Training Module-Elementary Mechanic

TPC Indo Plastic and ChemicalsMechanical

Elementary Mechanic

Prepared By : WDP

EngineeringEngineering


INTRODUCTION TO BASIC MECHANICS

NEWTONS LAWSOF MOTION

1. Every body will continue in its state of rest, or uniform motion in a straight line, unless it is acted upon by an external force.

2. The rate of change of motion is proportional to the force producing the change and takes place in the direction in which the force acts.

3. For every action, there is an equal and opposite reaction.

STATICStatic deals with forces and their effects on rigid bodies at rest

DYNAMICDynamics deals with motion and the effects of forces acting upon rigid bodies in motion.



ACCELERATION

VELOCITY

PRESSURE

MASSMass is the quantity of matter a body contains.

FORCEForce is any action on a body which tends to change its size or shape, its state of rest, or its state of motion.

Velocity is the rate of change of position

Acceleration is the rate of change of velocity.

Force = Mass (kg) * Acceleration (m/s2) = kg m/s2 = Newton (N)

Gravity = 9.81 m/s2Acceleration = Velocity (m/s) time

Velocity = change in positiontime

= Force (N) area (m2)= Pascal (Pa)

PRESSUREPressure is force per unit are and acts in a direction normal to or at right angles to a surface


ENERGY

Energy is the capacity of a body or substance to perform work.


POTENTIAL

KINETIC

Potential energy is the ability of a body to do work by virtue of its position.

Potential Energy (PE) = Gravitational Force * Vertical heightPE = m * g * h

Kinetic energy is the ability of a body to do work due to its motion

Kinetic Energy (J) = 1/2 mass (kg) * velocity 2 (m/s)2

KE = Nm or Joule

POWER

Power is the rate of doing work.

Power (W) = work done (Nm) or (J) time (s)

Watt (W) = Joule / Second

WORK

If a force is applied to a body and causes it to move through a distance, then work is done.

Work (J) = Force (N) * Distance (m)Joule (J) = Newton Meter (Nm)

TPC Indo Plastic and ChemicalsMechanical FORCES AND MOMENTS

FORCE

MO

ME

NT

FULCRUM

EQUILIBRIUMBEAM

A force is the pull or push exerted on a body, and it may make a body move or bring it to rest.

A force acting at any distance from a point will tend to produce a rotation around that point.

Moment = Force x perpendicular distance = Nm

Single support about which a bar is free to rotate.

A

100 N 40 N

1 m 2 m

Taking moments about A:

Clockwise moment = 40 N * 2 m = 80 Nm

Counter moment = 100 N * 1 m = 100 Nm

Bar will move in counter clockwise dire

Upward forces = Downward forces

Forces acting sideways to right = Forces acting sideways to left

Clockwise moments = Counter clockwise moments

STEPS TO SOLVE

1. State taking moment about fulcrum

2. State clockwise = counter3. Substitute known values

& solve for unknown

A beam is a rigid member or bar supported in some way so that it is capable of carrying a load or system of loads

SIMPLY SUPPORTED

Point load Point load

Support Support

REACTIONREACTION

Beam rests on supports so that it is free to bend without restriction from the supports.


SIMPLES MACHINES

A machine is a device which receives energy from some source and uses this energy to do work.

MACHINE

SIMPLE MACHINE

LEVER

LAW OF CONSERVATION OF

ENERGY

VELOCITY RATIO (VR)

PULLEY

PERCENT EFFECIENCY

ACTUAL MECHANICAL ADVANTAGE (MA)

A simple machine is one which receives energy by means of a single applied force, and produces work by means of a single output force.

Work Input = Work Out + Work Wasted

MA = Load Effort

A lever is a straight bar or other rigid structure supported at a fulcrum in such a way that a small force (or effort) can balance or move a much larger load.

VR = distance moved by effort distance moved by load

Percentage efficiency = actual MA * 100 VR

VR = # ropes supporting load block = 5

Load Block

WHEEL & AXLE

D d

VR = D d

6 m2 m

VR = 6 = 3 2

load Effort


SCALAR

VECTOR

SPACE DIAGRAM

RESULTANT

CO-PLANAR

CONCURRENT VECTORS

STEPS DRAWVECTOR DIAGRAM

A scalar quantity is one which has magnitude only and which can be completely described by a number with the necessary units.

A Vector is a quantity which has magnitude and direction

VELOCITY is a Vector because itHas speed and direction.

= DISPLACEMENT

DEFINE NORTHPLOT FROM ONE POINTSCALE = MAGNITUDE

Single vector replace system of vectors

Vectors who’s lines meet at one point

Located on same plane.

1. Determine north2. Select scale3. Order & Draw head to tail.

N30˚

20˚

N 30˚

20˚

SCALARVECTOR

TPC Indo Plastic and ChemicalsMechanical LINEAR VELOCITY & ACCELERATION NEWTONS LAWS

OF MOTION

Every body will continue in its state of rest, or uniform motion in a straight line, unless it is acted upon by an external force.

The rate of change of motion is proportional to the force producing the change and takes place in the direction in which the force acts.

For every action, there is an equal and opposite reaction.

1

2

3

MOTIONLINEAR

CIRCULAR

DISTANCE

DISPLACEMENT

AVERAGESPEED

VELOCITY

AVERAGE VELOCITY

Quantity & has magnitude only

Quantity Magnitude and change in position Relative to some reference point.

Distance traveled from A to D is 11 m

Displacement from A to D is 3 m north A B

CD

4 m

3 m

4 m

N

= Distance traveled Total time

= speed + direction

= displacement time taken

Scalar = 20 m/s

Vector = 20 m/s North

s = µ + v * t 2s = displacement (m)µ = Initial Velocity (m/s)v = Final Velocity (m/s)t = time (s) velocity

time

ACCELERATIONRate of change of velocity (m/s2)

v = µ + at

v2 = µ2 + 2as

s = µt + 1/2 at2

a = v - µ t

= Change of Velocity time

DERIVED FORMULAUNIFORM LINEAR MOTION


ENERGY

Force is a push or pull exerted on an object, which causes it to change state of motion or rest, shape or size.

1 N = 1 kg/m/s2

Variable force is practical application in reality

POTENTIAL

KINETIC

ABSOLUTE

GAGE

If a force is applied to a body and causes it to move through a distance then work is done by the force.

Work done (J) = Force (N) * Distance (m)

Force

Distance

area

Pressure is the measure of force per unit area

Absolute = Gage + Atmosphere (101.3 kPa)

Pressure (Pa) = Force (N) Area (m2)

Power is the rate of doing work.

1 horsepower = 746 watts1 kilowatt hour = 3.6 MJ

Power (Watt) = Work (J) Time (s)

PE = mass * g * h

KE = 1/2 mv2

WORK

FORCE

PRESSURE

POWER

Force = Mass (kg) * Acceleration (m/s2)

TPC Indo Plastic and ChemicalsMechanical FRICTIONS LAWS

COEFFICIENT OFFRICTION

ROLLING

The resistance which opposes the motion of a wheel or roller as it rolls along a surface.

Force of friction is proportional to the force which presses two surfaces together. (downward force doubled friction doubled)

Static friction is always greater than kinetic friction

The forces of friction, kinetic or static, are not affected by the area of the two surfaces in contact.

Kinetic friction is not affected by the speed of the body.

Force of friction either kinetic or static is affected by the relative roughness of the two surfaces.

Kinetic friction is greater than rolling friction.

Fw Gravity

FA Start Move

RN Reaction

FF Frictionµ = FF

RN

FF = Force of friction FA = Force start movingRN = Force opposing gravity

µ = FF

RN

FF = Force of friction FA = Force keep movingRN = Force opposing gravity

Fw Gravity

FA Start Move

RN Reaction

FF Friction

FORCE OF FRICTION

A force that opposes motion of one surface over another.

STATIC

The resistance which opposes the initial movement of a body at rest. KINETIC

The resistance which opposes the continued movement of an object.

FLUID

The resistance to movement within the

layers of a fluid

12

3

45

6

TPC Indo Plastic and ChemicalsMechanical STRESS

STRAIN

ELASTICITYSTIFFNESS

PLASTICITY

DUCTILITYTOUGHNESS

BRITTLENESS

HARDNESS

ULTIMATE STRESS

ALLOWABLE STRESS

ELASTIC LIMIT

MAX ALLOWABLE LOAD

FACTOR OF SAFETY

TENSILE

COMPRESSIVE

SHEAR

Internal resistance in a material developed to counteract an external force (load).

The ability of a material to return to its original shape after the force or load which

caused the deformation is removed.

The ability of a material to resist a change in shape or size when a load is applied.

The ability of a material to retain its deformed shape when the load

causing the deformation is removed.

The ability of a material to be stretched and reduced in cross section without breaking.

The ability of a material to absorb energy before breaking.

Brittle materials break without much deformation occurring before fracture.

The ability to resist penetration.

STRESS (Pa) = Load (N) Area (m2)

TieP (N) P (N)

StrutP (N) P (N)

Tensile stress (Pa) = Load (N) P Area (m2) A

Compressive stress (Pa) = Load (N) P Area (m2) A

A

B

C

X XP

P

SHEAR PLANE

The stress at the instant a material breaks.

The amount of stress that a material is allowed to carry

The maximum stress value that the material can be subjected to and still return to its original size and shape when load is removed.

The greatest load that can be applied to a material under its design conditions.

Factor of Safety = Ultimate Stress Allowable Stress

A measure of the deformation produced in a member by a load.

Strain = ∆ l Change in length l Original Length

TPC Indo Plastic and ChemicalsMechanical POWER TRANSMISSION

BELT DRIVE

BELT SLIPPAGE

LINEAR VELOCITY

ROTATIONAL SPEEDOF PULLEY

PULLEY TRAIN

GEAR DRIVES

INTERMEDIATEGEARS

BACKLASH

CHAIN DRIVE

GEAR TRAIN

DRIVERFOLLOWERSLACK SIDE

TIGHT SIDEF1

F2

• TRANSMISSION OF POWER• CHANGE SPEEDS

INCREASE POWER BY• INCREASE ANGLE OF CONTACT• INCREASE TENSION, REDUCE SLIPPAGE

% EFFECIENCY = POWER OUT x 100 POWER IN

POWER (W) = (F1 - F2) x Speed of Belts (m/s)TRANSMISSION

F1 = tension tight side (N)F2 = tension slack sideLinear Velocity = r/min x 2 πR

60

POWER TRANSMISSION

Dia 1 = r/min 2Dia 2 r/min 1

A B C D

Dia A = r/min BDia B r/min A

R/min C = r/min B

Dia C = r/min DDia D r/min C

Same as belt only opposite rotation

Same as gear drive

No change of speed r/minChange direction

Similar to pulley train

# teeth 1 = r/min 2# teeth 2 r/min 11 2

Start/ Stop slop in teeth mesh canCause excessive forces


Elementary Elementary

MechanicMechanic

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Training Module-Elementary Mechanic