Mech CE6315 som lab_manual

Strength of Materials Laboratory Manual / Observation
Department of Mechanical Engineering Page 1
KIT - KALAIGNARKARUNANIDHI INSTITUTE OF TECHNOLOGY
Coimbatore - 641 402
DEPARTMENT OF MECHANICAL ENGINEERING
STRENGTH OF MATERIALS LABORATORY
Name
Reg. No.
Class, Branch and Section
MANUAL / OBSERVATION

LIST OF EXPERIMENT
S. No. Name of the Experiment
1 Tensile Test on a Mild Steel Rod
2 Double Shear Test on Mild Steel Rod
3 Torsion Test on Mild Steel Rod
4 Impact Test on Metal Specimen – Izod Method
5 Impact Test on Metal Specimen – Charpy Method
6 Hardness Test on Metals – Rockwell Hardness Number
7 Hardness Test on Metals – Brinnell Hardness Number
8 Deflection Test on Beam
9 Compression Test on Helical Spring
10 Effect of Hardening – Improvement in Hardness and Impact Resistance of Steels
11 Improvement of Mechanical Properties
12 Tempering and Hardening

INDEX
S. No. Date Name of the Experiment Page No. Faculty Sign
Tensile Test on a Mild Steel Rod
Double Shear Test on Mild Steel Rod
Torsion Test on Mild Steel Rod
Impact Test on Metal Specimen – Izod Method
Impact Test on Metal Specimen – Charpy Method
Hardness Test on Metals – Rockwell Hardness Number
Hardness Test on Metals – Brinnell Hardness Number
Deflection Test on Beam
Compression Test on Helical Spring
Effect of Hardening – Improvement in Hardness and
Impact Resistance of Steels
Improvement of Mechanical Properties
Tempering and Hardening

TENSILE TEST ON A MILD STEEL ROD
Aim:
Conduct a tensile test on a mild steel rod and determine yield stress, ultimate
stress, breaking stress, percentage of elongation and percentage of decrease in cross
sectional area of the rod.
Apparatus Required:
 Universal testing machine.
 Extensometer.
 Vernier Caliper.
 Steel rule.
 Mild Steel Specimen.
Procedure:
 The diameter of the specimen is measured at top, middle and bottom and the
average is determined.
 Gauge length is marked by leaving suitable length at both the ends.
 The load range in the UTM is chosen appropriately to the given diameter of
the rod and to the ultimate stress assumed.
 The rod is rigidly fixed in between the grips and the test piece should be held
in such a way that the load is applied as axially as possible.
 The extensometer is fixed for measuring elongation of gauge length.
 The load is applied and the extensometer reading is noted for uniform
increment of loads.
 The extensometer is removed before the yield point.
 The yield load shown by the backward movement of the pointer is noted.
 The load is further applied and the ultimate load is noted.
 The breaking load is noted at which the specimen breaks.
 The specimen is released from the grips.
 Final dimensions (i.e., increment in gauge length and reduction in diameter at
neck) of the specimen are measured.

Formulae:
(1). Yield stress = Yield load/CSA N/mm2
(2). Ultimate stress = Ultimate load/CSA N/mm2
(3). Breaking stress = Breaking load/Neck area N/mm2
(4). % of elongation = Increase in length/Original length x 100 %
(5). % of decrease in CSA = Decrease in CSA/Original area x 100 %
Observation:
Length of rod (Gauge) = mm
Diameter of rod = mm
Area of rod = mm2
Final gauge length = mm
Increase in length = mm
Final diameter (neck) = mm
Neck area = mm2
Yield load = kg
Ultimate load = kg
Breaking load = kg
Calculation:

Result:
By conducting test on mild steel rod the following results were determined:
(1). Yield stress = N/mm2
(2). Ultimate stress = N/mm2
(3). Breaking stress = N/mm2
(4). % of elongation = %
(5). % of decrease in CSA = %

DOUBLE SHEAR TEST ON MILD STEEL ROD
Aim:
To determine the double shear stress of the mild steel rod.
Apparatus Required:
 UTM.
 Double shear setup.
 Specimen.
Procedure:
 The specimen is placed into the rectangular device present in the double shear
setup.
 The above setup is placed in the bottom portion of the UTM. The moving head
of the UTM is placed in the top of the rectangular device.
 Now the hydraulic pressure is applied on the rod by turning the knob present
in the hydraulic machine. The maximum load at which the specimen fails is
noted. The final diameter of the rod is measured.
 The double shear stress is calculated using the formula.
Formula:
Double shear stress = Load at failure/(2A) N/mm2
Observation:
Material =
Diameter of rod (d) = mm
CSA of rod (A) = mm2
Load at failure (W) = N

Calculation:
Result:
The double shear stress of the given specimen = N/mm2

TORSION TEST ON MILD STEEL ROD
Aim:
To determine the torsional stress and modulus of rigidity of the given
specimen.
Apparatus Required:
 Torsion testing machine.
 Vernier caliper.
 Steel rule.
 Specimen.
Procedure:
 Before testing, the measuring range is adjusted according to the capacity of the
test piece counter weight of the pendulum is adjusted correctly.
 The specimen is then held in the driving chuck and driven chuck with the help
of handles. The angle measuring dial is also adjusted to zero position.
 Black pointer is adjusted at the starting position the thread from the driving
chuck pulley is taken over small pulleys.
 The machine is started and the specimen is subjected to torsion.
 The torque is measured at suitable interval of angle twist.
 Angle of twist and the torque are measured at the failure of the specimen.
Formulae:
Polar moment of inertia (J) = πd4
/32 mm4
Torsional stress (QMax) = (T x r)/J N/mm2
Modulus of rigidity (N) = (T x l)/(J x ) N/mm2

Observation:
Length of specimen between grip (l) = mm
Diameter of the specimen (d) = mm
Torque at failure (T) = N mm
Angle of twist () = radian
[i.e.,  = (No. of turns x 360) + remaining angle of twist]
[Degree to radian = ( x π)/180]
Calculation:
Result:
Angle of twist () = radian
Torsional stress (QMax) = N/mm2
Modulus of rigidity (N) = N/mm2

IMPACT TEST ON METAL SPECIMEN – IZOD METHOD
Aim:
To determine the impact strength of mild steel square specimen using izod
method.
Apparatus Required:
 Impact testing machine.
 Guide plate.
 Mild steel specimen.
Procedure:
 The specimen is kept truly vertical in the notch vice so that the centre of the
notch is in level with the top of the vice so that the notch is facing the
direction of the blow. The one-third portion of the specimen (25 mm) should
be projected above the vice and remaining portion (50 mm) should lie inside
the vice.
 The pointer is set at maximum of the dial.
 The lever is released and the pendulum hammer is allowed to swing.
 The pointer in the dial gives the energy absorbed in friction down.
 The pendulum is locked in its original position.
 The latch is released and the pendulum is allowed to strike the specimen.
 The energy spent is breaking or bending the specimen is noted down from the
dial.
 The impact strength is calculated using the formula.
Formula:
Impact strength = Impact value/CSA of the specimen below notch J/mm2

Observation:
Type of notch =
Length of specimen =
Breadth of specimen =
Position of groove from one end =
Depth of groove =
Width of groove =
Tabulation:
S. No. Specimen
Initial reading
(E1) in J
Final reading
(E2) in J
Impact value
(E1 – E2) in J
Impact Strength
in J/mm2
Average
Calculation:
Result:
Impact value (Izod method) = J
Impact strength (Izod method) = J/mm2

IMPACT TEST ON METAL SPECIMEN – CHARPY METHOD
Aim:
To determine the impact strength of mild steel square specimen using charpy
method.
Apparatus Required:
 Guide plate.
 Mild steel specimen.
Procedure:
 The hammer is raised and locked.
 The pointer is set at the maximum graduated energy range of the dial.
 The trigger is released and the pendulum hammer is allowed to swing. This
actuates the pointer to move in the dial.
 The pointer shows the energy absorbed by the bearingwithout specimen and it
is noted.
 The hammer is again raised and locked.
 The specimen is placed in between the simple anvil support keeping the
45 degrees V-notch in the opposite direction to the striking edge of the
hammer.
 The specimen is adjusted such that the striking edge of hammer and V-notch
coincides in the same alignment.
 The pointer is set to read the maximum energy range marked in the dial.
 The lever is released and the pendulum is allowed to strike the specimen at its
midpoint.
 The energy spent is breaking or bending the specimen is observed.
 The results are tabulated and the impact strength is calculated using the
formula.

Formula:
Impact strength = Impact value/CSA of the specimen below notch J/mm2
Observation:
Type of notch =
Length of specimen =
Breadth of specimen =
Position of groove from one end =
Depth of groove =
Width of groove =
Tabulation:
S. No. Specimen
Initial reading
(E1) in J
Final reading
(E2) in J
Impact value
(E1 – E2) in J
Impact Strength
in J/mm2
Average
Calculation:
Result:
Impact value (Charpy method) = J
Impact strength (Charpy method) = J/mm2

HARDNESS TEST ON METALS – ROCKWELL HARDNESS NUMBER
Aim:
To determine the rockwell hardness number of the given specimen.
Apparatus Required:
 Rockwell hardness testing machine.
 Indentor.
 Test specimen.
Procedure:
 In the rockwell hardness testing machine is a direct reading instrument based
on the principle of different depth measurement is used in this test. The
penetrator or indicator scale load for the particular material to be tested is
chosen from the table.
Material Penetrator Load (kg) Scale
Relatively soft material Diamond cone 60 A
Fairly hard material 1/16 ball pointer 100 B
Hard material Diamond cone 150 C
S. No. Rockwell ‘B’ Rockwell ‘C’
1 Diameter of ball = 1.5875 mm Angle of top of the diamond cone = 120 degrees
2 --- Radius of curvature at the tip of the cone = 0.2 mm
3 Preliminary load = 100 N Preliminary load = 100 N
4 Additional load = 900 N Additional load = 1400 N
5 Total load = 1000 N Total load = 1500 N
 The surface of the specimen is cleaned by emery sheet. The specimen is kept
on the testing platform.
 The platform is raised until the small pointer in the dial reads against the red
mark and the lengthy pointer against the set position.

 The load is applied gradually and maintained till the lengthy pointer comes to
rest. The load is released gradually.
 After releasing the load the dial reading is observed. This is Rockwell
hardness number of the specimen.
 The same procedure is repeated for at least six times.
 The average value of the Rockwell hardness number is obtained.

Observation:
Indentor =
Dial =
Scale =
Load =
Indentor radius =
Tabulation:
S. No. Specimen
Reading (HRB)
Mean (HRB)
1 2 3
Result:
The rockwell hardness number for the given material (HRB)
1.
2.
3.

HARDNESS TEST ON METALS – BRINNELL HARDNESS NUMBER
Aim:
To determine the brinnell hardness number of the given specimen.
Apparatus Required:
 Brinnell hardness testing machine.
 Indentor.
 Test specimen.
Procedure:
 Keep the operating lever in horizontal position.
 Place the specimen on testing table.
 Turn the hand wheel in CW direction so that the specimen will push the
indentor.
 Lift the operating lever from horizontal position upwards slightly after which
it rotates automatically.
 Wait till the lever becomes standstill.
 Bring the lever back to horizontal position.
 Turn back the hand wheel and remove the specimen. Carry the same
procedure for further specimen.
 Measure the diameter of the impression by brinnell microscope and find out
brinnell hardness number.
Formula:
Brinnell hardness number (BHN) = 2P/{πD[D - sq. root (D2
– d2
)]}
Observation:
Total load (P) = kg
Diameter of ball (D) = mm
Indentor =
Dial =

Tabulation:
S. No. Specimen
Diameter of Indentation (d) in mm
BHN
1 2 3 Mean
Calculation:
Result:
The brinnell hardness number for the given material (BHN)
1.
2.
3.

DEFLECTION TEST ON BEAM
Aim:
To determine the deflection of SS beam experimentally and compare with the
theoretical values and draw the deflection curve.
Apparatus Required:
 Dial gauge.
 Weight.
 Weight hanger.
 Metre scale.
 Beam specimen.
 Beam setup.
Procedure:
 The beam is SS using knife edges and weight hanger is kept at the centre to
apply concentrated load at the centre.
 Three dial gauges are fixed at L/4, L/2 and 3L/4 positions to measure the
deflection at the points.
 Load is applied gradually in steps of 0.5 kg and corresponding dial gauge
readings a noted.
 Deflection curve is drawn on graph with the proper scale.
Formulae:
Deflection at L/4 and 3L/4 position is, yA = yC = 11PL3
/(768EI) mm
Deflection at L/2 position is, yB = PL3
/(48EI) mm
where, I = Area M.I = bd3
/12 mm4
E = Young’s modulus = 2.1 x 105
N/mm2
P = Load N

Observation:
Specimen length (L) = mm
Specimen breadth (b) = mm
Specimen thickness (d) = mm
Tabulation:
S. No.
Load (P)
in kg
Actual deflection (Dial gauge reading)
in mm
Theoretical deflection in mm
yA yB yC yA yB yC
Calculation:

Graph:
Load (X-axis) Vs Deflection (Y-axis)
Result:
Deflection curve are drawn for the given beam. Experimental values are
compared with theoretical values.

COMPRESSION TEST ON HELICAL SPRING
Aim:
To determine the modulus of rigidity of the given open coiled helical spring
under compression.
Apparatus Required:
 Compression testing machine.
 Spring testing assembly.
 Open coiled helical spring.
Procedure:
 The diameter of the wire, radius, pitch and number of turns of the spring are
measured using vernier caliper.
 The helix angle is calculated using the pitch of the spring.
 The spring is placed in the test setup.
 Initial reading in the scale is noted.
 The deformations are recorded for the corresponding applied load.
 Similarly the deformations are recorded while unloading.
 The modulus of rigidity of the spring is calculated using the formula.
Formulae:
Maximum shear stress (QMax) = 8WD/(πd3
) N/mm2
Stiffness of spring (S) = W/y N/mm
Modulus of rigidity (G) = 8WD3
n/(yd4
) N/mm2

Observation:
Diameter of the spring wire (d) = mm
Diameter of the spring coil (D1) = mm
Mean diameter of spring coil (D) = D1 – d
= mm
Number of turns (n) =
Height of spring (h) = mm
Pitch (p) = h/n
= mm
Helix angle (α) = p/(πD)
= degrees
Tabulation:
S. No.
Load (W) in kN
Deflection
(y) in mm
Modulus of
rigidity (G) in
N/mm2
Stiffness
(S) in
N/mm
Maximum
shear stress
(QMax) in
N/mm2
Loading Unloading Mean
Average
Calculation:

Graph:
Load (X-axis) Vs Deflection (Y-axis).
The slope of the graph gives stiffness.
Result:
Modulus of rigidity (G) = N/mm2
Stiffness of spring (S) = N/mm
Maximum shear stress (QMax) = N/mm2

EFFECT OF HARDENING – IMPROVEMENT IN HARDNESS
AND IMPACT RESISTANCE OF STEELS
Aim:
To determine the hardness and impact resistance of the given hardened
material and compare them with unhardened material.
Apparatus Required:
 Muffle furnace.
 Hardness testing machine.
 Specimen.
Description:
Hardening can be defined as a heat treatment process in which the steel is
heated to a temperature within or above its critical range and held at this temperature
for a considerable time to ensure thorough penetration of the temperature inside the
component and allowed to cool by quenching in water, oil or brine solution.
Procedure:
 The specimen is hardened as stated above.
 Now the specimen is polished using emery papers of various grades.
 Hardness number of the hardened specimen is found by rockwell hardness
testing machine.
 The same specimen is used for determination of impact strength from impact
testing machine.
 The calculated hardness numbers and impact strength are tabulated separately.
Result:
The hardness number and impact strength of the hardened specimen are
compared with the unhardened specimen.

IMPROVEMENT OF MECHANICAL PROPERTIES
Aim:
To compare the mechanical properties of various hardened specimen like
unhardened, quenched, quenched & tempered specimens.
Apparatus Required:
 Muffle furnace.
 Hardness testing machine.
 Oil, water or brine solution.
 Specimen.
Description:
Quenching is an operation of rapid cooling by immersing a hot piece into a
quenching bath.
Tempering is defined as the process of reheating the hardened specimen to
some temperature before the critical range followed by any rate of cooing such as
reheating permits the trapped temperature to transform and relieve the internal
stresses.
Procedure:
 An ordinary unhardened specimen is taken and its hardness number is found
by rockwell hardness testing machine.
 The test specimen whose hardness number was found already in the
unhardened stage is placed inside the heat treatment furnace after making the
temperature of the furnace s 800 degree C, the specimen is heated for at least
one hour continuously and then it is taken out by holder and it is cooled
rapidly by dipping it into quenching bath.
 The hardness number of this specimen is found by RHTM.
 Again the specimen is reheated (i.e., tempering is done).
 The hardness number of the tempered specimen is found.
 The results are compared.

Result:
The report is given by comparing three different hardness values of the
specimen, which was subjected to various heat treatment processes.

TEMPERING AND HARDENING
Aim:
To perform the heat treatment (A) Tempering and (B) Hardening on the given
material C-40 steel.
Apparatus Required:
 Muffle furnace: Tongs.
 Given material: C-40 Steel.
 Quenching medium: Water.
Procedure:
(A)Tempering:
 The given specimen is subjected to rockwell hardness test and rockwell
hardness number is measured before hardening that the specimen is subjected
to rough grinding.
 The specimen is placed inside the combustion chamber of muffle furnace and
is heated upto 630 degree C.
 Then the specimen is soaked for 10 minutes at the same temperature 630
degree C.
 After soaking it is taken out from the furnace and it is cooled in air.
 The specimen is cooled, now the tempering is completed.
 Again the specimen is subjected to rockwell hardness test and rockwell
hardness number is measured.
(B) Hardening:
 The given specimen is subjected to rockwell hardness test and rockwell
hardness number is measured before hardening.
 The specimen is placed inside the combustion chamber of muffle furnace and
is heated upto 830 degree C.
 Then the specimen is soaked for 10 minutes at the same temperature 830
degree C.
 After soaking it is taken out from the furnace and it is quenched in the water.

 The specimen is cooled, now the hardening is completed.
 Again the specimen is subjected to rockwell hardness test and rockwell
hardness number is measured.
Tabulation:
S. No.
Specimen
Material
Load in N Penetrator Scale RHN
Mean
RHN
(A) Tempering:
(B) Hardening:
Result:
The heat treatment (A) Tempering and (B) Hardening on the given material
C-40 steel and its rockwell hardness number is measured.
Heat Treatment Rockwell hardness number
Before tempering
After tempering
Before hardening
After hardening

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