3RD SEM - MT LAB

Department of Industrial Engineering and Management, R.V. College of Engineering, Bangalore – 59.

Department of Industrial Engineering and Management

MATERIA IALTESTIN INGLAB R.V. College of Engineering, Bangalore – 59 MATERIALS TESTING LABORATORY SCHEME OF CONDUCT AND EVALUATION CLASS: III SEMESTER (New Scheme) YEAR: 2006

Sl. No 01 02 03 04 05 06 07 08 09 10 11 12

Expt. No. MT01 MT02 MT03 D01 MT04 MT05 MT06 MT06 D02 MT07 MT08 MT09 MT10 S01 S01 S02 D03

SUBJECT CODE: MEL37 A CLASS MARKS: 25

Title CYCLE – I Tension Test on Mild Steel Specimen Torsion Test on Mild Steel Specimen Impact Tests (IZOD and CHARPY) on Mild Steel Specimen NonNon-De Dest stru ruct ctiv ivee Test Testss – Demo Demons nstr trat atio ion n Rockwell hardness Test CYCLE – II Wear Test Doubl Doublee She Shear ar Test Test on on Mild Mild Stee Steell Specime Specimen n Fati Fatigu guee Te Test – de demons monsttrati ration on Compression Test on Mild Steel Specimen Brinell Hardness Test CYCLE – III Vickers hardness Test Bending Test on wood Prepar Preparat atio ion n of spec specim imen en for for met metall allogr ograp aphic hic exam examina inati tion. on. Micr Microst ostruc ructu ture re study study of the Engine Engineer ering ing mate materi rials als – identification Heat treatment of steel materials & study of their hardness hardness using their Rock-well testing machine--Demonstration

13

TEST TOTAL

KEY MT –Materials Testing Expt. S – Study Expt.

Material Testing lab Manual

D – Demonstration Expt.

Class No. of & Test Class Marks 01 01

20 20

01

20

01

20

01

10

01

20

01 01

20 20

01 01

10 20

01

10

01

10

01 13

50 250


Department of Industrial Engineering and Management

MATERIA IALTESTIN INGLAB R.V. College of Engineering, Bangalore – 59 MATERIALS TESTING LABORATORY SCHEME OF CONDUCT AND EVALUATION CLASS: III SEMESTER (New Scheme) YEAR: 2006

Sl. No 01 02 03 04 05 06 07 08 09 10 11 12

Expt. No. MT01 MT02 MT03 D01 MT04 MT05 MT06 MT06 D02 MT07 MT08 MT09 MT10 S01 S01 S02 D03

SUBJECT CODE: MEL37 A CLASS MARKS: 25

Title CYCLE – I Tension Test on Mild Steel Specimen Torsion Test on Mild Steel Specimen Impact Tests (IZOD and CHARPY) on Mild Steel Specimen NonNon-De Dest stru ruct ctiv ivee Test Testss – Demo Demons nstr trat atio ion n Rockwell hardness Test CYCLE – II Wear Test Doubl Doublee She Shear ar Test Test on on Mild Mild Stee Steell Specime Specimen n Fati Fatigu guee Te Test – de demons monsttrati ration on Compression Test on Mild Steel Specimen Brinell Hardness Test CYCLE – III Vickers hardness Test Bending Test on wood Prepar Preparat atio ion n of spec specim imen en for for met metall allogr ograp aphic hic exam examina inati tion. on. Micr Microst ostruc ructu ture re study study of the Engine Engineer ering ing mate materi rials als – identification Heat treatment of steel materials & study of their hardness hardness using their Rock-well testing machine--Demonstration

13

TEST TOTAL

KEY MT –Materials Testing Expt. S – Study Expt.


D – Demonstration Expt.

Class No. of & Test Class Marks 01 01

20 20

01

20

01

20

01

10

01

20

01 01

20 20

01 01

10 20

01

10

01

10

01 13

50 250


EVALUATION SCHEME:

CLASS MARKS (Reduced to 25) Proposed by: D.Venugopal setty. Shobha N S

= Class work total + Test Marks 10 Prepared by: H.M.Shadakshara

Approved by Prof.K.S.Badarinarayanaa Prof.K.S.Badarinarayan

SYLLABUS MATERIALS TESTING LABORATORY (Common to ME I IP I AU I IM I MA)

Sub Code MEL37 A/MEL47 A Hrs/Week 03 Total Hrs. 42

IA Marks 25 Exam Hours 03 Exam Marks 50

PART-A 1. Preparation of specimen for metallographic examination of engineering materials and study the microstructure of plain carbon steel, tool steel, gray C.I, SG iron, Brass, Bronze. 2. Heat treatment: Annealing normalizing hardening and tempering of steel & to study their Rock-well hardness (Demonstration only)

PART-B 3. Conduction of tensile, shear, compression, torsion and bending tests of a Mild Steel specimen using a Universal Testing Machine. 4. Conduction of Izod and Charpy tests on Mild Steel Specimen. 5. Experiment on Wear Study. 6. Brinell, Rockwell and Vicker's Hardness tests. 7; .Fatigue Test- (demonstration only). 8. Non-destructive test experiments - (demonstration only). (a). Ultrasonic flaw detector (b). Magnetic crack detector (c). Dye penetrant testing

Scheme of Examination: ONE question from part -A (Identification only) ONE question from part -B Viva-Voce


:

10 Marks

: :

30 Marks 10 Marks




INTRODUCTION: Materials constitute an important component of the curriculum of every branch of engineering and applied science. For fabrication of machines, manufacture of parts, building of plants and structures, and carrying out processes, the choice of the material is critical. An awareness of materials available to the characteristic material properties & us are desirable for efficient problem solving, decision-making, and development of advanced materials and functioning of an engineer. The need for materials literacy of engineers and technologists is now recognized all over the world. It is clear that an engineer should keep the materials scenario in mind while designing a component or machine. Otherwise his design may become redundant. For the efficient design of engineering products, problem solving, decision making and the overall efficient functioning of an engineer, an awareness of available materials, there potentials and limitations, and an understanding of there properties and behaviour or desirable. Every engineering material is known by its set of properties. A variety of tests are conducted in the Material Testing Laboratory to evaluate & compare the mechanical properties of different materials. The Mechanical Properties are: 1. 2. 3. 4. 5.

Stiffness Elastic Strength Yield Strength Ductility Malleability

6. Ultimate Tensile Strength 7. Fracture Strength 8. Stress 9. Strain 10. Toughness

These tests are classified into three categories:

1. Loading conditions • Static tests - Tension, compression, Torsion, Bending, Shear Tests • Dynamic tests–Impact tests- Charpy Test, Izod Test • Repeated loading - Fatigue test. • High Temperature tests - Creep test 2. Hardness Tests • Penetration Tests - Rockwell Hardness Test, Brinell Hardness Test, Vicker’s Hardness Test

3. Non- destructive Tests • Visual Inspection • Magnetic Particle inspection • Magnetic crack detector • Dye penetrate test


• • •

Radiography Ultrasonic test X-Ray test.


EXPERIMENT No. MT01

TENSION TEST ON DUCTILE MATERIAL AIM: - To determine the strength and several properties of ductile steel, to observe the behaviour of the material under load and to study the fracture and thus determine the following:

1. 2.

Yield strength Tensile strength

3. Ductility i. Percentage elongation ii. Percentage reduction in area 4. Modulus of elasticity (Graphical Method)

APPARATUS / INSTRUMENTS / EQUIPMENT USED: 1. 2. 3. 4.

Universal Testing machine Extensometer Vernier caliper scale

UNIVERSAL TESTING MACHINE

Equipment Description:UTM as name implies, are general purpose machines. They vary greatly in physical size, load capacity, versatility & sophistication. In its simplest form, a UTM system includes a load frame where the test is actually performed. The load frame must, of course, be rugged enough for the application. Some means of control over the load frame is necessary. This control can be as simple as hand wheel on a valve or as complex as a



computer to control the loading & unloading process and the rates at which these are done. Generally a recorder is used to record permanently the results of the tests. Grips or some other accessory are used to interphase between the sample being tested & the load frame itself. The action & use of the grips is often one of the most critical and least understood parts of the test. Each UTM is desired to have a maximum load capacity. Small units may have a load of few 100N or even less. The UTM can be used for: 1. Tensile test 2. Shearing test 3. Compression test 4. Bending test 5. Functions of i. Yield point ii. Elasticity Modulus, iii. Young's Modulus iv. Ultimate value v. Break value

PROCEDURE:1.

Determine the average cross-section of the given specimen. Scribe a line along the bar and with a centre punch lightly mark a 120 mm gauge length symmetrical with the length of the bar. 2. Firmly grip the upper end of the specimen in the fixed head of the testing machine using proper fixing devices or shackles. The specimen is placed such that the punch marks face the front of the machine 3. Firmly attach the extensometer to the specimen so that the axis coincides with that of the specimen. Adjust the testing machine and extensometer to read zero. Grip the lower end of the specimen taking care not to disturb the fixing of the extensometer. 4. Select suitable increments of load (between 200 and 500 kgs) to obtain at least 15 readings of strain within the proportional limit. Apply the load at a slow speed, taking simultaneous observations of load and strain without stopping the machine. The extensometer is used only till the yield point value is reached at which point the extensometer dial makes two complete revolutions. After this, the elongation is observed on the scale fixed to the machine frame. 5. Loading is continued till the failure of the specimen . Record the ultimate load and breaking load.

6.

Remove the broken specimen from the machine and observe the failure characteristics . Measure the dimension of the smallest section. Hold the broken parts together and measure the gauge length. 7. Plot a stress-strain diagram and mark the following on the graph: a. Upper yield point b. Lower yield point



c. Breaking stress d. Ultimate stress

8.

Calculate the slope of the graph (within the elastic limit), which is the Young’s modulus value of the given material.

R.V. COLLEGE OF ENGINEERING, BANGALORE-560059 DEPARTMENT OF INDUSTRIAL ENGG. AND MANAGEMENT

MATERIAL TESTING LABORATORY OBSERVATION / DATA SHEET Date: Lab : MT Lab

Name: Class: III Sem

Title of the Experiment:

USN: Expt.No:

TENSION TEST

OBSERVATIONS: Least count of extensometer =0.01mm Least count of Vernier caliper = 0.02mm

DETAILS OF SPECIMEN: Material : Mild steel Total length of specimen (L) :330mm Length between shoulders (l) :133mm Gauge length (l1) :120mm Diameter at the ends (D) :19mm Diameter of reduced section (d) :14mm Diameter of ruptured section (d1) :8.5mm Gauge length after fracture (l2) :15.5mm Shoulder

SKETCH OF THE SPECIMEN:

d

l

1

l L


D


Contd….. Signature of the staff in charge





USN: Expt.No:

TENSILE TEST

EXPERIMENTAL READINGS:

Sl. No 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Load (Kg) 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000

Extensometer Reading Left 3 6 7 10 11.5 13 15 17 19 20.5 22.5


Right

Scale reading (mm)

0 0 1 3 4.5 6 8 9.5 11 13 16.5

Remarks

Yield point 1.5 3 4.5


15 16 17 18 19 20

7500 8000 8500 8000 6500 6000

6.5 9.5 13 35 39.5 40

Ultimate point Breaking point

Signature of the staff in charge R.V. COLLEGE OF ENGINEERING, BANGALORE-560059 DEPARTMENT OF INDUSTRIAL ENGG. AND MANAGEMENT




TENSILE TEST

Tabulated results: Sl. Load Extensometer Reading No (mm) Left Right Average 1 2 3 4 5 6 7 8 9 10 11

4905 9810 14715 19620 24525 29430 34335 39240 44145 49050 53955

12 13 14 15 16

58860 63765 68670 73575 78480

0.03 0.06 0.07 0.1 0.115 0.13 0.15 0.17 0.19 0.205 0.205

USN: Expt.No:

0 0 0.01 0.03 0.045 0.06 0.08 0.095 0.11 0.13 0.165


Scale Reading (mm)

0.015 0.03 0.04 0.065 0.08 0.095 0.115 0.1325 0.15 0.1675 0.195 1.5 3 4.5 6.5 9.5

Stress (N/mm2)

Strain

31.86 63.73 95.59 127.46 159.32 191.19 223.05 254.92 286.78 318.65 350.51

0.00013 0.00025 0.00033 0.00054 0.00067 0.00079 0.00096 0.00110 0.00125 0.00140 0.00163

382.38 414.25 446.11 477.97 509.85

0.0125 0.025 0.0375 0.0542 0.07916

Remarks

Yield point


17

83385

13

541.70

0.1083

18 19 20 21 22

78480 73575 68670 63765 58860

35 36 37.5 39.5 40

509.85 477.97 466.11 414.25 382.38

0.2916 0.3083 0.3167 0.329 0.3334

Ultimate point

Breaking Point

Signature of the staff in charge

Stress-Strain Diagram 600 500

) 2 m 400 m / N ( 300 s s e r 200 t s 100 0

3 3 3 6 7 9 6 2 5 6 3 5 2 3 3 9 1 2 5 4 0 8 0 8 3 2 0 0 0 0 0 0 0 0 1 0 1 0 . 0 . 0 1 3 0 . . . 0 0 0 0 0 0 0 0 0 0 0 . 0 . 0 . 0 . 0 . 0 .

strain

SPECIMEN CALCULATION: For Sl. No.3 1.Applied load , P = 1500 x 9.81 =14715

N

2.Area of cross section before fracture , A= π d² / 4 = 3.Area of cross section after fracture =

π

d12 / 4 =

π

π

x (14)2 /4 = 153.93 mm2

x (8.5)2 /4 = 56.745 mm2

4.Applied stress = P / A = Load/ Initial area of cross section = 14715/153093 = 95.595 N/mm2 = 77.18 X106 N/m2



5. Strain = Change in length / Original length = 0.035/120= 0.000333 6. % Elongation = Change in gauge length X100 / Original gauge length = (L2 -L1 )X 100 / L1 = (155-120)X100/120 = 29.17% 7. % Reduction in area = (Original area – Area after fracture)X100 / Original area = (153.93 –56.745 )X100 / 153.93 = 63.135% 8.Yield strength = Load at yield point / Initial area of cross section = 5300*9.81/153.93 = 337.77 N/mm2 =3.377 X108 N/m2 9. Tensile strength = Maximum load / Initial area of cross section = 83385/153.93= 541.7 N/mm2 = 5.417 X108N/m2 10. Breaking strength = Load at break point / Initial area of cross section = 58860/153.93=382.382 N/mm2 =3.823 X108 N/m2 11.Modulus of elasticity (Graphical), E = Slope of Graph = 2.4 X1011N/m2

RESULT :Experimental results are as follows: Percentage elongation = 29.166% Percentage reduction in area = 63.135% Yield strength = 3.377 X108 N/m2 Tensile strength = 5.417 X108 N/m2 Breaking strength = 3.823 X108 N/m2 Modulus of elasticity (Graphical), E = 2.4 X1011 N/m2


π


EXPERIMENT No. MT02

TORSION TEST AIM: - To determine the behaviour of ductile steel when subjected to torsion, and obtain the following tensional properties: • Modulus of rigidity • Maximum Shear strength of the material

APPARATUS/EQUIPMENT/INSTRUMENTS USED

• • •

Torsion testing machine, Torsion Shackles, Vernier Calipers

TORSION TESTING MACHINE

Equipment description: Torsion Testing Machine is designed for conducting Torsion and Twist on various metal wires, tubes, sheet materials. This Machine applies a torque on the specimen held in its chuck and measures the twist. Suitable for Torsion and Twist test on various metal rods and flats. Torque measured by pendulum dynamometer system. Geared motor to apply torque to specimen through gear box. Set of jaws to accommodate different size and diameter of test specimens provided.







USN: Expt.No:

TORSION TEST

OBSERVATIONS: Least count of the Vernier caliper =0.01mm Least count of the Torque Indicator r=60Kg-cm Least count Twist Indicator =0.5°

TORQUE AND TWIST READINGS: Sl.No.

TORQUE Kg-Cm (x 60)

Twist (Degrees) 1

2

1.

0

10

0

2.

3

20

0.25

3.

12

30

0.75

4.

14

40

1.00

5.

15

50

1.25

6.

16

60

1.25

7.

17

70

1.25




PROCEDURE:1. Measure the dimensions of the specimen using Vernier caliper 2. Fix the specimen between the shackles. The axis of the specimen should coincide with the axis of the shackles 3. Rotate the wheel very slowly to give a twist of θ1=10° 4. Note down the corresponding torque developed (kg-cm), T and the angle of twist, θ2 from the indicators. 5. Increase the twist θ1 in steps of 10° till the failure of the specimen. Note the corresponding values of θ2 and T.

6. Calculate the effective twist, θ = θ1 ~ θ2 7. Calculate shear strength using formula,τ = T x R / J 8. Plot a graph between τ and θ. 9. Calculate rigidity modulus from the slope, G = Slope x L / R

TABULATION: Sl No

Torque (division)

Torque (N-m)

° 1

1 2 3 4 5 6

0 3 12 14 15 16

0 17.658 70.632 82.404 88.290 94.176

10 20 30 40 50 60

TWIST (Degree) ° = 1° ~ ° 2

0 0.025 0.75 1.00 1.25 1.25

° 2

10.00 19.75 29.25 39.00 48.75 58.75

TWIST, (radians) 0.1745 0.3447 0.5105 0.6807 0.8508 1.0254

600

) m / 500 N

2

8

0 400 1 x ( s 300 s e r t S 200 r a e 100 h S

0

0.1745

0.3447

0.5105

0.6807

Twist (Radians)


0.8508

1.0254

Shear Stress, (x108N/m2) 0 89.93 359.72 419.68 449.66 479.63


SPECIMEN CALCULATION (for sl.no.2) 1. Torque division = 3 Torque (T) = 3x60 Kg- Cm T = 3x60x9.81/100 = 17.658 N – m

2. Twist, θ = θ 1 ~ θ 2= 20 ~ 0.25 = 19.75° = 19.75 x π /180 = 0.3447 radians 3. Diameter (D) = 10 mm, Polar moment of inertia, J = π D4 / 32 = π (10)4 / 32 = 981.75 mm4 = 981.75 x10-12 m4 4. Shear stress, τ = T x R /J = 17.658 x (5/1000)/ 981.75 X10-12

= 8.993 x107 N/m2

5. Maximum shear stress, τmax = 5.0961 x108 N/m2 6.

1. Modulus of rigidity or Polar Moment of Inertia, G = Slope x L / R N/m2

=(1.56x103x130)/5=4.056x10 9 N/m2

RESULTS: 1. Maximum shear stress 2. Modulus of rigidity


= 5.0961 x108 N/m2 = 4.056 x 109 N/m2


EXPERIMENT No. MT03

IMPACT TEST – IZOD AND CHARPY AIM:- To determine the relative impact resistance of a given specimen by conducting the IZOD and Charpy tests.

APPARATUS / INSTRUMENTS / EQUIPMENT USED:-

• • • •

Impact testing machine, Vernier caliper, Centerpiece or setting gauge, Allen key.

IMPACT- TESTING MACHINE

Theory: Impact loading differs from quasi-static loading. In that a load is applied over a very short time instead of being introduced gradually at some constant rate. This causes significant changes in the observed material properties from those associated with normal static tests. In the case of impact loading the effects measured are of a dynamic nature, with vibration and possibly fracture being observed. The Notched Bar test, where specimens are subjected to axial, bending or torsion loads using specialized testing machines. The technique involves swinging a weight of W from a certain specified height h to strike the notched specimen, breaking it as it passes through, and arriving at a



height h', lower than the initial position of the pendulum. The energy expended in rupturing the specimen can be described using the equation

U = W (h-h') Where, W= Weight

h & h’= Specified height





USN: Expt.No:

IMPACT TEST--- IZOD

OBSERVATIONS: Least count of Vernier Calliper:0.02mm Least count of the Dial on the Impact testing machine = 0.1 kg-m

EXPERIMENTAL READINGS: Dial Reading (Kg-m) Material

Dimensions of the specimen

Notch angle

Initial (E1)

Final Energy (E2) consumed (Kg-m)

Mild Steel

Length = 27.0mm. Diameter =12mm Dia. of notch=9mm Depth of notch =1.5mm Width of notch = 3.0mm

45°

0

1.5

1.5

Cast Iron

Length = 25.0mm Diameter = 11.0mm Dia .of notch = 7.84mm Depth of notch=1.58mm Width of notch = 3.0mm

45°

0

0.1

0.1






PROCEDURE: 1. Raise the pendulum and fix it to the pendulum notch. Place a thick wooden plank on the stand below the pendulum pipe. 2. Keep the reading pointer at 17 kg-m on the inner scale. Release the Izod lever and allow the pendulum to swing freely. Arrest the movement of the pendulum by using the pendulum brake. 3. Record the indicator reading, which will give the energy lost due to friction and air drag. See if the pointer comes to ‘o’ (Zero) reading. If not, there will be on error (in calibration of the instrument). Note that as initial reading. Again raise the pendulum and fix it onto the notch. 4. Measure the lateral dimension of the specimen at the full section and at the notch and check whether the dimensions conform to the given standard, 5. Now fix the Izod specimen inside the damping device, hold the specimen in hand vertically such that the half of the V-notch is just above the horizontal surface of the clamping device (cantilever beam position) and the notch is facing the pendulum. 6. Now insert the setting gauge such that the pointer edge of the setting gauge correctly fits inside the V-groove. Simultaneously tighten the clamping screw using allen key and check that there is no movement of the specimen. 7. After ascertaining that, there will be nobody in the range of swinging the pendulum.

8. Operate the Izod lever. Now the pendulum will swing freely and the specimen will be smashed. Care must be taken to see that proper range is selected on the indicator (The circular opening in the dial should be fully-3/4th red and partly black) 9. Stop the swinging pendulum by applying the pendulum brake. 10. Note the reading on the dial corresponding to the pointer.

11. Calculate the difference between final and initial readings. This value gives the impact energy consumed or lost in breaking the specimen.



TABULATION AND CALCULATION:Material

Dial Reading

Energy consumed (E2- E1) (Kgm)

Energy Consumed (E2- E1) , J

Initial E1 (Kg-m)

Final E2 (Kg-m)

Mild Steel

0

1.5

1.5

14.715

Cast Iron

0

0.1

0.1

0.981

SPECIMEN CALCULATION (For Mild Steel):-

Actual energy absorbed by the specimen during fracture = Energy recorded on the dial indicator with specimen in position - Energy recorded on the dial indicator without specimen in position. = 1.5- 0 = 1.5 Kg-m = 1.5x9.81 = 14.715 J

RESULTS:The actual energy absorbed by the specimens is as follows: -

1. Mild steel = 14.715 J 2.Castiron = 0.981J









USN: Expt.No:

IMPACT TEST---CHARPY

OBSERVATIONS: Least count of Vernier Calliper:0.02mm Least count of the Dial on the Impact testing machine =0.1Kgm

EXPERIMENTAL READINGS:

Material

Dimensions of the specimen

Notch angle

Dial Reading (Kg-m) Initial (E1)

Final (E2)

Energy consumed

Brass

Length = 60 mm Breadth = 10 mm Width of the notch=10mm Depth of notch=02 mm

900

0

1.05

1.05

Mild Steel

Length = 56.20 mm Breadth = 9.76 mm Width of the notch=10mm Depth of notch=02 mm

900

0

3.8

3.8




RESULT : DIMENSIONS OF SPECIMEN BEFORE TESTING SL. NO.

PARAMETERS

MATERIALS BRASS MILD STEEL

1

Length of the specimen (mm)

56.20

55.20

2 3

Breadth of the specimen (mm) Thickness of the specimen (mm)

9.76 9.72

9.72 9.64

SPECIMEN CALCULATION BRASS Actual energy absorbed by specimen during fracture = Energy recorded on the dial indicator with specimen in position - Energy recorded on the dial indicator without specimen in position = 1.05-0 = 1.05 kg-m = 1.05x9.81 = 10.30 N-m = 8.829 J

RESULTS: The actual energy absorbed by the different specimens are as follows:Brass: - 10.3 J Mild steal: -37.27 J



EXPERIMENT No. D01

NON -DESTRUCTIVE TESTS INTRODUCTION: A Non - destructive test is an examination of a component in any manner which will not impair its future use. Although non-destructive test do not provide a direct measurement of mechanical properties, but they are very useful in revealing defects in components which could impair their performance when put in service. Non –destructive tests make components more reliable, safe and economical.

ULTRASONIC TEST AIM: To study the ultrasonic flaw detector and to determine the location of the interior crack or cavity in the given specimen.

APPARATUS: Ultrasonic flaw detector. THEORY: Ultrasonic flaw detector is a device, which is used to detect internal discontinuities in the material by nondestructive means. It makes use of phenomenon of back reflection (echo) of waves by surfaces. When ultrasonic waves are made to pass through the test material, portion of the sound is immediately reflected from the surface at which they enter as a very large echo. Part of the sound will continue on into the test material, until it is partially reflected from the back surface as a second echo. If there is a discontinuity in the material, a portion of the sound will be reflected from the discontinuity and will return to the receiver as a separate echo between the echoes received from the front and back surface. The signals received are shown on a cathode ray tube, which also has a time base connected to it, so that the position of the signal on the screen gives an indication of the distance between the crystal generator and the surface from which the echo originates. Sound waves oscillating with a frequency greater than 20,000 cps are inaudible and are known as “ultrasound”. High frequency sound is produced by a piezoelectric crystal, which is electrically pulsed and then vibrates at its own natural frequency. In order to transmit the sound waves from the crystal to the metal, it is necessary to provide a liquid couplant. This is accomplished by using a film of oil between the crystal and the test piece. After the crystal has given off its short burst of sound waves, it stops vibrating and listens for the returning echoes, i.e., one crystal probe is used to send and receive the sound. This cycle of transmitting and then receiving is repeated at an adjustable rate from 100 to 1000 times per second. Returning echoes on the CRT causes short vertical spikes called pips. These are spaced along the baseline according to their time of receipt. Since the sound travels through the material at a constant speed, the spacing of the pips can be considered as indicating thickness. Selecting and expanding full screen size of the CRT can eliminate unwanted echoes caused by reverberations with the test piece.



PROCEDURE: 1. Clean the surface of the test piece. 2. Place the probe against the surface of test piece using thin oil film. 3. Switch on the power supply of the ultrasonic wave generator. 4. Adjust the number of cycles of transmitting and receiving the signals to the desired value. 5. Select the segment of time, which contain the echo pips. 6. Observe the echo from the cavity if any on the CRT and measure the relative distances of pips on the time axis. Let A = Time elapsed between the pips of front surface echo and bottom surface echo (sec) B = Time elapsed between the pips of front surface echo and cavity surface echo (sec) H = Thickness of test specimen (mm) Location of the crack from the front surface x = (B/A)x h

ADVANTAGES: 1. It is a fast, reliable method of non destructive inspection 2. It is a very sensitive method. 3. The minimum flow size which can be detected is equal to about 0.1% of the distance from the probe to the defect. 4. Big castings can be systematically scanned for initial detection of major defects. 5. Ultrasonic inspection involves low cost and high speed of operation. 6. The sensitivity of ultrasonic flow detection is extremely high, being at a maximum when using waves of highest frequency.

LIMITATIONS: 1. Ultrasonic inspection is sensitive to surface roughness since cost surfaces are usually rough, some preliminary machining an castings will be required. 2. In complex castings the interpretation of the oscillographic trace may not be easy. Waves reflected from corners or other surfaces may give a false indication of defects.

APPLICATIONS: 1. Inspection of large castings and forgings, for internal soundness, before carrying out expensive machining operations 2. Inspection of moving strip or plate (for laminations) as regards its thickness. 3. Routine inspection of locomotive axles and wheel pins for fatigue cracks. 4. Inspection of rails for bolt-hole breaks without dismantling railed assemblies.



MAGNETIC PARTICLE TEST AIM: To detect the surface or subsurface crack of the given ferromagnetic material. APPARATUS: Magnetic field generator and ferromagnetic powder. Magnetic particles

U-Horse Magnet

THEORY: The magnetic particle method of inspection is aofprocedure used to determine the Location Crack presence of defects at or near the surface of the ferromagnetic objects. This method consists of placing fine ferromagnetic particles on the surface. The particles can be applied either dry or in a liquid carrier such as water or kerosene. When the part is magnetized with a magnetic field, a discontinuity (defects) on the surface causes the particles to gather visibly around it. Thus, the defects become a magnet due to the principle of flux leakage where magnetic field lines are interrupted by the defect and collect the ferromagnetic particles. The collected particles generally take the shape and size of the defects. Sub surface defects can also be detected by this method, provided they are not deep. The ferromagnetic particles may be colored with pigments for better visibility on the metal surfaces. The magnetic fields can be generated either with direct current or alternating current, using yokes, bars and coils. The equipment may be portable or stationery. Procedure: 1. Clean the surface of the test specimen to remove scales, oil and grease. 2. Apply a thin layer of ferromagnetic particles over the surface to be tested. 3. Magnetize the test piece. 4. Observe the shape and size of the magnetic particles collected, which is the shape and size of the defect.

VISUAL INSPECTION Defects like surface cracks, tears, blowholes, metal penetration, rattails and buckles, swells, shifts, surface roughness and shrinkage are easily located by visual inspection. It is carried out with the marked eye or using a magnifying glass. This method is the simplest, fastest and most commonly employed, but requires greater skill on the part of the inspector to locate and identify different manufacturing defects. The inspector identifies the casting defects and assigns their cause to some foundry operation or raw materials so that corrective measures can be employed. Visual inspection ensures that none of the features of a casting has been omitted or malformed by moulding errors short running or mistakes in fitting.



LIQUID PENETRANT TEST AIM: To detect the surface defects by penetrant test. APPARATUS: Penetrant, developer and ultraviolet light source. THEORY: In the liquid penetrant test, liquids are applied to the surface of the part and allowed to penetrate into surface openings, cracks, seams and porosity. Two commonly known types of liquid penetrants are:

(a)

Fluorescent Penetrants which fluoresce under ultraviolet light, and

(b) surface.

Visible penetrant using dyes, usually red if which appear as bright outlines on the

The test piece is coated or socked in a liquid penetrant and the surplus coating is wiped off. After a short time, a developing agent is added to allow the penetrant to seep back to the surface (due to capillary action) and spread to the edges of openings. The surface is then inspected for defects, either visually in the case of dye-penetrants or under ultraviolet light for fluorescent penetrant. The developer includes dry powders, aqueous liquid and non-aqueous liquid. This method is capable of detecting variety of surface defects and is used extensively.

PROCEDURE: 1. Clean the test piece surface to remove scales, oil and grease. 2. Immerse the test piece in the selected penetrant and hold it for some time. 3. Remove the excess penetrant on the test piece surface. 4. Apply the developer on the surface of the test piece. 5. Examine the surface of the test piece under appropriate viewing conditions. 6. Clean the surface to prevent corrosion, etc.

OTHER NON-DESTRUCTIVE TESTS 1. Hammer Test 2. Radiography Test X- Ray radiography Gamma-ray radiography 3. Testing for metal composition -Wet analysis - Spectroscopy - Spot test techniques.

EXPERIMENT No. MT04

ROCKWELL HARDNESS TEST Material Testing lab Manual


AIM:- To determine the Rockwell hardness number of the given specimen. APPARATUS / INSTRUMENTS / EQUIPMENT USED:-

• •

Rockwell Hardness tester Indentors

ROCKWELL HARDNESS TESTER

Equipment Description: Rockwell HTM impacts a standard load on a steel ball or diamond indenter. Rockwell hardness test determines the hardness of ceramic substrates. The most common method of calculating hardness of plastics such as nylon, polycarbonate, polystyrene, and acetal is done by Rockwell hardness test. This test is also used for measuring the resistance of the plastic to indentation. The dial gauge is used to calculate the difference in depth produced by two different forces. The load applied, indenter diameter and the indentation depth can be measured using Rockwell hardness value.






USN: Expt.No:

Title of the Experiment: ROCKWELL HARDNESS TEST

OBSERVATIONS AND TABULATION SL.NO

Material

Scale

Load(Kg)

Indenter

1 2 3 4 5

Mild steel Cast Iron Brass Copper Aluminium

C C B B B

150 150 100 100 100

Cone(120°) Cone(120°) Ball (1/16th Ball (1/16th Ball (1/16th

Rockwell Hardness Number Trail 1 Trail 2 Trail 3 107 93 48 91 52

107 94 51 95 54

108 93 46 101 52




SELECTION OF LOAD AND INDENTOR Scale Symbol

Major Load (Kg)

Indentor

Application

A

60

Cone

Cemented carbide, thin steel, hardened steel.

B

100

(1/16)” Ball

Copper alloys, Soft Steels, Aluminum Alloys, Malleable Iron

C

150

Cone

Steel, Hard cast Iron, Paralyte malleable Iron, Deep case hardened steel.

PROCEDURE 1. Place the specimen on the anvil. 2. Select the load and indentor combination based on specimen material. 3. Raise the anvil until the specimen comes in contact with the indentor. Continue to raise the anvil slowly till the pilot lamp goes off. This indicates that the minor load of 10 kg is acting on the indentor. 4. Actuate the lever to apply the major load. 5. Give at least 10 seconds after the lever comes to rest position. 6. Read the position of the pointer on the corresponding scale of the dial, which gives the Rockwell hardness number. 7. Make three tests on each specimen. 8. Calculate average Rockwell hardness number. 9. Plot the bar chart separately for B-Scale and C-Scale



TABULATION AND CALCULATIONS:SL. NO

Material

Scale

Load(Kg)

Indenter

1 2

Mild steel Cast Iron

C C

150 150

3

Brass

B

100

Cone(120°) Cone(120°) Ball dia (1/16th of an inch) Ball dia (1/16th of an inch) Ball dia(1/16th of an inch)

4

5

Copper

Aluminium

B

100

B

100

Rockwell Hardness Number Trial Trial 2 Trial 3 Avg.RHN 1

SPECIMEN CALCULATION:Material : BRASS Scale : B-Scale Indentor = 1/16” Ball Indentor Major Load Applied = 100 Kgs Rockwell Number for trail 1, RHN1 = 48 Rockwell Number for trail 2, RHN2 = 51 Rockwell Number for trail 3, RHN3 = 46 Average Rockwell Number = (RHN1+RHN2+ RHN3) / 3 = (48+51+46) / 3 = 48.33 Kg/cm2

RESULTS:MATERIAL

ROCKWELL HARDNESS NUMBER

Cast Iron Mild Steel Brass

93.33 107.33 48.33


107 93

107 94

108 93

107.33 93.33

48

51

46

48.33

91

95 101

95.66

52

52.66

52

54


Copper Aluminium

95.66 52.66

C Scale 110

107.33

. o N 105 s s e n 100 d r a H l l 95 e w k 90 c o R

93.33

85 Cast Iron

Mild Steel

Materials

B Scale

120

. o N 100 s s e 80 n d r a 60 H l l e 40 w k c 20 o R

95.66

52.66

48.33

0 Brass

Copper Materials


Aluminium


EXPERIMENT No. MT06

DOUBLE SHEAR TEST AIM:- To conduct a Double shear test on different materials and obtain their shear strengths. APPARATUS / EQUIPMENT / INSTRUMENTS USED:• Universal testing machine, • Vernier calipers, • Double shear shackles.

UNIVERSAL TESTING MACHINE

DOUBLE SHEAR SHACKLES AND SPECIMEN:







USN: Expt.No:

DOUBLE SHEAR TEST

OBSERVATIONS: Least count of vernier caliper =0.02mm

TABULATION Sl. No.

MATERIAL

DIAMETER (mm)

Failure Load (Kg)

1 2

Brass Mild Steel

7.7 7.7

3200 4300




PRINCIPLE: Shear stress is caused by forces which act parallel to in area if cross-section and tend to produce sliding of one portion past another portion as shown in figure below:

P

If the force is resisted by failure through one plane and single area, then the material is said to be in single shear. In single shear, failure load

‫=ح‬

area of cross section

Where,

=

P A

=

P D π

2

4

=

4 P D π

2

N / m

2

D - initial diameter of the specimen. P - failure load. P

P

If 2 areas resist the fracture, then the area is said to be in double shear. Failure Load

τ

=

2 × Area of cross section

2 P

P =

2 A

=

π D

2

N / m

2

For conduction shear test, a suitable steel shackle may be fabricated based upon fork and eye plate principle the specimen is inserted as a connecting pin in the bush housing between the shackles; the fork plates of the shackle held rigidly together by bolts for avoiding any bending tendency of the specimen under high loads, and is tested in double shear. 1. The diameter of the specimen is measured using vernier calipers and the area of cross section of the specimen is calculated. 2. The specimen is than inserted inside the shear shackles & is placed inside the shear center plate. 3. The entire assembly is then placed on the lower cross slide of the universal testing machine.



4. The intermediate cross slide is then moved down till it makes contact with the top of the centre plate, through which the load is applied on the specimen. 5. The machine is started and the load is applied gradually till the specimen fails. At this point note down the load and the corresponding dial gauge reading.

OBSERVATION: Sl. MATERIAL No. 1 2

DIAMETER (mm)

Failure Load (Kg)

7.7 7.7

3200 4300

Brass Mild Steel

CALCULATION OF DOUBLE SHEAR STRENGTH MILD STEEL Area of cross section, 2 ( 7.7 ) 2 π d = π × A = 4 4

= 46.566mm 2 = 46.566 × 10 -6 m 2

Double strength, Failure Load

τ =


=

4300 × 9.81

(2

× 46.566 × 10

−6

)

=

6

452.937 × 10 N / m

2

BRASS 2

Area of cross section,

A =

π d

4

= π ×

( 7.7 ) 2 4

= 46.566mm 2 = 46.566 × 10 -6 m 2

Double strength, Failure Load

τ =


=

3200 × 9.81

(2

× 46.566 × 10

−6

)

=

RESULT: SL.N0

MATERIAL

1 2

MILD STEEL BRASS

DOUBLE SHEAR STRENGTH 452.937 X106 N/m2 337.0699 X106 N/m2

EXPERIMENT No. D02 Material Testing lab Manual

6

337.069 × 10 N / m

2


FATIGUE TEST AIM: To determine the fatigue limit and the fatigue strength. APPARATUS: Fatigue testing machine and micrometer caliper. THEORY: Failure due to repeatedly applied load is known as fatigue. The physical effect of a repeated load on a material is different from the static load, failure always being brittle fracture regardless of whether the material is brittle or ductile. Mostly fatigue failure occurs at stress well below the static strength of the material. If the applied load changes from any magnitude in one direction to the same magnitude in the opposite direction, the loading is termed completely reversed, where as if the load changes from one magnitude to another (the direction does not necessarily change), the load is said to be fluctuating load. Fatigue testing machine: In the simplest type of machine for fatigue testing, the load applied is of bending type. The test specimen may be of simply supported beam or a cantilever. R.R.Moore rotating beam type machine for a simply supported beam.A specimen of circular cross-section is held at its ends in special holders and loaded through two bearings equidistant from the center of the span. Equal loads on these bearings are applied by means of weights that produce a uniform bending moment in the specimen between the loaded bearings. A motor rotates the specimen. Since the upper fibers of the rotating beam are always in compression while the lower fibers are in tension, it is apparent that a complete cycle of reversed stress in all fibers of the beam is produced during each revolution. A revolution counter is used to find the number of cycles the specimen is repeatedly subjected to the load. For simply supported beam, maximum bending moment is at the center. The testing techniques are subjected to a series of identical specimens to loads of different magnitudes and note the number of cycles N of stress (or load) necessary to fracture the specimen. The data are plotted on a semi logarithmic paper, the stress S being plotted to a linear scale and the number of cycles N to a logarithmic scale.This is known as stress-cycle (S-N) diagram and the fatigue limit can be, determined from the diagram. Fatigue limit or endurance limit is the stress below, which a material can be, stressed cyclically an indefinitely large number of times without failure. The fatigue strength is the stress at which a metal fails by fatigue after a certain number of cycles. Specimens: All specimens should be taken from the same rod, each specimen should receive same kind of machining and heat treatment. The specimens for tests have no sharp stress raisers. The surface of the specimen is polished. Fracture appearance: Under repeated loading, a small crack forms in a region of high-localized stress, and a very high stress concentration accompanies the crack. As the load fluctuates, the crack opens and closes and progresses across the section. Frequently this crack propagation continues until there is in sufficient cross section left to carry the load and the member ruptures, the failure being fatigue failure. Therefore fractured surface shows two surfaces of distinctly different appearance.

1.

A smooth surface where the crack has spread slowly and the walls of the crack are polished



by repeated opening and closing. This surface usually shows characteristic of beach or clamshell marking. 2. A crystalline or fibrous surface where sudden failure occurred.

PROCEDURE: 1.

Measure the diameter d and the length L of the specimen.

2.

Fasten the specimen in the chucks of the testing machine.

3.

Set the maximum load. Set the counter to zero, and start the machine.

4.

Note the number of cycles N the specimen experiences before fracture.

5. Repeat the above test on the other specimens with gradually reduced loads. Draw the S-N diagram and obtain the endurance limit.



EXPERIMENT No. MT10 BENDING TEST AIM:- To conduct the bending test on the given material and there by determine the following: i. ii. iii. iv.

Stiffness Maximum bending moment Maximum bending stress at failure Modulus of elasticity

APPARATUS/EQUIPMENT/INSTRUMENTS USED • • • •

Universal Testing Machine Cathetometer Bending test attachment Former (acting as a knife edge to apply a concentrated load at the center of the specimen)

Cathetometer

The Cathetometer can measure with great precision the difference in level between two points whether or not they lie on the same vertical line. This instrument is made of a robust graduated vertical copper rod, more than a meter long. The rod turns on its axis and is mounted on a tripod with leveling screws. Attached to the rod are two horizontal collimeter telescopes attached to tracks which have a ruler and a pointer and which can slide along the rod. The instrument's case has the form of a right angle prism and rests on a strong metallic tripod. Less sophisticated cathetometers have one telescope with which the two points are collimated successively.



If two points, A and B, are collimated through the telescopes and the positions assumed by the two pointers are read on the scale, the difference between gives the distance between the horizontal planes of the two points. The collimation is effected by creating a coincidence between the image of the point (observable through the telescopes) and the center of the instrument's optical grid. The degree of precision obtained in measurement depends on the approximation obtained with the ruler and on the care with which the graduated rod is put vertical and the telescopes horizontal.







USN: Expt.No:

BENDING TEST

OBSERVATIONS Least count of vernier caliper = 0.02mm Least of cathetometer = 0.01mm

MATERIAL SPECIFICATIONS Length (l) mm Breadth (b) mm Thickness (d) mm

400 46 71

LOAD AND DEFLECTION READINGS Cathetometer initial reading = 17.272mm

Sl. No

Load (Kg)

1 2 3 4 5 6 7 8 9

0 300 600 900 1200 1500 1800 2100 2400

MATERIAL: MATTI WOOD Final Reading Final-Initial Reading 17.272 17.403 17.413 17.413 17.541 17.788 18.007 18.126 Breaking point

0 0.131 0.141 0.141 0.269 0.516 0.735 0.854


PRINCIPLE



A bending test can be performed on an actual being cross -section by using a 3-point loading system. The bending fixture is supported on the platform of the hydraulic cylinder of the UTM , The loading edge is held in the middle or intermediate crosshead. At a particular load , the deflection at the centre of the beam is determined using a dial gauge. The deflection at the centre of the beam is given by ∆ = W L 3 / (48 E I ) E = W L 3 / (48 ∆ I ) Stiffness , W/∆ = 48 EI/ L3 This is derived from the bending equation , M/I = σ/ y = E/R The beam with simply supported at two ends and loaded at the centre is as shown in figure W

L/2 W/2

L/2 W/2

For the above beam Maximum bending moment = WL/4 Since cross section of beam is rectangle with dimensions b&d, I = bd3 / 12 Therefore, s = 3WL / (2d3) N/m2 Where L = Length of the specimen in meters, b = breadth of the specimen in meters , d = depth or thickness of the specimen in meters , W= Applied load in N



PROCEDURE 1. The bending test attachment is fitted in the universal testing machine and the specimen is fixed in it using the special shackles provided for the purpose. 2. The breadth and thickness of the specimen are measured using vernier caliper and its length determined after fixing 3. The loading former is fixed in the intermediate cross head firmly and is adjusted till it just touches the specimen. 4. Record the initial cathetometer reading . 5. Load is applied, and after every 300 Kg, the cathetometer is focused on the wood specimen and the corresponding reading recorded. 6. Loading is continued till the specimen fails 7. Calculations are made. 8. A graph of load against deflection is plotted.

Principal features of supporting and loading devices for BEAM TESTS indicating provision for longitudinal and lateral rotational adjustment at support

DEFLECTION MEASURING DEVICES



BENDING OF A BEAM

MATERIAL: TEAK WOOD BENDING MOMENT CALCULATIONS SL. NO. 1 2 3 4 5 6 7 8 9 10 11

LOAD W (X9.81 N) 0 300 600 900 1200 1500 1800 2100 2400 2700 3000

DEFLECTION READING 162.60 162.60 162.60 162.60 162.60 162.60 162.60 162.60 162.60 162.60 162.60

162.60 163.53 164.03 164.42 165.16 165.34 165.50 166.00 166.64 166.80 167.32

(mm)

Bending moment (N-m)

0 0.93 1.43 1.92 2.56 2.74 2.90 3.40 4.04 4.20 4.72

0 286.94 573.89 860.83 1147.77 1434.71 1721.66 2008.60 2295.54 2582.48 2869.43

MATERIAL : MATTI WOOD BENDING MOMENT CALCULATIONS

1 2 3

DEFLECTION

(mm)

LOAD W (X9.81 N)

INITIAL

FINAL

= Final – Initial

Bending moment (N-m)

0 300 600

17.272 17.272 17.272

17.272 17.403 17.413

0 0.131 0.141

0 286.94 573.89



4 5 6 7 8 9

900 1200 1500 1800 2100 2400


17.272 17.272 17.272 17.272 17.272 17.272

17.413 17.541 17.788 18.007 18.126 Breaking point

0.141 0.269 0.516 0.735 0.854

860.83 1147.77 1434.71 1721.66 2008.60


DEFELECTION vs LOAD GRAPH FOR TEAK WOOD 3500 3000

) 2500 N 1 8 . 2000 9 X ( D 1500 A O L 1000 500 0 0

0.93 1.43 1.92 2.56 2.74

2.9

3.4

4.04

4.2

4.72

DEFLECTION (X0.001 m)

DEFLECTION vs LOAD FOR MATTI WOOD

) N 1 8 . 9 X (

D A O L

1600 1400 1200 1000 800 600 400 200 0 0

1.15

1.65

2.25

DEFLECTION (X0.001 m)


1.05

3.35


SPECIMEN CALCULATION MATERIAL : TEAK WOOD (Sl. No. 2) 1. Deflection, ∆ = Final reading - Initial reading = (17.541-17.272) =26.9 x 10-3 m

= 0.269 mm

2. Load, W = 1200 Kg = 1200 x 9.81= 11772 N Length of the specimen, l = 400.0 mm = 0.4 m Breadth of the specimen, b =47.0 mm = 0.47m Thickness of the specimen, d = 71.0 mm = 0.071m 3. Bending moment, M = W l / 4 = 11772x 0.4 /4 = 1177.2 N-m 4 Maximum bending moment = Wmax x l /4 = 3000 x9.81 x 0.39/4 = 2869.43N-m 5 Momentum of inertia, I = bd3/12= 0.47 x (0.71 )3/12 = 1.4018 x 10-6 m4 6 Stiffness = W /∆ = 2400 x 9.81/ 26.9 x 10 –3 N/m = 875.24 x 103 N/m 7 Maximum bending stress = 3 Wmax L/ ( 2 bd2 ) = 3 x 3000 x 9.81 x 0.4 / ( 2 x 0.071 x (0.047)2) = 91.82 x 106 N/m2 8 From graph

W vs ∆, W = 2500x9.81 N

∆= 3.9 x 10-3 m

Now, Young’s Modulus, E = WL3 / (48 I ∆) = 4.28 x 1015 N/m2

RESULT : SL. No

PROPERTIES

MATERIALS TEAK WOOD

MATTI WOOD 6.19 x 109 1397.93 4.04 x 106 44.17x106

1

Modulus of Elasticity

2 3

(Young’s Modulus) ( N/m2) Maximum Bending (N-m)

9.95 x 109 2869.43 6.29 x 106

4

Stiffness (N/M)

91.82 x 106

CONCLUSION: From above results, it can be concluded that Teak Wood is having more strength than Matti Wood Material Testing lab Manual


EXPERIMENT No. MT08

BRINELL HARDNESS TEST AIM:- To find out the Brinell Hardness Number for the given specimen/s of ferrous metals (mild steel, cost iron) and non-ferrous metals (copper, Brass)

APPARATUS / EQUIPMENT/INSTRUMENTS USED:  

Brinell hardness testing machine , Ball Indentor Traveling microscope .

Brinell Hardness Testing Machine

Equipment Description:Brinell HTM measures the resistance of a material to the penetration of a hardened steel ball subjected to a standard load. This Hardness Tester uses a machine to measure hardness by determining the depth of penetration of a spherical shaped device under controlled conditions. A carbide sphere of a specified diameter under a specified load is applied to the surface of the material and the diameter of the indentation is measured. The diameter of the indentation made is measured with the aid of Microscope. The Brinell hardness value is obtained by dividing the load to the actual surface area. This number is used to make relative comparisons of the different materials. The formula used to calculate the Brinell hardness number is as follows:



Brinell Hardness Number (BHN) = F/[∏/2 (D-√D²- Di²)] Where F - Applied Load D - Diameter of the spherical indenter Di -Diameter of the resulting indenter impression These machines are robustly built to provide laboratory accuracy in the harshest industrial environments and are used all over the world. The only disadvantage is more time is consumed for measuring hardness.







USN: Expt.No:

BRINELL HARDNESS TEST

OBSERVATIONS: Diameter of ball indenter =2.5mm Least count of micrometer =0.001mm

TABULATION: Sl. No. 1 2 3 4

MATERIAL Steel Cast Iron Brass Copper

LOAD

Duration of

Diameter of

(KG)

loading (sec)

indentation(mm)

187.5 187.5 62.5 62.5

15 15 15 15

1.117 1.043 0.82 0.965

1.255 1.031 0.812 0.955

1.247 1.045 0.831 0.975


DERIVATION FOR BRINELL HARDNESS NUMBER The principle of the Brinell Hardness Number is as shown in Figure . From the geometry of the figure,



h = depth of indentation in mm d = diameter of indentation in mm D = diameter of indentor ball in mm O

From triangle OAE, OA =Sqrt ( OE2 – EA2) = Sqrt[( D/2)2 –(d/2)2] h = OB- OA = D/2 - Sqrt[( D/2)2 –(d/2)2] Area of spherical indentation,

D/2 C

D/2 E

A

h B

h

d

A = P x DXh=P x Dx{D/2 - Sqrt[( D/2) 2 –(d/2)2]} = P x (D/2) x{ D - Sqrt[( D) 2 –(d)2]} BHN = Load / Area of spherical indentation = P P x (D/2) x[( D – Sqrt [( D) 2 –(d)2]

Cross Sections of Indentation in Brinell Test

PROCEDURE: 1. Place the polished specimen on the platform. 2. Raise the platform till the surface of the specimen gets focused on the microscope screen. Material Testing lab Manual


3. Select the load by pressing the load selector. Load P : 30XD2 for ferrous materials :10 D2 For non ferrous materials : 5 D2 for soft metals and alloys Where P is the load in kg. and D is the diameter of the indentor in mm. 4 Press the actuator in position,then the load acts on the indentor. 5. Wait till the handle on the left side of the frame comes to rest position. Now allow the load to act for 15 seconds for ferrous materials and 30 seconds for non ferrous materials. 6. Press the handle down without jerk to release the load and to bring the objective lens back into position 7. Measure the diameter of the indentation using the micrometer and microscope 8. For each materials make at least three indentations and measure the diameters. 9. Calculate the BHN for each diameter obtained and take the average of the three. 10. Tabulate the results. 11. Draw the Bar chart

TABULATION AND CALCULATIONS Sl No 1 2 3 4

Material

Load (Kg)

COPPER BRASS MILD STEEL CAST IRON

62.5 62.5 187.5 187.5


Duration Of Diameter of Indentation Loading (mm) (Sec) 30 30 15 15

0.965 0.82 1.117 1.043

0.955 0.812 1.255 1.031

0.975 0.831 1.247 1.045

Average BHN (X108N/M2) 8.05 11.478 15.394 21.112


SPECIMEN CALCULATION MATERIAL : COPPER Applied Load, P = 62.5 Kg. Diameter of Ball, D = 2.5 mm Avg.Diameter of Indentation, d= 0.965 mm BHN = P / [ π x (D/2) x (D- Sqrt D2 – d2)] = 62.5 / [π x(2.5/2)x(2.5 – Sqrt (2.5)2 – (0.965)2)] = 82.143Kg / mm2 = 82.143x9.81 N /mm2 = 8.05 x 108 N/m2

RESULT: 1. Bar chart was drawn for the given materials 2. The BHN’s of the given materials are as shown in below: SL. NO

MATERIAL

1 2 3 4

COPPER BRASS MILD STEEL CAST IRON

r 25 e b m u 20 N s s 15 e n d r 10 a H l l 5 e n i r 0 B

BRINELL HARDNESS NUMBER (X108 N/ m2) 8.05 11.478 15.394 21.112

21.112 15.394 11.478 8.05

COPPER

BRASS

MILD STEEL

Materials


CAST IRON


EXPERIMENT No. MT09

VICKER’S HARDNESS TEST AIM: - To determine the Vicker’s Hardness number of the given material APPARATUS/EQUIPMENT/INSTRUMENTS USED: • •

Vicker’s Hardness Tester, Diamond pyramid indentor.

Vickers Hardness Testing Machine

Vickers HTM is used to measure hardness of metals with hard surfaces. It is measured from the size of an impression produced under standard load by a diamond indenter used, which is pyramidshaped. The diagonal length is measured with a Microscope. The formula used to calculate the Vickers Hardness Number is as follows: Vicker Number (HV) = 1.854(F/ D²) Where, F - Applied Load,

D² - Indentation Area

Advantages of Vickers Hardness Tester The diagonal of the square can be measured easily and accurately Easier method for testing harder materials.

Disadvantages of Vickers Hardness Tester More Complicated & Expensive







USN: Expt.No:

VICKERS HARDNESS TEST

OBSERVATIONS: Indentor = Square pyramid indentor Least count of traveling micrometer =0.001mm

TABULATIONS Sl. No.

1 2 3 4 1

MATERIAL

BRASS CAST IRON MILD STEEL COPPER BRASS

Standard Load P (Kg) 20 30 30 20 20

Diagonal width (mm) d1 0.500 0.501 0.618 0.569 0.500

0.500 0.530 0.610 0.553 0.500

d2 0.486 0.544 0.625 0.558 0.486

0.500 0.559 0.618 0.547 0.500

0.467 0.516 0.620 0.547 0.467

0.500 0.539 0.613 0.548 0.500




THEORY :Vickers hardness number indicate the extent of resistance offered by the material to permanent indentation under static loading . The test consists in forcing a square based diamond pyramid (with an angle of 1360 between opposite faces) into the ground or polished surface to be tested. The pyramidal indentor makes impressions that remain geometrically similar irrespective of its size. The hardness number is derived from the relationship between the applied load and the surface area of the indentation.

Definition: Vickers hardness number is defined as the ratio between load and surface area of the impression and is calculated by formula, Vickers hardness number (VHN) = 2 P sin (q/2)/ d2 = (1.854xP/d2) Kg/mm2 =(18.188 x 106 x P/d2) /m2 Where P = applied load in kg d = Length of diagonal of indentation in m θ = apex angle of the pyramidal indentor

PRINCIPLE :-

Diamond pyramid Indentor (included angle 1360 )

d

2

d

1

Top view of indentation



PROCEDURE:1. Place the polished specimen on the platform 2. Raise the platform till the surface of the specimen is focused on

the microscope screen.

3. Select the load by pressing the load selector button 4. Load , P = 30 Kg, For ferrous materials 5. = 20 Kg. For non-ferrous materials 6. Wait till the handle on the left side of the frame comes to rest position, and after that allow the load to act for 15 seconds for ferrous materials and 30 seconds for non-ferrous materials 7. Press the handle down without any jerk to release the load and to bring the objective lens back into the position 8. Measure the length of the diagonals (d1 and d2) using the traveling micrometer and calculate their average, d. 9. For each material make at least three indentations and measure the length of the diagonals 10. Using the formula, calculate the Vickers hardness number for each trial and calculate their average.

Sl. No.

TABULATION AND CALCULATIONS MATERIAL Load Length of diagonal (mm) (Kg) d1 d2 d=(d1+d2) / 2

VHN X106 N/m2

Average VHNX106 N/m2

1

BRASS

20

0.500 0.500 0.486

0.500 0.476 0.500

0.500 0.488 0.493

1455.02 1527.46 1496.65

1493.04

2

COPPER

20

0.569 0.553 0.558

0.547 0.547 0.548

0.558 0.550 0.553

1168.26 1202.49 1189.48

1186.74

3

CAST IRON

30

0.541 0.530 0.544

0.559 0.516 0.539

0.550 0.523 0.542

1803.74 1994.79 1857.38

1885.3

4

MILD STEEL

30

0.618 0.610 0.625

0.618 0.620 0.613

0.618 0.615 0.619

1428.64 1442.61 1424.03

1431.76

SPECIMEN CALCULATION Material Testing lab Manual


Material : Brass Load,P = 20 Kg = 20 x 9.81 N = 196. 2 N For Trial 1,

Length of diagonals, d1 = 0.500 mm & d2 = 0.500 mm Average length of diagonal, d = (d1 +d2)/2 = (0.500 +0.500)/2 = 0.500 mm = 0.500 x 10- 3 m VHN1 = (18.188 x 20)/ (0.500 x 10 - 3 ) 2 = 1455.02 x 106 N/m2 VHN2 = (18.188 x 20)/ (0.488 x 10- 3 ) 2 = 1527.46 x 106 N/m2 VHN3 = (18.188 x 20)/ (0.493 x 10- 3 ) 2 = 1496.65 x 106 N/m2 Average VHN = (VHN1+VHN2+VHN3) / 3 = {(1496.63+1455.02 +1455.02) x 106} / 3 N/m2 = 1493.04 x 106 N/m2

RESULTS:MATERIAL

VICKER’S HARNESS NUMBER (x106 N/M2)

COPPER BRASS CAST IRON MILD STEEL

1186.74 1493.04 1885.30 1431.76

2000

1885.3

1800

. o 1600 N s 1400 s e n 1200 d r 1000 a H s 800 r e k 600 c i V 400

1493.04

1431.76

1186.74

200 0 COPPER

BRASS

CAST IRON

MILD STEEL

Materials

EXPERIMENT No. –MT07 Material Testing lab Manual


COMPRESSION TEST AIM: To study the behaviour of the given materials under compressive loading and to determine the following properties: 1. Maximum Compressive strength, 2. Proportional limit, 3. Elastic limit (Young’s modulus)

APPARATUS/EQUIPMENT/INSTRUMENTS USED • Universal testing machine, • Vernier Caliper, • Compression shackles.

Universal Testing Machine







COMPRESSION TEST

USN: Expt.No:

OBSERVATIONS: Least count of Vernier Caliper =0.02mm

TABULATION

SL.

CHARACTERISTIC OF THE

NO.

SPECIMEN

1 .

BRASS

MILD STEEL

22.00

21.16

18.00

18.40

16.78

14.70

21.60

22.60

Initial Height of the specimen (hi) mm

2 .

MATERIAL

Initial Diameter of the specimen (di) mm

3 .

Final Height of the specimen (hf ) mm

4

Final Diameter of the specimen (df ) mm

.




TABULATION: INITIAL SCALE READING = 100 mm

MATERIAL : MILD STEEL SL. LOAD SCALE NO (KG) READING (mm) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 14000 15000 16000 17000 18000 19000 20000 21000 22000 23000 24000 25000 14000 15000


100 101 101 101 101 101 101 101 101 101 102 103 104 104 105 105 106 106 106 106 107 108 102 103

MATERIAL : BRASS SL. NO LOAD (KG) SCALE READING (mm) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26.

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000 16000 17000 18000 19000 20000 21000 22000 23000 24000 25000

10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 100 101 101 101 101 101 101 102 103 103 103 104 104 104 104 105 105 105


27. 28. 29.

26000 27000 28000

106 106 106

PROCEDURE : 1. Fix the lower and upper compression plates in between the bottom cross head and intermediate crosshead. 2. Measure the initial diameter (di) and initial height (hi) of the given specimen using vernier caliper. 3. Place the specimen at the centre of the bottom plate and bring the top of the specimen in contact with the top plate by moving the intermediate cross head down wards. 4. Apply compressive load in steps of 1000 Kg. 5. The experiment is continued till the specimen attains a barrel shape on reaching the max load for ductile materials or fractures at maximum load for brittle materials. 6. 6.Record load values and corresponding decrease in heights form the scale which is fixed to the UTM. 7. Measure final height (hf ) and largest diameter of the specimen (df ) using vernier caliper 8. Calculate stress and corresponding strain. 9. Plot the stress- strain diagram . 10. Calculate the young’s modulus from the graph ( Slope of the graph –with in elastic limits)

MATERIAL : BRASS INITIAL SCALE READING = 100 mm , A= 254.47mm2 SL NO 1 2 3 4 5 6 7 8

LOAD (Kg) 0 1000 2000 3000 4000 5000 6000 7000

SCALE READING (mm)

STRESS x106(N/m2)

100 100 100 100 100 100 100 100

0 38.55 77.10 115.65 154.20 192.75 231.30 269.85


STRAIN 0 0 0 0 0 0 0 0


9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

8000 9000 10000 11000 12000 13000 14000 15000 16000 17000 18000 19000 20000 21000 22000 23000 24000 25000 26000 27000 28000

100 101 101 101 101 101 101 102 103 103 103 104 104 104 104 105 105 105 106 106 106

308.41 346.96 385.51 424.06 462.61 501.16 539.71 578.26 616.81 655.36 693.91 732.46 771.01 809.56 848.12 886.67 925.22 963.77 1002.32 1040.87 1079.42

0 0.045 0.045 0.045 0.045 0.045 0.045 0.091 0.136 0.136 0.136 0.182 0.182 0.182 0.182 0.227 0.227 0.227 0.273 0.273 0.273

MATERIAL: MILD STEEL INITIAL SCALE READING :SL NO 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

LOAD (Kg) 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000 16000

SCALE READING (mm)

STRESS x106(N/m2)

100 100 100 100 100 100 100 100 100 101 101 101 101 101 101 102 103

0 38.55 77.10 115.65 154.20 192.75 231.30 269.85 308.41 346.96 385.51 424.06 462.61 501.16 539.71 578.26 616.81


STRAIN 0 0 0 0 0 0 0 0 0 0.045 0.045 0.045 0.045 0.045 0.045 0.091 0.136


18 19 20 21 22 23 24 25 26 27 28 29

17000 18000 19000 20000 21000 22000 23000 24000 25000 26000 27000 28000

103 103 104 104 104 104 105 105 105 106 106 106


655.36 693.91 732.46 771.01 809.56 848.12 886.67 925.22 963.77 1002.32 1040.87 1079.42

0.136 0.136 0.182 0.182 0.182 0.182 0.227 0.227 0.227 0.273 0.273 0.273


SPECIMEN CALCULATION Material: Brass (Sl.No.2) 1.Stress = P/A = Load in Kgs x 9.81 / Initial Area 2.Initial Area (Ai) = πdi2/4 = π x (18.00)2/4 = 254.47 mm2 = 245.47 x 10-6 m2 3.Stress = 1000 x 9.81 / (245.47 x 10-6) = 38.55 x 106 N/m2 4.Change in Height = Scale reading – Initial Scale reading = 100 – 100 = 0mm 5.Strain = Change in Height / Original Height = 0/ 21.16 = 0.00 6.Final area (Af ) = πdf 2/4 = π x (21.6)2/4 = 401.15 mm2 = 388.15 x 10-6 m2 7. % increase in area = (Af – Ai) x 100 / Ai = 44.00 8. % decrease in height = (hf – hi) x 100 / hi = 23.73 9. Compressive Strength = Max. Load / Initial Area = 28000 x 9.81/ (245.47 x 10-6) = 10.79 x 108 N/m2 10. Modulus of elasticity (from graph) = 10.33 x 109 N/m2

SPECIMEN CALCULATION B. Material: Mild Steel (For l.No.2) 1.Stress = P/A = Load in Kgs x 9.81 / Area 2.Initial Area (Ai) = πdi2/4 = π x (18.00)2/4 = 254.47 mm2 = 245.47 x 10-6 m2 3.Stress = 1000 x 9.81 / (245.47 x 10-6) = 38.55 x 106 N/m2 4.Change in Height = Scale reading – Initial Scale reading = 101 – 100 = 1mm



5. Strain = Change in Height / Original Height = 1/ 21.16 = 0.047 6. Final area (Af ) = πdf 2/4 = π x (22.6)2/4 = 401.15 mm2 = 401.15 x 10-6 m2 7. 8. 9.

10.

% increase in area = (Af – Ai) x 100 / Ai = 57.64 % decrease in height = (hf – hi) x 100 / hi = 30.53 Maximum Compressive Strength = Max. Load / Initial Area = 25000 x 9.81/ (245.47 x 10-6) = 9.64 x 108 N/m2 Modulus of elasticity (from graph) = 5.67 x 109 N/m2

SPECIMEN SKETCH MATERIAL :DUCTILE BEFORE TESTING

AFTER TESTING


MATERIAL :BRITTLE BEFORE TESTING

AFTER TESTING


STRESS vs STRAIN GRAPH FOR BRASS MATERIAL

RESULT SL. NO.

PARAMETER

1.

Decrease in height (%)

23.73

30.53

2

Increase in area (%)

44.00

57.64

3

Compressive strength ( N/m2)

10.7942x108

96.377x108

4

Modules of elasticity (N/m2)

1.033x109

5.67x109


BRASS

MILD

S T E E L


EXPERIMENT No.S01&S02 PREPARATION OF SPECIMEN FOR METALLOGRAPHIC EXAMINATION & MICROSTRUCTURE STUDY OF THE ENGINEERING MATERIALS Objective: To study the microstructure of the given specimen (micro-section) and to determine the grain size.

Apparatus: Hand press, flat file, emery papers of various grades, rotary polishing machine and metallurgical microscope.

Theory: Micrography is the study of the structures of metals and their alloys under a microscope at magnification from x75 to x1500. The observed structure is called the microstructure. The metallographic studies include; 1. 2. 3. 4. 5.

Determination of size and shape of the crystallites, which constitute an alloy. Reveal the structure characteristic of certain type of mechanical working operations. Detect the micro-defects such as nonmetallic inclusions, micro cracks, etc. Determine the chemical content of alloy. It indicates the quality of heat treatment.

Preparation of specimens for microscopical examination: The various steps involved in preparing a specimen for microscopic examination are given below. 1. Selection of specimen: When investigating the properties of a metal, it is essential that the specimen must be homogeneous in composition and crystal structure. A specimen of 10mm diameter or 10mm square is cut from the metal with a saw or water-cooled slitting wheel. The thickness of the specimen should not be more than 12mm. When a specimen is so small that it is difficult to hold, the specimen may be mounted in a suitable compound like thermoplastic resin, by using a hand press. In cases where neither pressure nor heating is desirable, a cold setting thermoplastic resin can be cast round the specimen, a specimen whose surface has been prepared for micro analyses is called micro-section. 2. Grinding: It is primarily necessary to obtain a reasonably flat surface of the specimen. This can be achieved either by using a fairly coarse file or by using motor-driven emery belt. Care must be taken to avoid overheating of the specimen by rapid grinding methods; since this may lead to alterations in the microstructure. When the original hacksaw marks have been ground out, the specimen should be thoroughly washed. 3. Fine grinding: Fine grinding is carried out on waterproof emery papers of progressively finer grades (220, 320, 400 and 600) that are attached to a plane glass plate. The specimen is drawn back and forth along the entire length of No. 220 paper, so that scratches produced are roughly at right angles to those produced by the preliminary grinding operation. Having removed the primary grinding marks, the specimen is washed thoroughly. Grinding is then continued on No. 320 paper and again turning the specimen through 900 until the previous scratch marks has been removed.



This process is repeated with No. 400 and No. 600 papers. Light pressure should be used at all stages. 4. Polishing: The final polishing operation is to remove the fine scratches on the surface by using a rotary polishing machine. The specimen is polished by rubbing it on a soft moist velvet cloth mounted on a flat rotating disc, with the polishing paste. Suitable polishing pastes are fine alumina, magnesia, Chromium oxide or diamond dust. Polishing is continued until a mirror scratch free finish is obtained. Non-ferrous specimens are best finished by hand on a small piece of selvyt cloth wetted with silvo polishing. This should be accomplished with a circular sweep of the hand instead of back and forth motion used in grinding. During polishing a constant trip of water is fed to the rotating pad. After polishing, the specimen must be washed thoroughly. The grease films if any can be removed by immersing the specimen in boiling ethanol.

5. Etching: To make its structure apparent under the microscope, it is necessary to impart unlike appearances to the constituents. This is generally accomplished by selectively corroding or etching the polished surface by applying a chemical etching reagent. Grain boundaries will etch at different rates than the grains, then leaving the grains standing out and they become visible with a reflected light microscope.



EXPERIMENT No. –D03 HEAT TREATMENT OF STEEL MATERIALS & STUDY OF THEIR HARDNESS USING THEIR ROCK-WELL TESTING MACHINE (ANNEALING AND NORMALIZING OF STEEL) Objective: To heat treat the given steel specimen( anneal or normalize)and determine the Rockwell hardness.

Apparatus: Austenitizing furnace (upto-1000ºC) and Rockwell hardness testing machine. Theory: The microstructure of steel part can be modified by heat treatment techniques, that is, by controlled heating and cooling of the alloys at various rates. These treatments induce phase transformations that greatly influence mechanical properties of steel. The various heat-treatment processes are annealing, normalizing, hardening and tempering. Annealing of steel is the process of heating the steel specimen to its austenizing temperature, holding it there long enough to dissolve the cementite and disperse the carbon uniformly and then cool it very slowly to change the structure to the softest state. The low rate of cooling is achieved by turning the furnace off and letting the closed furnace cool down to ambient temperature. The annealing temperature of hypoeutectoid steel is

t anneal = Upper critical temperature + 30ºC to 50ºC To avoid excessive softness in the annealing of steels, the cooling cycle may be done completely in still air. This process is called normalizing. In normalizing, the part is heated to normalizing temperature and is withdrawn from the furnace. It is then cooled in still air at the room temperature. The more drastically cooled austenite decomposes into a more dispersed aggregate made up of pearlite. After annealing and normalizing, a fine grain structure is obtained, provided there is no super heating. The normalizing temperature is usually 30ºC to 50ºC more than that of annealing temperature. The purposes of annealing are: 1. To obtain softness. 2. To improve machinability. 3. To increase ductility and toughness. 4. To relieve internal stresses. 5. To refine the grain size. . 6. To prepare steel for subsequent cold working. The purposes of normalizing the steel are: 1. To eliminate coarse-grained structure obtained in previous working (rolling, forging or stamping). 2. To increase the strength of medium carbon steel. 3. To improve machinability of low carbon steel. 4. To reduce internal stresses.



Heat-treating furnace: A heat-treating furnace is a refractory lined chamber in which the metal parts are heated to the required temperature. Usually the furnace consists of a box-like structure of steel shell, door, refractory lining. heating source, temperature controls and temperature indicators.

Procedure for annealing: 1. Heat the given given steel steel specimen specimen in a box type type furnace furnace until the the specimen specimen reaches reaches the annealing annealing temperature. 2. keep the specimen specimen in the furnace at the annealing annealing temper temperature ature for some time time 3. Cool the speci specimen men by by switchi switching ng off the the furnace furnace.. 4. Remove the the steel specimen specimen from from the furnace furnace when when the furnace furnace is cooled cooled down to to atmospheric atmospheric temperature. 5. Determine Determine the hardness hardness of the annealed annealed specime specimen n using Rockwell Rockwell hardness hardness testing testing machine. machine.

Procedure for normalizing: 1. Heat Heat the the give given n stee steell spec specim imen en in a box box type type furn furnac acee unti untill the the spec specim imen en reac reache hess the the normalizing temperature. 2. keep the the specimen specimen in the the furnace furnace at the normaliz normalizing ing temperat temperature ure for some some time 3. Remo Remove ve the the stee steell spec specim imen en from from the the furn furnac acee when when the the furn furnac acee is cool cooled ed down down to atmospheric temperature. 4. Dete Determ rmine ine the the hardne hardness ss of the norma normali lized zed spec specim imen en using using Rockw Rockwel elll hardne hardness ss testi testing ng machine.



EXPERIMENT NO. MT05

WEAR TEST AIM: To study the wear properties of the given specimen and to determine the wear rate. APPARATUS/ TOOLS/ EQUIPMENT USED:     

Wear testing machine Tachometer Scale Digital weighing machine Digital stopwatch.

THEORY: Wear is defined as the progressive loss or removal of material from a surface. Usually parts damaged by wear can be repaired or replaced before disastrous failure takes place. Wear is usually classified as adhesive, abrasive, corrosive, fatigue, fretting, and impact wear. Adhesive wear: If a tangential force is applied between the two sliding blocks, shearing can take place either at the original original interface or along a path below or above it, causing adhesive wear. The fracture path depends on whether or not the strength of the adhesive bond of the asperities is greater than the cohesive strength of either of the two sliding bodies. Thus during sliding, fracture at the asperity usually follows a path in the weaker or softer component. A wear fragment is then generated. Although this fragment is attached to the harder component, it eventually becomes detached during further rubbing at the interface and develops into a loose wear particle. This process is known as adhesive wear or sliding wear. Adhesive wear can be reduced by: 1. Selecting materials that do not form strong adhesive bonds. 2. Using a harder material as one of the pair. 3. Using materials that oxidize more easily. Abrasive wear: Abrasive wear is caused by a hard and rough surface sliding across a surface. This type of wears removes particles by forming microchips, thereby producing grooves or scratches on the softer surface. The abrasive wear resistance of metals is directly proportional to their hardness. Abrasive wear can thus be reduced by increasing the hardness of materials or by reducing the normal load. Several methods can be used to observe and measure wear. In general a wear testing machine consists of a means for applying load to a specimen of materials, which is rubbed at a given speed over another piece of material or over an abrasive surface. The amount of wear after a given amount of rubbing is measured either by loss of weight of the specimen or by dimensional changes.



Wear Testing Machine

The material abrasion wear test machine is used to determine the wear coefficient of hard and soft coating and monolithic materials by abrasive wear in a ball on plate contact configuration. The machine may also be used as a crater generating tool on coated surfaces for coating thickness determination. Test materials are paint films, plastic, coating, shoe material, slurry abrasion. This system can do following wear test: 1. Ball Cratering Test 2. Grinding Process 3. Micro scale Abrasion In general wear testing machine consists of a means for applying load to a specimen of material, which is rubbed at a given speed over another piece of material or over an abrasive surface. The amount of wear after a given amount of rubbing is measured either by loss of weight of specimen or by dimensional changes







USN: Expt.No:

WEAR TEST

OBSERVATIONS:

• • • • • •

Least count of Vernier Caliper = 0.02mm Radius of wear track in meter (R) = 90mm Speed of the wheel in RPM, (N) = 400 Length of the arm from specimen holder to load point (L1) =300mm Length of the arm from specimen holder to Hanger point (L2) =150mm Sliding time (T) = 10min

TABULATION: Sl. Specimen No Material 1 2 3 4

Load, WH (Kg)

Aluminium Brass Aluminium Brass

1 1 2 2

Weight (gms) Initial (w1) Final (w2) 0.951 2.411 0.949 2.325

0.949 2.325 0.946 1.158

Density, (x103 kg/m3)

BHN

2.8 6.8 2.8 6.8

40 103 40 103


PROCEDURE: 1. Clean the the surface surface of the disc disc and the the specimen specimen by alcohol and acetone. acetone.



2. Weigh the specimen in digital weighing machine, measure the length of the arm and the track radius by using scale. Also a note down the length of specimen. 3. Fix the specimen on the horizontal arm using Allen key and place it on the disc. 4. Note down the speed of the disc and switch on the motor. 5. Load the specimen and adjust the displacement sensor to read zero. 6. Switch off the motor after the required interval of time 10 min. 7.

The final weight is recorded using digital weighing machine.

8. The wear coefficient and wear rate are calculated by the formulae Wear coefficient K =

VH FS

and

Wear rate in debri’s (mm3), V = Weight loss / Density of metal = (Initial weight – Final weight) / Density of metal 9. Repeat the above procedure to the other specimen for a given period at constant velocity. Load may also be changed from 1 kg to 2 kg. 10. Repeat the procedure on the other specimens for given load by changing time, speed of the track, track radius, etc.

Formulae used:Wear coefficient K =

VH FS

and

Wear rate = V / S Where

V = Volume of wear m3 = Weight loss / Weight loss (Kg) = (W1 – W2) / 100 W1 = Initial weight of the specimen (gms) W2 = Final weight of the specimen (gms) ρ = Density of the metal (Kg/m3)

H = Hardness of material (B H N) N/m2

L = Normal load (Newton) = W x 9.81 x L1 / L2 W = applied load in Kgs,



L1 = length of the arm from specimen holder to load point in meter L2 = length of the arm from specimen holder to hanger point in meter

S = Sliding distance (meter) = x D x N x T = 2 RNT D = Diameter of wear track in meter R = Radius of wear track in meter N = Speed of the wheel in rpm and T = Sliding time in minutes

Wear rate (mm3 / m) = V/S V = Volume of wear in debri’s in mm3 S = Sliding distance in meter

Sl. No

Specimen Material

Load, WH (Kg)

1 2 3 4

Aluminium Brass Aluminium Brass

1 1 2 2

Weight (gms) Initial Final (w1) (w2) 0.951 2.411 0.949 2.325

0.949 2.325 0.946 1.158

Density, (x103 kg/m3)

BHN

Wear coefficient Kx10-12

Wear rates,mm3/m x10-13

2.8 6.8 2.8 6.8

40 103 40 103

2.49 113 1.90 110

3.0565

Specimen Calculation Material – Aluminum Least count of Vernier Caliper = 0.01 mm Weight loss = W1 – W2 = 0.951 – 0.949 = 2 x 10-3 gms = 2 x 10-6 Kg Density of the metal, ρ = 2.8 x 104 Kg/m3 Harness of material H = 40 B H N Radius of wear track in meter R = 93 x 10-3 m Speed of the wheel in rpm N = 400 rpm Sliding time T = 10 min Length of the arm from specimen holder to load point, L1 = 360 x 10-3 m Length of the arm from specimen holder to hanger point in meter L2 = 150 x 10-3 m

For trial 1, Load = 1 Kg Initial Weight, W1 = 0.951 gms Final Weight, W2 = 0.949 gms Weight loss = W1 – W2 = 0.951 – 0.949 = 2 x 10-3 gms = 2 x 10-6 Kg


4.5845


Volume of material removed

=

w1 − w2

= 2 × 10

ρ

−6

( 2.8 × 10 ) 3

= 7.143 x 10-10 m3 H = 40

Force F =

W H L2  1 × ( 9.81) × 150 mm = 4.905 N  L  × 9.81 = 300 mm  1 

Sliding distance = 2πRNT = 2π x 93 x 10-3 x 400 x 10 = 2337 m Wear coefficient K 1 Wear rate

=

7.143 × 10 −10

× 40

4.905 × 2337

= 2.49 × 10 −12

= V / S = 7.143 x 10-10 / 2337 = 3.0565 x 10-13 mm3 / m

Advantages i. ii. iii. iv.

High reproducibility Short test time Simple flat test geometry Simple operation

Disadvantages i. The tester does not have an arrangement for keeping the air humidity at a constant level. ii. Large variations in humidity might affect the reproducibility. iii. Expensive

Department of Industrial Engineering and Management R.V. College of Engineering, Bangalore – 59 VIVA QUESTIONS Material Testing lab Manual


1. How do you define the word 'Engineering Material’? 2. What are the objectives of testing of materials? 3. Write brief classification of materials. 4. List out the properties of materials. 5. What is purpose of doing the following tests: Tensile Test, Compression Test, Shear Test, Impact Test, Hardness Test 6. In Tensile test, what is the nature of failure for brittle and ductile material? 7. Define stress and strain. In what unit is each one measured? 8. State Hook's law. Is this applicable to all materials? 9. Define the following terms: elastic limit, proportional limit, yield point, yield strength, resilience and toughness. Do all materials have yield point? Give examples 10. What is the use of tensile test? What factor should be considered in selecting the gauge length? 11. Which property in a tension test is an indication of stiffness of a material? 12. What is the difference between the proportional limit and the elastic limit? 13. Distinguish between yield point and yield strength? 14. What are the uses of hardness test? 15. What are the types of hardness measurement? 16. What are the types of hardness test, with brief explanation? 17. What are the advantages of Rockwell test over Brinell's Test? 18. How do you define single shear and double shear? 19. How do you place the specimens in impact test? 20. What is metallography? 21. What are the types of metallurgical microscopes? 22. What are the steps involved for preparation of metallographic specimen? 23. What is the purpose of conducting the wear test? 24. What are the types of wear? 25. What are the factors affecting wear? 26. What is the importance of fatigue test? 27. Describe the events that occur when a specimen undergoes a tension test. 28. How is stress calculated? What additional measurement must be made to determine the true stress? 29. Explain why the difference between engineering strain and true strain becomes larger as strain increases in tension? 30. What is breaking stress? How does it differ from the maximum stress? 31. If a brittle material and a ductile material have same tensile strength. Which one will require the greater energy for fracture? Explain. 32. Describe the difference between brittle and ductile fracture? 33. What is universal testing machine? Describe briefly the mechanism for applying load, and for measuring force in testing machine. 34. What is the effect of rate of loading on tensile properties? 35. What are the limits of ratio of the height to the diameter of the compression specimen? 36. Explain compression fracture of the following materials: (a) cast iron, (b) mild steel and (c) wood. 37. How failure in bending occurs in the following materials? (a) Cast iron, (b) mild steel and



(c) wood. 38. What physical property of the material is determined by means of an impact test? 39. Discuss the significance and advantages of impact test compared with static tests. 40. In what units are the results of an impact test usually given? 41. For impact tests why are notch specimens used? 42. What is difference between Charpy tests and Izod tests? 43. What is meant by velocity sensitivity and notch sensitivity? 44. What is the effect of temperature on impact toughness? What is a transition temperature? 45. Explain the impact fracture as in the case of ductile material. 46. Define hardness. Why is hardness test conducted instead of tension test? 47. What physical properties of a material can be estimated from a hardness test? 48. What is the unit for Brinell hardness number? 49. Where are the Vickers and Rockwell hardness test employed? 50. Why is a minor load applied before setting the Rockwell measuring dial? 51. What is stress concentration? What is stress raiser? 52. What is meant by the term fatigue of metals? 53. Define the following terms in discussing fatigue tests: Stress cycle, maximum stress, range of stress, minimum stress, normal stress, alternating stress, amplitude, mean stress, fatigue life, fatigue limit, stress ratio, cycle ratio, fatigue strength and fatigue ratio. 54. Explain why there is difference between a theoretical stress concentration factor and the actual-strength reduction factor found in actual tests? 55. What are the types of fatigue loading? Give examples of machine parts and structures subjected to fatigue loading. 56. If a material does not have an endurance limit, how would you estimate its fatigue life? 57. What type of fracture would you expect in the case of steel member fractured by repeatedly applied loads? Explain the mechanism of such fracture. 58. What is creep? Name two structural or machine members in which creep strength is an important property. 59. State the resemblance and the difference between creep and slip? 60. Does wood creep? State evidence for your answer. 61. Define wear of the material. Name different types of wear. 62. Define micrography. 63. What are the general objectives of the macro examination of a metallic component as compared with the micro examination of a metal? 64. Describe the various steps involved in preparation of specimen for micrographic examination. 65. What is the difference between eutectic and eutectoid? 66. Explain the Curie point in iron, iron-carbide equilibrium diagram. 67. What is annealing? What are the purposes for annealing steel? 68. How does normalizing differ from annealing as applied to steels? 69. What are the advantages of the normalizing process in respect of final properties? 70. Describe the hardening process. Where does the defect occur after hardening the steel? 71. Explain what happens in steel when it is hardened by quenching.Name several quenching media. 72. What is age hardening? 73. Explain the difference between hardness and harden ability?


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