And its percent reduction of the area was 547 by

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and its percent reduction of the area was 54.7%. By processing the data collected, a stress-strain diagram for 6061-T6 Aluminum was drawn, which is shown in Figure 14. It was found that 6061-T6 Aluminum has Young’s modulus of 64.2 Gpa (see Figure 16), yield strength of 315 Mpa (see Figure 15), and the ultimate strength of 338 MPa. 3.5 304 Stainless Steel 7
The specimen of 304 stainless steel showed apparent necking and fractured with a cup and cone surface in the tensile test, which is shown in Figure 17. It reached a yield load of 9.6 kN and a maximum load of 24.2 kN. Through the tensile test, its percent elongation was 76.7% and its percent reduction of the area was 75.2%. By processing the data collected, a stress-strain diagram for 304 stainless steel was drawn, which is shown in Figure 18. It was found that 304 stainless steel has Young’s modulus of 178.6 Gpa (see Figure 20), yield strength of 243 Mpa (see Figure 19), and the ultimate strength of 611 MPa. 3.6 Polymethylmethacrylate (PMMA) The specimen of PMMA fractured with a flat surface in the tensile test, which is shown in Figure 21. It reached a maximum load of 3.1 kN. Through the tensile test, its percent elongation was 3.7% and its percent reduction of the area was 0.75%. By processing the data collected, a stress-strain diagram for PMMA was drawn, which is shown in Figure 22. It was found that PMMA has Young’s modulus of 2.9 GPa and ultimate strength of 63 MPa.
4. DISCUSSION 4.1 Stress-strain Curve The stress-strain diagrams are shown in Appendices. Different materials have their own unique diagram, which shows their mechanical properties. And similar stress- strain diagrams show similar properties among the materials.
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For 1045 steel normalized, its linear region is similar to that of 1045 steel as received. However, after reaching the proportional limit, the stress decreases to reach the yield point, which is different from 1045 steel as received. After the yield point, the strain still increases continuously, while the stress first increases to the ultimate strength and then decreases until fractured. For 6061 Aluminum, its diagram is similar to 1045 steel as received’s. The stress increases linearly first to the yield point. After that, the stress goes up a little bit to the ultimate strength, and then continually decreases until the fracture point reached. For 304 S.S., the stress increases linearly to the yield point first. From the yield strength to the ultimate strength, the curve has a relatively small slope when the stress increases. After the ultimate strength, the stress decreases drastically with a relatively large slope to reach the fracture point.

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