Expermint 3-Torsion Test

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Washington State University *

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Mechanical Engineering

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Apr 3, 2024

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Met 225 Torsion Test September 11 th ,2023 Aaliyah Ashley aashl009@odu.edu

Torsion Test Purpose: The purpose of this lab was to see how the material would respond to being repeatedly twisted. Also, using the torsion test can determine the Proportional limits, yield strengths in shear, shearing resilience, and stiffness. Seeing how the much steel rod will twist until it fractures. Theoretical Considerations: The theoretical considerations of the experiment were the relationship between shear modulus of rigidity and tensile modulus of elasticity. Which is when we are seeing if that is true and if can be proven to be true. Description Apparatus: 1. 10k Torsional Machine: The 10k Torsional Machine has a cover on for safety purposes. There is a 602 controller that has several keys. Two of the keys are for speed, one is to increase the speed and the other is to decrease the speed. There are two heads, one is attached to the box of the machine, while the other is on a slider where it can be pushed further away from the other head or closer to it. On top of those heads are knobs that tighten the piece into place. There are rings that are on the face of the head that need to be in the same circle. And inside where the bar is going, there are connectors that have teeth and gears to keep the steel rod in place. Procedure: 1. A micrometer caliper was used to determine the mean of the steel specimen near the mid-length. 2. The shearing proportional limit of 0.6 of the tensile proportional limits and the shearing modulus of rupture as equal to the tensile strength was assumed. 3. Serval readings were taken before and after the proportional limits. The speed Sp was set to 10 degrees/minute (Sp1). The proportional limit was reached, the speed Sp was increased 60 degrees/minute (Sp2). 4. The gage length of 8 inches for the ductility computation was assumed. 5. The specimen was inserted into the two heads, and the chuck end grips were tightened. 6. The 10k torsional machine was set to zero prior to the test.

7. Readings were taken from the 602 controller LCD screen. At the top of the screen, the applied torque was shown in lbs-in and below the rotation in degrees. 8. They torque was applied at Sp 1. The proportional limit was reached the machine was stopped and the rotational speed was increased to Sp 2. The load was applied until it fractured. 9. The steel specimen fractured and was removed, and observations were made. Data Tables: Mean Of Diameter (in) 0.753 Whole Length of Bar (in) 14.75 Gage Length (in) 9.937 Readings Torque (lb-in) Angle Deflection (radians) Shear Stress(τ) (MPa) Shear Strain(Y) (radians) 1 180.50 0.0285 14.85 0.0036 2 279.17 0.0538 22.96 0.0067 3 535.45 0.0988 44.04 0.0123 4 678.81 0.1274 55.83 0.0159 5 820.53 0.1553 67.48 0.0194 6 1027.2 0.1789 84.48 0.0223 7 1269.2 0.2039 104.38 0.0255 8 1820.3 0.2529 149.71 0.0316 9 2036.9 0.2634 167.52 0.0329 10 2695.3 0.3196 221.67 0.0399 11 2848.5 0.3890 234.27 0.0486 12 3205.8 1.4364 263.66 0.1795 13 3652.4 2.3108 300.39 0.2889 14 3927.5 2.9866 323.01 0.3733 15 4095.6 3.4704 336.84 0.4338 16 4351.1 4.3413 357.85 0.5426 17 4546.6 5.1576 373.93 0.6447 18 4874.5 6.8382 400.90 0.8547 19 4965.4 7.4468 408.37 0.9308 20 5035.2 7.9473 414.11 0.9934 21 5290.6 10.1806 435.12 1.2725 22 5392.0 11.2399 443.46 1.4049 23 5567.0 13.4985 457.85 1.6873 24 5723.0 15.9795 470.68 1.9974 25 5811.8 17.6296 477.98 2.2037

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Calculations: Shear Stress Calculations: Shear Strain Calculations:

Graph: Proportional Limit 170 MPa Modulus of rigidity Ductility Ultimate Shear Strength 430 MPa Tensile Proportional Limit The mode of failure is the ductility failure. Because of the low value of Shear strain.

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Compare the Properties of the Steel Bar: The properties of the steel bar sit between a hot rolled steel bar at 0.2% carbon and cold rolled steel bar at 0.2% carbon. It is closer to a hot rolled steel bar than cold rolled. But the number do show that they are in between both. Discussion of Results In this experiment there was many parts to it that are going to be talked about. Like the graph, the results of the lab, how could have been done different or what could have been gone better with the experiment. The graph was the best fit of Shear Stress (ordinate) vs Shear Strain (abscissa) based on the data that was recorded during the experiment. The trend of the graph is increasing, which is being shown by every time stress increases for every time that strain increases. While the graph was increasing, on the other hand, it was not linear. The curve looks very close to being linear, but it does have humps that are peaking slightly before coming back down. The graph did not start at the origin (0,0). It had started a little bit higher than that. The first point it started at was (0.0036, 14.85). From this point on, it slowly increased and did not have any large increases that occurred. This continued until the end of the graph, but it has slight peaks in the middle of the graph. Towards the end, it looks like it is starting to straighten out and become more linear. When it straightens, the stress was at 478 and strain was at 2.20. here were no data points that were outliers. The graph shows how it is increasing over time between each point.

There were not many problems that happened during the experiment. The problem that occurred was get the head of the machine to the correct angle. And when doing so the once it got the angle of 0 it continued moving. Maybe getting it to the angle it needed to be at before putting on side of the rod it. Also, when the Steel rod broke it broke at the top and not in the middle of it. A way to improve could have maybe seeing if the bar would go further into the head that able to be moved. Overall, the graph shows how it stress is increasing with strain. And shows the significant parts of the curve and shows important increases that are significant to the curve. The stress vs strain looks more linear than a curve because the data points are not spread apart enough to make the curve for the graph. But it makes peaks where it was slightly increasing more than other places. There were not many things that needed to be improved while doing the experiment.