The use of amorphous bodies in human life. Amorphous bodies – Knowledge Hypermarket

The threads on the rods are depicted along the outer diameter with solid main lines, and along the inner diameter with solid thin lines.

You studied the basic elements of metric threads (outer and inner diameters, thread pitch, thread length and angle) in fifth grade. Some of these elements are indicated in the figure, but such inscriptions are not made on the drawings.

Threads in holes are depicted with solid main lines along the internal diameter of the thread and solid thin lines along the outer diameter.

Symbol thread shown in the figure. It should be read like this: metric thread (M) with an outer diameter of 20 mm, third class of accuracy, right-handed, with a large pitch - “Thread M20 class. 3".

In the figure, the thread designation is “M25X1.5 class.” 3 left” should be read as follows: metric thread, outer thread diameter 25 mm, pitch 1.5 mm, fine, third class of accuracy, left.

Questions

1. What lines represent the threads on the rod?
2. What lines show threads in a hole?
3. How are threads indicated on drawings?
4. Read the entries “M10X1 class. 3" and "M14X1.5 cl. 3 left."

Working drawing

Each product - a machine or mechanism - consists of separate, interconnected parts.

Parts are usually made by casting, forging, and stamping. In most cases, such parts are machined on metal-cutting machines - lathes, drilling, milling and others.

Drawings of parts, equipped with all instructions for manufacturing and control, are called working drawings.

The working drawings indicate the shape and dimensions of the part, the material from which it must be made. The drawings indicate the cleanliness of surface treatment and the requirements for manufacturing accuracy - tolerances. Manufacturing methods and technical requirements the finished part is indicated by an inscription on the drawing.

Cleanliness of surface treatment. On treated surfaces there are always traces of processing and unevenness. These irregularities, or, as they say, surface roughness, depend on the tool used to process.

For example, a surface processed with a garnish will be rougher (uneven) than after processing with a personal file. The nature of roughness also depends on the properties of the material of the product, on the cutting speed and feed rate when processing on metal-cutting machines.

To assess the quality of processing, 14 classes of surface cleanliness have been established. Classes are designated in the drawings by one equilateral triangle (∆), next to which the class number is indicated (for example, ∆ 5).

Methods for obtaining surfaces of different cleanliness and their designation in the drawings. The cleanliness of processing one part is not the same everywhere; therefore, the drawing indicates where and what kind of processing is required.

The sign at the top of the drawing indicates that for rough surfaces there are no requirements for cleanliness of processing. The sign ∆ 3 in the upper right corner of the drawing, taken in brackets, is placed if the same requirements are imposed on the surface treatment of the part. This is a surface with traces of processing with bastard files, roughing cutters, and an abrasive wheel.

Marks ∆ 4 - ∆ 6 - semi-clean surface, with barely noticeable traces of processing with a finishing cutter, personal file, grinding wheel, fine sandpaper.

Signs ∆ 7 - ∆ 9 - clean surface, without visible traces processing. This treatment is achieved by grinding, filing with a velvet file, or scraping.

Mark ∆ 10 - a very clean surface, achieved by fine grinding, finishing on whetstones, filing with a velvet file with oil and chalk.

Signs ∆ 11 - ∆ 14 - surface cleanliness classes, achieved by special treatments.

Manufacturing methods and technical requirements for the finished part are indicated in the drawings by the inscription (for example, blunt sharp edges, harden, burnish, drill a hole together with another part and other requirements for the product).

Questions

1. What symbols indicate the cleanliness of the surface treatment?
2. After what type of treatment can a surface finish of ∆ 6 be obtained?

Exercise

Read the drawing in the figure and answer the questions in writing using the form provided.

Questions for reading a drawing	Answers
1. What is the name of the part?	–
2. Where is it used?	–
3. List the technical requirements for the part	–
4. What is the name of the drawing type?	–
5. What conventions are there in the drawing?	–
6. What is general shape and dimensions of the part?	–
7. What thread is cut on the rod?	–
8. Specify the elements and dimensions of the part	–

“Plumbing”, I.G. Spiridonov,
G.P. Bufetov, V.G. Kopelevich

A part is a part of a machine made from a single piece of material (for example, a bolt, nut, gear, lathe lead screw). A node is a connection of two or more parts. The product is assembled according to assembly drawings. A drawing of such a product, which includes several assemblies, is called an assembly drawing; it consists of drawings of each part or assembly and depicts an assembly unit (a drawing of a single...

10.1.4. Image and designation of threads in the drawings

The image and designation of threads in the drawings are standardized. In accordance with GOST 2.311-68, external threads are depicted with solid main lines along the diameter D and solid thin lines along the diameter D 1 . In images obtained by projection onto a plane perpendicular to the thread axis, a solid thin line is not extended to 1/4 . The chamfer lines are not shown (Figure 10.6).

When depicting a thread, a solid thin line is drawn at a distance of at least 0.8 mm from the main line and no more than the pitch value. A solid thin line of the thread on the rod should intersect the chamfer boundary line.

Internal threads are shown with solid main lines - along the internal diameter d and solid thin ones - along the diameter d 1 . The thread boundary is applied at the end of the full profile, before the start of the run. It is drawn to the line of the outer diameter and is depicted as a solid thick line if the thread is visible, and dashed if it is invisible. Hatching in sections and sections is carried out to a solid thick line.

For all types of threads, excluding conical and cylindrical pipe threads, the designation refers to the outer diameter and is placed above the dimension line, on its extension and on the leader shelf (Figure 10.6).

Figure 10.6 - Symbol for internal and external threads

The designation of conical threads and cylindrical pipe threads refers to the contour of the thread and is applied only on the shelf of the leader line (Figure 10.7).

Figure 10.7 - Designation of conical and cylindrical pipe threads

Table 1 - Thread types and designations

	Profile	Designation
Metric GOST 9150-81 - on the profile GOST 24705-81 - for diameter sizes GOST 8724-81 - for diameters and pitches	Equilateral triangle. The tops of the protrusions and depressions of the profile are cut along a straight line or a circular arc, which facilitates the manufacture of threads, reduces stress concentration and protects the threads from damage during operation.	M20-6g - metric thread with a diameter of 20 mm, coarse pitch 2.5 mm, tolerance range 6g, right; M20×2- metric thread with a diameter of 20 mm, fine pitch 2 mm, right; M20×2L.H. - metric thread with a diameter of 20 mm, fine pitch 2 mm, left. The thread has one large and several small steps for each nominal diameter. The large pitch is not indicated in the thread designation, but the small pitch is required. LH is added to the left-hand thread designation.
	Metric threads are most widely used in technology. This thread is used on bolts, studs, screws, nuts, etc. Right-hand threads are preferably used.
Inch GOST 6111-52	An isosceles triangle with an apex angle of 55° (for a tapered thread - a profile angle of 60). The peaks and valleys are cut flat.	1" - inch cylindrical thread with an outer diameter of 1 inch; K 1 3 / 4" GOST 6111-52- inch conical thread.
Pipe cylindrical GOST 6357-81 Pipe conical GOST 6211-81	Isosceles triangle with an apex angle of 55°. The crests and valleys are rounded, which makes the thread more airtight than metric threads.	G1- A - cylindrical pipe thread with a diameter of 1 inch, accuracy class A; R1 - external conical pipe thread; Rc1 - internal conical pipe thread. Size 1"=25.4 mm corresponds to the internal diameter of the pipe (nominal bore). The outer diameter of the pipe thread will be 1" = 25.4 mm + 2 pipe thickness = 33.25 mm.
	Straight pipe threads are used on water and gas pipes, on parts for their connection - fittings (couplings, elbows, tees, etc.), pipeline fittings (gate valves), etc. Tapered pipe threads are used in pipe connections at high pressures and temperatures.
Trapezoidal GOST 9484-81 - on the profile, GOST 24738-81 - for diameters and pitches		Tr40×6-8e- trapezoidal thread, single-start, with a nominal diameter of 40 mm, pitch 6 mm, accuracy class 8e; Tr48×9(RZ)LN- trapezoidal thread, three-start, with a nominal diameter of 49 mm, stroke 9 mm, pitch 3 mm, left
	Used on screws that transmit reciprocating motion.
Persistent GOST 10177-82 for profile and main dimensions	Uneven-sided trapezoid with angles of 3° and 30° at the sides	S80×5- persistent thread, with a nominal diameter of 80 mm, single-start, with a pitch of 5 mm; S80×20(P5)LN- persistent thread, four-start, with a nominal diameter of 80 mm, stroke 20 mm, pitch 5 mm, left.
	Used on screws subject to unidirectional forces, for example, in jacks.
Rectangular	The profile is not standardized; the drawing provides all the data necessary for its manufacture.
	It is used in connections where there should be no self-unscrewing under the influence of an applied load.
	The profile is standard, but the diameter or pitch dimensions differ from those accepted by the standard.	Sp is added to the designation of any thread with a standard profile:

When the temperature drops, the liquid can freeze without ordering the structure. The substance is already in solid state, but its structure approaches the structure of a liquid - such substances are called amorphous (from Greek " amorphos" - shapeless)

Properties of amorphous bodies:

§ Main sign - lack of atomic or molecular lattice, that is, the three-dimensional periodicity of the structure characteristic of the crystalline state.

§ The amorphous state is characterized by presence of only short-range order. The structures of amorphous substances resemble liquids, but have much less fluidity.

§ The amorphous state is usually unstable. The amorphous state has a certain excess supply of internal energy, and therefore spontaneously transforms into a crystalline state as a more stable one. Because of this, most substances under normal conditions are still in a crystalline state.

§ Under the influence of mechanical loads or temperature changes, amorphous bodies can crystallize.

§ Fluidity(because according to some theories, amorphous bodies are considered as supercooled liquids). This property can be detected by careful examination of window glass in very old houses. The window glass in such houses is somewhat thicker at the bottom, since for a long time the glass constantly flowed down under the influence of gravity. Relatively recently we learned to receive metals in glassy state. To do this, the metal is melted, and then very quickly short time cool. Due to rapid cooling, the correct crystalline structure does not appear in the metal; it becomes glassy. Metal glass is characterized by high hardness, wear resistance and corrosion resistance.

§ Amorphous bodies isotropic , that is, their mechanical, optical, electrical and other properties do not depend on direction.

§ In amorphous bodies no fixed melting point: melting occurs in a certain temperature range. Transition of an amorphous substance from solid state into liquid is not accompanied by an abrupt change in properties. For example: the melting temperature range of silicate glasses is approximately 200°C.

Physical model the amorphous state has not yet been created.

Reactivity substances in the amorphous state is significantly higher than in the crystalline state.

Examples of amorphous substances: natural: honey, amber, rosin, resin, bitumen;

artificial: glass, many oxides, hydroxides.

There are substances that can only exist in solid form in an amorphous state. This applies to polymers with an irregular sequence of links.

In some cases, the same substance can be in different states, for example: SiO 2 exists in glassy and several crystalline states; also S-sulfur, there is amorphous sulfur and two crystalline modifications (orthorhombic and monoclinic).

Most substances in temperate climate The earth is in a solid state. Solids retain not only their shape, but also their volume.

By the nature of the relative arrangement of particles solids They are divided into three types: crystalline, amorphous and composites.

Amorphous bodies. Examples of amorphous bodies include glass, various hardened resins (amber), plastics, etc. If an amorphous body is heated, it gradually softens, and the transition to a liquid state takes a significant temperature range.

The similarity with liquids is explained by the fact that atoms and molecules of amorphous bodies, like liquid molecules, have time " settled life" There is no specific melting point, so amorphous bodies can be considered as supercooled liquids with very high viscosity. The absence of long-range order in the arrangement of atoms of amorphous bodies leads to the fact that a substance in an amorphous state has a lower density than in a crystalline state.

Disorder in the arrangement of atoms of amorphous bodies leads to the fact that the average distance between atoms is different directions the same, so they are isotropic, i.e. all physical properties(mechanical, optical, etc.) do not depend on the direction of external influence. Signs of an amorphous body are irregular shape fractured surfaces. Amorphous bodies after a long period of time still change their shape under the influence of gravity. This makes them look like liquids. As the temperature increases, this change in shape occurs faster. The amorphous state is unstable; a transition from the amorphous state to the crystalline state occurs. (The glass becomes cloudy.)

Crystalline bodies. If there is periodicity in the arrangement of atoms (long-range order), the solid is crystalline.

If you examine grains of salt with a magnifying glass or microscope, you will notice that they are limited by flat edges. The presence of such faces is a sign of being in a crystalline state.

A body that is one crystal is called a single crystal. Most crystalline bodies consist of many randomly located small crystals that have grown together. Such bodies are called polycrystals. A piece of sugar is a polycrystalline body. Crystals various substances have a variety of shapes. The sizes of the crystals are also varied. Poly crystal sizes crystalline type may change over time. Small iron crystals turn into large ones, this process is accelerated by impacts and shocks, it occurs in steel bridges, railway rails etc., from this the strength of the structure decreases over time.

So many bodies are the same chemical composition in the crystalline state, depending on conditions, they can exist in two or more varieties. This property is called polymorphism. Ice has up to ten modifications known. Carbon polymorphism - graphite and diamond.

An essential property of a single crystal is anisotropy - the dissimilarity of its properties (electrical, mechanical, etc.) in different directions.

Polycrystalline bodies are isotropic, that is, they exhibit the same properties in all directions. This is explained by the fact that the crystals that make up the polycrystalline body are randomly oriented relative to each other. As a result, none of the directions is different from the others.

Composite materials have been created mechanical properties which are superior to natural materials. Composite materials (composites) consist of a matrix and fillers. Polymer, metal, carbon or ceramic materials are used as a matrix. Fillers may consist of whiskers, fibers or wires. In particular, composite materials include reinforced concrete and ferrographite.

Reinforced concrete is one of the main types building materials. It is a combination of concrete and steel reinforcement.

Iron-graphite is a metal-ceramic material consisting of iron (95-98%) and graphite (2-5%). Bearings and bushings for various machine components and mechanisms are made from it.

Fiberglass is also a composite material, which is a mixture of glass fibers and hardened resin.

Human and animal bones are a composite material consisting of two completely different components: collagen and mineral matter.

Have you ever wondered what these mysterious amorphous substances are? They differ in structure from both solids and liquids. The fact is that such bodies are in a special condensed state, which has only short-range order. Examples of amorphous substances are resin, glass, amber, rubber, polyethylene, polyvinyl chloride (our favorite plastic windows), various polymers and others. These are solids that do not have a crystal lattice. These also include sealing wax, various adhesives, hard rubber and plastics.

Unusual properties of amorphous substances

During cleavage, no edges are formed in amorphous solids. The particles are completely random and are located at close distances from each other. They can be either very thick or viscous. How are they affected by external influences? Under the influence different temperatures bodies become fluid, like liquids, and at the same time quite elastic. In case external influence does not last long, substances of an amorphous structure can break into pieces with a powerful blow. Long-term influence from outside leads to the fact that they simply flow.

Try a little resin experiment at home. Place it on a hard surface and you will notice that it begins to flow smoothly. That's right, it's substance! The speed depends on the temperature readings. If it is very high, the resin will begin to spread noticeably faster.

What else is characteristic of such bodies? They can take any form. If amorphous substances in the form of small particles are placed in a vessel, for example, in a jug, then they will also take the shape of the vessel. They are also isotropic, that is, they exhibit the same physical properties in all directions.

Melting and transition to other states. Metal and glass

The amorphous state of a substance does not imply the maintenance of any specific temperature. At low values ​​the bodies freeze, at high values ​​they melt. By the way, the degree of viscosity of such substances also depends on this. Low temperature promotes reduced viscosity; high viscosity, on the contrary, increases it.

For substances of the amorphous type, one more feature can be distinguished - the transition to a crystalline state, and a spontaneous one. Why is this happening? Internal energy V crystalline body much less than in amorphous. We can notice this in the example of glass products - over time, the glass becomes cloudy.

Metallic glass - what is it? The metal can be removed from the crystal lattice during melting, that is, a substance with an amorphous structure can be made glassy. During solidification during artificial cooling, the crystal lattice is formed again. Amorphous metal has amazing resistance to corrosion. For example, a car body made from it would not need various coatings, since it would not be subject to spontaneous destruction. An amorphous substance is a body whose atomic structure has unprecedented strength, which means that an amorphous metal could be used in absolutely any industrial sector.

Crystal structure of substances

In order to have a good understanding of the characteristics of metals and be able to work with them, you need to have knowledge of the crystalline structure of certain substances. The production of metal products and the field of metallurgy could not have developed so much if people did not have certain knowledge about changes in the structure of alloys, technological techniques and operational characteristics.

Four states of matter

It is common knowledge that there are four state of aggregation: solid, liquid, gaseous, plasma. Amorphous solids can also be crystalline. With this structure, spatial periodicity in the arrangement of particles can be observed. These particles in crystals can perform periodic motion. In all bodies that we observe in a gaseous or liquid state, we can notice the movement of particles in the form of a chaotic disorder. Amorphous solids (for example, metals in a condensed state: hard rubber, glass products, resins) can be called frozen liquids, because when they change shape, you can notice such characteristic feature, like viscosity.

Difference between amorphous bodies and gases and liquids

Manifestations of plasticity, elasticity, and hardening during deformation are characteristic of many bodies. Crystalline and amorphous substances in to a greater extent have these characteristics, while liquids and gases do not have such properties. But you can notice that they contribute to an elastic change in volume.

Crystalline and amorphous substances. Mechanical and physical properties

What are crystalline and amorphous substances? As mentioned above, those bodies that have a huge viscosity coefficient can be called amorphous, and their fluidity is impossible at ordinary temperatures. But high temperature, on the contrary, allows them to be fluid, like a liquid.

Substances of the crystalline type appear to be completely different. These solids can have their own melting point, depending on external pressure. Obtaining crystals is possible if the liquid is cooled. If you do not take certain measures, you will notice that various crystallization centers begin to appear in the liquid state. In the area surrounding these centers, solid formation occurs. Very small crystals begin to connect with each other in a random order, and a so-called polycrystal is obtained. Such a body is isotropic.

Characteristics of substances

What determines physical and mechanical characteristics tel? Atomic bonds are important, as is the type of crystal structure. Crystals ionic type characterized by ionic bonds, which means a smooth transition from one atom to another. In this case, the formation of positively and negatively charged particles occurs. Ionic bond we can watch on simple example- such characteristics are characteristic of various oxides and salts. Another feature of ionic crystals is low thermal conductivity, but its performance can increase noticeably when heated. At the nodes of the crystal lattice you can see various molecules that are distinguished by strong atomic bonds.

Many minerals that we find throughout nature have a crystalline structure. And the amorphous state of matter is also nature in pure form. Only in this case the body is something shapeless, but crystals can take the form of beautiful polyhedrons with flat edges, and also form new solid bodies of amazing beauty and purity.

What are crystals? Amorphous-crystalline structure

The shape of such bodies is constant for a particular compound. For example, beryl always looks like a hexagonal prism. Try a little experiment. Take a small cube-shaped crystal of table salt (ball) and put it in a special solution as saturated as possible with the same table salt. Over time, you will notice that this body has remained unchanged - it has again acquired the shape of a cube or ball, which is characteristic of table salt crystals.

3. - polyvinyl chloride, or the well-known plastic PVC windows. It is resistant to fires, as it is considered to be flame retardant, has increased mechanical strength and electrical insulating properties.

4. Polyamide is a substance with very high strength and wear resistance. It is characterized by high dielectric characteristics.

5. Plexiglas, or polymethyl methacrylate. We can use it in the field of electrical engineering or use it as a material for structures.

6. Fluoroplastic, or polytetrafluoroethylene, is a well-known dielectric that does not exhibit dissolution properties in solvents of organic origin. A wide temperature range and good dielectric properties allow it to be used as a hydrophobic or anti-friction material.

7. Polystyrene. This material is not affected by acids. It, like fluoroplastic and polyamide, can be considered a dielectric. Very durable against mechanical stress. Polystyrene is used everywhere. For example, it has proven itself well as a structural and electrical insulating material. Used in electrical and radio engineering.

8. Probably the most famous polymer for us is polyethylene. The material is resistant to exposure to aggressive environments; it is absolutely impermeable to moisture. If the packaging is made of polyethylene, there is no fear that the contents will deteriorate under the influence of heavy rain. Polyethylene is also a dielectric. Its application is extensive. It is used to make pipe structures, various electrical products, insulating film, casings for telephone and power line cables, parts for radios and other equipment.

9. Polyvinyl chloride is a high-polymer substance. It is synthetic and thermoplastic. It has a molecular structure that is asymmetrical. It is almost impervious to water and is made by pressing, stamping and molding. Polyvinyl chloride is most often used in the electrical industry. Based on it, various heat-insulating hoses and hoses for chemical protection, battery banks, insulating sleeves and gaskets, wires and cables are created. PVC is also an excellent replacement for harmful lead. It cannot be used as a high-frequency circuit in the form of a dielectric. And all because in this case the indicators dielectric losses will be high. Has high conductivity.