A machine is a device designed to convert energy, materials and information. Depending on the main purpose, there are three types of machines: energy, information and workers.
Power machines designed to convert any type of energy into mechanical energy are called motor machines. Power machines include, for example, electric motors, motors internal combustion, turbines, steam engines. Information machines are designed to convert information (calculators, computers, etc.).
Working machines are divided into two groups: technological and transport. transform processed products (which can be in a solid, liquid and gaseous state), changing its shape, properties, state and position. In transport vehicles, a product is understood as a moving object, and its transformation consists only in a change in position. TO transport vehicles include cars, loaders, conveyors, elevators, hoists, etc.
Technological, designed to perform certain technological operations for the processing of various products, is divided into special working machines, apparatus and devices.
A working machine is considered to be a device that rationally carries out technological operations as a result of the movement of working bodies, which maximally replace the operator’s labor with machine labor. At the same time, an increase in labor productivity and a reduction in the cost of manufactured products are achieved.
An apparatus is a machine in which thermal, chemical, biochemical, electrical and other processes take place, and for their implementation and intensification, as well as for the transportation of processed products, various devices are used that produce mixing, heating, cooling, etc.
The design of machines and devices is made up of parts, assemblies, mechanisms. A part is a product made of a material that is homogeneous in name and brand without the use of assembly operations. A collection of one or more fixedly connected parts is called a node. A system of nodes in which the movement of one or more leading nodes causes the movement of the others is called a mechanism. The set of mechanisms forms a machine. To control the regime, machines and devices are equipped with instrumentation, control, signaling, automation and control devices.
A modern machine consists mainly of power devices, actuators with working elements, a drive mechanism, as well as control, regulation, protection and blocking devices.
The feeding device is designed for continuous or periodic supply of initial products or raw materials to the machine with the possibility of dosing them by weight or volume, depending on the requirements of the technological process.
The actuator is designed to transfer movement to the working bodies of the machine. This mechanism includes a slave link, which is connected to the working bodies, and a leading link, which is connected to drive mechanism. The working bodies of the machine directly affect the processed product according to the given technological process. In some cases technological process in the machine is carried out by several working bodies, each of which performs a specific operation. Such machines are called complex, in contrast to simple machines with one working body.
Modern catering machines are driven mainly by individual electric motors, but a number of machines are designed to operate from universal drives.
Control devices carry out the start and stop of the machine, as well as control over its operation. Control mechanisms ensure the specified mode of operation of the machine, and protection and blocking mechanisms are used to prevent improper switching on of machines and prevent industrial injuries.
MACHINES AND MECHANISMS
mechanical devices that facilitate labor and increase its productivity. Machines can be varying degrees complexity - from a simple one-wheeled wheelbarrow to elevators, cars, printing, textile, computers. Energy machines convert one form of energy into another. For example, hydroelectric generators convert the mechanical energy of falling water into electrical energy. The internal combustion engine converts the chemical energy of gasoline into heat and then into mechanical energy of the car.
(see also
ELECTROMECHANICAL GENERATORS AND ELECTRIC MOTORS;
THERMAL ENGINE;
TURBINE).
The so-called working machines transform the properties or state of materials (metal-cutting machines, transport machines) or information (computers). Machines consist of mechanisms (motor, transmission and executive) - multi-link devices that transmit and transform force and movement. A simple mechanism called a chain hoist
(see. BLOCKS AND POLESPATS),
increases the force applied to the load, and thereby allows you to manually lift heavy objects. Other mechanisms make work easier by increasing speed. Thus, a bicycle chain engaging with an asterisk converts slow pedaling into fast rotation. rear wheel. However, mechanisms that increase speed do so by decreasing force, while those that increase force do so by decreasing speed. It is impossible to increase both speed and strength at the same time. Mechanisms can also simply change the direction of the force. An example is a block at the end of a flagpole: to raise the flag, the cord is pulled down. A change in direction may be combined with an increase in strength or speed. So, a heavy load can be lifted by pushing the lever down.
BASIC PRINCIPLES OF OPERATION OF MACHINES AND MECHANISMS
The basic Law. Although the mechanisms allow you to get a gain in strength or speed, the possibilities of such a gain are limited by the law of conservation of energy. As applied to machines and mechanisms, it says: energy can neither arise nor disappear, it can only be converted into other types of energy or into work. Therefore, the output of a machine or mechanism cannot be more energy than the input. Moreover, in real machines some of the energy is lost due to friction. Since work can be converted into energy and vice versa, the law of conservation of energy for machines and mechanisms can be written as Input Work = Output Work + Friction Losses. This shows, in particular, why a machine of the type perpetual motion machine: due to the inevitable loss of energy due to friction, it will stop sooner or later.
Gains in strength or speed. Mechanisms, as mentioned above, can be used to increase strength or speed. The ideal or theoretical gain in force or speed is the rate of increase in force or speed that would be possible in the absence of energy loss due to friction. The ideal gain is unattainable in practice. The real gain, for example in force, is equal to the ratio of the force (called load) that the mechanism develops to the force (called force) that is applied to the mechanism.
mechanical efficiency. Useful
The action of the machine is called the percentage ratio of the work at its output to the work at its input. For a mechanism, the efficiency is equal to the ratio of the real gain to the ideal one. Lever efficiency can be very high - up to 90% or even more. At the same time, the efficiency of the chain hoist due to significant friction and the mass of moving parts usually does not exceed 50%. The efficiency of the jack can be only 25% due to the large contact area between the screw and its body, and therefore high friction. This is approximately the same efficiency as car engine. See CAR PASSENGER. Efficiency can be increased within certain limits by reducing friction due to lubrication and the use of rolling bearings. See also LUBRICATION.
SIMPLE MECHANISMS
The simplest mechanisms can be found in almost any more complex machines and mechanisms. There are six of them: lever, block, differential gate, inclined plane, wedge and screw. Some authorities argue that in fact we can talk about only two simple mechanisms - a lever and an inclined plane - since it is easy to show that the block and gate are variants of the lever, and the wedge and screw are variants of the inclined plane.
Lever arm. It is a rigid rod that can rotate freely about a fixed point called the fulcrum. An example of a lever is a crowbar, a split hammer, a wheelbarrow, a broom. There are three types of levers, differing in the mutual arrangement of the points of application of the load and effort and the fulcrum (Fig. 1). The ideal gain in leverage is equal to the ratio of the distance DE from the force application point to the fulcrum to the distance DL from the load application point to the fulcrum. For a lever of the first kind, the distance DE is usually greater than DL, and therefore perfect win in strength is greater than 1. For a lever of the second kind, the ideal gain in strength is also greater than one. As for the lever of the third kind, then the value of DE for it is less than DL, and therefore, the gain in speed is greater than one.
Block. This is a wheel with a groove around the circumference for a rope or chain. Blocks are used in lifting devices. The system of blocks and cables, designed to increase the carrying capacity, is called a chain hoist. A single block can be either with a fixed axle (levelling) or movable (Fig. 2). A block with a fixed axle acts as a Class I lever with a fulcrum on its axle. Since the force arm is equal to the load arm (block radius), the ideal gain in strength and speed is 1. The movable block, on the other hand, acts as a type II lever, since the load is located between the fulcrum and the force. The load arm (block radius) is half the force arm (block diameter). Therefore, for a moving block, the ideal gain in strength is 2.
An easier way to determine the ideal gain in force for a block or system of blocks is by the number of parallel ends of the rope holding the load, as is easy to figure out by looking at fig. 2. Leveling and moving blocks can be combined in different ways to increase the gain in strength. Two, three or more blocks can be installed in one cage, and the end of the cable can be attached to either a fixed or a movable cage.
Differential gate. These are, in essence, two wheels connected together and rotating around the same axis (Fig. 3), for example, a well gate with a handle.
The differential gate can give a gain in both strength and speed. It depends on where the force is applied and where the load is, since it acts as a type I lever. The fulcrum is located on a fixed (fixed) axle, and therefore the arms of force and load are equal to the radii of the corresponding wheels. An example of such a device for gaining strength is a screwdriver, and for gaining speed, a grinding wheel.
Gear wheels. The system of two gears in mesh, sitting on shafts of the same diameter (Fig. 4), is somewhat similar to a differential gate (see also GEAR). The speed of rotation of the wheels is inversely proportional to their diameter. If the small drive gear A (to which the force is applied) is half the diameter of the large gear B, then it should rotate twice as fast. Thus, the gain in strength is gear train is equal to 2. But if the points of application of force and load are interchanged, so that wheel B becomes the driver, then the gain in strength will be 1/2, and the gain in speed will be 2.
Inclined plane. An inclined plane is used to move heavy objects for more high level without directly lifting them. Such devices include ramps, escalators, conventional stairs, and conveyors (with rollers to reduce friction). The ideal gain in force provided by an inclined plane (Fig. 5) is equal to the ratio of the distance over which the load moves to the distance traveled by the point of application of the force. The first is the length of the inclined plane, and the second is the height to which the load is raised. Since the hypotenuse is longer than the leg, the inclined plane always gives a gain in strength. The gain is greater, the smaller the slope of the plane. This explains the fact that mountain automobile and railways have the appearance of a serpentine: the less the steepness of the road, the easier it is to climb it.
Wedge. This is, in essence, a double inclined plane (Fig. 6). Its main difference from the inclined plane is that it is usually stationary, and the load moves along it under the action of force, and the wedge is driven under the load or into the load. The principle of the wedge is used in such tools and implements as an ax, a chisel, a knife, a nail, a sewing needle.
The ideal gain in strength given by the wedge is equal to the ratio of its length to the thickness at the blunt end. The real payoff of the wedge, unlike other simple mechanisms, is difficult to determine. The resistance he encounters varies unpredictably for different parts of his "cheeks". Due to the high friction, its efficiency is so small that the ideal gain does not matter much.
Screw. The thread of a screw (Fig. 7) is, in essence, an inclined plane repeatedly wrapped around a cylinder. Depending on the ascending direction of the inclined plane, the screw thread can be left hand (A) or right hand (B). The mating part, of course, must have a thread in the same direction. Examples simple devices with a screw thread - a jack, a bolt with a nut, a micrometer, a vice.
Since the thread is an inclined plane, it always gives a gain in strength. The ideal gain is equal to the ratio of the distance traveled by the point of application of force per revolution of the screw (circumference) to the distance traveled by the load along the screw axis. In one revolution, the load moves the distance between two adjacent threads (a and b or b and c in Fig. 7), which is called the thread pitch. The thread pitch is usually much smaller than its diameter, since otherwise the friction is too great.
COMBINED MECHANISMS
The combined mechanism consists of two or more simple ones. This is not necessarily a complex device; many fairly simple mechanisms can also be considered combined. For example, in a meat grinder there is a gate (handle), a screw (pushing meat) and a wedge (knife-cutter). Wrist watch hands are rotated by a system of gears of different diameters, meshing with each other. One of the most famous simple combined mechanisms is a jack. The jack (fig. 8) is a combination of a screw and a collar. The head of the screw supports the load, while the other end enters the threaded support. The force is applied to the handle fixed in the head of the screw. Thus, the force distance is equal to the length of the circle described by the end of the handle. The circumference of a circle is given by 2pr, where p = 3.14159 and r is the radius of the circle, i.e. V this case handle length. Obviously, the longer the handle, the greater the ideal power gain. The distance traveled by the load in one turn of the handle is equal to the thread pitch. Ideally, a very large gain in strength can be obtained if a long handle is combined with a small thread pitch. Therefore, despite the low efficiency of the jack (about 25%), it gives a big real gain in strength.
The gain in power created by the combined mechanism is equal to the product of the gains of the individual mechanisms included in its composition. So, the ideal gain in strength (IVS) for a jack is equal to the ratio of the circumference described by the handle to the thread pitch. For the gate included in the jack, the IVS is equal to the ratio of the circumference described by the handle (force distance) to the circumference of the screw (load distance). For a jack screw, IVS is equal to the ratio of the screw circumference (force distance) to the screw thread pitch (load distance). Multiplying the IVS of the individual mechanisms of the jack, we get for the combined mechanism IVS = (Handle circumference / Screw circumference) * (Screw circumference / Thread pitch) = (Handle circumference / Thread pitch). For more complex combined mechanisms, it is more difficult to calculate the IVS. Therefore, they usually indicate only real winnings.
see also
CAM GEAR ;
DYNAMICS ;
METAL-CUTTING MACHINES;
MECHANICS .
LITERATURE
Popov S.A. Course design on the theory of mechanisms and machines. M., 1986
Collier Encyclopedia. - Open Society. 2000 .
See what "MACHINES AND MECHANISMS" are in other dictionaries:
- "Machines and Mechanisms" Specialization: popular science Periodicity: monthly Abbreviated name: MM Language: Russian Editorial address: 197110, Saint Petersburg, st. Bolshaya Raznochinnaya 28 ... Wikipedia
Machines and mechanisms used during installation.- 8. Machines and mechanisms used during installation. Truck-mounted crane 10 t and crawler crane g.p. up to 100 tons Vehicles for transportation of packaged delivery units to the place of installation 5 t, crawler tractors ... ...
GOST 12.2.106-85: Occupational safety standards system. Machines and mechanisms used in the development of ore, non-metallic and alluvial mineral deposits. General hygiene requirements and assessment methods- Terminology GOST 12.2.106 85: System of labor safety standards. Machines and mechanisms used in the development of ore, non-metallic and alluvial mineral deposits. General hygiene requirements and assessment methods original document ... Dictionary-reference book of terms of normative and technical documentation
cars- 3.26 machinery executive mechanisms, power circuits and control circuits, etc., combined ... ... Dictionary-reference book of terms of normative and technical documentation
Loading and unloading machines- - the main purpose of these machines and mechanisms is to work on the movement of various goods. They are usually self-propelled universal machines based, as a rule, wheeled Vehicle. They also use quick-detachable workers ... ...
Lifting machines- - cranes of all types, excavator cranes (excavators designed to work with a hook suspended on a rope), hoists, winches for lifting loads and people. [Safety regulations for the operation of heat-consuming installations and thermal ... ... Encyclopedia of terms, definitions and explanations of building materials
Aggregate loosening machines- - devices and mechanisms designed to restore the flowability of frozen aggregates during their unloading; According to the principle of action, they are divided into vibration and vibro-impact. [Terminological dictionary for concrete and reinforced concrete. Federal State Unitary Enterprise "Research Center ... ... Encyclopedia of terms, definitions and explanations of building materials
Unloading machines- - designed for unloading aggregates from gondola cars and platforms (unloading from gondola cars is carried out by a multi-bucket elevator, from platforms by a pusher; supply to a stack, silos by belt conveyors). [Terminological dictionary… … Encyclopedia of terms, definitions and explanations of building materials
Engine- an energy machine that converts any energy into mechanical work. The main type of power plant in transport is a heat engine - a complex technical system that converts heat into mechanical work.
On domestic cars installed piston engines internal combustion. These engines are classified according to the following main features:
1. According to the method of ignition combustible mixture: compression ignition engines (diesels) and spark (forced) ignition engines (gasoline and gas).
2. According to the method of mixture formation: engines with external mixture formation (gasoline and gas) and with internal mixture formation (diesel engines).
3. By type of power control: motors with quantitative and motors with qualitative power control. With quantitative regulation, the power is changed by the throttle valve due to the amount of air-fuel mixture entering the cylinder, and with qualitative regulation, by varying the amount of injected fuel with a constant amount of air (by varying the composition of the mixture).
4. According to the method of implementation of the working process: four-stroke and two-stroke engines.
5. By type of fuel used: liquid fuel engines running on gasoline and diesel fuel, and gaseous fuel engines operating on compressed or liquefied gas.
6. According to the number of cylinders: single-cylinder and multi-cylinder engines (two-, four-, six-cylinder, etc.).
7. According to the location of the cylinders: single-row, or linear, engines (the cylinders are arranged in one row) and double-row, or the so-called V-shaped (two rows of cylinders are located at an angle to each other).
Spark ignition engines are characterized by quantitative power control and external mixing. They can use gasoline and gas. Gasoline engines divided into two modifications - fuel injected engines through the nozzle intake system(usually on inlet valve or into a cylinder) and carburetor (air-fuel mixture entering the cylinders is prepared by the carburetor).
Carburetor engines are being actively superseded by fuel-injected engines. The fuel supply in these engines is carried out according to the signal of the control unit, formed according to the information of the sensor complex (air consumption, rotational speed crankshaft, position throttle valve etc.).
Compression ignition (diesel) engines are characterized by power regulation by changing the composition of the mixture and internal mixture formation.
Car - technical device, which performs the transformation of energy, materials and information in order to facilitate the physical and mental labor of a person, improve its quality and productivity.
There are the following types of machines:
1. Energy machines - converting energy of one type into energy of another type. These machines come in two varieties:
Engines(Fig. 1.2), which convert any kind of energy into mechanical energy (for example, electric motors convert electrical energy, internal combustion engines convert the energy of gas expansion during combustion in a cylinder).
2. Working machines - machines that use mechanical energy to perform work on the movement and transformation of materials. These machines also have two varieties:
Transport vehicles(Fig. 1.4), which use mechanical energy to change the position of the object (its coordinates).
3. Information machines - machines designed to process and convert information. They are divided into:
Math machines(Fig. 1.6), transforming the input information into mathematical model object under study.
4. Cybernetic machines (Fig. 1.8) - machines that control workers or energy machines, which are able to change the program of their actions depending on the state of the environment (i.e. machines with elements of artificial intelligence).
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The concept of the machine unit.
Machine unit called a technical system consisting of one or more machines connected in series or in parallel and designed to perform any required functions. Usually, the machine unit includes: an engine, a transmission mechanism and a working or power machine. At present, a control and management or cybernetic machine is often included in the composition of the machine unit. The transmission mechanism in the machine unit is necessary to match the mechanical characteristics of the engine with the mechanical characteristics of a working or power machine.
Scheme of the machine unit.
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Mechanism and its elements.
Several definitions of mechanism are used in the textbook literature:
First: mechanism called a system of rigid bodies designed to transfer and convert the given movement of one or more bodies into the required movements of other rigid bodies.
Second: Mechanism- a kinematic chain, which includes a fixed link (rack) and the number of degrees of freedom of which is equal to the number of generalized coordinates characterizing the position of the chain relative to the rack.
Third: mechanism called a device for the transmission and transformation of movements and energies of any kind.
Fourth: Mechanism- a system of solid bodies, movably connected by contact and moving in a certain, required way relative to one of them, taken as stationary.
These definitions use previously undefined concepts:
Link- a rigid body or a system of rigidly connected bodies that are part of the mechanism. Kinematic chain- a system of links that form kinematic pairs with each other. Kinematic couple- a movable connection of two links, allowing their certain relative movement. Rack- a link, which, when studying the mechanism, is taken as a fixed one. Number of degrees freedom or mobility of the mechanism- the number of independent generalized coordinates that uniquely determines the position of all its links on a plane or in space.
From theoretical mechanics: Systems of material bodies (points), the positions and movements of which are subject to certain geometric or kinematic restrictions, set in advance and independent of the initial conditions and given forces, is called not free. These restrictions placed on a system and making it non-free are called connections. The positions of the points of the system allowed by the constraints imposed on it are called possible. Quantities independent of each other q 1 ,q 2 , ... q n , completely and uniquely determining the possible positions of the system at an arbitrary moment of time are called generalized coordinates of the system.
The disadvantages of these definitions are: the first does not reflect the ability of the mechanism to transform not only movement, but also forces; the second does not contain an indication of the function performed by the mechanism. Both definitions are in conflict with the definition of a technical system. Given the above, we give the following formulation of the concept of mechanism:
mechanism called a system consisting of links and kinematic pairs forming closed or open circuits, which is designed to transfer and convert the displacements of the input links and the forces applied to them into the required displacements and forces on the output links.
Here: input links- links to which the specified movement and the corresponding force factors (forces or moments) are reported; output links- those on which they receive the required movement and forces.
Starting link- a link, the coordinate of which is taken as a generalized one. Initial kinematic pair- a pair, the relative position of the links in which is taken as a generalized coordinate.
Test tasks for TMM
assembly based on the materials of the Federal Accreditation Agency
(att. nica. en, i- exam. en), NGPU, KamGPI and department. "Mechanization…",
Assoc. Glukhov B.V.
Thematic structure
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Schemes, drawing. |
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1. Basic provisions |
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2. Structure |
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3. Kinematics of lever mechanisms |
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4. Dynamics |
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5. Gear kinematics |
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6. Involute gearing |
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7. Cam mechanisms |
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8. Vibration protection |
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1.Basic provisions
1. The totality of the means of human activity created to carry out the processes of production and service the non-productive needs of society is ...
1) device 2) mechanism
3) technique 4) knot
2. A machine is a device designed to…
1) performing useful work 2) transforming movements
3) transfer of movements 4) transfer and transformation of movement
3. A device that performs mechanical movements to convert energy, materials and information is ...
1) kinematic pair 2) mechanism
3) machine 4) node
4. Machines are divided into classes according to the functions they perform ...
1) energy, workers, information
2) energy, workers, information, cybernetic
3) working, analytical, informational, cybernetic
4) energy, working, analytical
5. energy machine- This...
1) a machine designed to convert any kind of energy into mechanical energy (and vice versa)
2) a machine designed to convert materials
3) a machine that changes the shape, properties and states of a material or processed object
4) a machine designed to convert information
6. The electric current generator is a machine ...
1) transport 2) technological
3) energy 4) information
7. The working machine is…
1) car - engine
2) a machine that converts information
3) a machine that converts materials
4) cybernetic machine
8. transport vehicle- This…
1) car - engine
2) working machine, changing the shape, properties and state of the material or processed object
3) a technological machine that transforms the shape of an object
4) a machine that changes the position of a moving object
9. Transport vehicles are…
1) automatic machines 2) electric motors
3) automatic lines 4) working machines
10. The mechanism is called ...
1) energy conversion device
2) a device for transferring useful work
3) conversion device mechanical movement
4) a system of moving links connected by kinematic pairs
11. The mechanism is designed to ...
1) doing useful work
2) transmission and transformation of mechanical movements
3) information transfer
4) energy transfer and conversion
12. A device for transmitting and converting rotational motion between two shafts is ...
1) machine 2) mechanism
3) fixture 4) assembly unit
13. A system of bodies designed to transform mechanical movement is called ...
1) mechanism 2) machine
3) technique 4) assembly unit
14. A mechanism, all moving links of which describe trajectories in one plane or in parallel planes, is ... a mechanism.
1) spatial 2) flat
3) linear 4) symmetrical
15. A kinematic pair is called ...
1) fixed connection of two contacting links
2) movable connection of more than two links
3) movable connection of two contacting links
4) two links not connected by kinematic pairs
16. The connection of two contacting links of the mechanism, allowing their relative movement, is called ...
1) kinematic connection 2) structural group
3) kinematic pair 4) kinematic chain
17. A kinematic pair is called superior if...
3) the links are in contact along the plane
4) the links are in contact along the line
18. A kinematic pair is called inferior if...
1) the links are in contact on the surface
2) the links are in contact along a line or at a point
3) the links are in contact along the line
4) the links are in contact in any way
19. Mechanisms with higher kinematic pairs are superior to mechanisms with lower kinematic pairs ...
1) Greater motion conversion accuracy
2) transmission of movement over long distances
3) the ability to transfer large forces
4) using fewer links in the chain
20. An example of a single-moving kinematic pair is a pair ...
1) a cylinder on a plane 2) a ball on a plane
3) screw 4) spherical
21. An example of a two-moving kinematic pair is a pair ...
1) cylinder on a plane 2) cylindrical
22. An example of a three-moving kinematic pair is a pair ...
1) ball on a plane 2) cylindrical
3) rotational 4) spherical
23. An example of a four-movable kinematic pair is a pair ...
1) a ball on a plane 2) a cylinder on a plane
3) rotational 4) spherical
24. The number of degrees of freedom of a kinematic pair in the figure is ...
25. The number of degrees of freedom of a kinematic pair in the figure is ...
26. The number of degrees of freedom of a kinematic pair in the figure is ...
27. The number of degrees of freedom of a kinematic pair in the figure is ...
28. Number of degrees of freedom of a kinematic pair E equals…
29. Number of degrees of freedom of a kinematic pair WITH equals…
30. Number of degrees of freedom of a kinematic pair E equals…
31. Number of degrees of freedom of a kinematic pair IN equals…
32. The kinematic pair shown in the figure is called ...
1) screw 2) translational
3) rotational 4) spherical
33. The figure shows symbol according to GOST 2.770 …
34. The figure shows the symbol according to GOST 2.770 …
1) screw kinematic pair
2) translational kinematic pair
3) cylindrical kinematic pair
4) rotational kinematic pair
35. The figure shows the symbol according to GOST 2.770 …
1) screw kinematic pair
2) rotational double kinematic pair
3) cylindrical kinematic pair
4) rotational kinematic pair
36. The figure shows the symbol according to GOST 2.770 …
1) screw kinematic pair
2) spherical kinematic pair
3) spherical kinematic pair with a finger
4) rotational kinematic pair
37. Kinematic chain is ...
1) a system of links that form kinematic pairs with each other
2) a system of links that form kinematic connections with each other
3) a system of links that form kinematic connections with each other
4) a system of links that form among themselves higher kinematic pairs
38. The mechanism is different from the kinematic chain ...
1) the presence of a fixed link (rack)
2) the absence of a fixed link
3) the presence of moving links
4) the presence of expedient movements
39. In a flat kinematic chain ...
1) all points move in the same plane
2) all points move in two planes
3) all points move parallel to one plane
4) all points move parallel to two planes
40. In a closed kinematic chain ...
1) the output link is not connected to the rack
2) all links are movable
3) the input link is not connected to the rack
4) the input and output links are connected with the rack
2.Structure
1. The number of degrees of freedom of a flat mechanism is determined by the formula ...
1) Malysheva 2) Chebysheva
3) Willis 4) Novikov
2. Chebyshev's formula for calculating the number of degrees of freedom of a flat mechanism has the form ...
1) W = 6n + 5p 5 + 4p 4 + 3p 3 + 2p 2 + p 1
2) W \u003d 3n + 2p 1 - p 2
3) W = 6 n – 5 p 1 – 4 p 2 – 3 p 3 – 2 p 4 – p 5
4) W= 3 n – 2 p 1 – p 2
3. If there is a roller in the cam mechanism diagram, its ...
1) replace with a link and two pairs
2) move to the structural profile
3) remove
4) replace with two links
4. The number of degrees of freedom of the mechanism of mechanical scissors is ...
5. The number of degrees of freedom of a flat mechanism, the kinematic diagram of which is shown in the figure, is ...
6. Number of degrees of freedom of a flat mechanism, kinematic scheme
