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ENB110-T1-S2-2010

# ENB110-T1-S2-2010 - |||||||I|||||I| Surname Given Name/s...

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Unformatted text preview: |||||||I|||||I| Surname Given Name/s III-III- Examination Paper SEMESTER: SECOND SEMESTER EXAMINATIONS 2010 UNIT: ENB110 ENGINEERING STATICS AND MATERIALS - THEORY 1 DURATION OF EXAMINATION: PERUSAL: 10 MINUTES WORKING: 2 HOURS EXAMINATION MATERIAL SUPPLIED BY THE UNIVERSITY: EXAMINATION BOOKLETS FORMULA SHEET - ONE (1) PAGE ATTACHED EXAMINATION MATERIAL SUPPLIED BY THE STUDENT: WRITING IMPLEMENTS CALCULATORS - ANY TYPE INSTRUCTIONS TO STUDENTS: Students are prohibited from having mobile phones or any other device capable of communicating information (either verbal or written) in their possessions during the examination NOTES MAY BE MADE QNLX ON THE EXAMINATION PAPER DURING PERUSAL TIME ALL SIX (6) QUESTIONS ARE TO BE ATTEMPTED ALL QUESTIONS ARE OF EQUAL VALUE Queensland University of Technology GUT Gardens Point GUT Kelvin Grove GUT Caboolture 1 All 6 Questions are to be Attempted All Questions have Equal Weighting QUESTION 1 Stress-Strain Curve of Engineering Materials Figure 1 is the stress—strain curve for a cylindrical specimen steel of 8.5 mm in diameter and 80 mm long that is pulled in tension. Show all necessary steps when answering the following questions: a. Calculate the Young’s Modulus and %EL of the alloy. b. Determine the 0.2% off-set Yield Stress and Tensile Strength of the alloy. 300 Stress (MP3) Stress (103 psi) 100 09000 0.005 0.010 0.015 Strain 0 0.000 0.020 0040 0.060 0.080 Strain Figure 1 Stress-strain curve of steel obtained in a tensile test. QUESTION 2 Crystal structures Determine the atomic packing fraction (APF) of body centred cubic (BCC) crystal structure. Show all the necessary steps and write the assumptions you have made in your calculation. QUESTION 3 Defects in Solids What are dislocations? Explain how they are created, and why they are important in metals. QUESTION 4 Strengthening of Metals (a) Brieﬂy explain why HCP metals are typically stronger and more brittle than metals with FCC. (1)) Explain the effect of reducing grain size on the strength of metals. ENB110T1.102 cont/... 2 QUESTION 5 Equilibrium Phase Diagram Using the Cu-Ag phase diagram (Figure 2), answer the following questions for an alloy of 35wt% Ag: (a) What are the phases obtained at a temperature just above 780°C? (19) Determine the composition of the phases at 780°C? (0) Sketch the microstructure you would expect for the material after solidiﬁcation is completed. Composition (anus) A O 20 4O 60 80 100 2000 1800 1 600 1400 Temperature 1°C) Temperature (“H 1200 1000 H I 800 0 20 40 60 80 100 (Cu) Composition (M%Ag) (All Figure 2 Copper-Silver Equilibrium Phase Diagram. QUESTION 6 Heat Treatments of Steel Using Figure 3, determine the microstructure of steel that has the following heat treatments: (3) Cooling from 800°C to 600°C and held for 3 seconds before quenching to room temperature. (b) Cooling from 800°C to 700°C and held for 100 seconds, then cooling to 400°C and held for 30 seconds, and ﬁnally quenching to room temperature. ‘( N!) '71” (‘UHM pcarlilc NI) ' 5m r- hnv pcurlun: 44M 7 Bantik' 34 1) 211) mu U ._ ,. i . i“. . (H 1 In 10‘ m‘ 141‘ in‘ Time. wcunds Figure 3 TTT curve of Eutectoid (0.77wt%C) steel. END OF PAPER ENBl 10T1.102 (i) FORMULA AND CONS T AN T S SHEET Crystallography E = 2G (1 + v) p = "A Alloying and lever rules MA Elastic and Plastic Properties C A = —mﬁ— x 100 m A + m B 0' = E5 C B = 1 — 100% z" = Gy WA : CB _ C0 8x «9y CB _ CA V = —— = —— g a Z 2 C _ C WE : 0 A CB _ CA Values of Selected Physical Constants Avogadro’s number, NA = 6.023><1023 molecules per mole. Boltzmann’s constant, k= 1.38x10'23 J/atom—K. Gas constant, R = 8.31 J/mole-K. 1eV=1.6x10'19 J 0°C=273 K ENB110T1.102 ...
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ENB110-T1-S2-2010 - |||||||I|||||I| Surname Given Name/s...

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