Activity Tensile Testing SIM

Transcription

1 Activity Tensile Testing SIM Introduction Tensile testing provides engineers with the ability to verify and establish material properties related to a specific material. This verification process is critical in ensuring that the selected material will meet design specifications. In this activity you will interpret and make sample specific calculations related to the material properties of a dog bone test sample. Equipment Computer with access to Virtual Tensometer and Adobe Flash Material Testing Formula Sheet Procedure You will use a tensile test simulation to observe how the test is performed and how the force displacement graph is created during the test. You will perform calculations using the graph to better understand the graph and important data. 1. Go to the Virtual Tensometer. 2. Click Enter to begin the simulation. POE Unit 2 Activity Tensile Testing SIM Page 1

2 3. Choose Want to try? 4. Click on the image of the Virtual Tensometer. 5. This should bring you to the Virtual Tensometer for testing. 6. Four materials are available to test. All but cast iron will create usable data for this activity. Check with your instructor to determine which material you will test. A sampling of each material should be tested among the class. 7. Test the material by dragging it into the clamps and pressing Start. 8. Upon completion of the test, enlarge your browser window by using Ctrl + so that the graph is large. POE Unit 2 Activity Tensile Testing SIM Page 2

3 9. Take a screen shot of the browser, paste it into the Proportional Limit table below, and then crop out all but the graph. Copy the cropped image and paste it into the remainder of the tables. The original diameter of the specimen is 5mm or 0.20 in. and the original length is 75mm or 2.95 in. Test Sample Calculations Proportional Limit Stress The greatest stress that a material is capable of withstanding without deviation from straight line proportionality between the stress and strain. If the force applied to a material is released, the material will return to its original size and shape. Locate the proportional limit on the test graph. Solve for the proportional limit stress: = P/A POE Unit 2 Activity Tensile Testing SIM Page 3

4 Yield Point Stress The point at which a sudden elongation takes place while the load on the sample remains the same or actually drops. If the force applied to the material is released, the material will not return to its original shape. Locate the Yield Point on the test graph. Solve for the Yield Point stress: = P/A POE Unit 2 Activity Tensile Testing SIM Page 4

5 Ultimate/Tensile Stress The point at which a maximum load for a sample is achieved. Beyond this point elongation of the sample continues, but the force exerted decreases. Locate the maximum load location on the test graph. Solve for the Ultimate/Tensile stress: = P/A POE Unit 2 Activity Tensile Testing SIM Page 5

6 Breaking/Rupture Point The maximum amount of stress that can be applied before rupture occurs. The specimen fractures in the necking region where the material reduces in diameter as it elongates. Locate the Breaking/Rupture Point on the test graph. Solve for the Breaking/Rupture Point stress: = P/A POE Unit 2 Activity Tensile Testing SIM Page 6

7 Modulus of Elasticity A measure of a material s ability to regain its original dimensions after the removal of a load or force. The modulus is the slope of the straight line portion of the stressstrain diagram up to the proportional limit. Solve for the Modulus of Elasticity: E = (P 1 -P 2 )L 0 /( 1-2 )A POE Unit 2 Activity Tensile Testing SIM Page 7

8 Modulus of Resilience A measure of a material s ability to absorb energy up to the elastic limit. This modulus is represented by the area under the stress vs. strain curve from 0-force to the elastic limit. Solve for the Modulus of Resilience: U r = ½( yp yp) POE Unit 2 Activity Tensile Testing SIM Page 8

9 Modulus of Toughness A measure of a material s ability to plastically deform without fracturing. Work is performed by the material absorbing energy from the blow or deformation. This measurement is equal to the area under the stress vs. strain curve from its origin through the rupture point. Solve for the Modulus of Toughness: U t = 1/3 ( br )( yp + 2 ult ) Conclusion Questions 1. Test and observe the graph created when testing cast iron. What does the graph tell you about the hardness of cast iron? Describe an application where the hardness of cast iron would be an advantage. 2. Compare the difference in the size and shape of the material if the test is stopped before or after the yield point. POE Unit 2 Activity Tensile Testing SIM Page 9