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X4192 - I—_I OU.W0'Thisnmuhihabmeqid —...

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Unformatted text preview: I—_I OU.W0.'Thisnmuhihabmeqid — éfi/G/n/éZW/A/JJ \i’IéZ/CL bail/g Esozik fimggp‘hiflmmn DEZLJéf/o/ (/é) X 9/9912 Final Exam Emmy” _‘_..a Short Answer Questions STUDENT NAME: STUDENT NUMBER: The University of Western Ontario Faculty of Engineering Science ES 021a — Properties of Materials Final Exam December 14, 2001 2:00 pm - 5:00 pm Time: 3 hours Aids: Programmable calculators 1 Crib Sheet 81/2” X 11”, both sides Not Professionally Produced Format: 47) Multiple choice questions to be answered on the form provided 5)Short answer questions to be answered in the space provided UNIVERSITY POLICY STATES THAT CHEATING IS A SCHOLASTIC OFFENSE. 3 THE COMMISSION OF A SCHOLASTIC OFFENSE IS ATTENDED BY ACADEMIC ; PENALTIES WHICH MIGHT INCLUDE EXPLUSION FROM THE PROGRAM. IF YOU i ARE CAUGHT CHEATING, THERE WILL BE NO SECOND WARNING Record your answers to the multiple—choice questions as on the form below: PRINT NAME INSTRUCTOR SIGNATURE COURSE If your student number has fewer than 9 digits, add lead-off zeroes. IMPORTANT HB PENCIL ONLY! EXAMPLE: (1‘. I it :3!) [E1 ERASE CDMPLETELYTD CHANGE Page 1 ofl6 we; .Deeember 14, 2001 , , 9? musing-52.5 Jana as MULTIPLE CHOICE QUESTIONS (49 Marks) (All questions worth one mark unless otherwise noted) ES 021 Final Exam Pick the closest value in the following questions. The following data relates the properties of an annealed low carbon steel sample and is to be used to answer Questions 1) - 7). Gauge area 0.4418 cm (i.e. diameter was 0.750 Gauge length 5.00 cm cm) _— 1) The force applied to the sample when the stress was 45 MPa was: a) 19.9 Pa b) 1.99 x 103 N c) 3.38 x 105 Pa d) 1.019 x108 N c) 1.019 x1012 N 2) The gauge length when the stress was 45 MPa was: a) 2.14 ><1o4 cm b) 5.0002 cm c) 5.0011 cm (1) 5.158 cm 6) 5.789 cm 3) The change in the diameter of the gauge section when the stress was 45 MPa would be: a) —5.3 x 10'5 cm b) —9.42 x 10'5 cm c) +9.42 X 10'5 cm d) —1.61><10“1 cm e) —2.14 ><10‘1 cm 4) The minimum diameter of a rod of this steel required to withstand an alternating load of £1500 N indefinitely would be in the range: a) 0.4 — 0.5 cm b) 0.5 — 1.0 cm c) 1.0 — 2.0 cm (1) 2.0 — 3.0 cm e) > 3.0 cm Page 2 of 16 ES 021 December 14, 2001 Final Exam 5) The true stress at fracture was: a) 80 MPa b) 180 MPa 0) 288 MPa d) 405 MPa 6) 2.88 ><1013 Pa 6) If the grain size was increased to 45 um (1 urn = 1><10'6rn) the yield strength would be approximately: (2 Marks) a) 25 MPa b) 75 MPa c) 130 MPa d) 675 MPa e) 2025 MPa 7) If the grain size was increased to 45 um the hardness would be approximately a) 30.6 VHN b) 91.7 VHN c) 159 VHN d) 825 VHN e) 2475 VHN 8) The crystal structure shown in the diagram is: a) BCC b) FCC c) HCP d) Metallic e) Ionic 9) A close—packed direction would be: a) A - B b) A — C c) A — D d) A — E e) There are no close—packed directions 10) The number of atoms in the unit cell shown is: a) 1 b) 2 c) 3 d) 5 e) 9 Page 3 of 16 ES 021 December 14, 2001 Final Exam 11) The diameter of a brass rod is cold reduced from 1 cm to 0.8 cm. The rod is then annealed and further reduced to 0.7 cm. At this point the ductility of the brass is approximately: a) 3% b) 4% c) 13% a d) 18% a: e) 37% :33 E 0 10 20 30 40 50 60 70 Percent cold work Questions 12) to 19) refer to the following Fe—C phase diagram . 1493éc Temperature 19C)" - , (F )1" ‘ . - Composition (wt% C) Page 4 of 16 ES 021 , December 14, 2001 Final Exam 12) The liquidus temperature of Fe — 3 wt% C is approximately: a) 400°C b) 727°C c) 1147°C d) 1250°C 6) above 1300°C 13) The alloy Fe - 3 wt% C has a freezing range of: a) less than 40°C b) between 40 and 75°C 0) between 75 and 125°C d) between 125 and 175°C e) greater than 175°C 14) The composition of the first solid to form on slowly freezing Fe - 3 wt% C is about: a) pure Fe b) Fe - 1.3 wt% C c) Fe - 2.14 wt% C d) Fe - 3 wt% C e) Fe - 4.30 wt% C 15) The composition of the eutectic that forms when Fe - 3 wt% C is cooled slowly is about: a) Fe - 1.36 wt% C b) Fe - 2.14 wt% C 0) Fe ~ 4.30 wt% C d) Fe - 6.70 wt% C e) no eutectic forms 16) An alloy containing Fe - 6 wt% C is slowly cooled from the liquid. The arriount of primary (or dendritic) Fe3C that forms is about: a) <20% b) 20 — 40% c) 40 — 60% d) 60 ~ 80% e) >80% 17) On slow cooling from 950°C an Fe - 0.4 wt% C steel first forms ferrite at about: a) 727°C b) 800°C c) 912°C d) 1493°C e) 1510°C Page 5 of16 ES 021 December 14, 2001 Final Exam 18) At room temperature an Fe 0.4 wt% C alloy would be composed of about: a) 0% ferrite / 100% pearlite b) 6% ferrite / 94% pearlite c) 48% ferrite / 52% pearlite d) 52% ferrite / 48% pearlite e) 94% ferrite / 6% pearlite 19) The microstructure is of an Fe - 0.76wt% C alloy. It appears to be: a) austenite b) martensite c) bainite d) ferrite e) pearlite FIGURE 10.14 The 800 complete isothermal transformation diagram for an iron—carbon 700 alloy of eutectoid .; composition: A, austein'tc; ‘B, bainite; M1 600' martensite; P. pearlite. S 500 Temperature (‘0) 8 O Temperatune ('F) 300 600 200 400 100 200 Time (s) 20) A 1080 steel component is rapidly cooled to 600°C where it is held for 3 seconds and then quenched to room temperature. Its structure would then be: a) 100% austenite b) 100% pearlite c) 100% martensitc d) 50% austenite 50% pearlite e) 50% pearlite 50% martensite Page 6 ofl6 ES 021 December 14, 2001 Final Exam 21) A 1080 steel component is rapidly cooled to 300°C where it is held for 3 seconds and Diameter of bar (mm) then quenched to room temperature. Its structure would then be: a) 100% austenite b) 100% pearlite c) 100% martensite d) 50% austenite 50% pearlite e) 50% pearlite 50% martensite 100 75‘ Diameter of bar (in.) Hardness HRC 25 Distance from quenched end Equivalent distance from quenched end 22) A 10 cm diameter bar of 1040 steel is quenched from 850° (curves above). The hardness of the surface of the bar would be in the range: a) 50—60Rc b) 40—50Rc c) 30—40Rc d) 20—30Rc e) lower than 20 Re 23) A 10 cm diameter bar of 4140 steel is quenched from 850°C. The hardness of the center of the bar would be in the range: a) 55-60Rc b) 50—55 Re C) 45—50Rc d) 40—45Rc e) 35-40Rc Page 7 of16 ES 021 December 14, 2001 Final Exam \\ _ \ N I ~ - / ” u H '\ fi‘ 5, u tr. )C‘“ c: ~ H \ a IC..C"’I . 0‘” u-L.“ k If I C=Lv \ I, ‘CI“ “4 ‘ s’cvu m “I ‘f ,C’ MD H /c¢c‘ '1‘ :1 H‘ )0 ")c j ‘ ‘c, k a H 01-: “‘c. ”‘C~ ‘l \ / '/ H ” Q a I / ‘l/fl-C‘H Muc‘ . fl'c‘” .1 \c \ ,1 C. "I T; c\\ ’“ u H ' c .. ‘ \\ u u’ u 4 ,[email protected] C ' (t g 24) The bonding between points A-B would be: a) ionic b) covalent c) metallic (1) van der Waals e) hydrogen 25) The bonding between points A-C would be: a) ionic b) covalent c) metallic d) van der Waals e) hydrogen 26) The bonding between chain fragments 1—2 would be: a) ionic b) covalent c) metallic (1) van der Waals e) hydrogen 27) The bonding between chain fragments 1-3 at point “D” would be: a) ionic b) covalent c) metallic (1) van der Waals 6) hydrogen Page 8 of16 ES 021 December 14, 2001 Final Exam 28) The number of mers between points 2—2 is: a) l b) 2 c) 3 d) 4 e) indeterminate 29) The polymer chain fragment 2-2 is: a) isotactic b) atactic c) syndiotactic d) neotactic e) this type of classification is not applicable 30) The polymer is basically of the type: a) linear b) network 0) thermosetting d) crystalline e) block 31) The junction between the three parts of polymer chain “1” at the point B: a) could never occur in reality b) is termed vulcanizing c) is termed cross linking d) is termed incipient crystallization e) is termed branching 32) In the diagram of a silica-based glass, the smallest atoms are: a) silicon b) oxygen c) a glass former d) a glass modifier e) could be lead 33) The biggest atoms are: a) silicon b) oxygen c) a glass former d) a glass modifier e) could be lead Page 9 ofl6 ES 021 December 14, 2001 Final Exam 34) A brittle material has an effective strength of 1700 MPa when internal flaws are 100 um in diameter. The fracture toughness of the material is therefore in the range: (Assume K ,C = 0.9 (xx/E where the symbols have their usual meaning.) (2 Marks) a) 19.2 MPm/Z b) 171 MPH; c) 19.2 x 10’3 MPH; d) 19.2 x 106 MPH; e) 1.71 x 109 MPaJ; 35) The diagram at right contrasts the volume - temperature relationship for a glass and for a crystalline material. The line on the diagram that relates to a glass object in use would be: a 1—2 b) 2—3 0 3—4 (1) 5—6 e) 2—5 36) The change in slope of the volume — temperature relationship at the junction of the segments 2-3 and 3-4 2.) defines the melting temperature b) defines the glass transition temperature c) defines the crystallization temperature d) defines the homologous temperature e) defines the tempering temperature 37) The bifurcation (forking) of the curves at point 2 in the graph: a) defines the melting temperature b) defines the glass transition temperature 0) defines annealing temperature d) defines the homologous temperature e) defines the tempering temperature 38) The line on the diagram that relates to annealing a glass object would be: a 1—2 m 2—3 0 3—4 Q 5—6 a 2—5 Page 10 ofl6 ES 021 December 14, 2001 Final Exam 39) When making a traditional ceramics one starts with clay, silica, feldspar and water. The purpose of the water is to: a) make the ceramic cheaper b) to provide water of crystallization for the crystalline components c) to make the ceramic lighter d) to make the final product more plastic e) to make the original mix more plastic 40) When a tensile specimen is made from the polymer shown in the diagram is held at a strain of ‘A of the yield strain (as in Lab 3) the load changes with time aCcording to the following diagram: This reduction of stress with time is known as: a) Viscoelestic behaviour b) necking 0) chain orienting d) craze formation e) micro-voiding 572:8 41) On a molecular level the reduction of stress with time is due to: ‘77,"5 a) polymer chains breaking b) polymer chains sliding past each other c) polymer chains crystallizing d) polymer chains cross-linking e) polymer chains branching 42) If the initial stress “A” was doubled the best estimate of the final stress “B” would be: a) A + B b) 2A + B c) 2A - B cl) 2A - 2B e) 2B 43) The resistivity of pure copper is 8.0 X 10'8 Q-m. It is found that the resistivity of the copper increases: 10% on heating, 5% on cold work, and 15% on alloying. The best estimate of the resistivity of hot, cold worked alloy is: _ a) 2.13 x 10'8 Elm b) 9.6 x 10:89:11 c) 1.0X10'8Q-m d) 1.52 x 10'7Q-m e) 3.0 x 10'7Q-m Page 11 of16 ES 021 December 14, 2001 Final Exam Questions 44) — 47) refer to a piece of intrinsic silicon measuring l><2><50 cm whose resistance along the length at 25 °C is 5 X 106 Q. 1e|=q=1.6x10"9c, 218:0.19 mZV'1s", ,uh=0.05m2V'ls'1 . 44) The conductivity of the silicon is approximately: a) 8 x 10'11 mm] b) 5 x 10‘4 Q"~m" c) 1000 9‘1 -m'1 d) 2000 mm" c) 1.25 x 10” Q'l'm'l 45) The resistivity of the silicon is approximately: a) 8 x 10'” Q-m b) 5 x 10“ om c) 1000 (21m d) 2000 Q-m e) 1.25 x 1010 (2m 46) The total number of charge carriers/meter3 is approximately: a) 2.2 x 1022 m'3 b) 1.3 ><.1016 m'3 c) 7.5 x 1014 m'3 d) 5.9 x 10‘4m'3 e) 2.1><109 m'3 47) The number of electrons carrying the current would: a) be equal to the number of positive holes b) be greater than the number of holes by the ratio O.l9/0.05 c) be less than the number of holes by the ratio 005/019 (1) be very much greater than the number of holes e) be very much less than the number of holes Page 12 ofl6 ES 021 December 14, 2001 Final Exam SHORT ANSWER QUESTIONS Answer in the space provided 1) The following diagram shows the interactive forces between two atoms as they are brought together from an infinite separation. a) On the axes provided, draw the related diagram of Energy vs. Separation. (4 Marks) b) On the axesof your diagram, clearly indicate the equilibrium separation of the atoms and how the equilibrium spacing is related to any features of the Energy-Separation curve. (2 Marks) c) On the original diagram, indicate graphically the mathematical operation required to calculate the bond energy at point ”X”. (2 Marks) i Attractive force FA 1\ Atttzction —_—). Interatomic separation, r Force F 0 Energy Repulsion .4.— Net force FN Page 13 of16 ES 021 Final Exam 2) From the information on the iron—carbon phase diagram below: a) Enter the names that correspond to the Greek letter labels in the table below. (The first entry is done for you.) (3 marks) b) Circle the eutectic reaction and label it with an A (1 mark) c) Circle the eutectoid reaction and label it with a B (1 mark) d) For the equilibrium microstructures shown below, mark an X on the phase diagram where that structure would be present and label it with the corresponding letter. Be very clear in describing if the point must be above/below/lefi/right of a particular feature on the phase diagram. (5 marks) Temperature ['C) December 14, 2001 Common Name layered (X + FC3C 3 4 5 6 Weight percent carbon Page 14 ofl6 ES 021 December 14, 2001 Final Exam 3) Complete the following diagram to show the stress distribution across a plate of tempered glass. a) with no external load (4 Marks) hart T/IIcK/VESS ‘ com fltE${/Y£ 5771555 754614;“ b) with an external load that gives an average stress of 20 MPa. Give realistic values of stress. (4 Marks) PLATE TflIaKN£SS ‘ (—om IKE $6 1Y5 $172555 . 75’9“? 4) The diagram shows a normal tensile test results from a polymer sample. a) In the sentence below, circle the correct word in bold type and complete the following sentence. (2 Marks) The polymer sample must be above / below its glass transition temperature because it b) Add additional stress-strain relationships to the diagram illustrating what would happen to the data if: i) the strain rate of the test was decreased (2 Marks) ii) the strain rate of the test was increased (2 Marks) iii) if the test temperature was increased. (2 Marks) 5) Stress Page 15 ofl6 ' Strain ES 021 December 14, 2001 Final Exam Use the accompanying figure of an p-n-p bipolar junction transistor to complete the following questions: a) The three sections of the device have been labeled as the emitter, base and collector. Label the terminals of the input voltage source (+ve and -—ve) so that emitter is in forward bias. (1 mark) b) Label the terminals of the output voltage source so that the device will operate correctly. (1 mark) c) Using the symbols e' and h+ to represent electrons and holes respectively, show how the charge carriers in each section of the device move when the device is operating properly. (3 marks) 11 d) If the input voltage is 0.5V, the input current is 10 mA, and the output voltage is 20V, calculate: i) The input power including the correct units (1 mark) ii) The approximate output power (including units) for a well—constructed device (IBzO). (1 mark) Page 16 of 16 ...
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