Stm Complete Experiments

8/4/2019 Stm Complete Experiments

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DEPARTMENT OF MECHANICAL ENGINEERING

B.E. III SEM

MATERIAL TESTING LAB

1. To determine the Rockwell Hardness of given materials.

2. To determine the hardness by Vicker Hardness Testing machine.3. To determine the Brinell Hardness Number of given materials.

4. To determine impact strength of material by impact testing machine using

Izod Test.

5. To determine impact strength of material by impact testing machine using

Chary Test.

6. To study of Universal Testing Machine.

7. To perform Tensile Test of mild steel and to draw stress-strain curve.8. To determined the Compressive Test strength of wood (1) along the

grains, (2) across the grains.

9. To determine Shear Test strength of given mild steel specimen.


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EXPERIMENT NO. .

SHEAR TESTOBJECT : To determine Shear strength of given mild steel specimen. Using UTM.

THEORY : A type of force which causes or tends to cause two continues 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 fracturein the plane of cross-section, acted on by shear force is called shear

strength.

For determining shear strength, a suitable length of steel

specimen in uniform cross-section is subjected to double shear, using a

suitable test-rig as shown in figure in universal testing machine under a

compressive test. The shear strength shall be calculated from the formula

F = ---------------- =

2. ----- d24

where F is the shear force and d is the diameter of specimen.

For metals, cross shearing tests are usually made in rivets other

bars of circular cross-section. Shearing tests have not been specified to any

appreciable extent for acceptance purpose and they are rarely used.

Shear Test


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PROCEDURE:(1) Prepare the specimen as per standards.

(2) Measure the diameter of the test specimen by means of micrometer at

each of the section to be sheared.

(3) Insert the specimen in the shear-rig properly.

(4) Fix the shear-rig in between the fixed head and movable head of theuniversal testing machine.

(5) Start the machine load at slowest speed to the ultimate which is indicated

by an abrupt reduction in load. Record this reading and stop the machine

as soon as the specimen fractures.

OBSERVATION:

Diameter of test specimen, ---------- d = -------mm

Area of the cross-section, -------d2 = ------mm2

4

Ultimate shearing load, --------F = -------N

CALCULATION:

The shear stress will be given by the formula

F = ------------------ =

2. ----- d2

4RESULT:

Shear strength of mild steel specimen = --------- N/mm2


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EXPERIMENT NO.

STUDY OF UNIVERSAL TESTING MACHINE

DESCRIPTION : Some types of testing machine are used to evaluates properties of

materials. The primary tests in tension, compression, flexure and

hardness performed on so called universal testing machine.The universal testing machines are of many types, all of them consisting

essentially of two parts (1) the straining mechanism (2) the load weighing

mechanism. With suitable arrangements of gripping of bearing device, the

specimen to be tested is interposed between fixed head and movable head.

The measurement or weighing of the load on the specimen is accomplished by

means of lever system, by pressure cells or by other devices through which the

straining load or some known portion of it must pass.

The movable head of the universal testing machine actuated

either by a gear and screw system or by hydraulically. The load is weighed

either by levers and a scale beam on which is mounted a movable pointer or by

an hydraulic gauge.

STUDY OF MACHINE:

Study the machine assigned giving special attention to each of

the following features.

(1) Capacity, make type and other main features of machine.

(2) Starting, stopping, reversing and speed controls.

(3) Straining mechanism.

(4) Provision for taking care of eccentric positioning of specimen in the

machine.

(5) Provision for adjusting the plane of the head to parallelism with the plane of

the specimen in compression test.

(6) Provision for gripping tensile specimens.

(7) Weighing or load-measuring arrangement.

(8) Various attachment and fixtures used for different type of specimens and

for different tests.

DETERMINATIONS TO BE MADE AND RECORDED :

(1) Types of tests for which machine may be used.

(2) Maximum size of specimen of each type which the machine can

accommodate.


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REPORT ;

(1) Tabulate the main characteristics of machine.

(2) Draw a line diagram showing loading arrangement and load measuring

arrangement.

(3) Draw line sketch of fixing arrangement of specimen in different tests.


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EXPERIMENT No. ..

THE ROCKWELL HARDNESS TESTING MACHINE

OBJECT : To determine the Rockwell hardness of given materials.

THEORY : This test utilize the depth of indentation under standard loading condition, as

a measure of hardness. The scale of the dial is reversed so that deepimpressions give low reading and shallow impression a high to that high

number; high number indicates hard material.

PROCEDURE :

(1) Keep lever (eccentric knob stud) at unload position A.

(2) Select the suitable indenter according to scale.

(3) Select weight according to the scale.

(4) Place the test block on testing table as per requirement.

(5) Turn the main screw nut clockwise direction to raise the test block making

contact with the clamping cone.

(6) Continue turning, first the block will get clamped, turn the main screw nut,

so that test block push the indenter further turn the main screw nut until the

long pointer of the dial gauge has made two and half turn turns than it stop

at 0 on black scale and 30 on red scale.

(7) Turn the lever from unload position A to load position at B so that total

load is brought into action.

(8) When the long pointer of the dial gauge reaches the steady position the

take by the lever to unload position A slowly.

(9) Read the figure against the long pointer on proper scale. That is the direct

reading of hardness of test block.

(10) Then turn anticlockwise the main screw nut to release the specimen and

select next surface of test block and carry on the same procedure until dial

gauge give reading marked on test block than release the test block and

the machine is ready for the next test of the job.

NOTE :

(1) Loading lever should be pulled towards A.

(2) Place the specimen below the indenter rotate the main screw nut clockwise

direction till the big hand of the dial gauge rests at 0 while small at 3 red

spot.

(3) Gently the turn lever towards B wait till the dial show the steady reading

push the lever towards A position, note down the reading.

(4) Rotate screw nut anticlockwise to release the job..


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(5) Take two or three reading initially to get set ready the indenter sits on the

holder

OBSERVATION:

RESULT:

(1) Average Rockwell hardness number of mild steel test specimen is found to

be ---

(2) Average Rockwell hardness number of Brass test specimen if found to be

--------

PRECAUTIONS:

(1) The place where the hardness tester is installed should be away from themachine, which causes vibrations.

(2) The temperature of the room should be maintained at 200 C, if possible.

(3) The surface of the test specimen should be free from oil, grease before

testing.

(4) Several reading should be taken on a dummy specimen when the machine

is newly installed. This will stabilize the apparatus.

(5) Do not test the surface, which are not leveled.

(6) Maintain correct oil level in the dashpot replace oil whenever it needed.

(7) Adjust the time of operation of the dashpot to six second in beginning.

(8) The machine should be maintained free from dust and dirt.

Sr.NO.

Material

of TestSpecimen

Penetrator

Total

Load(N)

ScaleSymbol

Rockwell

HardnessNumber

MeanValue

1.1.2.3.

2.1.2.3.

3.1.2.3.

4.1.2.

3.


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EXPERIMENT No. .

TENSILE TEST

OBJECT: - To perform tensile test of mild steel and to draw stress-strain curve.

THEORY: - Tensile test are employed to obtain the tensile strength, elasticity and ductility of the

material. This test consists in straining a test piece by tensile stress, generally to fracture.

Deformation or elongations of specimen at different loads are noted and a stress-straindiagram is prepared with the help of this diagram various elastic and strength properties

of material are found.

The standard from of tensile test specimen various with the nature of the

material. Acceptance tests of ductile metals are usually performed on a length of the

material if it is in the form of a rod and of a strip if it is a sheet material. Brittle materials

are usually formed into special shapes to permit the use of gripping device which

minimizes bending and to make certain that fracture occurs within the gauge length

selected.

The length of test piece between the grips of the testing machine should not be

less then 9 d in case of bars of dia. less the 2.5 cm, 4.5 d in case of bars of dia more then

2.5 cm. The gauge length of specimen should be taken equal to 5.65 S0, where S0 it the

original cross sectional area of the specimen.

d

L 0L0 + 2d

PROCEDURE:-

(1) Prepare the specimen as explained above.

(2) Measure the diameter of test specimen by means of a micrometer at least at three

places and determine the mean value. Also mark the gauge length with the help of acentre punch.

(3) Insert suitable jaws in the grips.

(4) Insert the test specimen in the grips.

(5) Take the initial reading on vernier scale provided in the machine.

(6) Note the initial zero error in the dial of machine.

(7) Start the machine. Apply the load at the slowest speed.


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(8) Take the reading on vernier scale at the various load stages and record.

(9) Continue applying the load till the specimen breaks and then stop the machine.

(10) Take out the fractured specimen from the grips. Measure the final length in between

the punch marks.

(11) Record the probable yield point during test by observing the point at which pointer of

load dial is stationary for some time and move backward slightly.

OBSERVATION :-

Initial diameter specimen, d0 --------------------- = mm

Diameter of test specimen after fracture, du ----------------- = mm

Gauge length, L0 --------------------- = mm

Final length after facture, Lu --------------------- = mm

Initial area of cross section, A0 = /4d20 --------------------- = mm2

Final area of cross section Au = /4d2u --------------------------------= mm2

Probable yield point --------------------- = N/mm2

Type of fracture --------------------- =

TENSILE TEST

CALCULATIONS:-P

Stress = --------- N/mm2 Strain = --------A0 l0

Sr.No.

LoadP

VernierReading

Elong-ation Stress Strain

Sr.No.

LoadP

VernierReading

Elonga-tion Stress Strain

15

26

37

48


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Draw the graph taking stress on Y axis and strain on X axis.

Ultimate loadUltimate stress = ------------------- N/mm2

A0

Lu Lo% elongation = -------------- X 100 =

L0

Au A0% reduction in area = -------------- X 100 =

A0

For calculation of value of modulus of elasticity take any two points on stress-strain curve withinelastic range. Find the corresponding stress and strain i.e. and .

2E = ------- = ------ = ------, ------- = -------- = --------, Mean value of E = ------ kgf/sq. cm. 2RESULT:

Ultimate stress = ------------------------- N/mm2

Yield stress = ------------------------- N/mm2

Proportional limit = ----------------------

Modulus of elasticity = -------------------------- N/mm2

Percentage of elongation = -------------

Percentage reduction in area = ------------

DISCUSSION:

(1)Discuss the shapes of stress-strain diagram.(2)Discuss the type of fracture obtained.

(3)Compare the results with standard values.

(4)Discuss the effect of various variables on the test results.


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EXPERIMENT No. ..

VICKER HARDNESS TESTING MACHINE

OBJECT : To determine the hardness by Vicker Hardness Testing machine.

THEORY : The vicker pyramid hardness test utilizes quadrilateral diamond pyramid an

angle of 1360 between the opposite faces, so that it is useable over the wholerange of material hardness, since the diamond is the hardest known

substance. Moreover the adoption of the square base pyramid shape provides

freedom from distortion under load.

In the case of ball indention the total impression is obtained

when the diameter of impression is 0.375 times the ball diameter. If pyramidal

tangent planes are taken of the ball, the pyramidal angle would be 1360. In the

Vickers method the indention made are all pyramids of similar angle, and the

Vickers hardness HV is obtained as follow.

Applied loadVicker Hardness HV = Area of indation

= F/(d2/sin136/2)

= 1.854 F/d2

The thickness of the test specimen should be at least 1.2d the distance

of the center of indention from edge of the test piece and between centers of

indention should be at 2.5d. the load should be applied for a period of 10 to 15

seconds. The accuracy of the microscope should be 0.001mm.

The indenter profile should be occasionally checked, and the maximum

variation at the center should not exceed 0.002mm as shown.

F

INDENTERTEST

Specimen

Platform

Principal of Vickers hardness machine

Diagonal

d1

d2

Measurement of indention


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D1 + D2

---------------2

CHOICE OF LOAD FOR VARIOUS HARDNESS RANGE

The machine carrying out Vickers hardness tests against load50, 30, 20, 10, & 5. These load are selected as per requirement. An optical

device is provided for projecting the impression on front screen with 70 times

magnification, which is capable to project 1.6 mm impression maximum. The

micrometer thimble provided on front screen enable to measure diagonal of

impression. It is advisable to select the load in relation to expected hardness

range of the metal in such a way that impression produced should be to 0.50 mm

across diagonal as for as possible.

PROCEDURE:For carrying out tests, the following procedure should be adapted very

carefully. Any negligence may lead to spoil the indenter.

(1) Select the weights according to the expected hardness of specimen to be

tested.

(2) Place the specimen securely on testing table.

(3) Turn the hand wheel clockwise so that specimen will get focused on front

screen shapely. At this sage a gap of above 0.2 to 0.25 mm expected

between tip of diamond indenter and top face of specimen.

(4) Press start push button. Keep it pressed till inside START button will be ONeven after release of push button. The loading cycle starts gradually.

The cycle is as under

Load is transferred on specimen gradually maximum time about 6

second.

The load is kept constant on specimen as per dwell time adjustment.

Adjustment range is 30 2 sec.

(5) The indention is now projected on front focusing screen. Measure diagonal of

impression is both the axis one after other. Find out mean value. Refer

corresponding table and find out vicker hardness value.(6) To have next test, index the head to original position and bring back indenter

on specimen, before starting loading / unloading. Vicker hardness value is

always mentioned with the reference to load applied.

HV 30 = 610 30 denots applied load in kgf.


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PRECAUTIONS:

(1) The machine should be maintained free from dust and dirt.

(2) The moving parts of machine like loading mechanism are locked so that this

should not move in transit.

(3) It should free from outside vibration.


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EXPERIMENT NO.

IMPACT TEST

OBJECT : To determine impact strength of material by impact testing machine using

Charpy Test.

THEORY : To determine the notch beam impact strength of steel, three types of notches

are used (a) V-notch (b) U-notch (c) key hole notch. The test piece should bemachined all over and 55 mm long square cross section with 10 mm sides.

Three notches is made at the centre of the piece. The notches should be

prepared carefully by any machining method like milling shaping but no grooves

should be visible to the necked eye. The test piece should lie squarely against

the supports the supports with the plane of symmetry of the notch within 0.5 mm

of the plane midway between them shown in fig. It should be struck by the

hammer in the plane of symmetry of the notch and on the side opposite to the

notch the speed of striking should be 5m/s to 5.5m/s.

PROCEDURE :1. Lift the hammer to an appropriate knife-edge position and note down the

energy stored in the hammer. For the standard test the energy stored should

be 300 N-m.

2. Fit the striker with the central vertical edge in striking position.

3. Release the hammer. The hammer will break the test piece and shut up to

the other side of the machine.

4. Note the residual energy indicated on the scale by the hammer.

5. The impact strength of the test piece is the difference of the initial energy

stored in the hammer and the residual energy.

40mm

Striking Edge

10 X 10 X 55mm

V Notch Specimen Charpy Test


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6. Calculate the impact modulus given by the ratio of the apparent energy of the

rapture of the volume of the test piece below the notch.

OBSERVATION:

The experimental data may be tabulated as following.

Material of the test piece = -----------

Type of notch = -----------

Dimension of the test piece = -----------

Velocity of striking = -----------

Test No Initial energy ( N-m) Residual energy (N-m) Energy absorbed (N-m)

1

2

3

4

5

Means value of impact strength = ----------

CALCULATION:

Impact strength (N/m2) I = K/AK = energy stored by the specimen in joules

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

PRECAUTION:

1. The machine should be installed in such a way that the swinging range of the

pendulum does, by no means, project into the area of common use.

2. The working place is to be safe-guarded against hitting by stray pieces of broken test

specimen.

3. Before any test, ensure the fixing of correctly end supports.

4. Confirm the tightness of all bolts and striker, latching tube, specimen supports etc.

5. Do not allow to stand near the machine and particularly in the range of pendulum

swinging.


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EXPERIMENT No.

BRINELL HARDNESS TEST

Object : To determine the Brinell hardness number of given materials.

Apparatus : Brinell hardness tester machine, dynamometer, ball holder, specimen.

Theory : The brinell hardness test consists of the application to the surface of the

specimen under test, of a hard steel ball of known diameter load for specifiedminimum time period. The diameter of the resulting impression is measured by

means of microscope and the Brinell hardness number is the load applied in N

divided by the spherical area of impression (in mm2). If P is the applied load in

N. D is the diameter of the steel ball (mm) and d is the diameter of the

indention in (mm), then

BHN = Load / indented area

P/{ D/2( D-D2-d2)}N/mm2

In order that d/D may be within reasonable limits (preferable between 0.2 and

0.5) for different materials, standard ratio of P/D2 are used.

00

d = 2.1 mm

Procedure :

(1) Keep, clean flat and smooth surfaced specimen for the test.

(2) Keep the specimen on the top plate, as shown in the drawing and apply

the desire load in Kg. On the specimen by rotating the handle in the

clockwise direction, so that the sample comes in contact with the

ball fitted in the ball holder.

(3) For applying the desired load, which in normally 3000 Kg, is achieved by

deferring to the calibration chart.

(4) The large needle of the gauge should be always in 12 O clock position

(0) before application of the load.


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(5) Hold desire load for 30 seconds and thereafter, release the load by

rotating the handle in anticlockwise direction and switching of the motor

in motorized version.

(6) Remove the specimen from the top plate and see the diameter of the bal

impression with the help of brinell microscope and than refer to the

enclosed hardness conversion table for the knowing hardness value of

the material under test.

Observation and results :

Material of test specimen = -----------

Diameter of steel ball D = -----------mm

Diameter of indentation d = -----------mm

Applied load = -----------N

B.H.N.=Load/Indented area

B.H.N. = P/{ D/2( D-D2-d2)}N/mm2

Precautions :

(1) The thickness of the test specimen should not be less than ten times the

depth of the impression.

(2) Distance of the center of indention from the edge of the specimen or from the

center adjacent indentions should be greater than three times diameter of the

indention.

(3) The surface on which impression is made, should be flat, the accuracy of the

measurement of the impression will depend on the degree of finish imparted

to the surface, which should preferably be polished.

(4) Slow speed of load application should be used for high precision. The speed

of application of the load is adjustable by means of the knob at the front of

machine. Turn the knob to the left to increase and to the right to decrease thespeed.


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EXPERIMENT NO.

COMPRESSION TEST

OBJECT : To determined the compressive test strength of wood

(1) along the grains, (2) across the grains.

THEORY : wood exhibits, under compressive loading, a behavior peculiar to it self it is

anything but an isotropic material, being composed of cells formed by organicgrowth align themselves to from a series of tubes or columns in the direction of

the grain. As a result of this structure the elastic limit is reality low. There is no

definite yield point and considerable set take place before failure. For loads

normal to the grains, the load that causes lateral collapse of the tubes or fibres

(crushing) is the significant load. For loads parallel to the grain, not only the

elastic strength important but also the strength at rupture. Rupture often occurs

because of collapse of the tubular fibres as columns. Various types of failure of

would loaded parallel with the grain are shown in figure. 1.

(a) Crushing (plane of rapture approx. horizontal)

(b) Wedge split

(c) Shearing (plane of rapture at acute angle with horizontal)

(d) Spliting

(e) Shearing and splitting parallel to grain.

TEST SPECIMENS :

Specimen for compression tests of wood parallel to the grain 5cm X 5cm X

20cm rectangular prisms. Compression tests perpendicular to the grain are

made on nominal 5cm X 5cm X 15cm. specimens. The load in applied through

a metal bearing plate 5cm. with placed across the surface at right angles to the

width placed across the upper surface at right angles to the width as shown in

figure. 2.

PROCEDURE :


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(1) Measure the dimensions of test places.

(2) Clean the bottom and top platens of the machine.

(3) Position the specimen

centrally on the bottom platen and screw down the top platen into contact.

Positioning of the specimen centrally is important to ensure correct

application of the load (fig. 3)

(4) Open the stop valve of thepressure gauge to be used. Close other pressure gauge valves.

(5) Open the control valve fully and start the pump motor.

(6) Set the loose pointer of the

gauge to zero and apply load slowly by closing the control valve.

(7) When the specimen falls,

the loose pointer on the gauge will indicate the maximum load reached. At

this point the pump motor should be stopped.

OBSERVATION AND CALCULATIONS:

TestDimensions of

specimenCross section

area m2Load at failure

NCompressivestrength N/m2

Along the grain

Across the grain

Results:-

(1) The compressive strength

of wood specimen along the grain is ---------------

(2) The compressive strength

of wood specimen across the grain is ---------------

Precautions:-

(1) The specimen should be correctly prepared. It should be ensured that the

end faces are at right angles to the side faces.

(2) Specimen should be correctly placed on the bottom platen of the machine.

(3) Load should be centrally placed on the bottom platen of the machine.

(4) The specimen guard should be positioned to protect the operator from flying

fragments if any.

Discussion : Discuss the type of failure for each case.


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EXPERIMENT NO.

IMPACT TEST

OBJECT : To determine impact strength of material by impact testing machine using

Izod Test.

THEORY : Many structures, machine and machine parts are commonly subjected to

suddenly applied loads. Impact resistance is the capacity of a material towithstand sharp blows without fracturing. Many different procedures are used to

evaluate the impact resistance of metals depending on the brittleness of the

metals and of the nature of the application. The tension impact test can be used

on the most ductile metals while the torsion impact test is suitable for extremely

for material such as hardness tool steels.

The most commonly used impact for steels or the charpy and the izod

tester. These testers are made on small notched specimens broken in flexures

by a single below. The energy absorbed in breaking the specimens is measured.

The results are usually given in kilogram-meters without reference to the volume

of metal involved sudden bending of the specimen cause appearance of triaxial

tensile stress in the neighborhood of the base of the notch.

Impact strength I = K/A

K = energy

A = cross section area of the specimen

10

10

Striking edge for of pendulum

100 0.5628 22

75 8

47

10

Cantilever beam specimen and mounting for the IZOD TEST.


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PROCEDURE :

(1) Check that the latching tube is fitted in horizontal position for izod test and

fully tightened in place.

(2) Check the izod striker is fitted with the hammer.

(3) Check with the help of wedge shaped setting gauge position the test piece

correctly and then the tighten allen ball fully to clamped the test piece tightly.

(4) Bring the reading pointer to maximum scale reading. Latch the hammer inthe raised position and allow it to swing freely pulling the release handle.

(5) Apply the break just then it reaches near the wise/specimen support to stop

the hammer.

(6) Note down the reading accurately. As absorbed energy.

Carry out the impact tester on three specimens and take average values of the

energy absorbed.

OBSERVATION:

Material --------

Izod Value -------

RESULT : The impact strength of mild steel specimen is

Izod value = -------- N/m

PRECAUTION : Three features of great importance are,

(1) Making the notch correctly.

(2) Locating the bottom of the notch properly.

(3) Placing the specimen properly in machine.

Stm Complete Experiments

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