BASIC MECHANICAL AND CIVIL ENGINEERING

BASIC MECHANICAL AND CIVIL

ENGINEERING

UNIT-I

THERMAL ENGINEERING

I.C engines

An internal combustion engine is heat engine where combustion of fuel with air takes place inside the engine cylinder.

CLASSIFICATION OF IC ENGINE

I.C. engines can be classified as follows.

1. According to the number of strokes required to complete a cycle

2 stroke engine

4 stroke engine

2. According to fuel used

Petrol engine

Diesel engine

Gas Engine

3. According to thermodynamic cycle of operation:

Constant volume or Otto cycle

Constant Pressure or Diesel cycle

Mixed or Dual cycle

4. According to the ignition system used:

Spark Ignition engine

Compression Ignition Engine

5. According to the number of cylinders:

Single cylinder engine

Multi Cylinder engine

6. According to arrangement of cylinders:

Vertical engine

Horizontal engine

In line engines

V-type engines

Radial engine

7. According to the cooling system:

Air cooled engine

Water cooled engine

8. According to the speed of the engine:

Low Speed (below 400 rpm)

Medium Speed (400 to 900 rpm)

High Speed (above 900 rpm)

9. According to lubrication system:

Splash Lubrication

Pressure Lubrication

10. According to field of application:

Stationary engine and mobile engine

FOUR STROKE PETROL ENGINE

The four stroke-cycles refers to its use in petrol engines, gas engines, light, oil engine and heavy

oil engines in which the mixture of air fuel are drawn in the engine cylinder. Since ignition in

these engines is due to a spark, therefore they are also called spark ignition engines.

SUCTION STROKE

In this Stroke the inlet valve opens and proportionate fuel-air mixture is sucked in the engine

cylinder. Thus the piston moves from top dead centre (T.D.C.) to bottom dead centre (B.D.C.).

The exhaust valve remains closed throughout the stroke.

COMPRESSION STROKE

In this stroke both the inlet and exhaust valves remain closed during the stroke. The piston

moves towards (T.D.C.) and compresses the enclosed fuel-air mixture drawn. Just

before the end of this stroke the operating plug initiates a spark which ignites the mixture and

combustion takes place at constant pressure.

POWER STROKE OR EXPANSION STROKE

In this stroke both the valves remain closed during the start of this stroke but when the piston

just reaches the B.D.C. the exhaust valve opens. When the mixture is ignited by the spark plug

the hot gases are produced which drive or throw the piston from T.D.C. to B.D.C. and thus the

work is obtained in this stroke.

EXHAUST STROKE

This is the last stroke of the cycle. Here the gases from which the work has been collected

become useless after the completion of the expansion stroke and are made to escape through

exhaust valve to the atmosphere. This removal of gas is accomplished during this stroke. The

piston moves from B.D.C. to T.D.C. and the exhaust gases are driven out of the engine cylinder;

this is also called scavenging.

Theoretical P-V diagram of a four-stroke petrol engine

The four strokes complete one cycle which may repeat again to produce power.

Gudgeon pin

It’s used to connect the piston and the smaller end of the connecting rod. It is also called as piston pin.

Parts of on internal combustion engine

Cylinder, piston, connecting rod, cylinder head, crank shaft etc. carburetor

A carburetor is a device which is used to mix air and petrol in the required proportion before the air fuel mixture is admitted to cylinder.

Cooling systems used for I.C engine

Water cooling systems Air cooling systems

FOUR STROKE DIESEL ENGINE

Working principle of four stroke Diesel engine.

SUCTION STROKE

With the movement of the piston from T.D.C. to B.D.C. during this stroke, the inlet valve opens

and the air at atmospheric pressure is drawn inside the engine cylinder; the exhaust valve

however remains closed. This operation is represented by the line 5-1

COMPRESSION STROKE

The air drawn at atmospheric pressure during the suction stroke is compressed to high pressure

and temperature as the piston moves from B.D.C. to T.D.C. Both the inlet and exhaust valves do

not open during any part of this stroke. This operation is represented by 1-2

POWER STROKE OR EXPANSION STROKE

As the piston starts moving from T.D.C to B.D.C, the quantity of fuel is injected into the hot

compressed air in fine sprays by the fuel injector and it (fuel) starts burning at constant pressure

shown by the line 2-3.

At the point 3 fuel supply is cut off. The fuel is injected at the end of compression stroke but in

actual practice the ignition of the fuel starts before the end of the compression stroke. The hot

gases of the cylinder expand adiabatically to point 4. Thus doing work on the piston.

EXHAUST STROKE

The piston moves from the B.D.C. to T.D.C. and the exhaust gases escape to the atmosphere

through the exhaust valve. When the piston reaches the T.D.C. the exhaust valve closes and the

cycle is completed. This stroke is represented by the line 1-5.

The four-strokes complete one cycle which may repeat again to produce power.

Theoretical p- V diagram of a four-stroke Diesel Engine

Lubrication system

Lubrication system is used to reduce frictional losses between moving parts of

an engine. Why is cooling of an IC engine necessary

To prevent damage to the engine parts such as cylinder walls, cylinder head, etc.at high temperature To improve overall efficiency of an engine To prevent abnormal ignition of air-fuel mixture

TWO STROKE PETROL ENGINE The working principle of 2-Stroke petrol engine is discussed below.

1) 1st Stroke

To start with let us assume the piston to be at its B.D.C. position. The arrangement of the ports is

such that the piston performs two jobs simultaneously. As the piston starts rising from its B.D.C.

position it closes the transfer port and the exhaust port. The charge (mixture, of the air and

petrol) which is already there in the cylinder, as the result of the previous running of the engine

is compressed at the same time with the upward movement of the piston vacuum is created in the

crank case (which is gas tight). As son as the inlet port is uncovered; the fresh change in sucked

in the crank case. The charging is continued until the crank case and the space in the cylinder

beneath the piston is filled with the charge. As the end of third stroke, the piston reached the

T.D.C. position.

2) 2nd

Stroke Slightly before the completion of the compression stroke, the compressed charge is ignited by

means of a spark produced at the spark plug. Pressure is exerted on the crank of the piston due to

the combustion of the piston is pushed in the downward direction producing some useful power.

The downward movement of the will first close the inlet port and then it will compress the

charge already sucked in the crank case.

Just the end of power stroke, the piston uncovered the exhaust port and the transfer port

simultaneously the expanded gases start escaping through the exhaust port and the same time the

fresh charge which is already compressed in the crank case, rushed into the cylinder through the

transfer port and thus the cycle is repeated again.

The fresh charge coming into the cylinder also helps in exhausting the burnt gases out of the

cylinder through the exhaust port. This is known as scavenging.

TWO STROKE DIESEL ENGINE

1st Stroke

As the piston starts rising from its B.D.C. position, it closes the transfer and the exhaust port.

The air which is already there in the cylinder is compressed. At the same time with the

upward movement of the piston, vacuum is created in the crank case. As soon as the inlet

port is uncovered the fresh air is sucked in the crank case. The charging is continued until the

crank case and the space in the cylinder beneath the piston in filled with the air

2

nd Stroke

Slightly before the completion of the compression stroke a very fine spray of diesel is injected

into the compressed air (which is at a very high temperature). The fuel ignites spontaneously.

Pressure is exerted on the crown of the piston due to the combustion of the air and the piston is

pushed in the downward direction producing some useful power. The downward movement of the

piston will first close the inlet port and then it will compress the air already sucked in the crank

case. Just at the end of power stroke, the piston uncovers the exhaust port and the transfer port

simultaneously. The expanded gases start escaping through the exhaust port and at the same time

the fresh air which is already compressed in the crank case, rushes into the cylinder through the

transfer port and thus the cycle is repeated again.

Scavenging

The transfer port is opened and some percentage of air-fuel mixture enters the cylinder to push out the exhaust gasses. In this process some of the fresh charge is lost to the atmosphere which is called scavenging

Distinguish spark ignition and compression ignition engine

SPARK IGNITION ENGINE COMPRESSION IGNITION ENGINE

( SI – ENGINE ) ( CI – ENGINE )

( PETROL – ENGINE ) ( DIESEL – ENGINE )

Compression ratio is 7 - 10 Compression ratio is 15 – 20

Air - fuel mixture is Only air is compressed

compressed

Distinguish 4-stroke and 2- stroke engine

FOUR STROKE ENGINE TWO STROKE ENGINE

There is one power stroke for There is one power stroke for one

two revolution of crankshaft revolution of crankshaft

For the same power, engine size For the same power, engine size is

is large Small

Inlet and exhaust valves are Inlet port , exhaust port and transfer

present port are present

Boiler A boiler is a closed vessel in which steam is produced above atmospheric pressure by the

application of heat.

Tell the Difference between fire tube and water tube boiler

WATER TUBE BOILER FIRE TUBE BOILER

Water pass through the tubes Hot flue gases pass through the

tubes

Less liable to explosion More prone to explosion or

damage of boiler parts

Cochran boiler

COCHRAN BOILER

Simple vertical boilers of the fire tube type boiler in small plants requiring small quantities of

steam and where floor area is limited. The most common applications are steam rollers, pile

drivers, portable hoisting rigs etc. Cochran boiler, as shown, provides an excellent example

of the improved design of vertical, multi-tubular, internally fired natural circulation boiler.

It consists of 1. Boiler shell with hemispherical crown, 2. Furnace, fire box and grate 3. Combustion chamber and flue pipes 4. Smoke box and chimney 5. Connections for boiler mountings and accessories.

CONSTRUCTION AND WORKING The unit consists of a cylindrical shell with a dome shaped top where the space is provided for

steam. The shell is formed of steel plates joined together with rivets. The fuel is burnt on grate in

the furnace provided at the bottom most part of the boiler. Thegrate consists of iron bars which

are arranged with space between them. The spacing allows the air to pass onto the fuel for

combustion. The fire box is hemispherical so that the un burnt fuel, if any, is deflected back to

the grate and complete combustion is achieved.An ash pit is attached beneath the furnace for

collecting ash after regular intervals. The coal, on burning, produces hot flue gases and these hot

products of combustion from the fire box enter through the small flue pipe into the combustion

chamber which is lined with fire bricks on the outer walls of the boiler. The lining prevents the

shell from being damaged due to the overheating. The unburnt fuel is deflected back to the grate

and complete combustion is achieved in combustion chamber where the high temperatures are

maintained. The hot gases passing through the horizontal smoke tubes give their heat to the water and in

doing so convert water into steam which gets accumulated in the upper portion of the shell from

where it can be supplied to the user. Finally the flue gases are discharged to the atmosphere

through the smoke box and the chimney. The smoke box door enables the cleaning and

inspection of the smoke box and fire tubes. Through a manhole provided at the crown of the

shell, a man can enter the boiler for periodic cleaning and maintenance of the boiler. The

Cochran boiler is compact in design and there is good external and internal accessibility. Its

efficiency is up to 70 to 75%.

LOCOMOTIVE BOILER

WORKING

The boiler barrel is cylindrical shell and consists of large number of flue tubes. The barrel

comprise of a rectangular fire box at one end and a smoke box at the other end. The coal is

introduced in fire box through fire hole and is made to burn on the grate. Water is filled into

cylindrical boiler shell up to about ¾ level. Hot gases which are generated as a result of coal

burning rise and get deflected by fixed fire brick lining. The hot flue gases heats water and then

reach the smoke box at the other end. Finally flue gasses pass to atmosphere through short

chimney. The steam produced is stored in steam space and steam dome. A throttle valve is

provided in steam dome. The throttle valve is controlled by regulating rod from outside. For

super heating, steam passes through throttle valve to the super heater.

Power plant

Power plant is an assembly of equipment that produces electrical energy.

Classify different power plant

POWER PLANT BASED ON TYPES

Steam power plant

Non – Renewable source of Diesel power plant

Energy Nuclear power plant

Solar power plant

Hydro power plant

Renewable source of energy Tidal power plant

Wind mill

Geothermal power plant

Ocean thermal energy conversion -

OTEC

Prime mover

A prime mover is a device that is used to convert energy from any natural source into mechanical energy.

Function of economizer

Economizer is mechanical device intended to reduce energy consumption or to perform another useful function such pre-heating a fluid.

THERMAL POWER PLANT we will study about the general layout of a typical power plant. There are four main circuits in any thermal power plant and these are Coal & Ash Circuit

This circuit deals mainly with feeding the boiler with coal for combustion purposes and taking

care of the ash that is generated during the combustion process and includes equipment that is

used to handle the transfer and storage of coal and ash.

Air & Gas Circuit

We know that air is one of the main components of the fire triangle and hence necessary for

combustion. Since lots of coal is burnt inside the boiler it needs a sufficient quantity of air which is

supplied using either forced draught or induced draught fans. The exhaust gases from the combustion

are in turn used to heat the ingoing air through a heat exchanger before being let off in the

atmosphere. The equipment which handles all these processes fall under this circuit.

Feed Water & Steam Circuit

This section deals with supplying of steam generated from the boiler to the turbines and to handle the

outgoing steam from the turbine by cooling it to form water in the condenser so that it can be reused

in the boiler plus making good any losses due to evaporation etc.

Cooling Water Circuit

This part of the thermal power plant deals with handling of the cooling water required in the system.

Since the amount of water required to cool the outgoing steam from the boiler is substantial, it is

either taken from a nearby water source such as a river, or it is done through evaporation if the

quantity of cooling water available is limited.

Advantages

They can respond to rapidly changing loads without difficulty

A portion of the steam generated can be used as a process steam in different industries

Steam engines and turbines can work under 25 % of overload continuously Fuel used is

cheaper

Cheaper in production cost in comparison with that of diesel power stations

Disadvantages

Maintenance and operating costs are high

Long time required for erection and putting into action

A large quantity of water is required

Great difficulty experienced in coal handling

Presence of troubles due to smoke and heat in the plant

Unavailability of good quality coal

Maximum of heat energy lost

Problem of ash removing

NUCLEAR POWER PLANT

The main principle work of nuclear power reactor is to produce electricity. It is done by the use of

released energy as heat to make steam for generating electricity. The main parts of nuclear power plant

are described as below.

1. Fuel- The isotope of Uranium U-235 is used as the basic nuclear fuel. It is used inform of

pallets. The uranium oxide (UO2) pallets are arranged in tubes known as

fuel rods. These pellets are backed at high temperature up to 1400°C. The pellets are inserted

into zirconium alloy thin tubes or stainless steel tubes to get the fuel rods. Thus the fuel rods

are arranged to form the fuel assemblies in reactor core.

2. Moderator and coolant- Water or graphite is used as a moderator. This ismaterial of core

which uses to slow down the speed of released neutrons that can be undergo other fission.

Water is also used as coolant. It circulates from the core to transfer the heat.

3. Control rods- As in the nuclear fission reaction, the nuclear explosion also cantakes place if

the reaction is not controlled. So the control rods control the rate of nuclear reaction to avoid

the nuclear explosion. The neutron-absorbing material like cadmium, hafnium or boron etc is

used to make the control rods. The rate of nuclear reaction can be increased or decreased by

inserting or withdrawn the control rods from the core according to the requirement of process.

4. Pressure vessel- The pressure vessel is a robust steel vessel that contains thereactor core and

moderator or coolant. It can be also in the form of pressure tubes. If the tubes are used then

these are series of tubes that holds the fuel.

5. Steam generator- The cooling system contains the steam generator. The heatfrom the reactor

comes in the steam generator from the primary coolant and then it is used to make steam for

the turbine.

6. Containment- It works as protector. It protects the reactor form outside intrusionand the

effects of harmful radiation. This is a meter thick concrete and steel structure around the

reactor core.

WORKING

In the nuclear power plant, the released heat of a nuclear fission reaction is used to turns a steam

turbine and it produce electric power.

The nuclear fission of uranium-235 occurs by bombardment of neutrons on nuclear fuel uranium

and thus the decaying process takes place.

The reaction does not produce pollutants or hazardous smoke of green house gases like carbon

dioxide.

The reactor is able of generating huge amount of energy by using negligible amount of fuel.

The waste of nuclear reactor is negligible.

It is one of the most reliable sources of energy. Nuclear

power is reliable.

Disadvantages

Although the waste is very small but it is more dangerous than the by products of many other

fossil fuels. The residue needs to be buried deep down in earth for thousands of year so the

radioactivity can diminish. It should also be kept safe from earth quake, floods and terrorist

attack.

The source of energy is although reliable but to maintain the safety of the plant is very expensive.

In case of any accident, the nuclear power station can result into a disaster.

The absorption of neutrons by the atom of nuclear fuel uranium causes the splitting of uranium

into smaller atoms.

The uranium pellets are arranged as long rods. These rods are collected together to form bundles.

The bundles are dropped in water of a pressure vessel.

The control rods prevent the overheating by absorbing neutrons to control the rate of nuclear

reaction. If more energy is required then the rods are lifted out from the bundle to absorb few

electrons.

The control rods can be lowered into the uranium bundle for reducing the level of heat. The heat

from the fission of uranium bundle turns the water in to steam.

This steam turns a turbine and thus generator starts spin and produces the electric energy.

As the high energy neutrons are emitted so these are directly absorbed by the other uranium atom

in fast reactors.

This tendency is greater in isotope Uranium-238 than Uranium-235. This is the main reason to

use much larger fraction of U-235 is used as fuel in fast reactors. While in slow reactors or

thermal reactors, the speed of produced neutrons is in control so that neutrons are absorbed by the

correct isotope of uranium-235.

Advatages

The nuclear energy is no doubt a very useful source to meet the energy requirement but it also create

issues of mishandling. However, energy is the backbone of our society and there is no way to escape

the every increasing need. It is also suggested that the states that use nuclear reactors to fulfillthere

needs must behave responsibly and discard the wastage properly.

Distinguish nuclear power plant & thermal power plant

NUCLEAR POWER PLANT THERMAL POWER PLANT

This plant is more economical in Not economical in areas that are

areas remote from coal fields

That are remote

No fuel transportation , handling Coal is to be transported, stored

and storage problems and handled

No ash disposal Ash disposal is a problem

UNIT-II

Chapter-1

MANUFACTURING PROCESSES Manufacturing Processes

Casting processes Forming processes Machining processes &Joining processes

Metal Forming

It is a method of deforming metals by applying force without any removal of materials.

Hot Working

Hot working is defined as the forming of metals above their recrystallization temperature. (600°-700 °C) Example of hot working of metals: Forging, Extrusion, Hot rolling etc.

Cold Working

Cold working is the forming of metals below their recrystallization temperature. (600°-below)

Example of hot working of metals: Shearing, Drawing, Squeezing, Bending etc. Rolling Process

It is a metal forming process to get plates, sheets, and various sections of rods by passing the metal between rotating rollers.

ROLLING PROCESS

Rolling is a process of reduction of the cross-sectional area or shaping a metal piece through

the deformation caused by a pair of rotating in opposite directions metal rolls.

A scheme of rolling process is shown in the picture.

The gap between the rotating rolls is less than the thickness of the entering bar H0 therefore a friction force is necessary in order to bite the bar and to pull it through the rolls. A metal bar passing through the rotating rolls is squeezed, and it elongates while its cross section area decreases.

The amount of deformation “R” achieved in a flat rolling operation (thickness reduction) is determined by the relationship: R = 100% * (H – H0)/H0

A machine used for rolling metal is called rolling mill. A typical rolling mill consists of a pair of rolls driven by an electric motor transmitting a torque through a gear and pair of cardans. The rolls are equipped with bearings and mounted in a stand with a screw-down mechanism. A force applied to the rolls in vertical direction is called roll separating force. A rolling mill is characterized by the maximum values of its roll separating force and the torque.

The maximum amount of deformation (thickness reduction) which may be achieved in a single rolling pass is determined by the maximum roll separating force, maximum torque, work roll diameter, friction coefficient and mechanical strength of the rolled material and its width.

Low roll diameter results in low roll contact area and consequently in low absolute value of the roll separating force and the torque required for achieving a certain thickness reduction. However such rolls are susceptible to bending and causing non-uniform widthwise strip thickness distribution (convex crown). Complex rolling mill designs employing back-up rolls are used to diminish the bending effect

TYPES

Hot rolling is a rolling operation carried out at a temperature exceeding the recrystallization temperature and permitting large amount of deformation.

Cold rolling is a rolling operation carried out at room temperature. Cold rolling is commonlyconducted after hot rolling when good surface quality and low thickness tolerance are needed. Cold rolling causes material strengthening and may be followed by annealing.

Forging

It is a forming process where the product of desired shape and size is obtained by pressing or hammering.

FORGING PROCESS Forging is a compressive metal forming process, involving shaping a metal piece by hammer, press or rolls.

Hammer forging (drop forging) is forming a preheated work piece by using impactenergy of the falling hammer forcing the metal to fill the space between the punch (a part attached to the

hammer) and the forging die (a part attached to the anvil).

Press forging is forming a preheated workpiece by using a force created by ahydraulically driven ram causing the metal to be squeezed into the die cavity by the static pressure.

Press forging achieves more uniform internal structure due to transmitting deformation to the interior layers of the work piece. This effect is particularly important when large shafts or other thick parts are forged.

Upset forging is a forging operation which is employed for manufacturing head ofbolts, valves, artillery shells and other parts where increase of cross section dimensions of the workpiece is desired.

Roll forging is a forging operation involving reduction of the workpiece diameter (withincrease of its length) by rolling it between two grooved rolls rotating at the same rotating direction.

Extrusion

It is a process in which the hot metal in plastic state is plunged through the hole of required shape to get different sections of rod

EXTRUSION PROCESS

The process of extrusion is simply forcing a billet of metal through a shaped die to produce a continuous length of constant section similar to the die profile. There are two basic extrusion processes

Direct extrusion Indirect extrusion.

Direct extrusion is by far the most widely used process. Indirect extrusion more efficient and produced higher quality products.

Extrusion presses are generally hydraulically operated and the process is generally completed in a horizontal elevation. An extrusion press can have a capacity of over 200 MN for extruding stiffer metals such as titanium or steel. Hot metal extrusion involves preheating the billet prior to extrusion to reduce the work required to extrude the section.

The term extrusion is usually applied to both the process, and the product obtained, when a hot cylindrical billet of aluminum is pushed through a shaped die (forward or direct extrusion, see Figure. The resulting section can be used in long lengths or cut into short parts for use in structures, vehicles or components. Also, extrusions are used for the starting stock for drawn rod, cold extruded and forged products. While the majority of the many hundreds of extrusion presses used throughout the world are covered by the simple description given above it should be noted that some presses accommodate rectangular shaped billets for the purpose of producing extrusions with wide section sizes. Other presses are designed to push the die into the billet. This latter modification is usually termed "indirect" extrusion.

Wire Drawing

It is a deforming process in which the metal rod or wire with larger diameter is pulled through a die hole to produce a wire of smaller diameter

DRAWING PROCESS

It is a process of cold forming a flat blank of sheet metal into a hollow vessel without much

wrinkling, trimming, or fracturing. The process involves forcing the sheet metal blank into a die cavity

with a punch. The punch exerts sufficient force and the metal is drawn over the edge of the die

opening and into the die as shown in fig. In forming a cup, however, the metal goes completely into

the die.

Fig. Drawing operation.

Fig. Drawing operation.

The metal being drawn must possess a combination of ductility and strength so that it does not rupture in the critical area (where the metal blends from the punch face to the vertical portion of the punch). The metal in this area is subjected to stress that occurs when the metal is pulled from the flat blank into the die.

OPERATION

A setup similar to that used for blanking is used for drawing with the difference that the punch and die are given necessary rounding at the corners to permit smooth flow of metal during drawing. The blank of appropriate dimensions is place within the guides on the die plate. The punch descends slowly on the blank and metal is drawn into the die and the blank is formed into the shape of cup as punch reaches the bottom of the die. When the cup reaches the counter – bored portion of the die, the top edge of the cup formed around the punch expands a bit due to the

spring back. On the return stroke of the punch, the cup is stripped off the punch by this counter – bored

portion.

The term shallow drawing is used when the height of cup formed is less than half its diameter. When drawing deeper cup (height greater that ½ diameter) the chances of excessive wrinkle formation at the edges of blank increases. To prevent this, a blank holder is normally provided, see Fig. As the drawing process proceeds the blank holder stops the blank from increasing in thickness beyond a limit and allows the metal to flow radially. The limiting thickness is controlled by the gap between the die and the blank holder, or by the spring pressure in the case of a spring loaded blank holder.

Some lubricant is generally used over the face of the blank to reduce friction and hence drawing load.

Welding Process

It is defined as the process of joining two similar or dissimilar materials

Any Four Types Of Welding

Gas welding processes Arc welding processes Soldering Brazing

The Block Diagram Of Gas Welding

Clean and Position and Pass the high Metals are

prepare the clamp the temperature joined along

edges to be plates gas along the edges

welded edges

Arc welding with neat sketch

Welding is a process which is in used to join any two metals. In ARC welding two metals are joined together using electrical current. The electric current produces the heat needed for welding. The electric current passes through the MMA welding machine through the torch and electrode to the work piece. An arc is created around 6000 degrees F or more. This melts the filler rod and the metal that is being welded and a weld pool is developed. A flux is formed around the weld and this provides stability to the arc and gives protection from weld contamination. This flux is then removed by using a wire brush or a chipping hammer. The electric power source used for this is AC/DC current.

Arc welding is a welding process, in which heat is generated by an electric arc struck between an electrode and the work piece. Electric arc is luminous electrical discharge between two electrodes through ionized gas.

Any arc welding method is based on an electric circuit consisting of the following parts

Power supply (AC or DC) Welding electrode Work piece

Welding leads (electric cables) connecting the electrode and work piece to the power supply.

Electric arc between the electrode and work piece closes the electric circuit. The arc temperature may reach 10000°F (5500°C), which is sufficient for fusion the work piece edges and joining them.

When a long join is required the arc is moved along the joint line. The front edge of the weld pool melts the welded surfaces when the rear edge of the weld pool solidifies forming the joint.

WORKING PRINCIPLE

Arc welding is performed by striking an arc between a coated-metal electrode and the base metal. Once the arc has been established, the molten metal from the tip of the electrode flows together with

the molten metal from the edges of the base metal to forma sound joint. This process is known as fusion.

The coating from the electrode forms a covering over the weld deposit, shielding it from contamination Shielded metal arc welding (SMAW). Therefore the process is called shielded metal arc welding. The main advantages of shielded metal arc welding are that high-quality welds are made rapidly at a low cost.

The welding electrode (the stick or rod) has an inner core of metal similar to the material that is being welded. This core also has a diameter that is proportional to the material – as the work-piece gets thicker, so too should the rod. The inner of the rod is surrounded by a welding flux. When the molten material solidifies, the flux forms a separate layer on top that can later be knocked away with the chipping hammer.

When a filler metal is required for better bonding, filling rod (wire) is used either as outside material fed to the arc region or as consumable welding electrode, which melts and fills the weld pool. A chemical composition of filler metal is similar to that of work piece.

Molten metal in the weld pool is chemically active and it reacts with the surrounding atmosphere. As a result weld may be contaminated by oxide and nitride inclusions deteriorating its mechanical properties. Neutral shielding gases (argon, helium) and/or shielding fluxes are used for protection of the weld pool from atmospheric contamination. Shields are supplied to the weld zone in form of a flux coating of the electrode or in other forms.

Welding Rods

In addition to the differences in diameter described above, welding rods vary in other characteristics. (Despite “general purpose” welding rods being sold at every hardware store, in fact rods should always be matched to the application.) The flux on welding rods serves these functions:

Provides a gas shield Gives a steady arc by providing a „current bridge‟

Cleans the surface and slows the cooling of the weld Introduces appropriate alloys into the weld

Specific electrodes are available for welding:

Mild steel Cast iron

Stainless steel Copper, bronze, brass, etc

High tensile steel

ADVANTAGES

Strong and tight joining

Cost effectiveness

Simplicity of welded structures design Welding processes may be mechanized and automated.

DISADVANTAGES

Internal stresses, distortions and changes of micro-structure in the weld region Harmful effects: light, ultra violate radiation, fumes, high temperature.

APPLICATIONS

Buildings and bridges structures Automotive, ship and aircraft constructions

Pipe lines Tanks and vessels

Rairoads Machinery elements.

Illustrate Gas welding with neat sketch.

Metal joining process in which the ends of pieces to be joined are heated at their interface by producing coalescence with one or more gas flames (such as oxygen and acetylene), with or without the use of a filler metal. Gas Welding is a welding process utilizing heat of the flame from a welding torch. The torch mixes a fuel gas with Oxygen in the proper ratio and flow rate providing combustion process at a required temperature. The hot flame fuses the edges of the welded parts, which are joined together forming a weld after Solidification.

The flame temperature is determined by a type of the fuel gas and proportion of oxygen in the combustion mixture: 4500°F - 6300°F (2500°C - 3500°C). Depending on the proportion of the fuel gas and oxygen in the combustion mixture, the flame may be chemically neutral (stoichiometric content of the gases), oxidizing (excess of oxygen), and carburizing (excess of fuel gas).

Filler rod is used when an additional supply of metal to weld is required. Shielding flux may be used if protection of weld pool is necessary. Most of commercial metals may be welded by Gas Welding excluding reactive metals (titanium, zirconium) and refractory metals (tungsten, molybdenum).

Gas Welding equipment:

Fuel gas cylinder with pressure regulator Oxygen cylinder with pressure regulator

Welding torch Blue oxygen hose

Red fuel gas hose Trolley for transportation of the gas cylinders

Oxyacetylene gas welding is commonly used to permanently join mild steel. A mixture of oxygen and acetylene burns as an intense / focused flame, at approximately 3,500 degrees centigrade. When the flame comes in contact with steel, it melts the surface forming a molten pool, allowing welding to take place. Oxyacetylene can also be used for brazing, bronze welding, forging / shaping metal and cutting. This type of welding is suitable for the prefabrication of steel sheet, tubes and plates.

Flame temperature differs according to the type of oxygen and fuel to fuel ratio. Velocity of flame travel through adjacent unburned gas is called as flame propagation rate. It affects the size and temperature of the primary flame. This also influences the maximum velocity at which gases might be made to flow from the torch tip without causing a flame standoff or backfire. In case of flame standoff combustion occur some distance from the torch tip instead of right at the tip whereas in case of backfire there is recession of flame into the torch tip.

The oxyfuel procedure requires cylinder of oxygen and fuel gas (Figure 8). Each cylinder is fixed along a regulator and two pressure gauges (one for the pressure in cylinder and the other one for the pressure of gas being fed to the torch).

Natural gas/methane, butane, propane or hydrogen might be used with oxygen but oxy acetylene welding (OAW) in which acetylene is utilized with oxygen is most broadly used welding method because of its high flame temperature. The oxyacetylene flame might also be utilized for all types of brazing processes. Oxyacetylene flame might be carbursing (excess acetylene with oxygen) that is blue with a red and orange end, an oxidising frame (excess of oxygen) resultant in short hoisy, hissing inner

cone. Oxidizing flame tends to burn the metal being welded. However the neutral flame (perfect mixture of oxygen & acetylene) which has a quiet, blue white inner cone is best suitable for most welding procedure.

Brazing

Brazing is a joining process wherein metals are bonded together using a filler metal with a melting (liquids) temperature greater than 450°C(840 °F), but lower than the melting temperature of the base metal. Filler metals are generally alloys of silver (Ag), aluminum (Al), gold Au), copper (Cu), cobalt (Co) or nickel (Ni)ss

Soldering

Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal (solder) into the joint, the filler metal having a lower melting point than the work piece.

The Block Diagram Of Brazing And Soldering.

Clean and prepare Position and Melt the filler

the edges to be clamp the plates metal and fill the

joined gaps to be joined

Soldering and brazing in a joining process.

SOLDERING Soldering is a method of joining two metal work pieces by means of a third metal (solder) ata

relatively low temperature, which is above the melting point of the solder but below the melting point of either of the materials being joined. Flow of the molten solder into the gap between the work pieces is driven by the capillary force. The solder cools down and solidifies forming a joint.

The parent materials are not fused in the process. Soldering is a joining process that occurs at temperatures below 450 °C (842 °F). It is similar to brazing in the fact that filler is melted and drawn into a capillary to form a join, although at a lower temperature. Because of this lower temperature and different alloys used as fillers, the metallurgical reaction between filler and work piece is minimal, resulting in a weaker joint.

Soldering is similar to Brazing. The difference is in the melting point of the filler alloy solders melt at temperatures below 840°F (450°C); brazing filler materials melt at temperatures above this point. The difference between soldering and welding processes is more sufficient: in the welding processes edges of the work pieces are either fused (with or without a filler metal) or pressed to each other without any filler material; soldering joins two parts without melting them but through a soft low melting point

solder. Soldering joints have relatively low tensile strength of about 10000 psi (70 MPa).

Soldering methods

Hand soldering Iron soldering Torch soldering Wave soldering Reflow soldering

ADVANTAGES

Low power is required Low process temperature

No thermal distortions and residual stresses in the joint parts Microstructure is not affected by heat

Easily automated process Dissimilar materials may be joined High variety of materials may be joined

Thin wall parts may be joined Moderate skill of the operator is required

DISADVANTAGES

Careful removal of the flux residuals is required in order to prevent corrosion Large sections cannot be joined Fluxes may contain toxic components

Soldering joints cannot be used in high temperature applications Low strength of joints.

BRAZING

Brazing is a method of joining two metal work pieces by means of a filler material at atemperature above its melting point but below the melting point of either of the materials being joined. Flow of the molten filler material into the gap between the work pieces is driven by the capillary force. The filler material cools down and solidifies forming a strong metallurgical joint, which is usually stronger than the parent (work piece) materials. The parent materials are not fused in the process.

Brazing is a joining process in which a filler metal is melted and drawn into a capillary formed by the assembly of two or more work pieces. The filler metal reacts metallurgically with the work piece(s) and solidifies in the capillary, forming a strong joint.

Unlike welding, the work piece is not melted. Brazing is similar to soldering, but occurs at temperatures in excess of 450 °C (842 °F). Brazing has the advantage of producing less thermal stresses than welding, and brazed assemblies tend to be more ductile than weldments because alloying elements cannot segregate and precipitate

Brazing is similar to Soldering. The difference is in the melting point of the filler alloy brazing filler materials melt at temperatures above 840°F (450°C); soldering filler materials (solders) melt at temperatures below this point.

The difference between brazing and welding processes is more sufficient in the welding processes edges of the work pieces are either fused (with or without a filler metal) or pressed to each other without any filler material; brazing joins two parts without melting them but through a fused filler metal.

Brazing filler materials

Copper filler alloys: BCuP-2 (Cu-7P), BCuP-4 (Cu-6Ag-7P). Used for brazing Copper alloys, steels, Nickel alloys. Aluminum filler alloys: Al-4Cu-10Si, Al-12Si, Al-4Cu-10Si-10Zn, 4043 (Al-5.2Si), 4045 (Al-10Si). Used for brazing Aluminum alloys. Magnesium filler alloys: BMg-1 (Mg-9Al-2Zn), BMg-2 (Mg-12Al-5Zn). Used for brazing Magnesium alloysNickel filler alloys: BNi-1 (Ni-14Cr-4Si-3.4B-0.75C), BNi-2 (Ni-7Cr-4.5Si-3.1B-3Fe), BNi-3 (Ni-4.5Si-3.1B). Used for brazing Nickel alloys, cobalt alloys, Stainless steels. Silver brazing alloys: BAg-4 (40Ag-30Cu-28Zn-2Ni), BAg-5 (45Ag-30Cu-25Zn), BAg-6 (50Ag-34Cu-16Zn), BAg-7 (56Ag-22Cu-17Zn-5Sn). Used for most of metals and alloys except aluminum and magnesium alloys.

Brazing methods

Torch brazing utilizes a heat of the flame from a torch. The torch mixes a fuel gas with Oxygen or air in the proper ratio and flow rate, providing combustion process at a required temperature. Furnace brazing uses a furnace for heating the work pieces.

Vacuum brazing is a type of furnace brazing, in which heating is performed invacuum. Induction brazing utilizes alternating electro-magnetic field of high frequency forheating the work pieces together with the flux and the filler metal placed in the joint region. Resistance brazing uses a heat generated by an electric current flowing through thework pieces. Dip brazing is a brazing method, in which the work pieces together with the fillermetal are immersed into a bath with a molten salt. The filler material melts and flows into the joint. Infrared brazing utilizes a heat of a high power infrared lamp.

ADVANTAGES

Low thermal distortions and residual stresses in the joint parts Microstructure is not affected by heat

Easily automated process Dissimilar materials may be joined

High variety of materials may be joined Thin wall parts may be joined

Moderate skill of the operator is required

DISADVANTAGES

Careful removal of the flux residuals is required in order to prevent corrosion No gas shielding may cause porosity of the joint Large sections cannot be joined

Fluxes and filler materials may contain toxic components Relatively expensive filler materials

Moulding Moulding refers to the process of making a mould by using a moulding box, sand and other moulding

tools. It also refers to the casting

Pattern

A pattern is a model of the object to be cast.

Illustrate The Different Types Of Pattern In A Casting Process

PATTERN In sand casting a few different types of patterns may be used in the process. Solid Pattern This is a one piece pattern representing the geometry of the casting. It is an easy pattern to manufacture, but determining the parting line between cope and drag is more difficult for the foundry worker. Split Pattern

The split pattern is comprised of two separate parts that when put together will represent the geometry of the casting. When placed in the mold properly the plane a which the two parts are assembled should coincide with the parting line of the mold. This makes it easier to manufacture a pattern with more complicated geometry. Also mold setup is easier since the patterns placement relative to the parting line of the mold is predetermined.

Match Plate Pattern

The match plate pattern is typically used in high production industry runs for casting manufacture. A match plate pattern is a two piece pattern representing the casting, and divided at the parting line, similar to the split pattern. In the match plate pattern, however, each of the parts are mounted on a plate. The plates come together to assemble the pattern for the casting process. The match plate pattern is more proficient and makes alignment of the pattern in the mold quick and accurate.

Cope and Drag Pattern

The cope and drag pattern is also typical in casting manufacture for high production industry runs. The cope and drag pattern is the same as the match plate pattern in that it is a two piece pattern representing the casting and divided at the parting line. Each of the two halves are mounted on a plate for easy alignment of the pattern and mold. The difference between the cope and drag pattern and the match plate pattern is that in the match plate pattern the two halves are mounted together, where as in the cope and drag pattern the two halves are separate. The cope and drag pattern enables the cope section of the mold, and the drag section of the mold to be created separately and latter assembled before the pouring of the casting.

PATTERN MATERIAL

Some materials used for making patterns are:

Wood Metals and alloys Plastic Plaster of Paris Plastic Rubbers Wax and resins.

To be suitable for use, the pattern material should be:

Easily worked, shaped and joined Light in weight

Strong, hard and durable Resistant to wear and abrasion Resistant to corrosion, and to chemical reactions Dimensionally stable and unaffected by variations in temperature and humidity

THE CUPOLA FURNACE

A cupola is a vertical cylindrical furnace equipped with a tapping spout neat its base. Cupolas

are used only for melting cast irons, and although other furnaces are also used the largest tonnage of cast iron is melted in cupolas.

It consists of a large shell of steel plate lined with refractory. The charge, consisting or iron, Coke, flux

and possible alloying elements, is loaded through a charging door located less than halfway up the

height of the cupola.

The iron is usually a mixture of pig iron and scrap (including risers, runners, and sprues left over from previous castings). Coke is the fuel used to heat the furnace. Forced air is introduced through openings near the bottom of the shell for combustion of the coke.

The flux is a basic compound such as limestone that reacts with coke ash and other impurities to form slag. The slag serves to cover the melt, protecting it from reaction with the environment inside the cupola and reducing heat loss. As the mixture is heated and melting of the iron occurs, the furnace is periodically tapped to provide liquid metal for the pour.

CONSTRUCTION

A cupola or cupola furnace is a melting device used in foundries that can be used to melt cast iron,ni-resist iron and some bronzes. The cupola can be made almost any practical size. The size of a cupola is expressed in diameters and can range from 1.5 to 13 feet (0.5 to 4.0 m).

[1]

The overall shape is cylindrical and the equipment is arranged vertically, usually supported by four legs. The overall look is similar to a large smokestack.

The bottom of the cylinder is fitted with doors which swing down and out to 'drop bottom'. The top where gases escape can be open or fitted with a cap to prevent rain from entering the cupola. To control emissions a cupola may be fitted with a cap that is designed to pull the gases into a device to cool the gases and remove particulate matter.

The shell of the cupola, being usually made of steel, has refractory brick and plastic

[note 1] refractory

patching material lining it. The bottom is lined in a similar manner but often a clay and sand mixture ("bod") may be used, as this lining is temporary.Finely divided coal ("sea coal") can be mixed with the clay lining so when heated the coal decomposes and the bod becomes slightly friable, easing the opening up of the tap holes.

[3] The bottom lining is compressed or 'rammed' against the bottom doors.

Some cupolas are fitted with cooling jackets to keep the sides cool and with oxygen injection to make the coke fire burn hotter.

OPERATION

The furnace is filled with layers of coke and ignited with torches. Some smaller cupolas may be

ignited with wood to start the coke burning. When the coke is ignited, air is introduced to the coke bed through ports in the sides called tuyeres.

When the coke is very hot, solid pieces of metal are charged into the furnace through an opening in the top. The metal is alternated with additional layers of fresh coke. Limestone is added to act as a flux. As the heat rises within the stack the metal is melted. It drips down through the coke bed to collect in a pool at the bottom, just above the bottom doors. During the

melting process a thermodynamic reaction takes place between the fuel and the blast air. The carbon in the coke combines with the oxygen in the air to form carbon monoxide. The carbon monoxide further burns to form carbon dioxide.

Some of the carbon is picked up by the falling droplets of molten metal which raises the carbon content of the iron. Silicon carbide and ferromanganese briquettes may also be added to the charge materials. The silicon carbide dissociates and carbon and silicon enters into the molten metal. Likewise, the ferromanganese melts and is combined into the pool of liquid iron in the 'well' at the bottom of the cupola. Additions to the molten iron such as ferromanganese, ferrosilicon, Silicon carbide and other alloying agents are used to alter the molten iron to conform to the needs of the castings at hand.

After the cupola has produced enough metal to supply the foundry with its needs, the bottom is opened, or 'dropped' and the remaining materials fall to the floor between the legs. This material is allowed to cool and subsequently removed. The cupola can be used over and over. A 'campaign' may last a few hours, a day, weeks or even months.

When the operation is over, the blast is shut off and the prop under the bottom door is knocked down so that the bottom plates swing open. This enables the cupola remains to drop to the floor or into a bucket. They are then quenched and removed from underneath the cupola.

CUPOLA ZONES

Combustion or Oxidizing zone

It is the zone where combustion takes place. It extends from the top of the tuyeres to a surface boundary below which all the Oxygen of air is consumed by combustion, chemical reaction that takes place in the zone is

C(coke) + 02 (from air) -> C02 + Heat The temperature in this zone is about 1800°C.

Reducing zone

It extends from the top of the combustion zone to the top of the initial coke bed. The CO2 produced in the combustion zone moves up and is reduced to CO. The temperature also drops to 1650°C.

C02 + C2 -» CO – Heat

Preheating zone

It includes all the layers of cupola charges placed above the melting zone to the top of the last charge. The layers of charges are heated by the out-going gases. The temperature in the zone may be up to 1050°C.

Stack:

It is the zone beyond the pre-heating zone, through which the hot gases go to the atmosphere

The Different Tools Used In Moulding Process

Any four moulding tools in a casting process.

Moulding board Shovel Riddle Rammer Trowels

Types Of Moulding

Bench moulding Floor moulding Pit moulding Machine moulding Green sand moulding Dry sand moulding Plaster moulding Carbon-di-oxide moulding Loam sand moulding

Green Sand Green sand is a special type of sand used to make mould. The sand contains binders water and addit

PREPARATION OF GREEN SAND MOULDING

First the moulding board is cleaned by a brush and kept on the table.

Inside walls of the drag are cleaned thoroughly and the drag is kept centrally on the moulding board. The lower half of the pattern is cleaned and kept centrally inside the drag.

Now, green sand is brought by a shovel and filled to the top level of the drag box. With the rammer, the sand is packed tightly inside the drag box around the pattern and side walls. Excessive sand is leveled off with a strike off bar and vent holes are made.

Now the drag with pattern and packed sand is turned upside down and placed firmly on the moulding board. Now the top surface of the drag box shows sand with the pattern inside.

Now dry sand or parting sand is sprinkled on and around the pattern. This is done to avoid the sticking of sand at the parting surface. Now, preparation of one half of the moulding box (drag) is over.

Now, the top half of the moulding box (cope) is taken and inside walls are cleaned thoroughly.

The cope is placed directly above the drag and aligned properly with the help of the dowel pins.

Now the top half of the pattern is placed inside the cope box directly above the bottom half of the pattern at the parting line.

Other tools like sprue pin, runners, risers are kept at correct positions inside the cope box

Now the cope is filled with green sand and rammed tightly and excessive sand is leveled off with a stike off bar. Vent holes are made with a vent wire. Now the preparation of the cope box is over. Now the cope and drag are separated to remove the pattern from the sand cavity with the help of draw spike. Other tools like runner, riser, sprue pin are also removed. Now the cope is fitted again on the top of the drag and the molten metal should be poured through the sprue hole. The metal will go through the sprue hole to the runner to the gate and finally to mould cavity. If the molten metal is poured excessively, it will come through the riser outside.

.

CHAPTER-III

MACHINING OPERATIONS

Types Of Machining Processes

The different types of machining process are turning, shaping, drilling, milling, boring, grinding etc.

Types Of Tool

Single point cutting tool Multi point cutting tool

Types Of Cutting Tool Materials

Carbon tool steel High speed steel Diamond Cemented carbides

Types Of Lathe

Speed lathe Center lathe or engine lathe Bench lathe Tool room lathe Turret and capstan lathe Special purpose lathe Copying lathe

Parts Of Lathe

Bed Head stock Tail stock Carriage Tool post

LATHE WITH NEAT SKETCH.

A lathe is a machine tool which rotates the workpiece on its axis to perform various

operations such as cutting, sanding, knurling, drilling, or deformation, facing, turning, with tools that are applied to the work piece to create an object which has symmetry about an axis of rotation.

Lathes are used in woodturning, metalworking, metal spinning, Thermal spraying/ parts reclamation, and glass-working. Lathes can be used to shape pottery, the best-known design being the potter's wheel. Most suitably equipped metalworking lathes can also be used to produce most

solids of revolution, plane surfaces and screw threads or helices. Ornamental lathes can produce three-dimensional solids of incredible complexity. The material can be held in place by either one or two centers, at least one of which can be moved horizontally to accommodate varying material lengths. Other work-holding methods include clamping the work about the axis of rotation using a chuck or collet, or to a faceplate, using clamps or dogs.

COMPONENTS OF LATHE

Bed:

Usually made of cast iron. Provides a heavy rigid frame on which all the main components

are mounted.

Headstock:

Mounted in a fixed position on the inner ways, usually at the left end. Using a chuck, it

rotates the work.

Gearbox: Inside the headstock, providing multiple speeds with a geometric ratio by moving levers.

Spindle:

Hole through the headstock to which bar stock can be fed, which allows shafts that are upto

2 times the length between lathe centers to be worked on one end at a time.

Chuck:

3-jaw (self centering) or 4-jaw (independent) to clamp part being machined. Allows the

mounting of difficult work pieces that are not round, square or triangular.

Tailstock:

Fits on the inner ways of the bed and can slide towards any position the headstock to fit the

length of the work piece. An optional taper turning attachment would be mounted to it.

Carriage:

Moves on the outer ways. Used for mounting and moving most the cutting tools.

Cross Slide:

Mounted on the traverse slide of the carriage, and uses a hand wheel to feed tools into the

workpiece.

The operations performed on a lathe with neat sketch.

The lathe on which you will work is a machine used to cut metal. The spindle carrying the

work is rotated whilst a cutting tool, which is supported in a tool post, is made to travel in a certain

direction depending on the form of surface required. If the tool moves parallel to the axis of the

rotation of the work a cylindrical surface is produced as in Fig 2 (a) , whilst if it moves at right

angles to this axis it produces a flat surface as in Fig 2 (b).

Figure 2a. Producing a

Figure 2b. Producing a Flat Surfac Cylindrical Surface

The lathe can also be used for the purposes shown in Fig 2c, 2d, 2e and 2f.

Figure 2c. Taper Turning Figure 2d. Parting Off / Under Cutting

Figure 2e. Radius Turning Attachment Figure 2f. Drilling on a Lathe Tool Post:

To mount tool holders in which the cutting bits are clamped.

Compound Rest:

Mounted to the cross slide, it pivots around the tool post.

Feed Rod:

Has a keyway, with two reversing pinion gears, either of which can be meshed with the

mating bevel gear to forward or reverse the carriage using a clutch.

Functions Of Carriage In A Lathe

The carriage is used for giving various movements to the tool by hand or power. The carriage has the following parts.

Saddle Cross slide Compound rest Tool post Apron

ANY FOUR OPERATIONS PERFORMED ON LATHE

Straight turning Facing Chamfering Knurling

TELL WHY COOLANT IS USED WHILE MACHINING A PART IN A LATHE.

Reduce the heat Prepare chip remove

To increase the life of tool To reduce wear & tear To avoid the noise

Types Of Milling Machine

Horizontal milling machine Vertical milling machine Universal milling machine

Up Milling

In up milling process, the work piece is feed in the opposite direction as that of the cutter’s tangential velocity

Down Milling

In down milling process, the work piece is feed in the same direction as that of the cutter’s tangential velocity.

THE HORIZONTAL MILLING MACHINE.

The Horizontal Milling Machine is a very robust and sturdy machine. A variety of cutters are available to removed/shape material that is normally held in a strong machine vice. This horizontal miller is used when a vertical miller is less suitable. For instance, if a lot of material has to be removed by the cutters or there is less of a need for accuracy - a horizontal milling machine is chosen.

The cutter can be changed very easily. The arbor bracket is removed by loosening nuts and bolts that hold the arbor firmly in position. The arbor can be slid off the over arm. The spacers are then

removed as well as the original cutter. The new cutter is placed in position, spacers slid back onto the arbor and the arbor bracket tightened back in position.

FUNCTION

Column The column houses the spindle, the bearings, the gear box, the clutches, the shafts, the pumps, and the shifting mechanisms for transmitting power from the electric motor to the spindle at a selected speed.

Knee The knee mounted in front of the column is for supporting the table and to provide an up or down motion along the Z axis.

Saddle The saddle consists of two slide ways, one on the top and one at the bottom located at 90º to each other, for providing motions in the X or Y axes by means of lead screws.

Table The table is mounted on top of the saddle and can be moved along the X axis. On top of the table are some T-slots for the mounting of workpiece or clamping fixtures.

Arbor The arbor is an extension of the spindle for mounting cutters. Usually, the thread end of an arbor is of left hand helix.

WORKING PRINCIPLE The work piece is holding on the worktable of the machine. The table movement controls the feed of work piece against the rotating cutter. The cutter is mounted on a spindle or arbor and revolves at high speed. Except for rotation the cutter has no other motion. As the workpiece advances, the cutter teeth remove the metal from the surface of workpiece and the desired shape is produced.

The Vertical Milling Machine Figure shows a vertical milling machine which is of similar construction to a horizontal milling machine except that the spindle is mounted in the vertical position.

Motor-The motor supplies the power to the spindle.

Tool head-The tool head houses the spindle. The tool head is located at the end of the Ram.The tool head also contains the motor. Column-The column of the milling machine, along with the base, are the major structuralcomponents. They hold, align, and support the rest of the machine.

Table-Holds and secures the workpiece for machining.

Saddle-The saddle it attached to the knee. The saddle provides the in and out, or Y axistravel of the table. Knee-The knee supports the saddle and the table. The knee can be moved up and down forworkpiece positioning.

Ram-The ram allows the Tool head to slide in and out. The ram gives the machine greatercapacity and flexibility. It is recommended that the tool head be kept as close to the column as possible during heavy milling work.

WORKING PRINCIPLE The workpiece is holding on the worktable of the machine. The table movement controls the feed of workpiece against the rotating cutter. The cutter is mounted on a spindle or arbor and revolves at high speed. Except for rotation the cutter has no other motion. As the workpiece advances, the cutter teeth remove the metal from the surface of workpiece and the desired shape is produced.

Milling Machine

Plain Milling

Plain milling is the milling of a flat surface with the axis of the cutter parallel to the machining surface. It can be carried out either on a horizontal machine or a vertical machine as shown in figure.

End Milling

End Milling is the milling of a flat surface with the axis of the cutter perpendicular to the machining surface as shown in figure. Gang Milling

Gang milling is a horizontal milling operation that utilizes three or more milling cutters grouped together for the milling of a complex surface in one pass. As illustrated in figure. Different type and size of cutters should be selected for achieving the desire profile on the workpiece.

Straddle Milling

In straddle milling, a group of spacers is mounted in between two side and face milling cutters on the spindle arbor as shown in figure for the milling of two surfaces parallel to each other at a given distance.

Milling Set Up

Correct use of holding device and a good set up are of crucial importance in achieving a safe,

accurate, and efficient operation of the machine. Large workpiece can be mounted directly onto

the machine table by means of tenons and screws while small work pieces are usually held by

machine vice as shown in figure 20. In either case, a dial indicator is used for alignment checking

Vice Alignment

In the setting up of the vice onto the machine table, the fix jaw of the vice must be set parallel to

the machine table using a Parallel Bar and a Dial Indicator as illustrated in figure 21. Adjustments

can only be made by using a hide face hammer to correct its position such that a near zero

indicator movement is achieved at all positions along the parallel bar

Any Four Operations Performed On Milling Machine

Plain milling Face milling Side and face milling Straddle milling

Apron:

Attached to the front of the carriage, it has the mechanism and controls for moving the

carriage and crossslide. Types Of Drilling Machine

Portable drilling machine Sensitive drilling machine Upright drilling machine Radial drilling machine Gang drilling machine Multi spindle drilling machin

RADIAL DRILLING MACHINE

1. Base:

The base of the machine is a large cast iron material on which is mounted a cylindrical vertical column. The base is provided with T-slots, which help the work piece to be clamped rigidly to the base of the machine.

2. Vertical column:

The column is a long, cylindrical shaped part fastened rigidly to the base. The column carries a radial arm that can be raised or lowered by means of an electric motor and can be clamped to any desired position. The radial arm can also be rotated (swiveled) in a complete circle around the column.

3. Drill head:

The drill head is mounted on the radial arm and carries a driving motor and a mechanism for revolving an feeding (power feed) the drill bit into the workpiece. The drill head can be moved horizontally on the guide ways provided in the radial arm, and can be clamped to any desired position.

With the combination of the movements of radial arm the drill head, it is possible to move the drill bit, and hence generate a hole at any desired position without moving the work piece.

WORKING PRINCIPLE

It the largest and most versatile used for drilling medium to large and heavy work pieces. Radial drilling machine belong to power feed type.

The column and radial drilling machine supports the radial arm, drill head and motor. Fig shows the line sketch of radial drilling machine.

The radial arm slides up and down on the column with the help of elevating screw provided on the side of the column, which is driven by a motor.

The drill head is mounted on the radial arm and moves on the guide ways provided the radial arm can also be swiveled around the column.

The drill head is equipped with a separate motor to drive the spindle, which carries the drill bit. A drill head may be moved on the arm manually or by power. Feed can be either manual or automatic with reversal mechanism.

Radial drilling machines are used for drilling medium or large diameter holes up to 50 mm in heavy work pieces.

List Of Operation Performed On A Drilling Machine

Drilling Reaming Boring Counter boring Counter sinking Spot facing Tapping

List The Important Drilling Tools

Twist drill Reamer Boring tool Countersinking tool

The Twist Drill Nomenclature

Drill nomenclature comprises the various parts and important geometric parameters of cutting point. They are shown in Figure defined below.

Shank

The shank is the part of drill which is held in machine spindle and driven by it.

Tang

Flattened end of shank, intended to fit into a slot in the drill holder.

Neck

There is large number of special drills manufactured against order to meet specific requirements. Such drills can be classed as special drills.

Body

The fluted portion of a drill.

Flutes

Flutes are helical grooves formed in the body of drill.

Web

The central portion of the body which separates the flutes and runs through entire length of drill.

Cutting Lip or Edge

The edges formed by intersection of flank and face, and correspond to the cutting edge of a single point tool.

Land

It is the cylindrical ground surface on the leading edges of drill flutes.

Body Clearance

The diameter over the surface of the body which is situated behind the land.

Margin

Narrow surface along the groove which keeps the drill aligned.

Heel

The edges formed by the intersection of flute surface and body clearance.

UNIT-III

MECHANICS

Stress. when a body is subjected to a system of external forces, it undergoes a deformation. At the same time, by virtue of its strength it offers resistance against this deformation. This internal resistance offered by the body to counteract the applied load is called the

stress. Stress=Force/Area. Unit for stress is N/m2

Strain. Strain is defined as change in dimension produced by the external force on the body.

Strain =

Draw stress- strain curve . Stress StrainDiagram

Where A- Proportional limit

A – Elastic limit

B – Yield point

AB – Permanent set region

BC – Plastic region / range

C - Ultimate point / strength stress

D – Breaking point / stress

CD – Non – uniform flow

Types Of Stress

Tensile stress

Compressive stress Shear stress

Types Of Strain.

Tensile strain

Compressive strain

Shear strain

Volumetric strain

Lateral strain

Tangential stress. When the force is applied along the surface of the body then the stress applied is called as Tangential stress.

THE TYPES OF STRESS WITH DIAGRAM (i) Tensile stress: when external force produce elongation of the body in its direction

it is called as tensile force. The stress now developed in the cross section of the body is called tensile stress (ft).

Tensile stress (ft) =

(ii) Compressive stress: when external force causes shortening of the body in the direction of force it is called as compressive force. The stress developed in the body due to the compressive force is called as compressive stress (fc).

Compressive stress (fc) =

(iii) Shearstress: The tangential force acting along a section of a body is called shear force. Consider a rectangular block ABCD of height “h” and length “ ”. Let the bottom “CD” of the block be fixed. Force “P” is applied tangentially along the top. For the equilibrium of the block, the fixed surface will offer tangential reaction which is equal and opposite to the tangential force “P”.The intensity of shear resistance along the section is called shear stress.

Shear stress (P) =

Types Of Strain With Diagram.

i. Tensile strain: Due to the application of load(pull) the length of the member

increases from “l” to(l+dl). The ratio of the increase in length to the original length is called tensile strain.

Tensile strain (et) =

ii. Shear strain: if the element ABCD is subjected to shearing stresses on faces AB and CD, it undergoes deformation. Let the horizontal displacement of the upper face of the block be “dl”. The ratio of transverse displacement to the distance from the lower face is called shear strain.

Shear strain =

= =

iii. Volumetric strain: The change in volume of an elastic body due to external force in unit original volume.

Let the original volume = V

Let the change in volume = dV

Volumetric strain = dV/V

iv. Compressive strain: Due to the application of load (push), the length decreases from l to (l-dl). The ratio of decrease in length to the original length is called

compressive strain (ec).

Compressive strain (ec) =

Stress and strain. Stress

Stress is defined as the restoring force per unit area which brings the body to its original state from the deformed state.

Strain

Strain is defined as the change in dimension produced by the external force on the body

Strain =

Stress Strain diagram

Stress strain curve of mild steel

When a ductile material is subjected to tension test, it passes through the following

stages before it fails. a) Limit of proportionality (A): This is the stage up to which the material behaves

Hooke’s law that is the strain is proportional to the stress. Therefore up to this limit the stress-strain curve is a straight line.

b) Elastic limit (B): This is the limit up to which the strain produced will disappear

completely on the removal of load. It can be noted from the figure that between limit of proportionality and elastic limit the strain is not proportional to the stress.

c) Yield point (C): At this stage the material is in semi plastic condition and the strain increases even without any increase in the stress. Even for a small increase in stress the increase in strain is very large. Beyond the yield point C, and the ultimate load point D, the cross sectional area decreases in the same proportion as the length increases.

d) Ultimate load point (D): This is the maximum stress the material takes during the test.

At this stage waist is formed in the material and there after the extension continuous without any increase in load.

Bulk Modulus

Bulk modulus is defined as the ratio of volume stress to volume strain

K= volume stress/volume strain = (F/A)/(v/V)

K = (PV)/v

P= pressure P = F/A

V = original volume

V = change in volume

Rigidity Modulus. It is defined as the ratio between the tangential stress to the shearing strain within the elastic limits.

Rigidity modulus n = = N/m2

Yield Strength.

The value of stress at the yield point is called yield strength of that material.

Ultimate Tensile Strength. When a wire is loaded, it gets deformed and a point at which the value of the developed stress is maximum is called as the ultimate tensile strength.

Poisson ratio σ Poisson`s Ratio is defined as the ratio of lateral strain per unit stress to

longitudinal strain per unit stress.

Poisson ratio σ

Relation Between three moduli of Elasticity Relation between the three moduli (Y, K, N)

α=

α= longitudinal strain / stress

α- 2β =

β = lateral strain / stress

α+ β =

Y =

σ =

- 1

Poisson ratio= σ

σ = Modulus Of Elasticity.

Stress/Strain = Constant= Modulus of elasticity There are three modulus of elasticity

Young’ s Modulus(Y)

Bulk Modulus ( k)

Rigidity Modulus ( N )

= Lateral strain/stress(β)

Longitudinal strain/stress (α)

Centre of gravity. The point at which the entire mass of the body is assumed to be concentrated. It is an

imaginary point. In case of plane figures of uniform material having the same thickness, the

weight of the body is proportional to the area. Hence the centre of gravity can be considered

to be the point at which the entire area of the figure is assumed to be concentrated. Elasticity When an external force acts on a body, it undergoes some deformation. The property by which a body returns to its original shape after the removal of external load is called Elasticity

Determine the young’s modulus of the material of a mild steel rod of 12mm diameter

and 200mm length elongates 0.085mm under on axial pull of 10KN.

Load P = 10KN

= 10,000.N

Cross – sectional areaof the rod A =

A steel rod of 20mm diameter and 3m long is subjected to an axial pull of 45KN.xTake ‘E’

= 210 GN/m.

Find the centre of gravity of the lamina shown fig.

The given lamina may be split up into two rectangles ABCD and CEFG as shown in fig

Find the centre of gravity of the lamina shown in fig.

UNIT – IV

BUILDING MATERIALS AND CONSTRUCTION

THE CLASSIFICATION AND QUALITIES OF A BRICK

Classification: Bricks can broadly be divided into two categories.

(i) Unburnt or sundried bricks (ii) Burnt bricks (i) Un burnt or Sun dried bricks- UN burn or sun dried with the help of heat received from sun after the process of moulding. These bricks can only be used in the constructions of temporary and cheap structures. Such bricks should not be used at places exposed to heavy rains. (ii) Burnt Bricks: The bricks used in construction works are burnt bricks and they are classified into the following four categories.

a. First Class bricks: These bricks are table moulded and of standard shape. The surface and edges of the bricks are sharp, square, smooth and straight. The comply all the qualities of good bricks and used for superior work of permanent nature b. Second class bricks: These bricks are ground moulded and they are burnt in kilns. The surface of bricks is some what rough and shape is also slightly irregular. These bricks are commonly used at places where brick work is to be provided with a coat of plaster. c. Third class bricks: These bricks are ground moulded and they burnt in clamps. These bricks are not hard and they have rough surfaces with irregular and distorted edges. These bricks give dull sound when struck together. They are used for unimportant and temporary structures and at places where rainfall is not heavy. d. Fourth class bricks: These are over burnt bricks with irregular shape and dark colour. These bricks are used as aggregate for concrete in foundation, floors, roads, etc because of the fact that the over burnt bricks have compacted structure and hence, they are some times found stronger than even first class bricks.

Qualities of Good Brick: (i) Bricks should be table moulded, well burnt in kilns, copper coloured, free from cracks and with sharp and square edges. (ii) Bricks should be uniform shape and should be of standard size. (iii) Bricks should give clear ringing sound when struck each other. (iv) Bricks when broken should show a bright homogeneous and compact structure free from voids. (v) Bricks should not absorb water more than 20 percent by weight for first class bricks and 22 percent by weight for second class bricks, when soaked in coldwater for a period of 24 hours. (vi) Bricks should be sufficiently hard no impression, should be left on brick surface, when it is scratched with finger nail. (vii) Bricks should be low thermal conductivity and they should be sound proof.

(viii) Bricks should not break when dropped flat on hard ground from a height of about one meter. (ix) Bricks, when soaked in water for 24hours, should not show deposits of white salts when allowed to dry in shade.

(x) No brick should have crushing strength below 55kg/cm2

THE TYPES OF BRICKS

Special Types: Bricks are made in a wide range of shapes and to suit the requirements of the location where they are to be used. Special form of bricks may be needed due to structural consideration or for ornamental decoration as defined by the architect. Specially moulded bricks avoid the cumbersome process of cutting and rounding the rectangular bricks to the desired shape. Some of the special types of bricks commonly used are given below.

4. Squint Bricks: These bricks are made in a variety of shapes and are used to the construction of a cute and obtuse squint quoins.

b. Bull Nosed Bricks: These bricks are used to form rounded quoins.

c. Perforated Bricks: These bricks may be standard size bricks produced with perforations running through their thickness. Perforated bricks are easy to burn and their light weight makes it possible to cut down the weight of the structure and effect in foundations. The aperture of the perforations is such that it gives maximum amount of ventilation. But does not permit the entry of rats or mice. These bricks are used for constructing load bearing walls of low buildings, panel walls for multistoried buildings and for providing partition walls.

d. Hallow Bricks: These bricks are made of clay and are provided with one or more cavities. Hallow bricks are light in weight and are used to increase insulation against heat and dampness. They are used for the construction of load bearing walls, partition walls or panel walls to multistoried buildings.

e. Circular Bricks: These bricks have internal and external faces curved to meet the requirement of the particular curve and radius of the wall. These bricks are used for wells, towers etc.

f. Plinth cornice and String Course Brick: These bricks are moulded in several patterns with the object of adding architectural beauty to the structure and at the same time to helping to throw the rack water off the face of the walls.

g. Coping Bricks: These bricks are manufactured in a variety of shapes to set the thickness of the wall and are throated on the underside to throw off rain water.

h. Paving Bricks: These bricks are specially made for paving the surface of streets and highways. These bricks are usually made from shale, fire clay on a mixture of the two. They are unaffected by weather and ordinary traffic wear. They are loaded on the bed of sand which in term rests on foundation of stone or concrete. The bricks are laid by grouting with cement mortar or asphalt. They are machine moulded and are burnt in a continuous kiln to ensure high degree of verification.

TESTS FOR BRICKS

A brick is generally subjected to following tests to find out its suitability of the construction work.

a) Absorption b) Crushing strength or compression strength c) Hardness d) Presence soluble salts e) Shape and size f) Soundness g) Structure

a) Absorption: A good should not absorb not more than 20 percent of weight of dry brick b) Compressive strength: crushing or compressive strength of brick is found out by placing it

in compression testing machine. It is pressed till it breaks. Minimum crushing strength of brick is 35kg/cm2 and for superior bricks, it may vary from 70 to 140 kg/cm2.

c) Hardness: No impression is left on the surface the brick is treated to be sufficiently hard. d) Presence of soluble salts: The bricks should not show any grey or white deposits after

immerted in water for 24 hours. e) Shape and size: It should be standard size and shape with sharp edges f) Soundness: The brick should give clear ringing sound struck each other

g) Structure: The structure should be homogeneous, compact and free from any defects

THE FUNCTION OF ALL INGREDIENTS OF CEMENT

Functions of Ingredients:

a) Lime: Lime is the important ingredient of cement and its proportion is to be maintained carefully. Lime in excess makes the cement unsound and causes the cement to expand and disintegrate. On the other hand, if lime is in deficiency the strength of the cement is decreased and it causes cement to set quickly .

b) Silica: This also an important ingredient of cement and it gives or imparts quick setting property to imparts strength to cement.

c) Alumina: This ingredient imparts quick setting properly to cement. Express alumina weakens the cement.

d) Calcium Sulphate: This ingredient is in the form of gypsum and its function is to increase the initial setting time of cement.

e) Magnesia: The small amount of this ingredient imparts hardness and colour to cement.

f) Sulphur: A very small amount of sulphur is useful in making sound cement. If it is in excess, it causes the cement to become unsound.

g) Alkalies: Most of the alkalies present in raw material are carried away by the flue gases during heating and only small quantity will be left. If they are in excess in cement, efflorescence is caused.

Types Of Cement And Its Uses

TYPES OF CEMENT

In addition to ordinary cement, the following are the other varieties of cement.

a. Acid Resistance Cement: This is consists of acid resistance aggregates such as quartz, quartzite’s, etc, additive such as sodium fluro silicate (Na2SiO6) and aqueous solution of sodium silicate. This is used for acidresistant and heat resistant coating of installations of chemical Industry. By adding 0.5 percent of unseed oil or 2 percent of ceresil, its resistance to water is increased and known as acid water resistant cement. b. Blast Furnace Cement: For this cement slag as obtained from blast furnace in the manufacture of pig iron and it contains basic elements of cement, namely alumina, lime and silica. The properties of this cement are more or less the same as those of ordinary cement and prove to be economical as the slag, which is waste product, is used in its manufacture

c. Coloured Cement: Cement of desired colour may be obtained by intimately mixing mineral pigments with ordinary cement. The amount of colouring may vary from 5 to 10 percent and strength of cement if it is exceeds 10 percent. Chromium oxide gives brown, red or yellow for different proportions. Coloured cements are used for finishing of floors, external surfaces, artificial marble, windows.

d. Expanding Cement : This type of cement is produced by adding an expanding medium like sulpho – aluminate and a stabilizing agent to ordinary cement. Hence this cement expands where as other cement shrinks. Expanding cement is used for the construction of water retaining structures and also for repairing the damaged concrete surfaces.

e. High alumina Cement: This cement is produced by grinding clinkers formed by calcining bauxite and lime. The total content should not be less than 32 percent and the ratio by weight of alumina to lime should be between 0.85 and 1.30.

Advantages 1. Initial setting time is about 31/2 hours therefore, allows more time for mixing and placing operations. 2. It can stand high temperatures.

3. It evolves great heat during setting therefore not affected by frost. 4. It resists the action of acids in a better way.

5. It lets quickly and attains higher ultimate strength.

Disadvantages: 1. It is costly 2. It cannot be used in mass construction as it evolves great heat and as it sets soon. 3. Extreme care is to taken to see that it does not come in contact with even traces of lime or ordinary cement.

f. Hydrophobic Cement: This type of cement contains admixtures, which decreases the wetting ability of cement grains. The usual hydrophobic admixtures are acidol napthene soap, oxidized petrolatum etc when hydrophobic cement is used, the fire pores in concrete are uniformly distributed and thus the frost resistance and the water resistance of such concrete are considerably increased.

g. Low Heat Cement: Considerable heat is produced during the setting action of cement. In order to reduce the amount of heat, this type of cement is used. It contains lower percentage of tri calcium aluminates C3A and higher percentage of dicalcium silicate C2s. This type of cement is used for mass concrete works because it processes less compressor strength.

h. Quick Setting Cement: This cement is prepared by adding a small percentage aluminum sulphate which reduce the percentage of gypsum or retarded for setting action and accelerating the setting action of cement. As this cement hardness less than 30 minutes, mixing and placing operations should be completed. This cement is used to lay concrete under static water or running water.

i. Rapid Hardening cement: This cement has same initial and final setting times as that of ordinary cement. But it attains high strength in early days due to

1. Burning at high temperature.

2. Increased lime content in cement composition. 3. Very fine grinding.

Advantages: 1.Construction work may be carried out speedily. 2.Formwork of concrete can be removed earlier. 3. It is light in weight.

4. It is not damaged easily. 5. This cement requires short period of curing.

6. Use of this cement also higher permissible stresses in the design. 7. Structural member constructed with this cement may be loaded earlier.

j. Sulphate Resisting Cement: In this cement percentage of tricalcium aluminates is kept below 5 to 6 percent and it results in the increase in resisting power against sulphate. This cement is used for structure which are likely to be damaged by sever alkaline condition such as canal linings, culverts, siphons etc.

k. White Cement: This is a variety of ordinary cement and it is prepared form such raw materials which are practically free from colouring oxides of Iron, manganese or chromium. For burning of this cement, oil fuel is used instead of coal. It is used for floor finish; plaster work, ornamental works etc.

USES OF CEMENT

1. Cement mortar for masonry work, plaster, pointing etc 2. Concreter for laying floors, roofs and constructing lintels, beams, weather sheds, stairs, pillars etc. 3. Construction of important engineering structure such as bridges, culverts, dams, tunnels storage reservoirs, light houses, deckles etc. 4. Construction of water tanks, wells, tennis courts, septic tanks, lampposts, roads, telephone cabins etc. 5. Making joints for drains, pipes etc.

6. Manufacture of pre cast pipes, piles, garden seats, artificially designed urns, flowerpots, etc dustbins, fencing posts etc. 7. Preparation of foundations, watertight floors, footpaths etc.

THE STEELS, CLASSIFICATION AND ITS USES IN CONSTRUCTION.

Steel contains carbon upto a maximum of 1.5 percent. Based on the carbon content, steel are classified into, (i) Low carbon steel (Mild steel) with carbon content 0.25 percent.

(ii) Medium carbon or medium hard steel with carbon content between 0.25 – 0.70 percent (iii) High carbon steel or hard steel having carbon content 0.70 – 1.5 percent.

Uses of Low carbon steel (Mild steel): Low carbon or mild steel is used in structural works such as trusses, angles and plates. It is also used in RCC works as plain or twisted rods. Uses of Medium hard steel: It is used in the manufacture of rails, chisels, hammers, boiler plates etc. Uses of hard steel: It is used in earth moving or mining equipments. Used for manufacturing cutting steel.

Torsteel rods : (i) Torsteel rods are twisted or torsioned deformed rods. (ii) Ordinary steel rods are round plain bars made of mild steel. (iii) Both plain bars and tor steel rods are used in RCC roof slabs, beams, columns

THE PROPERTIES AND USES OF PLASTICS

Plastic is one the recent engineering materials, which has appeared in the market all over the world. Plastic is an organic substance and it consists of natural or synthetic binder or resins with or without moulding compounds. Plastics are the compounds of carbon with other elements such as hydrogen, nitrogen and oxygen.

Properties:

1. Appearance: Some Plastics are completely transparent in appearance 2. Chemical resistance: Plastics offer great resistance to moisture, chemicals and solvents. 3. Dimensional Stability: This property of plastic favours quite satisfactorily with that of other common engineering materials. 4. Ductility: Plastic lacks ductility. Hence its member may fail without warning

5. Electrical Insulation: Plastic posses excellent electric insulating property 6. Durability: Please are quite durable. 7. Finishing: Any surface treatment may be given to plastic. It is also easy to have technical control during its manufacture. 8. Fire Resistance: Plastic are organic in nature and hence, all plastics are combustible. 9. Fixing: Plastics can be easily fixed in position they can be bolted, clamped, drilled, glued, screw threaded or simply push filled in position.

10. Humidity: The properties of plastic are governed to some extent by humidity. 11. Maintenance: It is easy to maintain plastic surfaces.

12. Melting Point: Most of the plastics have low melting point is about 500C. 13. Optical Property: Several types of plastics are transparent and translucent. 14. Sound Absorption: Acoustical boards are prepared by impregnating fiberglass with phenolic resins. 15. Strength: Plastic are reasonably strong. The strength of plastics may be increased by reinforcing with various fibrous materials. 16. Thermal property: Thermal conductivity of plastics is low compared to with wood.

17. Weather Resistance: Only certain varieties of plastics can be exposed to weather. 18. Weight: Low Specific gravity. The length weight of the plastic reduces the transport costs and facilitates fixing.

Uses of Plastics:

1. Bath and Sink units 2. Cistern ball floats 3. Corrugated and plain sheets 4. Decorative laminate and mouldings 5. Electrical conducts 6. Electrical insulations

7. Films of water proofing, damp proofing 8. Floor tiles 9. Foams for thermal insulation 10. Jiontless flooring

11. Lighting fixtures

12. Overhead water tanks 13. Paints and varnishes 14. Pipes to carry cold water

15. Roof lights 16. Wall tiles

17. Safety glass 18. Water resistant adhesives etc.

THE PROPERTIES AND USES OF MORTAR

The term mortar is used to indicate a paste prepared by adding required quantity of water to a mixture of binding material like cement or Lime and fine aggregates like sand. The two components of mortar namely the binding material and fine aggregates are some times referred to as matrix the durability, quality and strength of mortar will mainly depends on quantity and quality of the matrix. The combined effect of the two components of mortar is that the mass is able to bind the bricks or stones firmly.

Properties : The important properties of a good mortar mix are mobility, placeability and water retention. The

mobility is used toindicate the consistency of mortar mix, which may range from stiff to fluid The mobility of mortar depends upon composition of mortar and mortar mixes to be used for masonry work, finishing works, etc are made sufficiently mobile. The placeability or the ease with which the mortar mix can be placed with minimum cost in a thin and uniform layer over the surface depends on the mobility of mortar. The placeablity of mortar mix should be such that a strong bond is developed with the surface of the bed. A good mortar mix should posses the ability if retaining adequate humidity during the transportation and laying over the porous bed. If water retention power of mortar mix is low it separates into layers during transportation and when it comes contact with the porous bed like brick, wood, etc, it gives away its water to that surface. Thus the mortar becomes poor in a amount of water and remaining water proves to be insufficient for its hardening. Hence required strength of mortar will not be achieved with such a mortar mix will.

Properties of good mortar 1. It should be capable of developing good adhesion with the building units such as bricks, stones etc. 2. It should be capable of developing the designed stresses. 3. It should be capable of resisting penetration of rainwater. 4. It should be cheap. 5. It should be durable. 6. It should be easily workable. 7. It should not affect the durability of materials with which it comes into contact.

Uses: 1. To bind the building units such as bricks, stones etc.

2. To carry out painting and plaster works on exposed surfaces of masonry 3. To form an even bedding layer for building units

4. To form joints of pipes

5. To improve the appearance of structure.

The Types Of Mortar Types of mortars used for

plastering a) Cement Mortar

b)Lime Mortar

c) Cement-lime mortar d) Water – proof mortar.

a) Cement Mortar: (i) It is a mixture of ordinary portland cement and coarse sand in predetermined proportions. (ii) The proportions of cement and sand depends on the nature of plastering work. (iii) The usual mix for cement mortar for plastering varies from 1:3 for the surfaces in cntact with water to 1:4 to 1:6 for other surfaces.

b) Lime mortar: (i) Equal volumes of lime and fine sand are thoroughly mixed. (ii) Either fat lime or poor lime may be used in lime mortar. (iii) The mixture is ground in a mortar mill by adding required quantity of water to form a paste of required consistency and workability

c) Cement Lime mortar: (i) Cement lime mortar is prepared by first mixing cement and sand in a dry state in the requirement proportions. (ii) Fat lime is mixed with water and is added to the cement sand mix. (iii) The materials are thoroughly mixed till a mortar of the desired consistency and workability is obtained.

d) Water proof mortar: (i) Water proof mortar for plastering is prepared by mixing 1 part of cement with 2 parts of sand and pulverized alum at the rate of 12 kg/m3 of sand. (ii) Soap water is added to the dry mixture to make it water proof and to obtain required consistency and workability.

EXPLAIN BRICK MASONRY AND EXPLAIN ITS TYPES

Brick Masonry (Bonds in Brick work): a) Stretcher Bond: (i) All the bricks are arranged in stretcher courses. (ii) The stretcher bond is useful for one brick partition as there areno headers. (iii) As the internal bond is not proper this is not used for wallsof thickness greater than one brick.

b) Header Bond (i) All bricks are arranged in header courses. It is used forcurved surfaces since the length Will be less.

c) English Bond: (i) It is most commonly used type of bond. (ii) It is the strongest type of bond. (iii) It is used for all wall thicknesses. (iv) English bond consists of headersand Stretchers in alternative courses of elevation. (v) A queen closer is placed next to the quoin header in eachheader course to the full thickness of wall. Each alternative header lies centrally over a stretcher of the stretcher course.

d) Flemish Bond: Headers are distributed evenly as shown. The peculiarities of a Flemish bond are as follows.

1. In every course headers and stretchers are placed alternatively. 2. The queen closer is put next to the queen header in alternate course to develop the lap

3. Every header is centrally supported over a stretcher below it. 4. The Flemish bond may be either a double Flemish or Single Flemish bond. e) Racking Bond: It is used for thick It is subdivided into

1. Diagonal bond 2. Herringbone bond. 1. Diagonal bond: Bricks are laid diagonally. Internal placing of bricks is made in one Direction only at certain angle of inclination. 2. Herringbone : The bricks are laid at an angle of 450 from the centre in both directions.

stone masonry and its types? It is a natural choice for masonry. Its durability has been demonstrated and massive structures.

Coal tar, paraffin, linseed oil or solution of alum and soap are the preservatives used to prevent the stone from the effects of rain water, wind etc., Stone masonry is the construction carried out using stones with mortar.

Because of high cost of transportation, painful and costly work of dressing and need for experienced labour, stone masonry is presently not popular. Further stone masonry walls occupy more space compared brick work

CLASSIFICATION OF STONE MASONRY

a) Rubble Masonry: In this type stones of irregular shapes and sizes are used

It is ether broken to specified size with a hammer or used as it is.it is classified as follows:

(i) Random rubble masonry: It is the cheapest form of stone masonry It is further classified into coursed and uncoursed

In course stone masonry the stone in a course are of equal heights In

uncoursed stone masonry the stones are irregular in shape Larger

stones are laid and the gaps are filled up with small stones

(ii) square rubble masonry:

In this type the stones are squared or straight cut finished It is also classified as coursed and uncoursed In coursed type the depth is varied in courses

In uncoursed type stones of different sizes with straight edges are arranged.

(iii) Polygonal rubble masonry: In this the stones are hammer dressed in an irregular polygonal shape

The face joints are seen in an irregular in all direction.

(iv) Flint rubble masonry: Flints or cobbles are used in this type They are irregularly shaped nodules of silica The stones are hard, hence break easily.

(v) Dry rubble masonry: Mortar is not used at the joints. Cheapest and require more skill in construction.

Used for non-load bearing walls such as compound walls. Ashlar Masonry:

a) In Ashlar masonry, no irregular stones are used. b) The entire construction is done using square or rectangular dressed stones. c) The sides and faces of the stones are dressed finely with chisel.

TYPES OF ASHLAR MASONRY

a) Ashlar fine masonry

b) Ashlar rough tooled masonry c) Ashlar rock or quarry faced masonry d) Ashlar chamfered masonry e) Ashlar facing masonry

Types Of Concrete

The concrete are mainly classified into four types (i) Plain cement concrete (ii) Reinforced cement concrete

(iii) Pre-stressed concrete (iv) Fibre reinforced concrete

Plain cement concrete:

It is a mixture of cement, sand pebbles or crushed rock and water. It has high compressive strength. It is weak in tensile strength. It is free from corrosion.

It is used for floorings, gravity dam, simple strip foundation and other mass concreting works.

Reinforced cement concrete:

Cement concrete prepared with steel reinforcement is called reinforced cement concrete It can be used for the structural members subjected to both compressive and tensile stress.

Steel is strong in tension and introduced in the places where tensile stresses are developed. It is used for roof slabs, columns, dams,pile foundation, railways.

Pre-stressed concrete:

In this type of concrete, high tensile steel wires are used as reinforcement instead of mild steel bars. There are two types of pre stressing namely pre tensioning and post tensioning.

In pre tensioning method the wires are initially stressed and the concrete is built around the wires. The wires are released after the concrete attains its strength. In post tensioning, the wires are placed inside the concrete and then stressed.

Fibre reinforced concrete: It consists of cement, fibre, sand and water.

Nylon, glass, asbestos are the fibers used for reinforcement. It is more durable. Production rate is less and less maintenance cost

UNIT-V

ROADS, RAILWAYS, BRIDGES AND DAMS

THE CLASSIFICATION OF ROAD

1. National highway: Roads connecting state capitals, industrial centers and major ports

2. State highway: It connects district headquarters and important cities within the state

3. Major district road: It connects important towns within the district

4. Other district road: It connects villages with towns

5. Village road: It connects village to village or to nearby railway station

LIST THE COMPONENTS PRESENT IN ROAD a. Wearing surface b. Base course c. Sub base course d. Soil sub grade

TELL WHAT IS A ROAD AND EXPLAIN THE COMPONENTS IN ROAD

Road is a specially designed path in which transport vehicles pass.

Components in road:

iv. Surface course/wearing surface: It gives smooth riding surface and it provides a water tight layer which prevents the entering of water to the sub grade.

v. Base course: Layer placed between the wearing surface and the sub grade. it gives firm support to the road surface and it transmits wheel load to the underlying layer.

vi. Sub base course: If the bearing capacity of soil is poor, an additional layer is laid between the base course and the wearing surface. It improves the load supporting capacity of soil by distributing the load.

vii. Soil sub grade: Top of the ground on which foundation of road rest. It should not be overstressed. 0.5 m of soil is laid on this layer at optimum moisture content.

The Structure Of A Permanent Way The combination of railway track that is rails, fixtures, sleepers and ballast is called a permanent way. It consists of a two parallel steel rails fixed to a sleeper resting on ballast. When train runs over the tract, the rails transmit the entire wheel load to the sleepers and sleeper transfer the load from rails to the ballast. The ballast distributes the load to the formation.

COMPONENT PART OF PERMANENT WAY: Rails Sleepers Fixtures and fastening Ballast Formation/ sub grade

v. Rails: Rolled steel sections laid in two parallel lines over the sleeper to form a railway track.

Main functions of rails are

Provides continuous even and smooth riding surface for the movement of trains It transmits the moving loads to the sleeper

Types of rails:

Flat footed rails Bull headed rails Double headed rails

e) Sleepers:

Members laid transversely under the rails for supporting and fixing them at the gauge distance.

Wooden sleeper

Steel

Castiron

Reinforced cement concrete Pre stressed concrete

ii. Fixtures and fastenings:

Fixtures: It is used to connect the rails with each other and also to fix them with the sleeper at the desired gauge distance.

Rail fastening: Rails are manufactured in certain fixed length. Rails are joined by means of two fish plates one on either side of the joint with the help of fish belts.

b Ballast:

Layer of broken stones or other suitable material which is spread on the top of the formation and around sleepers. The main functions of ballast are

Transmit and distribute the load from sleeper to formation It provides stability to the track

It helps to drain water immediately to keep the sleeper in dry condition. The

best material for ballast is non porous, hard and angular stones (25mm-50mm).

d. Formation of sub grade:

The top of the ground on which the whole railway track rest. It should be hard and top layer of 0.5 m of sub grade soil should be well compacted at optimum moisture content.

BRIDGE A bridge is a structure providing passage over an obstacle such as an vale, road, railway, canal, river without closing the way beneath. The required passage may be road, railway, canal, pipeline, cycle track or pedestrians.

THE COMPONENT PARTS OF PERMANENT WAY Rails Sleepers Fixtures Fastening Ballast Formation/sub grade

WHAT IS DAM A dam is an impervious barrier or an obstruction constructed across a natural stream or a river to hold up water on one side of it up to a certain level.

the different types of dam a. Based on structural behavior: Gravity dam, Arch dam, Buttress Dam. b. Based on hydraulic design: Non over flow dam, over flow dam. c. Based on materials used: Earth dam, Rock fill dam, RCC dam, Composite dam, steel dam.

Purposes of Dam. a. To store the surplus water.

b. To control the stored water for irrigation. c. To create hydro-electric power plant.

d. To divert the water for domestic uses.

TELL WHAT IS A BRIDGE AND EXPLAIN BRIEFLY THE COMPONENT OF

A BRIDGE Definition: A bridge is a structure providing passage over an obstacle such as an vale, road, railway, canal, river without closing the way beneath. The required passage may be road, railway, canal, pipeline, cycle track or pedestrians. Components of a bridge: Pier: These are provided between the two extreme supports of the bridge (abutments) and in the bed of the river to reduce the span and share the total load acting on the bridge. Abutments: The end supports of a bridge superstructure are called abutments. It may be of brick masonry, stone masonry, or RCC. It serves both as a pier and as a retaining wall. The purposes of abutments are, iii. To transmit the load from the bridge superstructure to foundation. iv. To give the final formation level to the bridge superstructure v. To retain the earth work of embankment of the approaches.

Deck with road surface: Deck is top horizontal portion of the bridge. It may be made of R.C.C or prestressed concrete or steel girders and joist.

Foundations: Foundation forms the lowest part of a bridge. The type of foundation depends upon the nature of the subsoil, velocity of water. Well foundation is the most commonly adopted bridge foundation.

Bank connections: Bank connection like wing walls and return walls provide a connection between the bridge abutments and road approach.

Approaches: These are the length of communication route at both ends of the bridge.

Hand rails: Hand rails are provided on both sides of a bridge to prevent any vehicle from falling into the stream.

Guard stones: It indicates the presence of a bridge to the road users approaching the bridge at a distance. It is available on both sides of the bridge. They guide the vehicle for a safe entry onto the bridge.

Tell what is a dam and explain the types of dam A dam is an impervious barrier or an obstruction constructed across a natural stream or a river to hold up water on one side of it up to a certain level.

Classification of dams: Dams are broadly classified into, 1. Rigid Dams 2. Non rigid dams.

Rigid dams: These dams are constructed using rigid construction materials. The construction materials used are, stone or brick or reinforced cement concrete.

Rigid dams are further classified into, 1. Solid gravity dam 2. Arch Dam 3. Buttress dam 4. Timber and steel dam

Solid Gravity Dam:

A gravity dam is defined as a structure which is designed in such a way that its

own weight resists external forces. It is more durable and has maximum rigidity. It requires less maintenance compared to other types. This type can be constructed of masonry or concrete. Nowadays, concrete dams are prevalent.

Arch Dam:

Arch dams are curved in plan. This structure less Massive when compared to gravity dam

The forced exerted by the stored water on upstream side will be transferred by the abutments of the arch dam.

This dam is suitable for narrow valleys but major requirements are sound abutments. An arch dam is economical only when the length of dam is less than its height.

Buttress dam: A buttress dam has relatively thin sections when compared to a gravity dam.

It consists of a sloping section buttresses and a base slab. The sloping membrane

(Face slab) first takes the water load and transfer to the buttresses which are specific intervals.

The buttresses in turn transfer the load to the base slab which forms the

foundation part of the dam.

Timber and Steel Dam: Timber and steel dams are not generally used for bigger dam sections.

A timber dam is generally adopted for temporary requirements to enclose certain

work sites or to divert the flow.

After the main structure is built the timber dam will be dismantled. Timber dams are generally made water tight.

Steel dams are not common in use. But it is possible to construct the dam with

steel up to a height of 15-18 m

Non Rigid Dams: Non rigid dams have a trapezoidal basic profile. Types of Non Rigid dams

= Earth Dams = Rock fill dams.

Earth Dam:

Earth dams are made of soil with minimum processing using primitive equipment These are built in areas where the foundation is not strong enough to bear the weight of a gravity dam.

As the construction material of the dam is ordinary soil which is cheaply available

the cost of construction of this dam is less than rigid dam.

Rock Fill Dam: Rock fill dams are made of loose rocks and boulders piled in the river bed.

A slab of reinforced concrete is often laid on the upstream face to make it water tight. There are more stable than earthen dams and les stable than gravity dams.

The dam section generally consists of dry ruble stone masonry on the upstream side and loose rock fill on the downstream side.