s m lab final

8/12/2019 S M LAB FINAL

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SATHYABAMA UNIVERSITY

CHENNAI -600 119

DEPARTMENT OF MECHANICAL

ENGINEERING

MATERIAL TESTING LAB MANUAL


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CONTENTS

LIST OF EXPERIMENTS

1. COMPRESSION TEST ON BRICKS.CONCREATE BLOCS.2. DEFLECTION TEST3. COMPRESSION TEST ON OPEN COILED HELICAL SPRING4. TENSION TEST ON CLOSED COILED HELICAL SPRING5. DOUBLE SHEAR TEST U.T.M6. IZOD/CHARPY IMPACT TEST7. TENSION TEST ON MILD STEEL BAR8. ROCKWELL HARDNESS TEST9. BRINELL HARDNESS TEST10. VICKERS HARDNESS TEST12 LOAD MEASUREMENTS USING LOAD INDICATOR & LOAD COILS


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1. COMPRESSION TEST ON WOOD/ BRICK

AIM :

To determine the compressive strength of a given wooden specimen .

APPARATUS REQUIRED:

Compression testing machine

1. Scale .

PROCEDURE :

1. Measure the dimensions of the specimen .2. Keep the wooden specimen at the centre of the lower compression plate .Now lower the

adjustable cross head by rotating the hand wheel so that the top compression plate just

touches the specimen .3. Now apply the load manually. Now the specimen is compressed between the compression

plates .The load applied to the specimen is indicated by the measuring value indicator .

4. Load the specimen till it fails .Note the ultimate load .5. Remove the specimen from the machine .

OBSERVATION :

C . S dimensions of the specimen = mm


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TABULATION :

CALCULATION:

Ultimate compressive load (N)

Compressive strength of the given specimen( N/mm) = ---------------------------------

C. S area of the specimen (mm)

RESULT :

The compressive strength of the given specimen = (N/mm)

Sl .No Load in N Cross sectional area of

the specimen

( mm2)

Compressive strength

N / mm2


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2.DEFLECTION TEST

AIM :

To determine the Youngs modulus of the given material and verify Maxwells law of

reciprocal deflection .

APPARATUS :

1. Knife edge supports2. Deflectometer3. Set of weights with hanger.4. Scale5. Vernier caliper .

PRINCIPLE :

According to Maxwells law of reciprocal deflection in a simply supported beam

AB = BA

where AB- Deflection of the beam measured at A due to the load at B

BA- Delection of the beam measured at B due to the load at A

PROCEDURE :

1. Measure the dimensions of the beam.2.

Place the given beam on knife edge supports with equal overhangs on either side of thebeam .

3. Place the deflectometer at a distance x from the support.4. Place the weight hanger at a distance of a from the support. Note the initial reading of

the deflectometer.

5. Now increase the load gradually and take the corresponding deflectometer readings.6. Now decrease the load in the same intervals and note the deflectometer readings.7. Draw a graph - Load vs Deflection .


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OBSERVATION :

x < a & x < b

C . S . dimensions of the beam =

Span ( l ) = mm

Distance ( x ) = mm

Distance ( a ) = mm

Distance ( b ) = mm

TABULATION :

S.No Load

Deflectometer reading Youngs

modulus

in

N/mm2

x < a x < b

gm N Loading

mm

Unloading

mm

Mean

mm

Loading

mm

Unloading

mm

Mean

mm

1.2.3.4.

5.6.


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CALCULATION:

x < a

w b x

= ------------ ( l2- b2- x2 )

6 E I l

x < b

w a x

= ------------ ( l2- a2- x2)

6 E I l

RESULT :

Youngs modulus of the given material (E) = (N/mm)


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3.COMPRESSION TEST ON OPEN COILED HELICAL SPRING

AIM :

To conduct a compression test on the given helical spring and hence determine the

following, a) Shear modulus b) Stiffness of the spring c) Proof load d) Strain energy stored

at proof load

APPARATUS :

1. Spring testing machine2. Vernier caliper3. Scale

MACHINE DESCRIPTION :

The machine mainly consists of loading mechanism, load measuring system, indicating

mechanism, recorder and electrical controls.

Loading mechanism:

The base is connected to torque plate by two columns forming the main structure of the

machine .The measuring system is assembled on top plate and is covered by top cover. The side

panel fixed to the right column consists of indicating and recording mechanismsLoad measuring sytems(Pendulum dynamometer):

The load measuring system is supported on the top plate and is covered by the top cover.

The upper grip head is fixed to the central member .A spring steel strip with one end fixed to the

pendulum shaft runs around the shaft and its end is fixed to the central member.


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Indicating mechanism:

The rack pusher fixed to the pendulum lower pushes the rack which slides over the rack

guide pulleys .The lower movement of the rack rotates the pinion .The pinion is fixed on a pointer

shaft running in ball bearing. A dummy pointer which moves forward with the main pointer is

provided for maximum load reading .

PROCEDURE :

1. Measure the mean coil diameter and the diameter of wire of the spring .Also note thenumber of free coils in the spring.

2. Place the spring in position in between the platforms for compression spring.3. Adjust the indicator of the load dial, to read 0.4. Apply compressive load by increasing at suitable intervals and note the corresponding

deflections.

5. Draw graph - load vs deflection .

OBSERVATION :

Mean coil diameter ( D ) = (N/mm)

Wire diameter (d ) = (N/mm)

No. of turns ( n ) =

Free height of the spring (H) = (N/mm)


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TABULATION :

S.No

Load

(N )

Deflection (mm ) Stiffness

(N/mm)

Proo

f

Load

( N)

Shear

stress

(N/mm)

Rigidity

modulus

(N/mm)

Strain

energy

(N-mm)Loading Unloading Mean

1.2.3.4.5.6.7.8.9.10.

CALCULATION:

64 R3n w

Rigidity modulus ( G ) = ------------- x --------------- (N/mm)

d4


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w

Stiffness of the spring ( K ) = ----------- (N/mm)

Proof load (wp) = K (H - n d ) (N)

16 wp R

Shear stress (p ) = -------------- = (N/mm)

d3

(p )2 d2

Strain energy stored ( Uwp ) = -------------- x --------- x Dn (N/mm)

4 G 4

RESULT :

Rigidity modulus = (N/mm)

Stiffness of the spring = (N/mm)

Proof load = (N)

Strain energy stored at proof load = (N/mm)


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4. TENSION TEST ON CLOSED COILED HELICAL SPRING

AIM :

To conduct a tension test on the given helical spring and hence determine the

following a) Shear modulus b) Stiffness of the spring.

APPARATUS :

1. Spring testing machine

2. Vernier caliper

3. Scale

MACHINE DESCRIPTION :

The machine mainly consists of loading mechanism, load measuring system, indicating

mechanism, recorder and electrical controls.

Loading mechanism:

The base is connected to torque plate by two columns forming the main structure of the

machine. The measuring system is assembled on top plate and is covered by top cover. The side

panel fixed to the right column consists of indicating and recording mechanisms

Load measuring systems(Pendulum dynamometer ):

The load measuring system is supported on the top plate and is covered by the top

cover.The upper grip head is fixed to the central member .A spring steel strip with one end fixed

to the pendulum shaft runs around the shaft and its end is fixed to the central member.


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Indicating mechanism :

The rack pusher fixed to the pendulum lower pushes the rack which slides over the rack

guide pulleys .The lower movement of the rack rotates the pinion .The pinion is fixed on a pointershaft running in ball bearing. A dummy pointer which moves forward with the main pointer is

provided for maximum load reading .

PROCEDURE :

1. Measure the mean coil diameter and the diameter of wire of the spring .Also note thenumber of free coils in the spring .

2. Place the spring in position by attaching it to hooks for tension spring .3. Adjust the indicator of the load dial ,to read 0 .4. Apply tensile load by increasing at suitable intervals and note the corresponding

deflections .

5. Draw graph - load vs deflection.

OBSERVATION :

Mean coil diameter (D) = mm

Wire diameter (d ) = mm

No. of free coils ( n ) =


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TABULATION :

S.No

Load

(N )

Deflection (mm ) Stiffness

N/mm

Shear

stress

N/mm2

Rigidity

modulus

N/mm2

Strain

energy

N-mmLoading Unloading Mean

1.2.3.4.5.6.7.8.9.10.

CALCULATION:

64 R3n w

Rigidity modulus ( G ) = -------------- x ---------


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d4

w

Stiffness of the spring ( K ) = ---------------

16 wR

Shear stress ( ) = ------------

d3

( )2 d2

Strain energy stored ( Uwp ) = -------------- x --------- x Dn

4 G 4

RESULT :

Rigidity modulus (N/mm) =

Stiffness of the spring (N/mm) =

Proof load (N) =

Strain energy stored at proof load =


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5 DOUBLE SHEAR TEST U.T.M

AIM

To determine the shear strength (ultimate shear stress) of the mild steel specimen supplied using

double shear method.

EQUIPMENT

UTM, Shear attachment to the UTM, shear dies and Venire Calipers.

THEORY AND PRINCIPLE

Shear strength of the material is the ultimate shear stress ( ) attained by the specimen,

which under double shear given by,

Where,

F = Maximum load at which the specimen breaks, and

A = cross-sectional area of the specimen.

The load range to which the machine is to be set for the test is selected bases on the expected

maximum load F to be applied on the specimen. This is calculated from the yield stress fy and the

factor of safety , as follows:

Permissible shear stress t for mild steel is,

And therefore,


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________________________(2)

PROCEDURE

Measure the diameter of the specimen. Calculate the maximum load expected to be applied on

the specimen using equation (2) and select the load range to be used. Set the UTM for the

selected load range. Set the correct set or dies to assemble the shear attachment with the right

set of dies in it. Insert the specimen in to the dies so that it projects equally on either side. Place

the entire bear assembly with the specimen in it centrally over the baring plate on the lower

table. Bring the lower cross- head close to the top surface of the assembly. Float the lower table

and set the load pointer to zero. Apply the load gradually until the specimen breaks. Note the

ultimate load applied on the specimen.

OBSERVATION

The observation taken are tabulated in Table

Calculations

(i) Range

Using equation (2) and taking fy = 250 N/mm2 and =3 and, expected maximum load to be applied

on the specimen is,

F = 30.45250/2A

(ii) Shear strength

Using equation (1) the ultimate shear stress is= F/2=___________

RESULT

Ultimate shear stress of the material is fount to be N/mn^2


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6. IZOD IMPACT TEST

AIM :

To determine the impact strength of the given specimen.

APPARATUS REQUIRED:

1. Izod impact testing machine

2. Scale

.

MACHINE DESCRIPTION:

The pendulum impact testing machine consists of the single piece frame, the pendulum,

the specimen support and the measuring equipment. The pendulum is fastened to the pendulum

shaft. The range within which the pendulum is swinging is partially protected by the guard. There

is a dial attached concentrically with the pendulum shaft. The scale is designed such that the

impact energy absorbed in breaking the specimen can be read directly.

(i) Angle of drop of pendulum = 900

(ii) Striking velocity of pendulum = m / sec

PROCEDURE :

1. Firmly secure the proper striker to the bottom of the hammer with the help of dampingpiece.

2. Firmly secure the latching tube for Izod test to the barring housing at the side of thecolumns. The steel wire coming from the latch is carried through the latching tube and is

fastened to the interior of the release lever.

3. For determining the frictional loss in the machine, adjust the reading pointer along withpointer carrier to 300 J reading on the dial when the pendulum is swinging free.

4. Note the reading on the scale against the pointer, which gives initial error if any.5. Now lift the pendulum again to its starting position.6. Fix the specimen for Izod test to the support.7. Release the pendulum as before. The hammer strikes the specimen.8. Note the reading against the pointer. This gives the energy absorbed by the specimen.

OBSERVATION:


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Length of the specimen = mm

Effective cross-sectional area = mm

Energy absorbed by the specimen = J

TABULATION:

Sl .No Effective cross-sectional

area ( mm2)

Energy absorbed by the

specimen ( J )

Impact strength

(J / mm2)

CALCULATION:

Energy absorbed by the specimen

Impact strength = -------------------------------------------------------------- J/mm

Effective cross-sectional area

RESULT:

Impact strength of the given specimen = J/mm


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7. TENSION TEST ON MILD STEEL BAR

AIM:

To study the behaviour of a mild steel specimen under tension when tested to destructionand also to determine the following.

i) Youngs modulus ii) Yield stress iii) Ultimate stress iv) Breaking stress

v) Percentage elongation in length vi) Percentage reduction in area.

APPARATUS REQUIRED :

1. Universal testing machine

2. Extensometer

3. Vernier caliper

4. Scale

DESCRIPTION OF MACHINE:

The machine consists of two units namely

1. The loading unit

2. The control unit.

The loading unit consists of a robust base. The main hydraulic cylinder is to be fitted in the

centre of the base and the piston slides in the cylinder. It consists of a lower table, which is

connected to the main piston through a ball and ball seal joint and two cross heads. The lower

table and the upper cross head assembly moves up and down with the main piston .

The main units in the control panel are

1.

The oil tank which contains the hydraulic oil.2. The pump which assures a continuous high pressure non - pulsating of current for the

smooth application of load on the specimen.

3. Two valves one at the right hand side and the other at the left side are used to control theoil flow in the hydraulic system and Dynamometer is a unit which measures and indicates

the load. It is a pendulum dynamometer consisting of a cylinder in which the piston

reciprocates.


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4. The displacement of the piston causes the pendulum to deflect and this deflectionrepresents the measurement of the load on the specimen.

THEORY:

Within the elastic limit for ductile materials, stress bears a constant ratio with the applied

stress. When the test sample is tested by varying the stress in UTM at the time of yield, the point

steps for a moment. This will be followed by the scaling off from the surface of the specimen.

Further increase in load will be the ultimate load and this will be shown by the dummy indicator

on the load scale and the breaking load will be shown by the active indicator needle when the

specimen fails.

PROCEDURE :

Initial adjustment:Before the testing, adjust the pendulum weight according to

the capacity of the test. Adjust the corresponding range on the dial with the range - adjusting

knob.

1. Measure the diameter of the specimen in two directions perpendicular to each otheratleast at three places on the bar and take the average .

2. Mark the gauge length on the bar.3. Select the appropriate measuring range by placing proper weights on the Pendulum of the

U . T . M.

4. Fix one end of the mild steel bar in the clamping jaws of the U. T. M5. Now adjust the lower head to the required distance and grip the other end of the mild

steel bar in the clamping jaws in it.

6. Clamp the extensometer.7. Apply the load gradually by opening the right control valve and note the corresponding

extensometer reading.

8. At a particular stage there will be a pause in the increase of load. The load at that point isnoted as yield point load.

9. After the pointer reaches the maximum, there will be a sudden drop in the load and thisis recorded as ultimate load.

10.A neck is formed at the center of the specimen and continue the loading with a dummypointer accompanying the load pointer until the mild steel bar breaks. Note the breakingload at the time of fracture.

1. Now close the right control valve. Remove the specimen from the machine.2. Measure the final length and the diameter of the mild steel bar.3. Calculate the stress and strain for each reading and plot a graph. Slope of the line gives

the Modulus of Elasticity.


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OBSERVATION:

Diameter of the specimen (D) = mm

Gauge length of the specimen (L) = mm

Neck diameter after fracture(D1) = mm

Final gauge length after fracture (L1) = mm

Yield load N

Ultimate load = N

Breaking load N

TABULATION :

Sl. No Load Extensometer reading

mm

Strain Stress

N/mm2

Youngs

Modulus

N/mm2Kgf N Dial I Dial II Mean

1.2.3.4.5.6.7.


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CALCULATION:

Initial cross-sectional area (A) = mm

Final cross-sectional area (A1) = mm

% reduction in area = Initial area - Final area

--------------------------------- X 100 %

Initial area

Final length - Initial length

% Elongation in length = -------------------------------- X 100 %

Initial length

Yield load

Yield stress = -------------------------

Initial cross-sectional area

Ultimate load

Ultimate stress = --------------------------- N/mm

Initial cross-sectional area


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8. ROCKWELL HARDNESS TEST

AIM :

To find the Rockwell hardness number for the given materials.

GENERAL:

The Rockwell hardness test is of the static indentation type and the Rockwell hardness

number is based on the additional depth to which a penetrator is driven by a heavy load beyond

the depth to which a penetrator has been driven by a definite light load .The following indentors

are used in Rockwell hardness tester .

a ) Diamond cone indentor with a top angle of 1200

.

b ) Steel ball of diameter 1/ 16 .

Load range : 60 , 100 , 150 kg.

APPARATUS REQUIRED:

1. Rockwell hardness testing machine

2. Stop watch

PROCEDURE :

1. Put the weights on plunger of dash-pot according to the Rockwell scale required byturning the Load selector disc, the respective figure of weight will be visible in the

window.

2. Keep the lever at position A.3. Place the specimen securely on the work table .4. Turn the hand wheel clockwise so that the specimen will push the indentor and show a

reading on dial gauge as small pointer at 3. The long pointer automatically stops at 0

on black scale. (i.e ) B 30 on red scale .5. Turn the lever from position A to B slowly so that the total load is brought into action

without any jerks.

6. When the long pointer of dial gauge reaches a steady position, take back the lever to Aposition slowly.

7. Read off the figure against the long pointer. This gives the Rockwell hardness number8. Turn back the hand wheel and remove the specimen from the machine. Carry on the

same procedure for further specimens.


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TABULATION :

Sl . No Specimen Loadkg f

Indentor Scale Rockwell hardness number

Trial 1 Trial 2 Trial 3 Mean

RESULT :

The Rockwell hardness number for


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9. BRINELL HARDNESS TEST

AIM :

To determine the Brinell hardness number for the given specimens.

APPARATUS :

1. Brinell hardness testing machine.

2. Microscope.

DESCRIPTION OF MACHINE :

The machine consists of a J frame, main lever, hanger, elevating screw, loading

unloading mechanism and damper system. The load is applied on the specimen through ball

holder, it is effected through a lever mechanism.

The main lever carries three male vees, one for hanger, second for spindle shaft and third

for pivot vee. The elevating screw can be moved up and down by rotating the hand wheel. The

five detachable weights, each equivalent to 500 kg and to be made use of for application of

desired load in addition to the bottom weight equivalent to 500 kg. The operating lever is

provided for loading and unloading.

PROCEDURE :

1. Polish the surface of the specimen.2. Place the specimen on the worktable.3. Keep the operating lever in horizontal position.4. Turn the hand -wheel in clockwise direction so that the specimen touches the ball

indentor.

5. Lift the operating lever from horizontal position upwards slightly after which it rotatesautomatically.

6. Wait till the lever becomes standstill.7. Bring the lever back to horizontal position.8. Turn back the hand wheel and remove the specimen from the machine. Carry on thesame procedure for further specimens.9. Measure the diameter of impression by Brinell Microscope.10.Find the Brinell hardness number using the formula

FORMULA:


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P

Brinell Hardness Number = --------------------------------

D / 2 [ D - (D2- d2) ]

Where P - load in Kgf

D - Dia. of indenter in mm

d - Dia. of indentation in mm

For Steel , P = 30 D2

For Brass , P = 10 D2

For Aluminium, P = 5 D2

OBSERVATIONS:

Diameter of indentor , D =

Diameter of indentation, d =


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TABULATION :

Sl . No Specimen Diameter of

indentor D

(mm)

Load

kgf

Diameter of impression

(mm)

Brinell

hardness

numberTrial

1

Trial

2

Trial

3

Mean

RESULT : Brinell hardness number for the given specimens =


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11.LOAD MEASUREMENTS USING LOAD INDICATOR & LOAD COILSAim:

To study the load measurements using load indicator & load coils.

Apparatus Required:

Proving ring with strain gauge boarded digital force indicator & necessary

weights.

Procedure:

1. Dial Gauge will show o (Zero) when there is no load in the plan.2. Apply the Load in the pan, note down the deflection shown at the dial gauge.3. 1kg =10 kg (beam length is 1 mtr)4. Max .Load to be applied is 25 kg =250 kg

Tabulation:

SLNO Weight in (kgs) Indicator

Reading (kgf)

Force: Mass x

Acceleration .

Deflection in

(mm)

01

02

0304

05

06

07

Graph :

1.Mass Vs indicator reading .

2. Mass Vs deflection in micros.

3. Indicator reading Vs deflection in (mm)

Result:

The load measurements using load indicator & load coils is studied.


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