Solid Mechanic Lab ( Lab 5). Egme 306A, Essays (university) of Mechanical Engineering

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Experiment 5 – Charpy Impact EGME 306A - Stress Mechanics Laboratory Szymon Lao 11/29/2021 Submitted to: Patrick Phelan 1 Contents I Abstract .......................................................................................................................................... 2 II Results ............................................................................................................................................ 3 III Discussion & Conclusion ................................................................................................................ 6 IV Appendix ........................................................................................................................................ 7 IV.1 Fracture Pictures ............................................................................................................... 7 IV.2 MATLAB Code.................................................................................................................. 11 EGME 306A Experiment 5 – Charpy Impact 4 Figure A-2: Impact Energy vs. Temperature Right Station From figures A-1 and A-2 we can see the relationship that impact energy has with temperature. We can see that 1018 steel has the more drastic change between the other two. It is also the only material to have the lowest impact energy at lower temperatures. This is no surprise since steel is a very brittle material. We also know that steel has the highest temperature that transitions from ductile to brittle which explains the sudden shift in low impact energies at lower temperatures. Aluminum shows a very tame graph as it does not move as significant compared to 1018 steel. This is because aluminum is more ductile compared to 1018. Table 1: Ductile to Brittle Transition Temperature 1018 Steel 4140 Steel Aluminum 6060 Left Station 42.06 oF 28.89 oF N/A Right Station 53.10 °F 21.59 °F N/A EGME 306A Experiment 5 – Charpy Impact 5 Table 1 shows the ductile to brittle transition temperatures for all three materials and for both stations. As mentioned on the graphs, we see that 1018 steel has the highest temperature compared to 4140 Steel. This indicates that 1018 steel will turn brittle at a much higher temperature than 4140 Steel. We can conclude that 1018 steel is more brittle than 4140 Steel. This is expected since 4140 is known for its toughness and impact resistance. Pictures B1 to B3 show 1018 steel through three different temperatures. These pictures show a close-up on the fracture failure. From our experiments we found that 1018 steel has a ductile to brittle temperature of approximately 40°F. Picture B2 shows a brittle failure which is expected since dry ice temperatures were around -100°F. Ambient temperatures at the time of the experiment was 70°F which is above the DBTT but closer compared to heated temperatures. This explains why picture B3 shows a mix of brittle and ductile failure, the sample is still connected but still shows a sudden fracture. As expected for picture B1 shows a ductile failure. Oven temperature was 115°F, it is a temperature much higher than the DBTT which allowed it to be more ductile. We can notice the fracture failure of B1 is much more connected compared to the rest. Picture B1: Oven Temperature 1018 Steel Ductile Failure Picture B2: Dry Ice Temperature 1018 Steel Brittle Failure Picture B3: Ambient Temperature 1018 Steel Mix of Ductile and Brittle Failure EGME 306A Experiment 5 – Charpy Impact 6 III Discussion & Conclusion We experimented on three different metals at six different temperatures. Our goal is to find the ductile to brittle transition temperatures for these three metals. Our test samples were made of 1018 Steel, 4140 Steel, and Aluminum 6060. It is important to find these transition temperatures as some designs may go through different temperatures and depending on what the design is intended for; it would be beneficial to know when the material will turn from ductile to brittle. Through experimentation, we found the ductile to brittle transition temperature for 1018 steel is 42.06°F for the left station and 53.10°F for the right station. 4140 Steel has a DBTT of 28.89°F for the left and 21.59°F for the right. These numbers are expected since 4140 steel is known to be tough. Having a lower transition temperature means it will be ductile at a larger temperature range. You can see that Our values from the two stations differed a bit but did not stray away from each other significantly. This can be attributed to experimental error. During the experiment, we initially had an assigned person for grabbing the test sample from the temperature-controlled area to the pendulum. However, halfway through the experiment, our lab technician told us to switch people around. This creates an issue with consistency since another person can be quicker or place the test sample off-center. To alleviate these errors, it would be best to just keep an assigned person for each task. 9 10 11 IV.2 MATLAB Code %%Author: Szymon Lao %Date: 11/27/21 %Experiment 5 clear, close, clc; filename = "charpy_impact_data.xlsx"; for n = 1:2 %Reading our data sheets data = readmatrix(filename, 'Sheet', n, 'Range', 'B2:G7'); %1018 e_max1018 = max(data(:,1)); e_min1018 = min(data(:,1)); etrans_1018 = (e_max1018 + e_min1018)/2; etrans_1018 = ones(1,6)*etrans_1018; t_1018 = data(:,1); e_1018 = data(:,2); [db1018,tr_1018] = polyxpoly(t_1018,e_1018, t_1018, etrans_1018); db1018 = ones(1,6).*db1018; db{n,1} = db1018; %collecting dbtt for 1018 %4140 e_max4140 = max(data(:,4)); e_min4140 = min(data(:,4)); etrans_4140 = (e_max4140 + e_min4140)/2; etrans_4140 = ones(1,6)*etrans_4140; t_4140 = data(:,3); e_4140 = data(:,4); [db4140,tr_4140] = polyxpoly(t_4140,e_4140, t_4140, etrans_4140); db{n,2} = db4140; %collecting dbtt for 4140 %6060 e_max6060 = max(data(:,6)); e_min6060 = min(data(:,6)); etrans_6060 = (e_max6060 + e_min6060)/2; etrans_6060 = ones(1,6)*etrans_6060; t_6060 = data(:,5); e_6060 = data(:,6); [db6060,tr_6060] = polyxpoly(t_6060,e_6060, t_6060, etrans_6060); db{n,3} = db6060; %collecting dbtt for 6060 f = figure(n); f.Position = [0 0 750 500]; f.Visible = 'on'; %%Plotting plot(t_1018, e_1018, 'b-o', 'linewidth', 2) hold on plot(t_4140, e_4140, 'r-o', 'linewidth', 2) hold on plot(t_6060, e_6060, 'g-o', 'linewidth', 2) hold off xlabel('Temperature [^{o}F]'); ylabel('Impact Energy [lb-ft]'); legend('1018 Steel' , '4140 Steel','Aluminum 6060', 'Location' , 'Northwest'); if n == 1 s = 'Left Station'; else s = 'Right Station'; end title(sprintf('%s',s)) ax = gca; %exportgraphics(ax,['figures/ener_temp_' num2str(n) '.png'], 'Resolution', 300) end