When examined under a microscope the morphology has a

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that of a hollow cylinder (Figure 2c). When examined under a microscope, the morphology has a distinct pock-mark appearance and is referred to as a micro void coalescence morphology. 3. Methods: a. For smooth specimen: One plate specimen without a crack will be subjected to uniaxial tensile stretch and the resulting force will be measured. The goal is to obtain the stress-strain curve and the various material parameters that characterize the elastic and plastic properties of materials. Procedure is given as: 1. Measure specimen dimensions using callipers: length between two marks, width (at several places along the length), and thickness (at several places along the length). 2. Grip the specimens firmly following the instruction of the instructor. 3. Attach an extensometer on the specimen. 4. Set up the extension rate, limiting load, and limiting extension for the test according to the instruction of the TA. 5. Follow the loading instructions impose a slow stretch rate. You should go from 0 to about 4000 lbf in about 250 seconds. Do not break the smooth specimen! 8. Terminate the test. 9. REMOVE the extensometer and specimen according to the instruction of the TA. 10. SAVE the experimental data for analysis. b. For notched specimen: One specimen with a notch as shown is used. 1. Measure specimen dimensions using callipers: length between two marks, width (at several places along the length), thickness (at several places along the length), and the length of the notch.
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2. Grip the specimens firmly following the instruction of the instructor. 3. Do not use an extensometer. 4. Set up the extension rate, limiting load, and limiting extension for the test according to the instruction of the TA. 5. Follow the loading instructions impose a slow stretch rate until the specimen breaks. You should go from 0 to about 4000 lbf in about 250 seconds. 6. Terminate the test. 7. REMOVE the extensometer and specimen according to the instruction of the TA. 8. SAVE the experimental data for analysis. 9. Collect the two pieces and make sure the broken ends do not rub together, since you will need them for microscopy. 10. Examine the fracture surface on the two pieces. Identify the area of ductile fracture (shearing). c. For cracked specimen: 1. Measure specimen dimensions using callipers: length between two marks, width (at several places along the length), thickness (at several places along the length), and the length of the crack. 2. Produce a crack on both specimens using a fatigue test. One should have a shorter crack length (about 0.05’’) and another should have a longer crack (about 0.2”). Record the exact crack lengths. 3. Grip the specimens firmly following the instruction of the instructor. 4. Do not use an extensometer. 5. Set up the extension rate, limiting load, and limiting extension for the test according to the instruction of the TA.
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