x4527 - I I.JENSIDEERI 208.021:23 X45cQZ Student Name and...

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Unformatted text preview: I_ I .JENSIDEERI 208.021 :23 X45cQZ Student Name and Number fqflQ‘C 3 fr, L3qu E.S. 021b PROPERTIES OF MATERIALS FINAL EXAMINATION (9m-12noon, APRIL 19, 2003) Professor R.J. Klassen Professor D.M. Shinozaki Department of Mechanical and Materials Engineering INSTRUCTIONS: TIME ALLOWED: 3 HOURS HAND IN THIS BOOKLET WITH YOUR NAME PRINTED AT THE TOP AT THE END OF THE EXAMINATION. 1 page of handwritten notes (8 1/2 x 11", both sides) is allowed. A calculator is allowed No communication with others is allowed at any time. CHEATIN G: University policy states that cheating is a scholastic offense. The commission of a scholastic offence is attended by academic penalties which might include expulsion from the program. If you are caught cheating, there will be no second warning. This exam contains 24 pages with 60 questions. Check to see all pages are here. Computer Answer Sheet: Use pencil to fill in the squares carefully. Hand in sheet at the end of the test. 1. Print your name and student number. 2. Fill in the student number squares. 3. Fill in the CODE with the number 333. 4. Answer 60 questions: variable mark weights as shown: Total=125 marks 5. Fill in the corresponding answers on the computer answer sheet. QU.W.0. "This material has been copied With permission of this Faculty. Any resale or further copying of this material is strictly prohibited." ,, a-.. .4 Student Name and Number Use the following information for questions 1—4 A tensile stress of 67 MPa produces a tensile strain of 3.268 x 10'4 in a specimen. The yield stress is 150 MPa. The Poisson's ratio of this material is 0.33. MARKS 1. The magnitude of the lateral strain, i.e. the strain normal to the 3 direction of loading, when the specimen is loaded to a tensile stress of 150 MPa is about: (a) 2.4% (b) 0.24% (c) 0.024% (d) 0.0024% (e) 0.00024% 2. The Young's modulus of the tensile specimen material is 2 closest to: a) 6.7x10'4MPa b) 67 MPa 0) 205 x 103MPa d) 205 x 106MPa e) 3.268x109GPa The initial gauge length of the tensile specimen is 50.0000 mm. Calculate the length of the gauge at the yield point. a) 50.0000 mm b) 50.0073 mm C) 50.0366 mm d) 50.0732 mm 1 6) 51.3700 mm 4. A tensile specimen having an initial cross sectional area of 10 3 mm2 fractures after necking at a load of 2000 N. The measured ductility is 60% (reduction of area). The true stress (MPa) at fracture is closest to. a) 92 b) 182 c) 500 d) 728 e) 2000 ___L > _I Student Name and Number In Figure l, the axes are not labelled. The correct labels (where distance is interatomic distance) are: CURVE 1 CURVE 2 X—axis Y—axis X-axis Y-axis (a) Energy Distance Force Distance (b) Force Distance Energy Distance (c) Distance Force Distance Energy Distance Energy Distance Force None of the above 6. At a temperature of OK the equilibrium interatomic spacing is 2 expected in Figure l to be at the point: (a) A (b) B (c) C (d) D (6) This cannot be determined from these plots 7. The unit cells for 5 different crystal structures are shown in 2 Figure 2, with each atom in the unit cell shown smaller than full size for clarity. The face centered cubic unit cell and the body centered cubic unit cell are respectively: fcc bcc (a) 4 l (b) 5 1 (c) 3 l (d) 1 3 (e) 2 4 The cubic unit cell of an fcc crystal is shown in Figure 3 without the atoms. The close packed direction in this unit cell is: a) l b) 2 c) 3 and 5 d) 4 e) there is no close packed direction shown Student Name and Number Each unit cell in a body centered cubic crystal structure contains the equivalent of the following number of atoms: (a) 1 (b) 2 (c) 3 (d) 4 (e) 5 For chromium, the crystal structure is body centered cubic; atomic radius=0.1249 nm; atomic weight=52 amu; Avogadro's number=6.02 x 1023 The density (g/cm ) of chromium is closest to. a) 2.08 b) 3.63 c) .63 d) 5.62 e) 7.20 The number of atoms in a lcm sample of pure chromium is closest to. a) 2.78 x 1022 b) 5.57x1022 0) 8.33 1022 d) 2.78 x 1028 e) 5.57 x 1028 If chromium had a face centered cubic crystal structure with a lattice parameter equal to the body centered cubic case, the density ratio (fcc/bcc) would be: (Assume the atomic weights are identical) Student Name and Number The defects in the crystal structure shown below are respectively: 0 O O O O O O O O O O O O O O O 0 000 O O O O O O O 020 O O O 3) O O O O O O O O O O O O O O O O O 1 2 (a) interstitial vacancy (b) substitutional vacancy (c) vacancy substitutional (d) vacancy dislocation (e) vacancy interstitial The concentration of vacancies in a crystal: (a) increases with increasing temperature (b) decreases with increasing temperature (c) does not change with changes in temperature ((1) is proportional to the atomic packing factor (e) is proportional to the lattice parameter Student Name and Number Calculate the composition, in atom percent, of an alloy which consists of 3 wt%Cu and 97wt% Al. The atomic weights for Cu and Al and are 63.55 and 26.98 amu respectively. The answer is closest to: (a) 97 at%Cu and 3 at% Al (b) 3 at% Cu and 97 at% Al (c) 98.7 at% Cu and 1.3 at% Al ((1) 1.3 at% Cu and 98.7 at% A1 (e) 26.9 at% Cu and 73.1 at% A1 Egg The stress which causes this dislocation to move as shown is represented by the following diagram: ('3) (C) (a) r E (e) (d) Student Name and Number 17. In the dislocation shown below, the approximate Burgers 1 vector for the dislocation (assuming a positive line direction lying into the page) is represented most closely by: (e) The Burgers vector cannot be determined. 18. Calculate the fraction of atom sites that are vacant for lead at 2 327°C (just below its melting point). Assume that the energy for vacancy formation is 0.55 eV/atom. The Boltzmann constant is 8.62 x 10'5 eV/atom—K. The absolute temperature in Kelvins is equal to °C+273. (a) 2.2x 1025 (b) 0.241 (c) 0.01 (d) 8.0x 10'5 (e) 2.41 x 10'5 K10 is a parameter that is measured to characterize this property: (a) yield strength (b)Young‘s modulus (c) shear modulus (d) fracture toughness (e) Poisson's ratio Student Name and Number 20. The Charpy test is used to measure: 2 (3) K1: (b) the energy absorbed by a sample during fracture (c) the yield stress ((1) the length of the largest flaw (e) the Poisson's ratio 21. A ceramic part, having a fracture toughness of KIC = 5 MPa.mI 2, fails in 3 tension at 500 MPa. Microscopy reveals a flaw (0.005 mm long) in the surface of the failed part which caused the failure. The failure stress for the same material containing a larger, 0.095 mm long, surface crack is closest to: a) 16.2 MPa b) 70.7 MPa 0) 118 MPa d) 500 MPa e) The failure stress cannot be calculated fiom the data given. 22. Figure 4 shows a fracture surface of a broken steel shaft. The fracture 1 is most likely due to: (a) creep (b) fast tensile testing (c) fatigue (d) Charpy testing (e) brittle fracture 23. A standard engineering fatigue test results in graphical plot called an SN 1 curve. The S and N refer to: S N (a) mean stress maximum stress (b) range of stress number of cycles to failure (0) minimum stress maximum stress ((1) stress amplitude plastic strain to failure (e) stress amplitude number of cycles to failure Student Name and Number Aluminum Low Alloy Steel Stainless Steel Brass Zirconium Alloy - alloy (304 (Naval, sand (Reactor Grade) (6061 -T4) annealed) cast) 1 3 lim— mum-.12- Elli-m WWW mm“ Ultimate tensile W 1150 MPa 620 MPa 310 MPa w strength maximum stress m2- TABLE 1 24. A sinusoidal alternating tensile load is applied to the cylindrical specimens (do=l .0 cm and length 10:10.0 cm). The maximum and minimum tensile loads are +13,000 N and -13,000 N. For specimens made of each of the 5 metals in Table 1, only the following metals would survive without failure: (a) 2,3,5 (b) 2,3,5,4 (c) 2,3,5,4,1 (d) 2,3 (6) 2 25. An increasing grain size affects mechanical properties of a metal in the 2 following way: (a) the yield stress increases (b) the yield stress decreases (c) the elastic modulus increases (d) the creep rate increases (6) the hardness increases 26. During an annealing process for a cold worked metal sample held at the 1 annealing temperature, the following steps are observed in the order: (a) recrystallization, recovery, grain growth (b) recovery, grain growth, recrystallization (c) grain growth, recrystallization, recovery (d) recrystallization, grain growth, recovery (e) recovery, recrystallization, grain growth Student Name and Number A line 12.5 cm long on a micrograph of annealed aluminum taken at a magnification of 750X intersects 75 grains. The average grain “diameter” is therefore between: (a)0-1um (where 1pm: 1 x 10'6 m) (b)1-2Mm (c)2-3nm (d)3-4um (e)4—5um A metal alloy is required to have a yield strength of at least 345 MPa, and a ductility of greater than 20%. They can be cold worked once if necessary. Of the three alloys in Figure 5, which ones can be used? (a) 1040 steel only (b) brass only (0) copper only ((1) 1040 steel and brass (e) brass and copper An annealed copper rod with a circular cross-section (initial diameter 10 mm) is cold worked 20% using a drawing process. The diameter after the cold work is closest to: a) 8.944 mm b) 8.000 mm c) 4.472 mm d) 2.828 mm e) 1.414 mm 30. An annealed copper rod with a circular cross-section (initial diameter = 3 10mm) is cold worked 20% using a drawing process, fully annealed and further cold worked 10%. The diameter is now closest to: a) 8.485 mm b) 8.000 mm c) 7.000 mm d) 2.837 mm e) 2.705 mm 10 Student Name and Number 31. TStarting with an annealed copper sample, it is cold worked 20%, ’ annealed, then cold worked 10%. The tensile strength (MPa) is closest to: (Use Figure 5 a) 210 b) 260 c) 295 d) 325 e) 360 F32. Elastic deformation changes the yield strength of metal because: (a) Young‘s modulus increases. (b) Young's modulus decreases. (c) The number of vacancies increases. (d) elastic deformation does not change the yield strength (e) The number of entangled dislocations increases. The steady state creep strain rate for a metal follows the functional form (the student is expected to know the definitions of each term: R is the gas constant): - n Q 8=KO' ex — c ‘ 2 pi RT (é, = da/dt) Experimentally the steady state creep strain rate is measured for a number of temperatures at a given stress. Select the graphing and analysis procedure from which one could deduce the activation energy for creep: X-axis Y-axis Slope (a) In as l/R Q, S (b) lné l/T QC 11 Student Name and Number 34. 35. 36. 37. Marks Tempering of glass involves: (a) heating the glass and then slowly cooling (b) heating the glass then rapidly cooling (0) heating the glass and drawing in tension (d) heating the glass and rolling the sheet (e) cooling the glass below the glass transition temperature The coordination number is: (a) number of close packed planes in a unit cell (b) number of close packed directions in a unit cell (c) number of nearest atomic neighbours (d) volume of atoms/volume of unit cell (e) number of interstitial atoms per unit volume The crystal structure of a ceramic containing the elements Cs and Cl is shown in Figure 6. The chemical formula for this compound is: (a) CsCl (b) CSZCI (c) Cscl2 (d) CsC14 (e) CsCi8 A smooth sample of a ceramic bar has a rectangular cross section 2 (h=6mm and w=12mm) and is tested in bending (d=55mm) (Figure 7). At fracture the applied load F=90N. The flexural strength is closest to. (a) 7.8 MPa (b) 17.2 MPa (c) 78.3 MPa ((1) 17.2 GPa (e) 78.3 GPa 12 Student Name and Number R's.“ In Figure 8, the upper and lower boundaries of the range A marked on the graph represent: Upper Lower (21) strain point annealing point (b) annealing point softening point (c) softening point working point (d) working point melting point melting point (e) strain point In Figure 8, the material which must be formed at the highest temperature is: (a) soda-lime glass (b) borosilicate glass (0) 96% silica glass (d) fused silica (e) it is not possible to make this selection from this graph Figure 9 is a diagram representing the manufacturing process: (a) compression molding (b) injection molding (c) slip casting (d) blow molding (e) tape casting Wei - ht fraction fraction 7500 12500 17500 22500 27500 Table 1 13 Student Name and Number 41. From the data provided in Table 1 for avpolymer, the number average 3 molecular weight of the polymer is closest to: a) 17,950 b) 18,750 c) 19,700 d) 20,650 6) 21,500 42. The approximate molecular weight of a PVC molecule (a part of a 2 molecule is shown in Figure 10) with a degree of polymerization of 625 is closest to. a) 625 amu (or g/mole) b) 19,500 c) 39,000 (1) 62,500 e) 78,000 The atomic masses of H, C and C1 are l, 12 and 35.5 amu (atomic mass units or g/mole) respectively. As the temperature decreases between the melting temperature and the glass transition temperature, the stiffness (modulus) of a thermoplastic polymer: (a) increases (b) decreases (0) remains approximately constant ((1) increases, then decreases as you approach Tg (6) decreases, then increases as you approach Tg A single polymer chain is comprised of atoms that are bonded by: a) metallic bonds b) ionic bonds 0) covalent bonds d) Van der Waal’s bonds 6) hydrogen bonds 14 Student Name and Number 45. In Figure 11, a specimen is subjected to the load in (a), and the three 2 different possible strain responses in the specimen are shown in (b), (c) and (d). The strain responses are: b c d (a) elastic viscoelastic viscous (b) elastic viscous viscoelastic (c) viscous viscoelastic elastic (d) viscoelastic viscous elastic (e) viscoelastic elastic viscous 46. A creep test involves fixing one parameter and measuring the relationship 3 between the following two parameters: a) stress and time b) stress and strain c) strain and time (1) strain and ductility e) stress and Poisson's ratio 47. The tensile strength of a polymer changes in the following manner with 2 increasing temperature: it (a) decreases (b) increases (c) increases then decreases (d) is unchanged (6) increases only at temperatures above the melting point 48. In Figure 12, the curves labelled A, B and C represent polymers which 2 are: A B C (a) partly crystalline amorphous completely crystalline (b) completely crystalline amorphous partly crystalline (c) amorphous completely crystalline partly crystalline (d) amorphous partly crystalline completely crystalline (e) partly crystalline completely crystalline amorphous 15 Student Name and Number Information for questions 49-51. A fibre reinforced composite is made of 25% (volume) glass fibers in an epoxy matrix. The fibres run the full length of the sample and are aligned in the direction of tensile loading. A test sample of the composite measures 5 mm x 5 mm in cross-section, and has a gauge length of 100 mm. The properties of the glass and epoxy are given in the Table below. Modulus MPa 75 GPa 250 MPa a does not yield (20 m dia.) E - ox _ 49. Calculate the modulus of the composite parallel to the fibers in GPa: 3 (a) 75.0 (b) 42.6 (c) 35.6 (d) 28.7 (e) 20.3 50. Calculate the modulus of the composite perpendicular to the fibers in 3 GPa: (a) 2.00 (b) 2.64 (c) 4.63 (d) 7.00 (e) 42.6 51. When a load of 300 N is applied to the composite parallel to the fibers, the 3 stress in the fibers is closest to (MPa) (a) 81.0 (b) 69.1 (c) 44.4 (d) 20.3 (e) 7.0 52. If the fibre/matrix bond shear strength is 10 MPa, the critical fibre length 2 is closest to (m) (a) 25 (b) 2.5 (c) 0.25 (d) 0.025 (e) (e) 0.00025 16 Student Name and Number A pultrusion process is one in which (a) short fiber composites can be made into any shape (b) continuous fibers composites can be made into tubes, rods, or bars with constant cross sectional shape (c) an extrusion process for crystalline polymers (d) a reverse injection molding process for amorphous polymers (e) a glass forming method Information for questions 54-56: For copper, assume the electrical conductivity is 6.0)(107ohm'1m'1 ; the mobility of electrons is 0.0030 mZ/V—s; the charge on one electron is 1.6x10'19C. 54. The electrical resistance of a copper wire (diameter=3mm, 1ength=20m) is 2 closest to (in ohms): (a) 0.018 (b) 0.032 (c) 0.047 (d) 0.180 (6) 0.790 55. The number of electron charge carriers per m in copper is closest to: 3 (a) 6.00x107 (b) 6.25x1018 (c) 1.60x1019 (d) 2.10x1021 (e) 1.25x1029 56. The average drift velocity (in m/s) of the electrons moving when a 3 potential of 4 volts is applied to a copper wire 4 m long is closest to: (a) 7.5x10“1 (b) 3.0x10'3 (c) 1.2x10'2 (d) 1.0 (e) 4.0 57. The device shown in Figure 13 is a: 3 (a) n-p-n junction transistor (b) p-n-p junction transistor (c) n-p-n rectifying junction (diode) (d) p-n-p rectifying junction (diode) (6) field effect transistor 17 Student Name and Number One way to distinguish a semiconductor from a metallic conductor is: (a) to measure the resistance as a function of plastic deformation (b) to measure the melting temperature (c) to measure the grain size ((1) to measure the resistance as a function of temperature (6) to determine the optical transparency 59. The energy gap between the valence band and the conduction band in silicon is 1.1 eV and in germanium it is 0.7 eV. The mobilities of holes and electrons are similar for the two materials. On the basis of this information it can be stated that: a) it is probable that the conductivity of silicon is greater than the conductivity of germanium at room temperature b) it is probable that the conductivity of germanium is greater than the conductivity of silicon at room temperature c) it is probable that silicon and germanium have the same conductivity at room temperature (1) it is likely that the conductivity of germanium will become equal to that of silicon if its temperature is raised 6) adding germanium to silicon will increase the conductivity of silicon by changing it to an extrinsic semiconductor. 60. A p type dopant causes mfg—holes/m to be generated in a block of silicon. Calculate the conductivity of this p-type silicon given that the conductivity of pure silicon is 10'10 Q] m"‘, charge/carrier=1.6x10‘19 C, mobility of electrons=0.19 m2.V" s1, mobility ofholes= 0.05m2V'IS‘1. a) 10'10 (2'1 m'1 b) 0.03 9" m" c) 0.008 Q" m"1 d) 0.038 Q" m'1 e) 0.08 o“ m" 18 Student Name and Number Figure 2 Figure 1 3 UPLI‘UY‘; i)“ fpt‘gflu-h- Figure 4 19 Student Name and Number 1040 Steel 1040 Steel Yield strength (MPa) A m ’2 l g; 2 v V c a E” 5 fl) _ e 17. a 'U 2 a.» 'g >- .2 10 20 30 4O 50 60 70 ' I 10 20 3O 40 50 60 Tensile strength (ksi) Percent cold work 1 Percent cold work (a) ( b) Ductility (%EL) 20 30 4D 50 6O 70 Percent cold work (0) Figure 5 20 Student Name and Number 21 Student Name and Number Borosil icate glass 96% silica Fused glass silica Viscosity (Pa-s) Soda~|ime glass 600 800 1000 1200 1400 Temperature (°C) 1600 18( Figure 8 Units: 1 Pa-s = 10 Poise (P) Draining mold Top trimmed Finished piece 22 Student Name and Number G.) E ..E C7 > a.) :“E L; Q) C3... U3 Figure 11 Team peratu re Figure 12 23 Student Name and Number Silicon doped with Aluminum Silicon doped with Phosphorous Silicon doped with Phosphorous Input Voltage Output Load Valence of Silicon = 4, Phosphorous = 5, Aluminum = 3 Figure 13 24 ...
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x4527 - I I.JENSIDEERI 208.021:23 X45cQZ Student Name and...

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