Not so comfortable on your good old mattress anymore? Are protruding springs or other internal structural elements bothering you to sleep? Has your mattress lost its former firmness? It's time to buy a new mattress. Let's try to figure out what they are and how to choose the right mattress.

Which mattress to choose, orthopedic or anatomical?

Many manufacturers and store managers love to pronounce these terms. Let's see what they mean.

Orthopedic (from the word ortos - which means straight, correct) surface is designed for the correct position of your spine during sleep. The most obvious prosthetic surface will be a straight board. Such a bed is unlikely to suit most of our readers, but from the point of view of the spine, this is what we need.

The second, softer way is the anatomical surface (it follows the contours of your body). This effect can be achieved using a soft, independent base that will proportionally distribute the person's weight.

The surface follows the contours of the body

With regard to our "rams" (oh, that is, mattresses), anatomical and orthopedic are one and the same: a comfortable mattress that takes the shape of the body.

A good mattress must combine two opposing qualities. Be soft and tough at the same time. The rigidity of the structure is determined by the frame, and the soft component is determined by the sheathing layers.

Consider the main design solutions for mattresses

Conventional spring mattresses- the most budgetary option.

The base is made of large diameter springs interconnected (the correct name is a bonnel-type spring block). In this design, each spring is dependent on its neighbors. If you press on any spring, then the pressure will spread to the neighboring ones (because they are rigidly connected to each other), which leads to undesirable deformation of the mattress surface. Such models are inexpensive, but their orthopedic component is not up to par.

When choosing such a mattress, you should pay attention to the number of springs. Manufacturers in pursuit of low cost can save money by reducing the number of springs, which will inevitably affect the quality of the product. The average is considered to be at least 100 springs per square meter of surface. For more expensive models, the number of springs can be up to 150 and even higher.

The first orthopedic mattresses on independent springs appeared in America at the beginning of the last century.

Their main difference from traditional mattresses is that each spring is in a separate cover and does not affect its neighbors. This design suppresses vibrations and distributes the load more precisely, which has a positive effect on the orthopedic properties. As with dependent springs, pay attention to the number of springs per square meter of structure. For simple models, their number is 250 pieces, for more expensive models it reaches 500 and more.

Springless mattresses are made of various materials.

Natural materials (latex, coconut coir, felt, wool), synthetic materials (polyurethane foam, artificial latex) or their combination can act as a filler. Orthopedic properties in such mattresses directly depend on the quality of the materials used in the filler. Of course, it is preferable to choose natural materials, but such a mattress can hurt your wallet.

Many springless models are delivered in a vacuum package rolled into a roll, which allows them to be transported even in a passenger car.

What to look for when choosing a mattress

There is a simple way to determine the quality of a mattress. If you put a mattress against the wall with a short edge to the floor and it will stand level without losing its shape (it will not begin to roll under its own weight), then consider that this instance passed the first exam. You can proceed to field tests. Lie down on the mattress (without a share of embarrassment), fall apart, as you are used to at home. If it is convenient for you, then the second exam is passed. If the model is double-sided, then repeat the second exam for the back of the mattress. Pay attention to the seams, stitching, whether the fabric is well quilted, whether the handles are tightly sewn (handles are needed to turn the mattress).

Mattress hardness should be discussed separately. The more body weight you have, the more firm the mattress you will have to choose. So a person weighing 60 kg will feel comfortable on a soft mattress, and for a person weighing 120 kg, the same mattress will more resemble a hammock. A firm mattress may also be needed on the advice of a doctor. There are two-sided mattresses on sale with different firmness. Basically, these are springless models (in spring mattresses, to obtain different stiffness on each side, manufacturers sometimes use different lining materials, but only springless models can provide a feather bed on one side, and only springless models can provide you with an elastic bed on the other).

When choosing a mattress, pay attention to the cover. If the design provides for the removal of the cover, then this is another plus, tk. it can be periodically washed or dry cleaned.

Another feature that is relevant for residents of the middle lane is double-sided covers of the winter-summer type. In such cases, one side is intended for use in the summer (usually made of lightweight material), and the other is insulated for the winter period.

As upholstery for the cover, modern manufacturers use a fairly wide range of fabrics: from synthetics to natural materials. When choosing the base of the mattress, it is advisable to give preference to natural fabrics, because they are the least allergenic.

Anti-friction materials

Plain bearings – antifriction(low coefficient of sliding friction) and fatigue resistance. The mating part is a steel or cast iron shaft.

Antifriction provided by such material properties as:

High thermal conductivity.

Good wettability lubricants.

The ability to form protective films of soft metal on the surface.

Break-in- the ability of the material under friction to easily deform plastically and increase the area of ​​actual contact.

Assessment criteria for bearing material:

Friction coefficient.

Permissible load-speed characteristic - pressure acting on the support and sliding speed: parameter pv (specific power of friction).

Metallic materials

The materials are designed to operate in the fluid friction mode - boundary lubrication mode. Overheating can destroy the boundary oil film, therefore the material must resist grasping... For this, the alloy must have a soft component in its structure.

Structurally, metal antifriction materials are divided into two types:

Soft matrix and hard inclusions.

A) The matrix provides a protective reaction of the bearing material to increased friction.

B) Good earning capacity.

C) Surface micro-relief, which improves the supply of lubricant to the surface.

Solid inclusions provide wear resistance.

Hard matrix and soft inclusions.

First type- babbits, bronzes and brass (copper-based alloys).

Babbits- alloys on a tin or lead base - B83 (83% Sn, 11% Sb, 6% Cu) on a tin base; B16 (16% Sn, 16% Sb, 2% Cu) lead-based. Lead-calcium babbits (BKA, BK2) are cheaper. Babbits are the best alloys in terms of antifriction properties, but they do not resist fatigue well 1. Therefore, babbits are used in the form of thin coatings (up to 1 mm) of the sliding bearing working surface.

Best babbits- tin (pv = 50 - 70 MPams), but they are expensive and are used in critical junctions. The structure is a solid solution of antimony in tin (soft phase) and solid intermetallic inclusions (SnSb, Cu 3 Sn).

Bronze- the best antifriction materials. These are tin bronzes - BrO10F1, BrO10Ts2, and tin-zinc-lead - BrO5Ts5S5, BrO6Ts6S3. They are used for monolithic plain bearings. They are used as components of powder antifriction materials or thin-walled porous coatings impregnated with a solid lubricant.

Brass- inferior to bronzes in terms of antifriction and strength properties, but they are cheaper. They are used at low sliding speeds and low loads (LTs16K4, LTs38Mts2S2).

The second type of alloys – lead bronzes(BrS30) and aluminum alloys with tin(A09-2 - 9% Sn, 2% Cu). The soft component is inclusions of lead or tin. During friction, a thin film of soft, low-melting metal is applied to the surface of the shaft, which protects its neck. Monometallic inserts are cast from aluminum alloys, bronze is used for surfacing on a steel strip.

Cast iron also belong to the second type of alloys, where the soft component is graphite. They are used at significant pressures and low sliding speeds (SCh 15, SCh 20, antifriction cast irons - AChS-1, AChS-2, AChV-1, AChV-2, AChK-1, AChK-2). Cast iron is selected so that its hardness is less than the hardness of the steel shaft. Advantages of cast irons - low cost; disadvantages - poor breakability, low shock resistance and sensitivity to lack of lubricant.

Multi-layer bearings. Steel provides strength and rigidity to the product; the upper soft layer improves the running-in ability, after wear of which lead bronze becomes the working layer; the nickel layer prevents the diffusion of tin from the top layer into the lead bronze.

Non-metallic anti-friction materials. Textolite, nylon and especially fluoroplastics (F4, F40) - have a low coefficient of friction, high wear resistance and corrosion resistance. Disadvantages - low thermal conductivity of polymers, aging, and fluoroplastics with a very low coefficient of friction (0.04 - 0.06 without lubrication) - “flows” under load.

Combined materials.

1. Self-lubricating bearings. Material - iron-graphite, iron-copper (2 - 4%) - graphite, bronze-graphite. Graphite - 1 - 4%. Products are manufactured by powder metallurgy methods and after sintering they have a porosity of 15 - 35%. The pores are filled with oil. With an increase in friction, the bearing heats up, the pores expand and, at the same time, the supply of lubricant to the friction zone increases. Bearings operate at low sliding speeds, without shock loads and are installed in hard-to-reach places.

2. Fluoroplastic bearings... The four-layer tape consists of an upper - a running-in layer of fluoroplastic filled with MoS 2 - 25% of the mass. thickness 0.01 - 0.05 mm; the second layer - bronzofluoroplastic - porous bronze BrO10Ts2 in the form of spherical sintered particles, filled with a mixture of fluoroplastic and 20% Pb (or MoS 2); the third layer - 0.1 mm of copper for adhesion of the bronze layer to steel (steel 08, 1 - 4 mm).

PTFE sponge is a lubricant. When heated in the place of friction, PTFE is squeezed out of the pores of the bronze due to the higher temperature coefficient of linear expansion and increases the amount of lubricant in the friction and heating zone. With strong heating, lead begins to melt (327 ° C), which leads to a decrease in the coefficient of friction.

Metal-fluoroplastic bearings can operate in a vacuum, in liquid non-lubricating media and in the presence of abrasive particles that are "sunk" in their soft component.

Minerals. Natural hard minerals (agate), artificial minerals (ruby, corundum) and sitalls (glass-crystalline materials) are used for miniature plain bearings - stone bearings. Their main advantage is a low and stable frictional moment. The frictional moment is low due to:

Small footprint;

Low adhesion of metal to mineral (low coefficient of friction);

The constancy of the frictional moment is ensured by the high wear resistance of the minerals, due to their high hardness.

1 The process of gradual accumulation of damage in a material under the action of cyclic loads, leading to a change in its properties, the formation of cracks, their development and destruction, is called tiredness. The ability to resist fatigue - endurance.

Cyclic durability- the number of cycles (or operating hours) that the material withstands until a fatigue crack of a certain length or fatigue failure at a given stress is formed. It characterizes the performance of the material under conditions of repetitive stress cycles between two limiting values ​​ max and min during the period T. When experimentally determining the fatigue resistance of a material, a sinusoidal cycle of voltage change is taken as the main one.

Cyclic durability is a physical or limited endurance limit. It characterizes the bearing capacity of the material, that is, the highest stress that it can withstand during a certain time of operation.

The soft component of the human body

First letter "p"

Second letter "l"

Third letter "o"

The last beech letter "ь"

Answer to the question "The soft component of the human body", 5 letters:
flesh

Alternative crossword questions for flesh

What does a hermit tame with asceticism?

The same as the body

Film starring Hollywood star Greta Garbo "... and the Devil"

Clothe in ... and blood

Abused body

Definition of flesh in dictionaries

Wikipedia Definition of a word in the Wikipedia dictionary
Flesh and blood. The whole person with body and soul can be designated by the flesh, opposing the flesh to the blood and, at the same time, the flesh is identified with the body. The Apostolic Creed affirms the dogma of the resurrection of the flesh after the Second Coming. Apostle...

Explanatory dictionary of the Russian language. D.N. Ushakov The meaning of the word in the dictionary Explanatory dictionary of the Russian language. D.N. Ushakov
flesh, pl. no, well. Body (lower. Obsolete and church.) Are not husband and wife one spirit and one flesh? Pushkin. Weak flesh. The same, As a source of sensuality, lust (church). Mortify the flesh. Humble your flesh. Male seed (obsolete and obl.). Dandruff (region) ....

Examples of the use of the word flesh in literature.

Everything must change from the moment when the Adjarians, blood from blood and flesh from the flesh of the villages that sent them, they will return to their native places as teachers and propagandists.

Under the influence of vibration-shock eye rays that pierce flesh and bones with electric needles, her image blurred and burst in an explosion of nitrogenous kinodim.

Brown clouds emanate from their scent glands and sweep through the ranks of the saints, eating flesh to the bone in gusts of nitrogenous vapor.

Pearl spasms received and passed, nitrogenous flesh formed amber evenings.

From a door of tarnished silver, a boy from a dead nitrogenous flesh.

In the process of welding, the sections of the parts to be joined, which are in the zone of the welded seam and around it, are subjected to intense temperature effects: at first they quickly heat up to the melting temperatures, and then cool down with almost the same intensity. Deformations and stresses during welding are an inevitable consequence of such processes.

With ultrafast heating, structural changes occur in any metal. They are caused by the fact that the constituent microstructures of any metal have different grain sizes.

With regard to unalloyed medium- and low-carbon steels (steels with a high carbon content, as you know, are poorly welded), at different temperatures, mainly the following structures can form in them:

1. Austenite- solid solution of carbon in α-iron. It is formed at heating temperatures above 723 0 С, and exists, depending on the percentage of carbon in the steel, up to temperatures of 1100-1350 0 С. The mobility of grains of the microstructure under such conditions is high, therefore austenitic steels are quite plastic and do not exhibit significant the level of residual stresses. Partially (up to 18-20%) austenite remains in the steel structure after final cooling. The austenite grain size is 0.27-0.8 microns.
2. Iron carbide / cementite... The structure has a diamond-shaped lattice and is characterized by high surface hardness. The grain sizes are in the range of 0.1-0.3 microns.
3. Ferrite- the low-temperature, softest component of the microstructure, formed during the relatively slow cooling of the metal, which occurs during execution. Ferrite grains are rounded in plan, 0.7-0.9 microns in size.
4. Perlite- a structure that forms during the cooling of the metal and is a mixture of ferrite and cementite. Depending on the cooling rate, pearlite can be grainy or lamellar. In the first case, the grains are elongated along the axis of the workpiece, in the second, they have a rounded shape. The average particle size of pearlite is in the range of 0.6-0.8 microns. At higher cooling rates, instead of pearlite, a thinner structural component appears, which is called troostite. The grain size of troostite does not exceed 0.2 µm.
5. Martensite- a non-equilibrium structural component that exists only in steel heated to temperatures above 750-900 0 С (with an increase in the percentage of carbon, the beginning of the martensitic transformation shifts to the region of lower temperatures). It is fixed in the composition of steel only during its accelerated cooling, for example, during quenching. Such martensite has a grain size of 0.2-2.0 microns.

Alloyed steels are characterized by an even more complex composition, in the microstructure of which carbides and nitrides of the components appear. In addition, the grain size is strongly influenced by the cooling rate of various parts of the parts, the composition of the atmosphere in which heating is performed, the diffusion rate of the material of the welding electrodes, etc.

Thus, the main reason for the occurrence of stresses in welded structures is sharply different grain sizes in the microstructure of steels.

Classification of stresses and strains

The main reason for the occurrence of welding stresses and deformations is the uneven properties of the parts to be joined. Distinguish between internal (residual) and surface stresses. The former are formed in welded parts when they are cooled. They cause warpage of structures, and with increased hardness parameters, they can lead to the appearance of internal ruptures in the metal. Such voltages are dangerous for the following reasons:

1. Cannot be detected by visual inspection.
2. They are not constant over time, sometimes they increase during the operation of the welded assembly.
3. Contribute to a decrease in operational resistance, up to the destruction of the welded seam.

The presence of surface stresses is easily detected by warping the elements of the welded structure, especially in thin-walled ones. Such stresses are easily corrected after welding. However, if such stresses exceed the ultimate strength of the metal, then cracks appear on the surface. For low-responsibility products, they can be welded, in other cases, the welding is considered defective. The likelihood of stress is reduced when welding metals with approximately similar physical and mechanical properties. Bulk welding stresses are considered more dangerous, since their sign and absolute value are difficult to assess by conventional methods.

The effect of stresses is the resulting deformations during welding. They can be elastic and plastic. Elastic deformations arise as a result of the action of surface stresses, when the linear and volumetric parameters of the metal change: they increase during the welding process and decrease when the weld zone is cooled. Plastic deformation is a consequence of irreversible changes in the shape of the product under the influence of internal stresses that have exceeded the ultimate strength of the metal.

An important characteristic of the quality of welding is the coefficient of non-uniformity of deformation. It is set by linear and angular changes in the original dimensions of the parts at different coordinates. Deformation unevenness is minimal when the workpieces to be welded are not fixed in any fixture. For example, in contact with a less heated vice, the thermal expansion of the element to be connected in this direction is impossible, therefore, it is there that increased residual stresses will be formed.

The level of deformations in the zone of the weld seam increases if sharply dissimilar metals are being welded. This is due to the difference in the physical characteristics of materials - coefficients of thermal expansion, thermal conductivity, heat capacity, elastic modulus, etc.

The performance of the welding unit, in which internal stresses remain, is determined by the conditions of its operation. For example, at low temperatures and dynamic loads, the fracture of the weld due to the stresses present there is more likely than under normal conditions.

Thus, after welding dissimilar metals, as well as parts with sharply different overall dimensions, the welded structure should be examined more carefully. When detecting angular or linear deformations, it is impossible to use the product without correcting defects.

Methods for eliminating stresses and deformations

There are enough ways to avoid welding defects due to deformations and stresses in the weld.

Minimizing the seam size is the simplest way to reduce the risk of knot failure. With a decrease in the width of the seam, the zone of action of stresses decreases, as well as the forces of buckling of the part caused by structural changes in it. When a positive effect is achieved by careful preparation of the edges: they are cut in the form of the letters V, U or X. With fillet welding, the same result can be achieved with the correct shape of the seam section: it should look like a parabolic triangle when the voltage drop is the smallest. It should be noted that the welding stresses can mutually balance each other, therefore, with a double-sided weld, one part of it is made with a concave parabolic triangle, and the opposite is a convex one.

With increasing seam length, the likelihood of welding stresses and deformations increases. Therefore, for unloading, an intermittent seam is practiced, when zones that have not been exposed to the thermal effect of a flame or a welding arc are left between its individual sections. If, according to the strength conditions, the execution of an intermittent seam is impossible, then compensation stiffeners are provided in the structure.

The level and likelihood of welding stresses and deformations in the transverse direction is sharply reduced when using electrodes with an increased diameter. In this case, the temperature difference over the cross section of the seam decreases. The same effect is obtained by a decrease in the number of welding passes: each subsequent one increases the level of welding stresses, which have not yet had time to decrease after the previous pass. For this purpose, double-sided (but of the same type!) Grooving is provided.

When welding parts with sharply different thicknesses, or a complex Z-shaped profile, the seam is provided along the axis of symmetry, when the distance to both edges is approximately the same. In this case, the metal on both sides of the symmetry axis cools down in approximately the same conditions.

To compensate for the resulting tensile-compression forces, the seams are performed in the reverse order. As a result, the stresses are mutually balanced. The reverse sequence is possible not only along the length, but also along the depth of the seam.

Structural elements form a special group of methods to reduce welding stresses and deformations: intermediate shims, water-cooled vices, etc. In the first case, metals with increased heat capacity are used, for example, copper. Copper pipes are also used in the construction of clamping devices, while the place of water supply must coincide with the place of the seam to be applied. When making long seams, additional clamps are effective, which prevent thermal deformation of the metal in the weld zone. Such clamps are removed only after complete cooling of the connected structure.

The cardinal method for relieving stresses and strains arising during welding is softening heat treatment of finished structures - their annealing.