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Creep in Metals Laboratory Report

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BE 1310 Creep in Metals Laboratory Report Creep in metals is evaluated by the change in length versus time. For the creep to take place its important to consider the magnitude of the stress as well as the temperature. When evaluating the creep curve, the initial strain has significant effects on the length, which is followed by decrease in the strain rate as the primary creep takes place. The derivative of the primary creep is noted as the steady-state creep rate. After the steady-state creep rate a rapid change in the data will be observed as the strain causes fracture. This time dependent deformation must be considered during engineering design for safety and longevity. Materials and Methods A Sm 106 Mk II creep testing machine was used along with a stop watch and lead specimens in the lab experiment. The creep machine consists of a lever, steel pins that hold the specimen, bearing block, weight hanger, and a dial test indicator. ...read more.


Sample 1 Sample 2 Sample 3 Area 5.1360 mm2 5.1948 mm2 5.1467 mm2 Table 2: Measurement of the area of our lead specimens. Weights 0.6 kg 0.7 kg 0.8 kg Force 76.1256 N 83.9736 N 91.8216 N Stress Sample 1 14.8220 N/mm2 16.3500 N/mm2 17.8780 N/mm2 Sample 2 14.6542 N/mm2 16.1649 N/mm2 17.6757 N/mm2 Sample 3 14.7911 N/mm2 16.3160 N/mm2 17.8409 N/mm2 Table 3: Measurement of the force and stress of the lead specimens for each load. Time (t) Reading (a) ?Reading (a-a1) Stretch (?l) Strain (?) 0 12.75 0 0 0 15 15.85 3.1000 1.5500 0.4062 30 16.25 3.5000 1.7500 0.4586 45 16.50 3.7500 1.8750 0.4914 60 16.69 3.9400 1.9700 0.5162 15 16.84 4.0900 2.0450 0.5359 30 16.93 4.1800 2.0900 0.5477 45 17.07 4.3200 2.1600 0.5660 60 17.15 4.4000 2.2000 0.5765 15 17.23 4.4800 2.2400 0.5870 30 17.31 4.5600 2.2800 0.5975 45 17.38 4.6300 2.3150 0.6067 60 17.47 4.7200 2.3600 0.6184 15 17.57 4.8200 2.4100 0.6316 30 17.67 4.9200 2.4600 0.6447 45 17.77 5.0200 2.5100 0.6578 60 17.86 5.1100 2.5550 0.6695 15 17.96 5.2100 2.6050 ...read more.


Results and Discussion Load or stress usually occurs to materials at high temperatures. The operating temperature greatly affects the creep, a time dependent deformation, of engineering materials. On the other hand, materials such as lead and polymers can undergo creep at room temperature. The creep curves in each of the three graphs represent the time vs. strain behavior of lead under a constant load at constant temperature. It involves a primary creep, secondary (steady state), tertiary creep and a fracture point. The three lead samples have marginally small differences, approximately 0.3%, which is necessary for consistent results. The SM106K2 creep testing machine allows users to mount the sample and measure the elongation caused by the mass from reading the dial test indicator every 15 seconds. Figure 1 Figure 2 Figure 3 Figure 4 Formula 1 Formula 2 Formula 3 Formula 4 Conclusion Using the three values calculated from the slope of primary creep stage vs. sigma it is possible to solve 'n' for lead. These three data points can be seen in Figure 4. The value of 'n' for lead has been determined to be 11.5775. ...read more.

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