- Review of physical properties
- Moisture absorption
- Sleeping and swelling
- Internal stresses
- Manifested when exposed to emissions
- Description of mechanical properties
- Quality coefficients
- Features of technological properties
Know everything about the properties of wood, and not just what it happens on hardness is useful and for general development, and for the immediate organization of different production. It is necessary to pay attention to technological properties and humidity. But also standing in advance, what useful properties has wood.
Review of physical properties
Wood coloring largely depends on the degree of saturation of tanning substances. Therefore, it is clearly tied to climatic and soil features of various locations. The main rule is simple: the more solubility of mineral salts, the darker it turns out. But what kind of color has a specific tree, depends on:
- receipts of mineral salts;
- features of production in production;
- moisture degrees;
- illumination characteristics;
- burnout over time;
- lesions fungi.
Physically, this parameter expresses the degree of directional discarding of the light flux. The smoother surface of a particular sample, the higher. No wonder they are polished as the board and panels, almost independently of the initial breed, are glittering especially. But still the features of the breed are always an imprint on the nature of such brilliance.
And again, it is necessary to take into account the unequal manifestation of this parameter with different illumination.
In many ways, this property is considered to be determining the appearance of the wood as a result. Under the texture implies a specific pattern. It is usually detected not on the surface, but on the cut. The texture affects:
- already mentioned color;
- Features of fibers and their location;
- annual rings;
- Pigments inside.
Specific fragrance – hardly the most pleasant property, which has wood. The maximum strong smell is characteristic of the nucleus, because there is the most high concentration of aromatic substances. Just a fired tree smells stronger, then everything is weaker. After some time, it is almost impossible to catch this smell. It is most attractive in such instances:
- lemon tree;
- Yellow Tree.
So called the structure of the tree, detected or when considering the naked eye, or with a slight increase, for example, with a magnifying glass. It is possible to notice the macrostructure on any slices of trunks. Core, Cambier and Actually Wood – All these are parts of the macrostructure.
This also includes annual rings, allowing to judge the age of a tree, about what conditions it grew and developed.
This indicator usually passes as negative because The less he, the easier it works with a tree, the predictable other parameters and the more reliable the finished product. Fresed wood has a sufficiently high degree of humidity. Under normal conditions – the temperature of 20 degrees – the tree can be absorbed from the external environment to 30% of water in absolute calculus. It cannot exceed this indicator in a natural way if there are no special circumstances that increase the saturation of liquid to 50 or even up to 100%. What is noteworthy, it almost does not depend on the breed and even from the region of origin.
The norm according to GOST is simple: if the water content is below 22%, then it is a dry lumber, and at a higher concentration, it is referred to as a humid category. However, for practical purposes, limit the similar standard level, of course, it is impossible. In addition, it is necessary to remember that according to the GOST, the water content in the 4th grade wood is not normalized. The definition of this indicator is made in various ways. In professional purposes, it is measured using a special device – an electrolylavera.
However, experienced joiners and carpenters can rather high accuracy determine the moisture. Of course, it is not enough to draw up documentation on the quality of the party of this party, but it is enough for the selection of sawn timber for construction or furniture production.
Checking moisture can be used using weight test. Usually, air-dry wood is considered normal, the humidity of which does not exceed 15-20%. Most often to achieve such a result, you need more or less long drying.
Wet consider tree with a humidity of more than 100 percent (according to the weight gain of the mass due to a reference). But this is possible only with long finding in water. Normal consider humidity from 30 to 80%, Although, of course, it does not seek to reach the top limit, but try to use a more dry sawn timber, ideally – no more than 12%. The calculation is made by a fairly simple formula.
The initial moisture indicator is determined by subtracting from the initial mass of the mass, which will be in a completely dry state, and then divide it to an absolutely dry mass and multiply 100%. It must be understood that even if the surface of the dryness, then the fair amount of moisture can remain inside. In some cases, you can hear about the so-called equilibrium moisture. It implies such a state when the pressure from the external environment is fully equalized by pressure from the liquid, concluded in the pores and cells. This indicator, like other types of saturation with water, directly affects the suitability of raw materials for certain practical purposes.
With increasing moisture lumber:
- becomes essentially wider;
- somewhat extends;
- In combination with increasing temperatures, plasticity acquires;
- For a long time (comparable with the usual service life), it is faster and degraded, more often and actively rotates.
But the water is not only contained initially, but also comes from the outside throughout the time of use of products. The intensity of its absorption is just called moisture absorption. During water adsorption, some heat is released.
But gradually this process will slow down. When approaching the saturation limit, it generally flows extremely slow way.
We are talking about passing the so-called connected water. The coefficient of moisture conductivity takes into account the movement of both the actual liquid and the vapor phase. It occurs through:
- cell cavities;
- intercellular spaces;
- Capillary systems of cell shells.
Sleeping and swelling
When professionals utter the word dewushka, it is deprived of any ironic shade. This is quite a serious term meaning the degree of reduction in the size of the wood or the product from it when removing the moisture there. For each breed and even for a particular density level, this indicator may differ significantly. In different geometric directions, the dewushka goes inhomogeneously. The physical meaning of the swelling consists in the penetration of water molecules inside the cell walls and in the spout of the cellulose fibrils, such a phenomenon is predominantly characteristic of the wood moisture and subjected to seasonal.
In natural state, any trunk of a tree is rolled balanced, even if he has to develop crooked. But when the same barrel cut down, the wood “leads” because these stresses are broken out due to control, lose all harmony. The strongest of them are revealed immediately as soon as the barrel is split. However, sometimes the problem reveals itself much later, after drying the boards and their attachments in the design created.
It is visually expressed in the appearance of various cracks, the problem of the problem is the right industrial drying, and that is why it is impossible to assume that it only raises the price as often thinking.
This is a mass rate of some piece of wood. Important: it is calculated, specifically ignoring the mass of emptiness and the moisture contained, only the clear severity of the dry matter is important. For each breed, the density is strictly individual. This indicator is closely related to the following parameters:
- absorption level;
- exposure to biological damage (the more denser the sample, the harder to damage it).
The ability of wood to transmitting liquids and gases to underestimate. It directly affects the development of drying and impregnation modes, to assess the feasibility of such modes. The permeability of water is determined not only by the tree of wood, but also by the location in the trunk, and the direction of movement of liquids, gases. Permeability along the fibers differs significantly from the intensity of penetration across the fibers. It is also worth considering and an important role of resinous substances that interfere with the flow of water and other liquid substances.
Permeability for gases is defined as the number of past air. It is measured in terms of 1 cubic. cm Sample surface. This indicator is determined:
- properties of the wood itself;
- Properties of vapors or gases.
They are most often mentioned among the beneficial properties of natural material. But in reality, the situation is somewhat more complicated than just “good heat retention”. The specific level of heat capacity is not so much dependent on the breed and density. It is determined primarily by ambient temperature. What it is higher, the greater the heat capacity, the dependence is practically linear.
It is worth paying attention to the temperature and thermal conductivity. Both of these properties are directly related to the density of the substance, because each cavity containing air plays an important role. The denser of the tree, the higher its thermal conductivity. But the thermal conductivity index, on the contrary, falls sharply with an increase in the specific mass of the sample.
Cells and fibers passes more heat in longitudinal than in the transverse direction.
But sometimes wood use both fuel. In this case, thermal efficiency is critical. For absolutely dry wood, it ranges from 19.7 to 21.5 MJ by 1 kg. The appearance of moisture, even in small quantities, dramatically reduces this indicator. Bark, with the exception of birch, burns with the same temperature as wood herself.
When using wood as a fuel, such a thermal property of wood, as the heat of combustion (calorific value), which is absolutely dry wood 19.7-12.5 MJ / kg. The presence of moisture strongly reduces its meaning. The heat combustion of the bark is approximately the same as wood, except for the outer layer of birch bark (36 MJ / kg).
The overwhelming majority of builders are interested only and exclusively by the ability of the tree to absorb foreign sounds. What it is higher, the better the material will protect the house from street noise. However, in the production of musical instruments, such a property plays a major role as resonation.
Professionals still study the emission constant, it is an acoustic constant. It is according to it that the suitability of a certain breed or even a specific sample to practical use.
It’s above all, About electrical resistance and electric strength. The degree of resistance of the current is determined by the breed and direction of fibers. However, the temperature and level of humidity predictably play an important role. Under electrical strength, it is customary to understand the necessary tension of the electric field, which is enough for breakdown. The stronger the tree heated, the higher its temperature, the lower the resistance to such a breakdown.
Manifested when exposed to emissions
In case of infrared radiation, the surface areas of wood can heal greatly. It is necessary, however, a very strong impact of this kind to change the trunk of a thick tree for the entire depth. What is curious, the penetration of visible light occurs much deeper – by 10-15 cm. Features of light reflection make it nice to judge the defects of the material. Ultraviolet penetrates wood bad.
But it provokes a specific glow – luminescence. X-ray radiation allows you to detect even small structure defects. It is often used for professional diagnosis. Beta radiation is used to study growing trees. Gamma rays allow you to detect very deeply hidden defects, rot, and so on.
Description of mechanical properties
So called the ability to resist destroying when the load is applied. The degree of strength depends on the magnitude of the bound moisture. What it is higher, the lower the resistance to mechanical stress. However, after overcoming the boundary of hygroscopicity (approximately 30%), this dependence disappears. Therefore, the comparison of the strength of the samples is allowed only when an identical degree of moisture.
Resistance is necessarily measured not only along the fibers, but also in radial and tangential directions.
Almost everyone knows that the tree is of different hardness, and that This is one of the main indicators when selecting it for specific purposes. Specialists determine the hardness as the power of resistance to the introduction of foreign objects, including hardware. In addition to the list or scales by breeds of coniferous and deciduous trees, there is also its classification on the area of hardness. Fantastic The hardness is set by pressing the rod from the metal with a certain diameter and the end form to a given radius depth smoothly for 120 seconds. Evaluation is made in kilograms per square centimeter.
Also distinguished radial and tangential hardness. Its indicator in the side plane in the deciduous board is almost 30% lower than from the end, and for a coniferous array, the difference is usually 40%. But much depends on the specific breed, from its state and storage features. In some cases, hardness is measured by Brinell. In addition, experts always take into account how hardness can be switched in the processing process and when used.
The most strong tree in the world is:
- Amazonian yarra;
But just figure out what kind of wood is most powerful, not destroying, far enough. It is necessary to pay attention to other significant aspects. First of all, the relationship between mechanical parameters and volumetric mass. The harder wood, the usual better mechanics. The corresponding relationship is described by a number of complex formulas. But to take into account certain conditions and places of growth, additional correction coefficients are introduced.
Weight profitability reflected by the coefficients:
- general quality;
- qualities in statics;
- Specific quality.
Features of technological properties
The main technical properties of wood, along with the hardness already mentioned, are:
- shock viscosity;
- The effectiveness of retention of hardware;
- tendency to splitting;
- Wear resistance.
Viscosity characterizes the absorbed work when hit, which does not lead to the destruction of the material.
The test is carried out on special samples. It uses pendulum copers.
The pendulum in the raised state is intensifying potential energy. After vacationing in unhindered movement, it rises for one height, while spending a part of the pulse to destruction of the sample, – to another height, it allows you to determine the cost of effort.
Instruments usually equip a special scale. Considering the testimony, they substitute them into formulas, and in this way, the impact viscosity is obtained. It should be understood that we are talking about comparing the quality of samples, and not about the calculations of wooden structures. It has been established that deciduous rocks are more viscous than the coniferous array. As for the deduction of hardware, it depends on the friction force arising between the material and the fastener entered into it.
Additionally, the so-called pulp of resistance to pulling. In addition to the density, it is still determined by the wood of wood and the fact that the methome is in the end or across the fibers. Moisturizing the tree, it will be possible to simplify the same nails, but the dried material keeps them worse. Resistance to bending effort has to be evaluated mainly in cases where the bending is technologically necessary to obtain some product. Standardized method for evaluating this indicator not developed.
Wear resistance is almost always defined as friction resistance. Only in rare cases, the impedance is played by other wearing impacts. It is important to understand that it is estimated on the surface layer. If the destruction has reached the core, it makes no sense to learn the topic – the consequences and so understandable. The standard method for evaluating wear resistance is provided in GUT 16483 from 1981.