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Previous Midterms + Finals + Solutions - MECH 210 –...

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Unformatted text preview: MECH 210 – Materials Science and Engineering Term Test 1, Spring Semester 2008 Name: 1. The engineering stress-strain curve for a specimen is given. The original diameter and gauge length of are 25.40 mm and 98.50 mm , respectively. The materials has a Poisson’s ratio of 0.3 (20 points) (a) Determine the modulus of elasticity of the specimen material. (b) What is the 0.2% offset yield strength? (c) Calculate the modulus of resilience of the material. (d) What is the true strain at an engineering stress of 1300 MPa ? (e) Under a load of 710,000 N , what is the gauge length? (f) When the applied load in (e) is completely removed, calculate the length of elastic recovery. (g) At a stress of 800 MPa , what is the diameter within the gauge length. 2. For a factor of safety of 1.5, (a) calculate the maximum working load, in N , for a rod of the same material and size as the specimen in Problem 1. (b) Is the working stress still within the elastic range? (15 points) 3. A steel plate with a through-thickness hole is subjected to a uniform load as shown. It is known that the maximum local stress is 504 MPa . (a) Indicate where this maximum local stress may occur, and (b) calculate the maximum theoretical stress concentration factor. (15 points) 4. If the steel in Problem 3 has a fracture toughness of 24 m MPa , (a) what is the maximum allowable stress to avoid unstable crack propagation? (b) Explain whether your analysis in part (a) generates a valid result. The geometry correction factor for the crack is 1.14. (15 points) 5. For repeated compression-tension cyclic stress cycling with a mean stress of 40 MPa and a stress range of 160 MPa , (a) what is the stress ratio? (b) Sketch the schematic sinusoidal stress-time diagram showing the repeated cyclic stress with magnitudes. (15 points) 6. Briefly answer the following questions. (20 points) (a) What properties of materials are described by S-N curve? (b) Name three examples of stress raisers. (c) What is fatigue limit? (d) What is Mode I crack surface displacement? (e) Given the three curves, which has the lowest mean stress? (f) Explain why surface hardening can improve fatigue property of metals? (g) Which hardness test yields results that can be directly related to the tensile strength of steel? MECH 210 – Materials Science and Engineering Term Test 2, Spring Semester 2008 Name: 1. (a) Determine the four-index indices for direction A shown in the HCP unit cell. (10 points) (b) Draw (1 0 1) and calculate planar density of atoms for this plane for FCC copper having an atomic radius of 0.128 nm. (10 points) (a) (b) 2. Using the photomicrograph shown, determine (a) the ASTM grain size number and (b) the total grain boundary area per unit volume. (18 points) 3. Given the diffraction pattern obtained using monochromatic x-ray of wavelength 0.1790 nm. Determine the atomic radius of the sample. (15 points) 4. In the carburizing process of a steel initially containing 0.45 wt%C in an atmosphere having a constant In the carburizing process of a steel initially containing 0....
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This note was uploaded on 01/07/2012 for the course MECH 210 taught by Professor Hsu during the Fall '08 term at CSU Chico.

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Previous Midterms + Finals + Solutions - MECH 210 –...

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