What is wood and what is it like?

Wood has many functions - it is used to build houses and make furniture, heat rooms with it, it surrounds us everywhere. But what is wood in terms of physics or mechanics? How can it be used, and what flaws does it have?

Wood is called natural raw material, which is used for the production of various kinds of products and structures. If we talk about this material from the point of view of physics, then wood is a plant tissue, consisting of cells that adhere to each other with a high density. Because of this, the structure of the tree is dense and resilient. Tree cells (like any other living cells) have a shell. It contains cellulose, which makes the wood so durable. The cells are in the form of a tube - long and narrow, which is why they were given the name of fibers.

Wood has the ability to retain heat. This is due to the presence of voids between cells - it is they who retain heat and accumulate it. Inconsistent strength and weight are related to the size of the fibers. The thicker they are, the more durable the wood is.

It is easier to chop wood in the direction in which the fibers are located. It is easier to process wood of those species in which they are located in parallel. Maple trees are more difficult to process, since the structure of the maple has a close interweaving of fiber cells. But not only cellulose is found in wood cells. They also contain a very complex and mysterious substance called lignin. Thanks to him, the fibers are connected to each other. Scientists have not yet succeeded in deriving the chemical formula of lignin, it is so complex.

Wood has a unique shade and smell that distinguishes it from other materials. Both are due to the presence in the composition of resins, oils, in conifers - gums and other substances. These same elements help the wood fight decay. Wood is divided into two types of species - deciduous and coniferous. Both groups are very large. A separate group stands out - monocotyledonous trees, which include a palm tree, bamboo.

All characteristics of wood are divided into three large groups: physical, technological and mechanical.

Those properties that during testing do not lead to changes in the chemical composition of wood are called physical properties. These include the following characteristics:

• appearance;
• humidity level and everything related to its changes;
• thermal conductivity and heat retention;
• electrical conductivity;
• sound insulation and everything connected with it;
• changes that the material acquires after exposure to electromagnetic radiation.

The appearance is shaped by such components as color, gloss, texture and macrostructure. Color is the visual sensation that remains after the tree reflects a stream of light, or rather, from the spectral composition of this reflection. Color is extremely important to wood.They are guided by it when choosing the breed with which the room will be decorated, from which furniture, musical instrument, decorative and applied genre, etc. will be made.

The color of a tree depends on many factors - breed, age, region and climate of the area in which it grows. The color may well change under the influence of wind, sun, fungal infection, as well as moisture, especially if the tree has been in water for a long time. But many breeds have a unique tone that can be easily recognized by a specialist. Luster is the property of a tree to reflect a stream of light. In some breeds the sheen is stronger, in some it is weaker. Of the species growing in Russia, the strongest shine is found in oak, beech wood, as well as in trees such as white acacia.

The texture is nothing more than a drawing of a tree. It becomes visible after the anatomical elements are cut (annual rings, rays of the core, vessels). According to the width of the growth rings and the content of late wood, an assessment is made of how high quality it is. The tree-ring width is the number of layers contained in one centimeter, laid down in the radial direction at the end of the wood.

It is measured by direct or indirect methods. The easiest and most reliable way to measure the moisture content of wood is to dry it. It takes time, but the answer is accurate. As far as indirect methods are concerned, they are significantly faster. For example, measurements with a conductometric electric moisture meter show how much water a tree contains and what its electrical conductivity is. But the accuracy of such methods is low - a maximum of 30%, and then only where the needle for measurement was introduced.

The water in the tree can be free and bound. The first can be found in the cavity of the fibers and in the space between cells. The second is in the structure of the cell, it is held by physical and chemical bonds. If free water is removed from wood quite easily, then bound water is much more difficult to remove. If the lumber changes its shape during drying, sawing or storage, this is called warpage. Whatever it is caused, it leads to the appearance of wood defects, therefore, it must be stored and processed in accordance with the technology.

Wood has properties such as moisture absorption and swelling (as a consequence). This should be taken into account when working with him. It is not always negative, for example, in vats or barrels, the property of wood to swell and increase in size increases the density of adhesion of wooden elements to each other.

Wood has a density measured in kilograms per cubic meter (or grams per cubic centimeter). Different types of wood have the same density of woody substance (it is 1.53 g / cm3), but different density of completely dried wood. There are several indicators of density - wet wood has one density, and dry wood has another. Wood has such a characteristic as porosity, that is, the degree of filling of empty cavities with air. The porosity of different rocks ranges from 40 to 80%.

The permeability index means how much of a liquid or gaseous substance wood is able to pass under the influence of pressure on it. Separately, among the physical properties of wood, thermal properties are distinguished, which include heat capacity, the ability to conduct heat and expand under its influence, as well as the ability to conduct temperature. The tree has the property of electrical conductivity, that is, an electric current passes through it. The drier the wood, the worse it conducts electricity, and vice versa.

This category of wood properties includes parameters such as hardness, wear resistance, toughness, retention of various types of fasteners, as well as the ability to process the material with cutting tools. Impact toughness is the property of wood to absorb the force applied to it during impact without changing the structure of the material. High viscosity means that it takes a lot of force to break the sample.

Hardness refers to the ability of wood to resist a harder body when pressed. The harder material for wood and hardness testing is steel. The hardness is determined using the scale of the force meter. The wear resistance of wood is indicated by its property of resistance to wear during its friction against a surface with an abrasive coating. There is a special formula for calculating the abrasion rate.

Wood is capable of resistance under the action of forces applied to it, that is, it has mechanical properties. These include strength, resistance to deformation, technological and operational properties. The mechanical properties of wood are determined in tests such as tension, compression, bending and shear. Wood is classified as anisotropic material, which means that it has different properties in different directions.

Ultimate strength is the maximum allowable stress level that precedes the onset of fracture of the sample. It must be determined on a sample that is free of defects, small in size and clean. In order to determine the compressive strength of wood, you need a sample that has a prismatic shape.

Deformability is the ability to withstand short-term loads without changing the original shape. Due to its elasticity, wood is able to return to its original shape after short-term loads. The elastic modulus is calculated using a special formula. The structure of wood is such that it can deform under constant loads. It is important to know exactly both the strength index and the limit of additional resistance, as well as the endurance limit (for samples subjected to alternating loads).

There are a lot of wood species, when choosing a material for construction or processing, one should take into account the individual characteristics and properties of each. Wood is divided not only into well-known groups of deciduous and coniferous species. For example, there is a classification of wood by color. Depending on the species, the colors of the wood differ. The color of a tree depends on several factors. This is the breed, age, the rate at which the tree grows, as well as the amount of dyes it contains.

Brightness is also directly related to the latter factor. The sapwood of the tree (the outer part, which contains living cells), the tone is always lighter than that of the core. In the core part, in which tannins and resins are concentrated, the shade is much darker. Accordingly, in heartwood the wood is darker, in sapwood it is light.

The former include larch, pine, ash. The second, with a narrow core - birch, pear, linden, alder. Of those listed, birch has a completely white shade of wood, while the rest have a very light woody. This is also due to the fact that starch is present in the sapwood. Sapwood is used for the manufacture of parquet boards.

Conifers are used to create lumber and other building components. They have a lightweight and easy-to-handle structure. A large number of coniferous trees grow in Russia. As for hardwoods, they are used to create furniture and furnishings.

Certain tree species have a higher value, they are called valuable. The value lies in the fact that these rocks have much higher strength, they last longer and have a unique pattern. These varieties are used to create beautiful elite furniture, parquet boards, doors, and other decor items. They all cost significantly more than conventional products in the same category. Domestic valuable species include cherry, oak, pear, rosewood, as well as white or holly maple wood.

Wood is also distinguished by signs of liquidity and illiquidity.

• Liquid wood - it is used for household needs. Liquid timber consists of commercial timber and firewood. In turn, commercial timber includes round and chipped timber, but does not include firewood. In the composition of industrial wood, technological chips and stump resin are also distinguished.
• Illiquid wood - one that cannot be used for economic purposes due to the fact that it has lost its technical qualities due to natural defects or processing defects.

The defects of wood are called those defects that it has. This applies to the entire trunk and its individual elements. The flaw must necessarily degrade the quality of the wood, limiting the possibility of its use. All types of defects and defects are listed in GOST 2140-81. Anything that deviates from the normal structure of wood is considered a defect.

Vices are natural, which arise regardless of the will of a person (exposure to climatic factors, birds, insects, rodents, bacteria, etc.), and there are processing defects, which include those defects that arise as a result of improper processing, storage or storage of material.

Vices can be both conditional and unconditional. Such a defect is considered unconditional, which significantly reduces the quality of lumber, such as rot or fungus. Knots are the most common defect, but structural defects in wood are also common. The gnarled trunk can be used, for example, for original decor, but it does not cease to be a vice. The number of permissible knots includes no more than two knots per meter of timber length, while the knots must be healthy.

Defects in processing include everything that damaged the wood during mechanical impact on it., namely - sawing, harvesting, warehousing, storage, transportation, etc. It is as a result of mechanical impact that wood suffers most often, acquiring disadvantages that it initially did not have.

Wood is used in many areas of industry, being one of the most environmentally friendly and at the same time inexpensive materials.

The last decades have shown the importance of using renewable minerals and resources. The latter includes firewood used as fuel. The growth in the use of firewood for heating premises has been recorded all over the world, and Russia is no exception. Fuel pellets (pellets) and fuel briquettes are made in almost all regions of the country where there are forests - no matter whether coniferous or deciduous. Charcoal also became suddenly popular, although it was previously undeservedly forgotten. Now it is widely used in everyday life and at work.

Country houses in the overwhelming majority of cases today are erected from wood. The advantages of wood are undeniable: it is environmentally friendly, natural, has an attractive appearance and makes it possible to create a lot of designs - from a classic Russian hut to an alpine chalet. They build from wood not only houses, but also baths, saunas, gazebos. Wood is used in housing construction and in load-bearing structures, beams, ceilings. In rural settlements, low-rise houses are still being built from wood - for 2 or 4 owners.

The woodworking industry is now striving to increase the resistance of sawn timber to moisture, fire, strength, and also to improve the compliance of timber and boards with building codes. But at the same time, wood should remain a natural, breathing material, retain a unique pattern and its inherent aroma. New processing and construction technologies are constantly appearing, for example, the construction of houses using double timber technology is a relatively new phenomenon that is only gaining popularity in Russia.

Besides construction, wood is widely used as a structural material for furniture production. - sofas, chairs, tables, wardrobes and more. Stairs, railings, platbands, balusters, paths and sidewalks in the garden, and other decorative elements in landscape design and in buildings are made of wood.

Both amateurs and professionals are engaged in applied art today. Wood is used for crafts in its most varied forms - from sawdust and slabs to bars and parquet boards. Craftsmen with golden hands and from wooden boxes or pallets will create a garden chair - Adirondack, which will look no worse than a factory one. From the cuts, both original walking paths in the garden are obtained, as well as magnificent cutting boards or pictures burned with a jigsaw.

Although a tree is a renewable natural resource, it takes several decades for a forest to fully recover. Deforestation and forest fires negatively affect climatic and environmental conditions and reduce the amount of the resource available for use. Therefore, wood is recycled in order to reuse it in production, as well as to process the resulting waste.

Wood can be divided into business and non-business. The first includes, for example, the slab and under-saddle boards. The second includes veneer and slabs, more precisely, their remains, saw cuts of logs, various pieces and scraps from carpentry activities, and bark, sawdust, shavings and dust are also referred to non-business wood. Commercial wood is used to create new products. Non-business is subject to collection, additional processing and subsequent disposal. Although in relation to non-commercial wood, developments and search for ways of processing are being carried out. For example, shavings and sawdust are compressed, after which they are made into cat litter.