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qs_3 - E-344 Fall 2004 Name LA em Quiz 3 30 November 2004...

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Unformatted text preview: E-344 Fall 2004 Name: LA em Quiz 3 30 November, 2004 |D#: Honor Pledge: Use the backs of the pages if you need more space. Clearly label any work there with an appropriate question number. 1. (15 points) A plain—carbon steel has a yield strength of 35 ksi. a tensile strength of 52 ksi and a modulus of 29,000 ksi. Suppose a 3 inch diameter rod of this steel with a length of 10 feet is loaded in tension with a force of 10,000 pounds. a. Determine the stress in the rod. b. Determine the total strain of the rod. 0. What component of this strain is due to plastic deformation? Briefly explain. _? _ \00w\\os - ‘ ., 2 a o‘- ._ _ 1.. \V\\%E>b\ {3“ F5:— 3’i9\ "I" “\ -._ C5"fl WW; 52 ® 0.:Ee :5 t.— ._._.-. ‘3 E Zai‘oovags'x . .5 .2 Age “9/“; %‘ \s LES") W LE»! ix suesfimamkk RM009'\\ “m \(ngk guess as: W ”EVER. Pace. —1 2. (15 pts) The yield strengths and fracture toughness values characteristic of several engineering alloys are given in the table below. Consider a structural application where a material must support a tensile stress of 730 MPa. If non—destructive testing equipment is available which can detect internal cracks and surface defects larger than 2 mm, which of the three materials would you recommend for the application? Justify your answer. Alloy ch (MPa~m'"2) 0,, (MPa) 7178-T651 Al 23.1 . 570 Ti-6Al-4V 55 1035 4340 steel 60.4 1515 o ‘(W W \meb\wpw Wfiz 0L7? 'WL 1‘3’1‘365‘ PLuhu-Tuh RLWY ¥>W351 W va3lCA3Wbt-A MU\WS 3 {X LDA‘D mvxcfi L.)\\.\. Rm 'Wxg MU-‘VS \t \YLfl) Efrwa‘“ . 0 To fixeewmm HECwEYeD We OM W‘l'slyvu Moss” Coo‘obeF— WWW— WSSWDQL T0 $34M WCWILE, §Wuetmm\ \loo M25? wwlwi “\Y— SURNARL 65- Mt snows L)\\.\ WV. \0 W1. Way-3" WT Nd MWWWL CRZN'AL \s swat“)? p‘eo'bfi: \W&'\\ \5 5 2mm 9 y_ = s- E = Geo will) L“ Luv? {.571 T :- Sc’l- L\ (“Vow fixpcxn 64H > 56‘ w “\"k New \8 m"? .. sumo; m “\3 N’MmK‘nau we“; W Aswan w 5+ SVW on SW» 9% N await CW \CXL . \WMLVW‘ ‘lT Wales 9»: V’D‘BKL WWfi NJ RVMA‘EAB saws Ext/wing “SON?“ 'WEL \AJ\k\ ‘€oSb\‘i’>\‘r ER %\6' T90033W0 3. (15 pts) For the 7075—T6 aluminum alloy described in the diagram below, determine: a. the yield stress; b. the tensile stress; c. the elongation to failure; and d. the modulus. 100 :3.“ 600'. ' _7075-T6 E ' . .. . . . . 80 £2 «5‘ 7. «I E 4505' ' 20241351 60 *3 on CD 5 ' t .e g.) 200 g, C: : C LLl 20 LU 0" .. 0 ‘0 -‘ 0.05 0.10 0.15 0.20 ' Engineering strain, mm/mm @n.) (b) 0.002, 25 0.17:} GMT Ov\—"\": 6);? \b‘\ 57,0 NM a} CB “/o‘flmfaW-me: 815;? .2 " M .. = 660 b?r4 g>\ 5“. ©an Vex - $5 E @~a\sao.wl\ *3 332.2% Pace — 9. 4. (15 pts) Chring problem 7—13: m M o \‘t‘ ma w/S $oggm kg \anLW was Nab-mm W we“ \Wfio. Mi Wow/NS LEW TD N WO‘N‘F m gumcg Gram/i ka M A “119.7 $MP<LK EFFECT ow M ma; Wave-mag 0% m Co‘NEL, Pane—4 In the following multiple choice questions, circle the single answer which best completes the statement. (4 points per problem). 5. A metal can be strengthened by: a. by decreasing its grain size; b. piastically deforming it at low temperature; c. adding alloying elements; all of the above; e. none of the above. 6. Typically for a given material, as yield strength increases, fracture toughness: @ decreases; b. increases; 0. stays the same; d. there is no systematic pattern,; e. none of the above. 7. Hardness is usually determined by: a. compression experiments; b. the 0.2% offset analysis of tensile data; @ indentation experiments; d. fracture-toughness measurements; e. none of the above. 8. Elastic deformation: (3 is fully recoverable when a material is unloaded; b. involves the motion of dislocations; . occurs only after necking begins; c d. is greater in a high modulus material than in a low modulus material for a given load; e. none of the above. Paoe— i 9. Suppose a ceramic material used as an electrical insulator in an automobile was discovered to be broken into two pieces at some time after installation and use. The most likely mode of failure is: a. fatigue; ([9 brittle fracture; c. creep; d. ductile failure; e. none of the above. 10. Suppose a metal rod 2 inches in diameter with a circumferential surface scratch 0.1 inches deep is used as one of several pieces to open a draw bridge that crosses a small river. The rod is loaded in tension and the bridge is opened approximately two times each day. After three years, the rod breaks. The most likely mode of failure is: fatigue; -. brittle fracture; c. creep; d. ductile failure; e. none of the above. 11. Suppose the stress-strain data described in the adjacent diagram were collected from a specimen of polyethylene (PE), a specimen of 1020 plain-carbon steel (1020); and a silica— based glass (SiOz). Which curve corresponds to which material? = PE; 2 =1020; 3 = Si02 = SlOz, 2 = 1020; 3 = PE; = 1020; 2 = SiOz, 3 = PE; = 1020; 2 = PE; 3 = Slog, none of the above. a. c. d. e. 1 1 1 1 12. Suppose a cold-worked metal is annealed at a temperature just below its melting point for 1 hour. Relative to the initial hardness, the annealed hardness would: a. be greater; b. be the same; be less; . depend on degree of doping; e. none of the above. Page. — 6 13. Plastic deformation in an amorphous thermoplastic polymer occurs by: a. dislocation motion; b. creep; @ the flow of macromolecules past each other; d. all of the above; e. none of the above. 14. A material’s resistance to fracture is best characterized by its: @ toughness; b. yield strength; c. ductility; d. modulus; e. none of the above. h=6.626x1o-34 Jsec k=8.617x10-5 eV/K 1ev=1.6x10-19 J c=3x108 m/sec R=8.3144 JImoIe—K nbsine E=hv c=7w a0 J=-D(dcldx) dcldt = d{d2cldx2] dhk! = -—--~-~—~~--— [h2+k2+|2]1l2 D=Doexp[—QIRT] V=|R o=1lr R=pIIA —(Z1e)(22e) Area of a circle = m2 Fattract = ---——-----— Circumference of a circle = 2m 43138032 Surface Area of a sphere = 4 m2 Volume of a sphere = (413) m3; Area of a triangle = (1l2)(b)(h) AGT =4l3atr3AGv + 4an0 %ionic = {1-exp[(-1l4)(Xa-Xb)2]}{100%} Na = 6.022 x 1023 atoms/mole Pace—’7 ...
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