Team-19_Lab-2_Charpy_Impact_Test

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CHARPY IMPACT TEST OF 1018 STEEL AT DUCTILE-TO-BRITTLE TRANSITION TEMPERATURES Engineering Materials I MCG 2360[B] Laboratory Report Lab 2: Charpy Impact Test Team #19 Student Number Name 300241579 Gautam Mehta 300298485 George Lai 300298002 Phone Thant Htet 300293604 Ryan Gorodezky Experiment Date: November 3, 2023 Date Submitted: November 17, 2023 Professor: Dr. Nafisa Bano TA: Behrang Asghari Shirvani Faculty of Engineering Department of Mechanical Engineering 2023

1 Abstract In this experiment, the Charpy Impact test was conducted in order to determine the impact energy (K) absorbed by the Steel samples at 3 different temperatures. The Charpy impact test consists of a hammer attached to a rod which swings from an initial height creating a pendulum motion. The impact energy depends on gravity, mass, and the initial/maximum height of the hammer. The impact energy can then be used to calculate the impact toughness, which is proportional to the cross-sectional area of the sample. The calculation requires dividing the impact energy with the area. The three identical samples of 1018 Steel were tested at different temperatures of -80°C, 21°C (Room temperature), and 100°C. These samples are 55x10x10 mm and are fabricated with this experiment in mind to include a Charpy V-notch design, that is in line with ASTM E-23 Standard. A 2 mm deep cut at the midline at an angle of 45 degrees is included. The ‘V - notch’ focuses the energy and promotes a consistent fracture result. The main purpose of this lab is to show how the mechanical properties of a metal can be altered by temperature. A major factor to consider when analyzing the results of this lab is whether the sample displays brittle or ductile behavior when fractured. The transition between brittle and ductile happens at the transition temperature, where the energy absorbed on impact is quickly increasing. By assumption, the sample at -80°C will absorb less energy and display a brittle fracture, whereas it is predicted that the sample at room temperature and 100°C will display a Ductile fracture, with the 100°C sample absorbing more energy.

2 1. Table of Contents Abstract ........................................................................................................................................... 1 1. Introduction ............................................................................................................................. 1 1.1 Objective .......................................................................................................................... 1 1.1.1 Equipment and Materials .......................................................................................... 1 2. Methodology ........................................................................................................................... 2 3. Results and Discussion ........................................................................................................... 2 3.1 Results .............................................................................................................................. 2 3.2 Charpy Impact test and material structure variation with temperature ............................ 6 3.3 Discussion ........................................................................................................................ 6 3.4 Sample Calculations ......................................................................................................... 9 4. Conclusion ............................................................................................................................ 10 References ..................................................................................................................................... 11

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LAB 2: CHARPY IMPACT TEST 1 1. Introduction The impact test is a high-strain rate assessment of the material properties where a hammer attached to an arm will drop in a pendulum motion and impact the test specimen. The critical part of this experiment is the samples which will be prefabricated into the Charpy V-notch design which is a 55x10x10 mm rectangular specimen with a 2 mm deep cut at the midline at an angle off 45 degrees (the sample dimensions should follow the ASTM E-23 standard). This notch will focus the energy during the experiment. This lab report will compare the different impact strengths and energy absorbed on impact by three specimens of ASTM E-23 standard 1018 Steel at three different temperatures of 100°C, room temperature at 21°C and -80°C. The report will also illustrate how the mechanical properties of a sample can be affected by the temperature shown in ductile-brittle transition temperature graphs of the material. 1.1 Objective The objective of this lab report is to measure the impact energy, and calculate the impact toughness, of 1018 Steel V-notch samples at three different temperature that corresponds to differing areas of the ductile-to-brittle transition temperature relationship. The report will also illustrate how mechanical properties of a sample can vary depending on the temperature by ductile- brittle transition temperature of the material. 1.1.1 Equipment and Materials To exert impact on the specimen a Zwick-Roell pendulum impact testing machine will be used. Test subjects will be samples of 1018 annealed steel that are prefabricated Charpy notched specimens in line with ASTM standard E- 23 for “Notched bar impact testing of metallic materials”.

LAB 2: CHARPY IMPACT TEST 2 2. Methodology Three samples of 1018 Steel V-notch samples are collected to be tested at three different temperatures. A sample is placed in a Styrofoam container with dry ice to lower the temperature of the sample to approximately -80°C. Another sample is placed in boiling water to increase the temperature of the sample to 100°C. The remaining sample is kept at room temperature which was round 21°C. To initiate the testing phase, the Zwick-Roell RKP200 Pendulum impact testing machine ’s power breaker and secondary power switch is turned on. The hammer-arm is ensured to be retraced and locked. When the samples are at their respective temperatures, custom forceps are used to place the specimen in the holder with the notch facing away from the hammer. The field is inspected to be clear of obstructions and the access door is closed. The dial is set so that the arm is at zero. The hammer is released, after the hammer breaks the specimen, the pendulum is halted and retracted. Upon completion of the testing phase, the energy value recorded on the dial is recorded with their respective temperatures. The fractured samples are retrieved to access the fracture. The collected data will be used to plot the fracture energy over the temperature for the three materials and discussion will be made on how the structure of the material is dependent on temperature. 3. Results and Discussion 3.1 Results This section of the lab report will present the results of the Charpy impact test of 1018 annealed steel Charpy notched specimens in line with ASTM Standard E-23. The test is performed 4 times to get 4 data sets at the same temperature range. These data sets will be plotted to visualize the change in material ductility with respect to temperature. Table 1: Data from Charpy Impact Test

LAB 2: CHARPY IMPACT TEST 3 Data Set W (J) 100°C 21°C -80°C 1 259 195 7 2 252 205 8 3 255 199 7 4 260 196 9 Average 256.5 198.75 7.75 Below are the plots the fracture energy over the temperature for the three material conditions. Figure 3.1: Graph of Fracture Energy Over Temperature for Data Set 1

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LAB 2: CHARPY IMPACT TEST 4 Figure 3.2: Graph of Fracture Energy Over Temperature for Data Set 2 Figure 3.3: Graph of Fracture Energy Over Temperature for Data Set 3

LAB 2: CHARPY IMPACT TEST 5 Figure 3.4: Graph of Fracture Energy Over Temperature for Data Set 4 An mean value of each data point is found and plotted for a more accurate representation of how the material properties changes according to their respective temperature. Figure 3.5: Graph of Fracture Energy Over Temperature for the Average

LAB 2: CHARPY IMPACT TEST 6 3.2 Charpy Impact test and material structure variation with temperature In conducting the Charpy Impact test, the objective is to quantitatively assess the energy absorbed by materials, such as steel, during fracture, a key indicator of material toughness under various thermal conditions. At markedly low temperatures, specifically – 70°C, steel manifests a heightened brittleness, characterized by a reduced capacity to absorb energy prior to fracturing. This results in a fracture that is abrupt and exhibits minimal plastic deformation. At room temperature, steel presents an equilibrium between ductility and strength, leading to an intermediate level of energy absorption and a fracture pattern that displays both brittle and ductile characteristics. Conversely, at elevated temperatures, such as 100°C, an increase in the ductility of steel is observed. This enhanced ductility facilitates greater plastic deformation, allowing the material to absorb more energy before fracturing, which is indicative of increased toughness. These observations from the Charpy Impact test provide critical insights into the variations in the internal structure of steel across different temperature regimes, thereby underscoring the dynamic nature of material toughness in response to thermal changes. 3.3 Discussion In steel, the interplay between carbon content and its mechanical properties, particularly strength and hardness versus ductility and toughness. As the carbon content in steel increases, its strength and hardness typically rise. Since Carbon atoms are smaller than iron atoms. The carbon atoms distort the lattice structure in iron when they occupy interstitial positions in the iron lattice. This distortion hampers the movement of dislocations, which are defects in the lattice that allow for plastic deformation. This makes high-carbon steel exceptionally strong and hard, suitable for applications requiring resistance to wear and deformation. However, this increase in strength and hardness comes at the cost of reduced ductility and toughness. High-carbon steels, while hard, are also more brittle, making them more susceptible to cracking under stress or impact. This brittleness

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LAB 2: CHARPY IMPACT TEST 7 is a critical limitation in applications where flexibility and impact resistance are essential. The observation that steel exhibits greater brittleness at low temperatures, as evidenced by the more jagged or jarred edges at the fracture point in comparison to smoother edges when the same material was tested at room temperature and high temperatures. Therefore, it can be reasonably inferred that to mitigate the occurrence of brittle fracture, maintaining the steel at room temperature or elevating it to higher temperatures is beneficial, as this promotes a more ductile fracture response. The fracture resistance of the tested samples was dependent on the energy absorption of the metal. Since higher temperatures increase the energy absorption of the metal, the fracture resistance also increases with heat. The surfaces of the fracture also changed with the temperature. The ductile to brittle transition temperature for steel is 0°C. Between our tests at 21°C and -80°C, the fracture energy greatly decreases, indicating that the transition temperature lines in between these two temperatures. The ductile to brittle temperature that was found lies in between 21°C and -80°C, which is expected. The ideal temperature for the metal to avoid sudden brittle fracture upon impact is any temperature above the ductile to brittle transition temperature which is around 0°C. The 100°C sample plastically deformed when hammer contacted the steel and did not completely break. The sample at -80°C was extremely brittle and fractured rapidly. The sample at 20°C was close to the fracture point and underwent plastic deformation. These results align with our understanding of fracture energy and temperature. Steel becomes more ductile at higher temperatures and as a result it plastically deforms instead of undergoing a fracture when the hammer hits it. Steel becomes more brittle when at lower temperatures, as a result it is more susceptible to brittle fractures. When the hammer hit the sample at -80°C it fractured quickly.

LAB 2: CHARPY IMPACT TEST 8 Under room temperature, steel is a very tough and durable material, as a result it won’t plastically deform or fracture easily. The possible sources of error include temperatures of the metals are not precisely monitored and can affect the results. The lack of sample data has impeded us while making the graph and forced us to make gross assumptions for the ductile to brittle transition temperature. The sample size needs to increase and include a wider range of steel samples at different temperatures.

LAB 2: CHARPY IMPACT TEST 9 3.4 Sample Calculations

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LAB 2: CHARPY IMPACT TEST 10 4. Conclusion In conclusion, by completing the Charpy Impact test, it was determined that a sample of steel will deform in a brittle or ductile manner depending on the temperature of the metal at the time of impact. At -80°C, the sample only absorbed an average of 7.75 J of energy which resulted in a quick brittle break. At 21°C & 100°C, the average fracture energy was 198.75 J & 256.5 J respectively. The high fracture energy observed in these temperatures which are past the transition temperature result in plastic deformation. To avoid brittle fractures, 1018 Steel should be kept above 0°C, which was observed to be roughly the average transition temperature.

11 References • N. Bano, B.A. Shirvani, X. Xie, Data - Lab 2 – Charpy Impact Test, University of Ottawa, Department of Mechanical Engineering, 2023 • Zwick-Roell, Product Information HIT450P/HIT300P Pendulum Impact Tester for Metal Specimens, 2023, https://www.zwickroell.com/products/products-for-impact- testing/pendulum-impact-testers-for-tests-on-metals/