Operational differences products from solid pine and spruce
Among consumers, you can find two opposing and well-founded opinions. Some consumers argue that it is better to purchase products from solid pine, according to their characteristics, they better meet modern requirements. Others, not without reason, argue that lumber was eaten somewhat better, and during construction work and the manufacture of furniture is more appropriate to use these materials. Where is the truth, which of them is right? In this article we will try to give an independent expert answer, we hope that you will agree with our opinion.
Hardness of some types of wood, MPa
The tree is construction material with the oldest heritage in Sweden. Because wood is used for a range of purposes in construction - structural frames, exterior and interior wall cladding, fittings, floor coverings, formwork and scaffolding, the list goes on - it is important to understand how wood behaves in different conditions. Due to its specific properties, each type of wood has typical areas of use.
The direction of the sip in a wooden structure under load
Spruce is a wood used primarily as construction timber. Pine is commonly used for joinery, moldings and interior cladding although spruce can be used. Hardwoods such as oak and beech are used in floors and furniture.
Some differences between lumber
To begin with, it must be said that according to their biological characteristics spruce and pine are considered very close relatives. As between any relatives, they have much more in common than differences, based on this, some lumber manufacturers do not even make a difference and sell lumber together. Of course, and at the same price. But there are also differences by which experienced builders and carpenters can easily distinguish between different boards. The first difference is the structural pattern of wood. In spruce, the knotiness is somewhat higher, but all the knots are significantly smaller in size. The second distinguish - the color of spruce wood is lighter, sometimes almost white, pine lumber has a darker appearance, the pattern of the structure is more pronounced.
Wood from southern Sweden is denser, stronger and stronger than wood from northern Sweden. This is despite the fact that southern Swedish wood tends to have wider growth rings than northern Swedish wood. The reason for this is that the group summer trees, the dark part of the growth ring, is wider in southern Sweden. Summerwood, who weighs 900 kg at cubic meter dry wood, three times denser than spring wood, which weighs 300 kg per cubic meter of dry wood.
Material properties vary between various types wood. Even within the same type of wood, there are significant differences between different locations, but also between different trees grown in the same place. However, there is still greater change within the same tree, for example between various heights in a tree, between wood that is close to bark and bark, and between ash and summer wood in separate growth rings. Knots and other fiber distortions also affect the technical properties of wood.
Spruce wood can sometimes have a faint single or yellowish tint, growth rings are quite expressive, late wood has darker shades, core rays almost invisible. Spruce is significantly less resinous. Resin pockets are rare and small in size. Spruce bends more easily, but it is somewhat more difficult to process due to a large number hard knots.
Normal variations in density, strength and stiffness properties in the same type of wood with an undistorted fiber structure. Density ± 20% Strength ± 40% Modulus of elasticity ± 35%. . Therefore, the coefficient is greater between, for example, the average strength of the wood material and the allowable operating stress compared to other building materials.
The composition and structure of the tree
The numbers without brackets indicate state properties parallel to the fibers, and the figures in parentheses indicate properties perpendicular to the fibers. All values refer to wood with a moisture content of 12%. Despite the differences between pines and spruces, they should be considered statistically equal in terms of construction time. Pines and spruces have a similar composition. In the center of the cross section of the rod sits the core, which runs throughout the tree and ends at the top with a bud. The key is in the wood, which can be divided into heartwood and sapwood.
Pine wood is never white, it always has different shades. yellow flowers sometimes turning into pink. The core is darker, over time the core will change its shade and may become brownish-red. The rock is sound, has resin ducts and resin pockets of relatively large sizes, resin ducts are mainly concentrated in late wood. The sapwood is quite wide, yellow or pink, the annual rings are clearly visible throughout the thickness of the wood, the core rays are hardly noticeable. The knots are large, mostly whorled, but there are also tobacco knots. Moreover, tobacco knots are much more common in pine than in spruce. Pine wood is less resistant to fungal infections, it often has a sapwood color.
Testing the mechanical properties of wood for bending
The waterlogged cells are also dead, except for about 5-10 percent, which are nutrient-carrying parenchyma cells. Since the sapwood cells are not clogged with resin, they can carry water and soluble nutrients from the absorbent root hairs into the needles of the tree. The moisture content of sapwood ranges from 120 to 160 percent. Behind the forest is the cambium, which is the growth layer of the stem. The cambium produces wood cells inward and bark cells outward. The cambium is enclosed in an eraser, often referred to as the inner bark.
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For the construction of log cabins, it is better to use pine, it has a higher density and resistance to atmospheric factors. For internal works it is better to take spruce, lumber has a noble white look. Moreover, the pine darkens over time, in some cases it becomes a little reddish, the color change occurs unevenly along the cut of the lumber. This quality can adversely affect the design characteristics. We briefly compared some of the performance characteristics of pine and spruce lumber, now we need to consider their characteristics in more detail.
This layer transports nutrients down the stem and distributes them to the living cells in the tree's branches, stem, and roots. The onion is connected to the poison through the medullary rays, which live in the sapwood but are dead in the heartwood. The outer bark covers the entire stem, providing protection against water loss and various parasites.
Wood also contains 2-6 percent extractives. The vast majority of them are resin acids, fatty acids, carbohydrates and minerals. These fibers are as thick as hair and are 5 to 6 mm long. The rest of the cells are shorter, with thinner walls.
Physical comparative characteristics lumber pine and spruce
- Density. The density of pine is 500 kg/m3, the density of spruce is 400 kg/m3, the data correspond to a relative humidity of wood of 15%. As you can see, pine is somewhat denser than spruce, which means that lumber from it has higher rates of resistance to physical stress. Although you must understand that for a tree, density indicators can vary widely, this is a living organism, and not a piece of iron. If desired, you can always find spruce lumber, which has a higher density than pine. The density depends on the age of the tree, climate zone growth, readings of average annual temperatures and readings of rainfall. Even malformations and the degree of wood infestation with fungal diseases affect the density of lumber. Together, these factors can change the density by 50% or more in one direction or another.
- Coefficient of thermal conductivity. This physical indicator has a direct dependence on density - the higher the density, the higher the thermal conductivity. This means that spruce retains heat better than pine. But in practice, these differences are so scanty that during the design of houses they are not taken into account. AT more thermal conductivity is affected by the relative humidity of lumber.
Mechanical properties. This indicator is characterized by several indicators. Strength - the maximum load that lumber can withstand before complete destruction. The degree of deformation - the ability of lumber to return to its original linear dimensions and shape after the removal of static loads. Wear resistance - the ability to withstand surface abrasion during periods of intense rubbing loads. Mechanical properties are directly related to density, the higher the density, the higher the mechanical properties. Pine has a slightly higher density, respectively, its mechanical performance is somewhat better.
Measurement of the hardness of wood, wood
During the growth period, new cells are formed in the cambium. Cells that form in spring and early summer are short and relatively wide, with thin walls. This means that the main density is low, about 300 kg per cubic meter. Due to differences in density, ash appears as a lighter ring than dark summers.
Strength, hardness and toughness of some types of wood
Density of wood, a key factor for many technical properties wood, is determined mainly by the ratio of summer wood to the width of the growth ring. Therefore, density narrowing based solely on the width of the growth ring is misleading.
For industry, there are several more indicators that are taken into account during production. various products from solid wood.
- Manufacturability. Quite a complex indicator, it has many components. The main ones include density and the presence of knots. Since spruce has more knots, it is somewhat more difficult to make products from it. But, on the other hand, pine has resin pockets, which have a rather negative effect on performance. cutting tools, the machines have to be stopped more often for technical care and cleaning the cutting edges from adhering resin. Another indicator that affects manufacturability is density. Higher density - more difficult to process the material.
- Variability performance characteristics. The properties of wood may vary depending on the height of the tree. The more stable these indicators are, the more technologically wood is considered. According to this indicator, there are no significant differences between pine and spruce.
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The way growth rings develop is determined in part by the climate during the growing season. Growth rings therefore tend to be narrower and have thinner bands of summerwood in colder climates than in warmer ones. In this way, one can see the performance of good and bad growth years and how growth conditions are affected by different forest management measures. Growth improves after thinning due to better access to light and nutrients, and vice versa, growth may drop if the tree grows too close to other larger neighboring trees.
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The width of the growth rings and the proportion of summer wood vary within the stem. In the inner part of the stem, in the young forest near the root, the growth rings are often wide with a thin ribbon. Thus, the density adheres closely to the wood close to the pit, compared to mature wood further along the stem radius. This takes place along the entire length of the tree.
The growth rings are narrower, with wider groups of summer wood, in the outer parts of the stem, especially in the lower logs. Thus, the proportion of summer wood is higher, which gives mature wood a higher density and strength. The lower parts of the stem must be stronger to withstand the stresses of wind and snow. Thus, the density in the butt log is higher than in the middle log or upper log.
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Wood is an anisotropic material, which means it has different properties in different directions. For example, wood is much stronger in the direction of the fibers, that is, along the length of the rod, than at a right angle, through the grain. This is the case if the load is caused by compression, tension or bending stresses in the wood.
Strength depends in part on the density of the wood and how well the direction of the fibers matches the direction of the forces that occur when the wood is under stress. The direction of the fiber deviates from the direction of the forces at the nodes and when the fibers are not parallel to the edge of the tree.
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When choosing a material for a product, it is necessary to take into account its mechanical properties: hardness, wear resistance, strength, deformability.
The strength is also affected by the moisture content of the wood, its temperature and the period during which it is subjected to stress. A dry piece of wood is stronger than one with more moisture, and colder wood is stronger than warmer wood. The longer the tree is under tension, the stronger its strength.
Fractures may be gradual or brittle. A brittle fracture is sudden and occurs without warning. A gradual break is preceded by some form of warning, such as major distortions or cracks in the wood. The strength of wood depends on how stress occurs, so there is the following correlation.
Hardness of wood (wood) - this is the ability of wood to resist the introduction into it of more solids. The hardness depends on the density of the wood and is not the same in all directions. End surface hardness deciduous species are higher than tangential and radial by 30%, in conifers - by 40%.
According to the degree of hardness tree species divided into three groups: soft - spruce, pine, cedar, fir, juniper, poplar, linden, aspen, alder, chestnut, willow; solid - larch, birch, beech, oak, elm, elm, elm (birch bark), plane tree, mountain ash, maple, Walnut, ash, apple tree; very hard - white acacia, hornbeam, dogwood, boxwood, iron birch, pistachio tree, yew
The strength of the wood cannot be fully utilized at the breaking limit, so lower stress levels must be chosen. This is because the properties of wood are so widely distributed, which means that protective fields must be created.
Some differences between lumber
In terms of strength, pine and spruce are treated in the same way and generally have the same strength values. Rigidity and hardness can also be included in strength properties. Stiffness is the opposite of bending or deformation. When a length of high stiffness wood is bent, it doesn't give very much while remaining fairly straight. The degree of bending depends on the grain of the wood and on its modulus of elasticity. A high modulus of elasticity means high rigidity.
wood hardness depends on many factors: its humidity, the content of late wood in the annual layers, the place of growth, the time of harvesting. For example, a 1% increase in humidity reduces end hardness by 3%, and tangential and radial hardness by 2%. The increase in late wood increases the density and improves the mechanical properties of the material. Pines grown in a dry place (straight high trunks) are harder than pines growing on swampy ground. The wood of a tree felled in December has a greater hardness than in February.
Hardness refers to the ease with which a surface is damaged by external pressure, such as heels on the floor or knocks on a table. The hardness of wood is greater with the grain than against it. The end grain surface is hard and durable as the surface is completely wood grain.
In addition to the direction of the fibers, the hardness of wood depends primarily on the density. AT wooden floors so spring wood wears faster than summer wood. Thus, wood high density must be selected for the floor. Wood has good thermal properties, and as thermal insulation material traditional wood is used. Thermal conductivity is greater in the direction of the fibers, and it increases with moisture levels and density.
hard rocks, as a rule, are more suitable for mechanical processing (drilling, turning, milling). They are used in the manufacture parquet, wall panels(lining), tools, devices. soft rocks use for manual processing using knives, cutters, chisels.
Measurement of the hardness of wood, wood
To measure the hardness of wood using the Brinell method, a steel ball with a diameter of 10 millimeters is taken and pressed into the surface, applying a certain force for a certain time. After that, the depth and width of the formed dent are measured and the hardness value is calculated. According to the Brinell method, the harder the wood, the higher the rate.
Compare Table 11 in this section. Numerous factors affect the combustion properties of wood, most notably the moisture content, dimensions, density and fiber direction. Time to ignition can vary greatly and depends on heat radiation, ventilation and the presence of an open flame. The lowest thermal radiation for igniting wood with an open flame is about 12 kW per cubic meter. More high levels thermal radiation is needed for ignition without an open flame. Burning wood generates a moderate amount of smoke.
According to the degree of hardness all tree species at 12% humidity can be divided into three groups:
- soft - pine, spruce, poplar, linden, aspen.
- solid - larch, birch, beech, elm, maple, ash
- very hard - white acacia, ebony, eucalyptus, dogwood, boxwood
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