Brass Torsion Testing

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University Of Arizona *

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324L

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Mechanical Engineering

Date

Jan 9, 2024

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AME 324L Cooper Dickerson 08/27/2023 Section #1 Brass Torsion Testing

AME 324L Cooper Dickerson 08/27/2023 Section #1 Introduction: For this experiment, we wanted to test the properties of a brass rod under the effects of torsion strain. The importance of this experiment comes from the fact that twisted shafts are important in different objects or experiments around the world. Due to this it is important for us to know what stresses might be involved with different materials and how they react to torsion forces. We need to know how much torque this materials can go through and remain fine, versus the amount that compromises their integrity. For this particular experiment, we performed a torsion test on a brass rod, in order to determine the shear stresses, and strains and to calculate experimental values from these tests. Method: For this experiment, we used a torsion testing machine, a computer with Labview in order to connect to the machine and its sensors, and a Brass rod. We started by first using calipers to take exact measurements of the brass rod, that we were working with. Once we finished recording measurements of the brass rod, we drew a straight line down the rod, and began to insert it into our torsion machine. We did this by first retracting the sliding base, and then clamping the brass rod in the fixed position clamp. We then moved the sliding base back, and clapped the other side. Once both sides were properly clamped down, we proceeded to set up the LabView on our computer to record the data from the torsion testing machines sensors, as well as the sensor that would record its rotation. Once we had everything calibrated, we were able to run our tests. Our results were then converted into an excel file or an excel spreadsheet due to the LabView that we had set up. This Excel Spreadsheet then allowed us to view our data in order to determine our results for our shear stress and shear strain.

AME 324L Cooper Dickerson 08/27/2023 Section #1 Results: Through the testing of the brass rod through the Torsion testing machine, we were able to conclude that the brass rod is a very ductile material. This conclusion was reached through many different ways. We can see this when looking at our results and the strains and stresses. We are also able to see this, when we look at how the piece breaks. Since it is a clean break, and not at a 45 degree angle, we can see that it is a ductile material and not brittle. A brittle piece of material would have resulted in a 45 degree angle when it finally snapped. We were also able to see how many times the torsion testing machine turned it in a circle through the sharpie straight line we initially drew on the Brass Rod. We were also able to see that in our two different tests that the two different rods broke in two different location. The first one snapped where the rod tapered down to the cylindrical portion, where as the other rod snapped in the middle. My data in the chart I was able to calculate also does not resemble the data I know it should look like.

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AME 324L Cooper Dickerson 08/27/2023 Section #1 Error Analysis: Through this testing process, my group encountered many opportunities for error. First we did the test initially with a brass rod, but Had not recorded its rotation accurately, forcing us to do the experiment again. We then recalibrated the machine and its sensors, and then did the experiment again. The large portion of error comes from the fact that there was a technology error on the computer once we had finished our test. This caused us to not be able to retrieve our data on an excel file. Due to this our TA instructed that he would send us data, but that data would also not fit the exact measurements of our rod. We then were never sent the data, from our instructors. Members of my group received data from others who had completed the experiment, but they did not answer me in time to share the full data with me in order to finish my calculations. Another source of error could have come from improper measurements of the brass rod, or the rotation sensor again not being calibrated all of the way. Conclusion: The physical portion of the lab and experiment were successful, and properly demonstrated the effects of a ductile material under torsion. This allowed us to observe the effects that a ductile material should have. However, I would consider the calculations portion of this experiment to be a failure, because I did not have the proper data to go along with the physical experiment, or the data that I measured initially. Questions: Q) Consider briefly two round shafts of equal area One Hollow And The other solid: 1.1 Does One Have More Stiffness Than The other?

AME 324L Cooper Dickerson 08/27/2023 Section #1 A) The stiffness of the hollow shaft is more than the stiffness of the solid shaft if they have the same weight. This is because the weight is distributed farther out on the outer radius. Q)Under The Same Amount Of Torsion Loading, Does One Have More Stress Present Than The Other At The Outer diameter? which Tube will have higher angle of rotation? (5) A) The angle of rotation is higher is hollow tubes, The hollow tube also has more stress present on the outer diameter, because it does not have the internal portion to take any of the stress. Appendix: