources and the efforts of large teams are wasted.

Melting and pouring metal into molds is only the beginning of the path to obtaining a finished metal product.

Metal is supplied to processing plants in the form of pigs, sheets, rods or profiles of various sections. There, people who perform work related to metal processing deal with it.

Rolled products are produced at special rolling mills, where the billets pass through big number rotating shafts, gradually acquiring a cross-section of the desired shape and size. There are hot and cold rolled products. And the profession of people involved in the production of rolled products is called accordingly - rental company .

Not all smelted metal ends up in a tight embrace rolling mills. The part in the form of pigs is intended for smelting alloys. To melt them, various metals and other additives are placed in the furnace in the required weight proportions, which after smelting form one or another alloy.

The time has come to emphasize that the metallurgist is not only a worker at the furnace, but often a scientist who leads research work in order to obtain alloys with predetermined properties, or a scientist who seeks to develop a new, less expensive process for producing metal.

Another way for metal in ingots is to go into the furnace foundry worker . It is also a very difficult profession. In short, the foundry must prepare the mold, melt the alloy and, once the desired temperature is reached, pour it into the mold. You can pour the metal with a hand ladle (a kind of ladle) or a large mechanized ladle. Over time, the melt will cool and become strong. The mold is opened (or broken if it is one-time) and a part is obtained that is suitable for further processing. In some cases, the result is an almost finished part.

It's simple, you say. One could agree, but there are a lot of factors influencing the quality of the casting. Temperature and humidity in the room, the quality of the charge prepared for melting, the temperature of the alloy, the quality of the mold lubricant, the pouring speed and other “little things” affect the quality of the casting.

Metallurgists also include welder . People of this profession can concentrate the power of an electric arc, the heat of a gas or plasma torch flame, and Lately and focus the laser radiation so that local melting of the joined parts begins in the right place and their connection into an integral structure. It’s also not an easy, very necessary profession.

The construction of openwork structures from profiles, welding of containers from metal sheets, thousands of kilometers of pipelines and much more is impossible without a welder.

The number of methods of influencing metal in order to obtain parts and structures of a given shape and given dimensions is constantly growing.

Processing by cutting off unnecessary mass of metal - the so-called cutting processing - is carried out by workers of the following professions:

turners on lathes , including on machines with numerical control;
milling operators on milling machines different types, including on software-controlled processing centers;
locksmiths on drilling machines when drilling holes;
grinders on flat and cylindrical grinding machines;
tool makers (an outstanding category of specialists pursuing micron precision parts). In their work they often use non-standard devices, techniques, and tools. Relatives of the famous Lefty;
Borers on jig boring machines obtain calibrated holes in the parts in the right places.

Prefer pressure treatment blacksmiths, stampers . Drawing, die-cutting, hot-shaping, and, as a result, artistic forging products - this is the roughly outlined area of their activity.

Relatively new directions are laser and plasma cutting on special machines operating according to a program. It turns out that even programmer profession associated with metal.

It is not enough to manufacture a part or weld a structure. Often the properties of a metal are very sensitive to what the cooling regime was like after melting, whether it was quenched (or tempered) at a certain temperature in a certain environment.

Thermist - here is a person who can make a cutting tool from a soft blank. It will not allow cracks to appear in parts after casting.

Many parts, even under normal conditions, are eaten away by corrosion. Can protect the metal surface galvanizer, by electrochemically applying a layer of another metal to the surface of the part.

It would be worth mentioning people who test metal in laboratories, carry out rapid chemical analysis during technological processes, and conduct exploration of new deposits, but the length of the article forces us to stop listing professions. A complete list is impossible in principle, since this list is constantly updated.

Transcript

1 PRIMARY PROFESSIONAL EDUCATION B. A. STEPANOV MATERIALS SCIENCE FOR PROFESSIONS RELATED TO WOOD PROCESSING TEXTBOOK Approved by the Ministry of Education of the Russian Federation as a textbook for educational institutions implementing primary programs vocational education 7th edition, revised and expanded 1

2 UDC (075.32) BBK 38.35ya722 C79 Reviewer teacher of Construction College 12 (GOU SK 12) V.I. Zhiganova C79 Stepanov B.A. Materials science for professions related to wood processing: a textbook for beginners. prof. education / B. A. Stepanov. 7th ed., revised. and additional M.: Publishing center "Academy", p. ISBN The structure of wood and wood, the physical and mechanical properties of wood, defects and defects, wood species, classification and standardization of forest materials are considered. Data are provided on ensuring the durability of wood, adhesives and materials for finishing and protective treatment of building structures and joinery. Wood-based materials, wood parts and products, polymer products, roofing and cladding materials, metal products and fittings, thermal insulation and waterproofing materials, and materials for glass work are described. For students of primary vocational education institutions. UDC (075.32) BBK 38.35я722 The original layout of this publication is the property of the Publishing Center "Academy", and its reproduction in any way without the consent of the copyright holder is prohibited ISBN Stepanov B.A., 2010 Educational and Publishing Center "Academy", 2010 Design. Publishing center "Academy",

3 PREFACE The textbook is written on the basis of a block of educational elements for the federal component of the State educational standard for vocational primary education in the subject “Materials Science” for the training in institutions of vocational primary education of qualified workers in the professions: master carpentry, parquet work; master of carpentry and furniture production; woodworking machine operator; construction restorer. The textbook consists of 19 chapters. Chapters 1 through 7 include general issues, the study of which is necessary for all of these professions. Studying Chapters 8-17 is necessary for all professions, but to varying degrees. Chapter 15 is essential for carpenters and Chapter 17 for woodworkers. Chapter 18 is required for students of the profession of glazier carpenter, and Chapter 19 for the profession of woodworking machine operator. The textbook provides information both about traditional materials that have been used for a long time, and about new materials that have begun to be used recently, knowledge of the properties of which is also necessary for modern skilled workers. For clarity and better understanding of information, the textbook contains illustrations and tables. The data necessary in practice is given in the appendices, which also contain information of educational interest. The content of the textbook is given a practical orientation so that the knowledge gained can be most effectively used in the manufacture of products and work. 3

4 INTRODUCTION Wood is the oldest of all materials used by man. Almost everything that surrounded a person years ago was made of wood, but also modern world wood plays an important role. In terms of scope and variety of uses, no other material can compare with wood. Wood is used for the construction of buildings and structures for various purposes, the manufacture of joinery and construction products (doors, windows, floors, parquet, cladding, etc.) and furniture. Wood is used to make elements of bridges, ships, carriages, containers, sleepers, musical instruments, sports equipment, pencils, matches, paper, cardboard, household items, toys, souvenirs and much more. Natural and modified wood is used in mechanical engineering and the mining industry; it serves as a raw material for the pulp and paper industry and the manufacture of various board materials. Chemical processing of wood produces cellulose, wood alcohol, grape sugar, cellophane, acetic acid, wine alcohol, fur, leather, artificial fiber, photographic and film film, cotton wool, paper, turpentine, rosin and much more. Lumber, chipboards, wood fiber boards, wood boards, and plywood are the main construction materials for building structures and joinery products. Peeled and sliced veneer is widely used in the manufacture of joinery. Peeled veneer is used to make plywood, plywood boards, laminated veneer lumber, glued furniture parts, containers, and matches. Sliced veneer is the main facing material for parts made from low-value wood, plywood and particle boards, parquet and furniture. Wood is a natural polymer that has a combination of positive properties that allow it to be used so widely and variably in a wide variety of fields. Wood has high physical and mechanical characteristics, is easy and easy to process, and has a low volumetric 4

5 weight, high aesthetic qualities and natural decorativeness, low thermal conductivity, high strength with low weight, well resistant to shock and vibration loads. Structures and products made of wood, when properly designed, manufactured and used, are reliable and durable. Wood is relatively easily and simply connected with fasteners, glued firmly and reliably; remains beautiful for a long time appearance; is an environmentally friendly material; Protective and decorative compounds can be applied well to it. The energy intensity of manufacturing wood products is the smallest compared to other materials, which is especially important in modern conditions with ever-increasing energy prices. The uniqueness of wood as a material lies in the fact that it is the only renewable natural resource, unlike oil, coal, gas, iron ore and raw materials for the production of cement. Along with a set of positive properties, wood has a number of disadvantages: it is susceptible to rotting and burning, destroyed by insects and fungi, hygroscopic, as a result of increased humidity it can swell, and dry out when humidity decreases. In addition, wood as a natural material has biological defects that reduce the uniformity of the wood; they have to be taken into account. The disadvantages of wood can be overcome with proper design, manufacture, operation and use modern methods protection from rotting and fire. To effectively use wood, you need to know its structure, properties, defects, and main types of wood. But knowledge about wood alone is not enough, since in the manufacture of wood products they use various materials: adhesives, paints and varnishes, finishing and auxiliary materials, metal and plastic products, fittings, locking and fastening products, and much more. In order to produce high-quality products and perform work, a joiner, carpenter, parquet floorer, or woodworker requires good knowledge of work technology, product design and material properties. All this knowledge is closely interconnected. The type and properties of the materials used determine the processing methods and modes, the quality of the manufactured products, their appearance, strength, durability and cost. The structure depends on the materials technological process, set of necessary technological equipment and tools, the labor intensity of the work and the duration of the production cycle, the level of possible mechanization, working conditions and the necessary qualifications of workers. 5

6 The fact that the forest must be protected has become an indisputable truth. It would seem that for Russia, which has almost a quarter of the world's timber reserves, the problem of saving it is not relevant. However, the current structure of wood harvesting and the increasing cost of transportation from harvesting sites to consumption sites make the issue of saving and rational use of wood very important. Solving this important task of rational and integrated use of wood by processing it into useful and valuable products without any losses or waste is possible only by qualified craftsmen who have all the necessary knowledge and are constantly expanding their knowledge of modern materials. 6

7 CHAPTER 1 STRUCTURE OF TREE AND WOOD 1.1. Tree structure A growing tree consists of roots, trunk and crown (Fig. 1.1, a). Each part of a tree plays a specific role during its life and is used by humans for various purposes. The branches that make up the crown account for approximately 12%, the stump with roots accounts for 15%, and the trunk accounts for 73% of the total mass of the tree. The top of the trunk, together with branches and leaves or needles (in coniferous trees), forms the crown. Trees of different species have crowns that begin at different distances from the ground. The crown of cedar and spruce begins low above the ground. In an adult pine tree, the crown is located closer to the top. The crown of trees of different species has a different shape, for example, the crown of spruce has the shape of a cone, the crown of cedar has an ovoid shape, and birch has an elongated crown. Fig Parts of a growing tree: a growing tree; b sap flow in a tree 7

8 Leaves or needles absorb carbon from carbon dioxide in the air, water and mineral salts, which are provided by roots from the soil, and in the sun, as a result of photosynthesis, they form very complex organic substances from which the plant organism of the tree is built (Fig. 1.1, b). Leaves or needles are used to prepare vitamin flour, which is a valuable product for livestock and poultry farming. Branches and twigs are processed into industrial chips. Process wood chips are used to make fiberboards and containerboard. The other part of the tree is the roots. The roots hold the tree upright and supply the tree with water and mineral salts from the soil. The roots store the tree's nutrients. Some trees, such as oak, have roots that go deep into the ground, while others, such as spruce, have well-developed powerful horizontal roots located almost at the surface of the earth. The roots are used as secondary fuel. Rosin and turpentine are obtained from the stumps and large roots of pine after processing over a certain period after cutting down the tree. The third, main and most valuable part of the tree, which has the greatest economic importance, is the trunk. It supports the heavy crown and serves as a conductor for nutrients coming from the roots (upward currents) and from the foliage or needles (downward currents). The trunk, like the roots, stores the tree's nutrients. The shape of the trunk depends on the type of tree and the conditions in which it grows. For example, a pine tree grown in a forest has a straight and long trunk, while a pine tree grown in an open place has a short, thick and twisted trunk. When the tree reaches the maximum possible height for a given species and growing conditions, further growth stops (Appendices 1 and 2). The thin upper part of the tree is called the top, and the thick lower part is called the butt. Schematically, a tree trunk can be represented as a cone. The decrease in the diameter of a tree trunk from the butt to the top is called camber, or runoff. Coniferous trees have less camber than deciduous trees. The variety of trees grown in the forest is less than that of trees grown in the open. But even the trunk of the same tree at different heights has different camber: the closer to the top, the greater it is. A cross section of a tree trunk (Fig. 1.2) shows the bark, pith and wood with its annual layers. 8

9 Fig Cross section of a tree trunk: 1 core; 2 medullary rays; 3 core; 4 cork layer; 5 bast layer; 6 sapwood; 7 cambium; 8 annual layers The bark covers the entire surface of the tree and consists of two layers: cork and bast. The cork layer of bark located on the outside of the tree trunk protects the wood from frost, overheating, sudden temperature changes, mechanical damage and other external influences. The type, texture and color of the bark depend on the species and age of the tree. Tree bark comes in a variety of colors (white, gray, brown, green, red, black, etc.). For example, birch has white bark, oak has dark gray bark, and spruce has dark brown bark. The bark also differs in surface shape (smooth, lamellar, fissured, etc.). For example, fir has smooth bark, pine has scaly bark, juniper has fibrous bark, and birch has warty bark. The color and shape of tree bark change with age. Young trees have smoother bark than older trees. Depending on the species, age and growing conditions of tree species growing in Russia, the bark makes up from 6 to 25% of the trunk volume. The bark has many uses. It is used for tanning leather (willow and oak bark contains a lot of tannins), in medicine (in its natural form and for the preparation of medicines), dyeing (for the preparation of dyes), for the production of thermal insulation materials and materials for floor coverings. The bark, when properly processed, makes excellent compost for agriculture. Corks are cut from the bark of the cork oak tree. The bast layer of bark conducts water with organic substances produced in leaves or needles down the trunk. Bast, matting, and ropes are made from bast. Well developed bast layer 9

10 linden trees are used for weaving various household items. Between the bark and the wood there is a very thin succulent layer of living cells, invisible to the naked eye, called the cambium. Most of the cambium cells go to the construction of a new annual layer of wood and a very small part to the formation of bark. In the middle of the trunk of many tree species, the core is clearly visible, which consists of loose tissue formed in the first years of the tree's life. The pith permeates the tree trunk from the butt to the top and every branch of the tree. In most tree species, the core is visible on the end section in the form of a dark circle with a diameter of 2-5 mm. In some tree species, the core has a different shape, for example, the core of alder has the shape of a triangle, ash of square, poplar of pentagon, and the core of oak has the shape of a five-pointed star. On a radial section, the core is visible in the form of a straight or winding dark narrow strip. The main cuts of a tree trunk (Fig. 1.3): transverse P (end or butt) runs perpendicular to the longitudinal axis of the trunk, radial P runs perpendicular to the transverse through the core of the trunk, tangential T on the non- 10 Fig Main cuts of a tree trunk: P transverse (end ); P radial; T tangential

11 which distance from the radial. By sawing a tree across the grain, we get an end cut, and by splitting or sawing a tree along the grain, we get radial and tangential cuts. Macroscopic structure of wood Macroscopic is the structure of wood that can be seen with the naked eye. In order to better examine the macrostructure of wood, it is necessary to have a magnifying glass with five- or tenfold magnification, coarse-grained and fine-grained sandpaper, a jar of clean water and a brush. The section of wood that they want to examine is carefully sanded first with coarse-grained and then fine-grained sandpaper, then moistened with water using a brush and examined with a magnifying glass. Sapwood, heartwood, mature wood. Wood from forest species growing in Russia is usually painted in a light color. . In some species, the entire mass of wood is painted in one color (birch, hornbeam, alder), while in other species the central part is a darker color (pine, larch, oak). The dark-colored central part of the trunk is called the core, and the part surrounding the core is sapwood (see Fig. 1.3). Rocks that have a core are called core rocks. Species that have no difference between the central and peripheral parts either in color or water content are called sapwood. If the humidity of the central part of the trunk is less than the humidity of the peripheral part, then such wood is called mature, and the corresponding species are called mature wood. Of the tree species that grow in Russia, the core is: coniferous pine, larch, cedar; deciduous oak, ash, poplar, elm. Sapwood species include: maple, birch, linden, pear, hornbeam, boxwood, etc. Mature tree species include: coniferous fir and spruce, deciduous aspen and beech. Some hardwoods that do not have a core, e.g. in non-core species (birch, aspen, beech, maple, alder) sometimes the central part has more dark color than peripheral. In this case, the dark central part is called the false nucleus. Coniferous trees do not have a false core. eleven

12 Young trees of all species do not have a core and consist of only sapwood. Only over time does part of the sapwood transform into sound wood and a core is formed. The formation of the core occurs due to the death of living wood cells, blockage of water supply pathways, deposition of tannin dyes, resin, and calcium carbonate. As a result of these processes occurring in the sapwood, the color of the wood, density and mechanical properties change. The width of the sapwood depends on the type of tree and its growing conditions. In some tree species, the core is formed in the third year (yew, white acacia), in others (pine) in the th year of life. Therefore, pine has wide sapwood, while yew has narrow sapwood. The transition from sapwood to core can be sharp (yew, larch) or smooth (cedar, Walnut). In a growing tree, the sapwood plays the role of a conductor of water with mineral salts from the roots to the leaves, and the core performs a mechanical function. Sapwood easily allows water to pass through and is less resistant to decay than core wood. Sapwood is not recommended for the manufacture of containers for liquids. Annual layers, early and late wood. Concentric rings are visible in the cross section of the trunk, which are called annual layers of wood. On a radial section, the annual layers are visible in the form of parallel stripes, and on a tangential section in the form of wavy, winding lines (Fig. 1.4). Annual layers represent the annual growth of wood. The annual layers grow annually from the center to the periphery, and the outer layer is the youngest. The age of a tree can be determined by counting the number of annual layers along the radius in the end section on the butt. The width of the annual layers depends on the type of tree, its growth conditions and position along the length of the trunk. Fast-growing tree species form wide annual layers, for example, poplar and willow, while slow-growing tree species, such as boxwood, yew, and juniper, form narrow annual layers. The narrowest annual layers are located in the lower part of the trunk, and up the trunk the width of the annual layers increases, since the tree grows both in height and in thickness, and the shape of the trunk is close to cylindrical. For the same tree species, the width of the annual layers can be different. If the weather is favorable, then a wide annual layer grows, and when unfavorable conditions(lack or excess of moisture, lack of nutrients, possible

13 Fig. Annual layers on transverse (a), radial (b) and tangential (c) sections of rose pine wood) form such narrow rings that they are difficult to see with the naked eye. In some tree species, the growth rings are pronounced and clearly visible, while in others they are barely noticeable. As a rule, young trees have wider growth rings than older trees. The width of the annual layers also depends on the location of the tree. For example, the annual layers of pine growing in the northern regions are narrower than the annual layers of southern pine. Sometimes on opposite sides of the trunk the annual layers are of unequal width. For example, in trees growing on the edge or edge of a forest, on the side facing the light, the annual layers are wider than on the dark side. As a result, the core (or the center of the trunk, if there is no core) is displaced from the center of the trunk and the arrangement of the annual layers becomes asymmetrical. The annual layers, as a rule, have the form of rings, but some tree species have an irregular shape of the annual layers. On cross sections of juniper, yew, and hornbeam, wavy annual layers are visible. Each annual layer consists of two parts: early and late wood. Early wood is light in color and faces the core. Early wood is softer than late wood. Late wood faces the bark; it is darker in color and harder than the early one. The difference between early and late wood is pronounced in conifers and some deciduous species. Earlywood forms in spring and early summer when there is a lot of moisture in the soil. It grows very quickly, but as autumn approaches, growth slows down and, finally, in winter it stops completely. Late wood grows in late summer and early autumn and performs mainly mechanical work in the trunk 13

14 function, as if being the reinforcement of a tree. The density and strength of the wood as a whole depend on the amount of late wood. Core rays and core repetitions On the end surfaces of tree trunks of some tree species, light shiny stripes are clearly visible, running fan-shaped from the core to the bark; these are core rays (Fig. 1.5, a). All breeds have medullary rays, but only some are visible to the naked eye. They conduct water horizontally and store nutrients. The width of the medullary rays can be very narrow, not visible to the naked eye (in boxwood, aspen, birch, pear and all conifers); narrow, difficult to distinguish (maple, elm, elm, linden); wide, clearly visible to the naked eye in a cross section. Wide rays can be truly wide (in oak, beech) and falsely wide. Falsely wide rays seem wide, but if you look at them through a magnifying glass, you will find that it is not a wide ray, but a bunch of very thin rays that are collected together (in hornbeam, hazel, alder). The core rays are denser than the surrounding wood, and after wetting with water they become clearly visible. The core rays may be lighter or darker than the surrounding wood. In a tangential section, the rays are visible in the form of Fig. View of the core rays in transverse (a), tangential (b) and radial (c) sections of wood 14

15 dark strokes with pointed ends or in the form of lenticular stripes placed along the fibers (Fig. 1.5, b). On a radial section, the medullary rays are visible in the form of shiny stripes, dashes and spots located across the fibers (Fig. 1.5, c). The beam width ranges from 0.015 to 0.6 mm. The core rays create a beautiful pattern on a radial section, which is important when using wood as a decorative material. The number of medullary rays depends on the type of tree: deciduous species have approximately 2-3 times more medullary rays than coniferous trees. On the end section of wood of some species (birch, rowan, maple, alder), you can see chaotically scattered dark spots of brown, brown color, located closer to the boundary of the annual layer. These formations are called core repeats. Pith repeats are formed as a result of damage to the cambium by insects or frost and resemble the color of the pith. On longitudinal sections (radial and tangential), core repetitions are visible in the form of strokes and shapeless spots of brown or brown color, sharply different in color from the surrounding wood. Vessels On a transverse (end) section of hardwood wood, holes are visible, which are cross sections of vessels: tubes, channels of various sizes that conduct water in the tree. By size, vessels are divided into large, which are clearly visible to the naked eye, and small, invisible to the naked eye. Large vessels, as a rule, are located in the early wood of annual layers and, in cross section, form a continuous ring of vessels. Deciduous species in which the vessels are arranged in this way are called ring-vascular. In ring-vascular species in late wood, small vessels are collected in groups that are clearly visible due to their light color. In some types of wood, small and large vessels are evenly distributed across the entire width of the annual layer. Such breeds are called disseminated-vascular. In ring-vascular hardwoods, the annual layers are clearly visible due to the sharp difference in the color of early and late wood. In deciduous vascular species, the annual layers are poorly visible, since there is no sharp difference between late and early wood. 15

16 Fig Types of groupings of vessels: a, b, c ring-vascular rocks with radial, tangential and scattered grouping, respectively; d scattered-vascular grouping In deciduous ring-vascular species, small vessels that are located in late wood form the following types of groups (Fig. 1.6): radial in the form of light radial stripes reminiscent of flames (Fig. 1.6, a chestnut, oak); tangential small vessels form continuous or intermittent wavy lines extended along the annual layers (Fig. 1.6, b elm, elm); scattered small vessels in late wood are located in the form of light dots or dashes (Fig. 1.6, in ash). In Fig. Figure 1.6, d shows the location of vessels in a deciduous scattered-vascular species (walnut). The vessels are located evenly across the entire width of the annual layer. In radial and tangential sections, the vessels have the appearance of longitudinal grooves. The volume of vessels in different types of wood ranges from 7 to 43% of the total volume. 16

17 Resin ducts A characteristic feature of the structure of coniferous wood is the presence of resin ducts. They are channels filled with resin that penetrate the wood of pine, cedar, larch and spruce. Yew, fir and juniper do not have resin passages. Resin passages run in vertical (along the trunk) and horizontal (across the trunk) directions. Only vertical resin ducts can be detected with the naked eye, and the associated horizontal ducts are visible only under a microscope. Horizontal passages pass along the core rays. Vertical resin ducts are thin, narrow channels filled with resin. In a cross section, vertical resin ducts are visible in the form of light dots located in the late wood of the annual layers. In longitudinal sections, resin passages are visible in the form of dark strokes directed along the axis of the trunk. The number and size of resin ducts differ among different tree species. Cedar has the largest resin passages, with an average diameter of 0.14 mm. The diameter of the resin ducts in pine is 0.1 mm, in spruce 0.09 mm, in larch 0.08 mm. The length of the passages varies within cm, and in the lower part of the trunks of spruce and larch their length is twice as long as in the upper part. The largest number of resin ducts is found in pine, less in cedar and even less in larch and spruce. Resin ducts occupy a small volume of trunk wood (0.2–0.7%) and therefore do not have a significant effect on the properties of the wood. They are important when tapping, when the harvesters of resin (resin), the lifters, apply two rows of inclined cuts, called subcuts, to the tree. Resin is a valuable raw material for chemical industry. Turpentine and rosin are obtained from it, which, in turn, serve as very valuable raw materials. The resin is called resin because it heals wounds on the tree. In ancient times, resin was used for medical purposes. Microscopic structure of wood The microstructure of wood is a structure that can only be seen with a microscope. Examination of wood under a microscope showed that it consists of tiny particles of cells. The bulk (up to 98%) of cells are dead and only 2% of cells are alive. 17

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