Assignment: Lab report Charpy Impact

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Assignment: Lab report Charpy Impact ORDER NOW FOR CUSTOMIZED AND ORIGINAL ESSAY PAPERS ON Assignment: Lab report Charpy Impact Hi, The all files have been uploaded of related lab report. Assignment: Lab report Charpy Impact Steps of report: 1- Abstract 2- Introduction 3- Methods 4- Analysis 5- Discussion attachment_1 attachment_2 attachment_3 attachment_4 Widener University School of Engineering Department of Mechanical Engineering ME 303 – Mechanical Measurements Laboratory I Experiment #5 CHARPY IMPACT TEST I. INTRODUCTION One of the methods to measure fracture energy (toughness) of a given material is an impact test, such as, for example, the Charpy impact test. In this test, a pendulum swings through its arc, strikes, and breaks a standard specimen. After impact, the difference in potential energy of the pendulum is equal to the fracture energy of the specimen. This method is also used in the TE15 apparatus shown in Figure 1(a). Referring to Figure 1(b), a pendulum starts at a standard elevation h1, swings through its arc, strikes and breaks a standard specimen, then reaches a lower final elevation h2. Knowing the initial and final elevation of the pendulum, the difference in potential energy can be obtained. ?V=mg (h1 -h2) (1) where h1 = r(1 + sin(? – 90) )), h2 = r(1 + sin(? – 90) ), and the value mgr for the TE15 apparatus is mgr = 2.34 Nm. However, the energy of impact is read directly from the scale of the tester in Joules (Nm). (a) (b) Figure 1(a) The TE15 Apparatus; (b) Charpy Impact Test II. OBJECTIVES – Familiarization with the use of the Charpy impact testing machine. – Familiarization with standardized specimens. – Determination of impact energy required to fracture standardized specimens of different materials. – Correlation of impact energy with deformation of individual specimens. – Correlation of impact energy with yield and ultimate strengths of individual specimens. III. EQUIPMENT TE 15 Charpy Impact Testing Machine, Charpy test specimens, blocks and hacksaw Calipers (see Figure 1(a)) IV. MAKING SPECIMENS 1 In this experiment, you will test several standard v-notched Charpy specimens. Each specimen has dimensions which conform to Charpy standards. The TE15 apparatus is supplied with rods of different material. 1. Cut precise 38 mm specimen lengths from the rods as shown in Figure 2(a). 2. Clamp each new specimen into the specimen block, using a hexagon tool to tighten the grub screw in the side of the block as shown in Figure 2(b). 3. Put the black cutting block over the specimen and bolt it to the specimen block as shown in Figure 2(c). (a) (b) (c) Figure 2(a) Cut Specimen lengths at 38 mm; (b) Fit Specimen to Block; (c) Place the Cutting Block over and onto the Specimen and block (a) (b) Figure 3(a) The Correct Cutting Action; (b) The Wrong Cutting Action 4. Put the assembly into a suitable vice and use the hacksaw (supplied) to cut a notch into the specimen. Cut the specimen with a flat action, across the dowels as shown in Figure 3(a). Do not ‘rock’ the saw or cut at an angle as shown in Figure 3(b). Stop when you reach the level of the dowels, the cutting note will change and the saw will slide easily. 5. Remove the black cutting block. The notch in the specimen should accurately face into the direction of impact. 6. The specimen and block are now ready for test. V. LABORATORY PROCEDURE 1. Remove the specimen block from the apparatus. 2. Place a new 38 mm long specimen in the specimen block and cut a notch as described in Section IV. The notch must face into the direction of impact. 3. Create a table of results similar to Table 1. 4. Measure the room temperature and the exact diameter of each new specimen before use. 5. Connect the Instrumentation box shown in Figure 4 to a suitable mains supply. Assignment: Lab report Charpy Impact The Instrumentation Box will display ‘TecQuipment Ltd’ then ‘TE15’ then ‘Energy Absorbed in Fracture’, and finally ‘Ready to Arm’. 2 Figure 4 The TE15 Instrumentation Box 6. Allow the pendulum to come to a complete rest just above the specimen shear block, a square black indicator should illuminate in the top right- hand corner of the display, next to ‘Ready to Arm’. If it does not, then the apparatus is not level. Re adjust the bench to make the apparatus level. 7. Use the lifting control on the front of the apparatus to move the pendulum up to its starting position at the top left. An electromagnet will energize and hold the pendulum in place. The Instrumentation Box will display the words ‘Load Specimen Press Release’. 8. Insert the specimen and block into its place under the shear block at the base of the apparatus, making sure it is fully inserted (see Figure 5). Table 1 Experimental Results Impact Energy Material Diameter (mm) ? ? (Joules) (Eq. (1)) Impact Energy (Joules) (from the scale) Average Impact Energy (Joules) Type of Failure Aluminum Brass Copper Mild Steel Date: Ambient Temperature: Energy Lost to Friction and Air Resistance: 3 9. Make sure all persons are standing clear of the apparatus and press the release button. 10. Record the readings displayed by the Instrumentation Box. 11. Wait for the pendulum to stop swinging before preparing the next specimen. Test each material three times, recording the results and produce an average for the energy loss to fracture. 12. On completion of the test, try one more swing without a specimen in place and determine how much energy is lost to friction and air resistance. Figure 5 Push the Specimen Block fully into Place in the Shearing Block VI. RESULTS The impact energy from the Charpy test correlates with the area under the total stress-strain curve (i.e. toughness). For any material test, the area under the stress-strain curve is related to the energy absorbed by the material, the larger the area, the greater the amount of energy absorbed. This is also an indication of the material toughness. As shown in Figure 6, material A has a high tensile strength, (indicated by the high yield point) but low ductility, material B has a lower tensile strength and medium ductility and material C has much lower tensile strength and high ductility. The area under materials B and C are similar, and both materials will show similar impact properties and toughness. Material A has very little ductility, despite its high tensile (yield) strength and will show a much lower toughness than materials B and C.This indicates that a tough material must have both high strength and ductility. Figure 6 The Stress Strain Relationship 4 Although this is frequently so, the impact data are sensitive to test conditions. For instance, increasingly sharp notches can give lower impact energy values due to the stress concentration effect at the notch tip. Test temperature is also a factor. Face-centered cubic (fcc) alloys generally show ductile fracture modes in Charpy testing, and hexagonal close-packed (hcp) alloys are generally brittle (Figure 7). Figure 7. Impact energy for a ductile fcc alloy (copper C23000-061, “red brass”) is generally high over a wide temperature range. Conversely, the impact energy for a brittle hcp alloy (magnesium AM100A) is generally low over the same range. [3] However, body-centered cubic (bcc) alloys show a dramatic variation in fracture mode with temperature. In general, they fail in a brittle mode at relatively low temperatures and in a ductile mode at relatively high temperatures. Figure 8 shows this behavior for two series of low-carbon steels. The ductile-to-brittle transition for bcc alloys can be considered a manifestation of the slower dislocation mechanics for these alloys compared to that for fcc and hcp alloys. (In bcc metals, slip occurs on non-close-packed planes.)Assignment: Lab report Charpy Impact Increasing yield strength combined with decreasing dislocation velocities at decreasing temperatures eventually lead to brittle fracture. The microscopic fracture surface of the high-temperature ductile failure has a dimpled texture with many cuplike projections of deformed metal, and brittle fracture is characterized by cleavage surfaces (Figure 8). Figure 8. (a) Typical dimpled texture of ductile fracture surface; (b) Typical cleavage texture of brittle fracture surface Near the transition temperature between brittle and ductile behavior, the fracture surface exhibits a mixed texture. The ductile-to-brittle transition temperature is of great importance. The alloy that exhibits 5 this behavior loses toughness and is susceptible to catastrophic failure below this transition temperature. Because a large fraction of the structural steels is included in the bcc alloy group, this is a design criterion of great importance. The transition temperature can fall between roughly 100 and + 100°C depending on alloy composition and test conditions. Several disastrous failures of Liberty ships occurred during World War II because of this phenomenon. Some literally split in half. Low-carbon steels that were ductile in room-temperature tensile tests became brittle when exposed to lower-temperature ocean environments. Figure 9 shows how alloy composition can dramatically shift the transition temperature. Such data are an important guide in material selection. – VII. REPORT Your laboratory report should include 1. The experiment description (with stated Objectives), 2. Data and results (tabulated individual and average values for each material, type of failure comments on fractured surface (Table 1)), 3. Discussion of your results, including comments regarding the correlation of impact energy with type of failure and strengths for each specimen. Figure 9. Variation in ductile-to-brittle transition temperature with alloy composition. (a) Charpy V-notch impact energy with temperature for plain-carbon steels with various carbon levels (in weight percent). (b) Charpy V-notch impact energy with temperature for Fe-Mn-0.05 C alloys with various manganese levels (in weight percent). [2] REFERENCES 1. Metals Handbook, 9th ed., Vol. 2, American Society for Metals, Metals Park, Ohio, 1979. 2. Metals Handbook, 9th ed., Vol. 1, American Society for Metals, Metals Park, Ohio, 1978. 6 Material Aluminum Brass Copper Mild Steel Diameter Inches a b Energy Joules Degrees Degrees 100 91 0.36 100 91 0.36 100 88 0.48 100 91 0.36 100 91 0.36 100 88 0.48 100 81 0.77 100 87 0.53 100 82 0.73 100 100 100 100 83 68 38 43 0.69 1.28 2.25 2.11 100 45 2.06 100 31 2.41 100 68 1.28 100 73 1.09 100 54 1.78 100 67 1.32 100 63 1.46 Type of Failure Fracture Fracture Fracture Fracture Fracture Fracture Fracture Fracture Fracture Fracture Bending Bending Bending Bending Bending Bending Bending Bending Bending Bending … Get a 10 % discount on an order above $ 100 Use the following coupon code : NURSING10