SM New Final Manual1

ANNA UNIVERSITY - COIMBATORE THE KAVERY ENGINEERING COLLEGE

M.KALIPATTI, METTUR (TK), SALEM (DT) – 636453DEPARTMENT OF MECHANICAL ENGINEERING

STRENGTH OF MATERIALS LABORATORY MANUAL

IV SEMESTER MECHANICAL ENGINEERING (R-2008 SYLLABUS)

Name of the student: ______________________________________________

Register Number : ______________________________________________

Prepared By

Sasikumar.M & Sudhagar.M

Department of Mechanical Engineering

Strength of Materials Lab

INDEXThe Kavery Engineering college Department of Mechanical

2


Ex. No Date Name of the experiment Page No Marks

ObtainedStaff

signature Remarks

1 TENSION TEST ON A MILD STEEL ROD 5

2 DOUBLE SHEAR TEST ON MILD STEEL 11

3 DOUBLE SHEAR TEST ON ALUMINUM 15

4 IMPACT STRENGTH TEST (CHARPY’S TEST)

19

5 IMPACT STRENGTH TEST ( IZOD TEST)

23

6 BRINELL HARDNESS TEST 27

7 ROCKWELL HARDNESS TEST 31

8 DEFLECTION TEST ON SIMPLY SUPPORTED BEAM (MILD STEEL)

35

9 COMPRESSION TEST ON HELICAL SPRING

39

10 TORSION TEST ON MILD STEEL ROD 43

11 EFFECT OF HARDENING IN IMPACT RESISTANCE OF STEEL

45

12 STUDY OF MICROSCOPIC EXAMINATION OF HARDENED AND TEMPERED SAMPLE

51

13 STUDY OF MICROSCOPIC EXAMINATION OF UNHARDENED SAMPLES

53

The Kavery Engineering college Department of Mechanical

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SYLLABUS

STRENGTH OF MATERIALS LAB (Common to Mechanical & Production)

LIST OF EXPERIMENTS

1. Tension test on a mild steel rod

2. Double shear test on Mild steel and Aluminum rods

3. Torsion test on mild steel rod

4. Impact test on metal specimen

5. Hardness test on metals - Brinnell and Rockwell Hardness Number

6. Deflection test on beams

7. Compression test on helical springs

8. Strain Measurement using Rosette strain gauge

9. Effect of hardening- Improvement in hardness and impact resistance of steels.

10. Tempering- Improvement Mechanical properties Comparison

(i) Unhardened specimen

(ii) Quenched Specimen and

(iii) Quenched and tempered specimen.

11. Microscopic Examination of

Hardened samples and

(ii) Hardened and tempered samples.

LIST OF EQUIPMENT (For a batch of 30 students)

1. Universal Tensile Testing machine with double 1

2. shear attachment – 40 Ton Capacity

3. Torsion Testing Machine (60 NM Capacity) 1

4. Impact Testing Machine (300 J Capacity) 1

5. Brinell Hardness Testing Machine 1

6. Rockwell Hardness Testing Machine 1

7. Spring Testing Machine for tensile and compressive loads (2500 N) 1

8. Metallurgical Microscopes 3

9. Muffle Furnace (800 C)

Quantity: one each. Total Number of Periods: P=45The Kavery Engineering college Department of Mechanical

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Exp. No: 1 TENSION TEST ON A MILD STEEL RODDate :

AIM:To conduct tension test on the given specimen and determine the following

Yield Stress

Nominal stress

Actual breaking Stress

Ultimate stress

Percentage of elongation

Percentage reduction in cross sectional area / E

APPARATUS REQUIRED:

Universal Testing Machine (UTM)

Mild steel specimen

Ruler

Divider

Vernier caliper

THEORY:

The tensile test is most applied one, of all mechanical tests. In this test ends of test piece are

fixed into grips connected to a straining device and to a load measuring device. If the applied load is

small enough, the deformation of any solid body is entirely elastic. An elastically deformed solid

will return to its original from as soon as load is removed. However, if the load is too large, the

material can be deformed permanently. The initial part of the tension curve which is recoverable

immediately after unloading is termed. As elastic and the rest of the curve which represents the

manner in which solid undergoes plastic deformation is termed plastic. The stress below which the

deformations essentially entirely elastic is known as the yield strength of material. In some material

the onset of plastic deformation is denoted by a sudden drop in load indicating both an upper and a

lower yield point. However, some materials do not exhibit a sharp yield point. During plastic

deformation, at larger extensions strain hardening cannot compensate for the decrease in section

and thus the load passes through a maximum and then begins to decrease. This stage the “ultimate

strength”’ which is defined as the ratio of the load on the specimen to original cross-sectional area,

reaches a maximum value. Further loading will eventually cause ‘neck’ formation and rupture.


5


OBSERVATION:

1. Given material of specimen = _____

2. Initial diameter of specimen d1 = ____

3. Initial gauge length of specimen L1 = ______

4. cross-section area of specimen A1 = _____

5. Final length after specimen breaking L2 =______

6. Diameter of specimen at breaking place (Neck Dia.) d2 = ______

7. Cross section area at breaking place (Neck area) A2 = ______

8. Load of yield point = ______

9. Ultimate load of specimen =______

10.Breaking load of specimen = ______

TABULATION:

SL.NOLOAD

( KN)EXTENSION(mm) STRESS

(N/mm2)STRAIN


6


FORMULAE USED:

Yield Load 1) Yield Stress = N/mm2

Cross Sectional Area

Ultimate Load 2) Ultimate Stress = N/mm2

Cross Sectional Area

Breaking Load 3) Nominal Breaking Stress = N/mm2

Cross Sectional Area of Specimen

Breaking Load 4) Actual Breaking Stress = N/mm2

Neck Area

Change in length 5) Percentage of Elongation = x 100 % Original gauge Length

Change in area 6) Percentage reduction in = x 100 % Area of cross section Original area


7


TENSILE TESTING MACHINE

GRAPH:

Where,P– Proportional LimitE – Elastic limitYU – Upper Yield PointYL – Lower Yield PointThe Kavery Engineering college Department of Mechanical

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S – Ultimate Tensile strengthB – Fracture point


9


PROCEDURE:

1. Measure the original length and diameter of the specimen. The length may

either be length of gauge section which is marked in the specimen with a

preset punch.

2. Insert the specimen into grips of the test machine and attach strain

measuring device to it.

3. Begin the load application and record load versus elongation data.

4. Take readings more frequently and record as yield point is approached.

5. Measure elongation values with the help of dividers and a ruler.

6. Continue the test till fracture occurs.

7. By joining the two broken halves of the specimen together the final length

and diameter of specimen.

RESULT:

Different parameters of the given specimen are.

1. Yield stress = __________N/mm2

2. Ultimate stress = __________ N/mm2

3. Nominal breaking stress = __________N/mm2

4. Actual breaking stress = __________N/mm2

5. Percentage of elongation = __________ %

6. Percentage reduction in

Cross sectional area = __________ %


10



11


Exp. No: 2 DOUBLE SHEAR TEST ON MILD STEEL RODDate :

AIM:

To determine shear stress by conducting shear test on the specimen under double shear.

APPARATUS REQUIRED:

Universal Testing Machine

Double Shear assembly box

Vernier caliper

Test specimen

THEORY:

A type of force which causes or tends to cause two contiguous parts of the body to

slide relative to each other in a direction parallel to their plane of contact is called the

shear force. The stress required to produce fracture in the plane of cross-section, acted on

by the shear force is called shear strength.

Place the shear test attachment on the lower table, this attachment consists of

cutter. The specimen is inserted in shear test attachment & lift the lower table so that the

zero is adjusted, then apply the load such that the specimen breaks in two or three pieces.

If the specimen breaks in two pieces then it will be in single shear & if it breaks in three

pieces then it will be in double shear.

FORMULAE USED:

Ultimate Shear Stress () = W N/mm2

2A

Where,

‘ ‘ - Ultimate Shear strength (N/mm2)

‘W’ - Ultimate load in (N)

‘A’ - area of the specimen in mm2


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OBSERVATION:

Given material of specimen = Mild steel

Diameter of specimen rod = ------

Maximum Shear Load = ------

TABULATION:

Specimen

Diameter of

the specimen

‘d’ (mm)

Cross

Sectional

area ‘A’(mm2)

Maximum

Shear Load

‘W’ (kN)

Ultimate

Shear stress

‘’ ( N/mm2)

Mild steel Rod


13


PROCEDURE:

1. The diameter of rod is measured using vernier caliper.

2. The specimen is inserted in position in double shear assembly box and is gripped

between the compression plates of universal testing machine.

3. The universal testing machine is switched on.

4. A suitable load is selected.

5. Left side valve is kept in a closed position and right side loading valve is gradually

opened and the load is applied on the specimen till it shear.

6. The maximum load taken by the specimen at that time is noted.

7. Then the machine is stopped and the ultimate shear strength of the specimen is

noted.

RESULT:

The ultimate Double shear stress of the Mild steel specimen is_____________ N/mm2.


14



15


Exp. No: 3 DOUBLE SHEAR TEST ON ALUMINIUM RODDate :

AIM:

To determine shear stress by conducting shear test on the specimen under double shear.

APPARATUS REQUIRED:

Universal Testing Machine

Double Shear assembly box

Vernier caliper

Test specimen

THEORY:

A type of force which causes or tends to cause two contiguous parts of the body to

slide relative to each other in a direction parallel to their plane of contact is called the

shear force. The stress required to produce fracture in the plane of cross-section, acted on

by the shear force is called shear strength.

Place the shear test attachment on the lower table, this attachment consists of

cutter. The specimen is inserted in shear test attachment & lift the lower table so that the

zero is adjusted, then apply the load such that the specimen breaks in two or three pieces.

If the specimen breaks in two pieces then it will be in single shear & if it breaks in three

pieces then it will be in double shear.

FORMULAE USED:

Ultimate Shear Stress () = W N/mm2

2A

Where,

‘ ‘ - Ultimate Shear strength (N/mm2)

‘W’ - Ultimate load in (N)

‘A’ - area of the specimen in mm2


16


OBSERVATION:

Given material of specimen = Aluminum rod

Diameter of specimen rod = ------

Maximum Shear Load = ------

TABULATION:

Specimen

Diameter of

the specimen

‘d’ (mm)

Cross

Sectional

area ‘A’(mm2)

Maximum

Shear Load

‘W’ (kN)

Ultimate

Shear stress

‘’ ( N/mm2)

Aluminum rod


17


PROCEDURE:

1. The diameter of rod is measured using vernier caliper.

2. The specimen is inserted in position in double shear assembly box and is gripped

between the compression plates of universal testing machine.

3. The universal testing machine is switched on.

4. A suitable load is selected.

5. Left side valve is kept in a closed position and right side loading valve is gradually

opened and the load is applied on the specimen till it shears.

6. The maximum load taken by the specimen at that time is noted.

7. Then the machine is stopped and the ultimate shear strength of the specimen is

noted.

RESULT:

The ultimate Double shear stress of the Aluminum specimen is_____________ N/mm2.


18



19


Exp. No: 4 IMPACT STRENGTH TEST (CHARPY’S TEST)Date :

AIM: To determine the impact strength of material of the given specimen by charpy’s

impact test.

APPARATUS REQUIRED: Impact testing machine

Charpy’s test specimen

Vernier caliper.

THEORY:

In manufacturing locomotive wheels, coins, connecting rods etc. the components

are subjected to impact (shock) loads. These loads are applied suddenly. The stresses

induced in these components are many times more than the stress produced by gradual

loading. Therefore, impact tests are performed to asses shock absorbing capacity of

materials subjected to suddenly applied loads. These capabilities are expressed as (i)

Rupture energy (ii) Modulus of rupture and (iii) Notch impact strength. Two types of notch

impact tests are commonly-

Charpy test

Izod test

In charpy’s test, the specimen is placed as 'cantilever beam'. The specimens have V-

shaped notch of 45°. U- Shaped notch is also common. The notch is located on

tension side of specimen during impact loading. Depth of notch is generally taken as

t.5 to t/3 where ’t’ is thickness of the specimen.


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TEST SPECIMEN:

OBSERVATION:

Breath of specimen (b) = ________ mm

Depth of specimen (d) = ________ mm

Length of specimen (l) = ________ mm

Depth of notch (d1) = ________ mm

TABULATION:TABULATION:

Specimen

Dimensions of Specimen Impact Energy

Observed‘ k ’

ImpactStrengthI = k / A

Breath‘b’

Depth‘d’

Length‘l’

Depth ofNotch

‘d’

mm mm mm mm J J / m2

MODEL CALCULATION:

Area of cross- section of specimen (A) = b X (d-d1) mm2

Impact energy observed (K) = _______ J

Impact strength (I) = K/A J/m2

FORMULAE USED : The Kavery Engineering college Department of Mechanical

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Notch Impact Strength I =K/A J/m2

Where,

I = Notch impact strength in J/m2

K = Impact energy absorbed by specimen in Joules

A = Area of the cross section of specimen below notch before test in m2

PROCEDURE:1) The hammer is raised and locked.

2) The pointer is set at maximum position of graduated energy of dial.

3) The safety load bar is placed horizontally arms of projecting bars.

4) The trigger is released and pendulum is allowed to swing. This actuates the pointer

to move in the dial.

5) See that no person is on within range to swing of pendulum.

6) The specimen is placed in such a way that notch is opposite to the direction of the

pendulum for contact centering of specimen. The end stop is provided.

7) The latches are released and pendulum is allowed to strike on specimen (or)

bending the specimen is noted in the dial.

8) Then the impact energy required for the rupture of the specimen is directly

measured on indicator.

RESULT : The Charpy impact strength is calculated as,

The impact strength of the given specimen (I) = J/m2


22


Exp. No: 5 IMPACT STRENGTH TEST (IZOD TEST)Date :The Kavery Engineering college Department of Mechanical

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AIM:

To determine the impact strength of the given specimen by Izod impact test.

APPARATUS REQUIRED:

Impact testing machine

Izod specimen

Vernier caliper.

THEORY:

In manufacturing locomotive wheels, coins, connecting rods etc. the components

are subjected to impact (shock) loads. These loads are applied suddenly. The stresses

induced in these components are many times more than the stress produced by gradual

loading. Therefore, impact tests are performed to asses shock absorbing capacity of

materials subjected to suddenly applied loads. These capabilities are expressed as (i)

Rupture energy (ii) Modulus of rupture and (iii) Notch impact strength.

Two types of notch impact tests are commonly-

Charpy test

Izod test

In Izod test, the specimen is placed as ‘cantilever beam’. The specimens have V-shaped

notch of 45°. U- Shaped notch is also common. The notch is located on tension side

of specimen during impact loading. Depth of notch is generally taken as t.5 to t/3

where’t’ is thickness of the specimen.

TEST SPECIMEN:


24


OBSERVATION:

Breath of specimen (b) = ________ mm

Depth of specimen (d) = ________ mm

Length of specimen (l) = ________ mm

Depth of notch (d1) = ________ mm

TABULATION:TABULATION:

Specimen

Dimensions of Specimen Impact Energy

Observed‘k’

ImpactStrengthI = k / A

Breath‘b’

Depth‘d’

Length‘l’

Depth ofNotch

‘d’

mm mm mm mm J J / m2

MODEL CALCULATION:

Area of cross- section of specimen (A) = b X (d-d1) mm2

Impact energy observed (K) = _______ J


FORMULAE USED:

Notch Impact Strength I =K/A J/m2


25


Where,

I = Notch impact strength in J/m2

K = Impact energy absorbed by specimen in Joules

A = Area of the cross section of specimen below notch before test in m2

PROCEDURE:

1. The hammer is raised and locked.

2. The pointer is set at max. position of graduated energy of dial.

3. The safety load bar is placed horizontally arms of projecting bars.

4. The trigger is released and pendulum is allowed to swing. This actuates the pointer

to move in the dial.

5. See that no person is on within range to swing of pendulum.

6. The specimen is placed vertically ie cantilever position in such a way that notch is

opposite to the direction of the pendulum for contact centering of specimen. The

end stop is provided.

7. The latches are released and pendulum is allowed to strike on specimen (or)

bending the specimen is noted in the dial.

8. Then the impact energy required for the rupture of the specimen is directly

measured on indicator.

RESULT : The Izod impact strength is calculated as,

The impact strength of the given specimen (I) = J/m2


26


Brinell hardness Testing Machine

LOADING TABLE:

S.NoBall

diameter

‘D’ in mm

Loading in ‘Kg’

( P )

Ferrous (Steel & Iron)

(30D2)

Non – Ferrous

Brass (10D2) Aluminum (5D2)

1 10 3000 1000 500

2 5 750 250 -

Exp. No: 6 BRINELL HARDNESS TESTThe Kavery Engineering college Department of Mechanical

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Date :

AIM:

To determine the brinell hardness number of the given specimen.

APPARATUS REQUIRED: Brinell Hardness Testing Machine

Brinell Microscope

Ball Indenter (5,10 mm)

Test specimens

THEORY:

Hardness represents the resistance of material surface to abrasion, scratching

and cutting, hardness after gives clear identification of strength. In all hardness

testes, a define force is mechanically applied on the test piece for about 15

seconds. The indenter, which transmits the load to the test piece, varies in size

and shape for different tastes. Common indenters are made of hardened steel or

diamond.

In Brinell hardness testing, steel balls are used as indenter.

Diameter of the indenter and the applied force depend upon the thickness of the

test specimen, because for accurate results, depth of indentation should be less than 1/8 th

of the thickness of the test pieces. According to the thickness of the test piece increase,

the diameter of the indenter and force are changed.


28


TABULATION:

S.No

Name of the

Material

Load(Kgf)

P

Diameter ofImpression

Mean dia of

Impression

(mm)

‘d’

Area‘A’

mm2

Brinell Hardnes

sNumber(BHN)

d1

(mm)

d2

(mm)

1

2

3

MODEL CALCULATION:Name of the Specimen =

Applied Load (P) = Kg

Ball diameter (D) = mm

Diameter of the impression ‘d1’ = mm

Diameter of the impression ‘d2’ = mm.

Surface Area of Impression (A) =

DD - (D2 – d2 ) ] mm2

2

Brinell Hardness Number (P/A) = _____________ Kg/mm2 Or BHN


29


PROCEDURE:

1. The type of ball indenter of specified diameter is selected and fixed in machine

head.

2. The surface of specimen is to be cleaned from dust, oil etc. before placing it on

the test platform.

3. The platform with specimen is raised until gap between indenter and specimen

is minimum. Now the machine is switched on.

4. The load-applying lever is released to original position.

5. A minor load is applied manually while the specimen is made contact with the

indenter.

6. The platform is lowered and the machine is switched off.

7. Then with the help of brinell microscope the diameter of impression is measured

and tabulated.

8. Then with the help of brinell microscope the dia of impression is measured in

two directions at right angle to each other and average dia to be taken and

tabulated.

9. The above procedure is repeated for different specimen with minimum three

readings in each specimen.

RESULT:

The Brinell hardness number of

1. ____________with _______ Ball diameter = __________ BHN




30


Rockwell hardness Testing Machine

LOAD TABLE:

Material Penetrates Load (Kgf) Scale

Relatively soft Material Diamond cone(1200 ) 60 A

Purely hard Material 1/16” Ball point 100 B

Hard Material Diamond Cone (800) 150 C


31


Exp. No: 7 ROCKWELL HARDNESS TESTDate :

AIM:

To determine the Rockwell hardness Number of given specimen.

APPARATUS REQUIRED:

1. Rockwell hardness testing machine

2. Penetrates

3. Test specimen.

THEORY: Hardness represents the resistance of material surface to abrasion, scratching and

cutting, hardness after gives clear indication of strength. In all hardness tests, a define

force is mechanically applied on the piece, varies in size and shape for different

tests. Common indenters are made of hardened steel or diamond.

Rockwell hardness tester presents direct reading of hardness number on a dial

provided with the m/c. Principally this testing is similar to Brinell hardness testing. It

differs only in diameter and material of the indenter and the applied force. Although there

are many scales having different combinations of load and size of indenter but commonly

'C' scale is used and hardness is presented as HRC. Here the indenter has a diamond

cone at the tip and applied force is of 150 kgf. Soft materials are often tested in 'B' scale

with a 1.6mm diameter steel indenter at 60kgf.


32


TABULATION:

S.NoName of

the Material

Load

(Kgf)

Load

(N)Penetrates Scale

Dial

Reading

Rockwell

Hardness

Number

1.

2.

3.

4.


33


PROCEDURE:

1. Insert ball of dia. 'D' in ball holder of the m/c.

2. Make the specimen surface clean by removing dust, dirt, oil and grease etc.

3. Make contact between the specimen surface and the ball by rotating the

jack adjusting wheel.

4. Push the required button for loading.

5. Pull the load release lever wait for minimum 15 second. The load will automatically

apply gradually.

6. Remove the specimen from support table and locate the indentation so

made.

7. Repeat the entire operation, 3-times.

RESULT:

The Rockwell hardness number of

1. ____________with _______penetrate = __________ RHN





34



35


Exp. No: 8 DEFLECTION TEST ON SIMPLY SUPPORTED BEAM (MILD STEEL)Date :

AIM:To find the values of Young’s modulus of the material of a simply supported beam

(mild steel) by conducting deflection test.

APPARATUS REQUIRED:1) Deflection of beam apparatus

2) Weight

3) Beam ( steel)

4) Deflect meter

5) Knife edge support

6) Loading hanger

7) Vernier caliper

THEORY: If a beam is simply supported at the ends and carries a point load at its centre,

the beam bends concave upwards. The distance between the original position of the beam

and its position after bending is different at different points along the length of the beam,

being maximum at the centre in this case. The difference is known is deflection.

FORMULA USED:

W a x (L2 ─a2 ─x2) Young’s Modulus E = N/mm2 6 I L

Where, bd3 I = Moment of inertia in ‘mm4’ = 12

W = Load applied in ‘N’

L = Effective span of the beam in ‘mm’

= Mean deflection of the beam in ‘mm’

x = Distance between the deflect meter and one knife edge in ‘mm’

a = Distance between the load hanger and another knife edge in ‘mm’

b = Breath of specimen in ‘mm’The Kavery Engineering college Department of Mechanical

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d = Thickness of the specimen in ‘mm’

OBSERVATIONS:Effective span of the beam ‘L’ =

Breath of specimen in ‘b’ =

Thickness of the specimen in‘d’ =

Least count deflection of the beam =

Distance between the deflect meter and one knife edge ‘x’ =

Distance between the load hanger and another knife edge in ‘a’ =

TABULATION:

S.No

Load

applied

( W)

Kg

Load

applied

( W)

N

Deflect meter

Reading

Mean

Deflection

()

mm

Young’s

Modulus

(E)

N/mm2

Loading Unloading

1

2

3

4

5

6

7

8


37


PROCEDURE: 1. Place the beam on the knife edges on the blocks so as to project equally beyond

each knife edge. See that the load is applied at the centre of the beam.

2. Note the initial reading of vernier scale

3. Add a weight of 50 N (say) and again note the reading of the vernier scale.

4. Go on taking reading adding 50 N (say) each time till you have minimum six

readings.

5. Find the deflection in each case by subtracting the initial reading of vernier scale.

Plot the graph between load and deflection. On the graph choose any two

convenient points and between these points find the corresponding values of W and

δ. Putting these values in the above relation, we can find the E.

GRAPH:

X-Axis - Deflection (mm)

Y-Axis - Load (N)

RESULT: The Young’s modulus of given mild steel material is

Theoretical (E) =

Graphical (E) =


38


COMPRESSION TEST ON HELICAL SPRING

MODEL GRAPH

OBSERVATION:

Diameter of the rod (d) = mm

Diameter of the spring (D) = mm

Inner diameter of spring (D1) = mm

Height of the spring (h) = mm

Number of turns (n) =

mmThe Kavery Engineering college Department of Mechanical

Mean radius of spring ( R) =d + D1

2 39


Exp. No : 9 COMPRESSION TEST ON HELICAL SPRING

Date :

AIM:

To study the load deflection behavior of the helical spring and to determine the

Stiffness of spring and Modulus of rigidity.

APPARATUS REQUIRED:

Spring testing machine

A spring

Micrometer

Vernier caliper

Scale

FORMULA USED:

1. Stiffness of spring ‘S’

(Slope of W- curve)= W/ N/mm

2. Modulus of rigidity

(C) =

64 WR3n N/mm2

d4

‘W’ - applied Load (N)

‘R’ - Mean radius of the spring (mm)

‘n’ - No. of turns

‘’ - Deflection of the spring ( mm )

‘d’ - diameter of the spring Wire (mm)


40


TABULATION:

Sl.

No

Applie

d Load

(Kg)

Applied

Load

(N)

Compression due to the load Modulus of

rigidity

“C”

(N/mm2)

Stiffness

“S”

(N/mm)

Loading

(mm)

Unloading

(mm)

Mean

“”

(mm)

Mean


41


PROCEDURE:

1. Measure the diameter (d) of the spring bar forming the coil at 3 locations and take

the average value as the diameter of the bar.

2. Determine the mean radius(r) of the spring, record the number of turns (n).

Determine the pitch (p) of the spring and measure the free height of spring (h).

3. The compression spring is placed centrally on the bottom plate and the upper

plate is lowered such that it just touches the upper plate .

4. The pointer on the dial is set to zero. The Load is gradually applied.

5. Note the deflections for both loading as well as Unloading. Calculate the

average of the loads for the various deflections.

6. Unlock the testing machine and fix the spring in position. Make zero adjustment in

the dial by adjusting the weight on the spring.

7. Apply the load slowly note the deflections for both loading and unloading by 20N

steps. At least 6 readings have to be noted.

RESULT:

1. Stiffness of spring (S)

i) From calculation = ________ N/mm

ii) From graph = ________ N/mm

2. Modulus of rigidity (C)

i) From calculation = ________ N/mm2

ii) From graph = ________ N/mm2


42


Exp. No : 10 TORSION TEST ON MILD STEELDate :The Kavery Engineering college Department of Mechanical

43


AIM: To conduct torsion test on mild steel specimens to find the following

Modulus of rigidity

Maximum Shear stress

APPARATUS REQUIRED:

A torsion testing machine.

Twist meter for measuring angles of twist

A steel rule and Vernier Caliper or micrometer.

THEORY:

A torsion test is quite instrumental in determining the value of modulus of rigidity of

a metallic specimen. The value of modulus of rigidity can be found out thought

observations made during the experiment by using the torsion equation

FORMULA USED:

Torsion test of square rod

4.8 Tmax

Maximum Shear stress = b3

5.5 T LModulus of rigidity C = θ b4

T = Torque applied (Nmm)

C = Modulus of rigidity (N/mm2)

θ = Angle of twist (radians)

L = Gauge length (mm)

= Shear stress (N/mm2)

b = width of the square rod (mm)

OBSERVATION:


44


Width of the square rod (b) = mm

Gauge length (L) = mm

TABULATION:

S.No

Angle of

Twist

(deg)

Tropotometer

reading

Kgf(cm)

Torque

NmmModulus of

rigidity (C)

N/mm2

1

2

3

4

5

6

7

8

9

PROCEDURE:


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1. Select the driving dogs to suit the size of the specimen and clamp it in the machine by

adjusting the length of the specimen by means of a sliding spindle.

2. Measure the diameter at about three places and take the average value.

3. Choose the appropriate range by capacity change lever

4. Set the maximum load pointer to zero.

5. Set the protector to zero for convenience and clamp it by means of knurled screw.

6. Carry out straining by rotating the hand wheel in either direction.

7. Load the machine in suitable increments.

8. Then load out to failure as to cause equal increments of strain reading.

9. Plot a torque- twist (T- θ) graph.

10. Read off co-ordinates of a convenient point from the straight line portion of the torque

twist (T- θ) graph and calculate the value of C by using relation

RESULT:

Maximum shear stress =__________N/mm2

Modulus of rigidity C (From Calculation) =__________ N/mm2

Modulus of rigidity C (From Graph) =__________ N/mm2


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Exp. No: 11 EFFECT OF HARDENING IN IMPACT RESISTANCE OF STEEL

Date :

AIM: To determine the effect of hardening in impact resistance resistance of steel before

and after hardening.

APPARATUS REQUIRED:

Impact testing machine

Furnace

Vernier caliper

Scale

PROCEDURE:

1. The hammer is raised and locked.

2. The pointer is set at maximum position of graduated energy of dial.

3. The safety load bar is placed horizontally arms of projecting bars.

4. The trigger is released and pendulum is allowed is to swing this actuates the pointer to

more in the dial.

5. The specimen is placed in such a way that notch is opposite to the direction of the

pendulum for contact centering of specimen the end stop is provided.

6. The latches are released and pendulum is allowed to strike on specimen or bending the

specimen is noted in the dial.

7. Then the input energy required for the rapture of the specimen is directly measured on

indicator.

8. Now another specimen is taken and kept into a furnace at 8500C to 9500C.

9. The specimen is the same piece is cooled suddenly in quenching media.

10. Now the variation in the input strength before and after hardening is studied.


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OBSERVATION:

Breadth of specimen (b):__________________

Depth of Specimen (d):___________________

Length of Specimen (L):___________________

Depth of notch (d1):______________________

TABULATION:

Specimen

Dimension of specimen Are of

cross

section

A (mm2)

Impact

energy

observed

K (J)

Impact

strength

I=K/A

(J/m2)

Breadth b

(mm)

Depth

d

(mm)

Length L

(mm)

Depth of

notch d1

(mm)

Before

hardening

After

hardening

MODEL CALCULATION:

Area of the cross section of specimen (A) = b (d -d1) mm2



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RESULT: The charpy impact strength is calculated as,

1. The impact strength of the given specimen (Before hardening) = ________ J/m2

2. The impact strength of the given specimen (After hardening) = __________J/m2


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Exp. No : 12 STUDY OF MICROSCOPIC EXAMINATION OF HARDENED AND TEMPERED SAMPLES

Date :

AIM: To determine the microscopic examination of hardened and tempered samples (steel)

APPARATUS REQUIRED:

Specimen

Metallurgical microscope

COMPOSITION:

C=0.6%

Si=0.4%

Mn=0.1%

P=0.05%

S=0.05%

Heat treatment: yes

Mechanical treatment:: NIL

OBSERVATION: The structure contains tempered martensite. The given structure is identified as quenched

and tempered steel.


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a

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Exp. No : 13 STUDY OF MICROSCOPIC EXAMINATION OF UNHARDENED SAMPLES

Date :

AIM: To determine the microscopic examination of unhardened samples

(medium carbon steel)

APPARATUS REQUIRED:

Specimen

Metallurgical microscope

COMPOSITION:

C=0.6%

Si=0.6%

Mn=0.8%

P=0.004%

S=0.004%

Heat treatment: NIL

Mechanical treatment: NIL

OBSERVATION: The structure contains pearlite and ferrite. The given structure is identified as medium

carbon steel.


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