Lab7.docx - Mideast Engineering and Testing, INC. Material...

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Mideast Engineering and Testing, INC.“Material properties is the key to success!”501 Mercury DriveChampaign, Il 61822February 22, 2018Dr. John PopovicsPopovics Manufacturing Co.4200 Industrial Blvd.Morristown, NJ 07960Dear Dr. Popovics,On behalf of Mideast Engineering and Testing, is our pleasure to send you these experimental results. Two differentspecimens, which made of lead and high-density polyethylene, were subjected to a creep test. Also, two high-densitypolyethylene were subjected to tensile test in different displacement rate usingInstron Model 4400 load frame to studyits strain-rate sensitivity. All the dimensions were measured by a digital caliper, and all the data was recorded by acomputer data acquisition system.For the specimens performed in the creep test, the engineering stress and the creep rate for lead and HDPE were bothincreased as the incremental loads were added. From Table 2 in the enclosures, lead had engineering stress of 3.95MPa,4.83MPa, 6.16MPa and 7.48MPA; creep rate of 2.03E-06s1, 2.32E-06s1, 6.92E-06s1and 1.25E-05s1as the load increased. HDPE had engineering stress of 1.64MPa, 3.61MPa, 7.54MPa and 13.4MPA; creep rateof 7.27E-07s1, 1.24E-06s1, 4.59E-06s1and 1.64E-05s1as the load increased. From Figure 3 and4, the log creep rate versus log stress curve for HDPE presented a same linear relationship, the constant B and m are2.64E-07 and 1.49 respectively. For lead specimen, it existed different linear relationship within the time span ofdifferent load. The constant B are 8.15E-07, 1.96E-09 and 2.73E-08, and the constant m are 0.664, 4.49 and 3.25.From Figure 1 and 2 in enclosures, the creep rate increased for both specimen as the applied load increased. And theirengineering strain-time curve exhibited instantaneous strain, primary creep and secondary creep when an incrementalload was added. The creep exponent m of lead changed within 0.664 to 4.49 as incremental load added, experiencedboth grain boundary diffusion and dislocation climb. However, the creep exponent m of HDPE stated the samethroughout the test as shown in Table 2, it only exhibited grain boundary diffusion. Both lead and HDPE exhibitedbehavior as other materials. It is because they performed instantaneous strain, primary creep and secondary creep. Also,after a large load was added to lead specimen at 4000 second, a large, clear instantaneous strain was shown. And afterall the load was removed to HDPE specimen at 4000 second, an instantaneous elastic recovery and a delayed elasticityhappened. Therefore, both specimens were consistent with other materials. The measured creep rates were in the steady-state creep region since they were determined within 500 second to 900 second which is after the primary creep state.

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Term
Fall
Professor
Popovics
Tags
Materials Science, LAb 7, Tensile strength, Mideast Engineering and Testing

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