Presentation byK. Prudhvi RahulBTG Batch - 8

MECHANICAL ENGINEERING

Topics To Be Covered• Basics of mechanical engineering• Units and measurements• Measuring instruments• Mechanical equipment• Manufacturing process• Codes and standards• Measuring equipment & techniques• Hvac System• Heat transfer• Material Handling• Mechanical properties of materials• IC engines• Hydraulic machines• Strength of materials

What is mechanical engineering?•  Mechanical engineering is

the discipline that applies the principles of engineering, physics, and materials science for the design, analysis, manufacturing, and maintenance of mechanical systems. It is the branch of engineering that involves the design, production, and operation of machinery

Mechanical Engineer?• Mechanical engineers

create and develop mechanical systems for all of humankind. Concerned with the principles of

• Force • Energy • Motion• Mechanical engineers use

their knowledge of design, manufacture, and operational processes to advance the world around us — enhancing safety, economic vitality and enjoyment throughout the world.

What Is a Force?

• A force is a push or pull upon an object resulting from the object's interaction with another object.

• Mainly there are two types of forces:

• Contact Forces• Non Contact Forces• Force is Measured in

Newtons

FORCEForce

ContactFriction

Air Resistance

Normal Force

Applied Force

Tension Force

Spring Force

Non ContactGravitational Force

Magnetic Force

Electrical Force

Frictional Forces & Applied Forces

• Whenever an object moves against another object, it feels frictional forces.

• These forces act in the opposite direction to the movement.

• Friction makes it harder for things to move.

• The pushing or pulling force we were applying on an object is called as Applied Forces.

How Many Types Of Friction?

1

2

3

4

Helpful Frictional Forces &Unhelpful Frictional Forces• Friction can be useful:

• Friction between tires and the road stop cars from skidding.

• Friction between the brakes and wheel help bikes and cars slow down.

• Friction can also be unhelpful:• If you don't lubricate your bike regularly with oil, the

friction in the chain and axles increases. Your bike will be noisy and difficult to pedal.

• When there is a lot of friction between moving parts, energy is lost to the surroundings as heat.

Air Resistance• Air resistance is

caused by the frictional forces of the air against the vehicle.

• The faster the vehicle moves, the bigger the air resistance becomes.

Normal Force

• When a body exerts a force on another, the second provides a reaction which acts perpendicular to the surface of 2nd body.  

Tension Force

• The Tension force is the force that is transmitted through a string, rope, cable or wire when it is pulled tight by forces acting from opposite ends.

• The tension force is directed along the length of the wire and pulls equally on the objects on the opposite ends of the wire.

Spring Force• The spring force is the force exerted by a

compressed or stretched spring upon any object that is attached to it. An object that compresses or stretches a spring is always acted upon by a force that restores the object to its rest or equilibrium position.

Hooks Law

• Hooke's law states that the force F needed to extend or compress a spring by some distance X is proportional to that distance.

• F = KX where K is a constant of the spring: its stiffness, and X is the deformation of the spring.

• F= -KX When the direction of the restoring force is opposite to that of the displacement.

Non Contacting Forces• Gravitational Forces: Newton's law of

universal gravitation states that any two bodies in the universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

• F is the force between the masses;• G is the gravitational constant (6.674×10−11 N · 

(m/kg)2);• m1 is the first mass;• m2 is the second mass;• r is the distance between the centers of the

masses.

Lorenz Force

• Lorentz force: It is the combination of electric and magnetic force on a point charge due to electromagnetic fields. If a particle of charge q moves with velocity v in the presence of an electric field E and a magnetic field B, then it will experience a force

• F = q E + q v × B

What Is Energy?• The ability of a system to

perform work.• Energy is a property of

objects which can be transferred to other objects or converted into different forms.

• Law Of Conservation Of Energy: energy can be neither created nor be destroyed.

• Energy is measured in Joules.

Work• Work is said to be done on an object

when the force causes displacement of the object.

• Work is the product of the force applied on an object and the displacement of the object.

• W= Force x Displacement Displacement: is an

object's change in position considering its starting position and final position.

Work is measured in Joules

Types Of Energy

Mechanical Energy• Mechanical energy

is the sum of kinetic and potential energy in an object that is used to do work.

• In other words, it is energy in an object due to its motion or position, or both.

Kinetic Energy• kinetic energy

is the energy that the body possesses due to its motion.

• KE= 1/2MV2

• Where M is the mass and V is the speed (or the velocity) of the body.

Potential Energy• The energy stored in an

object by the virtue of its motion.

• The amount of gravitational potential energy an object has depends on its height above the ground and its mass.

• PE= mgh• Where m is Mass, g is

gravitational force, And h is height of the object.

Motion• Motion is a change in

position of an object with respect to time.

• Motion is typically described in terms of displacement, distance, velocity, acceleration, time and speed.

• It is measured in relationship to point of reference.

Motion Types(DOF)

Random Motion

• Random motion, also known as Brownian motion, is the movement of atoms and molecules.

• Gas is having random motion, because of the molecules move in different directions.

Randon Motion Of Gas Particles

Translational Motion• Translational motion is the movement

of an object from one point to another through space.

• Three types of translational motions:• Rectilinear

• Curvilinear

• Circular

Rotational And Oscillatory

• Rotational motion is an object moves around an axis passing through its body.

• Oscillatory motion is something that moves back and forth repeatedly.

DOF(Degrees of freedom)

• DOF is number of independent motions that are allowed to the body.

• In case of a mechanism number of possible independent relative motions between the pieces of the mechanism.

• Mostly used in robotics.

How many degrees of freedoms ?

• There are six degrees of a freedom for an object in space.

DOF of a ship

• The motion of a ship at sea has the six degrees of freedom of a rigid body, and is described as:

• Translation and rotation:• Moving up and down (elevating/heaving);• Moving left and right (strafing/swaying);• Moving forward and backward

(walking/surging);• Swivels left and right (yawing) ;• Tilts forward and backward (pitching);• Pivots side to side (rolling).

DOF of Plane

• A plane is also having six degrees of freedom.

Measurements And Units

Measurement• Measurement is the standard

which is used for comparison must be defined accurately, And it should be universally accepted.

• Measurement is the process of comparing unknown magnitude of certain parameter with the known predefined standard of that parameter.

How large is a millimeter?

•The width of a pin

How large is a centimeter?

The widthof the top

of your finger

How large is a meter?

About the width

of one & 1/2 doors

1 meter

How large is a milliliter?

About adrop ofliquid

• Units of Length• 10 millimeters = 1 centimeter• 10 centimeters = 1 decimeter• 10 decimeters = 1 meter• 1000 meters = 1 kilometer• Units of Weight• 10 milligrams = 1 centigram• 10 centigrams = 1 decigram• 10 decigrams = 1 gram• 1000 grams = 1 kilogram• 1000 kilograms = 1 metric ton

Measurements Of Length And Weight

Units• Units are standards for

measurement of physical quantities that need clear definitions to be useful.

• There are mainly two types of units

• Basic Units• Derived Units

Basic Units

• The International System of Units (SI) defines seven units of measure as a basic set from which all other SI units are derived. The SI base units and their physical quantities are:

Derived Units

Derived Mechanical Units

Features of Measured Quantities

• When we measure a number, there are physical constraints to the measurement.

• Instruments and scientists are not perfect, so the measurement is not perfect (i. e., it has error).

• The error in the measurement is related to the accuracy and the precision of the measurement

Accuracy and Precision

Accuracy – how close the measurement is to the “true” value (of course we have to know what the “true” value is)

Precision – is a measure of how closely individual measurements agree with one another.

Accuracy and Precision

Equations for Precision and Accuracy

1. Precision2. Accuracy Absolute Error % AE = (True value-Avg

Value) X 100 True Value

Measuring Instruments• A measuring

instrument is a device for measuring a physical quantity.

• In the physical sciences, quality assurance, and engineering, measurement is the activity of obtaining and comparing physical quantities of real-world objects and events.

Rulers• Rulers

– Simple tools to measure straight-line distances where tolerances are not a major factor

– Can be made of metal, plastic, or wood

– Typical rulers are 6 inches or 12 inches

– Tolerance: is the permissible limit or limits of variation.

– In mechanical engineering the space between a bolt and a nut or a hole Is the Tolerance

Tolerance

Calipers

• Calipers: Engineers and machinists frequently use calipers to secure accurate measurements of inside and outside diameters.

• A caliper can be as simple as a compass with inward or outward-facing points

Calipers

Feeler Gauges

• Feeler Gauges

– to measure the clearance between two parts

– Used for measuring “gaps” or the space between two objects

– Proper usage requires practice

Feeler Gauges

Feeler Gauges used for

• Valve lash • Measure spark plug gap• Head flatness• Thrust distance in Crankshaft• Ignition point gap (Old Vehicles)

Feeler gages are principally used in determining clearances between various parts of machinery. Probably the most common use is determining valve clearance. Various blades are inserted between the tappet and the push rod until a blade of the feeler gage is found that will just slide between the two surfaces without too much friction or sticking. The thickness of the blade then determines the clearance. Or, a particular feeler of proper thickness may be selected and the tappet adjusted until the feeler will just slide between the tappet and push rod with out catching.

Measuring Valve Clearance

Valve lash

Thrust distance in Crankshaft

Head flatness

Spark plug gap

Feeler Gauges with strip

Such a gage consists of thin blades of metal of various thicknesses. There is generally a blade or strip for each of the most commonly used thicknesses such as 0.002 inch, 0.010 inch, and .015 inch. The thickness of each blade is generally etched on the blade

Some other models of Feeler Gauges

Micrometers

• Micrometer is a caliper to obtain measurements accurate to 1/1000 of an inch.

• This instrument is particularly useful for measuring relatively short lengths and the diameter of bolts or cylinders.

• The common commercial micrometer consists of a frame, an anvil or fixed measuring point, a spindle, a sleeve or barrel, a thimble and a rachet.

Micrometer

Types of micrometers

• Outside micrometer typically used to measure wires, spheres, shafts and blocks.

• Inside micrometer used to measure the diameter of holes.

• Depth micrometer measures depths of slots and steps.

Outside Micrometer

Inside Micrometer

Depth Micrometers

Telescopic Gauges

Used with outside micrometers to measure inside diameters.

Various lengths and T-shaped. Extensions are spring-loaded. These wont contain individual

markings for measurement

Telescoping gages

Telescopic gauge

Telescoping Gauges

• Telescopic Gauges– Leg has a

rotatable handle to lock extensions in place.

– Once gauge is removed, measured with outside micrometer.

Small Hole Gauges

• To measure small holes• Gauge is straight with a screw

handle on one end and a split ball on other.

• Handle is turned to expand ball. • These wont contain individual

markings for measurement

– Removed and measured with a micrometer

Small Hole Gauges

Small Hole Gauge

Go/No Go gauge

• Go/No Go gauge refers to an inspection tool used to check a work piece against its allowed tolerances.

• Its name is derived from two tests: the check involves the work piece having to pass one test (Go) and fail the other (No Go).

• It does not return a size or actual measurement in the conventional sense, but instead returns a state, which is either acceptable (the part is within tolerance and may be used) or unacceptable (the part must be rejected).

Types Of Go Gauges

circular

Treaded nut

Treaded

Hexagonal

Some different types

Go Gauge

Dial Indicators

• Dial Calipers– For inside, outside,

and depth measurements

– Manual scales or digital

– can measure in 0.001 inch increments

– Metric can measure in 2-millimeter increments

Dial Indicator• A plunger moves in and out

from the body of the indicator and rotates the measuring needle on a dial face.

• Dial indicators usually have either a 1" or 2" range and are calibrated in increments of .001".  A smaller dial reads each revolution of the larger dial in increments of 0.100".

Dial Gauges Uses• Centering cylindrical stock in a 4-jaw

chuck• Determining accuracy of lathe or mill

alignment• Determining runout of lathe spindle

and chucks• Monitoring depth of drilled holes• Monitoring vertical movement of

milling head• Determining if edges of a rectangular

workpiece are parallel

Pressure and Vacuum Measurements

• Pressure Gauges– Measures amount of pressure applied

to a closed, sealed system– Fitted into pressure line with

appropriate fittings– A manometer is an instrument that

uses a column of liquid to measure pressure, although the term is currently often used to mean any pressure measuring instrument.

Pressure manometer

Pressure and Vacuum Measurements

• Vacuum Gauges– Mechanical gauge measures

difference between atmospheric pressure and current state of system

– A vacuum gauge is used to measure the pressure in a vacuum.

– it is possible to measure system pressure continuously from 10 mbar down to 10−11 mbar.

Vacuum Manometer

Rahul