General Regulations on the details of the machines. Basic concepts about machine details

26.11.2019

As a result of the study of this section, the student must:

know

Methodical, regulatory and guidelines regarding the work performed;
Basics of designing technical objects;
Problems of creating machines of various types, drives, principle of operation, specifications;
constructive features developed and used technical means;
Sources of scientific and technical information (including Internet sites) on the design of parts, nodes, actuators and general-purpose machines;

be able to

apply the theoretical foundations for the implementation of work in the field of scientific and technical activities for design;
apply the methods of comprehensive technical and economic analysis in mechanical engineering for reasonable decision-making;
independently understand the normative methods of calculation and take them to solve the task;
choose structural materials for the manufacture of general details depending on the working conditions;
search and analyze scientific and technical information;

own

Skills of rationalization of professional activities in order to ensure safety and protection ambient;
discussion skills on professional topics;
terminology in the design of machine parts and general-purpose products;
skills search for information about the properties of structural materials;
information O. technical parameters Equipment for use when designing;
Skills of modeling, carrying out structural works and design transmission mechanisms taking into account matches with the terms of reference;
Skills of applying received information when designing machine parts and general products.

Studying the elementary base of engineering (parts of machines) - know the functional purpose, image (graphic representation), methods of design and verification calculations of the main elements and parts of the machines.

The study of the structure and methods of the design process is to have an idea of \u200b\u200bthe invariant concepts of the system design process, to know the stages and design methods. Including iterations, optimization. Obtaining practical design skills technical Systems (TC) from the field of mechanical engineering, independent work (with the help of a teacher - consultant) to create a mechanical device project.

Mechanical engineering is the basis of scientific and technological progress, the main production and technological processes are performed by machines or automatic lines. In connection with this mechanical engineering belongs to the leading role among other industries.

The use of machine parts is known with deep antiquity. Simple details of machines - metal tracks, primitive gears, screws, crank were known to Archimedes; Cable and belt, cargo screws, hinge clutches used.

Leonardo da Vinci, who is considered to be the first researcher in the field of machine parts, gear wheels were created with crossed axes, hinged chains, rolling bearings. The development of the theory and calculation of machine parts are associated with many names of Russian scientists - II. L. Chebyshev, N. P. Petrova, N. E. Zhukovsky, S. A. Chaplygin, V. L. Brick - Va (author of the first textbook (1881) for the details of machines); In the future, the course "Details of Machines" was developed in the works of P. K. Khudyakova, A. I. Sidorova, M. A. Savsrina, D. N. Retova, and others.

As an independent scientific discipline, the course "Details of Machines" took for 1780, at that time it was allocated from the general course of building machines. From foreign courses "Details of the machines", the works of K. Bach, F. Retzher were most widely used. Discipline "Details of machines" directly relies on the courses "Resistance of materials", "Theory of mechanisms and machines", "Engineering charts".

Basic concepts and definitions. "Machine details" is the first of the estimated design courses in which they study design Basics Machines and mechanisms. Any machine (mechanism) consists of parts.

Detail - Such a part of the car, which is manufactured without assembly operations. Details may be simple (nut, key, etc.) or complex ( crankshaft, gearbox body, machine bed, etc.). Details (partially or completely) are combined into nodes.

Knot Represents complete assembly unitconsisting of a number of parts having a general functional purpose (rolling bearing, coupling, gearbox, etc.). Complex nodes may include several simple nodes (subasters); For example, the gearbox includes bearings, shafts with gear wheels planted on them, etc.

Among the wide variety of parts and nodes of machines, there are those used in almost all machines (bolts, shafts, couplings, mechanical transmissions etc.). These details (knots) are called complete details And learn in the course "Details of Machines". All other details (pistons, turbine blades, rowing screws, etc.) belong to details special purpose And learn in special courses.

Details of general purpose are used in mechanical engineering in very large quantities, about a billion gears are produced annually. Therefore, any improvement of the methods of calculating and designing these parts, which makes it possible to reduce the cost of material, lower the cost of production, increase the durability, brings a large economic effect.

A car - device committing mechanical movements In order to convert energy, materials and information, for example, the engine internal combustion, rolling mill, lifting crane. EUM, strictly speaking, can not be called the machine, since it does not have parts performing mechanical movements.

Performance (GOST 27.002-89) nodes and parts of the machine - the state in which the ability to perform the specified functions within the parameters set by the regulatory and technical documentation

Reliability (GOST 27.002-89) - the property of the object (machines, mechanisms and parts) to perform the specified functions, keeping the values \u200b\u200bof the established indicators in the desired limits corresponding to the specified modes and conditions of use, maintenance, repair, storage and transportation.

Reliability - The property of the object continuously maintain performance for some time or some workers.

Refusal - This event consistent with the performance of the object.

During the refusal - Work time from one failure to another.

Failure intensity - Number of failures per unit time.

Durability - The property of the machine (mechanism, details) is maintained before the marginal state when installed system technical Services and repairs. The limit is understood as such a state of the object, when further operation becomes economically inappropriate or technically impossible (for example, repair is more expensive new car, Details or may cause emergency breakdown).

Maintainability - The property of the object, which consists in adaptability to the prevention and detection of the causes of failures and damage and eliminate their consequences in the process of repair and maintenance.

Persistence - Property of an object to maintain performance during and after storage or transportation.

Basic requirements for the design of machine parts. Perfection of the design details are evaluated by her reliability and economy. Under reliability, understand product property to save its performance. Efficiency determine the value of the material, the cost of production and operation.

The main criteria for the performance and calculation of machine parts are strength, rigidity, wear resistance, corrosion resistance, heat resistance, vibration resistance. The value of this or that criterion for this part depends on its functional purpose and working conditions. For example, for fastening screws, the main criterion is strength, and for driving screws - wear resistance. When designing parts, their performance is provided mainly by choosing the appropriate material, a rational structural form and the calculation of the size of the main criteria.

Features of calculating machine parts. In order to compile a mathematical description of the calculation object and, if possible, simply solve the task, in engineering calculations, real designs are replaced by idealized models or calculated schemes. For example, when calculating the strength substantially, the details are discontinuously considered non-solid and homogeneous material, ideas, loads, loads and the form of parts. Wherein the calculation becomes approximate. In the approximate calculations are of great importance right choice The calculated model, the ability to estimate the main and discard secondary factors.

Inaccuracies of strength calculations are compensated mainly due to strength reserves. Wherein the choice of coefficients of strength reserves becomes a very responsible stage of calculation. The understated value of the reserve of strength leads to the destruction of the part, and the overestimated - to the unjustified increase in the mass of the product and the overflow of the material. Factors affecting the margin of durability, numerous and diverse: the degree of responsibility of the part, the homogeneity of the material and the reliability of its tests, the accuracy of the calculated formulas and determining the calculated loads, the impact of the quality of technology, operating conditions, etc.

In engineering practice there are two types of calculation: project and verification. Project calculation - A preliminary, simplified calculation, performed in the design process of the part design (node) in order to determine its size and material. Verification calculation - Refined calculation of the known design, which is performed in order to verify its strength or determination of the load standards.

Estimated load. When calculating parts of machines, the calculated and nominal load is distinguished. Calculation load, such as torque T, Determine how the product of the nominal moment T P. On the dynamic coefficient of load mode K. T \u003d CT p.

Nominal moment T N. Corresponds to the passport (design) power of the machine. Coefficient TO Consides additional dynamic loads associated mainly with non-uniformity of movement, start and braking. The value of this coefficient depends on the type of engine, drive and working machine. If the mode of operation of the machine, its elastic characteristics and mass are known, the value TO You can determine the calculation. In other cases, the value TO Choose, focusing on the recommendation. Such recommendations are based on experimental research and experience of the various machines.

Choosing materials For parts of the machines is the responsible stage of design. Properly selected materialbig extent determines the quality of the part and the machine as a whole.

Selecting the material, take into account mainly the following factors: the compliance of the properties of the material the main criterion of health (strength, wear resistance, etc.); requirements for mass and dimensions of the part and the machine as a whole; Other requirements associated with the purpose of the part and the conditions of its operation (anticorrosive resistance, frictional properties, electrical insulating properties, etc.); Compliance of the technological properties of material of the structural form and the planned method of processing the part (stamp, weldability, casting properties, cutting processability, etc.); The cost and deficiency of the material.

Machine A device generated by a person performing mechanical movements for transformation of energy, materials and information in order to fully replace or facilitate the physical and mental labor of a person, an increase in its performance.

Under the materials are understood by processed items, moved goods, etc.

The machine characterizes the following signs:

energy transformation into mechanical work or transformation of mechanical work in another type of energy;

the definition of the movement of all its parts at a given movement of one part;

artificiality of origin as a result of human labor.

By the nature of the workflow, all cars can be divided into classes:

machines - engines. These are energy machines designed to convert the energy of any kind (electrical, thermal, etc.) into mechanical energy (solid);

machines - transducers - energy machines intended for transforming mechanical energy into energy of any kind (electric generators, air and hydraulic pumps etc.);

transport machines;

technological machines;

information machines.

All machines and mechanisms consist of parts, nodes, aggregates.

Detail - Part of the car manufactured from homogeneous material without the use of assembly operations.

Knot- The completed assembly unit, which consists of a number of connected parts. For example: Bearing, coupling.

Mechanismit is called an artificially created system of bodies, intended for converting the movement of one or more bodies to the required movements of other bodies.

Requirements for machines:

High performance;

2. Payback of the cost of design and manufacture;

3. High efficiency;

4. Reliability and durability;

5. Easy management and maintenance;

6. Transportability;

7. Small dimensions;

8. Security in work;

Reliability- This is the ability of the part to save its operational performance, execute the specified functions during the specified service life.

Requirements for machine details:

but) strength - resistance to the detail of the destruction or occurrence of plastic deformations during the warranty period of service;

b. ) rigidity - guaranteed degree of resistance to the elastic deformation of the part in the process of its operation;

in ) wear resistance - Details resistance: mechanical wear or corrosion-mechanical wear;

d) small dimensions and weight;

e) manufacture of inexpensive materials;

e) manufacturability (production should be carried out at the lowest work and time costs);

g) safety;

h) Compliance with state standards.

When calculating parts for strength, it is necessary to obtain such a voltage in a hazardous section, which will be less than or equal to admitted: Δ max ≤ [Δ]; τ max ≤ [τ]

Allowable voltage- This is the maximum working voltage that can be allowed in a hazardous section, subject to the necessary strength and durability of the part during its operation.

The allowable voltage is chosen depending on the limit voltage

;
n is a permissible strength factor that depends on the type of design, its responsibility, the nature of loads.

The stiffness of the part is checked by comparing the magnitude of the largest linear | or angular J moving with allowable: for linear | max £ [|]; For angular j max £ [j]

Machine parts (from Franz. Détail - detail)

elements of machines, each of which is one of the whole and cannot be disassembled without destruction to simpler, composite blocks of machines. D. M. is also a scientific discipline considering the theory, calculation and design of machines.

Number of parts B. sophisticated cars Reaches tens of thousands. Performing machines from parts is primarily caused by the need for relative movements of parts. However, the fixed and mutually fixed parts of the machines (links) are also made from separate connected parts. This allows you to use optimal materials, restore the working capacity of worn cars, replacing only simple and cheap items, facilitates their manufacture, provides the possibility and convenience of assembly.

D.M. As scientific discipline considers the following basic functional groups.

Cabinet parts ( fig. one ) carrying mechanisms and other machine nodes: plates that support machines consisting of separate units; Stanins carrying main nodes of machines; transport machines; corps of rotary machines (turbines, pumps, electric motors); cylinders and cylinder blocks; gearboxes, gearboxes; Tables, Salazki, Calipers, Consoles, Brackets, etc.

Transmission - mechanisms transmitting mechanical energy to the distance, as a rule, with the transformation of velocities and moments, sometimes with the transformation of species and movement laws. Transferring the rotational motion, in turn, divide on the principle of working on gearing transmission, working without slipping - gear transmissions (see gear transmission) ( fig. 2. , a, b), worm gears (see worm gear) ( fig. 2. , c) and chain, and transmission friction - belt transmissions (see belt transmission) and friction with rigid links. According to the presence of an intermediate flexible link, which ensures the possibility of significant distances between the shafts, distinguishes the transmissions of flexible bond (belt and chains) and the transmission by direct contact (gear, worm, friction, etc.). By the relative arrangement of shafts - transmissions with parallel axes of shafts (cylindrical gear, chain, beltented), with intersecting axes (conical gear), with crossed axes (worm, hypoid). According to the main kinematic characteristic - a transfer ratio - there are transmissions with a constant gear ratio (reduction, efficient) and with variable gear ratios - stepped (gearboxes (see. Transmission)) and stepless (variator s). Transmissions transforming rotational movement into a continuous translational or vice versa are separated by the transmission of screw - nut (sliding and rolling), Rake - Rack gear, Rake - Worm, Long Polgaika - Worm.

Shafts and axes ( fig. 3. ) Serve to maintain rotating D. M. Distinguish the gears, carrier gear parts - gear wheels, pulleys, stars, and shafts are indigenous and special, bearing, except for the gear parts, engineering engineers or machine guns. Axis, rotating and fixed, have been widely used in transport vehicles To maintain, for example, you are not interested in wheels. Rotating shafts or axes are based on the bearing and ( fig. four ), and progressively moving parts (tables, calipers, etc.) move along the guides (see the guides). Slip supports can work with hydrodynamic, aerodynamic, aerostatic friction or mixed friction. Rolling rolling structures are used for small and medium loads, roller - with significant loads, needle - with embarrassed dimensions. Most often in the machines are used rolling bearings, they are made in a wide range of external diameters from one mM. to several m. and weighing g. to several t..

Couplings serve for the shafts. (See Coupling) This feature can be combined with the compensation of manufacturing and assembly errors, mitigating dynamic impacts, control, etc.

Elastic elements are intended for vibration insulation and damping energy, to perform engine functions (for example, time springs), to create gaps and tights in the mechanisms. Split twisted springs, spiral springs, leaf springs, rubber elastic elements, etc.

Connecting parts are a separate functional group. Distinguish: indefinite compounds (see an indefinite compound) that do not allow disconnection without the destruction of parts, connecting elements or a connecting layer - welded ( fig. five , but), soldering, crossed ( fig. five , b), glue ( fig. five , c), rolled; Connecting compounds (see the terminal compound), allowing separation and carried out by the mutual direction of parts and friction forces (most of the connector compounds) or only with a mutual direction (for example, the compounds of prismatic key). At the form of connecting surfaces, compounds on planes (most) and on the surfaces of rotation - cylindrical or conical (shaft - hub) are distinguished. Welded joints are welded in mechanical engineering. Threaded compounds carried out by screws, bolts, heels, nuts ( fig. five , d).

The prototypes of many D. m. Known with deep antiquity, the earliest of them are lever and wedge. More than 25 thousand years ago, a person began to apply a spring in bows for throwing arrows. The first transmission of flexible bond was used in an ampace drive to mining fire. Rollers whose work is based on rolling friction, more than 4,000 years ago were known. To the first details approaching under the working conditions to modern, the wheel, axis and bearing in wagons. In antiquity and during the construction of temples and pyramids, the gates of Ami and block Ami were used. Plato and Aristotle (4th century BC. Er) mention in its writings about metal pinges, gears, cranks, rims, polystes. Archimeda applied the screw in the water-made machine, apparently known and previously. In the notes, Leonardo da Vinci describes the screw gear wheels, gear wheels with rotating vegetables, rolling bearings and hinged chains. In the literature of the Renaissance, there are information about the belt and cable broadcasts, cargo screws, couplings. Designs D. M. Improved, new modifications appeared. In late 18 - early 19th centuries. Wide distribution received ripple compounds in boilers, structures J.-D. Bridges, etc. In the 20th century Close compounds gradually supplemented welded. In 1841, the Avenger in England was developed a system of fastening threads, which was the first work on standardization in mechanical engineering. The use of transfers with flexible bond (belt and cable) was caused by the distribution of energy from steaming On the floors of the factory, with transmissions drive, etc. With the development of individual electric drive, belt and cable transfer began to use for energy transmission from electric motors and primary engines in the drives of light and medium-sized machines. In the 20s 20 V. Clinoremated transfers spread widely. Further development of flexible bonding transmissions are multi-world and gear belts. The gears were continuously improved: the recovery engagement and the engagement of the straightforward profile with roundings was replaced with cycloidal, and then evolvent. An essential stage was the appearance of the circlent engagement M. L. Novikova. Since the 70s 19 V. Rolling bearings began to be widely used. Significant propagation was obtained by hydrostatic bearings and guides, as well as bearings with air lubrication.

Materials D. M. To a large extent, determine the quality of the machines and make up a significant part of their cost (for example, in cars up to 65-70%). The main materials for D. M. are steel, cast iron and colored alloys. Plastic masses are used as electrically insulating, antifriction and friction, corrosion-resistant, heat-insulating, high-strength (fiberglass), as well as both possessing good technological properties. Rubber are used as materials with high elasticity and wear resistance. Responsible D. M. (Camcolted wheels, highly tense shafts, etc.) are performed from hardened or improved steel. For D. M., the dimensions of which are determined by the conditions of rigidity, use materials that make the manufacture of parts made of perfect forms, such as non-uncrowded steel and cast iron. D. M., working at high temperaturesah, performed from heat-resistant or heat-resistant alloys. On the surface of D. M. The largest rated voltages from bending and twist, local and contact voltages are valid, and the wear is also covered, so D. M. Surface hardening: chemical-thermal, thermal, mechanical, thermal-mechanical processing.

D.M. MUST with a given probability to be operational over a certain period of service with the minimum necessary value of their manufacture and operation. To do this, they must satisfy the criteria of performance: strength, rigidity, wear resistance, heat resistance, etc. Calculations on the strength of D. M., experiencing variable loads, can be conducted on rated voltages, in terms of safety reserves, taking into account the concentration of stresses and a large-scale factor or taking into account Mode variability. The most reasonable can be considered the calculation for a given probability and trouble-free operation. Calculation of D. M. The hardness is usually carried out from the condition of satisfactory work of the conjugate parts (the absence of increased edge pressures) and the working capacity of the machine, such as obtaining accurate products on the machine. To ensure wear resistance, they seek to create conditions for liquid friction, in which the thickness of the oil layer should exceed the sum of the heights of the micronether and others. Deviations from the correct geometric shape of the surfaces. If it is impossible to create liquid friction, pressure and speed limit to the established practice or calculates wear on the basis of a similarity on operational data for nodes or machines of the same destination. Calculations of D. M. Develop in the following directions: settlement optimization of structures, development of calculations for computers, the introduction of the time factor, the introduction of probabilistic methods, standardization of calculations, the use of table calculations for D. centralized manufacturing. The basics of the formation of the calculation of D. M. were laid by research in the field of engagement theory (L. Euler, X. I. Gokhman), the theory of friction of threads on the drums (L. Euler et al.), Hydrodynamic lubrication theory (N. P. Petrov, O. Reynolds, N. E. Zhukovsky, etc.). Research in the field of D. m. The USSR is held at the Institute of Machinery, Research Institute of Mechanical Engineering Technology, MVTU. Bauman and others. The main periodic body, which publishes materials on the settlement, design, applying D. M., is the "Bulletin of Mechanical Engineering".

Development of design D. M. occurs in the following directions: increasing the parameters and development of D. M. High Parameters, the use of optimal features of mechanical with solid links, hydraulic, electrical, electronic and other devices, Design D. m. For a period to moral aging Machines, increase in reliability, optimization of forms due to new technology capabilities, ensuring perfect friction (liquid, gas, rolling), sealing of conjugates D. M., Performing D. M., working in an abrasive medium, from materials, the hardness of which is higher than hardness abrasive, standardization and organization of centralized manufacturing.

LIT: Machine parts. Atlas of structures, ed. D. N. Reshettova, 3 ed., M., 1968; Machine parts. Directory, t. 1-3, M., 1968-69.

D. N. Reshetov.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

Watch what is "Details of Machines" in other dictionaries:

The combination of structural elements and their combinations, which is the basis of the machine design. Detail of the car is called such a part of the mechanism that is manufactured without assembly operations. Machine details are also scientific and ... Wikipedia

machine parts - - Topics Oil and gas industry En Machine Components ... Technical translator directory

1) Dep. Composite parts and their simplest connections in machines, devices, devices, devices, etc.: Bolts, rivets, shafts, gears, swords, etc. 2) Scientific. Discipline, including theory, calculation and design ... Big Encyclopedic Polytechnic Dictionary

This term has other values, see the key. Installation of the key in the groove of the sword shaft (from Polish. Szponka, through it. Spon, Span Slice, Wedge, Lining) Detail of machines and mechanisms of the oblong shape, inserted into the groove ... ... Wikipedia

The development of modern society is different from the ancient the fact that people invented and learned to enjoy all sorts of machines. Now even in the most distant villages and the most backward tribes enjoy the fruits of technical progress. Our whole life is accompanied by the use of technology.

In the process of the development of society, as the mechanization of production and transport, an increase in the complexity of structures, there was a need not only unconsciously, but also scientifically approach the production and operation of machines.

From the middle of the XIX century in the Universities of the West, and a little later, an independent course "Machine details" is introduced a little later in the University of St. Petersburg. Today without this course is unthinkable, the preparation of the mechanic engineer of any specialty.

The process of training engineers worldwide has a single structure:

In the first courses, fundamental sciences are introduced, which give knowledge about the general laws and principles of our world: physics, chemistry, mathematics, computer science, theoretical mechanics, philosophy, political science, psychology, economy, history, etc.
Applied sciences, which explain the effect of fundamental laws of nature in private spheres of life. For example, technical thermodynamics, strength theory, materials science, material resistance, computing equipment, etc.
Starting from the 3rd year, students proceed to the study of general technical sciences, such as "Machine details", "Fundamentals of standardization", "Material processing technology", etc.
At the end, special disciplines are introduced when the engineer's qualifications are determined in the appropriate specialty.

Educational discipline "Machine details" aims to study students with students and mechanisms of instruments and installations; physical principles of instrument, physical installations and technological equipment used in the nuclear industry; Methods and design calculations, as well as methods for designing design documentation. In order to be prepared for the comprehension of this discipline, it is necessary to own basic knowledge, which are taught in the courses "physics of strength and resistance of materials", "Basics of Materials", "Engineering Graphics", "Informatics and Information Technologies".

The subject "Machine details" is mandatory and main for courses, where the course project and thesis design is expected.

Details of machines as scientific discipline considers the following basic functional groups.

Cabinet parts, carrying mechanisms and other machine nodes: Plates that support machines consisting of individual units; Stanins carrying main nodes of machines; transport machines; corps of rotary machines (turbines, pumps, electric motors); cylinders and cylinder blocks; gearboxes, gearboxes; Tables, Salazki, Calipers, Consoles, Brackets, etc.
Transmission - mechanisms transmitting mechanical energy to the distance, as a rule, with the transformation of velocities and moments, sometimes with the transformation of species and movement laws. The transfers of the rotational movement, in turn, divide on the principle of carrying out the gearing transmission, working without slippage - gears, worm gears and chains, and friction transmission - belt transfers and friction with rigid links. According to the presence of an intermediate flexible link, which ensures the possibility of significant distances between the shafts, distinguishes the transmissions of flexible bond (belt and chains) and the transmission by direct contact (gear, worm, friction, etc.). By the relative arrangement of shafts - transmissions with parallel axes of shafts (cylindrical gear, chain, beltented), with intersecting axes (conical gear), with crossed axes (worm, hypoid). According to the main kinematic characteristic - a gear ratio - there are transmissions with a constant gear ratio (reduction, rising) and with a variable gear ratio - stepped (transmissions) and stepless (variators). Transmissions transforming rotational movement into a continuous translational or vice versa are separated by the transmission of screw - nut (sliding and rolling), Rake - Rack gear, Rake - Worm, Long Polgaika - Worm.
Shafts and axles serve to maintain rotating machine parts. The transmissions are distinguished, carrying output parts - gear wheels, pulleys, stars, and shafts are indigenous and special, bearing, except for gear parts, engineering engineers or machine guns. Axis, rotating and fixed, has been widely used in transport vehicles to maintain, for example, native wheels. Rotating shafts or axes are based on bearings, and progressively moving parts (tables, calipers, etc.) move along the guides. Most often, rolling bearings are used in the machines, they are made in a wide range of outer diameters from one millimeter to several meters and weighing a fraction of grams to several tons.
Couplings serve for the shafts. This feature can be combined with compensation of manufacturing and assembly errors, mitigating dynamic impacts, control, etc.
Elastic elements are intended for vibration insulation and damping energy, to perform engine functions (for example, time springs), to create gaps and tights in the mechanisms. Split twisted springs, spiral springs, leaf springs, rubber elastic elements, etc.
Connecting parts are a separate functional group. Distinguish: the indefinite compounds that do not allow separation without the destruction of parts, the connecting elements or the coupling layer are welded, soldering, rigging, adhesive, rolled; Conclusion compounds that allow disconnection and carried out by the mutual direction of parts and friction forces or only a mutual direction. In the form of connecting surfaces, compounds on planes and on the surfaces of rotation - cylindrical or conical (shaft-hub) are distinguished. Welded joints are welded in mechanical engineering. Threaded compounds carried out with screws, bolts, heels, nuts obtained the greatest propagation of the most propagation.

So, "details of the machines" - a course in which the framework of the design of machines and mechanisms is studying.

What are the stages of the design of the structure of the device, instrument, installation?

First, a design task is set, which is the source document for developing a device, a device or installation, which indicates:

a) appointment and area of \u200b\u200bproduct use; b) operating conditions; c) technical requirements; d) stages of development; e) production type and other.

The technical task may have an application containing drawings, sketches, schemes and other necessary documents.

Part technical requirements Includes: a) destination indicators that determine the target use and application of the device (measurement range, effort, power, pressure, sensitivity, etc.; b) the composition of the device and design requirements (dimensions, mass, use of modules, etc.; c) Requirements to the means of protection (from ionizing radiation, high temperatures, electromagnetic fields, moisture, aggressive medium, etc.), interchangeability and reliability, technologicality and metrological support; d) aesthetic and ergonomic requirements; e) additional requirements.

The regulatory framework of the design includes: a) unified system design documentation; b) a unified system of technological documentation c) State Standard of the Russian Federation on the system of development and production of products for the production of SRPP - GOST R 15.000 - 94, GOST R 15.011 - 96. SRPP

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Vocational school №22.

Abstract on discipline

"Technical Mechanics"

on the topic: "Machine details: the concept and their characteristic"

Performed: Svetlana Rozhko

Saratov-2010 g

Basic definitions and concepts

The item is a product obtained from a homogeneous material on a material without assembly operations.

Assembly unit - the product obtained using assembly operations.

The mechanism is a complex of details and assembly unitscreated in order to perform a certain type of driving unit movement with a predetermined leading movement.

The machine is a set of mechanisms created in order to turn one type of energy into another, or to make useful work, in order to facilitate human labor.

Mechanical transmissions.

Transmissions are mechanisms intended for movement.

1. According to the method of moving movement:

a) engage (gear, worm, chain);

b) friction (frictional);

2. By way of contact:

a) direct touch (Zubv., Worm., Fricz.);

b) using a gear ratio.

The toothed - consists of a gear and gear and is designed to transmit rotation.

Advantages: reliability and strength, compactness.

Disadvantages: noise, high requirements for the accuracy of manufacture and installation, depressions - voltage concentrators.

Classification.

1. Cylinder (axis 11), conical (axis crossed.), Screw (axis cross).

2. By profile of the tooth:

a) evolvent;

b) cycloidal;

c) with the engagement Novikova.

3. By way of engagement:

a) internal;

b) external.

4. By the location of the teeth:

a) styling;

b) ososophy;

c) Mampnaya.

5. By design:

a) open;

b) closed.

Used in cars cars, clock.

The worm gear consists of a worm and a worm wheel whose axes are cross. Serves to transmit rotation wheel.

Advantages: reliability and strength, the ability to create self-blocking, compactness, smoothness and silent operation, the possibility of creating large peeled numbers.

Disadvantages: low-rise, large heating of the transmission, the use of expensive antifriction materials.

Classification.

1. Output worm:

a) cylindrical;

b) global.

2. For a tooth profile Worm:

a) evolvent;

b) carpurals;

c) Archimedes.

3. By number of goals:

a) once an expense;

b) multisope.

4. In relation to the worm to the worm wheel:

a) with the bottom;

b) with the top;

c) with side.

Used in machines, lifting devices.

Belt transmission consists of pulleys and belt. It serves to transmit rotation to a distance of up to 15 meters.

Advantages: smoothness and sacchability of work, simplicity of design, the possibility of smooth regulation of the betrayal number.

Disadvantages: strap slip, limited belt service, the need for tension devices, the impossibility of use in explosive media.

It is used in convekers, drives of machine tools, in the textile industry, in sewing machines.

Instrument making.

Belts - leather, rubber.

Pulleys - cast iron, aluminum, steel.

The chain transmission consists of a chain and gear. It serves to transfer the rotational torque to a distance of up to 8 meters.

Advantages: reliability and strength, lack of slippage, less pressure on shafts and bearings.

Disadvantages: noise, big wear, sagging, lubricant is difficult.

Material - steel.

Classification.

1. By appointment:

a) freight,

b) stretch,

c) traction.

2. By design:

a) roller,

b) sleeve,

c) gear.

Apply in bicycles, drives of machine tools and cars, conveyors.

Shafts and axles.

The shaft is a detail designed to maintain other parts in order to transfer the rotational torque.

During operation, the shaft is experiencing bending and twist.

The axis is the item intended only to maintain on it of similar details, during operation the axis is experiencing only bend.

Classification of shafts.

1. By appointment:

a) straight,

b) crankshafts

c) flexible.

2. in form:

a) smooth,

b) stepped.

3. By section:

a) solid,

Elements of the shaft. Shafts are often made of steel-20, steel 20x.

Calculation of shafts: kr \u003d | Mmax | \\ w<=[ кр] и=|Mmax|W<=[ и] Оси только на изгиб. W - момент сопротивления сечения [м3].

Couplings are devices designed to connect shafts for the purpose of transmitting the rotational torque and to stop the node without turning off the engine, as well as the preventing operation of the mechanism during overloads.

Classification.

1. Unpainted:

a) rigid,

b) flexible.

Advantages: simplicity of structures, low cost, reliability.

Disadvantages: can connect shafts of the same diameters.

Material: Steel-45, Gray cast iron.

2. Managed:

a) gear,

b) friction.

Advantages: simplicity of design, different shafts, it is possible to disable the mechanism when overloading.

3. Self-:

a) safety,

b) overtaking,

c) centrifugal.

Advantages: Reliability in the work, transmit rotation when a certain rotational speed is reached due to the inertia forces.

Disadvantages: the complexity of the design, the big wear of the cams.

Performed from gray cast iron.

4. Combined.

Couplings are selected on the GOST table.

Independent connections

Extcast connections are such parts compounds that cannot be disassembled without the destruction of parts included in this compound.

These include: ripple, welded, soldering, adhesive connections.

Close connections.

Close connections:

1. By appointment:

a) durable

b) dense.

2. By location of the ripples:

a) parallel,

b) in a checker order.

3. By number of goals:

a) single-row

b) multi-row.

Advantages: well withstand shock loads, reliability and strength, ensure visual contact for the quality of the seam.

Disadvantages: Holes - voltage hubs and reduce the strength, take the construction, noisy production.

Welding connections

Welding is the process of connecting parts by heating to the melting point or plastic deformation in order to create an indefinite compound.

a) gas,

b) electrode,

c) contact,

d) laser,

e) cold,

e) explosion welding.

Welded connections:

a) angular,

b) butt,

c) fattest

d) brand,

d) point.

Advantages: Provides a reliable hermetic compound, the possibility of connecting any materials of any thickness, the sacchability of the process.

Disadvantages: Changing the physical and chemical properties in the seam area, the blocking of the part, the complexity of the seam quality check, requires highly qualified specialists, poorly withstand the loads of the load, seam - voltage concentrator.

Adhesive connections.

Advantages: Does not take up the design, low cost, does not require specialists, the ability to connect any details of any thickness, sacchability of the process.

Disadvantages: "aging" glue, low heat resistance, the need for pre-stripping surface.

All the indefinted compounds are calculated on the cut.

TSR \u003d Q \\ a<=[Тср].

Threads (classification)

1. By appointment:

a) fasteners,

b) running,

c) sealing.

2. Angle at the top:

a) metric (60),

b) inch (55).

3. By profile:

a) triangular,

b) trapezdal

c) stubborn,

d) round,

d) rectangular.

4. By number of goals:

a) the one-income,

b) multi-day.

5. In the direction of the screw line:

a) left, detail mechanism is an indefinite connection

b) right.

6. On the surface:

a) external

b) internal,

c) cylindrical,

d) conical.

Threaded surfaces can be performed:

a) manually

b) on the machines,

c) on automatic machines rolling.

Advantages: simplicity of design, reliability and durability, standardization and interchangeability, low cost, does not require specialists, the possibility of connecting any materials.

Disadvantages: Thread - voltage concentrator, wear of contacting surfaces. Material - steel, colored alloys, plastic.

Sponge compounds.

The swords are: prismatic, segment, wedges.

Advantages: Simplicity of design, reliability in work, long swords - guides.

Disadvantages: Sponge groove - voltage concentrator.

Slotches.

There are: straight, triangular, evolvent.

Advantages: Reliability in the work, uniform distribution throughout the shaft cross section.

Disadvantages: the complexity of manufacture.

R \u003d SQR (X ^ 2 + Y ^ 2) - for fixed supports,

by x - COS of this angle

on y - sin of this angle or cos (90-angle)