Chops along or across the grain. How to cut meat? How to properly cut meat for various dishes

The mechanical properties of wood include: strength, hardness, rigidity, impact strength and others.

Strength - the ability of wood to resist destruction from mechanical forces, characterized by tensile strength. The strength of wood depends on the direction of the load, the type of wood, density, humidity, and the presence of defects.

Only bound moisture contained in the cell membranes has a significant effect on the strength of wood. As the amount of bound moisture increases, the strength of wood decreases (especially at a humidity of 20-25%). A further increase in humidity beyond the hygroscopic limit (30%) does not affect the strength of wood. Strength indicators can only be compared at the same wood moisture content. In addition to humidity, the mechanical properties of wood are also influenced by the duration of the load.

Vertical static loads are constant or slowly increasing. Dynamic loads, on the contrary, act for a short time. A load that destroys the structure of wood is called destructive. The strength bordering on destruction is called the tensile strength of wood; it is determined and measured by wood samples. The strength of wood is measured in Pa/cm2 (kgf per 1 cm2) of the cross section of the sample at the point of destruction, (Pa/cm2 (kg s/cm2).

The resistance of wood is determined both along the fibers and in the radial and tangential directions. There are main types of force actions: tension, compression, bending, shearing. Strength depends on the direction of the forces, the type of wood, the density of the wood, humidity and the presence of defects. The mechanical properties of wood are given in the tables.

Most often, wood works in compression, for example, posts and supports. Compression along the fibers acts in the radial and tangential directions (Fig. 1).

Tensile strength. The average tensile strength along the fibers for all rocks is 1300 kgf/cm2. The tensile strength along the grain is greatly influenced by the structure of the wood. Even a slight deviation from the correct arrangement of fibers causes a decrease in strength.

The tensile strength of wood across the grain is very low and on average is 1/20 of the tensile strength along the grain, that is, 65 kgf/cm2. Therefore, wood is almost never used in parts that work in tension across the grain. The tensile strength of wood across the grain is important when developing cutting modes and wood drying modes.

Compressive strength. A distinction is made between compression along and across the fibers. When compressed along the fibers, the deformation is expressed in a slight shortening of the sample. Compressive failure begins with longitudinal bending of individual fibers, which in wet samples of soft and viscous rocks manifests itself as crushing of the ends and bulging of the sides, and in dry samples and hard wood causes a shift of one part of the sample relative to another.

Average tensile strength when compressed along the fibers for all rocks is 500 kgf/cm2.

The compressive strength of wood across the grain is approximately 8 times lower than along the grain. When compressed across the fibers, it is not always possible to accurately determine the moment of wood destruction and determine the magnitude of the destruction load.

Wood is tested for compression across the grain in radial And tangential directions. In deciduous species with wide core rays (oak, beech, hornbeam), the strength under radial compression is one and a half times higher than under tangential compression; in conifers, on the contrary, the strength is higher under tangential compression.

Rice. 2. Testing the mechanical properties of wood for bending.

Ultimate strength under static bending. When bending, especially under concentrated loads, the upper layers of wood experience compressive stress, and the lower layers experience tension along the fibers. Approximately in the middle of the height of the element there is a plane in which there is neither compressive nor tensile stress. This plane is called neutral; maximum tangential stresses arise in it. The tensile strength in compression is less than in tension, so failure begins in the compressed zone. Visible destruction begins in the stretched zone and is expressed in the rupture of the outermost fibers. The tensile strength of wood depends on the species and humidity. On average, for all rocks, the bending strength is 1000 kgf/cm2, that is, 2 times the compressive strength along the fibers.

Shear strength of wood. External forces that cause movement of one part of a part relative to another are called shear. There are three cases of shear: shearing along the grain, across the grain, and cutting.

Shear strength along the grain is 1/5 of the compressive strength along the fibers. In hardwoods with wide core rays (beech, oak, hornbeam), the chipping strength along the tangential plane is 10-30% higher than along the radial plane.

Tensile strength when shearing across the fibers approximately two times less than the tensile strength when shearing along the fibers. The strength of wood when cut across the grain is four times higher than the strength when chipped.

Hardness- this is the property of wood to resist the introduction of a body of a certain shape. The hardness of the end surface is higher than the hardness of the side surface (tangential and radial) by 30% for hardwoods and 40% for conifers. According to the degree of hardness, all wood species can be divided into three groups: 1) soft - end hardness 40 MPa or less (pine, spruce, cedar, fir, juniper, poplar, linden, aspen, alder, chestnut); 2) hard - end hardness 40.1-80 MPa (larch, Siberian birch, beech, oak, elm, elm, elm, plane tree, rowan, maple, hazel, walnut, persimmon, apple tree, ash); 3) very hard - end hardness more than 80 MPa (white acacia, iron birch, hornbeam, dogwood, boxwood, pistachios, yew).

The hardness of wood is of significant importance when processing it with cutting tools: milling, sawing, peeling, as well as in cases where it is subjected to abrasion when constructing floors, stairs and railings.

Wood hardness

Impact strength characterizes the ability of wood to absorb work upon impact without destruction and is determined during bending tests. The impact strength of hardwood wood is on average 2 times greater than that of softwood wood. Impact hardness is determined by dropping a steel ball with a diameter of 25 mm from a height of 0.5 m onto the surface of the sample, the greater the value of which, the lower the hardness of the wood.

Wear resistance - the ability of wood to resist wear, i.e. gradual destruction of its surface zones during friction. Tests on the wear resistance of wood have shown that wear from the side surfaces is significantly greater than from the end cut surface. As the density and hardness of the wood increased, wear decreased. Wet wood wears more than dry wood.

Ability of wood to hold metal fasteners: nails, screws, staples, crutches, etc. are its important properties. When driving a nail into wood, elastic deformations occur, which provide sufficient friction force to prevent the nail from being pulled out. The force required to pull out a nail driven into the end of the sample is less than the force applied to a nail driven across the grain. As the density of wood increases, the resistance of wood to pulling out a nail or screw increases. The effort required to pull out screws (all other things being equal) is greater than for pulling out nails, since in this case the resistance of the fibers to cutting and tearing is added to friction.

Basic technical properties of various wood species

Standard resistance of pure pine and spruce wood

Average wood resistance to nail pullout

The force required to pull out a nail driven into the end is 10-15% less than the force applied to a nail driven across the grain.

Wood's ability to bend allows you to bend it. The ability to bend is higher in ring-vascular species - oak, ash, etc., and among scattered-vascular species - beech; Coniferous species have less bending ability. Wood that is in a heated and wet state is subjected to bending. This increases the flexibility of the wood and allows, due to the formation of frozen deformations during subsequent cooling and drying under load, a new shape of the part to be fixed.

Splitting wood is of practical importance, since some assortments are prepared by splitting (rivet, rim, knitting needles, shingles). The resistance to splitting along the radial plane of hardwood wood is less than along the tangential plane. This is explained by the influence of the medullary rays (in oak, beech, hornbeam). In conifers, on the contrary, splitting is less along the tangential plane than along the radial plane.

Deformability. Under short-term loads, predominantly elastic deformations occur in wood, which disappear after the load. Up to a certain limit, the relationship between stress and strain is close to linear (Hooke's law). The main indicator of deformability is the coefficient of proportionality - the elastic modulus.

Modulus of elasticity along the fibers E = 12-16 GPa, which is 20 times more than across the fibers. The higher the elastic modulus, the stiffer the wood.

With an increase in the content of bound water and the temperature of the wood, its hardness decreases. In loaded wood, when drying or cooling, part of the elastic deformations is converted into “frozen” residual deformations. They disappear when heated or moistened.

Since wood consists mainly of polymers with long, flexible chain molecules, its deformability depends on the duration of exposure to loads. The mechanical properties of wood, like other polymers, are studied on the basis of the general science of rheology. This science examines the general laws of deformation of materials under the influence of load, taking into account the time factor.

Almost all cookbooks contain the recommendation to “cut the meat across the grain.” We suggest you figure out what this really means, how to do it correctly, and whether this is really important for obtaining a positive result.

Many of us have encountered a situation where a steak made from perfect meat, cooked according to all the rules of the recipe, turns out to be tough and rubbery. It turns out that the key to success lies not only in the correct choice of meat and the technology of its preparation, but also in its cutting, or more precisely in the angle of inclination at which you cut it.

If you carefully examine any piece of meat, you will notice that its structure is similar to wood and has the same clearly defined fibers. When it comes to sirloin, subscapular or loin of beef, there is not much to worry about, the structure of the muscle tissue in such cuts is thin and tender in itself, and even the wrong cut is unlikely to greatly affect the softness and tenderness of the steak. But if you are dealing with flank steak, where the muscle fibers are dense and strong, it is worth taking the advice of cutting the meat correctly.

It's all about the fibers

What we call fibers is the direction in which the muscle tissue is located. And it is the correct definition of this direction that plays a decisive role for the result. The juiciness and softness of the meat depends on the direction in which you cut the meat from the fibers.

Case Study

In fact, this statement can be easily verified in practice if you separate a small amount of muscle tissue from a steak and try to tear it, stretching it lengthwise. It will be quite difficult. But it’s quite easy to separate small fibers from each other.

How to cut?

Thus, before you put a piece of steak into your mouth, your goal is to shorten these same fibers as much as possible. After all, if you cut a steak parallel to the muscle tissue, you will get long, tough fibers that will be difficult to chew. And if you cut it across, you will get small pieces of muscle tissue, the fibers of which are ready to fall apart without any extra effort on your part.

Mathematical justification

For the skeptics, we can even prove mathematically the importance of following the above rules.

For convenience, we propose to introduce the following definitions:

W is the distance the knife moves between cuts (that is, the width of the piece)

M - length of meat fibers in each piece

θ- angle between the knife blade and meat fibers

M = w/sin(θ) If our goal is to reduce the fiber length (m), we need to increase the value of sin(θ).

With a piece width of 1.5 cm and a knife angle towards the fibers of 90 degrees, the value of sin (θ) is equal to one, and the length of the fibers coincides with the width of the piece.

If we reduce the angle to 45 degrees, with the same width of the piece, we get a fiber length equal to 1.76 cm (1.5^ (1/2). And this is an increase of 50%! And to bring the situation to the point of absurdity, imagine: that we need to cut the meat parallel to the grain. In this case, sin (θ) will be equal to zero, and, according to the inviolable laws of mathematics, the length of the grain of your steak will extend straight to infinity, which will certainly make it difficult to eat.

Question No. 24. Tensile strength of wood along and across the grain. Shape and dimensions of samples. What explains the difference in tensile strength of wood along and across the grain?

Determine the strength of a sample of pine wood in compression along the fibers and bring it to a normalized moisture content W = 12%, if the sample dimensions are standard, the maximum load is 7800 N, and the humidity at the time of testing is 32%. Correction factor K=2.25.

To determine the tensile strength of wood along the grain, samples of rather complex shapes with massive heads, which are clamped in wedge-shaped grips of the machine, and a thin working part are used. The shape, dimensions of the sample and the diagram of its fastening, see the figure:

With this shape of the sample, the possibility of its destruction at the attachment points due to compression across the fibers and chipping along the fibers is prevented. The transition from the heads to the working part of the sample is made smooth to avoid stress concentration. Sample blanks are prepared by pinching (rather than sawing) to avoid cutting the fibers. The working part of the sample should capture as many annual layers as possible, so its wide edge coincides with the radial direction. It is allowed to produce samples with glued heads.

Before testing, the thickness a and width b of the working part of the samples are measured with an error of up to 0.1 mm and steel plugs with a diameter of 9.9 mm are inserted into the holes of the heads. The length of the plugs is 3 or 2 mm (for soft and hard wood, respectively) less than the thickness of the head. The plugs prevent excessive compression of the heads during testing.

The tensile strength of wood along the fibers depends relatively little on the moisture content of the wood, but drops sharply at the slightest deviation of the fibers from the direction of the longitudinal axis of the sample. On average, for all rocks the tensile strength along the fibers is 130 MPa. Despite such high strength, wood in structures and products rarely works in tension along the fibers due to the difficulty of preventing the destruction of parts at the points of fastening (under the influence of compressive and shearing loads).

The current standard for tensile testing of wood across the grain recommends a specimen whose shape and dimensions are shown in the figure below. This specimen is shaped like a tensile test specimen along the grain. However, in this case, the samples are mounted in screw grips on the flat side so that the compressive forces are directed along the fibers.

Difficulties that arise when making a sample of relatively large length (for a plane across the fibers) can be reduced by using glued samples. In glued samples, the central section of the wood under study must have a length of at least 90 mm and include a flat working area, curved transitions and a small part of the length of the heads.

To determine the tensile strength across the fibers in the radial and tangential directions, the sample is made in such a way that the annual layers on its flat side are directed respectively across (as shown in the figure) or along the length of its working part.

There is still no comprehensive data on the comparative tensile strength of wood across the grain for different species, established using a standard sample shape, however, experiments conducted earlier with samples whose shape corresponded to the previously valid standard show that the strength of wood in the radial direction is greater than in tangential, for conifers by 10-50%, for deciduous trees by 20-70%. On average, the tensile strength across the grain for all rocks studied is approximately 1/20 of the tensile strength along the grain.

When designing wood products, they try to prevent tensile loads directed across the fibers. Indicators of the strength of wood under a given type of effort are necessary for the development of cutting and drying modes for wood. It is these values ​​that characterize the maximum value of drying stresses, the achievement of which causes cracking of the material. When calculating safe wood drying modes, the dependence of strength limits on humidity and temperature, as well as the duration of load application (loading speed), is taken into account.

The conditional compressive strength across the grain for all rocks is on average approximately 10 times less than the compressive strength along the grain. This difference is explained by the fact that when compressed across the fibers, additional resistance of the wood fibers arises, while during longitudinal compression the resistance is limited by the elastic forces of the annual layers of wood. In other words, the deformability of wood when compressed across the grain is higher than when compressed along the grain.

Determine the strength of a sample of pine wood in compression along the fibers and bring it to a normalized moisture content W = 12%, if the sample dimensions are standard, the maximum load is 7800 N, and the humidity at the time of testing is 32%. Correction factor K=2.25.

The strength of a sample made of pine wood is determined by the formulas:

w = Pmax/a*b = 7800/20*20 = 19.5 MPa

V 12 = V 30 * K = 19.5 * 2.25 = 39 MPa

Question No. 38. Changes in the properties of wood under the influence of physical and chemical factors: drying; positive and negative temperatures; humidity; ionizing radiation; acids, alkalis and gases; sea ​​and river water.

Construct a graph of the effect of humidity on the strength of beech wood during compression along the grain, if 0% = 63.0 MPa; at 12% = 55.5 MPa; at 18% = 44.8 MPa; at 70% = 26.0 MPa.

During the drying process, raw wood is exposed to steam, heated dry or humid air, high-frequency currents and other factors, ultimately leading to a decrease in the content of free and bound water. That's right, under appropriate conditions, chamber drying of wood produces material that is quite equivalent to that obtained as a result of atmospheric drying. But if you dry wood in kilns too quickly and at high temperatures, this can not only lead to cracking and significant residual stresses, but also affect the mechanical properties of the wood.

According to TsNIIMOD, high-temperature drying leads to a decrease in the mechanical properties of wood. Strength decreases to a lesser extent during compression along the fibers and static bending, to a greater extent during tangential chipping, and the impact strength of wood decreases very significantly.

The drying time is sharply reduced when using microwave electromagnetic oscillations. However, the degree of specific influence of this factor on the properties of wood has not yet been established.

An increase in temperature causes a decrease in the strength and other physical and mechanical properties of wood. With relatively short-term exposure to temperatures up to 100 o C, these changes are mainly reversible, i.e. they disappear when the wood returns to its initial temperature.

Data obtained by TsNIIMOD show that compressive strength along and across the fibers decreases both with increasing temperature and increasing humidity of wood. The simultaneous impact of both factors causes a greater reduction in strength compared to the total effect of their isolated impact. The effect of humidity is observed up to the limit of cell wall saturation; a further increase in humidity has practically no effect on strength, although a number of researchers have noted its decrease (by 10-15%) in this range of humidity changes.

With sufficiently long exposure to elevated temperatures (more than 50 o C), irreversible residual changes occur in the wood, which depend not only on the temperature level, but also on humidity.

The impact strength of wood with low humidity decreases with increasing temperature, and at high humidity, on the contrary, it increases (wood was tested in a heated state).

Exposure to high temperatures causes wood to become brittle.

The nature of the influence of positive temperatures is the same for absolutely dry and wet wood. At the same time, at negative temperatures, the strength of absolutely dry wood gradually increases, and that of wet wood increases sharply with a decrease in temperature to - 25 o C ... - 30 o C, after which the increase in strength slows down. At these temperatures, so many ice inclusions are formed that they provide sufficient stability to the cell walls. The elastic modulus of wood increases when it is frozen.

Gamma irradiation, according to A.S. Freidin, has the least effect on the compressive resistance of wood. The shear strength is significantly reduced and the resistance to static bending drops even more. For the last two types of tests on pine wood, a sharp decrease in strength (by 20-24%) is observed already at a dose of 50 Mrad. With an irradiation dose of 100 Mrad, the strength is reduced by half. The strength after an irradiation dose of 500 Mrad in static bending is slightly more than 10%, and in compression along the fibers it decreases by 30%. Irradiation has the greatest effect on the impact strength of wood. In pine wood, after irradiation with a dose of 50 Mrad, the impact strength decreased by more than half. Radiation sterilization of wood (about 1 Mrad) practically does not reduce its mechanical properties.

Exposure to room-dry wood in small samples of sulfuric, hydrochloric and nitric acid with a concentration of 10% at a temperature of 15-20 o C leads to a decrease in the severity of compression along the fibers and static bending, impact strength and hardness by an average of 48% for the larch core and pine and 53-54% for spruce (ripe wood), beech and birch.

When wood was exposed to alkalis for four weeks, the following data were obtained: a 2% ammonia solution had almost no effect on the static bending strength of larch, pine, and spruce, but the strength of oak and beech decreased by 34%, and linden by almost two ;10% ammonia solution reduced the strength of larch by 8%, pine and spruce by 23%, and hardwood by almost three times. Caustic soda has a stronger effect.

Thus, the strength of deciduous wood is reduced under the influence of acids and alkalis to a much greater extent than coniferous wood.

Gases SO 2, SO 3, NO, NO 2 with prolonged exposure to wood change color and gradually destroy it. When wood is moistened, destruction occurs more intensely. Resinousness reduces the harmful effects of gases, and blueness promotes damage.

Tests of driftwood from pine, spruce, birch and aspen logs showed that after being in river water for 10-30 years, the strength of the wood remained virtually unchanged. However, a longer stay in water causes a decrease in the strength of the outer layers of wood (10-15 mm thick). At the same time, in deeper layers, the strength of the wood turned out to be no lower than the norms allowed for healthy wood. Being in water for several hundred years greatly changes the wood. Depending on the time spent under water, the color of oak wood changes from light brown to coal black due to the combination of tannins with iron salts. The wood of the “stained” oak thus formed, plastic in a water-saturated state, becomes brittle after drying, its shrinkage is 1.5 times greater than that of ordinary wood; prone to cracking when dried; compressive strength, static bending and hardness are reduced by approximately 1.5 times, and impact strength by 2-2.5 times. It is impossible to determine exactly how the properties of wood change due to exposure to water, because the properties of wood before flooding are unknown.

After a relatively short time, sea water has a noticeable effect on the strength and toughness of wood.

To establish the possibility of using driftwood, it is tested and the degree of deviation of the obtained data from the reference data is determined.

Construct a graph of the effect of humidity on the strength of beech wood during compression along the grain, if y 0% = 63.0 MPa; 12% = 55.5 MPa; 18% = 44.8 MPa; 70% = 26.0 MPa.

In places of notches or connections of wooden parts with metal ones (under shoes, bolts, etc.), the strength of the wood when compressed across the fibers is of significant practical importance. A classic example of the work of wood in compression across the grain are also railway sleepers (places under the rails). There are three cases of wood compression across the grain: 1. The load is distributed over the entire surface of the compressed part.

2. The load is applied over part of the length, but across the entire width of the part. 3. The load is applied to parts of the length and width of the part (Fig. 54). All these cases occur in practice: the first case - when pressing wood, the second - when using sleepers under rails, the third - when using wood under the heads of metal fasteners. When compressed across the fibers of wood of different species, two types of deformation are observed: single-phase, as with compression along the fibers, and three-phase, characterized by a more complex diagram (see Fig. 54).

Table 35. Compressive strength of wood along the grain.

Rice. 54. Cases of compression across the fibers (below) and diagrams of compression of wood across the fibers (above): a - with three-phase; b - with single-phase deformation; 1 - compression over the entire surface; 2 - compression over part of the length; 3 - compression on part of the length and width.

During single-phase deformation, the diagram clearly shows an approximately straight section, which continues almost until the maximum load is reached, at which the wood sample is destroyed. During three-phase deformation, the process of wood deformation during compression across the fibers goes through three phases: the first phase is characterized on the diagram by an initial, approximately straight section, showing that at this stage of deformation the wood conditionally obeys Hooke’s law, as in single-phase deformation; at the end of this phase the conditional limit of proportionality is reached; the second phase is characterized on the diagram by an almost horizontal or slightly inclined curved section; the transition from the first phase to the second is more or less abrupt; the third phase is characterized on the diagram by a straight section with a steep rise; the transition from the second phase to the third is gradual in most cases.

According to the nature of deformation during radial and tangential compression, rocks can be divided into two groups: the first group includes coniferous and ring-vascular deciduous species (with the exception of oak), and the second group includes diffuse-vascular deciduous species. Coniferous wood (pine, spruce) and ring-vascular hardwood (ash, elm) under radial compression gives a diagram characteristic of three-phase deformation, and under tangential compression - a diagram of single-phase deformation.

The noted nature of deformation of wood of the named species can be explained as follows. During radial compression, the deformation of the first phase occurs mainly due to compression of the early zone of the annual layers, which is mechanically weak; the first phase continues until the walls of the elements of the early zone lose stability and begin to collapse. With the loss of stability of these elements, the second phase begins, when deformation occurs mainly as a result of collapse of the elements of the early zone; this occurs at an almost constant or slightly increasing load. As the elements of the late zone of annual layers are involved in the deformation, the second phase smoothly passes into the third. The third phase occurs mainly due to compression of the elements of the late zone, consisting mainly of mechanical fibers, which can only wrinkle under heavy loads.

During tangential compression, deformation occurs from the very beginning due to the elements of both zones of the annual layer, and the nature of the deformation, naturally, is determined by the elements of the late zone. At the end of deformation, destruction of the sample occurs, which is more clearly expressed in coniferous wood: samples usually bulge towards the convexity of the annual layers, which, during tangential bending, behave like curved beams during longitudinal bending.

Among ring-vascular deciduous species, oak does not obey the noted patterns, the wood of which, under radial compression, is deformed according to a single-phase type, and under tangential compression it tends to switch to three-phase deformation. This is explained by the fact that during radial compression, wide core rays have a strong influence on the nature of deformation. During tangential compression, the tendency to transition to three-phase deformation is explained by the radial grouping of small vessels in the late zone.

The wood of diffusely vascular deciduous species (birch, aspen, beech) showed three-phase deformation during both radial and tangential compression, which, apparently, should be explained by the absence of a noticeable difference between the early and late zones of the annual layers. Hornbeam wood exhibits a transitional form of deformation (from three-phase to single-phase); Obviously, in this case the influence of falsely wide core rays is felt.

The beginning of wood destruction can be observed only during single-phase deformation; during three-phase deformation, wood can be compacted to a quarter of the initial height without visible signs of destruction. For this reason, when testing compression across the fibers, they are limited to determining the stress at the limit of proportionality according to the compression diagram, without bringing the sample to failure.

Wood is tested in two ways: by compression over the entire surface of the sample and by compression over part of the length, but across the entire width (crushing). For compression tests across the fibers, a sample is made of the same shape and size as for compression along the fibers; the growth layers at the ends in this sample should be parallel to one pair of opposite faces and perpendicular to the other pair. The sample is placed on the supporting part of the machine with its side surface and is subjected to a stepwise load along the entire upper surface with an average speed of 100 ± 20 kg/min. The deformation of soft wood is measured with an indicator with an accuracy of 0.005 mm every 20 kg of load and hard wood - after 40 kg; the test continues until the proportional limit is clearly exceeded. Based on paired readings (load-deformation), a compression diagram is drawn, on which the load at the proportionality limit is determined, with an accuracy of 5 kg, as the ordinate of the transition point from a straight section of the diagram to a clearly curved one. The conditional compressive strength across the fibers is calculated by dividing the load found using the specified method at the limit of proportionality by the compression area (the product of the width of the sample and its length).

For crushing tests, a sample in the form of a square block of 20X20 mm, 60 mm long is used. The load on such a sample is transmitted across its entire width through a steel prism 2 cm wide, placed in the middle of the sample perpendicular to the length; The prism ribs adjacent to the sample have roundings with a radius of 2 mm. Otherwise, the procedure and test conditions are the same as in the first method, but the conditional tensile strength is calculated by dividing the load at the proportionality limit by the compression area equal to 1.8 a, where a is the width of the sample, 1.8 is the average width of the pressure surface prisms in centimeters.

The conditional tensile strength in crushing across the fibers is 20-25% higher than in compression; this is explained by the additional resistance from bending of the fibers at the ribs of the prism. In the third case of compression across the fibers (see Fig. 54), the values ​​of the conditional tensile strength are slightly higher than those obtained in the second case as a result of additional resistance to shearing across the grain at the die ribs running parallel to the wood fibers.

Table 36. Conditional tensile strength when crushing across the fibers.

Wood of species with wide or very numerous rays (oak, beech, maple, partly birch) is characterized by a higher nominal tensile strength under radial crushing (about 1.5 times); for other hardwoods (with narrow beams), the indicators of the conditional crushing strength in both directions are practically the same or differ little.

For coniferous wood, on the contrary, the conditional tensile strength for tangential compression is 1.5 times higher than for radial compression due to the sharp heterogeneity in the structure of the annual layers; with radial compression, it is mainly the weaker, early wood that is deformed, and with tangential compression, the load is also taken up by the late wood from the very beginning. Compared to the compressive strength along the grain, the nominal compressive strength across the grain averages about 1/8 (from 1/6 for hardwood to 1/10 for softwood and softwood).

Master class from an experienced butcher

So, you killed a bull. Not in the sense of being drunk, but competently, according to all the rules, and they butchered the carcass. You don't need to eat it right away. The carcass should hang for at least a day, all the blood should flow out. Or better yet, five days. Even fresh meat from the best parts of the carcass must mature to become softer and tastier. Fermentation processes take place inside, which take time.

If you bought fresh meat at the market, it needs to be kept for 5-6 days at a temperature of about 1 degree in the coldest part of the refrigerator, but not frozen. Stores and restaurants have special aging cabinets for this purpose. In them, the meat can reach perfect condition for 3 months.

As for the meat that you buy in stores, Evgeniy recommends taking the one that will soon expire. Then it will be as ripe and tasty as possible, but at the same time completely safe.

Muscles are cut across the fibers to make chewing easier

The meat you are going to fry should be at room temperature.

Then it will warm up faster in the frying pan.

The degree of frying depends not only on the strength of the fire and the frying time, but also on the thickness of the piece. If you want it with blood, cut it thicker, two and a half centimeters. If you like it well done, you need a thinner piece.

Trim all veins and excess fat in advance. Firstly, it will be easier to cut the piece into steaks. Secondly, then you won’t have to cut the cores from each piece separately.

Try to cut evenly so that the piece is the same thickness over the entire area. Otherwise, you will have blood on one side and well-done on the other.

To prevent large steaks from bending, small cuts 2-3 mm deep can be made along the edges.

More clearly in the video.

What to do next is up to you. You can buy meat anywhere in the primebeef.ru network and cook it yourself. There are recipes. Can you go to Primebeef Bar at the Danilovsky market and ask to fry any piece you choose there. By the way, on December 10, a second butcher shop and Primebeef Bar will open at the Usachevsky market.

Bon appetit and more good meat! And if you missed the master class on removing corks with a knife, it's still .