TorsionLabManual

TorsionLabManual - EGR75L: Torsion Test Joseph Nadeau Civil...

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Unformatted text preview: EGR75L: Torsion Test Joseph Nadeau Civil & Environmental Engineering Duke University October 18, 2006 During the course of this laboratory a material specimen (see Fig. 1) is going to be gradually loaded in torsionuntil it failswhile collecting torque and relative rotation between two points on the specimen. 1 Objective The objective of this laboratory is to provide an introduction to the torsion test and to evaluate a number of material properties from the data collected during the torsion test. In the tension test, a material specimens Youngs modulus, E , was evaluated. In this test a second elastic material will be determined, namely, the shear modulus, G . Given these two elastic material constants, E and G , it is possible to calculate any of the three other elastic material constants. Two of those three you should be familiar with: Poissons ratio, , and bulk modulus, . Additional material properties, namely, (shear) yield stress y and ultimate (shear) stress u . Figure 1: A Torsion test specimen 2 Equipment The various instruments needed to conduct the torsion test are listed below: 1. Tinius Olsen Lo-Torq Machine (see Fig. 2): Applies a torsional load to a specimen by gripping it between two crossheadsone fixed and one rotating. The maximum capacity of the load 1 cell is 10,000 kg-cm and that of the electronic rotation sensor is 200 degrees. Scale on rotating cross-head permits manual reading of cross-head rotation. Figure 2: Tinius Olsen Lo-Torq Machine 2. Olsen-Muhlenbruch Troptometer (see Fig. 3): Measures the relative rotation between two points on specimen. The troptometer has a variable gauge length of 10-30 cm and can measure relative angles of rotation up to 60 degrees. 3. Safety Glasses/Goggles: Protects eyes from potential metal fragments when the specimen fails. 4. Ruler: Measure gauge lengths. 5. Calipers: Measure specimens diameter. 6. Specimen (see Fig. 1) 3 Procedure The testing procedure involves two distinct phases: set up and execution. The steps involved in each of these phases will be described in detail below in Sections 3.1 and 3.2, respectively. 3.1 Experimental Set Up 1. Record (in Table 1) the make, capacity, and range of the loading machine and troptometer. 2 Figure 3: Olsen-Muhlenbruch Troptometer 2. Record (in Table 1) the material type of your specimen. 3. Measure and record (in Table 1) the diameter of the specimen. 4. Using a marker, draw a bold, straight, line down the length of the specimen. This line will allow you to observe how those colored material points move relative to each other throughout the experiment. 5. Using a marker, make two small dots, separated by a predetermined gauge length (try 16 cm), in the middle portion of the specimen. If these two points were connected by a straight line that line should be parallel to the axis of the specimen. Record this gauge distance, L 1 , in Table 1....
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TorsionLabManual - EGR75L: Torsion Test Joseph Nadeau Civil...

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