Material Science & Testing Lab Manual

Transcription

1 Material Science & Testing Lab Manual LAB CODE-RME 351 Prepared by: G L Bajaj Institute of Engineering and Technology Greater Noida

2 RME-351 Material Science & Testing Lab List of Experiments Minimum Eight experiments to be performed (As per syllabi) S. No. List of Experiments Page No. 1. To measure the toughness of a given specimen by IMPACT testing machine 2. To measure the spring index of closed helical spring. 3. To measure the modulus of rigidity by torsion test. 4. To determine the Ultimate Tensile strength of Mild steel sample by U.T.M Machine. 5. To make a plastic mould for small metallic specimen. 6. To measure the hardness of given specimen by Rockwell hardness tester. 7. To study Heat treatment processes (Annealing, Normalizing, Hardening) of steel specimen. 8. Study of different engineering materials. 9. Study of deflection (y) of simply supported beam and calculate the value of Young s modulus of beam. 10. Prepare the specimen for micro structural examination-cutting, grinding, polishing, etching. Experiments beyond recommendation of AKTU, Lucknow 1.

3 TABLE OF CONTENTS Syllabus Practical Outcomes Mapping of Program Outcomes with Practical Outcomes Session Plan Laboratory policies & Report format Evaluation sheet Experiment and viva-voce questions.

4 Study & Evaluation scheme S. No. Subject Code Name of the Subject Period Evaluation Scheme Sessional Assessment L T P C T T A Total ESE Subject Total Credit 1 NME-351 Material Science and Testing Lab

5 Practical Outcomes (PrO): S. No. Outcomes 1. Students will be able to acquire the basic knowledge about the Mechanical properties of materials by using different mechanical testing machine such as Torsion testing machine, Rockwell hardness tester, Spring index testing machine and UTM machine. 2. Students will be able to acquire the knowledge regarding life of a machine component by using torsion testing machine and fatigue testing machine. 3. Students will be able to acquire the knowledge regarding polishing operation of a small metallic sample. 4. Students will be able to acquire the knowledge of different engineering materials properties and its industrial applications.

6 Mapping of Program Outcomes with Practical Outcomes S. No. PrO/PO PO 1 PO 2 PO 3 PO 4 PO 5 PO 6 PO 7 PO 8 PO 9 PO 10 PO 11 PO : Slight (low) 2: Moderate (Medium) 3: Substantial (High) - No correlation

7 COURSE: B. Tech. (Mechanical Engineering) Session Plan TITLE: Material science and testing lab CREDIT: 1 LOCATION: Lab No. ME-11 PREREQUISITES COURSES: Engg. Mechanics, Engg. Chemistry PREREQUISITIES BY TOPIC: S. No. List of Experiments Pre requisites 1. To measure the toughness of a given specimen by IMPACT testing machine 2. To measure the hardness of given specimen by Rockwell hardness tester. 3. To measure the spring index of closed helical spring. Engg. Mechanics 4. To measure the modulus of rigidity by torsion test. 5. To prepare a plastic mould for small metallic specimen. 6. To study Heat treatment processes (Annealing, Normalizing, Hardening) of steel specimen. 7. To determine the Ultimate Tensile strength of Mild steel sample Engg. Chemistry by U.T.M Machine. 8. Study of different engineering materials. TEXT BOOK(S) AND/OR REQUIRED MATERIALS: 1. (1) Callisters Materials Science and Engineering, by William D. Callister, Jr, (Adopted by R. Balasubramaniam), Wiley India Pvt. Ltd. (2) Lab manuals WEB RESOURCES:.

8 S.No. Name of Experiment Practical Outcomes To measure the toughness of a given specimen by IMPACT testing machine 1 2 To measure the hardness of given specimen by Rockwell hardness tester. 3 To measure the spring index of closed helical spring. Students will be able to acquire the basic knowledge about the Mechanical properties of materials by using different mechanical testing machine such as Torsion testing machine, Rockwell hardness tester, Spring index testing machine and UTM machine. 4 To measure the tensile strength of given specimen by UTM. 5 6 To measure the modulus of rigidity by torsion test. To study Heat treatment processes (Annealing, Normalizing, Hardening) of steel specimen. Students will be able to acquire the knowledge regarding life of a machine component by using torsion testing machine. 7 To prepare a plastic mould for small metallic specimen. Students will be able to acquire the knowledge regarding polishing operation of a small metallic sample. 8 Study of different engineering materials. Students will be able to acquire the knowledge of different engineering materials properties and its industrial applications.

9 Internal Evaluation Method S.No. Item % 1. Attendance In lab performance Record Post lab Viva-voce 10

10 LABORATORY POLICIES AND REPORT FORMAT 1. Lab reports should be submitted on A4 paper. Your report is a professional presentation of your work in the lab. Neatness, organization, and completeness will be rewarded. Points will be deducted for any part that is not clear. 2. The lab reports will be written individually. Please use the following format for your lab reports. a. Cover Page Include your name, Subject Code, Subject title, Name of the College b. Evaluation Sheet Gives your internal mark split up c. Index Sheet Includes the name of all the experiments d. Experiment documentation It includes experiment name, date, objective, flowchart, formulae used, Model calculation, problem solution. e. Post lab question Should be written after completing the experiments. 3. Your work must be original and prepared independently. However, if you need any guidance or have any questions or problems, please do not hesitate to approach your staff in charge. The students should follow the dress code in the Lab session. 4. Labs will be graded as per the following grading/marks policy: 5. Reports Due Dates: Reports should be submitted immediately after next week of the experiment. A late lab report will have 20% of the points deducted for being one day late. If a report is 3 days late, grade/marks of D/0 will be assigned..

11 Experiment No.:1 Object:- (i) To Determine the Impact strength of Mild Steel specimen by (Charpy test) (ii) To measure the toughness of a given specimen. Apparatus Required:- S. No. EQUIPMENT AND TOOLS REQUIRED Material required 1. Impact testing machine A mild steel specimen having a groove of 45 & 2 mm depth Brief Theory:- Fig: 1 Charpy test setup (a) hammer position (b) specimen position An Impact test signifies toughness of material that is ability of material to absorb energy during plastic deformation. Static tension tests of unmatched specimens do not always reveal the susceptibility of a metal to brittle fracture. This important factor is determined by impact test. Toughness takes into account both the strength and ductility of the material. Several engineering materials have to withstand impact or suddenly applied loads while in service. Impact strengths are generally lower as compared to strengths achieved under

12 slowly applied loads. Of all types of impact tests, the notch bar tests are most extensively used. Therefore, the impact test measures the energy necessary to fracture a standard notch bar by applying an impulse load. The test measures the notch toughness of material under shock loading. Values obtained from these tests are not of much utility to design problems directly and are highly arbitrary. Still it is important to note that it provides a good way of comparing toughness of various materials or toughness of the same material under different condition. This test can also be used to assess the ductile brittle transition temperature of the material occurring due to lowering of temperature. Procedure:- 1. With the striking hammer (pendulum) in safe test position, firmly hold the steel specimen in Impact testing machines vice in such a way that the notch faces as the hammer and is half inside and half above the top surface of the vice. 2. Bring the striking hammer to its top most striking position unless it is already there, and lock it at that position. 3. Bring indicator of the machine to zero, or follow the instructions of the operating manual supplied with the machine. 4. Release the hammer. It will fall due to gravity and break the specimen through its momentum, the total energy is not absorbed by the specimen. Then it continues to swing. At its topmost height after breaking the specimen, the indicator stops moving, while the pendulum falls back. Note the indicator at that topmost final position. 5. The specimen is placed on supports or anvil so that the blow of hammer is opposite to the notch. Calculations:- Material of test specimen Mild Steel Type of notch V notch Dimension of specimen 10x10x55 (mm 3 ) Velocity of striking m/sec Angle of drop of pendulum 120

13 Specimen no Maximum impact energy of pendulum (Joule) Energy absorbed (Joule) Average value of impact strength = Results:- The energy absorbed for Mild Steel is found out to be Joules. Precautions:- 1. Measure the dimensions of the specimen carefully. 2. Locate the specimen (Charpy test) in such a way that the hammer, strikes it at the middle. 3. Note down readings carefully. Conclusions of the present work (what new you have learnt in today s experiment): Viva-voce Questions 1. Define toughness? 2. Define strain energy? 3. Define Impact load?

14 Experiment No.:2 Object: - To determine the spring index i.e. loads (tensile/compressive) required for unit deflection (elongation/compression) of a helical spring. Apparatus Required:- S. No. EQUIPMENT AND TOOLS REQUIRED Material required 1. Spring index testing machine. Vernier caliper Micrometer Spring specimen Brief Theory:- Spring index s (or spring rate or spring stiffness) is defined as the load P that causes unit deflection δ in the spring. This deflection is in the form of contraction in a compression spring and in the form of extension in a tension spring. Thus S = P/δ Spring index is an important parameter in selection of spring for a particular use. It is expressed in N/mm or Kg/mm etc. The nature of load v/s deflection curve decides whether the behavior of spring is linear or non-linear. Mostly close- coiled helical spring have nature. Deflection of a close-coiled helical can be evaluated analytically by a derived formula given below. Δ = (8PD 3 n)/ (Gd 4 ) Where P is the axial load (tensile or compressive), D is mean coil diameter of the spring, n is number of coils, G is modulus of rigidity of spring material, and d is the spring wire diameter. In an experiment if δ obtained for different loading, the shear modulus G can be determined experimentally by above formula. The maximum shear stress Ț included in the spring can be determined by: Ț = (8PD 2 )/ (πd 4 )

15 Procedure:- 1. By using the micrometer measure the diameter of the wire of the spring. 2. By using the Vernier caliper measure the diameter of the spring coil. 3. Count the number of turns. 4. Insert the spring testing machine and note the corresponding axial deflection in tension or compression. 5. Increase the load and take the corresponding axial deflection reading. Calculations:- Diameter of compression spring coil, D, mm = Diameter of compression spring coil, d, mm = Number of turns in compression spring, n = For compression spring: Run Number Load, P (Kg) Deflection, δ (mm) For Tension spring: Run Number Load, P (Kg) Deflection, δ (mm) Results:- Spring index of helical spring is. N/mm Precautions:- 1. Measure the dimensions of the specimen carefully. 2. Measure the deflection of spring accurately for the corresponding value of tensile/compressive load.

16 3. Note down readings carefully. Conclusions of the present work (what new you have learnt in today s experiment): Viva-voce Questions 1. Define Tensile/Compressive load? 2. Define spring index? 3. Define modulus of rigidity?

17 Experiment No.:3 Object: - To Determine the Modulus of rigidity of Mild Steel specimen by (Torsion test) Apparatus Required:- S. No. EQUIPMENT AND TOOLS REQUIRED Material required 1. A Torsion testing machine. Twist meter for measuring angles of twist. A steel rule and calipers or micrometer. Mild Steel specimen Brief Theory:- Fig (4.1) Torsion testing machine A Torsion test is quite instrument in determining the value of modulus of rigidity (ratio of shear stress to shear strain) of a metallic specimen. The value of modulus of rigidity can be found out through observation made during the experiment by using the torsion equation. T/I P = Cα/l

18 Where, T = torque applied I P = Polar moment of inertia C = Modulus of rigidity α = Angle of twist (radians), and l = gauge length Procedure:- 1. Select the driving dogs to suit the size of the specimen and clamp it in the machine by adjusting the length of the specimen by means of a sliding spindle. 2. Measure the diameter at about three places and take the average value. 3. Choose the appropriate range by capacity change lever. 4. Set the maximum load pointer to zero. 5. Set the protector to zero for convenience and clamp it by means of knurled screw. 6. Load the machine in suitable increments. 7. Then load out to failure as to cause equal increments of strain reading. Calculations:- Material of test specimen Mild Steel Dimension of specimen 10x10x55 (mm 3 ) Gauge length of the specimen = Diameter of the specimen = Polar moment of inertia = Torque (T) Angle of twist (α) in radians Note: Angle of twist is measured in degrees. It should be converted into radians {α x (π/180)}.

19 Average value angle of twist = Results:- Modulus of rigidity of mild steel rod is N/mm 2 Precautions:- 1. Measure the dimensions of the specimen carefully. 2. Measure the Angle of twist accurately for the corresponding value of Torque. 3. Note down readings carefully. Conclusions of the present work (what new you have learnt in today s experiment): Viva-voce Questions 1. Define Modulus of rigidity? 2. Define angle of twist? 3. Define polar moment of Interia?

20 Experiment No.:4 Object: - To determine the Ultimate Tensile strength of Mild steel sample by U.T.M Machine. Apparatus Required:- S. No. EQUIPMENT AND TOOLS REQUIRED Material required 1. Universal testing machine Mild Steel Vernier caliper. specimen Brief Theory:- For the study of behavior of engineering materials under tensile load, a test specimen is required to be prepared. The shape of the test specimen is normally a right circular cylinder. The shape of the test specimen is normally a right circular cylinder. The ends of the test specimen to be gripped should suit the holders of the specimen of the test machine. For ductile material plain ends and for brittle materials threaded ends may be used. In general the diameter (d) of the gauge portion should not be less than 4mm. The test specimen is loaded axially, which responds to a applied axial load in the form of axial elongation with simultaneously lateral reduction up to certain value of load the stress included in the test specimen is directly proportional to the strain. If the material is stressed beyond the yield point, a point will come where the sample will be stressed maximum i.e maximum stressed is applied. This point is known as ultimate point and stress at that point is known as Ultimate stress point. Ultimate stress: The ratio of maximum load to the original cross-sectional area of a bar is called ultimate stress. Procedure:- 1. Measure the gauge length and diameter of the test specimen 2. Insert the suitable jaws in the grips and select a suitable load scale on the Universaltesting machine. 3. Start the machine and record the readings for different values of loads.

21 4. Continue applying load and record the extension values corresponding to the load till Calculations:- the test specimen ruptures. Material of test specimen Mild Steel Dimension of specimen 10x10x55 (mm 3 ) Gauge length of the specimen = Diameter of the specimen = 10 mm S.No. Load (W) (N) Ultimate Tensile Strength (MPa) Results:- Ultimate Tensile strength (MPa) = Precautions:- 1. There should not be any scratch mark in the gauge length portion of the specimen. 2. Rate of loading should not high. 3. Reading of load must be recorded very carefully. Conclusions of the present work (what new you have learnt in today s experiment): Viva-voce Questions 1. Define Stress? 2. Define Ultimate strength? 3. Define Hooks law?

22 Experiment No.:5 Object: - To make a plastic mould for small metallic specimen. Apparatus Required:- S. No. EQUIPMENT AND TOOLS REQUIRED Material required 1. Mounting press specimen Dies or mould with piston. One pair of asbestos hand gloves to hold the hot specimen Granular plastic. Brief Theory:- Polishing of a small metallic specimen or of a specimen in the form of thin foil is difficult. For convenience in handling during polishing operation, they are required to be attached to mounted on suitable plastic mould. This also helps in edge retention during polishing. The plastic mould is prepared from granular plastic by heating and pressure application. Metallic mould are required to hold plastic grains. They have to be of different shapes and sizes so as to get the final product (plastic mould) of similar shapes and sizes. Procedure:- 1. First of all the silicon-grease is applied on inner surface of the mould and on outer surface of the piston, for easy and smooth sliding of piston inside the mould. 2. Now the plastic grains are put in the mould and thin/foil metallic specimen is placed on it. The mould is encased by the piston. 3. The mould-piston assembly is placed in the heater and tightened. 4. Plastic grains normally melt below 100 degree Celsius. Its correct melting temperature can be recorded by mercury thermometer.

23 5. Heater plugs are disconnected to allow cooling of thus prepared plastic mould. The cooling is done down up to room temperature. 6. The cooled set-up is pressed again by jack to take out the piston and solidified mould. Results:- The plastic mould along with the metallic specimen is ready for further action i.e. polishing. Precautions:- 1. Carefully wear hand gloves to hold the specimen. 2. Note down readings carefully. Conclusions of the present work (what new you have learnt in today s experiment): Viva-voce Questions 1. Define mould? 2. Define casting? 3. Define plastic material?

24 Experiment No.:6 Object: - To determine the hardness of Mild Steel specimen by Rockwell hardness tester. Apparatus Required:- S. No. EQUIPMENT AND TOOLS REQUIRED Material required 1. Rockwell hardness testing machine Steel ball indenter/penetrator Mild steel specimen Brief Theory:- Rockwell hardness test uses a direct reading instrument based on the principle of differential depth measurement. The test is performed by slowly raising the specimen against the indenter until a fixed minor load has been applied. This is indicated on the dial gauge. Then major load is applied through a loader lever system. After the dial pointer comes to rest the major load is removed and, with the minor load still acting, the Rockwell hardness number is read on the dial gauge, since order of numbers is reversed on the dial gauge. The minor load is 10 Kg on a normal tester and major loads are usually 60, 100 and 150 Kg. On the normal scale. A variety of indentures and levels may be used and each combination determines a particular Rockwell scale. Indentures include hard steel ball 1/16, 1/8, ¼, ½ inch diameter and a 120 degree conical diamond point. Procedure:- 1. Insert ball of dia. D in ball holder of the machine. 2. Make the specimen surface clean by removing dust, dirt, oil and grease etc. 3. Make contact between the specimen surface and the ball by rotating the jack adjusting wheel.

25 4. Push the required button for loading. 5. Pull the load release the levers wait for minimum 15 seconds. The load will automatically apply gradually. 6. Remove the specimen from support table and locate the indentation so made. 7. Repeat the entire operation for three times. Calculations:- For Measurement of Rockwell hardness number Serial no. Penetrator used Minor Load (Kgf) Major load (Kgf) Total load (Kgf) Rockwell hardness no. (HRC) Results:- Rockwell hardness of the given mild steel specimen is HRC Precautions:- The specimen should be clean properly. Conclusions of the present work (what new you have learnt in today s experiment): Viva-voce Questions

26 1. Define Hardness? 2. Define Unit of Rockwell hardness? 3. What is the effect of hardness on carbon reinforcement in sample?

27 Experiment No.:7 Object: - To perform the Heat treatment process and compare the hardness of the specimen. Apparatus Required:- S. No. EQUIPMENT AND TOOLS REQUIRED Material required Electrically heated temperature controlled Oven. Cooling bath or bucket. Job holding tong. Rockwell hardness testing machine. Steel sample Brief Theory:- Properties of metals and alloys can be changed by heating followed by cooling under definite condition to make them suitable for specific applications. Accordingly steel can be hardened to resist cutting action and prevent abrasion. The rate of cooling and manner of cooling are important factors in heat treatment process. Heat treatment processes increases the hardness, tensile strength as well as ductility of material. In annealing processes it is heated up to about 700 degree Celsius and furnace cooled. In normalizing it is heated between 800 degree Celsius to 950 degree Celsius and slowly cooled in air. In hardening process it is quenched in different medium like water and oil. Fast cooling is being observed in case of water quenching. Procedure:- 1. Heat the specimen about 950 degree Celsius. 2. Maintain it at this temperature for about 10 minutes. 3. Now take it out of the oven and suddenly dip in cooling bucket. This is quench hardening process during which Martensite will form. The surface will become much harder than earlier. 4. When the job cools, take it onto Rockwell hardness testing machine and determine the hardness in usual manner.

28 Results:- 1. The observed Rockwell hardness of heat treated steel is HRC (water as quenching medium). 2. The observed Rockwell hardness of heat treated steel is HRC (oil as quenching medium). Precautions:- 1. The oven is electrically heated. Therefore take care to avoid burning from heat of the furnace and shock due to electricity. 2. Do not hold the hot specimen by hand. Always use tongs to hold it. 3. The handle of tong should be plastic insulated. Conclusions of the present work (what new you have learnt in today s experiment): Viva-voce Questions 1. Define Heat treatment process? 2. Define annealing, normalizing and hardening processes? 3. Explain how grain growth is a strong function of temperature? 4. Explain by which heat treatment process stresses of sample can be removed?

29 Experiment No.:8 Object: - Study of different engineering materials. Table: 1 containing different engineering materials with their Mechanical and Electrical properties Different Engineering materials Aluminum Nomenclature Structure Mechanical properties Electrical properties Duralium Magnesium Zinc Copper Tin Brass Bronze Chromium Nickel

30 Experiment No.:9 Object: - To study the effect of deflection on simply supported beam, compare the actual measurement of deflection with dial gauge to the calculated one and evaluate the value of young s modulus of beam. Apparatus Required:- S. No. EQUIPMENT AND TOOLS REQUIRED Material required Steel beams Dial gauge Weight pan Steel sample Brief Theory:- The deflection of a beam, y, will depend on many factors such as: - The applied load F (F=m g). The span L. The width of the beam b, and its thickness h. Other factors such as position, method of loading, the material of which the beam is made will also influence the deflection. If we wish to find the relationship between y and one of the possible variables it is necessary to keep all the other possible variables constant throughout the experiment. y = F*L3 48*E*I

31 L = length of beam (mm) y = deflection of beam (mm) F = force (N) E = Young's Modulus (N/mm 2 ) I = moment of inertia of beam (mm 4 ) Procedure:- 1. Mount the steel beam as simply support condition and placed a dial gauge indication at desired position over it supports properly and connect the plunger of dial gauge indicator to the middle support of beam. 2. Apply load on the weight pan increasingly and note the corresponding deflection value. Calculation:- L (length of beam) = (mm) Y (length of beam) =. (mm) Moment of Inertia (I)=.. (mm 4 )

32 S.No. Width b (mm) Length L (mm) Deflection y (mm) Young s modulus (MPa) Results:- 1. Experimentally observed value of Deflection of simply supported beam =.(mm). 2. Theoretically observed value of Deflection of simply supported beam =. (mm). 3. Observed value of Young s modulus of elasticity = (MPa). Precautions:- 1. Reading on dial indicator should be noted properly. 2. Placed the dial indication at desired location on the simply supported beam. Conclusions of the present work (what new you have learnt in today s experiment): Viva-voce Questions 1. Define young modulus of beam 2. Define moment of inertia. 3. Define simply support beam 4. Least count of dial indicator.

33 Experiment No.:10 Object:-Prepare the specimen for micro structural examination-cutting, grinding, polishing, and etching. Apparatus Required:- S. No. EQUIPMENT AND TOOLS REQUIRED Material required Grinding machine Abrasive paper Etchant Mild steel sample Brief Theory:- Metallography is the study of the microstructure of metals and alloys by means of microscopy. It is an art and science of preparing, interpreting, and analyzing microstructures in materials, to better understand materials behavior and performance. The method is used for the evaluation of metallic materials in the various industries, including the aerospace industry, the automotive industry and parts of the construction industry. It is also used for process control including the examination of defects that appear in finished or partly finished products, as well as the studies of parts that have failed during service. It is an important branch of the Metallurgical Engineering. A well prepared metallographic specimen is: a. A representative sample b. Sectioned, ground and polished so as to minimize disturbed or flowed surface metal caused by mechanical deformation, and thus to allow the true microstructure to be revealed by etching. c. Free from polishing scratches and pits and liquid staining d. Flat enough to permit examination by optical microscope Various steps involved in the specimen preparation, and the significance of each step: Many steps in the preparation of metallographic specimens described here are also applicable in other types of metallographic studies, such as electron microscopy, micro hardness testing, quantitative measurement of constituents of structures, and electron microprobe analysis. Preparation of metallographic specimens generally requires five major operations: a. Sectioning b. Mounting (which is necessary when the sample cannot be held properly due to its Shape and/or size, while polishing) c. Grinding

34 d. Polishing e. Etching Procedure: 1. Start the grinding wheel motor and wait for it to come up to speed. 2. Gently lower the specimen to the center of the wheel. Once it is down apply pressure and slowly move it to approximately half way to the edge of the wheel. 3. After grinding wheel polishing go for abrasive paper polishing. 4. After that use proper etchant for microstructural examination..calculation:- Polishing pressure = Etchant name = Abrasive paper grit size =. Result:- The mirror like polished specimen is ready for microstructural examination. Precautions:- 1. Make sure your specimen is suitable for polishing/grinding. The polishing surface must be flat and all edges (top and bottom) must be rounded (not sharp). Otherwise, there is a good chance that the abrasive paper will grab the specimen and pull it from your hand. 2. Make sure your grinding paper is mounted properly. It should not be able to slip and all air bubbles must be removed. 3. Make sure the rim is in place. Never operate the polisher/grinder without the rim in place. Conclusions of the present work (what new you have learnt in today s experiment): Viva-voce Questions

35 1. Define Etchant. 2. Define grain. 3. Define grit size. 4. What is Grain boundary?