MECH 390 - PRACT ICE 1 – FALL 2011 – SEC 51,52,03Name:___________________________ Number:_______________________ 1. Which of the following materials may form crystalline solids? A. B. C. D. E. Polymer s Metals Ceramic s All of the above None of the above Student 2. The drawing below represents the unit cell for which crystal structure? A. B. C. D. Simple cubic Face-centered cubic Body-centered cubic Hexagonal closepacked 5. 6. If the atomic radius of a metal that has the face-centered cubic crystal structure is 0.137 nm, calculate the volume of its unit cell (in nm3). For a metal that has the body-centered cubic crystal structure, calculate the atomic radius (in nm) if the metal has a density of 7.25 g/cm3 and an atomic weight of 50.99 g/mol. For the face-centered cubic crystal structure: (a) How many atoms are associated with each unit cell? (b) What is the coordination number? (c) What is the atomic packing factor? 7. 8. What is the difference between atomic structure and crystalline structure. 9. It is possible to produce a perfect crystalline solid that does not contain any vacancies. A.True A.True B.False B.False 10. The solute is an element or compound present in the greatest amount. 49 g/cm3. 19.11. respectively. and (b) of Sn (in at%)? The atomic weights for Pb and Sn are 207.63 eV/atom. respectively.32 and 10. 16. 13. The number of vacancies in some hypothetical metal increases by a factor of 5 when the temperature is increased from 1070 K to 1180 K.5 mm long of a low carbon-nickel alloy is to be exposed to a tensile stress of 70 MPa at 427°C. The densities of pure gold and silver are 19. Compute the stress ratio C. Zn. what are the concentrations (a) of Cu (in at%). Two metal specimens. 15. Calculate the number of gold atoms per cubic centimeter (in atoms/cm^3) for a silver-gold alloy that contains 21 wt% Au and 79 wt% Ag. 17. respectively. Which specimen has the larger grain size? A. A and B. Compute the magnitude of the stress range 18.2 and 118. have ASTM grain size numbers of 3 and 8. Gold forms a substitutional solid solution with silver. 65. Determine its elongation after 10. and their respective atomic weights are 196. and Pb are 63. what is the composition (a) of Pb (in at%). Compute the maximum and minimum stress levels B. respectively.7 g/mol. 113 g zinc.2 g/mol. 14.3 mm. A steel bar (1045 steel) is subjected to a repeated compression-tension stress cycling along its axis. For an alloy that consists of 94. . A fatigue test was conducted in which the mean stress was 70 MPa and the stress amplitude was 210 MPa A.97 and 107. A specimen 101. and 8.87 g/mol. Calculate the energy for vacancy formation (in J/mol) assuming that the density of the metal remains the same over this temperature range. If the amplitude is 66700 N. Assume that the total of both instantaneous and primary creep elongations is 1.36 g lead.3 wt% Sn. Assume an energy for vacancy formation of 0.000 h.7 wt% Pb and 62. 12.6 g copper.55. B. find the minimum allowable bar diameter to assure fatigue will not occur by a safety factor of 2. Calculate the fraction of atom sites that are vacant for silver at 661°C. and 207. For an alloy that consists of 37. (b) of Zn (in at%). and (c) of Pb (in at%)? The atomic weights for Cu.39. a.750 N. ksi 21. b. A cylindrical specimen of a brass alloy 10.20. A cylindrical specimen of some alloy 8mm in diameter is stressed elastically in tension A force of 15700 N produces a reduction in specimen diameter of 5 x 10-3 mm. Tensile stress-strain behavior for an alloy steel is shown in the Figure below.2%offset) in MPa Ultimate tensile strength in MPa Total percent elongation (%EL) Proportional point Toughness Resiliance 20. Compute Poisson’s ratio for this material if its modulus of elasticity is 140GPa. the force is subsequently released. E. Yield strength (0.0 mm long is pulled with a force of 11. B.500 N and then released . D. Creep ksi. List the following material parameters: A. F. C. Compute the final length of the specimen at this time.0 mm in diameter and 120. stress rapture is given by the equation: . Find the time to rapture when stress =100 20 10 data for S-590 Iron 1 12 16 20 24 28 L(103K-log hr) 22. Compute the final length when the specimen is pulled with a load 23. 100 Stress. The tensile stressstrain behavior is shown below. specify equations relating tensile stress and Brinell hardness for brass and nodular cast iron similar to equations 6. Using the data represented in Figure 6.20a and 6. 25. what is the carbon content 0. If the concentration of carbon at the surface is suddenly brought to and maintained at 1. Consider an alloy that initially has a uniform carbon concentration of 0.24.25 wt%.19.5 mm below the surface after 8 hours? The diffusion coefficient for carbon in iron at this temperature is 1.20b for steels. .6 ×10-11 m2/s.25 wt% and is to be treated at 1020oC. Non-steady state diffusion is given by: x C(x.assume that the steel piece is semi-infinite. t) − C o = − 1 erf 2 Dt Cs − C o .