department of production engineeringhithaldia.ac.in/cm/pe/lab/06. me 493.pdfweighted pendulum hammer...

DEPARTMENT OF PRODUCTION ENGINEERING HALDIA INSTITUTE OF TECHNOLOGY

LAB MANUAL ON

MATERIAL TESTING LABORATORY (ME 493)

CREDIT: 2

CONTACT HOURS / WEEK: 0-0-3

Syllabus

Material Testing Lab (ME 493)

Impact tests: Charpy and Izod tests; Test for drawability of sheet metals through cupping test; Fatigue test of a typical sample. Sample preparation and etching of ferrous and non-ferrous metals and alloys for metallographic observation; Experiments on heat treatment of carbon steels under different rates of cooling including quenching and testing for the change in hardness and observing its microstructural changes through metallographic studies. Observation of presence of surface/ sub-surface cracks using different non-destructive techniques, such as dye penetration (DP) test, magnaflux test, ultrasonic or eddy current test.

(At least six experiments must be conducted)

Course Outcome:

COS ME 493.

ME 493. 1 Students will demonstrate the knowledge and the skills required w.r.t the procedure conduction and analyzing the results w.r.t Tensile, Shear and Compression, Torsion Test , Bending Test etc

ME 493. 2 The ability to explain heat treating principles; quenching and tempering, solutionizing and aging, and annealing.

ME 493. 3 Set up testing strategies and select proper instruments to evaluate performance characteristics

ME 493. 4 Prepare professional quality textual and graphical presentations of laboratory data and computational results

ME 493. 5 Primarily via team-based laboratory activities, students will demonstrate the ability to interact effectively on a social and interpersonal level with fellow students, and will demonstrate the ability to divide up and share task responsibilities to complete assignments

ME 493. 6 Evaluate possible causes of discrepancy in practical experimental observations in comparison to theory.

CO-PO Correlation:

COS ME 493. PO1 PO2 PO3 PO4 PO5 PO6 PO7 PO8 PO9 PO10 PO11 PO12


3 2 1 2 1 - - - - - - -


3 1 1 1 - - - - - - - -


3 3 3 2 1 1 1 - 1 1 1 1


3 1 - - 1 - - - 1 1 - -


3 2 2 2 2 1 1 1 1 1 1 1


2 3 2 2 1 2 1 - 1 1 1 1

* Enter correlation levels 1, 2 or 3 as defined below: 1: Slight (Low) 2: Moderate (Medium)3: Substantial (High) and It there is no correlation, put “-”

2.83 2.00 1.80 1.80 1.20 1.33 1.00 1.00 1.00 1.00 1.00 1.00

CO-PSO Correlation:

COS ME 493 PSO1 PSO2 PSO3


3 3 3


3 3 3

ME 493. 3 Set up testing strategies and select proper instruments to evaluate performance characteristics 3 2 3


3 3 3


3 3 3


3 2 2

* Enter correlation levels 1, 2 or 3 as defined below: 1: Slight (Low) 2: Moderate (Medium)3: Substantial (High) and It there is no correlation, put “-”

3.00 2.67 2.83

CO-EXPERIMENT CORRELATION MAP:

COS ME 493. E-O1 E-O2 E-O3 E-O4 E-O5 E-O6

ME 493. 1

Students will demonstrate the knowledge and the skills required w.r.t the procedure conduction and analyzing the results w.r.t Tensile, Shear and Compression, Torsion Test , Bending Test etc




ME 493. 5

Primarily via team-based laboratory activities, students will demonstrate the ability to interact effectively on a social and interpersonal level with fellow students, and will demonstrate the ability to divide up and share task responsibilities to complete assignments


EXPERIMENT NO-1:

Impact Test.

EXPERIMENT NO-2:

Fatigue Test

EXPERIMENT NO-3:

Erichsen Cupping Test

EXPERIMENT NO-4:

Metallography

EXPERIMENT NO-5:

Non-destructive Test

EXPERIMENT NO-6:

Heat Treatment

Department of Production Engineering

Sub: Material Testing Lab

Experiment No: ME-493/01

Title : Impact Test

Objective : To determine the impact toughness (strain energy) through Izod test and Charpy test.

Principle: Notched-bar impact test of metals provides information on failure mode under high velocity loading conditions leading

sudden fracture where a sharp stress raiser (notch) is present. The energy absorbed at fracture is generally related to the area under

the stress-strain curve which is termed as toughness in some references. Although two standardized tests, the Charpy and Izod,

were designed and used extensively to measure the impact energy, Charpy v-notched impact tests are more common in practice.

The apparatus for performing impact tests is illustrated schematically in Figure-I. The load is applied as an impact blow from a

weighted pendulum hammer that is released from a position at a fixed height h. The specimen is positioned at the base and with

the release of pendulum, which has a knife edge, strikes and fractures the specimen at the notch. The pendulum continues its

swing, rising a maximum height h ' which should be lower than h naturally.

Procedure:

1. Measure the dimensions of a specimen. Also measure the dimensions of the notch.

2. Raise the hammer and note down the initial reading from the dial, which will be the energy to be used to fracture the

specimen.

3. Place the specimen for test and see that it is placed centre with respect to the hammer. Check the position of the notch.

4. Release the hammer and note the final reading. Difference between the initial and final reading will give the actual

energy required to fracture the specimen.

5. Repeat the test for specimens of other materials.

6. Compute the energy of rupture of each specimen.

Evaluation of test: The notch impact strength (I) is calculated as per the following formula,

I = K/A

Where I – Impact strength in Joules/cm2

K – Impact energy absorbed by the specimen during rupture in Joules.

A – Area of cross-section of specimen below the notch before test in cm2.

Result:

Find out the impact strength of given specimen.

Frequently asked questions during Interviews

(i) What are the 3 basic factors which contribute to brittle fracture of steels?

(ii) What are the main uses of the Charpy test?

(iii) Explain the relation between fracture toughness (KIC) of steels and impact.

(iv) Explain the effect of carbon content on transition behavior of plain carbon steels in annealed condition.

(v) List the ASTM specifications for the two impact tests with titles.

Fig 2- Specimen and loading configuration for Charpy V-notched impact test

Fig 3-Position of specimen for Izod test

Fig 1-Schematic impact testing equipment




Title : Fatigue Test

Objective : To become conversant with the method of Fatigue testing of a material

Theory: Practically all materials will break under numerous repetitions of a stress that is lower than the stress required for

producing an immediate rupture. This phenomenon is known as fatigue. Repetition of stress in a component occurs when the

applied load fluctuates between maximum and minimum values (dynamic loading).

Analysis: The specimen loading arrangements results in a constant bending moment PL/2 over the test length of the specimen.

P = Load applied over the specimen – kgf.

L = 10 cm

Bending moment Mb = PL/2 = 5P kgf.cm

Bending stress fb = Mb/Z kg/cm2

Z = section modulus

= Πd3/32 for circulation cross-section [d=0.8 cm]

Therefore, fb = (Mb X 32)/ Πd3 = (50.93 P)/d

3 kgf/cm

2

The S-N diagram which is a graph of stress on Y-axis and number of revolutions on the X-axis at log scale is then drawn. This

diagram tells us about the behavior of material under application of repeated load.

In the second case, the bending stress to be applied is decided depending upon the design requirements. Suppose the design

requirement is such that it should withstand a bending stress of 2000 kg/cm2. Then the load to be applied is calculated as follows:

fb = (50.93 x P)/d3

P = (fb x d3)/ 50.93

= [2000 x (0.8)3]/ 50.93

= 20.1 kgf

Test Procedure: 1. Prepare the test specimen.

2. Fix the specimen to the specimen-pulling out stud in the tapping

provided over face.

3. Insert the specimen with stud into the bore of L.H. swiveling

body and push it further till it inserts in the collect of R.H. swiveling body and rests against the specimen locator.

4. By pressing down the locking rod such that it inserts into the slots of locking ring and prevents hollow shaft from rotating,

tighten the specimen by rotating the clamping cum loosening ring with the help of a special spanner.

5. The locking rod is spring-loaded and hence it will immediately come out of the slots, as soon as the hand is released. In no

case, should the locking enter the slots when the machine is in running condition.

6. Repeat the procedure for the other side assembly. Take out the specimen pulling-out stud.

7. Select the load required, depending upon the bending moment to be imposed, by moving the loading weight and selecting

proper set of additional weights.

8. Lock the loading weight by locking screw.

9. Use the pin and support while moving the loading weight so that the lever is not moved. Remove the pin from support before

starting the motor otherwise the specimen will rotate without application of any bending moment.

10. Check the direction of rotation.

11. Reset the counter.

12. Start the motor. The motor will stop after the specimen fails and the counter will record the number of revolutions completed

by the specimen.

Results:

A plot of S-N curve is plotted in a semi-log graph paper using the results of an experiment.

From the plot determine the following: Fatigue limit, Fatigue strength at 106 cycles and Fatigue life at 2500 kgf/cm

2


(i) What is distinctive about the surface appearance of a fatigue fracture? What information can be obtained observing the

fracture surface?

(ii) What are the stages in a fatigue fracture?

(iii) Where do most fatigue cracks start? Why?

(iv) What is the mean stress and the R-ratio?

(v) What is the difference about behavior of steel and Aluminum?




Title : Erichsen Cupping Test

Objective : Test for draw-ability of sheet metals through cupping test

Introduction: Erichsen deep drawing test has a deep rooted hold on modern industry. Deep drawing is the conversion of a plain sheet blank into

a hollow body by drawing the material into the female die with a punch. A pressure plate is employed to prevent the formation of

wrinkles in the blank; this holds the blank against the female die which, in some cases is called the furrow holder. This test is used

for assessing the cupping qualities of metal sheet and strip within the limits imposed by the test conditions. Drawability is a ratio

of the initial blank diameter (Do) to the diameter of the cup drawn from the blank (punch diameter Dp)

Limiting draw ratio (LDR) = Do

Dp max ≈ e

η Where, η is an efficiency term accounting for frictional losses.

Practical considerations affecting drawability:

Die radius – should be about 10 x sheet thickness.

Punch radius – a sharp radius leads to local thinning and tearing. Clearance between punch and die should be

about 20-40% greater than sheet thickness.

Lubrication of die side – to reduce friction in drawing.

Material properties – low yield stress, high work hardening rates, high value of strain ratio of width to thickness

R.

Preparation of test:

1. The sample strips should have a width of 90 mm. However, under some unavailability of specimen 70 mm sized test piece

can be used instead of 90 mm sized one.

2. The center of each impression must be at a distance of 35 mm from the edge of the strip and of at least 70 mm from the

center of the next impression.

3. The thickness of the material to be tested has to be ascertained to the nearest one hundredth part of a millimeter.

4. Prior to testing, both sides of the specimen and the punch itself should be lightly lubricated with graphite grease. If some

other type of lubricant specially indicated in the test report.

Test reports:

The test report should give the following particulars:

1. Method of preparation of specimen.

2. Thickness of sheet or strip to nearest 0.01mm

3. Lubricant used, if other than graphite grease.

4. Number of cups made.

5. Erichsen depth of cup to nearest 0.2 mm individual value being stated.

6. Test temperature.

7. Appearance of specimen after failures. (Surface assessment appearance of fracture etc.)


(i) Explain the purpose of drawing operation?

(ii) Distinguish between ductile and brittle fracture?

(iii) What is LDR?

(iv) Describe the various steps involved in cupping test




Title : Metallography

Objectie : To study the structural characteristics or constitution of a metal or an alloy in relation to its physical

and mechanical properties.

Introduction: There are two examination methods in metallography:

Macroscopy

Microscopy

In macroscopy the examination of the structural characteristics or chemical characteristics of a metal or an alloy is done by the

unaided eye or with the aid of a low- power microscope or binocular, usually under l0x. In microscopy similar examination is

done with the prepared metal specimens, employing magnifications with the optical microscope of from 100 x to as high as 2000

x.

Specimen preparation:

1. Grinding:

A small piece of specimen is cut by a metal-cutting-saw. After cutting operation, burrs on the edges of the specimen should be

carefully removed by a fine file or coarse grinding paper. The silicon carbide grinding papers are held flat in a unit containing

water facility for lubrication purpose. Each unit contains four grades of papers, starting with grade 400 (coarse) and finishing with

grade 1200 (fine). Grinding of the work piece is done by starting with the coarse papers and then continuing with the fine papers.

2. Polishing:

The polishing is done on rotating wheels covered by a special cloth. Alumina is employed as polishing agent. The 1-micron size is

commonly used, but the total polishing time shortened by starting on the 7 or 3 micron grade.The pad should be kept well supplied

with lubricant. The specimen should be held firmly in contact with the polishing wheel, but excessive pressure should be avoided.

During polishing the specimen should be rotated or moved around the wheel so as to give an even polish. The specimen should be

thoroughly cleaned and dried between each wheel.

3. Etching:

Before etching, it is essential to ensure that the polished surface is grease and smear free. If the final polishing has involved the

use of magnesium in the form of an aqueous paste of fine magnesia) or alumina (in the form of an aqueous suspension of fine

alumina), then thorough washing followed by drying off with acetone or alcohol will give a suitable surface, although it must not

be fingered afterwardsAfter each etching, the specimen should be thoroughly washed in running water, followed by drying off

with acetone or alcohol.As a guide the following etchants are commonly used: Alcoholic Ferric Chloride -copper alloys, Mixed

Acids -aluminum alloys Nital (ethyl alcohol+ 2% HN03) -iron and steel, Dilute HCI -zinc alloys.

Microscopical examination

The micro-structural study of a material can provide information regarding the morphology and distribution of constituent phases

as well as the nature and pattern of certain crystal imperfections. Optical metallography is a basic tool of material scientists, since

the equipment is relatively inexpensive and the images can be obtained and interpreted easily. Distribution and morphology of the

phases can be studied and, if their properties are known, a quantitative analysis of the micrographs provides some information

about the bulk properties of the specimen. A limited study of line and surface information’s is also possible with the optical

microscope.

Micro-structural examination can provide quantitative information about the following parameters:

The grain size of specimens

The amount of interfacial area per unit volume

The dimensions of constituent phases

The amount and distribution of phases.


(i) What is metallography? State the stage for metallographic sample preparation?

(ii) Name different etchants used for etching different metals.

(iii) What is Banded Pearlite? How does it form and what is its effect on properties of steels?

(iv) What is the difference between hot working and cold working?

(v) How does the addition of alloying elements change the recrystallization temperature?

(vi) Why is grinding performed before polishing?

(vii) What are the effects of microstructure of steel and CI on their mechanical properties?




Title : Non-Destructive Test

Objective : Observation of presence of surface/ sub-surface cracks using dye penetration (DP) non-destructive

technique.

Introduction:

Non-destructive testing is the use of physical methods which will test materials, components and assemblies for flaws in their

structure without damaging their future usefulness. NDT is concerned with revealing flaws in the structure of a product. It,

however, cannot predict where flaws will develop due to the design itself.

All NDT methods have the following common characteristics:

Procedure:

Step 1: Surface cleaning process:

Solvent cleaning method: On removal of any rust, scale, welding flux, spatter, and in general, inorganic soils, the surfaces to be

inspected shall be cleaned, with solvent cleaner and then finally with a dry lint free cloth.

Step 2: Drying Process:

The drying process shall be accomplished by normal evaporation. Minimum time allowed for drying is 1 minute to ensure that the

cleaning solution has been evaporated prior to application of the penetrant.

Step 3: Application of penetrant:

After the area has been cleaned, dried and the temperature of the surface and penetrant are within the range of 40° F (5° C) to

125° F (52° C), the penetrant shall be sprayed directly to the surface to be inspected by means of aerosol container, so that the

entire area under inspection is completely covered.

Step 4: Excess Penetrant removal:

After the specified dwell time has been elapsed, any penetrant remaining on the surface shall be removed with a dry or slightly

moistened cloth of solvent cleaner, taking care to minimize removal of penetrant from possible discontinuity. Flushing the surface

with solvent cleaner, following the application of the penetrant and prior to developing is prohibited.

Step 4: Drying after removal of excess penetrant:

The drying process shall be accomplished by normal evaporation. Drying time shall only be that necessary to adequately dry the

part.

Step 5: Application of the developer:

Apply the non-aqueous wet developer directly to the area being inspected, by spraying from the aerosol container. The non-

aqueous developer evaporates rapidly at room temperature and therefore does not require the use of a dryer. Areas being inspected

shall be sprayed in such a manner so as to assure complete coverage with a thin, even film of developer. Dipping or flooding parts

with non-aqueous developer is prohibited. Developing dwell time shall not be less than 10 min.,

Examination:

Inspection shall be carried out after the applicable developer dwell time to allow for bleed out of penetrant from

discontinuities into the developer coating. It is good practice to observe the bleed out while applying the developer as an

aid in interpreting and evaluating indications.

Visible penetrant indications can be inspected in natural or artificial white light. A minimum intensity at the inspection

surface of 100 foot candles (1000 Lux) is required.


(i) What is the difference between destructive and non-destructive test?

(ii) What are the major 5 NDT methods?

(iii) For detection of surface weld defects or discontinuities what are the NDT methods commonly used?

(iv) What are the factors affecting the choice of NDT method?




Title : Heat treatment

Objective : Experiments on of carbon steels under different rates of cooling including quenching and testing for

the change in hardness and observing its microstructural changes through metallographic studies.

Introduction:

Heat Treatment is the controlled heating and cooling of metals to alter their physical and mechanical properties without changing

the product shape. Heat treatment is sometimes done inadvertently due to manufacturing processes that either heat or cool the

metal such as welding or forming. The different processes are:

Annealing

Normalizing

Hardening

Tempering

Annealing:

Annealing primarily is the process of heating a metal which is in a metastable or distorted structural state, to a temperature which

will remove the instability or distortion and then cooling it to the room temperature so that the structure is stable and/or strain free.

Normalizing:

This process involves heating the metal above the transformation temperature up to 900º C and cooling from that temperature

adopting the required rate of cooling.

Hardening (By Quenching):

Hardening is performed on metals to obtain desired hardness and structure. It involves:

Heating the metal above transformation temperature, around 900ºC

Holding at that temperature for 15 to 30 minutes per 25mm of cross-section.

Quenching it immediately in a suitable cold medium (brine solution,

Water, oil etc.)

Tempering:

Hardening of metal produces Martensite structure with some retained austenite. The martensite structure makes the metal very

hard and brittle. The retained austenite is unstable and it will change with time. This transformation of retained austenite even at

room temperature leads to distortion of metal. Due to these factors the hardened metal cannot be used as it is. Hence tempering is

carried out on the metals.

Quenching media during the heat treatment:

Water: Water is fairly good quenching medium. It is cheap, readily available, easily stored nontoxic nonflammable smokeless

and easy to filer and pump but with water quench the formation of bubbles may cause soft spots in the metal.

Brine (salt water): Brine is a more severe quench medium than water. Unfortunately it tends to accelerate corrosion problems

unless completely removed. Sodium or potassium hydroxide can be used when very severe quenching is desired and one wishes to

obtain good hardness in low carbon steels.

Oil: When slower cooling rate is desired oil quenches can be employed.

Air: Low alloy steels in light sections and high alloy steels may be successfully hardened by means of compressed air or still air.

Result:

To find the hardness of the given treated and untreated steel specimens by conducting the various hardness test


(i) What is heat treatment?

(ii) What are needs for performing annealing and normalizing on metals?

(iii) Name some components which are produced by case hardening process. Where do we apply this process?

(iv) Why does the hardness of steel increase after quench hardening?

(v) What are the melting points of steel and cast iron? Which factor influences their melting point?

(vi) Derive the formula to calculate BHN.

http://turkishengineering.blogspot.in/2007/05/quenching-media-during-heat-treatment.html

department of production engineeringhithaldia.ac.in/cm/pe/lab/06. me 493.pdfweighted pendulum hammer...

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