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1,2,3 Engineering materials, Metals, Non metals
There are two kinds of materials used in engineering – metals and non-metals. We can divide metals into ferrous and non-ferrous. The former contain iron and the latter don’t contain iron. Cast iron and steel are the two most important ferrous metals. Chromium can be added to iron to resist corrosion, and tungsten to increase hardness. Aluminium, copper, and alloys (bronze and brass) are common non-ferrous metals.
Plastics and ceramics are nonmetals; however, plastics may be machined like metals. Plastics are classified in two types - thermo-plastics and termosets. Thermo-plastics can be shaped and reshaped by heat and pressure, but termosets cannot be reshaped, because they undergo chemical changes as they harden. Ceramics are often employed by engineers when materials which can resist high temperatures are needed.
4 New materials technology
Era of new materials will have a profound effect on engineering of the future.
The new materials and new manufacturing processes are continuously being developed methods of casting, Molding, cutting and forging. As a rule these methods are aimed at the reduction number of operations from production of complex and accurate shapes and avoidance of waste.
Joining techniquesлплопл are also providing opportunities for economies. The methods can also be used effectively for assembly, allowing savings to be made in both materials and machine utilization. The brief review of new processes above has indicated that a new materials technology is rapidly emerging and providing new opportunities.
5 Metal casting and forging
Era of new materials will have a profound effect on engineering of the future.
The new materials and new manufacturing processes are continuously being developed methods of casting, Molding, cutting and forging.
A casting may be defined as “a metal object obtained by allowing molten metal to solidify in a mold”, the shape of the object being determined by the shape of the mo0ld cavity. The iron in the molds is allowed to cool for some time and the casting solidifies and hardens.
Metal shaping by controlled plastic deformation is the basis for all forging operations. Modern forging is not only carried out in virtually all metals, it is done at temperatures ranging from more than tow thousands five hundred ’F to room temperature. Part configuration generally determines the forging method chosen.
6 Metal cutting machines
Era of new materials will have a profound effect on engineering of the future. The new materials and new manufacturing processes are continuously being developed methods of casting, Molding, cutting and forging.
Cutting detailed study started about a hundred years ago. Fundamentally all machine-tools remove metal and can be divided into the following categories: turning, drilling, boring, milling and grinding machines. Screw machines can do all of these operations. Thousands of products produced on screw machines. Screw machining is also used to finish shapes produced by other forming and shaping processes.
7 Machines work power
A machine is a device that transmits and changes force or motion into work. Machines whose input energy source is a natural are called prime movers. Natural sources of energy include wind, water, steam, and petroleum. Windmills and waterwheels are prime movers.
Terms like work, force, and power are often used in mechanical engineering, so it is important to define them precisely. Force is an effort that results in motion or physical change. Work is the combination of the force and the distance through which it is exerted. Power is the rate at which work is performed, so we can measured in terms of horsepower. In metric system power is measured in terms of watts and kilowatts, because of famous inventor James Watt, who carried a lot of technic experimentation.
An engine produces power by burning air and fuel. The fuel and air are drawn into the engine cylinder by the piston. Then the fuel and air are compressed by the piston and ignited by the spark plug. They burn and expand very quickly and push the piston down. Thus the power is produced, air are expelled from the cylinder by the piston. There is an inlet valve allowing fresh fuel mixture into the cylinder and an exhaust valve which allows the burnt gases to escape. There are two basic engine operating cycles: a) the four-stroke cycle; b) the two-stroke cycle.
The complete four-stroke cycle comprises:
the induction stroke (the piston moves downwards);
the compression stroke (the piston moves upwards);
the power stroke (the piston moves downwards);
the exhaust stroke (the piston moves upwards).
9 10 Flexible production and robots, Computer
Swift production automation, the introduction of microprocessors, robotics, computers and rotary-conveyer lines, flexible readjustable production is vital for today's industry. Industrial robots play an important part in the process. Many institutes are currently engaged in developing them. The concept of designing robot modules is making successful headway with computer.
Also needed for the operation of flexible systems are robots which will transport works and parts between machine tools. All processes producing by robots are controlled a computer. Experts from the Institute of Machine Studies are developing measuring manipulators and coordinate-measuring machines.
Computer systems are divided into hardware (the physical, electronic and electro-mechanical devices) and software (the programs that control and coordinate the activities of the computer hardware.
The combination of flexible systems with the general system of programmed production, the spreading of flexibility to the processes of preparatory productions — foundry, forging and welding — are also very complicated problems. The flexible system must embrace all the stages of machine building.
11. Metal casting is basic
A foundry is a commercial establishment for producing casting. A casting is a metal object obtained by allowing molten metal to solidify in a mold.
Sand casting production is one of the oldest methods for producing metal castings. This method consist of melting metal in a furnace and pouring it into sand molds. Then the metal solidifies and assumes the shape of the mold cavity. Most castings serve as details or component parts of complex machines and products. But at first they are machined and finished to specified tolerances.
12.There five categories of cutting
There are five general categories of machine-tool. They are lathes, drilling, boring, milling and grinding machines. These machine-tools can perform turning, milling, grinding, boring and etc. operations. Finished parts possess symmetrical shapes, high dimensional accuracies and smooth surfaces. A lot of simple and complex shapes can be produced on screw machines. Screw machining is also used for finished operations.
13. Different types of hybrid cars
There are series and parallel subtypes of hybrids. In the series hybrid, a heat engine powers a generator. Generator chargers the battery or supplies power directly to the propulsion circuit without the battery. In a parallel hybrid, both the heat engine and battery used to deliver power to the generator.
Hybrid cars contain the following parts:
-batteries and transmission.
Some parts of a hybrid are different from the parts of the simple car, such as the engine, but some parts are similar to the simple cars parts, such as the fuel tank.
14.Hybrid cars have some performance
Gasoline engine of a hybrid car is much smaller then on conventional cars, but more efficient. Necessary power is produced by the electric motor and the batteries. The engine of a hybrid car is very efficient, because it is designed not for peak power, but for average power. A hybrid car can recover and stone energy in the battery. A hybrid car has a reduced frontal area and reduced drag. It uses special efficient tires. A hybrid car usually made of lightweight materials.
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