EML6324 HW 1 - l f The true strain ε f at fracture is...

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Fall 2011 EML6324 Fundamentals of Production Engineering HW 1 (Due on Sept. 9, 2011) 1 Q1. What is the difference between engineering stress and true stress in a tensile test? Q2. Which of the two tests, tension or compression, requires a higher capacity testing machine than the other? Explain. Q3. In addition to Brinell and Rockwell hardness testing methods, the following are hardness test methods in practical use: (a) Vickers hardness test, (b) Knoop hardness test, (c) Shore hardness test, and (d) Mohs hardness test. Explain the hardness testing methods (a-d) listed above. Q4. Describe ductility and toughness . Q5. The Hall-Petch relationship states that the tensile yield stress is related to grain size. Write the Hall-Petch equation and explain the mechanism behind the equation. Q6. A rod with initial length l 0 is plastically elongated to a length l 1 = 1.4 l 0 . Calculate the true strain ε for this plastic deformation. Q7. A rod with initial length l 0 is plastically elongated until it fractures at length
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Unformatted text preview: l f . The true strain ε f at fracture is 0.912. If the initial diameter d is 12.7 mm, calculate the diameter at fracture d f . Q8. A test specimen with a gage length of 50 mm and an area of 200 mm 2 is used in a tensile test. During the test, the specimen yields under a load of 98,000 N. The corresponding gage length is 50.23 mm. This is the 0.2 percent yield point. The maximum load of 168,000 N is reached at a gage length of 64.2 mm. Determine the (1) yield strength, (2) modulus of elasticity, and (3) tensile strength. Q9. In Question 8, fracture occurs at a gage length of 67.3 mm. (1) Determine the percent elongation. (2) Determine the percent reduction in area if the specimen necked to an area of 92 mm 2 . Q10. The figure below illustrates the phase diagram of two components with no solid solubility. (1) What is the name of the composition at point C? (2) Describe its characteristics....
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