material testing lab - 1...charpy impact test 19 8. brinell’s hardness test 22 9. rock well’s...

MATERIAL TESTING LAB - 1 CEL307

OBJECTIVES To introduce the students about conducting the

essential tests like hardness test, bending test,

compression test etc. on basic materials metal and

wood.

Prof. TARANATH S D BATCH 2015-16

COLLEGE OF ENGINEERING AND DESIGN DEPT. OF CIVIL ENGINEERING

MATERIAL TESTING LAB - 1

Sl. No List of Experiments Page No.

1. Tension Test on Steel Rod 01

2. Compression Test on Ductile Material 05

3. Bending Test on Wood 08

4. Torsion Test 10

5. Shear Test 14

6. Izod Impact Test 16

7. Charpy Impact Test 19

8. Brinell’s Hardness Test 22

9. Rock Well’s Hardness Test 26

10 Diamond Pyramid (Vickers’s) Hardness Test 28


[1]

MATERIAL TESTING LAB – 1 2015-16

Experiment No: 01 Date:

TENSION TEST ON STEEL ROD

Aim: -To conduct the tension test on ductile material and thereby to determine

1. Percentage increase in length

2. Percentage reduction in area

3. Yield stress

4. Working stress or permissible stress or safe stress.

5. Maximum tensile stress or ultimate stress

6. Breaking stress or failure stress

7. Young’s modulus of the material at elastic point

8. Proof resilience

9. Modulus of resistance

Equipment Required: - Universal

Testing Machine

1. Test specimen

2. Extensometer dial gauge with least count 0.01mm

3. Steel scale, slide calipers and screw gauge, support block, steel punch and hammer.

Theory: Ductile materials are characterized by their ability to yield at normal temperature. As the

specimen is subjected to an increasing load, its length first increases linearly with the load and at

a very slow rate. Hence the initial portion of the stress-strain diagram is a straight line with a steep

slope. But after a critical value of the stress is reached, the specimen undergoes a large deformation

with a relatively small increase in the applied load.

After certain maximum value of the load has been reached, the diameter of the specimen begins to

decrease because of local instability. This phenomenon is known as necking. After this stage of

necking, lower loads are sufficient to keep the specimen elongating further until it finally ruptures.


[2]


The stress at which yield is initiated is called yield strength of material. The stresses corresponding

to maximum load applied to the specimen is known as ultimate strength and the stress

corresponding to rupture is called breaking strength.

Procedure: -

1) Observe the specimen; measure the total length, parallel length and diameter. Mark the gauge length.

2) Fix the specimen between the upper and middle cross heads using the gripping devices. Take precautions to fix the test specimen in such a way as to ensure that the load is applied axially.

3) Fix the extensometer in its position. Adjust the extensometer and the linear scale to read zero initially.

4) Select a proper range of loading. 5) Switch on the machine. Take the extensometer reading at a constant increment of 400kg. 6) The yield point can be observed either –

a) By the kick back of the live needle of the load indicating dial. OR

b) By the rapid movement of extensometer dial at constant load reading.

Record the yield load(s), and remove the extensometer.

7) Now, start taking the deformation readings on the linear scale present on the loading unit. 8) At one stage, the live needle begins to return, leaving the dummy needle there itself. Note

down the load at that point as the ultimate load. Also, observe the neck formation on the

specimen.

9) Note down the reading of the live load and the linear scale at the point of failure of the specimen.

10) Switch of the machine; remove the broken specimen; and observe the nature of fracture. 11) Measure the final gauge length on the tested specimen and the diameter at the neck.

Observations: -

Initial Diameter of the Specimen D1 = ___________________mm

Total length Lt = ___________________mm

Parallel length Lp = ___________________mm

Initial gauge length Lo = ___________________mm

Diameter of the specimen at the neck after failure D2 = _____________mm

Final parallel Length Lf = ___________________mm

Final Gauge Length Lu = ___________________mm


[3]


Initial cross sectional area of the specimen A1= 𝜋𝑑1

2

4 = ______________mm2

Final cross sectional area of the specimen A2= 𝜋𝑑2

2

4 = ______________mm2

Tabular Column

Sl

No

Load in Kg Load in

N

Dial gauge

Div reading

Deformation

in mm=

D gauge

Div*LC

Stress

In N/mm

Strain

Stress = Load / Initial area of Specimen =_______________N/mm2

Strain = Deformation / Initial Gauge Length =_______________

1. Percentage elongation in length =100 x (Lu- Lo)/L o = ___________%

2. Percentage reduction in area =100 x (A1 - A2) /A1 =____________%

3. Yield stress or nominal stress = yield load / original area of c/s =____________N /mm2

4. Working stress = yield stress / (Factor of safety=1.85) =____________N/mm2

5. Maximum tensile stress = ultimate load / original area of c/s =____________N/mm2

6. Breaking stress = breaking load / original area of c/s =____________N/mm2

7. Stress within elastic point = pep =____________N/mm2

8. Strain corresponding to stress pep = εep =____________

9. Young’s modulus E= pep/εep =____________N/mm2


[4]


Graph: Stress v/s strain

Conclusion:

Reference Code: IS –1608-1995


[5]



COMPRESSION TEST

Aim: To conduct the compression test on brittle metal.

Equipment Required: -

1. Universal testing machine (UTM)

2. Cylindrical test specimen

3. Deformation dial gauge with least count 0.01 mm

4. Slide calipers

5. Compression plates (2 nos. top and bottom).

Procedure:

1. Observe the specimen; measure its diameter and length.

2. Place the specimen on the lower cross head.

3. Fix the dial gauge in its proper position. Adjust the dial reading to zero initially or note down

the dial reading corresponding to zero load.

4. Select a proper range of loading.

5. Switch on the machine take the dial gauge reading at a constant of 400 kg.

6. In this case, no yield point is observed. Continue the loading upto failure of specimen.

7. Switch off the machine; remove the tested specimen and observe the nature of fracture.

Sl

no

Load in

kg

Load in N Dial gauge

N

N x L.C Stress

N/mm2

Strain


[6]


From Graph: -

1. Stress within elastic limit = pep =____________N/mm2

2. Strain at the stress point Pep = eep =____________

3. Young’s modules E = pep / eep =____________N/mm2

Observations: -

Initial diameter of the specimen = d1 =______________mm

Final diameter of the specimen = d2 =______________mm

Initial Height of specimen = H1=______________mm

Final Height of Specimen = H2=______________mm

1. Initial area of the specimen = A1 =𝜋𝑑1

2

4 =_____________mm2

2. Final area of the specimen = A2=𝜋𝑑2

2

4 =_____________mm2

3. Percentage decrease in length = 𝐻1−𝐻2

𝐻1𝑥100 =_____________%

4. Percentage increase in area = 𝐴2−𝐴1

𝐴1𝑥100 =_____________%

5. Yield stress or nominal stress = yield load / original area of c/s =__________N/mm2

6. Working stress = yield stress / (Factor of safety=1.85) =__________N/mm2

7. Maximum Compressive stress = ultimate load / original area of c/s =__________N/mm2

8. Breaking Compressive stress = breaking load / original area of c/s =__________N/mm2

9. Compressive Stress within elastic point = pep =__________N/mm2

10. Compressive Strain at stress point pep = eep =__________

11. Young’s modulus in compr. = E = pep / eep =__________N/mm2

12. For ductile materials, 𝑴𝒂𝒙. 𝒄𝒐𝒎𝒑. 𝒔𝒕𝒓𝒆𝒔𝒔 = 𝒎𝒂𝒙 𝒄𝒐𝒎𝒑𝒓.𝒍𝒐𝒂𝒅

𝒐𝒓𝒊𝒈𝒊𝒏𝒂𝒍 𝒂𝒓𝒆𝒂 𝒐𝒇 𝒄/𝒔 =__________N/mm2

Conclusion:



[7]


Schematic representation of Compression Testing Machine


[8]



STATIC BENDING TEST ON WOOD

Aim: To determine the modulus of elasticity, horizontal shear stress, modulus of rupture by

bending test

Apparatus: Wood specimen of dimension 50x50x750 mm, Universal testing machine, dial gauge.

Theory: Bending is one of the important processes considered in the design of flexural members.

To determine the moment of resistance for the given material and its cross section can be

determined by static bending test.

Procedure:

1. Observe the specimen; mark the mid span point and draw right section lines through this point;

measure the cross sectional dimensions of the wooden beam.

2. Place the beam over roller supports such that the load will be at the mid span. Note the span.

3. Select the suitable load range.

4. Fix the dial gauge in its position to measure the central deflection.

5. Switch on the machine. Take the dial gauge readings at regular intervals of 40kg load. Remove

the dial gauge after about ten readings.

6. Continue the loading upto failure. Record the load at failure.

7. Switch off the machine; remove the tested specimen and observe the type of failure

Observations:

i. Type of wood : ii. Cross sectional dimensions : b x d = ___________

iii. Span : L = ___________

iv. Type of failure :


[9]


Tabular Column:

Sl. No P in kg P in N Deflection in mm (δ)

Calculations:

a. Moment of inetia of the cross section about the neutral

axis = 𝐼 =𝑏𝑑3

12 = _______________mm4

b. Section modulus = 𝑍 =𝑏𝑑2

6 = ______________mm3

c. Young’s modulus of elasticity= E=𝑊𝐿3

𝛿 48𝐼 = _____N/mm2

d. Maximum bending moment = 𝑀𝑓 =𝑊𝑓𝐿

4 = ______N-mm

(at failure)

Where Wf = load at failure in N

L = is the span in mm

e. Modulus of repture (bending) = 𝜎𝑓 =𝑀𝑓

𝑍 = ______N/mm2

Conclusions:


[10]



TORSION TEST

Aim: To determine the Behaviour of ductile steel when subjected to torsion and obtain the

following torsional properties:

1. Modulus of rigidity

2. Elastic shear strength

3. Resilience

4. Ultimate shear strength

5. Toughness

6. Ductility

Apparatus: Torsion testing machine, graduated scale, test specimen, Vernier caliper.

Theory: The test is carried out on specially designed torsion tasting machines to determine

modulus of elasticity in shear, yield strength and modulus of rupture. Torsion testing machine

consists of a rigid frame with two clutches for gripping the ends of the specimen and weighing

head, which grips the other end of the specimen. The clutches must be perfectly aligned to prevent

bending. The load is applied by rotating one chuck about the axis while the other measures the

amount of twisting moment or torque being applied on the test specimen. The chuck is rotated

either by motor or by hand crank through a system of gears. A twist-measuring device called

TROPTOMETER measures the deformation of the test specimen. Thin walled tubular specimens

are used in torsion test both in elastic and in-elastic range to minimize variation of stress. Further

longer specimens are preferred to enable measuring of the angle of twist accurately. Material is

homogenous, isotropic and elastic and also it is assumed that the plane sections before torsion

remain plane after torsion.


[11]


Figure:

Torsion Equation, 𝑇

𝐼𝑝=

𝑓𝑠

𝑅=

𝐶𝜃

𝐿

Where,

T = Applied torque in N –mm

Ip = Polar moment of Inertia = 𝜋𝑑4

32 mm4

fs = Shear stress N/ mm2

C = Modulus of rigidity = N/ mm2

θ = Angle of twist in radians

L = Length of shaft in mm

Procedure:

1. Observe the specimen; measure its initial diameter and length.

2. Mark a straight line parallel to the longitudinal axis of the specimen with a piece of chalk to

observe the twisting of the specimen.

3. Place the specimen in the end blocks and place the specimen in the whole assembly in the

specimen holder. See that the specimen is fixed with no slack.

4. Adjust the circular scale and the torque scale to read zero. See that the screw provided in the

torque scale arrangement is in contact with the main scale and the vernier of the circular scale

is in contact with the pendulum frame, initially.

5. Operate the machine manually. Record the torque scale reading at regular interval of 10 twist

upto 100 and at every 20 intervals upto 300.


[12]


6. Now remove the crank used for manual operation and connect the machine to an electric motor

through a clutch arrangement.

7. Take the torque scale readings from 600 onwards at an interval of 600 upto failure.

8. At the instant of failure, disengage the clutch. Record the twist as well as the torque at the

instant of failure.

9. Remove the tested specimen and observe the nature of fracture.

Observations:

a) Material of the specimen :

b) Diameter of the specimen : D = ______________ mm

c) Length of the specimen : L = _______________mm

d) Type of fracture :

Observations:

Least count of circular scale =

Least count of torque scale =

Angle of twist θ in rad Torque T N-mm

i) Polar moment of inertia of cross section = 𝐼𝑝 =𝜋𝑑4

32 = ____________mm4

ii) Modulus of rigidity = 𝐶 =𝑇𝐿

𝜃𝐼𝑝 = ____________N/mm2

Where, T= torque in N-mm

L = length of the specimen in mm

Ip = polar moment of inertia in mm4


[13]


Θ = angle of twist in radians.

Note: select a point on the straight line portion of Torque v/s twist diagram to calculate C.

iii) Modulus of rupture (torsion) = maximum shear stress at failure

𝜏 = 𝑇𝑚𝑎𝑥

𝜋𝑑3 = ___________N/mm2

Results and conclusions:


[14]



SHEAR TEST (SINGLE)

Aim: To determine the ultimate shear strength in single shear for ductile material

Equipment Required: -

1. Universal testing machine

2. Shear shackles for single shear

3. Slide calipers and screw gauge

4. Single shear specimen of mild

steel of height 25 mm.

Theory: A shearing stress acts parallel to a plane, whereas tensile and compressive stresses act

normal to a plane. There are two main types of shear stresses used in laboratories. One is called

direct or transverse shear stress and corresponds to the type of stress encountered in rivets, bolts

and beams.

The other type of shear stress is called pure or torsional shear and represents the kind of shear stress

encountered in a shaft subjected to pure torsion.

Direct Shear tests are usually employed to obtain a measure of shear strength and torsion test are

usually employed to evaluate the basic shear properties of the material.

Procedure

1. The diameter of the specimen is measured using slide calipers or screw gauge, the area of the

specimen is calculated

2. The specimen in then inserted inside the shear shackle and the specimen with the shackles is

placed inside the shear centre plate

3. The entire assembly is then placed on the lower cross head of the universal listing machine as

shown in figure

4. The adjustable or intermediate cross head is they moved down till it makes control with the top

of the center plate. Note that the load is applied on the specimen through the center plate

5. Load the specimen at steps of 25 kg ( 245.23 N )


[15]


6. The load of which the specimen in the single shear test

7. The experimental loading and the finally calculate the ultimate shear strength in N/mm2

Figure:

For Single Shear:

Sl

no

Type of

materia

l

Dia of

specimen

mm

Area of

specimen

mm 2

Fracture

load kg

Fracture

load

N

Ultimate

shear

Strength

N/mm 2

Shear Stress = Fracture load / Area of C/s of specimen =

N/mm2

Result: -

Ultimate shear strength of steel in single shear= ………………………… N/mm2



[16]



IZOD IMPACT TEST

Aim: - To determine the impact energy and specific impact factor for materials such as mild steel,

brass, copper, and aluminium by izod impact test.

Brief theory: A pendulum type single blow impact test in which the specimen, usually notched is

fixed at one end and broken by a falling pendulum. The energy absorbed as measured by the

subsequent use of the pendulum is a measure of impact strength or notch toughness.

Izod Impact Test Machine: - This is the most commonly used type. The specimen is fixed in the

anvil with the notch at the level of the top face and on side of the falling hammer. The hammer is

released from the fixed portion strikes the specimen which breaks and continues for some distances

on the other side. By means of a pointer which mover freely over a scale, the energy absorbed in

fracturing the test piece is recorded. The specimen may have single, two or three notches. The test

piece can be a square or round cross section. Usually a square cross section test piece is used for

testing. Angle of tip hammer striking the specimen at 85deg

Equipments required: Izod cum charpy impact testing machine, specimens with V –groove,

centerpiece, Allrn key.

Precautions:

1. After ascertaining that there will be no persons in the range of swinging the pendulum, operate

the izod lever. Now the pendulum will swing freely and specimen will be smashed.

2. Stop the swinging pendulum.

3. Note the reading on the dial corresponding to the pointer. The reading is to be taken from zero

count. This value gives the impact energy directly.


[17]


Procedure: -

1. Check the specimen for its standard dimensions.

2. Fix the appropriate striking edge to the hammer.

3. To find the frictional loss:

a) Raise the pendulum to its highest position where it gets locked (Potential energy stored =

30 Kg-m)

b) Set the dial to read 30Kg-m with the indicator showing black.

c) Press the lock lever, and then the pendulum releaser to release the pendulum.

d) Stop the oscillations of the pendulum using the brake.

e) Record the reading on the dial which indicates the frictional loss directly.

4. Fix the specimen in its holder:

The specimen should be placed vertically as a cantilever with the shorter end of the specimen

projecting above the holder and V-notch on the tension side.

5. Raise the position to its highest position once again where it gets locked. Set the dial to read

30 Kg-m. With the indicator showing black.

6. Release the pendulum by pressing down the lock lever first and then the pendulum releaser, to

rupture the specimen.

7. Use the brake to stop the oscillations of the specimen.

8. Record the dial reading depending upon whether the indicator is red or black.

9. Observe whether the specimen has broken completely.

OBSERVATIONS AND CALCULATIONS:

1. Material of the specimen :

2. Weight of the pendulum :

3. Length of the pendulum :

4. Angle of swing :

5. Frictional loss : Uf = ______________Kg-m


[18]


Specimen no. Specimen

dimensions

Observed

readings Uo

(Kg-m)

Impact energy OR impact

value UI = UO – Uf

Remarks

Kg-m joules

Conclusion:


Figure:


[19]



CHARPY IMPACT TEST

Aim: To determine the Charpy impact energy for a given material (mild steel)

Equipment required: -

a) Impact testing machine.

b) Charpy impact test specimen with u – notch.

c) Setting gauge, Slide clampers, Allen key, etc.

Precautions:

1. After ascertaining that there will be no persons in the range of swinging the pendulum,

operate the izod lever. Now the pendulum will swing freely and specimen will be smashed.

2. Stop the swinging pendulum.

3. Note the reading on the dial corresponding to the pointer. The reading is to be taken from

zero count. This value gives the impact energy directly.

Procedure: -

1. Check the specimen for its standard dimensions.

2. Fix the appropriate striking edge to the hammer.

3. To find the frictional loss:

a. Raise the pendulum to its highest position where it gets locked (Potential energy

stored = 30 Kg-m)

b. Set the dial to read 30Kg-m with the indicator showing black.

c. Press the lock lever, and then the pendulum releaser to release the pendulum.

d. Stop the oscillations of the pendulum using the brake.

e. Record the reading on the dial which indicates the frictional loss directly.

4. Fix the specimen in its holder:

The specimen should be placed vertically as a cantilever with the shorter end of the

specimen projecting above the holder and U-notch on the tension side.


[20]


5. Raise the position to its highest position once again where it gets locked. Set the dial to

read 30 Kg-m. With the indicator showing black.

6. Release the pendulum by pressing down the lock lever first and then the pendulum releaser,

to rupture the specimen.

7. Use the brake to stop the oscillations of the specimen.

8. Record the dial reading depending upon whether the indicator is red or black.

9. Observe whether the specimen has broken completely.

OBSERVATIONS AND CALCULATIONS:

1. Material of the specimen :

2. Weight of the pendulum :

3. Length of the pendulum :

4. Angle of swing :

5. Frictional loss : Uf = ______________Kg-m

Specimen

no.

Specimen

dimensions

Cross

sectional

dimensions

of the

specimen

below the

notch

Area of

the

cross

section

below

the

notch

A mm2

Observed

reading

U0

(Kg-m)

Impact

energy

UI =

Uo - Uf

(Kg-

m)

Impact

strength

KU=

UI/A

(Kg-

m/m2)

Remarks

Result: - Impact strength U/A = …………………. Kgm/mm2


[21]


Conclusion:


Figure:


[22]



BRINELL’S HARDNESS TEST

AIM: To determine the B.H.N for the given specimen.

Apparatus: Hardness testing machine, brinell’s micrometer, specimens, ball Indenter of 10mm

and 5 mm dia.

Theory: Hardness is a property of a material to resist permanent deformation. The hardness of a

material may be determined by conducting scratch test or by surface indentation methods.

The scratch test is normally used to determine the hardness of ceramic materials. Mohr’s scale of

hardness was one of the early attempts to evaluate the surface hardness of materials. This consists

of list of materials arranged in order of hardness with the diamond (hardness index =10) as the

hardest of all materials and Talc (hardness index =1) as the softest. Any material would scratch

any other material under test, which is below it in the list. Thus the hardness of unknown material

could be related to the scale by finding which material would or would not scratch it and thus find

the hardness index assigned to it.

Materials Hardness index

Diamond 10

Sapphire 9

Topaz 8

Quartz 7

Feldspar 6

Apatile 5

Flourspar 4

Calcite 3

Gypsum 2

Talc 1

Table -1


[23]


The indentation test is now being widely used due to its simplicity and accuracy. The indention

test involves producing permanent deformation by pressing indentor of some materials in to the

surface.

Value of K and range of hardness for different metals (For Brinell’s hardness test)

Sl. No. Metal Value of K Range of Brinell’s

hardness number

(HB)

1. Mild steel 30 67 – 500 kgf/mm2

2. Cast iron 30 -NA-

3. Brass 10 22 – 315 kgf/mm2

4. Gun metal 10 -NA-

5. Aluminium 5 11 – 158 kgf/mm2

Brinell test is conducted by forcing a hardened steel ball into the surface of a test piece by applying

standard load and maintaining load for 10 to 15 sec.

𝐵𝐻𝑁 = 𝑙𝑜𝑎𝑑

𝑎𝑟𝑒𝑎 𝑜𝑓 𝑖𝑚𝑝𝑟𝑒𝑠𝑠𝑖𝑜𝑛=

𝑃

𝐴𝑖

The diameter of the resulting impression is measured with the aid of calibrated microscope and the

Brinell hardness number is found out.

If ‘D’ is the diameter of the ball,‘d’ the diameter of the impression and ‘h’ the depth of impression,

Depth of impression ℎ = 𝐷−√𝐷2−𝑑2

2


[24]


Then by geometry: 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑖𝑚𝑝𝑟𝑒𝑠𝑠𝑖𝑜𝑛 = 𝜋𝐷

2(𝐷 − √𝐷2 − 𝑑2)

Hence Ball indentors of different diameter, say, 10mm, 5mm and 1mm are available. So depending

upon the thickness of the test piece the indentor must be chosen suitably. The loading for the test

must also be selected carefully. Suppose if we select a greater load for softer material test piece,

then the impression formed will be of the same diameter as that of the indentor. For different

material the ratio of P/ D2 has been standardized and is give in the table.

𝐵. 𝐻. 𝑁 = 2𝑃

𝜋𝐷(𝐷−√𝐷2−𝑑2)

Materials P/ D2

Steel and cast iron 30

Copper and Al alloys 10

Pure copper and aluminum 5

Lead, tin and tin alloys 1

Table –1 recommended ratio P/ D2 for BHN test

(Where P is in kgs and D is dia. of ball indentor in mm)

Procedure:

1. Remove the test piece from the sleeve and fix the indentor with the test piece inside the sleeve.

2. Place the test specimen on the platform


[25]


3. Nor set the required load for the corresponding specimen by turning the knob provided at the

side of the machine.

4. Bring the specimen into contact with indentor by turning the star handle slowly and the handle

is now slowly turned until there in sufficient contact between indentor and specimen.

5. Now turn the lever slowly towards the load position from the unload position. The longer

pointer moves and when it comes to rest, waits for 8-10 seconds for the entire application of

the load.

6. Now turn the lever slowly to the unload position, Now the entire load is being lifted off from

the specimen.

7. Turn the wheel and lower the platform and take out the specimen.

8. Measure the diameter of the impression made on the specimen (mm) using Brinell’s

Micrometer.

9. The results are tabulated.

Tabular Column:

Sl

no

Material K Ball dia

D mm

Load

F=KD2 kg

Dia of

indentation

mm d

BHN

Conclusion:

REFERENCE CODE:

IS –1500-1983

IS –1789-1961 Method of Brinell hardness test for grey cast iron.

IS –1790-1961 Method for Brinell hardness test for light metals and their alloys.


[26]



ROCK WELL’S HARDNESS TEST

Aim: To determine the Rockwell hardness number for hard materials such as mild steel and

moderately hard materials such as Brass and Aluminium.

Apparatus: Rockwell hardness tester, diamond indentor, ball indentors of 1/16” dia, specimen

Theory: Rock well test is widely used as it provides readily the hardness number which can be

read directly on the dial and no measurement of depth of impression is involved. In this test, the

depth of impression is calibrated on a dial into 100 divisions (1div = 0.01mm of impression depth)

is indicated by a pointer directly.

The indentors used for Rockwell test can be steel ball of various diameters such as 1/ 16 inch, 1/ 8

inch, 1/ 4 inch dia or diamond cone indentor with an included angle of 1200. The indenting loads

are 60 kgs, 100 kgs and 150 kgs. There are series of rock well hardness scales depending upon the

indentor and loads and are designated by A scale, B scale, C scale and so on.

Procedure:

1. Place the test specimen on the platform.

2. Insert the respective indentor inside the sleeve and tighten the screw. Check that there is no

movement of the indentor.

3. Now set the required load for the corresponding specimen by turning the knob provided by the

side of the machine.

4. Bring the specimen into contact with the indentor by turning the star handle slowly and the

handle is now slowly turned till the small pointer indicator the red mark on the small graduated

scale are on the dial.

5. Now turn the lever away from the position of the observer slowly. The longer pointer moves

and when it comes to rest, waits for 8 – 10 secs for the entire application of the load.


[27]


6. Now, turn the lever slowly to the original position. Now, the entire load is being lifted off from

the specimen.

7. The long pointer moves back and when it comes to rest position, note the reading on the outer

dial for hard materials such as mild steel and on the inner dial for moderately hard materials

such as brass and aluminium.

8. The reading of the dial directly gives the RHN.

9. The results are tabulated.

Tabular Column:

Sl. No Material Scale

Symbol

Indentor Total Load R.H.N

Conclusion:


Figure:


[28]



DIAMOND PYRAMID (VICKER’S) HARDNESS TEST

Aim: - To determine the Vickers hardness number of the given specimens

Theory: This test uses a square base diamond pyramid as the indentor. The included angle between

the opposite face of the pyramid is 136degrees. One advantage of this test that the impression

produced will be always geometrically similar. After an impression has been made, the size of the

impression is measured using a microscope or by a projecting a magnified image of the impression

on to a screen. Both diagonals of the impression are measured and the mean value of the diagonal

length ‘d’ is used in calculating hardness number. The size of the impression is related to hardness

in the same way.

𝑉𝐻𝑁 = 2𝑃 𝑠𝑖𝑛

136

2

0

𝑑2 N/mm2

Working Principle: Vickers hardness test is an indentation hardness test using a regular pyramid

having an apex angle of 136º and square base having smoothed off point made of diamond is

pressed in the material to be tested under a certain load. The produced impression is projected to

focusing front screen while the diagonals of the impression are measured by the means of

measuring equipment.

The Vickers hardness is found by referring corresponding tables.

Material Load in Kgs

Steel and Cast Iron 30

Copper & its alloys 10

Aluminum alloys 2.5


[29]


Procedure:

1. Prepare the specimen as per the standard procedure and place the polished specimen on the

platform/anvil.

2. Select the load by adjusting Load selection knob to the requirement, for ferrous material

the load selected is 30kgf, for non- ferrous material load selected is 20kgf, and set the Dwell

timer knob for 15 seconds for ferrous material and 20 seconds for non -ferrous material.

3. Raise the platform/anvil and bring the Microscope till the surface finish of the material is

clearly visible.

4. Bring the indenter onto the testing area & raise the platform so that the gap of 0.2mm to

0.25mm to be maintained between indenter & specimen’s surface.

5. Press the start button, the loading cycle starts gradually through a geared motor provided

with a drive – cam. The loading/ dwell / unloading cycle are fully automatic.

6. The indentation is now projected on front of focusing screen by turning the microscope on

the indentation area, Measure the diagonal d1 of the impression & measure d2 by offsetting

the index head to vertical position which is marked on the index head. For the mean value

of diagonals, find out the Vickers hardness number by referring the table (supplied).

7. Take three trial values and average is taken as the Vickers hardness number.

8. To have next test, change the position of specimen where hardness is to be checked. Verify

from front focusing screen that there is no earlier indentation near about expected new

indentation. Index the head to original position and bring back indenter on specimen.

Repeat operation from 1 to 8.

Note: Vickers hardness value is always measured with reference to the load applied.

HV Load = Number

Say HV 30 = 350


[30]


Applications:

Since the test indentation is very small in a Vickers test, it is useful for a variety of applications:

1. Testing very thin materials like foils or measuring the surface of a part, small parts or small

areas.

2. Measuring individual microstructures, or measuring the depth of case hardening by sectioning

a part and making a series of indentations to describe a profile of the change in hardness.

3. The Vickers method is more commonly used.

Conclusion:

Reference Code: IS –1501: PART III-1987

Figure:

material testing lab - 1...charpy impact test 19 8. brinell’s hardness test 22 9. rock well’s...

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