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Non-consumable Electrode Arc welding





Construction processes

 

In the modern industrialized world, construction usually involves the translation of designs into reality. A formal design team may be assembled to plan the physical proceedings, and to integrate those proceedings with the other parts. The design usually consists of drawings and specifications, usually prepared by a design team including surveyors, civil engineers, cost engineers (or quantity surveyors), mechanical engineers, electrical engineers, structural engineers, fire protection engineers, planning consultants, architectural consultants, and archaeological consultants. The design team is most commonly employed by (i.e. in contract with) the property owner. Under this system, once the design is completed by the design team, a number of construction companies or construction management companies may then be asked to make a bid for the work, either based directly on the design, or on the basis of drawings and a bill of quantities provided by a quantity surveyor. Following evaluation of bids, the owner will typically award a contract to the most cost efficient bidder. The modern trend in design is toward integration of previously separated specialties, especially among large firms. In the past, architects, interior designers, engineers, developers, construction managers, and general contractors were more likely to be entirely separate companies, even in the larger firms. Presently, a firm that is nominally "architecture" or "construction management" firm may have experts from all related fields as employees, or to have an associated company that provides each necessary skill. Thus, each such firm may offer itself as "one-stop shopping" for a construction project, from beginning to end. This is designated as a "design Build" contract where the contractor is given a performance specification and must undertake the project from design to construction, while adhering to the performance specifications.

 

Several project structures can assist the owner in this integration, including design-build, partnering and construction management. In general, each of these project structures allows the owner to integrate the services of architects, interior designers, engineers and constructors throughout design and construction. In response, many companies are growing beyond traditional offerings of design or construction services alone and are placing more emphasis on establishing relationships with other necessary participants through the design-build process. The increasing complexity of construction projects creates the need for design professionals trained in all phases of the project's life-cycle and develop an appreciation of the building as an advanced technological system requiring close integration of many sub-systems and their individual components, including sustainability. Building engineering is an emerging discipline that attempts to meet this new challenge.

 



Metals

 

Metals are materials most widely used in industry because of their properties. The study of the production and properties of metals is known as metallurgy.

 

The separation between the atoms in metals is small, so most metals are dense. The atoms are arranged regularly and can slide over each other. That is why metals are malleable (can be deformed and bent without fracture) and ductile (can be drawn into wire). Metals vary greatly in their properties. For example, lead is soft and can be bent by hand, while iron can only be worked by hammering at red heat.

 

The regular arrangement of atoms in metals gives them a crystalline structure. Irregular crystals are called grains. The properties of the metals depend on the size, shape, orientation, and composition of these grains. In general, a metal with small grains will be harder and stronger than one with coarse grains.

 

Heat treatment such as quenching, tempering, or annealing controls the nature of the grains and their size in the metal. Small amounts of other metals (less than1 per cent) are often added to a pure metal. This is called alloying and it changes the grain structure and properties of metals.

 

All metals can be formed by drawing, rolling, hammering and extrusion, but some require hot-working. Metals are subject to metal fatigue and to creep (the slow increase in length under stress) causing deformation and failure. Both effects are taken into account by engineers when designing, for example, airplanes, gas-turbines, and pressure vessels for high-temperature chemical processes. Metals can be worked using machine-tools such as lathe, milling machine, shaper and grinder.

 

The ways of working a metal depend on its properties. Many metals can be melted and cast in moulds, but special conditions are required for metals that react with air.

 

Non-consumable Electrode Arc welding

 

As non-consumable electrodes tungsten or carbon electrodes can be used. In gas-tungsten arc welding a tungsten electrode is used in place of the metal electrode used in shielded metal-arc welding. A chemically inert gas, such as argon, helium, or carbon dioxide is used to shield the metal from oxidation. The heat from the arc formed between the electrode and the metal melts the edges of the metal. Metal for the weld may be added by placing a bare wire in the arc or the point of the weld. This process can be used with nearly all metals and produces a high-quality weld. However, the rate of welding is considerably slower than in other processes.

 

In gas-metal welding, a bare electrode is shielded from the air by surrounding it with argon or carbon dioxide gas and sometimes by coating the electrode with flux. The electrode is fed into the electric arc, and melts off in droplets that enter the liquid metal of the weld seam. Most metals can be joined by this process.

 

Submerged-arc welding is similar to gas-metal arc welding, but in this process no gas is used to shield the weld. Instead of that, the arc and tip of the wire are submerged beneath a layer of granular, fusible material that covers the weld seam. This process is also called electric welding. It is very efficient but can be used only with steels.

 

In resistance welding, heat is obtained from the resistance of metal to the flow of an electric current. Electrodes are clamped on each side of the parts to be welded, the parts are subjected to great pressure, and a heavy current is applied for a short period of time. The point where the two metals touch creates resistance to the flow of current. This resistance causes heat, which melts the metals and creates the weld. Resistance welding is widely employed in many fields of sheet metal or wire manufacturing and is often used for welds made by automatic or semi-automatic machines especially in automobile industry.

 

Automation in Industry

Computers have greatly facilitated the use of feedback in manufacturing processes. Computers gave rise to the development of numerically controlled machines. The motions of these machines are controlled by punched paper or magnetic tapes. In numerically controlled machining centers machine tools can perform several different machining operations.

More recently, the introduction of microprocessors and computers have made possible the development of computer-aided design and computer-aided manufacture (CAD and CAM) technologies. When using these systems a designer draws a part and indicates its dimensions with the help of a mouse, light pen, or other input device. After the drawing has been completed the computer automatically gives the instructions that direct a machining centre to machine the part. Another development using automation are the flexible manufacturing systems (FMS). A computer in FMS can be used to monitor and control the operation of the whole factory.

Automation has also had an influence on the areas of the economy other than manufacturing. Small computers are used in systems called word processors, which are rapidly becoming a standard part of the modern office. They are used to edit texts, to type letters and so on.

Many industries are highly automated or use automation technology in some part of their operation. In communications and especially in the telephone industry dialing and transmission are all done automatically. Railways are also controlled by automatic signaling devices, which have sensors that detect carriages passing a particular point. In this way the movement and location of trains can be monitored.

Not all industries require the same degree of automation. Sales, agriculture, and some service industries are difficult to automate, though agriculture industry may become more mechanized, especially in the processing and packaging of foods. The automation technology in manufacturing and assembly is widely used in car and other consumer product industries. Nevertheless, each industry has its own concept of automation that answers its particular production needs.

 

 

Highly automated systems

Automation is the system of manufacture performing certain tasks, previously done by people, by machines only. The sequences of operations are controlled automatically. The most familiar example of a highly automated system is an assembly plant for automobiles or other complex products.

The term automation is also used to describe non-manufacturing systems in which automatic devices can operate independently of human control. Such devices as automatic pilots, automatic telephone equipment and automated control systems are used to perform various operations much faster and better than could be done by people.

Automated manufacturing had several steps in its development. Mechanization was the first step necessary in the development of automation. The simplification of work made it possible to design and build machines that resembled the motions of the worker. These specialized machines were motorized and they had better production efficiency.

Industrial robots, originally designed only to perform simple tasks in environments dangerous to human workers, are now widely used to transfer, manipulate, and position both light and heavy work pieces performing all the functions of a transfer machine. In the 1920s the automobile industry for the first time used an integrated system of production. This method of production was adopted by most car manufacturers and became known as Detroit automation.

The feedback principle is used in all automatic-control mechanisms when machines have ability to correct themselves. The feedback principle has been used for centuries. An outstanding early example is the fly ball governor, invented in 1788 by James Watt to control the speed of the steam engine. The common household thermostat is another example of a feedback device. Using feedback devices, machines can start, stop, speed up, slow down, count, inspect, test, compare, and measure. These operations are commonly applied to a wide variety of production operations.

 

Industrial construction

Industrial construction, though a relatively small part of the entire construction industry, is a very important component. Owners of these projects are usually large, for-profit, industrial corporations. These corporations can be found in such industries as Infrastructure, Power Transmission & Distribution, metallurgical and material handling, medicine, petroleum, chemical, power generation, manufacturing etc. Processes in these industries require highly specialized expertise in planning, cost estimating, design, and construction. As in building and heavy/highway construction, this type of construction requires a team of individuals to ensure a successful project often undertaken by big construction companies.

In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking. Normally, the job is managed by a project manager, and supervised by a construction manager, design engineer, construction engineer or project architect. For the successful execution of a project, effective planning is essential. involved with the design and execution of the infrastructure in question must consider the environmental impact of the job, the successful scheduling, budgeting, construction site safety, availability of building materials, logistics, inconvenience to the public caused by construction delays and bidding, etc.

Промышленное строительство

Промышленное строительство, хотя и является относительно небольшой частью всей строительной отрасли, является очень важным компонентом. Владельцами этих проектов обычно являются крупные коммерческие промышленные корпорации. Эти корпорации могут быть найдены в таких отраслях, как инфраструктура, передача и распределение электроэнергии, металлургия и перевалка материалов, медицина, нефтехимия, химия, производство энергии, производство и т. Д. Процессы в этих отраслях требуют высокоспециализированных знаний в области планирования, оценки затрат, проектирования и строительство. Как и в строительстве и строительстве тяжелых / магистральных дорог, для такого типа строительства требуется группа частных лиц, чтобы обеспечить успешный проект, часто осуществляемый крупными строительными компаниями.

В области архитектуры и гражданского строительства строительство - это процесс, который состоит из строительства или сборки инфраструктуры. Крупномасштабное строительство не является чем-то одним видом деятельности - это подвиг человеческой многозадачности. Обычно работу руководит руководитель проекта, а руководителем проекта является строительный менеджер, инженер-проектировщик, инженер-строитель или архитектор проекта. Для успешного выполнения проекта важно эффективное планирование. Связанные с проектированием и исполнением рассматриваемой инфраструктуры, должны учитывать воздействие на окружающую среду работы, успешное планирование, бюджетирование, безопасность строительных площадок, доступность строительных материалов, материально-техническое обеспечение, неудобства для населения из-за задержек в строительстве и торгов

 

Definition of machines

Defined in the simplest terms a machine is a device that uses force to accomplish something. More technically, it is a device that transmits and changes force or motion into work. This definition implies that a machine must have moving parts. A machine can be very simple, like a block and tackle to raise a heavy weight, or very complex, like a railroad locomotive or the mechanical systems used for industrial processes.

A machine receives input from an energy source and transforms it into output in the form of mechanical or electrical energy. Machines whose input is a natural source of energy are called prime movers. Windmills and waterwheels are prime movers; so are the great turbines driven by water or steam that turn the generators that produce electricity; and so are internal combustion engines that use petroleum products as fuel. Electric motors are not prime movers, since an alternating current of electricity which supplies most electrical energy does not exist in nature.

Terms like work, force, and power are frequently used in mechanical engineering, so it is necessary to define them precisely. Force is an effort that results in motion or physical change. If you use your muscles to lift a box you are exerting force on those blades, thereby setting them in motion. In a technical a sense work is the combination of the force and the distance through which it is exerted. To produce work, a force must act through a distance.

Power is another term used in a special technical sense in speaking of machines. It is the rate at which work is performed.

Определение машин

 

В простейших определениях машина - это устройство, которое использует силу для достижения чего-либо. Более технически это устройство, которое передает и изменяет силу или движение в работе. Это определение подразумевает, что машина должна иметь движущиеся части. Машина может быть очень простой, такой как блок и тальк, чтобы поднимать тяжелый груз или очень сложный, как железнодорожный локомотив или механические системы, используемые для промышленных процессов.

Машина получает вход от источника энергии и преобразует его в выходной сигнал в виде механической или электрической энергии. Машины, чей вход является естественным источником энергии, называются первичными двигателями. Ветряные мельницы и водяные колеса являются основными двигателями; Так что большие турбины, приводимые в движение водой или паром, превращают генераторы, вырабатывающие электричество; А также двигатели внутреннего сгорания, в которых в качестве топлива используются нефтепродукты. Электродвигатели не являются основными двигателями, поскольку переменный ток электричества, который обеспечивает большую часть электрической энергии, в природе не существует.

Такие термины, как работа, сила и сила, часто используются в машиностроении, поэтому их необходимо точно определить. Сила - это усилие, которое приводит к движению или физическим изменениям. Если вы используете мышцы для поднятия ящика, вы прикладываете силу к этим лезвиям, тем самым приводя их в движение. В техническом смысле работа - это комбинация силы и расстояния, через которое она действует. Чтобы произвести работу, сила должна действовать через расстояние.

Мощность - это еще один термин, используемый в техническом смысле, говоря о машинах. Это скорость, с которой выполняется работа.

 

 

Automation

We now use the term automation for specific techniques combined to operate automatically in a complete system. These techniques are possible because of electronic devices, most of which have come into use in the last thirty years. They include program, action, sensing or feedback, decision, and control elements as components of a complete system.

The program elements determine what the system does and the step-by-step manner in which it works to produce the desired result. A program is a step-by-step sequence that breaks a task into its individual parts. The action elements are those which do the actual work. They may carry or convey materials to specific places at specific times or they may perform operations on the materials. The term mechanical handling device is also used for the action elements.

Perhaps the most important part of an automated system is sensing or feedback. Sensing devices automatically check on parts of the manufacturing process such as the thickness of a sheet of steel or paper. This is called feedback because the instruments return or feed back this information to the central system control.

The decision element is used to compare what is going on in the system with what should be going on, it receives information from the sensing devices and makes decisions necessary to maintain the system correctly. The control element consists of devices to carry out the commands of the decision element. There may be many kinds of devices: valves that open or close, switches that control the flow of electricity, or regulators that change the voltage in various machines; they make the necessary corrections or adjustments to keep the system in conformity with its program.

An industrial engineer working with automated systems is part of a team. Many components of the system, such as computers, are electronic devices so electronic devices so electronic engineers and technicians are also involved. Many of the industries in which automation has proved particularly suitable – chemicals, papermaking, metals processing – involve chemical processes, so there may be chemical engineers at work too. An industrial engineer with expertise in all these fields may become a systems engineer for automation projects thereby coordinating the activities of all the members of the team.

 

 

Tomorrow's Factory

 

Machining is only one part of the overall production process in the engineering workshop. There are two more basic operations: design and administration. In the engineering industry of the future, all three of these operations will be done with the help of computers, which will greatly reduce the need for labor.

There would be three main computers: one each for the flexible manufacturing system, design and administration. Instructions that enter the first computer control how and which goods are made; draughtsman work out which goods they want made with the second machine; and in the third are lodged all the details about orders, scheduling, the state of stocks and so on. All three computers are linked to each other, and also to an automated warehouse from which raw materials are passed by a transport mechanism to the factory floor and the machining area.

The few places where people would be involved with the factory's processes would be in the design room and in a control area where the factory's administrators sit. Draftsmen would design products using their keyboards and screens. The codes representing these parts would come along wires to the production computer, which, in turn, would instruct its battery of machine tools to make the items. There would be a few "seeing" robots in the production department, to make the assembly job easier. Meanwhile, the factory's administrators could keep track of the whole operation, getting information from the system by keying in instructions to their terminals.

At the heart of the factory would be a complex communications network that links all the machines in the plant so that they constantly relay instructions to each other. In this way all the machines in the plant would inform each other of what is going on. The mechanisms in the plants will be linked by wires in the same way as the telephone network connects up towns and villages, houses and offices. The main difference is that the machines will talk to each other in a binary code.

It would not be an unmanned factory, but it would be pretty near such a thing. Given the rate of technical progress over the past ten to twenty years, such plants will be with us very soon.

Heating and ventilation

Besides masonry, a brick work, any engineer must know about heating and ventilation. They are two branches of engineering which are very closely connected. Both they are treated as a dual subject. Heating is to prevent too rapid loss of heat from the body. The rate of heat lost from the body is controlled. Some old concepts of heating have been gradually changed since engineers obtained more precise knowledge about how the body loses heat. Insufficient attention was paid formerly to loss by radiation, which is the transmission of energy in the form of waves from a body to surrounding bodies at a temperature. The human being also loses heat by conduction and convection, the latter by air currents not only past his skin or outside clothing surface but also by evaporation of moisture from his skin.

The determination of the capacity or size of the various components of the heating system is based on the fundamental concept that heat supplied to a space equals heat lost from the space. The most widely used system of heating is the central heating. There are two most common systems of heating: hot water and steam. There the fuel is burned in one place, from which steam, hot water or warm air is distributed to adjacent and remote spaces to be heated. Both systems are widely used nowadays. A hot-water system consists of the boilers and a system of pipes connected to radiators suitably located in the rooms. The steel or copper pipes give hot water to radiators or convectors which give up their heat to the rooms. Then cooled water is returned to the boiler for reheating. As for steam systems, steam is usually generated. The steam is led to the radiators through or by means of steel or copper pipes. The steam gives up its heat to the radiators and the radiators to the room. The condensate is returned to the boiler by gravity or by a pump. The air valve on each radiator is necessary for air to escape. Otherwise it would prevent steam from entering the radiator.

Recent efforts have resulted to completely conceal heating equipment in an arrangement. Hot water, steam, air, or electricity are circulated through distribution units embedded in the building construction. Panel heating is a method of introducing heat to rooms in which emitting surfaces are usually completely concealed in the floor, walls or ceiling. The heat is disseminated from such panels partly by radiation and partly by convection. Ceiling panels release the largest proportion of heat by radiation and floor panels release the smallest one. The proportion of heat disseminated by radiation and convection is also dependent to some extent upon panel-surface temperatures.

Concrete

Nowadays a building's framework is made of reinforced concrete and of structural steel. Concrete is made by mixing together small stones, sand, cement and water. The coarse stones used in the mix give the concrete its strength. The sand is needed to fill the gaps between the stones. The cement, mixed with just enough water to make it into a paste, covers the surface of all solids, and binds the entire mixture into single mass. It is used less water to make mixing concrete denser and stronger. It is a difficulty here. Dry mixing concrete is not so easy to stir as one that is fairly wet and sloppy. When it is really strong concrete, it is mixed with the necessary minimum of water and placed in the forms.

After this it is vibrated with electrically vibrated bars. The mixture is tipped or piped into forms (wooden molds) of the shape required. To make concrete resistant to bending, building engineers reinforce it. It is done by putting bars of steel or miniature steel frameworks into the forms. Hence is named «reinforced concrete». With such a material a variety of constructional shapes can be produced. They can be "shells" and roofs. For this reinforced concrete is used in thin sheets. Reinforced concrete can be used more effectively if before the external load comes on. For instance, suppose that a reinforced beam could be bent out of the straight by an inch before it developed serious cracks. By pressing it in reverse, building engineers prepare the concrete in advance to withstand the pressures and pulls that the external load causes. Concrete can be pressed in two ways. In the first method, the concrete is casted around stretched steel wires. After setting concrete, the wires are released and compress the concrete as they contract. Such a method of pressing produces pretension concrete.

The other method is called post-tensioning. In the case of a beam the concrete is casted around polythene tubes. After setting concrete- steel cables are drawn through polythene tubes. These cables are anchored at one end of the beam, stretched by jacks and then fixed at the end of the beam. In constructing of a building, it is possible to cast the floors and walls as well as the framework directly on the spot where they are to stand. Building forms a monolith. Last one is a large artificial stone composed entirely of concrete that has been shaped within wooden molds fitted together perfectly. To cast all the parts in place, a builder has to use many forms. They are removed as soon as the concrete has set. Before beginning another work, concrete must be given plenty of time to harden. In order to save time, a builder may prefer to use a number of standardized concrete units. These can be made. Individual members can be pressed. Also different sections of the building can be prefabricated.

Central heating system

The term "central heating" applied to the heating of domestic and other buildings indicates that the whole of a building is heated from a central source. Usually an independent boiler is fired by solid fuel, gas, electricity or fuel oil.

The boiler is generally placed at the lowest available point in the building, having regard at the same time to convenience of stoking and delivery of fuel. The boiler may be one of a number of types. It may be a solid one-piece casting, rectangular in form; it may be sectional; or it may be conical in shape and wrought or cast iron. For smaller system, the first and last-named types are both cheap and suitable. The sectional boiler has the advantage of the possibility of added sections should more heat be needed subsequent to initial installation.

Sectional and shell type boilers are almost invariably used for bigger installations.

In general, a heating system should be designed so that the water will circulate by gravity. In some installations, circumstances are such that a pump or accelerator must be used to achieve a satisfactory circulation. This should be avoided if possible.

When designing a heating system for a large building, it is usual — in the interests of economy and to ensure efficient heating — to first calculate how much heat will be needed to maintain the building at the desired temperature. Then the size of the boiler and the amount of pipe and radiator heating surface required to give out this heat will be estimated. For small systems, "rule-of-thumb" methods and past experience are generally a sufficient guide.

The overhead drop-feed system shows how the hot water from the boiler is carried as high as possible in the building, from where it falls "in cooling, through the various branch pipes and radiators, back to the boiler. In this type of system, the maximum amount of "circulating head" or pressure, would be obtained.

Building materials

Building materials are very important in the construction. But it is more important for any designer to select and adapt such building materials of construction that will give the most effective result by the most economical means. In this choice of materials for any work of constructions many factors must be considered by the civil engineer. These factors include availability, cost, physical properties of materials and others.

Practically, all buildings materials have their advantages and disadvantages. That’s why some materials are used most widely in building construction for the purpose of binding together masonry units. Among them are lime, gypsum and cement. Last material forms very important elements in all masonry structures, such as stone, a brick. Since the time of its introduction a gradual improvement of Portland cement quality has led to the elaboration of rapid hardening Portland cements, or “high early strength”. Portland cement like other materials can be modified to suit a particular application. Later developments include low heat and sulphate-resisting cements. The scope for such purpose – made cements has led to the development of an increasing variety such as high alumina cement, blast-furnace slag. They may be also white and colored cements. Alumina cement has an extremely high rate of strength increase. Portland blast- furnace cement has greater resistance to some forms of chemicals.

So, cement is the most important component of concrete. Concrete is even less uniform than many other materials. Concrete may be considered an artificial conglomerate of “crushed stone, gravel or similar inert material with a mortar”. A mortar is a mixture of sand, screenings or similar inert particles with cement and water. It is very important to know everything about proportions. The most accurate method of measuring proportions is to weigh the required quantities of each material. This may be done whether the proportions are based upon volumes or weights. This method is being extensively used in road construction and in many central mixing and in central proportioning plants. It is also widely used in large building constructions. Sometimes timber, steel and concrete are all very over considerable ranges in the properties desired by the engineer. Even steel varies considerably in its microstructure.

 

 

The Role of Science in Manufacture

Future improvements in productivity are largely dependent on the application of science to manufacturing. This depends in turn on the availability of large numbers of scientifically trained engineers. Higher schools can serve the needs of industry in two ways: by performing basic research and by training well-qualified engineers in the manufacturing field.

There is a growing need for engineers who are familiar with the fundamental problems in metal processing and manufacturing. In the near future many of the engineers will be recent university graduates. A few will come through courses of study in industry. Others, having a basic engineering knowledge will continue additional studies at colleges to prepare themselves for work in industry. Therefore, an engineer does not finish his education when he receives his diploma, particularly in the fields of interest to tool engineers who are to study new developments constantly.

There are numerous ways in which industry and education can cooperate on problems of common interest. Scientists and research engineers are engaged in work that is intended to provide a scientific approach to many purely industrial problems. These scientists and engineers can make a real contribution to engineering education or academic research. They can, for example, teach advanced engineering courses and they can actively participate in basic and applied research.

Similarly, large and complicated projects of new technologies could well be handled by institute researchers working on practical applications. This would often provide the most efficient approach to the solution of processing problems.

 

 

Chemical and physical changes

An iron rod held in the fire long enough increases in energy content until it u becomes too hot to hold in the unprotected hand. Nevertheless the rod is still iron, and when cooled to its originals temperature,1 its properties are just as they were before. The heating and subsequent cooling of the rod are examples of physical changes. A physical change may result in a more or less temporary alteration of a few of the properties of a substance involved, but no change of composition results from it and most of the altered properties usually regain their former value. Changes of this type are numerous and many of them are familiar to everyone. As an example we may take the behavior of ice when it is heated. At first when heated the ice melts, when further heated, the liquid water boils forming the gaseous water. If the steam is cooled, the process is reversed - when cooled sufficiently, the ice results.

The substance present in every instance was water. This experiment shows that there are three physical states in which the substance may exist. If the rod concerned is placed in a container of hydrochloric acid, it will be noted that bubbles begin to on the road. If the rod involved is left in the acid for some time, the evolution of gas will continue. When examined, it will be found that the rod has diminished in mass or disappeared altogether. The liquid in the container if examined will have a greenish color. If evaporated, a mass of greenish crystals will be obtained. The crystals will have totally different properties. This is an example of a chemical change.

So, a change may be called a chemical reaction or simply a reaction, the substances entering into a chemical reaction are called reactants. Phenomena accompanied by radical changes of substances are called chemical phenomena.

 

 

ТMetal cutting

Cutting is one of the oldest arts practiced in the stone age , but the cutting of metals was not found possible until the 18th century, and its detailed study started about a hundred years ago.

Now in every machine-shop you may find many machines for working metal parts, these cutting machines are generally called machine-tools and are extensively used in many branches of engineering. Fundamentally all machine-tools remove metal and can be divided into the following categories:

1. Turning machines (lathes)

2. Drilling machines

3. Boring machines

4. Milling machines

5. Grinding machines

Machining of large-volume production parts is best accomplished by screw machines. These machines can do turning, threading, facing, boring and many other operations. Machining can produce symmetrical shapes with smooth surfaces and dimensional accuracies not generally attainable by most fabrication methods.

Screw-machined parts are made from bar stock or tubing fed intermittently and automatically through rapidly rotating hollow spindles. The cutting tools are held on turrets and tool slides convenient to the cutting locations. Operations are controlled by cams or linkages that position the work, feed the tools, hold them in position for the proper time, and then retract the tools. Finished pieces are automatically separated from the raw stock and dropped into a container.

Bushings, bearings, nuts, bolts, studs, shafts and many other simple and complex shapes are among the thousands of products produced on screw machines. Screw machining is also used to finish shapes produced by other forming and shaping processes.

 

European bricks

 

The oldest domestic bricks were found in Greece. In the 12th century, bricks from Northern-Western Italy were re-introduced to Northern Germany, where an independent tradition evolved. It culminated in the so-called brick Gothic, a reduced style of Gothic architecture that flourished in Northern Europe, especially in the regions around the Baltic Sea, which are without natural rock resources. Brick Gothic buildings, which are built almost exclusively of bricks, are to be found in Denmark, Germany, Poland, and Russia. During the Renaissance and the Baroque, visible brick walls were unpopular and the brickwork was often covered with plaster. It was only during the mid-18th century that visible brick walls regained some degree of popularity. The transport in bulk of building materials such as bricks over long distances was rare before the age of canals, railways, roads and heavy goods vehicles. Before this time bricks were generally made close to their point of intended use. It has been estimated that in England in the 18th century carrying bricks by horse and cart for ten miles (approx. 16 km) over the poor roads then existing could more than double their price.

 

Bricks were often used for reasons of speed and economy, even in areas where stone was available. The buildings of the Industrial Revolution in Britain were largely constructed of brick and timber due to the demand created. During the building boom of the 19th century in the eastern seaboard cities of Boston and New York City, for example, locally made bricks were often used in construction in preference to the brownstones of New Jersey and Connecticut for these reasons.

 

The trend of building high office buildings that emerged towards the beginning of the 20th century displaced brick in favor of cast and wrought iron and later steel and concrete. Some early 'skyscrapers' were made in masonry, and demonstrated the limitations of the material – for example, the Monadnock Building in Chicago is masonry and just 17 stories high; the ground walls are almost 6 feet (1.8 m) thick to give the needed support; clearly building any higher would lead to excessive loss of internal floor space on the lower floors.

 

Architecture

The science of building is architecture. Any engineer cannot take a form of the building without consideration of structural principles, materials, social and economic requirements. So a building cannot be considered as a work of architecture. From the very beginning architecture of many skills, systems and theories have been used for the construction of the buildings that men have housed in all their essential activities. The coexistence of change and survival is evident in all phases of the human story. This change and repetition is clearly illustrated in any architectural style. The historical background of architecture is the value of our cultural heritage. The heritage of the past cannot be ignored. Such recognition of continuity does not imply repetition or imitation. It must be expressed in contemporary terminology.

Writing on architecture is almost as old as writing itself. There are a lot of books on the theory of architecture, on the art of a building and on the aesthetic appearance of buildings. The oldest book is a work of Marcus Vitruvius Pollio, written in the first century B.C. Nearly two thousand years ago the Roman architect Vitruvius set the principles upon which buildings should be designed and aims to guide the architect. He was the first who listed three basic factors in architecture – “convenience, strength and beauty”. The sequence of these three basic aims - “convenience, strength and beauty” – has its own significance. These three factors are always present and are always interrelated in the best structures. It is impossible for a true architect to think of one of them without considering the other two as well. Thus architectural design entails a consideration of the constant interaction of these factors. At last we can say that every element in a building has a triple implication. At the same time its contemporary expression must be creative and consequently new.

Architecture is an art. The triple nature of architectural design is one of the reasons why architecture is a difficult art. The architect does not first plan a building from the point of view of convenience, then designs around his plan a strong construction to shelter it, and finally adjusts and decorates the whole to make it pretty. First of all, the designer must have sufficient knowledge of engineering, building materials to enable him to create economically. I see, any building is built because of some definite human need. The use problem – “convenience” – is therefore primary. In addition, the designer must posses the creative imagination which will enable him to integrate the plan and the construction into one harmonious whole. The architect’s feeling of satisfaction in achieving such as integration is one of his greatest rewards.

 

 

History of bricks A brick is a block or a single unit of a ceramic material used in masonry construction. Typically bricks are stacked together or laid as brickwork using various kinds of mortar to hold the bricks together and make a permanent structure. Bricks are typically produced in common or standard sizes in bulk quantities. They have been regarded as one of the longest lasting and strongest building materials used throughout history.

In the general sense, a "brick" is a standard-sized weight-bearing building unit. Bricks are laid in horizontal courses, sometimes dry and sometimes with mortar. When the term is used in this sense, the brick might be made from clay, lime-and-sand, concrete, or shaped stone. In a less clinical and more colloquial sense, bricks are made from dried earth, usually from clay-bearing subsoil. In some cases, such as adobe, the brick is merely dried. More commonly it is fired in a kiln of some sort to form a true ceramic.

The earliest bricks were dried brick, meaning they were formed from clay-bearing earth or mud and dried (usually in the sun) until they were strong enough for use. The oldest discovered bricks, originally made from shaped mud and dating before 7500 BC, were found at Tell Aswad, in the upper Tigris region and in southeast Anatolia close to Diyarbakir. Other more recent findings, dated between 7,000 and 6,395 BC, come from Jericho, Catal Hüyük, and the ancient Indus Valley cities of Buhen, Mohenjo-daro, Harappa, and Mehrgarh. The Romans made use of fired bricks, and the Roman legions, which operated mobile kilns, introduced bricks to many parts of the empire. Roman bricks are often stamped with the mark of the legion that supervised their production. The use of bricks in southern and western Germany, for example, can be traced back to traditions already described by the Roman architect Vitruvius.

 

 

Construction careers

The examples and perspective in this section deal primarily with the United Kingdom and do not represent a worldwide view of the subject. There are many routes to the different careers within the construction industry which vary by country. However, there are three main tiers of careers based on educational background which are common internationally:

Unskilled and semi-skilled – general site labor with little or no construction qualifications: skilled – on-site managers whom possess extensive knowledge and experience in their craft or profession. Technical and management – Personnel with the greatest educational qualifications, usually graduate degrees, trained to design, manage and instruct the construction process. Skilled occupations in the UK require further education qualifications, often in vocational subject areas. These qualifications are either obtained directly after the completion of compulsory education or through "on the job" apprenticeship training .In the UK 8500 construction-related apprenticeships were commenced in 2007. Technical and specialised occupations require more training as a greater technical knowledge is required. These professions also hold more legal responsibility. Architect – Typically holds 1, undergraduate 3 year degree in architecture + 1, post-graduate 2 year degree (DipArch or BArch) in architecture plus 24 months experience within the industry. To use the title "architect" the individual must be registered on the Architects Registration Board register of Architects.

Civil engineer – Typically holds a degree in a related subject. The Chartered Engineer qualification is controlled by the Engineering Council, and is often achieved through membership of the Institution of Civil Engineers. A new university graduate must hold a master's degree to become chartered, persons with bachelor's degrees may become an Incorporated Engineer. Building services engineer – Often referred to as an "M&E Engineer" typically holds a degree in mechanical or electrical engineering. Chartered Engineer status is governed by the Engineering Council, mainly through the Chartered Institution of Building Services Engineers.

Project manager – Typically holds a 4-year or greater higher education qualification, but are often also qualified in another field such as quantity surveying or civil engineering. Structural engineer – Typically holds a bachelors or master's degree in structural engineering, new university graduates must hold a master's degree to gain chartered status from the Engineering Council, mainly through the Institution of Structural Engineers.

 

Construction processes

 

In the modern industrialized world, construction usually involves the translation of designs into reality. A formal design team may be assembled to plan the physical proceedings, and to integrate those proceedings with the other parts. The design usually consists of drawings and specifications, usually prepared by a design team including surveyors, civil engineers, cost engineers (or quantity surveyors), mechanical engineers, electrical engineers, structural engineers, fire protection engineers, planning consultants, architectural consultants, and archaeological consultants. The design team is most commonly employed by (i.e. in contract with) the property owner. Under this system, once the design is completed by the design team, a number of construction companies or construction management companies may then be asked to make a bid for the work, either based directly on the design, or on the basis of drawings and a bill of quantities provided by a quantity surveyor. Following evaluation of bids, the owner will typically award a contract to the most cost efficient bidder. The modern trend in design is toward integration of previously separated specialties, especially among large firms. In the past, architects, interior designers, engineers, developers, construction managers, and general contractors were more likely to be entirely separate companies, even in the larger firms. Presently, a firm that is nominally "architecture" or "construction management" firm may have experts from all related fields as employees, or to have an associated company that provides each necessary skill. Thus, each such firm may offer itself as "one-stop shopping" for a construction project, from beginning to end. This is designated as a "design Build" contract where the contractor is given a performance specification and must undertake the project from design to construction, while adhering to the performance specifications.

 

Several project structures can assist the owner in this integration, including design-build, partnering and construction management. In general, each of these project structures allows the owner to integrate the services of architects, interior designers, engineers and constructors throughout design and construction. In response, many companies are growing beyond traditional offerings of design or construction services alone and are placing more emphasis on establishing relationships with other necessary participants through the design-build process. The increasing complexity of construction projects creates the need for design professionals trained in all phases of the project's life-cycle and develop an appreciation of the building as an advanced technological system requiring close integration of many sub-systems and their individual components, including sustainability. Building engineering is an emerging discipline that attempts to meet this new challenge.

 

Metals

 

Metals are materials most widely used in industry because of their properties. The study of the production and properties of metals is known as metallurgy.

 

The separation between the atoms in metals is small, so most metals are dense. The atoms are arranged regularly and can slide over each other. That is why metals are malleable (can be deformed and bent without fracture) and ductile (can be drawn into wire). Metals vary greatly in their properties. For example, lead is soft and can be bent by hand, while iron can only be worked by hammering at red heat.

 

The regular arrangement of atoms in metals gives them a crystalline structure. Irregular crystals are called grains. The properties of the metals depend on the size, shape, orientation, and composition of these grains. In general, a metal with small grains will be harder and stronger than one with coarse grains.

 

Heat treatment such as quenching, tempering, or annealing controls the nature of the grains and their size in the metal. Small amounts of other metals (less than1 per cent) are often added to a pure metal. This is called alloying and it changes the grain structure and properties of metals.

 

All metals can be formed by drawing, rolling, hammering and extrusion, but some require hot-working. Metals are subject to metal fatigue and to creep (the slow increase in length under stress) causing deformation and failure. Both effects are taken into account by engineers when designing, for example, airplanes, gas-turbines, and pressure vessels for high-temperature chemical processes. Metals can be worked using machine-tools such as lathe, milling machine, shaper and grinder.

 

The ways of working a metal depend on its properties. Many metals can be melted and cast in moulds, but special conditions are required for metals that react with air.

 

Non-consumable Electrode Arc welding

 

As non-consumable electrodes tungsten or carbon electrodes can be used. In gas-tungsten arc welding a tungsten electrode is used in place of the metal electrode used in shielded metal-arc welding. A chemically inert gas, such as argon, helium, or carbon dioxide is used to shield the metal from oxidation. The heat from the arc formed between the electrode and the metal melts the edges of the metal. Metal for the weld may be added by placing a bare wire in the arc or the point of the weld. This process can be used with nearly all metals and produces a high-quality weld. However, the rate of welding is considerably slower than in other processes.

 

In gas-metal welding, a bare electrode is shielded from the air by surrounding it with argon or carbon dioxide gas and sometimes by coating the electrode with flux. The electrode is fed into the electric arc, and melts off in droplets that enter the liquid metal of the weld seam. Most metals can be joined by this process.

 

Submerged-arc welding is similar to gas-metal arc welding, but in this process no gas is used to shield the weld. Instead of that, the arc and tip of the wire are submerged beneath a layer of granular, fusible material that covers the weld seam. This process is also called electric welding. It is very efficient but can be used only with steels.

 

In resistance welding, heat is obtained from the resistance of metal to the flow of an electric current. Electrodes are clamped on each side of the parts to be welded, the parts are subjected to great pressure, and a heavy current is applied for a short period of time. The point where the two metals touch creates resistance to the flow of current. This resistance causes heat, which melts the metals and creates the weld. Resistance welding is widely employed in many fields of sheet metal or wire manufacturing and is often used for welds made by automatic or semi-automatic machines especially in automobile industry.

 

Automation in Industry

Computers have greatly facilitated the use of feedback in manufacturing processes. Computers gave rise to the development of numerically controlled machines. The motions of these machines are controlled by punched paper or magnetic tapes. In numerically controlled machining centers machine tools can perform several different machining operations.

More recently, the introduction of microprocessors and computers have made possible the development of computer-aided design and computer-aided manufacture (CAD and CAM) technologies. When using these systems a designer draws a part and indicates its dimensions with the help of a mouse, light pen, or other input device. After the drawing has been completed the computer automatically gives the instructions that direct a machining centre to machine the part. Another development using automation are the flexible manufacturing systems (FMS). A computer in FMS can be used to monitor and control the operation of the whole factory.

Automation has also had an influence on the areas of the economy other than manufacturing. Small computers are used in systems called word processors, which are rapidly becoming a standard part of the modern office. They are used to edit texts, to type letters and so on.

Many industries are highly automated or use automation technology in some part of their operation. In communications and especially in the telephone industry dialing and transmission are all done automatically. Railways are also controlled by automatic signaling devices, which have sensors that detect carriages passing a particular point. In this way the movement and location of trains can be monitored.

Not all industries require the same degree of automation. Sales, agriculture, and some service industries are difficult to automate, though agriculture industry may become more mechanized, especially in the processing and packaging of foods. The automation technology in manufacturing and assembly is widely used in car and other consumer product industries. Nevertheless, each industry has its own concept of automation that answers its particular production needs.

 

 

Highly automated systems

Automation is the system of manufacture performing certain tasks, previously done by people, by machines only. The sequences of operations are controlled automatically. The most familiar example of a highly automated system is an assembly plant for automobiles or other complex products.

The term automation is also used to describe non-manufacturing systems in which automatic devices can operate independently of human control. Such devices as automatic pilots, automatic telephone equipment and automated control systems are used to perform various operations much faster and better than could be done by people.

Automated manufacturing had several steps in its development. Mechanization was the first step necessary in the development of automation. The simplification of work made it possible to design and build machines that resembled the motions of the worker. These specialized machines were motorized and they had better production efficiency.

Industrial robots, originally designed only to perform simple tasks in environments dangerous to human workers, are now widely used to transfer, manipulate, and position both light and heavy work pieces performing all the functions of a transfer machine. In the 1920s the automobile industry for the first time used an integrated system of production. This method of production was adopted by most car manufacturers and became known as Detroit automation.

The feedback principle is used in all automatic-control mechanisms when machines have ability to correct themselves. The feedback principle has been used for centuries. An outstanding early example is the fly ball governor, invented in 1788 by James Watt to control the speed of the steam engine. The common household thermostat is another example of a feedback device. Using feedback devices, machines can start, stop, speed up, slow down, count, inspect, test, compare, and measure. These operations are commonly applied to a wide variety of production operations.

 

Industrial construction

Industrial construction, though a relatively small part of the entire construction industry, is a very important component. Owners of these projects are usually large, for-profit, industrial corporations. These corporations can be found in such industries as Infrastructure, Power Transmission & Distribution, metallurgical and material handling, medicine, petroleum, chemical, power generation, manufacturing etc. Processes in these industries require highly specialized expertise in planning, cost estimating, design, and construction. As in building and heavy/highway construction, this type of construction requires a team of individuals to ensure a successful project often undertaken by big construction companies.

In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking. Normally, the job is managed by a project manager, and supervised by a construction manager, design engineer, construction engineer or project architect. For the successful execution of a project, effective planning is essential. involved with the design and execution of the infrastructure in question must consider the environmental impact of the job, the successful scheduling, budgeting, construction site safety, availability of building materials, logistics, inconvenience to the public caused by construction delays and bidding, etc.

Промышленное строительство









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