Loading...
Menu

Strength of Materials Lab Manual

p<>{color:#000;}.

DEPARTMENT OF MECHANICAL ENGINEERING

CE6315 – STRENGTH OF MATERIALS LABORATORY MANUAL

Prepared by

Keerthi Kumar B (AP/Civil)

Saranya K (AP/Civil)

A LIST OF BASIC SAFETY RULES

 

1. When you handle chemicals wear eye protection (chemical splash goggles or full face shield).

2. When you work with furnaces for heat treatment procedures or other thermally activated equipment you should use special gloves to protect your hands.

3. Students should wear durable clothing that covers the arms, legs, torso and feet. (Note: sandals, shorts, tank tops etc. have no place in the lab. Students inappropriately dressed for lab, at the instructors discretion, be denied access)

4. To protect clothing from chemical damage or other dirt, wear a lab apron or lab coat. Long hair should be tied back to keep it from coming into contact with lab chemicals or flames.

5. In case of injury (cut, burn, fire etc.) notify the instructor immediately.

6. In case of a fire or imminently dangerous situation, notify everyone who may be affected immediately; be sure the lab instructor is also notified.

7. If chemicals splash into someone’s eyes act quickly and get them into the eye wash station, do not wait for the instructor.

8. In case of a serious cut, stop blood flow using direct pressure using a clean towel, notify the lab instructor immediately.

9. Eating, drinking and smoking are prohibited in the laboratory at all times.

10. Never work in the laboratory without proper supervision by an instructor.

11. Never carry out unauthorized experiments. Come to the laboratory prepared. If you are unsure about what to do, please ask the instructor.

12. Always remember that HOT metal or ceramic pieces look exactly the same as COLD pieces are careful what you touch.

13. Know the location and operation of:

*
p<>{color:#000;}. Fire Alarm Boxes

*
p<>{color:#000;}. Exit Doors

*
p<>{color:#000;}. Telephones

LABORATORY CLASSESINSTRUCTION TO STUDENTS

1. Students must attend the lab classes with ID cards and in the prescribed uniform.

2. Boys-shirts tucked in and wearing closed leather shoes. Girls‟ students with cut shoes, overcoat, and plait incite the coat. Girls‟ students should not wear loose garments.

3. Students must check if the components, instruments and machinery are in working condition before setting up the experiment.

4. Power supply to the experimental set up/ equipment/ machine must be switched on only after the faculty checks and gives approval for doing the experiment. Students must start to the experiment. Students must start doing the experiments only after getting permissions from the faculty.

5. Any damage to any of the equipment/instrument/machine caused due to carelessness, the cost will be fully recovered from the individual (or) group of students.

6. Students may contact the lab in charge immediately for any unexpected incidents and emergency.

7. The apparatus used for the experiments must be cleaned and returned to the technicians, safely without any damage.

8. Make sure, while leaving the lab after the stipulated time, that all the power connections are switched off.

CONTENTS

table=. =. |=.
p={color:#000;}. Ex.

No.


=.
h1={color:#000;}. Date
=.
h1={color:#000;}. Name of the Experiment
=.
h1={color:#000;}. Page No.
=.
h1={color:#000;}. Marks
=.
h1={color:#000;}. Signature of staff
=.
=.
=.
=.
=.
=.
=.
=.
=.
=.
=.
=.
=.

Ex. No : TENSILE TEST ON MILD STEEL ROD

Date :

Objective:

To develop an understanding of stress-strain curves of materials, and learn how to use

them to determine various mechanical properties of ductile materials

.

Aim:

To conduct tension test on the given ductile material to determine the following ,

#
p<>{color:#000;}. Yield stress.

#
p<>{color:#000;}. Nominal Breaking Stress .

#
p<>{color:#000;}. Actual Breaking Stress

#
p<>{color:#000;}. Ultimate stress.

#
p<>{color:#000;}. Percentage of reduction in area.

#
p<>{color:#000;}. Percentage of increase in length.

 

Theory:

  The tensile test is most applied one, of all mechanical tests. In this test ends of test piece is fixed into grips connected to a straining device and to a load measuring device. If the applied load is small enough, the deformation of any solid body is entirely elastic. An entirely deformed solid will return to its original form as soon as load is removed. However, if the load is too large, the material can be deformed permanently. The initial part of the tension curve, which is recoverable immediately after unloading ,is termed as elastic and the rest of the curve, which represents the manner in solid undergoes plastic deformation is termed as plastic. The stress below which the deformation is essentially entirely elastic is known as the yield strength of material. In some materials the onset of plastic deformation is denoted by a sudden drop in load indication both an upper and a lower yield point. However, some materials do not exhibit a sharp yield point. During plastic deformation, at larger extensions strain hardening cannot compensate for the decrease in section and thus the load passes through the maximum and then begins to decrease. At this stage the “ultimate strength”, which is defined as the ratio of the load on the specimen to the original cross sectional area, reaches the maximum value. Further loading will eventually cause neck formation and rupture. Usually a tension test is conducted at room temperature and the tensile load is applied slowly. During this test either round or flat specimens may be used. The round specimens may have smooth or threaded ends. The load on the specimen is applied mechanically or hydraulically depending on the type of testing machine.

 

Application:

 

The stress values found out from the experiment are used for the design of Reinforced Concrete, Prestressed Concrete, Steel structural elements.

 

Apparatus Required:

 

*
p<>{color:#000;}. Universal testing machine

*
p<>{color:#000;}. Vernier caliper

*
p<>{color:#000;}. Scale

*
p<>{color:#000;}. Specimen

Formula used:

*
p<>{color:#000;}. Yield Stress = N/mm2

*
p<>{color:#000;}. Ultimate Stress = N/mm2

*
p<>{color:#000;}. Nominal Breaking Stress = N/mm2

*
p<>{color:#000;}. Actual Breaking Stress = N/mm2

*
p<>{color:#000;}. % reduction in area = X 100

*
p<>{color:#000;}. % of increase in length = X 100

Procedure:

*
p<>{color:#000;}. Diameter of the specimen is measured.

*
p<>{color:#000;}. Fix the specimen at the two grip of UTM.

*
p<>{color:#000;}. Left valve of testing machine is opened.

*
p<>{color:#000;}. Release the cross head to move the grip up and down.

*
p<>{color:#000;}. Open the right valve slightly and then close the pushes and rest button.

*
p<>{color:#000;}. The machine is started and load is applied uniformly on the specimen. Readings are noted.

*
p<>{color:#000;}. The yield load, breaking load, Ultimate load are noted.

*
p<>{color:#000;}. The specimen is removed and the diameter of the neck and elongated gauge length are measured.

Observations:

*
p<>{color:#000;}. Ultimate load =

*
p<>{color:#000;}. Breaking load =

*
p<>{color:#000;}. Original diameter of rod =

*
p<>{color:#000;}. Original gauge length =

*
p<>{color:#000;}. Original area =

*
p<>{color:#000;}. Final neck diameter =

*
p<>{color:#000;}. Final gauge length =

*
p<>{color:#000;}. Final neck area =

Tabulation:

table=. =. |=.
p={color:#000;}. Sr. No |=.
p={color:#000;}. Type of load |=.
p={color:#000;}. Cross Sectional Area in mm^2^ |=.
p={color:#000;}. Load in KN |=.
p={color:#000;}. Stress in N/mm^2^ | =. |=.
p={color:#000;}. 1.

|=. p={color:#000;}.

Yield point load

 

|=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   | =. |=. p={color:#000;}. 2. |=. p={color:#000;}.

Ultimate load

 

|=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   | =. |=. p={color:#000;}. 3. |=. p={color:#000;}.

Breaking point load

 

|=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |

Model Calculation:

*
p<>{color:#000;}. Yield Stress = N/mm2

=

= N/mm2

*
p<>{color:#000;}. Ultimate Stress = N/mm2

=

= N/mm2

*
p<>{color:#000;}. Nominal Breaking Stress = N/mm2

=

= N/mm2

*
p<>{color:#000;}. Actual Breaking Stress = N/mm2

=

= N/mm2

*
p<>{color:#000;}. % of reduction in area = X 100

= X 100

= %

*
p<>{color:#000;}. % of increase in length = X 100

= X 100

= %

Result:

*
p<>{color:#000;}. Ultimate Stress =

*
p<>{color:#000;}. Nominal Breaking Stress =

*
p<>{color:#000;}. Actual Breaking Stress =

*
p<>{color:#000;}. Yield Stress =

*
p<>{color:#000;}. % of reduction in cross sectional area =

*
p<>{color:#000;}. % increase in length =

Inferences:

Viva Questions:

 

*
p<>{color:#000;}. Which steel have you tested? What is its carbon content?

*
p<>{color:#000;}. In what region of a stress vs. strain graph do you find Young’s Modulus?

*
p<>{color:#000;}. What general information is obtained from the tensile test regarding the properties of the material?.

*
p<>{color:#000;}. What kind of fracture has occurred and why?

*
p<>{color:#000;}. Which is the most ductile material? What is its elongation?

Ex. No : DETERMINATION OF ULTIMATE SHEAR STRENGTH

Date : OF STEEL (DOUBLE SHEAR TEST)

Objective:

To determine the double shear strength of the given Mild Steel Rod and aluminium rod.

Aim:

To conduct double shear test on the given ductile material.

Theory:

In actual practice when a beam is loaded the shear force at a section always comes to play along with bending moment. It has been observed that the effect of shearing stresses compared to bending stress is quite negligible. But sometimes, the shearing stress at a section assumes much importance in design calculations. Universal testing machine is used for performing shear, compression and tension. There are two types of UTM.

1. Screw type

2. Hydraulic type.

Hydraulic machines are easier to operate. They have a testing unit and control unit connected to each other with hydraulic pipes. It has a reservoir of oil, which is pumped into a cylinder, which has a piston. By this arrangement, the piston is made to move up. Same oil is taken in a tube to measure the pressure. This causes movement of the pointer, which gives reading for the load applied.

Application:

 

Double shear strength is used in the design of double cover butt joint (revetted and bolted)

Apparatus Required:

*
p<>{color:#000;}. Compression testing machine or universal testing machine

*
p<>{color:#000;}. Double shear apparatus

*
p<>{color:#000;}. Vernier calliper

*
p<>{color:#000;}. Mild Steel Rod

Formula Used:

Ultimate shear stress = N/mm2

Procedure:

*
p<>{color:#000;}. Measure the diameter of rod and fix the specimen in a double shear assembly with proper side grips.

*
p<>{color:#000;}. Apply the load gradually to the specimen by keeping the double shear assembly in between the plates of CTM or UTM.

*
p<>{color:#000;}. Note down the ultimate load at the time of failure.

*
p<>{color:#000;}. Ultimate load at failure divided by twice the cross sectional area of the specimen gives the ultimate shear stress.

Observation:

*
p<>{color:#000;}. Diameter of the specimen =

*
p<>{color:#000;}. Cross sectional area of specimen =

Tabulation:

table<>. <>. |<>/2.
p={color:#000;}. Sr. No |<>/2.
p={color:#000;}. Specimen |<>\2.
p={color:#000;}. Ultimate load

 

|<>/2. p={color:#000;}. Ultimate shear stress in N/mm^2^ | <>. |<>. p={color:#000;}. Kg |<>. p={color:#000;}. N | <>. |<>. p={color:#000;}.  

1.

 

|<>. p={color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}.  

2.

 

|<>. p={color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}.  

3.

 

|<>. p={color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |

Model Calculation:

Ultimate shear stress = N/mm2

= N/mm2

Result:

Ultimate shear stress of the specimen = N/mm2

Inferences:

VIVA-QUESTIONS :

*
p<>{color:#000;}. What are the factors affect the strength column?

*
p<>{color:#000;}. What is pure bending of beam?

*
p<>{color:#000;}. What is shear center or angle of twist?

 

 

Ex. No : TORSION TEST ON MILD STEEL ROD

Date :

[Objective:
**]

To determine the modulus of rigidity, Maximum shear stress of the given specimen by conducting torsion test.

Aim:

To conduct the torsion test for the given specimen.

Theory:

A torsion test is quite instrumental in determining the value of modulus of rigidity of a metallic specimen. The value of modulus of rigidity can be found out thought observations made during the experiment by using the torsion equation.

Where, T = Torque applied,

Ip = Polar moment of inertia

<>.
p<>{color:#000;}. =
<>.
p<>{color:#000;}. Modulus of rigidity,
<>.
<>.
<>.
<>.

Application:

Shear stress is used to determine the diameter of the shaft in pumps, turbine.

Apparatus Required:

*
p<>{color:#000;}. Torsion testing machine

*
p<>{color:#000;}. Vernier caliper

*
p<>{color:#000;}. Scale

*
p<>{color:#000;}. Mild Steel Rod

Formula Used:

*
p<>{color:#000;}. Shear stress, τ = N/mm2

*
p<>{color:#000;}. Polar moment of inertia, J = mm4

*
p<>{color:#000;}. Modulus of rigidity, C = N/mm2

Where, T = Torque in Nm

d = Diameter of the specimen

θ = Angle of twist in radian

l = Length of the specimen

Procedure:

*
p<>{color:#000;}. The diameter of the given specimen is measured.

*
p<>{color:#000;}. Place the specimen between rhe chucks and grip the specimen tightly.

*
p<>{color:#000;}. Torque is applied gradually and corresponding angular twist is noted.

*
p<>{color:#000;}. Within the torque range the readings are taken.

*
p<>{color:#000;}. Modulus of rigidity is evaluated.

Graph:

A graph is drawn by taking angle of twist at X-axis and torque on Y-axis the resultant straight line is passing through maximum number of points and origin.

Observation:

*
p<>{color:#000;}. Diameter of specimen =

*
p<>{color:#000;}. Length of specimen =

Tabulation:

table=. =. |=/2.
p={color:#000;}. Sr. No |=\2.
p={color:#000;}. Angle of twist (θ) |=\2.
p={color:#000;}. Torque (T) |=.
p={color:#000;}. Modulus of rigidity © |=.
p={color:#000;}. Shear stress

(τ) | =. |=.
p={color:#000;}. Degree |=.
p={color:#000;}. Radian |=.
p={color:#000;}. Kg-cm |=.
p={color:#000;}. N-mm |=.
p={color:#000;}. (N/mm2) |=.
p={color:#000;}. (N/mm2) | =. |=.
p={color:#000;}.  

1.

 

|=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   | =. |=. p={color:#000;}.  

2.

 

|=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   | =. |=. p={color:#000;}.  

3.

 

|=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   | =. |=. p={color:#000;}.  

4.

 

|=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   | =. |=. p={color:#000;}.  

5.

 

|=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |=. p={color:#000;}.   |

Model Calculation:

Polar moment of inertia, J = mm4

=

=

Angle of twist, θ = X radian (to convert from degree to radian)

=

Torque, T = X 98.1 N-mm (to convert from Kg-cm to N-mm)

=

Shear stress, τ = N/mm2

=

Modulus of rigidity, c = N/mm2

=

=

From graph,

Shear stress, τ = N/mm2

=

=

Modulus of rigidity, c = N/mm2

=

=

 

 

 

Result:

Shear stress, τ =

Rigidity modulus, C=

From graph

Rigidity modulus, C =

Inference:

Viva – Questions:

*
p<>{color:#000;}. What is the shear stress at the centre of shaft?

*
p<>{color:#000;}. Where the shear stress is maximum in a shaft?

*
p<>{color:#000;}. Why hollow shafts are better than a solid shaft?

*
p<>{color:#000;}. Give the relationship between Young’s modulus and shear modulus.

*
p<>{color:#000;}. Name two structural elements subjected to torsion.

Ex. No : IZOD IMPACT TEST ON METAL SPECIMEN

Date :

Objective:

To determine the impact strength of given mild steel specimen.

Aim:

To conduct the impact test of given mild steel specimen.

Theory:

The impact test signifies toughness of material that is ability of material to absorb energy during plastic deformation. Static tension tests of unnotched specimens do not always reveal the susceptibility of a metal to brittle fracture. This important factor is determined by impact test. Toughness takes into account both the material. Several Engineering materials have to with stand impact or suddenly loads while in service. Impact strengths are generally lower as compared to strengths achieved under slowly applied loads of all types of impact tests, the notched bar test are most extensively used. Therefore, the impact test measures the energy necessary to fracture a standard notched bar by applying an impulse load. The test measures the notch toughness of material under shocking loading. Values obtained from these tests are not of much utility to design problems directly and are highly arbitrary. Still it is important to note that it provides a good way of comparing toughness of various materials or toughness of same material under different conditions. This test can also be used to assess the ductile brittle transition temperature of the material occurring due to lowering of temperature

Application:

In the design of machine elements (power hammer) subjected to impact loads.

Apparatus Required:

*
p<>{color:#000;}. Specimen

*
p<>{color:#000;}. Impact testing machine

*
p<>{color:#000;}. Vernier calliper

Formula Used:

Cross section area of the specimen under notch, A = Breadth X Depth under notch mm2

Impact value of the specimen = (Absorbed Energy / Area of the cross section

under notch) J/mm2

Procedure:

*
p<>{color:#000;}. Raise the hammer and lock it.

*
p<>{color:#000;}. Set the pointer at the maximum graduated energy range of the dial.

*
p<>{color:#000;}. Release the trigger and allow the pendulum to swing and the pointer to move within the dial.

*
p<>{color:#000;}. Note down the energy observed in the dial and lock the pendulum in original position.

*
p<>{color:#000;}. Keep the specimen vertically in the vice notch. So the centre of mark is levelled with the top of the vice notch taking the direction below the 28mm portion should produce upward and remaining portion should be kept inside the vice.

*
p<>{color:#000;}. Note down the energy spends in bending specimen from the dial and tabulated the result.

Tabulation:

Dimension of the specimen:

table<>. <>. |<>.
p={color:#000;}. Sr. No |<>.
p<>{color:#000;}. Initial Energy

#
p={color:#000;}. in joule

|<>. p<>{color:#000;}. Residual Energy (B) in

Joule |<>.
p={color:#000;}. Absorbed Energy (A-B) | <>. |<>.
p={color:#000;}.  

1.

 

|<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   | <>. |<>. p={color:#000;}.  

2.

 

|<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   | <>. |<>. p={color:#000;}.  

3.

 

|<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |

Model Calculation:

Cross section area of the specimen under notch, A = Breath X Depth under notch mm2

=

=

*
p<>{color:#000;}. Impact value of the specimen = (Absorbed Energy / Area of the cross section

under notch) J/mm2

Result:

*
p<>{color:#000;}. Impact value of the specimen =

*
p<>{color:#000;}. Energy absorbed by the specimen =

Inferences:

[* Viva- Questions: *]

*
p<>{color:#000;}. Define impact load?

*
p<>{color:#000;}. Give the dimensions of the specimen for Izod test?

*
p<>{color:#000;}. How to mount the specimen for the Izod test?

*
p<>{color:#000;}. What do you infer from the initial reading dial reading?

*
p<>{color:#000;}. Why the stress induced due to suddenly applied load is greater than the stress due to gradually applied load.?

Ex. No : CHARPY TEST ON METAL SPECIMEN

Date :

Objective:

To determine the impact strength of given mild steel specimen by conducting charpy test.

Aim:

To conduct impact test (Charpy test) of Mild steel specimen.

Theory:

The impact test signifies toughness of material that is ability of material to absorb energy during plastic deformation. Static tension tests of unnotched specimens do not always reveal the susceptibility of a metal to brittle fracture. This important factor is determined by impact test. Toughness takes into account both the material. Several Engineering materials have to with stand impact or suddenly loads while in service. Impact strengths are generally lower as compared to strengths achieved under slowly applied loads of all types of impact tests, the notched bar test are most extensively used. Therefore, the impact test measures the energy necessary to fracture a standard notched bar by applying an impulse load. The test measures the notch toughness of material under shocking loading. Values obtained from these tests are not of much utility to design problems directly and are highly arbitrary. Still it is important to note that it provides a good way of comparing toughness of various materials or toughness of same material under different conditions. This test can also be used to assess the ductile brittle transition temperature of the material occurring due to lowering of temperature.

Application:

In the design of machine elements (power hammer) subjected to impact loads.

Apparatus Required:

*
p<>{color:#000;}. Impact testing machine

*
p<>{color:#000;}. Mild Steel Specimen

Formula Used:

Cross section area of the specimen under notch, A = Breadth X Depth under notch mm2

Impact value of the specimen = (Absorbed Energy / Area of the cross section

under notch) J/mm2

Procedure:

*
p<>{color:#000;}. Raise the hammer and lock it.

*
p<>{color:#000;}. Set the pointer at the maximum graduate energy range of dial.

*
p<>{color:#000;}. Release the trigger and allow the pendulum to swing and the pointer to move within the dial.

*
p<>{color:#000;}. Note down the energy observed in the dial and lock the pendulum in original position.

*
p<>{color:#000;}. Keep the specimen horizontally in the vice. So the centre mark faces the non striking end of the pendulum.

*
p<>{color:#000;}. Allow the pendulum to strike the specimen

*
p<>{color:#000;}. Note down the energy spends in breaking the specimen from dial and tabulate the result.

Tabulation:

Dimension of the specimen:

table<>. <>. |<>.
p={color:#000;}. Sr. No |<>.
p<>{color:#000;}. Initial Energy

#
p={color:#000;}. in joule

|<>. p<>{color:#000;}. Residual Energy (B) in

Joule |<>.
p={color:#000;}. Absorbed Energy (A-B) | <>. |<>.
p={color:#000;}.  

1.

 

|<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   | <>. |<>. p={color:#000;}.  

2.

 

|<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   | <>. |<>. p={color:#000;}.  

3.

 

|<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |

Model Calculation:

Cross section area of the specimen under notch, A = Breath X Depth under notch mm2

=

=

Impact value of the specimen = (Absorbed Energy / Area of the cross section

under notch) J/mm2

Result:

*
p<>{color:#000;}. Impact value of the specimen =

*
p<>{color:#000;}. Energy absorbed by the specimen =

Inferences:

Viva – Questions:

*
p<>{color:#000;}. Define Toughness.

*
p<>{color:#000;}. Give the dimensions of the specimen for Charpy test?

*
p<>{color:#000;}. How to mount the specimen for the Charpy test?

*
p<>{color:#000;}. What do you infer from the initial reading dial reading?

*
p<>{color:#000;}. What are the differences between Izod and Charpy test?

Ex. No : ROCKWELL HARDNESS TEST

Date :

Objective:

To determine the Rockwell hardness number and compare the hardness of the materials.

Aim:

To conduct Rockwell Hardness test for Mild Steel, Aluminium and Copper.

Thoery:

Rock well hardness test consists in touching an indenter of standard cone or ball into the surface of a test piece in two operations and measuring the permanent increase of depth of indentation of this indenter under specified condition. From it, Rockwell hardness is deduced. The ball (B) is used for soft materials (e.g. mild steel, cast iron, aluminium, brass.) and the diamond cone © for hard ones (High carbon steel. etc.)

HRB means Rockwell hardness measured on B scale

 HRC means Rock well hardness measured on C scale

Application:

In the design of machine elements where friction exists, it is necessary to ascertain the hardness of the material.

Apparatus Required:

*
p<>{color:#000;}. Rockwell hardness testing machine.

*
p<>{color:#000;}. Specimens

*
p<>{color:#000;}. Steel ball, Diamond cone intender.

Procedure:

*
p<>{color:#000;}. For the given specimen load is selected using table.

*
p<>{color:#000;}. The surface of the specimen is cleaned before placing it on the movable platform.

*
p<>{color:#000;}. The platform with the specimen moved until the surface of the specimen touches the intender to get the smallest point in the dial towards red mark.

*
p<>{color:#000;}. Select the load selection in turned and load is applied and maintained on the specimen by pressing the load levers.

*
p<>{color:#000;}. The initial loading of 100 Kg reads against the red mark. Then apply the load and maintain until longer pointer comes to rest.

*
p<>{color:#000;}. The load on the specimen is raised gently passing down release the levers.

*
p<>{color:#000;}. Hardness number is noted and the procedure is repeated and the values are tabulated.

Tabulation: 1

table<>. <>. |<>.
p={color:#000;}.  

Sr. No

 

|<>. p={color:#000;}.  

Material |<>.
p={color:#000;}.  

Load in Kg |<>.
p={color:#000;}.  

Penetrator |<>.
p={color:#000;}.  

Scale |<>.
p={color:#000;}.  

Hardness | <>. |<>.
p={color:#000;}.  

1.

 

|<>. p={color:#000;}. Aluminium |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   | <>. |<>. p={color:#000;}.  

2.

 

|<>. p={color:#000;}. Aluminium |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   | <>. |<>. p={color:#000;}.  

3.

 

|<>. p={color:#000;}. Aluminium |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |

Tabulation: 2

table<>. <>. |<>.
p={color:#000;}.  

Sr. No

 

|<>. p={color:#000;}.  

Material |<>.
p={color:#000;}.  

Load in Kg |<>.
p={color:#000;}.  

Penetrator |<>.
p={color:#000;}.  

Scale |<>.
p={color:#000;}.  

Hardness | <>. |<>.
p={color:#000;}.  

1.

 

|<>. p={color:#000;}. Copper |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   | <>. |<>. p={color:#000;}.  

2.

 

|<>. p={color:#000;}. Copper |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   | <>. |<>. p={color:#000;}.  

3.

 

|<>. p={color:#000;}. Copper |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |

Tabulation: 3

table<>. <>. |<>.
p={color:#000;}.  

Sr. No

 

|<>. p={color:#000;}.  

Material |<>.
p={color:#000;}.  

Load in Kg |<>.
p={color:#000;}.  

Penetrator |<>.
p={color:#000;}.  

Scale |<>.
p={color:#000;}.  

Hardness | <>. |<>.
p={color:#000;}.  

1.

 

|<>. p={color:#000;}. Mild Steel |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   | <>. |<>. p={color:#000;}.  

2.

 

|<>. p={color:#000;}. Mild Steel |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   | <>. |<>. p={color:#000;}.  

3.

 

|<>. p={color:#000;}. Mild Steel |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |

Result:

*
p<>{color:#000;}. The Rockwell hardness number of Aluminium =

*
p<>{color:#000;}. The Rockwell hardness number of Copper =

*
p<>{color:#000;}. The Rockwell hardness number of Mild Steel =

Inferences:

Viva – Questions:

*
p<>{color:#000;}. Define Hardness?

*
p<>{color:#000;}. Why diamond tip drill bits are used in drilling operations?

*
p<>{color:#000;}. What is penetration?

*
p<>{color:#000;}. Copper is harder than aluminium true or false?

*
p<>{color:#000;}. What is the significance of minor load applied in Rockwell hardness test?

Ex. No : BRINELL HARDNESS TEST

Date :

Objective:

To determine the Brinell hardness number and compare the hardness of the materials.

Aim:

To conduct Brinell Hardness test for Mild Steel, Aluminium and Copper.

Theory:

It consists of pressing a hardened steel ball into a test specimen. In this test usually a steel ball of Diameter D under a load “P” is forced into the test piece and the mean diameter “d” of the indentation left in the surface after removal of load is measured. According to ASTM specifications a 10 mm diameter ball is used for the purpose. Lower loads are used for measuring hardness of soft materials and vice versa. The Brinell hardness is obtained by dividing the test load P by curved surface area of indentation. This curved surface is assumed to be portion of the sphere of diameter D.

Application:

In the design of machine elements where friction exists, it is necessary to ascertain the hardness of the material.

Apparatus Required:

*
p<>{color:#000;}. Brinell hardness testing machine.

*
p<>{color:#000;}. Specimens

Formula:

Brinell hardness number, BHN =

Where, P = Load in Newton

D = Diameter of the intender in mm

d = Diameter of indentation in mm

Procedure:

*
p<>{color:#000;}. For the given specimen load is selected using table.

*
p<>{color:#000;}. The surface of the specimen is cleaned before placing it on the movable platform.

*
p<>{color:#000;}. The platform with the specimen moved until the surface of the specimen touches the intender to get the smallest point in the dial towards red mark.

*
p<>{color:#000;}. Select the load selection in turned and load is applied and maintained on the specimen by pressing the load levers.

*
p<>{color:#000;}. The initial loading of 100 Kg reads against the red mark. Then apply the load and maintain until longer pointer comes to rest.

*
p<>{color:#000;}. The load on the specimen is raised gently passing down release the levers.

*
p<>{color:#000;}. The diameter of the penetrator and the indentation diameter are noted.

*
p<>{color:#000;}. Hardness numbers are calculated by using the above formula.

Tabulation: 1

table<>. <>. |<>.
p={color:#000;}. Sl. No

 

|<>. p={color:#000;}.  

Material |<>.
p={color:#000;}.  

 

Load in Kg |<>.
p={color:#000;}. Indenter diameter D mm |<>.
p={color:#000;}. Diameter of impression d mm |<>.
p={color:#000;}. Brinell Hardness number |<>.
p<>{color:#000;}. Mean Brinell Hardness Number | <>. |<>/3.
p<>{color:#000;}.

1 |<>/3.
p={color:#000;}.

Mild steel |<>.
p<>{color:#000;}.  

|<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |

Tabulation: 2

table<>. <>. |<>.
p={color:#000;}. Sl. No

 

|<>. p={color:#000;}.  

Material |<>.
p={color:#000;}.  

 

Load in Kg |<>.
p={color:#000;}. Indenter diameter D mm |<>.
p={color:#000;}. Diameter of impression d mm |<>.
p={color:#000;}. Brinell Hardness number |<>.
p<>{color:#000;}. Mean Brinell Hardness Number | <>. |<>/3.
p<>{color:#000;}.

1 |<>/3.
p={color:#000;}.

Aluminium |<>.
p<>{color:#000;}.  

|<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |

Tabulation: 3

table<>. <>. |<>.
p={color:#000;}. Sl. No

 

|<>. p={color:#000;}.  

Material |<>.
p={color:#000;}.  

 

Load in Kg |<>.
p={color:#000;}. Indenter diameter D mm |<>.
p={color:#000;}. Diameter of impression d mm |<>.
p={color:#000;}. Brinell Hardness number |<>.
p<>{color:#000;}. Mean Brinell Hardness Number | <>. |<>/3.
p<>{color:#000;}.

1 |<>/3.
p={color:#000;}.

Copper |<>.
p<>{color:#000;}.  

|<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |

Model Calculation:

Brinell hardness number, BHN =

=

Result:

*
p<>{color:#000;}. The Brinell hardness number of Aluminium =

*
p<>{color:#000;}. The Brinell hardness number of Copper =

*
p<>{color:#000;}. The Brinell hardness number of Mild Steel =

Inferences:

Viva – Questions:

*
p<>{color:#000;}. Bring out the differences between Rockwell hardness test and Brinell hardness test?

*
p<>{color:#000;}. How will you calculate the load for Brinell hardness test?

*
p<>{color:#000;}. Mild steel is harder than Copper true or false?

*
p<>{color:#000;}. What is the value of minor load to be applied in Brinell hardness test?

Ex. No : DEFLECTION TEST ON BEAM

Date :

Objective:

To find Young’s modulus of given material by conducting deflection test.

Aim:

To conduct the deflection test for the simply supported steel beam.

Theory:

If a beam is simply supported at the ends and carries a concentrated load at the center, the beam bends concave upwards. The distance between the original position of the beam and its position after bending is different at different points along the length if the beam, being maximum at the center in this case. This difference is called ‘deflection’. In this type of loading the maximum amount of deflection is given by the relation,

Where δ = Deflection in mm

W= load acting at the center, N

l=length of the beam between the supports, mm

E=young’s modulus of material of the beam, N/mm 2

I=second moment of area of the cross section (moment of inertia) of the beam,

about the neutral axis, mm 4

 

 

 

 

 

 

Bending stress:

 

As per bending equation,

 

 

 

 

Where M= bending moment, Nmm

I= moment of inertia, mm 4

s =Bending stress, N/mm 2

y=distance of the fiber of the beam from the neutral axis.

Application:

To compare the actual deflection of the structural elements with the allowable deflection specified by the codes.

Apparatus Required:

*
p<>{color:#000;}. Beam of any cross section.

*
p<>{color:#000;}. Support

*
p<>{color:#000;}. Hanger

*
p<>{color:#000;}. Set of weights.

*
p<>{color:#000;}. Deflectometer

*
p<>{color:#000;}. Scale

Formula Used:

Moment of Inertia, I = mm4

Young’s modulus, E = [L3 – a2 – x2] N/mm2

Where, δ = Deflection in mm

w = Load in N

E = Young’s modulus in N/mm2

I = Moment of Inertia in mm4

L = Length of the beam in mm

a = Distance between LH support and deflection meter in mm

x = Distance between RH support and load in mm

Procedure:

*
p<>{color:#000;}. Find the distance between the support span and mark the midpoint.

*
p<>{color:#000;}. Place the deflection meter. So that the tip of head just touches the midpoint.

*
p<>{color:#000;}. Note the readings of deflection meter.

*
p<>{color:#000;}. The beam is loaded gradually in steps till the maximum deflection is one tenth of every increment of beam.

*
p<>{color:#000;}. Note the deflection for beam and also unloading corresponding steps in which it is loaded and deflection are noted.

 

 

 

 

Observation:

Specimen – Mild steel

Breadth of cross section (b) =

Length of beam (L) =

Depth of cross section (d) =

Distance between LH support and deflection meter (a) =

Distance between RH support and load (x) =

Tabulation:

 

table<>. <>. |<>/2.
p={color:#000;}. Sr. No |<>\2.
p={color:#000;}. Load |<>\2.
p={color:#000;}. Deflection Reading |<>/2.
p={color:#000;}.  

Mean deflection

mm |<>/2.
p={color:#000;}. Young’s modulus

N/mm^2^ | <>. |<>.
p={color:#000;}. Kg |<>.
p={color:#000;}. N |<>.
p={color:#000;}. Loading |<>.
p={color:#000;}. Unloading | <>. |<>.
p={color:#000;}.  

1.

|<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}.  

2.

|<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}.  

3.

|<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}.  

4.

|<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}.  

5.

|<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |

 

Model Calculation:

Moment of Inertia, I = mm4

=

=

Young’s modulus, E = [L2 – a2 – x2] N/mm2

=

=

Graph:

*
p<>{color:#000;}. The graph is plotted between the load Vs deflection. Load is taken in Y-axis and deflection in X-axis.

Result:

*
p<>{color:#000;}. Young’s modulus of given beam =

*
p<>{color:#000;}. From graph =

Inferences:

[* Viva- Questions: *]

*
p<>{color:#000;}. Define Youngs modulus?

*
p<>{color:#000;}. What is deflection?

*
p<>{color:#000;}. Define Beam.

*
p<>{color:#000;}. Define flexural rigidity.

*
p<>{color:#000;}. What is the nature of stress induced in a beam?

Ex. No : COMPRESSION TEST ON HELICAL SPRING

Date :

Objective:

To determine the modulus of rigidity and stiffness of the given compression spring specimen.

Aim:

To conduct the compression test for helical spring.

Apparatus and specimen required:

 

*
p<>{color:#000;}. Spring test machine

*
p<>{color:#000;}. Compression spring specimen

*
p<>{color:#000;}. Vernier caliper

 

Procedure:

 

*
p))))<>{color:#000;}. Measure the outer diameter (D) and diameter of the spring coil (D) for the given compression spring.

 

*
p<>{color:#000;}. Count the number of turns i.e. coils (n) in the given compression specimen.

 

*
p)))<>{color:#000;}. Place the compression spring at the centre of the bottom beam of the spring testing machine.

 

*
p))<>{color:#000;}. Rise the bottom beam by rotating right side wheel till the spring top rouches the middle cross beam.

 

*
p<>{color:#000;}. Note down the initial reading from the scale in the machine.

 

*
p))<>{color:#000;}. Apply a load of 25kg and note down the scale reading. Increase the load at the rate of 25kg upto a maximum of 100kg and note down the corresponding scale readings.

 

*
p))))<>{color:#000;}. Find the actual deflection of the spring for each load by deducting the initial scale reading from the corresponding scale reading.

 

*
p<>{color:#000;}. Calculate the modulus of rigidity for each load applied by using the following formula:

 

 

Modulus of rigidity, N = 64PR^3^n d4δ

 

Where, P = Load in N

 

R = Mean radius of the spring in mm (D –d /2) d = Diameter of the spring coil in mm

 

δ = Deflection of the spring in mm

D = Outer diameter of the spring in mm.

 

*
p<>{color:#000;}. Determine the stiffness for each load applied by using the following formula:

*
p<>{color:#000;}. Stiffness, K = P/δ

 

*
p))))<>{color:#000;}. Find the values of modulus of rigidity and spring constant of the given spring by taking average values.

 

 

table<>. <>. |_.
p<>{color:#000;}. [* *
**] |<>\6.
p<>{color:#000;}. Observation: |<>\3.
p<>{color:#000;}.  

|<>\3. p<>{color:#000;}.   |<>\3. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}. 1. |<>\5. p<>{color:#000;}. Material of the spring specimen |<>\3. p))))>{color:#000;}. = |<>\3. p<>{color:#000;}.   |<>\3. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}. 2. |<>\5. p<>{color:#000;}. Outer diameter of the spring. D |<>\3. p))))>{color:#000;}. = |<>\3. p((((<>{color:#000;}. mm |<>\3. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}. 3. |<>\5. p<>{color:#000;}. Diameter of the spring coil, d |<>\3. p))))>{color:#000;}. = |<>\3. p((((<>{color:#000;}. mm |<>\3. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}. 4. |<>\5. p<>{color:#000;}. Number of coils / turns, n |<>\3. p))))>{color:#000;}. = |<>\3. p((((<>{color:#000;}. Nos. |<>\3. p<>{color:#000;}.   | <>. |<>\5. p<>{color:#000;}. 5. Initial scale reading |<>. p<>{color:#000;}.   |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\2. p<>{color:#000;}. = |<>\3. p)))))={color:#000;}. cm |<>\2. p<>{color:#000;}. = mm | <>. |<>\5. p<>{color:#000;}.  

 

Tabulation:

 

|<>. p<>{color:#000;}.   |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>\3. p<>{color:#000;}. Sl.No. |<>\2. p<>{color:#000;}. Applied Load in |<>\3. p<>{color:#000;}. Scale reading in |<>. p<>{color:#000;}.   |<>\2. p)={color:#000;}. Actual |<>. p={color:#000;}.   |<>\2. p={color:#000;}. Modulus of |<>. p={color:#000;}.   |<>. p={color:#000;}. Stiffness in | <>. |<>\3. p<>{color:#000;}.   |<>. p<>{color:#000;}. kg |<>. p<>{color:#000;}. N |<>. p<>{color:#000;}. cm |<>\2. p<>{color:#000;}. mm |<>. p<>{color:#000;}.   |<>\2. p={color:#000;}. deflection |<>. p={color:#000;}.   |<>\2. p={color:#000;}. rigidity |<>. p={color:#000;}.   |<>. p={color:#000;}. N/mm | <>. |<>\3. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\2. p)={color:#000;}. in mm |<>. p={color:#000;}.   |<>\2. p={color:#000;}. inN/mm^2^ |<>. p={color:#000;}.   |<>. p={color:#000;}.   | <>. |<>\3. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>\3. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\5. p={color:#000;}. Average |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>\4. p<>{color:#000;}. Result: |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\2/2. p={color:#000;}. N/mm2 |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>\8. p<>{color:#000;}. The modulus of rigidity of the given spring |<>\3. p>{color:#000;}. = ------------------- |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>\6. p<>{color:#000;}. The stiffness of the given spring |<>\2. p<>{color:#000;}.   |<>\3. p>{color:#000;}. = ------------------- |<>. p<>{color:#000;}.   |<>\2. p={color:#000;}. N/mm2 |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |

Inferences:

Viva question:

*
p<>{color:#000;}. Define pricipal stresses and principal plane.

*
p<>{color:#000;}. What is radius of mohr’s circle?

*
p<>{color:#000;}. What is the use of mohr’s circle?

Ex. No : STRAIN MEASUREMENT OF CANTILEVER BEAM

Date :

Aim:

 

To determine the Strain of the cantilever beam subjected to Point load at the free end and to plot the characteristic curves.

 

Apparatus required:

*
p<>{color:#000;}. Cantilever Beam Strainguage Trainer Kit

 

*
p<>{color:#000;}. Weights and Multimeter

 

Formula used:

 

Strain, S = 6PL / BT^2^E

Where,

 

P=Load applied in Kg.

L = Effective length of the beam in cm.

B = Width of the beam in cm.

T = thickness of the beam in cm.

E = young’s modulus = 2×109Kg/cm2.

S = Micro strain.

 

Theory:

 

When the material is subjected to any external load, there will be small change in the Mechanical properties like thickness of the material or change in the length depending upon the nature of load applied to the material. The change in mechanical properties will remain till the load is released. The change in the property is called Strain (or) material gets strained.

 

Strain S = ∂L/L

 

Since the change in length is very small, it is difficult to measure ∂L, so the strain is measured in micro strain. Since it is difficult to measure the length, Resistance strain gauge are used to measure strain in the material directly. Strain gauges are bonded directly on the material using special adhesive s. As the material get strained due to load applied the resistance of the strain gauge changes proportional to the load applied. This change in resistance is used to convert mechanical property into electrical signal which can be easily measured and stored for analysis.

 

The change in the resistance of the strain gauge depends on the sensitivity of the strain gauge which is expressed in terms of a gauge factor, Sg

Sg = ∆R /R

The output ∆R/R of a strain gauge is usually converted into voltage signal with a

 

Wheatstone bridge. If a single gauge is used in one arm of Wheatstone bridge and equal but fixed resistors is used in the other arm, the output voltage is Eo =Ei / 4(∆R g /Rg)

 

E~o~ =1/4(EiS~g~ ∆)

 

The input voltage is controlled by the gauge size and the initial resistance of the gauge. As a result, the output voltage Eo usually ranges between 1 to 10 ∆V / micro units of strain.

 

 

Procedure:

 

*
p))<>{color:#000;}. The instrument is switched on ( i.e.,). The display glows to indicate the instrument is ON.

*
p)))<>{color:#000;}. The Instrument is allowed to be in ON position for 10 minutes for initial worm-up.

*
p<>{color:#000;}. From the selector switch, FULL or HALF bridge configuration is selected.

*
p<>{color:#000;}. The potentiometer is adjusted for ZERO till the displays reads ‘ 000’

*
p))<>{color:#000;}. 1 Kg load is applied on the pan of the cantilever the CAL Potentiometer is adjusted till the display reads 377 micro strains. When the weights are removed the display should come to ZERO, in case of any variation, ZERO Potentiometer is adjusted again and the procedure is repeated again. Now the instrument is calibrated to read micro strains.

*
p)))<>{color:#000;}. Then the loads are applied on the pan in steps of 100 gm up to 1kg. When the cantilever is strained, instrument displays exact micro strain.

*
p)))))<>{color:#000;}. The readings are noted down in the tabular column . Percentages error in readings, hysteresis and accuracy of the instrument can be calculated by comparing with the theoretical results.

 

Tabulation:

 

table<>. <>. |<>/8.
p={color:#000;}. Sl.

No |<>/8.
p={color:#000;}. Weight

(gms) |<>\2.
p={color:#000;}.  

|<>/8. p={color:#000;}. Actual

readings(using formula)

Micro strains |<>.
p={color:#000;}.  

|<>\2. p={color:#000;}. Display readings |<>/8. p={color:#000;}. Error

% |<>.
p<>{color:#000;}.  

| <>. |<>\2. p<>{color:#000;}.   |<>\2/7. p={color:#000;}. While

loading

micro strains |<>/7.
p={color:#000;}. While unloading

micro strains |<>.
p<>{color:#000;}.  

| <>. |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}. 1 |<>. p<>{color:#000;}. 100 |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}. 2 |<>. p<>{color:#000;}. 200 |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}. 3 |<>. p<>{color:#000;}. 300 |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}. 4 |<>. p<>{color:#000;}. 400 |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}. 5 |<>. p<>{color:#000;}. 500 |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}. 6 |<>. p<>{color:#000;}. 600 |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}. 7 |<>. p<>{color:#000;}. 700 |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}. 8 |<>. p<>{color:#000;}. 800 |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}. 9 |<>. p<>{color:#000;}. 900 |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}. 10 |<>. p<>{color:#000;}. 1000 |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\3. p<>{color:#000;}. % ERROR = |<>\4. p(<>{color:#000;}. (Actual reading Display reading) x 100 |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\2. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\2. p<>{color:#000;}. Max Weight (gms) |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |

Result:

 

Thus the strain of the cantilever beam subjected to free end loading, is obtained in micro strains and the characteristics curves – Load Vs Strain, Output Voltage Vs Strain and Actual Vs Display readings are plotted.

Inferences:

Ex. No : DETERMINATION OF HARDENING EFFECTS ON STEEL

Date :

Objective:

To determine the hardening effect of the given steel specimen.

Aim:

To study heat treatment processes (hardening and tempering) of steel specimen.

Theory:

Properties of metals and alloys can be changed by heating followed by cooling under definite conditions to make them suitable for specific applications. Accordingly steel can be hardened to resist cutting action and prevent abrasion. Different heat treatment processes are carried out in temperature controlled furnaces and ovens.

Hardening: To perform hardening process, steel is heated to a temperature (800 degree C) above its critical range. It is held at this temperature for a considerable time and then allowed to cool by quenching in water, Oil or brine solution. On heating the above at high critical temp, the basic structure changes into austenite which contains considerable parts of ceAmentite. On rapid cooling this austenite change into martensite that imparts hardness in steel.

Tempering: Steel after hardening becomes brittle, develops non-visible micro-cracks and is strained due to residual stresses. These undesired symptoms are reduced by tempering the steel. This process involves reheating of the hardened steel to a certain temperature below lower critical temperature followed by a slow cooling rate.

Application:

Heat treatment not only increases the hardness but also increases the tensile strength and toughness.

Apparatus Required:

*
p<>{color:#000;}. Steel specimen

*
p<>{color:#000;}. Hardness tester

*
p<>{color:#000;}. Muffle furnace

*
p<>{color:#000;}. Quenching medium

Procedure:

*
p<>{color:#000;}. The hardness of the given steel specimen is found out using Rockwell hardness test.

*
p<>{color:#000;}. The specimen is then kept inside the furnace at a temperature of above 950ºC.

*
p<>{color:#000;}. It is held at that temperature for 1 hour in order to transform all ferrite into austenite.

*
p<>{color:#000;}. Then it is rapidly quenched in water so that the formation of marten site takes place.

*
p<>{color:#000;}. Again the hardness of hardened steel is noted from the Rockwell hardness test.

Tabulation:

table<>. <>. |<>/2.
p={color:#000;}.  

Sr. No

 

|<>/2. p={color:#000;}.  

Material |<>/2.
p={color:#000;}.  

Load in Kg |<>/2.
p={color:#000;}.  

Penetrator |<>/2.
p={color:#000;}.  

Scale |<>\2.
p={color:#000;}.  

Hardness | <>. |<>.
p={color:#000;}. Before hardening |<>.
p={color:#000;}. After hardening | <>. |<>.
p={color:#000;}.  

1.

 

|<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   | <>. |<>. p={color:#000;}.  

2.

 

|<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   | <>. |<>. p={color:#000;}.  

3.

 

|<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |<>. p={color:#000;}.   |

Result:

Hardness of given specimen

*
p<>{color:#000;}. Before hardening =

*
p<>{color:#000;}. After hardening =

Inferences:

Viva – Questions:

*
p<>{color:#000;}. Define Hardening?

*
p<>{color:#000;}. Define Tempering?

*
p<>{color:#000;}. Give the application of this test.

*
p<>{color:#000;}. Explain the procedure involved in this test.

Ex. No : MECHANICAL PROPERTIES FOR UNHARDENED OR

Date : HARDENED SPECIMEN

Objective:

To determine the hardening effect of the given steel specimen.

Aim:

To find hardness number and impact strength for unhardened, hardened specimen or Quenched and tempered specimen and compare mechanical properties.

Apparatus Required:

*
p<>{color:#000;}. Unhardened specimen, Hardened or Quenched and tempered specimen,

*
p<>{color:#000;}. muffle furnace,

*
p<>{color:#000;}. Rockwell testing machine,

*
p<>{color:#000;}. impact testing machine.

Procedure:

HARDENING: It is 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 considerable time to ensure thorough penetration of the temperature inside the component and allowed to cool by quenching in water, oil or brine solution.

Case (I) – For Unhardened specimen 1. Choose the indenter and load for given material. 2. Hold the indenter in indenter holder rigidly 3. Place the specimen on the anvil and raise the elevating screw by rotating the hand wheel up to the initial load. 4. Apply the major load gradually by pushing the lever and then release it as before. 5. Note down the readings in the dial for corresponding scale. 6. Take min 5 readings for each material.

Case (II) – For Hardened specimen 1. Keep the specimen in muffle furnace at temperature of 700˚ to 850˚ for 2 hours 2. The specimen is taken from muffle furnace and quenched in water or oil.3. Then above procedure is followed to test hardness

Case (III) – For Tempered specimen 1. Keep the specimen in muffle furnace at temperature of 650˚ for 2 hours 2. Allow the specimen for air cooling after taking from muffle furnace 3. Then same procedure is followed foe the specimen

Observation:

Rockwell hardness test:

Cases for hardness =

Cross sectional area=

Tabulation:

table<>. <>. |<>.
p<>{color:#000;}.  

|<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>/2. p(<>{color:#000;}. Load |<>. p={color:#000;}. Intender |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>\2. p<>{color:#000;}. RHN |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>/2. p={color:#000;}. S.No |<>/2. p={color:#000;}. Material |<>/2. p={color:#000;}. Temperature |<>/2. p={color:#000;}. Detail |<>/2. p<>{color:#000;}. scale |<>/2. p={color:#000;}. Trial |<>/2. p={color:#000;}. trail |<>. p<>{color:#000;}.   |<>/2. p={color:#000;}. Trail |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>/2. p<>{color:#000;}. (Kgf) |<>. p<>{color:#000;}.   |<>/2. p(<>{color:#000;}. Mean |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>/2. p={color:#000;}.   |<>. p<>{color:#000;}.   |<>/2. p)>{color:#000;}. 1 |<>/2. p>{color:#000;}. 2 |<>. p<>{color:#000;}.   |<>/2. p)>{color:#000;}. 3 |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p={color:#000;}. Deep |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}. 1 |<>. p={color:#000;}. casehardened |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p={color:#000;}. steel |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p={color:#000;}. Deep |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}. 2 |<>. p={color:#000;}. casehardened |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p={color:#000;}. steel |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}. 3 |<>. p={color:#000;}. Mild steel |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p={color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}. 4 |<>. p={color:#000;}. Mild steel |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |

CHARPY TEST

table<>. <>. |<>.
p<>{color:#000;}.  

|<>/2. p={color:#000;}. Material and |<>/2. p={color:#000;}. Energy |<>/2. p={color:#000;}. Cross-sectional area |<>. p={color:#000;}. Impact |<>. p<>{color:#000;}.   | <>. |<>/2. p={color:#000;}. S.No |<>/2. p={color:#000;}. strength(J/ |<>. p<>{color:#000;}.   | <>. |<>/2. p={color:#000;}. Condition |<>/2. p={color:#000;}. absorbed(Joules) |<>/2. p={color:#000;}. below the notch(mm) |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>/2. p={color:#000;}. mm) |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>/2. p={color:#000;}. 1 |<>. p={color:#000;}. Mild steel- |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>/2. p={color:#000;}. unhardened |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   | <>. |<>. p={color:#000;}. 2 |<>. p={color:#000;}. Quenched |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |<>. p<>{color:#000;}.   |

Result:

Thus the hardening – heat treatment process is carried out.

Inferences:

Ex. No : MICROSCOPIC EXAMINATION OF METAL SPECIMEN

Date :

Objective:

To learn and to gain experience in the preparation of metallographic specimens and to examine and analyse the microstructures of metals and metallic alloy.

Aim:

To study the microscopic structures of metal

Theory:

The properties of metals highly depend on their structures. The internal structures determine how materials perform under a given application. The branch of materials science dealing with microscopic examination of metals is called Metallography.

The most common method used to examine the structures of materials is optical technique. A specimen about 20mm on an edge is cut from the metal to be examined. In some cases where the subject is small or unhandy like razor blade, it is embedded in a plastic case. A mirror polish is produced on one face of the specimen by grinding on successively fine emery (sand) papers and polishing on revolving cloth wheels with fine abrasives such as diamond or alumina powder. To reveal the structural details such as grain boundaries, phases and inclusions this polished surface is etched with chemical solutions. The etchant attacks various parts of the specimen at different rates and reveals the structure. A metallographic microscope is used to examine the microstructure.

Application:

The effects of most industrial processes applied to metals to control their properties can be explained by studying their microstructures.

Apparatus Required:

*
p<>{color:#000;}. Metallurgical microscope

*
p<>{color:#000;}. Specimen

*
p<>{color:#000;}. Dry and wet polisher

*
p<>{color:#000;}. High grade emery sheet

*
p<>{color:#000;}. Etchant

Procedure:

*
p<>{color:#000;}. A part of metal is taken so as to represent the entire mass.

*
p<>{color:#000;}. It is cut and removed with saw or abrasive material.

*
p<>{color:#000;}. The specimen is first grinded for coarse surface.

*
p<>{color:#000;}. The metal is rubbed against emery paper for progressive finish.

*
p<>{color:#000;}. The metal is dipped into etchant for cleaning the surface.

*
p<>{color:#000;}. The etchant metal is kept under microscope to observe the structure.

Result:

The microscopic structure of given metal sample have been examined.

Inferences:

[* Viva- Questions: *]

*
p<>{color:#000;}. What is meant by microstructure?

*
p<>{color:#000;}. What is meant by Metallography?

*
p<>{color:#000;}. Give examples for alloys.

*
p<>{color:#000;}. What is the use of an etchant?

49

 


Strength of Materials Lab Manual

  • ISBN: 9781311563057
  • Author: keerthikumar92
  • Published: 2016-05-03 09:35:17
  • Words: 6566
Strength of Materials Lab Manual Strength of Materials Lab Manual