ST. MARTIN’S ENGINEERING COLLEGE - smec.ac.insmec.ac.in/sites/default/files/lab1/Strength of...

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DHULAPALLY, SECUNDRABAD.

(Approved by AICTE, Affiliated to JNTU, Hyderabad)

STRENGTH OF MATERIALS

LABORATORY MANUAL

DEPARTMENT OF

CIVIL ENGINEERING

ST. MARTIN’S ENGINEERING COLLEGE

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LIST OF EXPERIMENTS:

1. To study the universal testing machine(U.T.M)

2. To determine hardness of metal using Rockwell Hardness test.

3. To determine hardness of metal using Brinell Hardness test.

4. Torsion test on mild steel rod. 5. To determine impact strength of steel.(by izod test)

6. To determine impact strength of steel.(by charpy test)

7. To determine Young’s modulus of elasticity of different materials of

beam simply supported at ends. 8. To determine the stiffness of the spring and modulus of rigidity of

material of the springwire 9. To determine the compressive strength of wood or concrete.

ST.MARTIN’S College of Engineering and Technology

STRENGTH OF MATERIALS Department of Civil Engineering

MANDATORY INSTRUCTIONS

1. Students should report to the labs concerned as per the timetable.

2. Record should be updated from time to time and the previous experiment must

be signed by the faculty in charge concerned before attending the lab.

3. Students who turn up late to the labs will in no case be permitted to perform the

experiment scheduled for the day.

4. After completion of the experiment, certification of the staff in-charge concerned

in the observation book is necessary.

5. Students should bring a notebook of about 100 pages and should enter the

readings/observations/results into the notebook while performing the

experiment.

6. The record of observations along with the detailed experimental procedure of the

experiment performed in the immediate previous session should be submitted

and certified by the staff member in-charge.

7. Not more than FIVE students in a group are permitted to perform the experiment

on a set up.

8. The group-wise division made in the beginning should be adhered to, and no mix

up of student among different groups will be permitted later.

9. The components required pertaining to the experiment should be collected from

Lab- in-charge after duly filling in the requisition form.

10. When the experiment is completed, students should disconnect the setup made

by them, and should return all the components/instruments taken for the

purpose.



11. Any damage of the equipment or burnout of components will be viewed

seriously either by putting penalty or by dismissing the total group of students

from the lab for the semester/year.

12. Students should be present in the labs for the total scheduled duration.

13. Students are expected to prepare thoroughly to perform the experiment before

coming to Laboratory.

14. Procedure sheets/data sheets provided to the students groups should be

maintained neatly and are to be returned after the experiment.

15. DRESS CODE:

i. Boys - Formal dress with tuck in and shoes.

ii. Girls - Formal dress (salwar kameez).

Iii. Apron in blue color for both boys and girls.

iii. Wearing of jeans is strictly prohibited



EXPERIMENT -1: TO STUDY THE UNIVERSAL TESTING MACHINE(U.T.M)

1.1 OBJECTIVE: - To conduct tension test on a mild steel bar to find its

(i) Yield stress (ii) ultimate stress (iii) breaking stress (iv) percentage elongation (v)

percentage reduction in area of cross section and (vi) Young's modulus of Elasticity

for steel material.

1.2 EQUIPMENT: -Tension tasting machine (5 to 400 KN capacity); vernier calipers, and

extensometer.

1.3 GENERAL: - The two essential parts of a testing machine are

(i) a means for applying load to specimen and

(ii) a means for measuring the applied load. In addition to these basic features there

are a variety of , accessory parts such as those for gripping or supporting 'the test

pieces, controllers, recorders, speed indicators and shock absorbers.

The load may be applied by mechanical means through these of screw-gear

mechanism in which case the machines are referred to as hydraulic jack; the

machine is called a hydraulic machine. Some machines are designed for one kind of

test only such as compression or tension. However if a machine is designed to test a

specimen in tension, compression, flexure, ahanr etc., it is called universal testing

machine. (U. T .M)

DESCRIPTION: - In the tension testing machine, the load is applied through the use

of screw-gear mechanism. The machine consists of base and vertical channels, which

support the load measuring unit. The base houses the drive unit. The drive is

affected by an eccentric motor whose stroke is transmitted through set of pulleys to

the spindle. Load can also be applied manually by rotating loading wheel: when pull

is applied to specimen, the pendulum gets deflected from its vertical position in

proportion to pull applied and the tensile force is indicated on the dial by the drag

pointer. To record the curve of the test, the machine is equipped with autographic

recorder. To prevent sudden fall of the pendulum rod on rupture of the specimen,



the damping unit is provided which ensures that thependulul1l red slowly goes back

to its vertical position. When the pendulum rod falls back, the drag pointer rod

remains in its position to' indicate maximum strength developed during the

strength.

The machine has three loading ranges, 1 ton, 2.5 ton, and 5 ton. Attaching

weight discs, on the pendulum rod sets, the measuring ranges.

0 – 1.0 ton = disc A

0 - 2.5ton =>discs A+B+C

0 -5.0 ton => discs A+B+C+D+E+F

The autographic recorder consists of an aluminum drum on which a graph

paper is wound. Curve is drawn with a pen connected to the pendulum rod through

rack.

On drum, the tensile force is recorded on horizontal axis and the elongation

is recorded in the direction of vertical axis. If the graph paper is taken off and turned

by'90 degrees, the curves are obtained in the usual representation i.e. load on y-axis

and extension on x-axis.

PROCEDURE:

(1) Considering the breaking strength of the test specimen select a proper loading

range out of the three ranges provided on the machine. Place suitable weight discs

on the pendulum at the back of the machine.

(2) Depending on the dimensions of the test specimen, appropriate gripping jaws

should be installed in grip housing.

(3) Measure the diameter of the specimen and mark gauge length accurately.

(4) Fix the specimen in the center of grips. Fix the extensometer to the specimen.

(5) Set drag pointer and dial gauges in extensometer to zero.

(6) Note the elongation reading for each suitable increment to load until the

specimen yields. The yielding of the specimen is observed from the fast movement



of the extensometer needle for no increment of load. At this stage extensometer is

removed. The load increases gradually and reaches a maximum value called ultimate

load. After' reaching the ultimate load, specimen breaks. Note this breaking load.

The readings may be tabulated in a tabular form as shown below.

TABULATION: -

Load Extensometer reading

Stress E in

S.No applied in

Kq/cm2

Strain

Kg/cm2

In div In cm

In kg

Using stress strain values, stress strain curve is drawn. Young's modulus of

Elasticity is calculated from the graph.

Load at yield point in kg from graph =

Yield stress in kg/cm2 = Load at yield point

Initial c/s area

Ultimate load in kg =

Ultimate stress in kglcm2 = Ultimate load

Initial c/s area



Breaking load in kg =

Breaking stress in kg/om2 = Breaking Load

Initial c/s area

% Elongation = Change in length x 100

Original length

% Reduction in area of cross section = A - Al x 100

A

A - Initial area of c/s

Al - Area of c/s at the broken section =

Least.count of vernier caliper = 0.002,

TABULATION FOR MEASUREMENT OF DIAMETER: -

Trail No Main scale reading Vernier scale Diameter = M.S.R + L.C x

in cm coincidence in div V.S.C in cm

M.S.R

V.S.C

Average diameter in cm =

OUTCOME:- The student will be able to find out all the stresses in the stress strain

curve and the modulus of elasticity of given material.



EXPERIMENT NO: 02

ROCKWELL HARDNESS TEST

OBJECTIVE: To determine the hardness number of different materials such as Steel,

Brass and Copper.

EQUIPMENT : Rockwell hardness testing machine, Specimen, Allen key, Indentor.

THEORY: Hardness of material is the property by virtue of which it offers resistance

to indentation or penetration or abrasion by other bodies. Hardness can be

measured in following ways.

1. Scratch hardness

2. Rebound hardness-Shore'scleroscope

3. Penetration hardness-Vickers, Rockwell and Brinnel.

Penetration hardness is the one, which is determined in this test. The test

essentially consists of first applying a small or minor load on the specimen through

an indentor. A major load is then added to the minor load and is allowed to act on

the indentor. The dashpot arrangement provided in the machine enables slow

application of the load with out shock or impact .The load will cause both plastic and

elastic deformation on the specimen. When the major load is removed, there is a

recovery of elastic deformation and the plastic deformation in the specimen is a

measure of its hardness, though the actual mode of measuring the hardness defers

from method to method.

Description of Machine: The machine has a cast iron body and has a small platform

over which the test specimen is placed. The plat form is supported by a cylindrical

stem, which has a screw out side. The stem and the platform can be fixed in a

centralized position. The dial gauge, which is mounted in the front of the machine, is

in contact with the loading lever and gives the indentation or penetration of the

indenter on the specimen.

There are two types of indenters supplied with the machine.

1. 1/16 inch (l.5875mm) diameter steel ball indentor.



2. Diamond type indenters with 120° cone angle.

The total 1oad to be applied varies with type of indenter. In all the tests the

initial or minor load is 10 kg. This can be applied by raising the flat form using the

hand wheel so that the indicator presses the specimen that causes the deflection of

the dial gauge pointer. The hand wheel is rotated until the large and small pointers

of dial gauge records a reading against the set position. (i.e. the large pointer stands

at SET position & small pointer stands at red point marked at '3'.)

The major load to be applied for various indentors is indicated below:

Indentor Scale Minor load (Kg) Major load (Kg) Total load (Kg)

2.5mm B (Red) 10 90 100

diameter

5mm C (Black) 10 140 I5O

Diameter

A load selector disc provided on the right hand side of the machine enables

the application of the correct major load. The major load can be applied by rotating

the lever below the load selector switch. Extreme anticlock position (i.e. north-west

position) is the unloaded position. Rotation of the lever in the clockwise direction or

north - east position enables application of the major load on the indentor. It is to be

noted that the load marked on the disc is the major plus minor i.e. the total load.

To avoid sudden application of the major load, a dashpot is provided in the

loading mechanism. After the lever is turned to load position, the pointer of the dial

gauge will be observed to be moving slowly for a few seconds indicating slow

application of the load. The lever should be brought back to unload position only

after the dial gauge pointer has come to rest.

The dial gauge is calibrated to give directly the Rockwell hardness number

both as per B scale measure and C scale measure.



PROCEDURE:

1. Note the material of the specimen which decide the ball and load to be selected.

2. Fix the suitable indenter

3. Place the specimen on the platform.

4. Make sure that the machine is in unload position and adjust the load to the

required value with the help of load selector disc.

5. Raise the platform by means of rotating hand wheel until the specimen presses

against the indentor and both the small and large pointers of the dial gauge show

SET position.

6. Now apply the load with the help of loading lever and wait for 30 seconds.

7. Remove the load on the specimen with the help of loading lever and note down

the reading of the pointer on the corresponding scale of the dial gauge.

8. Repeat the experiment and tabulate the readings.

9. Lower the platform and remove the indentor.

TABULATION

S.No. Specimen Indentor Load Scale Used R.H.N

Result: The average RHN of the specimen is

OUTCOME:- The student will be able to find out the hardness of the material.

Precautions:

1. The hand load must be applied only when the loading lever is in un-load position

2. The pointer in the smaller should not cross the red spot (Le. '3') during the

application of primary or hand load.



EXPERIMENT NO: 03

BRINNEL HARDNESS

OBJECTIVE: To determine the Brinnel hardness number of the given materials such

as Steel, Brass and Copper.

Apparatus: Brinnel hardness testing machine, Microscope, Specimen, Allen key,

Indentor.

Theory: Hardness of material is the property by virtue of which it offers resistance to

indentation or penetration or abrasion by other bodies. Hardness can be measured

in fallowing ways.

1. Scratch hardness

2. Rebound hardness-Shore'scleroscope

3. Penetration hardness-Vickers, Rockwell and Brinnel.

Penetration hardness is the one, which is determined in this test. The test

essentially consists of first applying a small 0r minor load on the specimen through

an indicator. A major load is then added to the minor load and is allowed to act on

the indenter. The dashpot arrangement provided in the machine enables slow

application of the load without shock or impact. Hardness in the case of Rockwell

test is directly based on the depth of plastic deformation under the major load. Also

it depends on the load and type of indenter used. This is not the case with Brinnel

hardness test.

Brinnel Hardness Number (B.H.N) = PIA

Where, P= Total load applied in kg,

A = Surface area of the indentation measured in mm2

Only hard steel balls of diameter ranging from 1 mm to 10 mm are used as

indentors. For the same material same B.H.N value will be obtained irrespective of

the total load and indentor diameter used. Usual diameters of indentors used in



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practice are of 2.5mm, 5mm, and 10mm. The standard combinations of load and the

diameter of the ball that may be used on various materials are indicated below.

S.NO PD2 Ratio Representative material

1 30 Steel, Cast iron

2 10 Copper alloys

3 60 to 20 Copper, Aluminium

4 Less than 20 Lead, Tin and their alloys

The loads to be selected for different indentors are calculated as follows:

Example 1: Let the specimen made of Steel.

If D = 10mm, desirable value ofP = 30 X 102= 3000 kg.

IfD = 2.5 mm, desirable value ofP = 30 x 2.52

= 187.5 kg.

Example 2: Let the specimen made of copper alloy.

If D = 5mm, desirable value of P = 10 X 52 = 250 kg.

Description of Machine: The machine has a cast iron body and has a small platform

over which the test specimen is placed. The plat form is supported by a cylindrical

stem, which has a screw out side. The stem and the platform can be fixed in a

centralized position. The dial gauge, which is mounted in the front of the machine, is

in contact with the loading lever and gives the indentation or penetration of the

indentor on the specimen.

There are two types of indentors supplied with the machine.

2.5 mm diameter steel ball indentor.

5 mm diameter steel ball indentor



The total load to be applied differs with indentor. In all the tests the initial or

minor load is 10 kg. This can be applied by raising the flat form using the hand wheel

so that the indicator presses the specimen that causes the deflection of the dial

gauge pointer. The hand wheel is rotated until the large and small pointers of dial

gauge records a reading against the set position. (Le. the large pointer stands at SET

position & small pointer stands at red point marked at '3'.)

P/D 2 Load. P

Indentor

Ratio

(kg)

2.5mm diameter 30 187.5

5mm Diameter 10 250

A load selector disc provided on the right hand side of the machine enables

the application of the correct major load. The major load can be applied by rotating

the lever below the load selector switch. Extreme anticlock position (i.e. north-west

position) is the unloaded position. Rotation of the lever in the clockwise direction or

north - east position enables application of the major load on the indentor. It is to be

noted that the load marked on the disc is the major plus minor i.e. the total load.

To avoid sudden application of the major load a dashpot is provided in the

loading mechanism. After the lever is turned to load position, the pointer of the dial

gauge will be observed to be moving slowly for a few seconds indicating slow

application of the load. The lever should be brought back to unload position only

after the dial gauge pointer has come to rest.

Procedure:

l. Note the material of the specimen which decide the ball and load to be selected.

2. Fix the suitable indenter

3. Place the specimen on the platform.



4. Make sure that the machine is in unloading position and adjust the load to the

required value with the help of load selector disc.

5. Raise the platform by means of rotating hand wheel until the specimen presses

against the indenter and both the small and large pointers of the dial gauge show

SET position.

6. Apply the load with the help of loading lever and wait for 30 seconds.

7. Now unload the machine and take the specimen out.

8. Measure the diameter‘d’ of the indentation using Brinnel Microscope

9. Repeat the experiment and tabulate the readings.

OBSERVATION AND TABULATION :

Load

Diameter

of

Diameter of Surface area of

the

Indentation in

mm2

S.No.

Specime

n Applied

the

indentor B·H.N

indentation

A=ПD*D-√D2 –d

2

]

(kg) D in mm

d in mm

Result: The average B.H.N of the specimen is

OUTCOME:- The student will be able to find out the hardness of the material.

Precautions:

1. The hand load must be applied only when the loading lever is in un-load

position

2. The pointer in the smaller should not cross the red spot (i.e. '3') during the

application of primary or hand load.



EXPERIMENT NO: 04

TORSION TEST

OBJECTIVE: To determine the Modulus of rigidity of the material of the given

specimen using torsion testing machine.

EQUIPMENT: Torsion testing machine, specimen, vernier calipers.

THEORY: When a straight circular bar of a given material is subjected to a torque 'T',

the angle of twist 'θ' in radians over a length 'L' of the bar is given by

θ = (T x L) / (G x J)

Where J = Polar moment of inertia = (П d4

)/ 32

Description of the machine: The torsion testing machine consists of two sturdy

stands on which the base frame is firmly fixed. The driving chuck is fixed on base

frame to the left end of the machine, torque indicator and the stationary chuck is

fixed on the right end of machine. The torque applied by the motor or hand wheel is

transferred to the pendulum, which in turn gets deflected. A dummy pointer (red) is

provided on the dial to indicate the amount of torque required for breaking the

specimen A dash pot is provided in the dynamometer panel which serves for slow

release of load when the specimen breaks. An angle-measuring disc is provided to

facilitate the measurement of angle of twist.

Procedure:

1. Measure the diameter and length of the specimen.

2. Adjust the pendulum weight and corresponding range on the dial according to the

specimen to be tested.

3. Fix one end of the specimen in the driving chuck.

4. Move the trolley towards, the fixed chuck and fix the other end of the specimen.

5. Adjust the angle measuring disc and the torque-measuring dial to zero.

6. Apply the torque by rotating the hand wheel. Note down the value of the torque

for each 10 of the angle of twist

7. Repeat the step 6 and take five readings.


8. Tabulate the readings.

RESULT:- The modulus of rigidity of the given specimen is

OUTCOME:- The student will be able to find out the torque at given angle of twist

and the rigidity modulus of the material.

EXPERIMENT NO: 05 DATE:

IMPACT TEST

OBJECTIVE: To conduct Izod Impact Test on a given specimen to determine the

toughness of the material of the specimen.

EQUIPMENT: Impact testing machine, 10x10 square specimen, vernier calipers

THEORY : The machine combines the facility for performing different standard

impact tests such as

1. Izod Test

2. Charpy Test.

The materials, which can be tested on this machine include Steel, Copper, Brass and

Alloys.

Machine specifications: Machine has the fallowing ranges

(a) 300 1 for Charpy impact test and

(b) 168 J for Izod impact test.

The machine has a pendulum of specified weight and effective length of

O.8I5m. For each of the test, the appropriate grips and striking tool have to be used.

The test essentially consists of holding the specimen at the at the position with

proper grip, raising the pendulum through a specified angle releasing it to strike the

specimen to cause fracture and measuring the energy lost in breaking the specimen.

The energy lost is directly read on the dial.

Technical data:

Weight of the pendulum = 21.79 kg.

Angle of drop pendulum = 900

Effective length of pendulum = 0.815 m

Geethanjali College of Engineering and Technology


Energy at impact = 21.79 x 9.81 x 0.815 x (1- Cos 90° ) = 168 J

The dial is gradated to read directly the energy lost at impact.

Specimen for Izod Test: Izod specimen made out of lO mm square has V-notch of

2mm depth with included angle of 45° at the section where it is required to fracture

by impact. (Ref. Fig. 1 )

Procedure:

1. Keep the pendulum in its initial position and lock it.

2. Fix the proper striker firmly to the pendulum.

3. Keep the specimen in position in such a way that the notch on the specimen facing the

pendulum. 4. Release the pendulum and note down the reading of the pointer on the dial which is

the energy absorbed by the specimen at fracture.

OBSERVATIONS

Evaluation Test: The impact strength of the specimen is given by I=K/A

Where, K = the energy absorbed by the specimen, J

A = Area of cross section of the specimen below the notch, m2

Result: Energy absorbed by the specimen at fracture is

Impact strength of the specimen is

OUTCOME:- The student will be able to find out the energy absorbed by the material at

the time of fracture and the impact strength of the material.

Precautions: Before releasing the pendulum, students should make sure that

nobody is standing in the swing zone of the pendulum.

EXPERIMENT NO: 06 DATE

IMPACT TEST – CHARPY

OBJECTIVE: To conduct Charpy Impact Test on a given specimen to determine the

toughness of material of the specimen.

APPARATUS: Impact testing machine, 10x10 square specimen, vernier calipers

Description of the Machine:

The machine combines the facility for performing different

standard impact tests such as 1. Izod Test

2. Charpy Test.

The materials that can be tested on this machine include Steel, Copper, Brass and

Alloys.

Machine specifications: Machine has the fallowing ranges.

(a) 300 J for Charpy impact test and

(b) 168 J for Izod impact test.

The machine has a pendulum of specified weight and effective length of

0.815m. For each of the test, the appropriate grips and striking t001 have to be

used.

The test essentially consists of holding the specimen at the at the position

with proper grip, raising the pendulum through a specified angle releasing it to strike

the specimen to cause fracture and measuring the energy lost in breaking the

specimen. The energy lost is directly read on the dia1.

Technical data:

Weight of the pendulum = 21.02 kg.

Angle of drop of pendulum 141.8°

Effective length of pendulum = 0.815111



Energy at impact = 21.79 x 9.81 x 0.815 x (1- Cos 140°):0-: 300 J

The dial is graduated to read directly the energy lost at Impact.

Specimen for Izod Test: Specimen for charpy is made out of 10 mm square rod having V -

notch of 2mm depth with included angle of 45° at the section where it is required to fracture

by impact. (Ref. Fig. 1 )

Procedure:

1. Keep the pendulum in its initial position and lock it.

2. Fix the proper striker firmly to the pendulum.

3. Place the specimen on specimen support touching end stop. The specimen should be

placed in such a way that the notch on the specimen is averted to the direction of impact of

the pendulum.

4. Release the pendulum and note down the reading of the pointer on the dial which is the

energy absorbed by the specimen at fracture.

Evaluation Test: The impact strength of the specimen is given by I=K/A

Where, K = the energy absorbed by the specimen, J

A = Area of cross section of the specimen below the notch, m2

Result: 1. Energy absorbed by the specimen at fracture is :

2. Impact strength of the specimen is :

OUTCOME:- The student will be able to find out the energy absorbed by the material at the

time of fracture and the impact strength of the material.

Precautions: Before releasing the pendulum, students should make sure that nobody is

standing in swing zone of the pendulum.

EXPERIMENT NO: 07 DATE:

SIMPLY SUPPORTED BEAM

OBJECTIVE: Determination of Young’s Modulus of the material Simply supported beam.

EQUIPMENT: Simply supported beam, hanger with weights, deflection guage, vernier

calipers and meter scale

PROCEDURE:-

1. Measure the dimension of the beam i.e. the length 'L’ the between knife edge

supports, width 'b' and depth‘d’

2. Fix the dial gauge at the center of the beam for measuring deflection. The needle of

the dial gauge should touch the bottom of the beam. 3. Place the hanger at a measured distance L1 from the fixed support. Record reading on

the dial gauge. Successively place the additional weight is added. Record the reading of

the dial gauge when each weight is added.

4. Repeat experiment by decreasing the weights and tabulated the reading.

TABULATION :

S.No Load Applied Dial gauge reading Deflection = Young’s

Avg x L.c modulus E

Kg N During During Average

loading unloading loading = N/mm2

in Div in Div in Div



Calculations:

The formula for deflection ‘δ’ at the centre for the ‘w’ applied at a distance ‘a’ from

one and is δ = WL13

48EI

Movement of inertia of the cross section of the beam, ‘I’ = bd3

mm4 12

Applying the above formula, the value of ‘E’ is E = WL3

48δI

Notation:

A – Left support

B – Right Supported

L – Length of the spam

W – Load applied.

RESULT : Young’s modulus of Elasticity ‘E’ of the material of the beam is =

OUTCOME:- The student will be able to calculate the deflection in a simply

supported beam at the given point of loading and the modulus of elasticity of the

given material beam.



EXPERIMENT NO: 08 DATE

SPRING TEST

OBJECTIVE: To determine the modulus of rigidity of material of the spring.

EQUIPMENT: Spring testing machine, spring, Vernier.

Theory: Springs are elastic members, which distort under load and regain their

original shape when load is removed. They are used in railway carriages, motorcars,

scooters, motorcycles, rickshaws, governors etc.

Different types of springs are:

1. Closely - coiled springs &Tension helical springs

2. Open-coiled springs & Compression springs,

3. Full- elliptical leaf springs,

4. Semi - elliptical leaf springs,

5. Cantilever leaf springs,

6. Circular springs.

Depending on their use, springs perform the following functions:

1. Absorb shock or impact loading as in carriage springs.

2. Store energy as in Clock springs.

3. Supply forces to and to control motions as in brakes and clutches

4. Measure forces as in spring balance.

5. Absorb the vibrations.

Springs are usually made of either High carbon steel (0.7% to 1.0%) or

Medium carbon alloy steels, Phosphor bronze, Brass and 18/8 Stainless steel. Other

metal alloys are also used for corrosion resistance.

Deflection of a closely - coiled spring of circular cross section is given by,



δ = δ W D3 n / Gd

4

Where W = Load applied on the spring,

D = Mean diameter of the coil of the

spring, d = Diameter of the spring wire,

n = Number of turns of the spring coil,

G = Modulus of rigidity of the spring material.

Procedure:

1. Measure the Mean diameter (D) of the coil and wire diameter (d) of the spring

using Vernier calipers.

2. Count the number of turns (n) of the spring

3. Insert the spring in the two jaws of the spring testing machine

4. Apply the load slowly with the help of handle until the spring deflects by say 5mm

and note down the load on the respective dial corresponding to the pendulum load

setup.

5 .Repeat the experiment and tabulate the readings.

OBSERVATIONS AND TABULATIONS:

Mean diameter of the coil of the spring, D =

Diameter of the spring wire, d =

No. of turns of the spring, n =

Tabular Column:

S.No Load W Deflection, Stiffness Modulus of

δ in mm K = W/δ rigidity,

N Kgf

G = δ = 8 WD3

Calculatios: The rigidity modulus of the spring material is calculated as follows:

δ = 8 WD3 n/d

4

PRECAUTIONS:

1. Take the reading from the scale corresponding to the set pendulum weight.

2. Apply the load gradually.

3. Remove the load carefully and remove the spring.

Result: Average rigidity modulus of the spring material is

OUTCOME:- The student will be able to find out the rigidity modulus of any given

spring.



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