Lab 4.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 Drive Champaign, Il 61822 March 8, 2018 Dr. John Popovics Popovics Manufacturing Co. 4200 Industrial Blvd. Morristown, NJ 07960 Dear Dr. Popovics, On behalf of Mideast Engineering and Testing, it is our pleasure to send you these experimental results. 1045 hot-rolled steel (steel), 6061-T6 aluminum (alum), and polymethylmethacrylate (PMMA) were tested for this notched bending test. A four-point bending test was performed, and for each metal material, two specimens one with sharp and other with round notches were tested. For PMMA, two specimens with identical sharp notches were tested in both tension and compression by alternating the orientation of the specimens. The gathered data was then analyzed and compared with data for same material acquired from tension, compression and bending tests. Moreover, fringes for specimens with different notches and cracks were visualized by using a polariscope. Fracture took place in all the tested specimens. For steel and alum, the test was stopped manually when the applied load dropped below 0.3kN, and we then break the material along the fracture surface by hands. Modulus of Rupture for steel with sharp and round notches are -974MPa and -1345MPa respectively. Apparent yield strength for steel with the same notches order shown above are -673Mpa and -650MPa. Modulus of rupture for alum with sharp and round notches are -516MPa and -615MPa respectively. Apparent yield strength for alum with the same notches order shown above are -456MPa and -440MPa. For PMMA, specimens broke into two halves during the test. Modulus of rupture for PMMA with tension and compression are -148MPa and -12.2MPa respectively. All the data collected during the experiment could be found in Table 1&2. Comparing the apparent yield strength with the results we acquired in the previous labs, we could observe that for alum, yield strength increased by 67% and for steel, yield strength increased by 25%. Hence, the yield strength for ductile material could be increased when a notch presented in the material. The increase of the yield strength is due to a triaxial tensile strength developed near the notch root and hence causes higher yield strength for unnotched specimens. We also observed that the predicted yield strength is higher for steel when compared with apparent yield strength while lower for aluminum when compared apparent and predict yield strength. The main reason for the discrepancy is that alpha was chosen to be 0.3 for different material with different notches and thus less reason to account for all these different situations. With the data and fracture type observed in this test, we can predict the performance of cast iron in this notched beam test. Since cast iron is a brittle material as we have observed in the tension test, it is reasonable to predict that cast iron would have similar performance when compared with PMMA for which is also a brittle material in tension. Cast iron will have an increased modulus of rupture if the notched side is in compression and a drastic decrease in rupture of modulus when the notched side is in tension. For the photoelasticity test, the fringes

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