(strength, elasticity, plasticity, viscosity), as well as other properties, are the initial data in the design and creation of various machines, mechanisms and structures.
Methods for determining the mechanical properties of metals are divided into the following groups:
· static, when the load increases slowly and smoothly (tensile, compression, bending, torsion, hardness tests);
· dynamic, when the load increases at high speed (impact bending tests);
· cyclic, when the load changes many times (fatigue test);
· technological - to assess the behavior of metal during pressure treatment (bending, bending, extrusion tests).
Tensile tests(GOST 1497-84) are carried out on standard samples of round or rectangular cross-section. When stretched under the action of a gradually increasing load, the sample is deformed until it breaks. During testing of the sample, a tensile diagram is taken (Fig. 1.36, A), fixing the relationship between the force P acting on the sample and the deformation Δl caused by it (Δl is the absolute elongation).
Rice. 1.36. Tensile Diagram of Low Carbon Steel ( A) and the relationship between stress and elongation ( b)
Viscosity (internal friction) is the ability of a metal to absorb the energy of external forces during plastic deformation and fracture (determined by the magnitude of the tangential force applied per unit area of the metal layer subject to shear).
Plastic— the ability of solids to deform irreversibly under the influence of external forces.
The tensile test determines:
· σ in - strength limit, MN/m 2 (kg/mm 2):
0 is the initial cross-sectional area of the sample;· σ pts — proportionality limit, MN/m 2 (kg/mm 2):
Where P pc - load corresponding to the proportionality limit;
· σ pr - elastic limit, MN/m 2 (kg/mm 2):
Where R pr - load corresponding to the elastic limit (at σ pr the residual deformation corresponds to 0.05-0.005% of the initial length);
· σ T- yield limit, MN/m 2 (kg/mm 2):
Where R t is the load corresponding to the yield point, N;
· δ—relative elongation, %:
Where l 0—specimen length before rupture, m; l 1—sample length after rupture, m;
· ψ — relative narrowing, %:
Where F 0—sectional area before rupture, m2; F- cross-sectional area after rupture, m2.
Hardness tests
Hardness- this is the resistance of a material to the penetration of another, more solid body into it. Of all types of mechanical testing, hardness determination is the most common.
Brinell tests(GOST 9012-83) are carried out by pressing a steel ball into the metal. As a result, a spherical imprint is formed on the metal surface (Fig. 1.37, A).
Brinell hardness is determined by the formula:
— ball diameter, m; d— imprint diameter, m.The harder the metal, the smaller the print area.
The diameter of the ball and the load are set depending on the metal being tested, its hardness and thickness. When testing steel and cast iron, choose D= 10 mm and P= 30 kN (3000 kgf), when testing copper and its alloys D= 10 mm and P= 10 kN (1000 kgf), and when testing very soft metals (aluminum, babbitts, etc.) D= 10 mm and P= 2.5 kN (250 kgf). When testing samples with a thickness of less than 6 mm, balls with a smaller diameter are selected - 5 and 2.5 mm. In practice, they use a table for converting the area of the imprint into the hardness number.
Rockwell tests(GOST 9013-83). They are carried out by pressing a diamond cone (α = 120°) or a steel ball ( D= 1.588 mm or 1/16", Fig. 1.37, b). The Rockwell instrument has three scales - B, C and A. The diamond cone is used to test hard materials (scales C and A), and the ball is used to test soft materials (scale B). The cone and ball are pressed in with two successive loads: preliminary R 0 and total R:
R = R 0 + R 1 ,
0 = 100 N (10 kgf). The main load is 900 N (90 kgf) for scale B; 1400 N (140 kgf) for scale C and 500 N (50 kgf) for scale A.Rice. 1.37. Hardness determination scheme: A- according to Brinell; b- according to Rockwell; V- according to Vickers
Rockwell hardness is measured in arbitrary units. The unit of hardness is taken to be the value that corresponds to the axial movement of the tip over a distance of 0.002 mm.
Rockwell hardness is calculated as follows:
HR = 100 - e(scales A and C); HR = 130 - e(scale B).
Size e determined by the formula:
Where h— depth of penetration of the tip into the metal under the influence of the total load R (R =R 0 + R 1); h 0 - tip penetration depth under preload R 0 .
Depending on the scale, Rockwell hardness is designated HRB, HRC, HRA.
Vickers tests(GOST 2999-83). The method is based on pressing a tetrahedral diamond pyramid (α = 136°) into the test surface (ground or even polished) (Fig. 1.37, V). The method is used to determine the hardness of thin parts and thin surface layers with high hardness.
Vickers hardness:
— arithmetic mean of two imprint diagonals measured after removing the load, m.The Vickers hardness number is determined using special tables along the diagonal of the print d. When measuring hardness, a load from 10 to 500 N is used.
Microhardness(GOST 9450-84). The principle of determining microhardness is the same as that of Vickers, according to the relationship:
The method is used to determine the microhardness of small-sized products and individual components of alloys. The device for measuring microhardness is a diamond pyramid indentation mechanism and a metallographic microscope. Samples for measurements must be prepared as carefully as microsections.
Impact test
For impact testing, special samples with a notch are made, which are then destroyed on a pendulum impact driver (Fig. 1.39). The total energy reserve of the pendulum will be spent on the destruction of the sample and on raising the pendulum after its destruction. Therefore, if we subtract from the total energy reserve of the pendulum the part that is spent on lifting (takeoff) after the destruction of the sample, we obtain the work of destruction of the sample:
K = P(h 1 - h 2)
K = Рl(cos β - cos α), J (kg m),
de P— mass of the pendulum, N (kg); h 1 — height of rise of the center of mass of the pendulum before impact, m; h 2 — take-off height of the pendulum after impact, m; l— pendulum length, m; α, β are the angles of elevation of the pendulum, respectively, before and after the destruction of the sample.
Rice. 1.39. Impact test: 1 - pendulum; 2 - pendulum knife; 3 - supports
Impact strength, i.e., the work expended on the destruction of the sample and related to the cross-section of the sample at the site of the notch, is determined by the formula:
MJ/m 2 (kg m/cm 2),
Where F- cross-sectional area at the site of the sample cut, m2 (cm2).
For determining KS use special tables in which the magnitude of the impact work is determined for each angle β K. Wherein F= 0.8 · 10 -4 m 2.
To indicate impact strength, a third letter is added, indicating the type of cut on the sample: U, V, T. Record KCU means the impact strength of a sample with U-shaped cut, KCV- With V-shaped cut, and KST- with a crack (Fig. 1.40).
Rice. 1.40. Types of cuts on samples for impact strength testing:
A — U-shaped cut ( KCU); b — V-shaped cut ( KCV); V- cut with a crack ( KST)
Fatigue test(GOST 2860-84). The destruction of metal under the influence of repeated or alternating stresses is called metal fatigue. When a metal fractures due to fatigue in air, the fracture consists of two zones: the first zone has a smooth ground-in surface (fatigue zone), the second is a fracture zone; in brittle metals it has a coarse-crystalline structure, and in viscous metals it has a fibrous structure.
When testing for fatigue, the limit of fatigue (endurance) is determined, i.e., the greatest stress that a metal (specimen) can withstand without destruction for a given number of cycles. The most common fatigue test method is the rotational bending test (Figure 1.41).
Rice. 1.41. Rotational bending test setup:
1
- sample; bending moment
The following main types of technological tests (samples) are used.
Bend test(Fig. 1.42) in cold and hot states - to determine the ability of the metal to withstand a given bend; sample dimensions - length l = 5A+ 150 mm, width b = 2A(but not less than 10 mm), where A- thickness of the material.
Rice. 1.42. Technological bending test: A— sample before testing; b- bend to a certain angle; V- bend until the sides are parallel; G- bend until the sides touch
Bend test involves assessing the ability of a metal to withstand repeated bending and is used for wire and rods with a diameter of 0.8–7 mm from strip and sheet material up to 55 mm thick. The samples are bent alternately to the right and to the left by 90° at a uniform speed of about 60 bends per minute until the sample is destroyed.
Extrusion test(Fig. 1.43) - to determine the ability of the metal to cold stamping and drawing thin sheet material. It consists of pressing a sheet of material with a punch, sandwiched between a matrix and a clamp. A characteristic of the plasticity of the metal is the depth of extrusion of the hole, which corresponds to the appearance of the first crack.
Rice. 1.43. Extrusion test: 1 - leaf; h- a measure of the ability of a material to draw
Test for winding wire with diameter d ≤ 6 mm. The test consists of winding 5-6 tightly fitting turns along a helical line onto a cylinder of a given diameter. Performed only in a cold state. The wire after coiling should not be damaged.
Spark test used when it is necessary to determine the steel grade in the absence of special equipment and markings.
Parts of machines and mechanisms operate under different loads: some parts experience constant loads in one direction, others experience impacts, and others experience loads that change in magnitude and direction. Some machine parts are subject to stress at high or low temperatures. Therefore, various test methods have been developed to determine the mechanical properties of metals. There are static and dynamic tests.
Static are tests in which the material being tested is subjected to a constant or slowly increasing load.
Dynamic are tests in which a material is subjected to impact loads.
The most common tests are hardness, static tensile, and impact tests. In addition, fatigue, creep and wear tests are sometimes performed, which provide a more complete understanding of the properties of metals.
Tensile tests. Static tensile testing is a common method of mechanical testing of metals. During these tests, a uniform stress state is created across the cross-section of the sample; the material is under the influence of normal and tangential stresses.
For static tests, round samples are usually used. 1 (Fig. 2.5) or flat 2 (leaf). The samples have a working part and heads designed to be secured in the grips of a tensile testing machine.
For cylindrical samples, the ratio of the calculated initial length / 0 to the initial diameter (/ 0 /^/ 0) is called sample multiplicity, on which its final relative elongation depends. In practice, samples with a multiplicity of 2.5 are used; 5 and 10. The most common pattern is a multiple of 5.
The design length /0 is taken to be slightly less than the working length /. Sample sizes are standardized. Working part diameter
Rice. 2.5.1 - round sample; 2 - flat sample; /1 - length of the working part; /о - initial design length
normal round sample 20 mm. Samples of other diameters are called proportional.
The tensile force creates stress in the test specimen and causes it to elongate. The moment the stress exceeds the strength of the sample, it will rupture.
Before testing, the sample is secured in a vertical position in the grips of the testing machine. In Fig. Figure 2.6 shows a diagram of a testing machine, the main elements of which are: a driving loading mechanism that ensures smooth loading of the sample until it breaks; a force measuring device for measuring the tensile strength of the sample; mechanism for automatic recording of the stretch diagram.
Rice. 2.6.1 - base; 2 - screw; 3 - lower grip (active); 4 - sample; 5 - upper grip (passive); 6 - force measuring sensor; 7 - control panel with electric drive equipment; 8 - load indicator; 9 - control handle; 10 - diagram mechanism; 11 - cable
During testing, the diagram mechanism continuously records the so-called primary (machine) tensile diagram (Fig. 2.7) in load coordinates R; D/ is the absolute elongation of the sample. In the stress-strain diagram of ductile metal materials, three characteristic sections can be distinguished: section OA(straight-line) corresponds
elastic deformation (such a relationship between the elongation of the sample and the applied load is called the law of proportional
Rice.
nality); plot LW(curvilinear) corresponds to elastoplastic deformation with increasing load; plot Sun(curvilinear) corresponds to elastoplastic deformation with decreasing load. At the point WITH the final destruction of the sample occurs, dividing it into two parts.
During the transition from elastic to elastoplastic deformation for some metallic materials, a small horizontal section may appear on the machine stress diagram LL", called the yield plateau. The sample elongates without increasing the load - the metal seems to flow. The lowest stress at which deformation of the test sample continues without a noticeable increase in load is called the physical yield strength.
Fluidity is characteristic only of low-carbon annealed steel, as well as some grades of brass. There is no yield plateau on the tensile diagrams of high-carbon steels.
With increasing elastoplastic deformation, the force with which the sample resists increases and reaches at the point IN its maximum value. For plastic materials, at this moment, a local narrowing (neck) is formed in the weakest section of the sample, where further deformation causes the sample to rupture.
When stretched, the strength and ductility of materials is determined.
Strength indicators materials are characterized by stress a, equal to the ratio of the load to the cross-sectional area of the sample (at characteristic points of the tensile diagram).
The most commonly used indicators of material strength include: yield strength, proof strength, tensile strength.
Yield strength a t, MPa - the lowest stress at which the material deforms (flows) without a noticeable change in load:
A. g = Р T /Р 0,
Where R t - load corresponding to the yield area on the tensile diagram (see Fig. 2.7); P 0 - cross-sectional area of the sample before testing.
If there is no yield plateau on the machine tensile diagram, then a tolerance for residual deformation of the sample is specified and the conditional yield strength is determined.
Conditional yield strength a 02, MPa - stress at which permanent elongation reaches 0.2% of the initial design length of the sample:
a 0.2 = A)2 /^0’
Where R 02 - load corresponding to permanent elongation
D/ 0>2 = 0.002/ 0.
Tensile strength a in, MPa - stress corresponding to the greatest load R tah, preceding sample rupture:
Plasticity index. Plasticity is one of the important mechanical properties of metal, which, combined with high strength, makes it the main structural material. The most commonly used plasticity indicators are:
Relative elongation 5,% - the greatest elongation to which the sample is deformed uniformly along its entire calculated length, or in other words, the ratio of the absolute increment in the calculated length of the sample D/p before loading R max to its original length (see Fig. 2.7):
8 = (D/ r //o)100 = [(/ r - /o)//(,]! 00.
Similar to the limiting uniform elongation, there is a relative narrowing of 1|/ (%) of the cross-sectional area:
y = (A/’ p // , 0)100 = [(/- 0 - r r ur 0 ] T,
Where E 0- initial cross-sectional area of the sample; E r - area at the rupture site.
For brittle metals, the relative elongation and relative contraction are close to zero; for plastic materials they reach several tens of percent.
Elastic modulus? (Pa) characterizes the rigidity of the metal, its resistance to deformation and represents the ratio of the stress in the metal during tension to the corresponding relative elongation within the limits of elastic deformation:
E= a/ 8.
Thus, during a static tensile test, strength indicators (a m, a 02, a b) and ductility indicators (8 and |/) are determined.
Hardness tests. Hardness is the property of a material to resist contact deformation or brittle fracture when a carbide tip (indenter) is introduced into its surface. Hardness testing is the most accessible and common method of mechanical testing. The most widely used in technology are static methods of testing for hardness when indenting an indenter: the Brinell method, the Vickers method and the Rockwell method.
When testing for hardness using the Brinell method, a carbide ball with a diameter of /) is pressed into the surface of the material under the influence of a load. R and after removing the load, the diameter is measured With! imprint (Fig. 2.8, A).
The Brinell hardness number (HH) is calculated using the formula
HB = P/E,
Where R - ball load, N; .Г - surface area of the spherical imprint, mm 2.
A certain load corresponds to a specific hardness value. Thus, when determining the hardness of steel and cast iron,
Rice. 2.8. Brinell hardness testing schemes (A), Vickers (b),
Rockwell (V)
load on the ball P= ZO/) 2 ; for copper, its alloys, nickel, aluminum, magnesium and their alloys - P= 10/) 2 ; for babbitts - P = 2,5/) 2 .
The thickness of the metal under the print must be no less than ten times the depth of the print, and the distance from the center of the print to the edge of the sample must be no less than 1/2).
Lever presses are currently mainly used for Brinell hardness testing.
Using the Brinell method, materials with a hardness of 4500 HB can be tested. If the materials are harder, the steel ball may become deformed. This method is also not suitable for testing thin sheet material.
If Brinell hardness was tested with a ball with a diameter of 10 mm and a load of 29-430 N, then the hardness number is indicated by numbers characterizing the hardness value and the letters “HB”, for example 185HB.
If the tests were carried out under other conditions, then after the letters “НВ” these conditions are indicated: ball diameter (mm), load (kgf) and duration of exposure under load (s): for example 175НВ5/750/20.
This method can test materials with a hardness of no more than 450HB.
When testing for hardness using the Vickers method, a diamond tetrahedral pyramid with an angle of 136° at the apex is pressed into the surface of the material (Fig. 2.8, b). After removing the indentation load, the diagonal is measured c1 x imprint. The Vickers hardness number (HH) is calculated using the formula
NU= 1.854 R/b 2,
arithmetic mean value of the length of both diagonals of the print, mm.The Vickers hardness number is designated by the letters “NU” indicating the load R and holding time under load, and the dimension of the hardness number (kgf/mm 2) is not set. The duration of exposure of the indenter under load is 10-15 s for steels, and 30 s for non-ferrous metals. For example, 450НУ10/15 means that a Vickers hardness of 450 was obtained at P= 10 kgf applied to the diamond pyramid for 15 s.
The advantage of the Vickers method over the Brinell method is that the Vickers method can test materials of higher hardness due to the use of a diamond pyramid.
When testing for hardness using the Rockwell method, a diamond cone with an angle of 120° at the apex or a steel ball with a diameter of 1.588 mm is pressed into the surface of the material. However, according to this method, the depth of the indentation is taken as a conditional measure of hardness. The Rockwell test scheme is shown in Fig. 2.8, V. First a preload is applied P 0, under the influence of which the indenter is pressed to a depth And (y Then the main load is applied R x, under the influence of which the indenter is pressed to a depth /?,. After this the load is removed R ( , but leave preload R 0 . In this case, under the influence of elastic deformation, the indenter rises up, but does not reach the level And 0 . Difference (AND- /g 0) depends on the hardness of the material. The harder the material, the smaller this difference. The depth of the print is measured by a dial indicator with a division value of 0.002 mm. When testing soft metals using the Rockwell method, a steel ball is used as an indenter. The sequence of operations is the same as for testing with a diamond cone. Hardness determined by the Rockwell method is designated by the letters “H11”. However, depending on the shape of the indenter and the values of the indentation loads, the following letters are added to this symbol: A, C, B, indicating the corresponding measurement scale.
The Rockwell method, compared to the Brinell and Vickers methods, has the advantage that the hardness value according to the Rockwell method is recorded directly by the indicator, eliminating the need for optical measurement of the print size.
Impact strength tests (impact bending). If this or that part of a machine or mechanism, due to its purpose, experiences shock loads, then the metal for the manufacture of such a part, in addition to static tests, is also tested under dynamic load, since some metals with sufficiently high static strength indicators are destroyed under low impact loads. Such metals are, for example, cast iron and steels with coarse-grained structures.
To assess the susceptibility of materials to brittle fracture, impact bending tests on notched specimens are widely used, as a result of which the impact strength is determined. Impact toughness is estimated by the work expended on the impact fracture of the sample, divided by its cross-sectional area at the point of the cut.
To determine impact strength, prismatic samples with various cuts are used. The most common are samples with U- and Y-shaped cuts.
Impact strength tests are carried out on a pendulum impact driver (Fig. 2.9). A pendulum of weight C is raised to a height /?, and then released. The pendulum, falling freely, hits the sample and destroys it, continuing its inertial movement to a height of /? 2.
The work spent on impact fracture of the sample is determined by the formula
K=0(And x-L 2),
where C is the weight of the pendulum; /?, is the height of the pendulum before testing; L 2 - the height of the pendulum after testing.
The pointer on the piledriver scale records the work TO.
Impact strength has the designations: KSU and KSI, where the first two letters indicate the symbol of impact strength, the third (V or i) - the type of concentrator (notch). The beat is counting
Rice. 2.9.A- pendulum pile driver; b- location of the sample on the pile driver; 1 - frame; 2 - pendulum; 3 - sample
viscosity as the ratio of work to the cross-sectional area of the sample in the notch:
KS = AG/^o,
Where TO - impact work to fracture the sample; 5 0 - cross-sectional area of the sample at the incision site.
Technological tests or metal testing is carried out to determine the ability of metals to accept deformation similar to that to which it must be subjected under processing or operating conditions. Technological tests of metals are carried out:
- on draft;
- flattening;
- wire winding;
- bend, bend;
- extrusion;
- weldability;
- deployment of shaped material, etc.
Technological samples of metals in many countries (including
including Russia) are standardized. Technological tests do not provide numerical data. The quality of the metal during these tests is assessed visually by the state of the metal surface after the test. For example, to assess the quality of pipes, technological tests are carried out for expansion, flattening, beading, stretching and ring expansion, as well as hydraulic pressure.
In order to assess the ability of a metal to plastically deform without violating its integrity during pressure treatment, its technological plasticity (deformability) is determined. Sometimes the ability to deform is called by the name of a specific process: stampability (extrusion test).
Stampability is determined by pressing the punch through sheet material up to 2 mm thick, sandwiched between the matrix and the clamp; serves to determine the ability of a metal to cold stamping and drawing.
Rollability - longitudinal rolling of wedge-shaped samples (rolling onto a wedge), serves to approximately determine the maximum degree of deformation for a given material.
Piercing - helical rolling of conical or cylindrical samples with braking, serves for an approximate (conical sample) or more accurate (cylindrical sample) determination of the maximum compression before the mandrel toe when piercing the workpieces.
Weldability determines the tensile strength of the weld. With good weldability, the tensile strength along the seam should be at least 80% of the tensile strength of the solid sample.
The bend test determines the ability of a metal to withstand bending; used to assess the quality of strip and sheet metal, as well as wire and rods.
Upsetting tests are carried out to determine the ability of a metal to take a given shape in a cold state, without allowing cracks, ruptures, breaks, etc. Such tests are carried out for rivet metals.
The flattening test determines the ability of a metal to deform when flattened. As a rule, sections of welded pipes with a diameter of 22-52 mm and a wall thickness of 2.5 to 10 mm are subjected to such tests. The test consists of flattening the sample under a press, which is performed until a gap is obtained between the inner walls of the pipe, the size of which is equal to four times the thickness of the pipe wall, and the sample should not have cracks.
Strength is the ability of a metal not to succumb to destruction under the influence of external loads. The value of metal as an engineering material, along with other properties, is determined by its strength.
The strength value indicates how much force is needed to overcome the internal bond between molecules.
Testing of metals for tensile strength is carried out on special machines of varying power. These machines consist of a loading mechanism that generates force, produces tension on the test specimen, and indicates the amount of force applied to the specimen. The mechanisms can be mechanical or hydraulic.
The power of the machines varies and reaches 50 tons. In Fig. 7, a shows the structure of the machine, consisting of a frame 2 and clamps 4, with the help of which the test samples 3 are secured.
The upper clamp is fixedly fixed in the frame, and the lower one, using a special mechanism, slowly lowers during testing, stretching the sample.
Rice. 7. Tensile testing of metals:
a - a device for testing metals for tension; b - samples for tensile testing: I - round, II - flat
The load transferred to the sample during testing can be determined by the position of the instrument pointer on measuring scale 1.
Testing of samples should always be carried out under the same conditions so that the results obtained can be compared. Therefore, the relevant standards establish certain dimensions of test specimens.
Standard specimens for tensile testing are the round and flat specimens shown in Fig. 7, b.
Flat samples are used when testing sheets, strip material, etc., and if the metal profile allows, then round samples are made.
The tensile strength (σ b) is the maximum stress that a material can experience before it fails; the tensile strength of a metal is equal to the ratio of the greatest load when testing a sample for tensile strength to the original cross-sectional area of the sample, i.e.
σ b = P b /F 0 ,
where P b is the greatest load preceding the rupture of the sample, kgf;
F 0 - initial cross-sectional area of the sample, mm 2.
For the purpose of safe operation of machines and structures, it is necessary that during operation the stresses in the material do not exceed the established limit of proportionality, i.e., the highest stress at which deformations are not caused.
Tensile strength of some metals during tensile testing, kgf/mm 2:
Lead 1.8
Aluminum 8
Answers to TCM exams.
1. Structure of structural materials.
Metals- crystalline bodies, the atoms of which are arranged in a geometrically regular order, forming crystals, in contrast to amorphous bodies (for example, resin), the atoms of which are in a disordered state.
Arranged in metals in a strict order, atoms in the plane form an atomic network, and in space - an atomic-crystal lattice. The lines in these diagrams are symbolic; in reality, no lines exist, and the atoms vibrate near equilibrium points, i.e., lattice nodes, with a high frequency. The unit cells of such crystal lattices are shown in Fig. 1. All crystalline bodies form seven types of crystal lattices, of which the most typical for metals are body-centered cubic (bcc), face-centered cubic (fcc) and hexagonal close-packed (hcp) (Fig. 1)
In a cell cubic body-centered lattice atoms are located at the vertices of the cube and in the center of the cube; Chrome, vanadium, tungsten, molybdenum, etc. have such a lattice. In the cell cubic face-centered lattice atoms are located at the vertices and in the center of each face of the cube; Aluminum, nickel, copper, lead, etc. have such a lattice. In the cell hexagonal lattice atoms are located at the vertices of the hexagonal bases of the prism, at the center of these bases and inside the prism; Magnesium, titanium, zinc, etc. have a hexagonal lattice. In a real metal, the crystal lattice consists of a huge number of cells.
The dimensions of the crystal lattice are characterized by its parameters, measured in angstroms - A (1A = 10 -8 cm or lA = 0.1 Nm). The cubic lattice parameter is characterized by the length of the edge of the cube, denoted by the letter A and is in the range of 0.28-0.6 Nm (2.8 - 6A). To characterize a hexagonal lattice, two parameters are taken - the side of the hexagon A and prism height With. When the attitude s/a -- 1.633, then the atoms are packed most densely, and therefore such a lattice is called hexagonal close-packed.
Fig.1. Atomic crystal structure of metals.
2. Types of crystal lattices.
The properties of a crystal are determined not only by the type of crystal lattice, but also by the nature of the interaction of atoms, ions and electrons with each other. When metal vapor passes into a liquid and then into a solid state, its atoms come so close that valence electrons are able to move from one atom to another and thus move freely throughout the entire volume of the metal, providing high electrical and thermal conductivity. Electrical interaction forces arise between electrons and positive ions.
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Rice. 2. Schemes of crystal lattices:
a – body-centered cubic; b - face-centered cubic; c - hexagonal close-packed.
Depending on temperature and pressure, many metals can form different types of crystal lattices. This ability of metals is called polymorphism or allotropy. Polymorphic transformations are characteristic of metals widely used in mechanical engineering such as Fe, Ti, Mn, Co, Sn. Polymorphic modifications of elements are usually designated, starting from the lowest temperature, with the letters α, β, γ, δ, etc. For example: iron, when heated to a temperature of 910 ° C, forms the modification α-Fe with a bcc lattice, in the range 910-1400 °C - γ-Fe with an fcc lattice and above 1400 °C - δ-Fe with a bcc lattice. In this case, a significant change in the properties of the material occurs. This phenomenon is widely used in technology to improve the workability of metals during heat treatment and other processes.
To characterize the shape and size of the unit cell of the crystal lattice, six main parameters are used (Fig. 2): distances along the coordinate axes - a, b, c called the lattice period, and three angles - α, β, γ between these segments. In addition to the main parameters in crystallography, others are also adopted that additionally characterize the crystal lattice.
3. Anisotropy of crystals and its influence on the properties of materials.
In different planes of the crystal lattice, atoms are located with different densities and therefore many properties of crystals in different directions are different. This difference is called anisotropy.
All crystals are anisotropic. Unlike crystals, amorphous bodies (for example, resin) in different directions have essentially the same atomic density and, therefore, the same properties, i.e. they isotropic.
In metals consisting of a large number of differently oriented small anisotropic crystals (polycrystal), the properties in all directions are the same (averaged). This apparent independence of properties from direction is called quasi-isotropy*.
If the same orientation of the crystals is created in the metal structure, then anisotropy appears.
When a metal transitions from a liquid to a solid state, the so-called process occurs crystallization. The fundamentals of the theory of crystallization were developed by the founder of the science of metals - metallurgy D.K. Chernov, who established that crystallization consists of two processes: the nucleation of the smallest particles of crystals (crystallization nuclei) and the growth of crystals from these centers (Fig. 3).
Fig.3. Successive stages of the crystallization process.
The growth of crystals consists in the fact that more and more atoms of liquid metal are added to their nuclei. At first, the crystals grow freely, maintaining the correct geometric shape, but this happens only until the growing crystals meet. At the point where the crystals come into contact, the growth of their individual faces stops and not all, but only some of the crystal faces develop. As a result, the crystals do not have the correct geometric shape. Such crystals are called crystallites or grains. The size of the grains depends on the number of crystallization centers and the rate of crystal growth. The more crystallization centers, the more crystals are formed in a given volume and each crystal (grain) is smaller. The formation of crystallization centers is affected by the cooling rate. The greater the cooling rate of the metal, the more crystallization centers appear in it, and the grains become smaller (Fig. 4). This is confirmed in practice in thin sections of cast parts that cool more quickly; the metal always turns out to be finer-grained than in thick massive cast parts that cool more slowly. However, it is not always possible to regulate the cooling rate.
All crystals are characterized by anisotropy, i.e., uneven properties in directions, determined by different distances between atoms in the crystal cell. Anisotropy is most pronounced in metals with an asymmetric crystalline structure. The direction of action of forces in a crystal significantly depends on indicators of physical properties such as strength characteristics, modulus of elasticity, thermal expansion coefficient, coefficients of thermal and electrical conductivity, light refractive index, etc. Anisotropy is also characteristic of the surface layers of crystals. Properties such as surface tension, electronic potentials, adsorption capacity, and chemical reactivity vary significantly between different crystal faces.
Fig.4. The influence of cooling rate on the occurrence of crystallization centers and on the size of the resulting grains.
1 - slow cooling, 2 - accelerated cooling, 3 - fast cooling.
4. Defects in crystal lattices.
The structure and properties of real crystals differ from the ideal ones shown in Fig. 1, due to the presence of defects in them, which are divided into superficial and internal. A real single crystal has a free (outer) surface, on which the lattice will be distorted due to surface tension. This distortion can extend to the area adjacent to the surface.
Fig.5. Crystal lattice defects :
A- point; b- linear; V - two-dimensional (planar)
Defects of the internal structure are divided into zero-dimensional (point), one-dimensional - linear and two-dimensional, i.e. developed in two directions. Point defects include: vacancies in the case when individual sites of the crystal lattice are not occupied by atoms; dislocated atoms, when individual atoms find themselves in interstices, or impurity atoms, the number of which even in pure metals is very large. Near such defects, the lattice will be elastically distorted at a distance of one or two of its periods (Fig. 5, A). Although the relative concentration of point defects may be small, they cause extremely large changes in the physical properties of the material. For example, thousandths of an atomic percent of impurities in pure semiconductor crystals change their electrical resistance by 10 5 -10 8 times.
Linear defects are small in two dimensions of the crystal lattice and quite large in the third. Such defects include displacements of atomic planes or dislocations and chains of vacancies (Fig. 5, b). The most important property of such defects is their mobility inside the crystal and active interaction with each other and with other defects.
The density of dislocations in crystals is high: in undeformed crystals their number per 1 cm 3 reaches 10 6 -10 8; During plastic deformation, new dislocations appear, and this number increases thousands of times. Two-dimensional defects are characteristic of polycrystalline materials, that is, for materials consisting of a large number of small crystals, differently oriented in space.
The boundary of crystals fused during solidification is a thin zone, up to 10 atomic diameters, with a disorder in the arrangement of atoms. In a polycrystalline body, the boundaries of individual crystals have curved interfaces, and the crystals themselves have an irregular shape. Therefore, in contrast to regularly bounded crystals, they are called crystallites or grains. During solidification, polycrystal grains grow from different crystallization centers and the orientation of the crystal lattice axes of neighboring grains is different. The metal grain consists of individual blocks oriented one relative to the other at a slight angle. The boundaries between them are usually clusters of dislocations (Fig. 5, V). Surface defects are small in only one direction; in the other two they can reach crystallite size.
5. The influence of crystal lattice defects on the properties of materials.
The influence of structural defects on the properties of materials is enormous. For example, the shear strength of real crystals due to the presence of structural defects decreases by three to four orders of magnitude compared to the same characteristic of an ideal crystal. The influence of structural defects on the strength characteristics of metals is not clear. From the one shown in Fig. Figure 6 shows that the strength of practically defect-free crystals (the so-called “whiskers”) is very high. Increase in quantity P structural defects of 1 cm 3 leads to a sharp decrease in strength (branch A). Dot R k characterizes the strength of metals, which are commonly called “pure”. A further increase in defects, for example, by introducing alloying impurities or methods of special distortion of the crystal lattice, increases the real strength of metals (branch IN). To create the most durable materials, they try to obtain the optimal number of defects. The greatest strengthening is achieved at a dislocation density of 10 12 -10 18 per 1 cm 3.
Rice. 6. Dependence of the strength of a crystalline body on the density of structural defects
In addition to influencing the strength characteristics, lattice defects play a large role in the processes of diffusion and self-diffusion, which largely determine the rates of chemical reactions in a solid, as well as the ionic conductivity of crystals. Defects in the crystal lattice, distributed in the required manner throughout the volume of the crystal, make it possible to create regions with different types of conductivity in one sample, which is necessary in the manufacture of some semiconductor elements.
6. Types of alloy crystal lattices.
In technology, it is much more common not to use pure metals, but alloys consisting of two or more elements, called components. The components of alloys can be either pure elements or chemical compounds. The widespread use of alloys as engineering materials can be explained by the fact that they have a diverse set of properties that can be specifically changed depending on the number and type of components, as well as using thermal or other types of processing.
Rice. 7. Types of crystal lattices of alloys.
A- substitutional solid solution; b- interstitial solid solution; V - chemical compound
A b
strength A.
Where R F 0
7. The concept of phases, types of phases.
When fused, the components form phases in the alloy - homogeneous volumes, delimited from each other by interfaces - boundaries, when passing through which the properties can change abruptly. The following main phases are formed in alloys: solid solutions, chemical compounds and mechanical mixtures.
Solid solutions are the most common phase in metal alloys. A characteristic feature of their structure is the preservation of the crystal lattice of the solvent metal. Dissolved metals can be distributed in it in the form of a substitutional solid solution (Fig. 7, A) if both components have the same type of lattices, fairly close atomic radii and physicochemical properties, or in the form of an interstitial solid solution (Fig. 7, b), if the atomic radius of the dissolved component is small enough.
Chemical compounds usually form between metals and non-metals and have the properties of non-metallic inclusions, as well as between metals. In this case, a new type of crystal lattice is formed, different from the lattices of the constituent components and having other properties (Fig. 7, c). When alloying components with very different atomic radii and electrochemical properties, mutual solubility is practically absent. In this case, a mechanical mixture of component crystals is formed.
As a rule, in multicomponent metal alloys three types of phases can be found simultaneously. By purposefully changing the combination of components in alloys, it is possible to change the number of structural defects and, therefore, control the physical and mechanical characteristics.
When choosing a material for a structure, they proceed from a set of properties, which are divided into mechanical, physico-chemical, technological and operational. The main mechanical properties include strength, ductility, impact strength, fatigue strength, creep, hardness and wear resistance. Under strength understand the ability of a material to resist deformation or destruction under the influence of static or dynamic loads. Under static loads, tensile, compression, bending and torsion tests are performed. The strength indicator is the tensile strength of the test metal sample shown in Fig. 9, A.
Where R- load required to destroy the standard sample, MN; F 0- cross-sectional area of the sample in mm.
8. Mechanical properties of structural materials.
Methods for testing the mechanical properties of metals.
Depending on the method of applying the load, methods for testing the mechanical properties of metals are divided into three groups:
static, when the load increases slowly and smoothly (tensile, compression, bending, torsion, shear, hardness tests);
dynamic, when the load increases at high speed, shock (impact test);
tests under repeated-variable loads, when the load during the test changes many times in magnitude or in magnitude and sign (fatigue test).
The need to test under different conditions is determined by the difference in operating conditions of machine parts, tools and other metal products.
Tensile test. For tensile testing, cylindrical or flat samples of a certain shape and size according to the standard are used. Tensile testing of samples is carried out on tensile testing machines with a mechanical or hydraulic drive. These machines are equipped with a special device on which, during testing (tension), a tensile diagram is automatically recorded.
Considering that the nature of the tensile diagram is influenced by the size of the sample, the diagram is constructed (Fig. 8) in the coordinates stress σ (in N/m 2 or kgf/mm 2) - relative elongation δ (in % ). When testing tensile strength, the following characteristics of mechanical properties are determined: limits of proportionality, elasticity, fluidity, strength, true tensile strength, relative elongation and contraction.
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Rice. 8. Tension diagram.
Limit of proportionality(conditional) σ pts is the stress when the deviation from the linear relationship between load and elongation reaches such a value at which the tangent of the angle formed by the tangent to the load-strain curve with the load axis increases, for example, by 25 or 50% compared to original value:
Where R pr- load corresponding to the proportionality limit (conditional).
Elastic limit(conditional) σ up is called the stress at which the residual elongation reaches 0.05% of the calculated value of the sample and is determined by the formula:
Where P 0.05- load corresponding to the elastic limit (conditional).
Yield strength(physical) σ t is the lowest stress at which the sample deforms (flows) without a noticeable increase in load:
Where R t- load corresponding to the yield strength (physical).
Yield strength(conditional) σ 0.2 is the stress at which the permanent elongation reaches 0.2% of the calculated length of the sample:
Where P 0.2- load corresponding to the yield strength (conditional).
Tensile strength(temporary resistance) σ in is called the voltage corresponding to the greatest load R in, preceding the destruction of the sample:
True resistance to destruction S K called the voltage determined by the load ratio R k at the moment of sample rupture to the cross-sectional area F K sample in the neck after rupture:
Relative elongationδ is called the ratio of absolute elongation, i.e., the increment in the calculated length of the sample after rupture ( l k - l 0), to its original gauge length l 0 , expressed as a percentage:
,
Where l k is the length of the sample after rupture.
Relative elongation is characterized plasticity metal is the property of solid materials to change shape and size without destruction under the influence of load or stress, stably maintaining the resulting shape and size after the cessation of this influence.
Fig.9. Tests to determine mechanical characteristics:
a – ultimate strength and plastic characteristics; b - impact strength; c - hardness (according to Brinell)
Strength under dynamic loads is determined according to test data: for impact strength - by destruction by impact of a standard sample on a pile driver (Fig. 9b), for fatigue strength - by determining the ability of a material to withstand, without collapsing, a large number of repeatedly variable loads, for creep - by determining the ability of a heated material slowly and continuously deforms under constant loads. The most commonly used impact tests are:
Where A- work spent on sample destruction, MJ; A = PH - Ph, Here R- pendulum weight, MN; F- cross-sectional area of the destroyed sample, m2.
Hardness test.Hardness is the ability of a metal to resist the penetration of another, harder body into it. Hardness testing is the most commonly used method for testing metals. To determine hardness, the manufacture of special samples is not required, i.e. the test is carried out without destroying the part.
There are various methods for determining hardness - indentation, scratching, elastic recoil, as well as the magnetic method. The most common method is to press a steel ball, diamond cone or diamond pyramid into the metal. For hardness testing, special devices are used that are simple in design and easy to use.
Brinell hardness A hardened steel ball with a diameter of 10, 5 or 2.5 mm is pressed into the surface of the metal being tested with a certain force. As a result, an imprint (hole) is formed on the metal surface. The diameter of the print is measured with a special magnifying glass with divisions. The Brinell hardness number is written in Latin letters HB, followed by a numerical hardness index. For example, hardness according to HB 220. The Brinell method is not recommended for metals with a hardness of more than HB 450, since the ball may be deformed and the result will be incorrect. You should also not test thin materials that are pressed through when the ball is pressed.
Rockwell hardness - hardness test by pressing a cone or ball into the surface of the metal being tested. A diamond cone is pressed at an angle of 120° or a hardened steel ball with a diameter of 1.59 mm. Ball tests are used to determine the hardness of soft materials, and diamond cone tests are used when testing hard materials. The Rockwell hardness number is written in Latin letters HRC, followed by the numerical value of hardness. For example, hardness HRC 230.
Vickers hardness - Pyramid indentation hardness test. A tetrahedral diamond pyramid is pressed into the surface of the metal. Based on the load per unit surface of the print, the hardness number, designated HV 140, is determined.
Microhardness test. This test is used to determine the hardness of microscopically small volumes of metal, for example, the hardness of individual structural components of alloys. Microhardness is determined using a special device consisting of a loading mechanism with a diamond tip and a metallographic microscope. The sample surface is prepared in the same way as for microstudy (grinding, polishing, etching). A tetrahedral diamond pyramid (with an apex angle of 136°, the same as the Vickers pyramid) is pressed into the test material under very low load. Hardness is determined by the value N/m 2 or kgf/mm 2.
Wear resistance- the ability of a material to resist surface destruction under the influence of external friction.
To physical and chemical properties materials include melting point, density, electrical and thermal conductivity, coefficients of linear and volumetric expansion, the ability to react chemically with aggressive media, as well as anti-corrosion properties. The listed properties are largely determined by the chemical composition of the alloy components and their structure.
Technological properties
Foundry properties
Ductility
Weldability
Machinability
The performance of a structure is determined by the operational or service characteristics of the materials used for their manufacture. Depending on the operating conditions and working environment, in addition to strength characteristics, engineering materials can be subject to heat resistance requirements, i.e., maintaining high mechanical characteristics at high temperatures; corrosion resistance when working in various aggressive environments; increased wear resistance, necessary if parts are subject to abrasion during operation, etc. In some cases, materials must have the ability to form permanent connections by welding or soldering with other materials, in particular, with ceramics, graphite, etc.
9. Technical properties of structural materials.
Technological properties metals and alloys are characterized by their ability to be amenable to various methods of hot and cold working. The main ones include casting properties, malleability, weldability and machinability with cutting tools.
Foundry properties characterize the ability of a metal or alloy to fill a casting mold, to ensure the production of a casting of a given size and configuration without pores and cracks in all its parts.
Ductility- this is the ability of a metal or alloy to deform with minimal resistance under the influence of an external applied load and take a given shape. Malleability depends on many external factors, in particular the heating temperature and the stress pattern.
Weldability call the ability of a material to form permanent connections with a set of properties that ensure the operability of the structure. Based on the degree of weldability, materials are divided into well and limitedly weldable. Weldability depends both on the material of the workpieces being welded and on the selected welding process.
Machinability called the property of a metal to be machined by cutting. The machinability criteria are cutting conditions and the quality of the machined surface.
Technological properties often determine the choice of material for a structure. Developed materials can be introduced into production only if their technological properties meet the necessary requirements. Indicators of technological properties are determined by special tests for malleability, workability, weldability, as well as casting tests.
The performance of a structure is determined by the operational or service characteristics of the materials used for their manufacture. Depending on the operating conditions and working environment, in addition to strength characteristics, engineering materials can be subject to heat resistance requirements, i.e., maintaining high mechanical characteristics at high temperatures; corrosion resistance when working in various aggressive environments; increased wear resistance, necessary if parts are subject to abrasion during operation, etc. In some cases, materials must have the ability to form permanent connections by welding or soldering with other materials, in particular, with ceramics, graphite, etc.
Consequently, when choosing a material to create a technological design, it is necessary to comprehensively take into account its strength, technological and operational characteristics.
10. Casting alloys.
Casting alloys and their application. Casting alloys are produced by fusing two or more metals and non-metals. Such alloys must have good electrical and thermal conductivity, increased ductility, etc. The practical importance of casting alloys is determined by the fact that they are superior to pure metals in some properties (strength, hardness, ability to reproduce the outlines of casting molds, machinability with cutting tools, etc.). Alloys with special physical properties (for example, electrical conductivity, magnetic permeability, etc.) occupy an important place in foundry production.
Alloys, depending on their chemical composition, differ from each other in melting point, chemical reactivity, viscosity in the molten state, strength, ductility and other properties. For the production of shaped castings, gray, high-strength, malleable and other cast irons, carbon and alloy steels, alloys of aluminum, magnesium, copper, titanium, etc. are used.
Gray cast iron(composition in%: 2.8-3.5 C; 1.8-2.5 Si; 0.5-0.8 Mn; up to 0.6 P and up to 0.12 S) has a fairly high strength, high cyclic viscosity, easy to process and cheap. The disadvantage of gray cast iron is low impact strength and brittleness. The strength of gray cast iron is due to the lamellar shape of the graphite inclusions and the strength of the metal base. Gray cast iron is used to make machine beds, gearbox housings and covers, pulleys and other castings.
Ductile iron(composition in%: 3.2-3.6 C; 1.6-2.9 Si; 0.4-0.9 Mn; not more than 0.15 P; not more than 0.02 S; not less than 0. 04 Mg) has high strength, ductility, and is easy to process. The high mechanical properties of these cast irons are obtained by treating molten cast iron with magnesium or cerium, in which the graphite takes on a spherical shape. High-strength cast iron is used to produce critical, heavily loaded parts: crankshafts, mine car drums, connecting rods, etc.
Malleable iron(composition in%: 2.4-2.8 C; 0.8-1.4 Si; less than 1 Mn; not less than 0.2 P; not less than 0.1 S) exceeds gray cast iron in strength and has high ductility . Malleable cast iron is obtained by annealing white cast iron castings (in white cast iron, carbon is almost completely in a bound state in the form of Fe 3 C) for 30-60 hours at a temperature of 900-1050 ° C. During annealing, graphite is formed in the form of flakes (Fig. 6, f). Depending on the annealing conditions, malleable cast iron can be ferritic (CC 37-12), ferritic-pearlite (CC 45-6) and pearlitic (CC 63-2). Malleable cast iron is used to produce pneumatic tool bodies, hubs, brackets, chain links and other parts.
Carbon steels(composition in%: 0.12-0.6 C; 0.2-0.5 Si; 0.5-0.8 Mn; up to 0.05 P and up to 0.05 S) have higher mechanical properties, than gray and ductile cast iron. Carbon steels are used for the manufacture of various cylinders, rolling mill beds, gears and other products.
Alloy steels differ from carbonaceous ones in the composition of alloying elements, i.e., additionally added elements (chromium, nickel, molybdenum, titanium, etc.) or a higher content of manganese and silicon. Alloying elements give steel high corrosion resistance, heat resistance and other special properties. Turbine blades, exhaust manifolds, various fittings and other similar parts are made from alloy steels.
Aluminum alloys They have low density, high strength and ductility, and are easy to process. The most common alloys of aluminum with silicon (silumins), which have increased corrosion resistance, good weldability and other properties. Aluminum alloys are used in the production of cylinder blocks, instrument bodies and tools, etc.
Magnesium alloys have low density, high strength, good machinability. The disadvantage of magnesium alloys is their low corrosion resistance. To improve mechanical properties, almost all magnesium alloys are treated (modified) with hexachloroethane, chalk and other substances. Magnesium alloys are used to make housings for pumps, instruments and tools, and other parts.
Copper alloys(bronze and brass) have relatively high mechanical and antifriction properties, high corrosion resistance, and good machinability. For the manufacture of castings, tin and tin-free bronze and brass are used. Tin-free bronzes are used as substitutes for tin bronzes.
In terms of mechanical, corrosion and anti-friction properties, tin-free bronzes are superior to tin bronzes. Copper alloys are used in the production of fittings, bearings, propellers, gears, etc.
Aluminum, magnesium and copper alloys are widely used in instrument making.
11. Cast irons.
CAST IRON
Cast iron is an alloy of iron and carbon containing more than 2% C (more precisely, more than 2.14% C)
Depending on the state of carbon in cast iron, there are:
white cast iron, in which all the carbon is bound into cementite. In white cast iron, carbon forms the chemical compound Fe 3 C with iron, and free carbon is in the form of graphite.
gray cast iron, in which all the carbon is in a free state in the form of graphite, or part of the carbon (most) is in the form of graphite, and part in a bound state in the form of cementite. The form of graphite is lamellar.
ductile iron, the same as gray cast iron, but the shape of the graphite is spherical.
malleable iron, the same as gray cast iron, but the graphite is in flake form.
As can be seen from the above classification of cast iron, a distinctive feature of gray, high-strength and malleable cast iron is the presence of free carbon - graphite - in the structure. Depending on the shape and location of the graphite inclusions, they weaken the metal base in which they are located to a greater or lesser extent.
Textbook for vocational schools. - M.: Mechanical Engineering, 1990. - 256 p.: ill. — ISBN 5-217-00830-X. The fundamentals of the theory of strength and ductility of metals and alloys are presented in an accessible form. The device, principle of operation, rules of operation of instruments and equipment for testing and flaw detection are considered. The mathematical foundations for processing measurement results are presented. The textbook can be used to train workers in production. Safety, fire safety and industrial sanitation
Basic safety information.
Fire safety.
Industrial sanitation.
Basic properties of materials
Raw metal materials. Basic information about the production of metals and alloys.
Basic properties of metals and alloys.
Non-metallic materials, their properties and applications.
Fundamentals of the theory of elastic and plastic deformation and fracture
General characteristics and atomic-crystalline structure of metals and alloys.
The concept of stress-strain state.
Elastic and plastic deformation.
The influence of temperature on the strength and ductility of metals and alloys.
Information about the destruction process.
Mechanical testing of metals and alloys
Classification of test methods.
Static tests.
Impact bending tests.
Fatigue tests.
Long-term strength and creep tests.
Hardness measurement.
Equipment and instruments for mechanical testing
Classification of equipment and instruments for mechanical testing.
Design and principle of operation of machines for static tests.
Design and principle of operation of impact testing machines.
Design and principle of operation of machines for repeatedly variable loads (fatigue tests).
Design and principle of operation of machines for special tests.
Instruments for measuring hardness.
Control and measuring equipment used during testing.
Non-destructive testing methods. Determination of physical properties of metals and alloys
Classification of non-destructive testing methods.
Defects in metals and alloys, the causes of their occurrence.
Thermal methods for detecting defects.
Thermal analysis of phase transformations in metals and alloys.
Thermal analysis at high temperatures.
Thermal analysis at high heating and cooling rates.
Calorimetric analysis.
Dilatometric method.
Magnetic methods.
Electrical methods.
Parametric eddy current method.
Acoustic methods.
Penetrant control methods.
Leak detection methods.
Radiographic and radioscopic methods.
Testing of non-metallic materials
Testing of building materials and products.
Testing of textile materials.
Testing of plastics.
Special types of tests
Tests on the machinability of metals by cutting.
Technological tests.
Testing of metalworking tools.
Basic information about standardization, metrology and product quality control
State standards and metrology.
Standardization and product quality.
Standards for testing materials and finished products.
Requirements for test samples and methods for processing test results
Samples and production of test specimens from them.
Statistical processing of test results.
Registration of test results.
Bibliography