# t2f05 - MAT 200 Quiz#2 — Fall ’04 circle Name(Print Dr...

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Unformatted text preview: MAT 200 Quiz #2 — Fall ’04 circle Name (Print) Dr. Kasachainula Dr. T. Hare This is a closed book test. No notes, books, or information stored in calculator memories may be used. Cheating will be punished severely. All of your work must be written on these pages and turned in. To receive full or partial credit on problems, you must show your step-by—siep calculations starting with the relevant equations. Units must be shown and all plots must have labeled axes. Sketches must be clear and well labeled, and your writing must be legible. Be sure that you read and answer all parts of each question. Multiple choice questions are 2 points each: 2 1. If the grain size is reduced a. the yield strength will be increased b. the hardness will be increased 0. the ductility will be decreased d. all of the above D 2. Slip generally occurs more easily in FCC than in BCC metals because a. there are not enough slip systems in BCC metals b. there are no close-packed planes in FCC metals c. there are nof‘touching” or close packed directions in BCC metals d. the critical resolved shear stress is lower in FCC metals than in BCC metals 8 3. The stress required for failure of a ferrous metal in a given number of cycles is called the a. endurance limit b. fatigue strength 0. fatigue life d. fatigue limit D 4. The hardness test can be used to estimate a. the yield strength b. the creep resistance c. Poisson's ratio (1. none of the above ‘8 5. The recrystallization temperature is raised when a. the amount of cold work is decreased b. the amount of cold working is increased 0. the amount of impurities are lowered (1. none of the above C 6. The Impact test measures a. strength at fracture b. elastic modulus c. energy required for fracture d. tensile strength - page 1 - D 7 The resolved shear stress in a slip plane depends on: a. the orientation of the slip plane b. the orientation of the slip direction 0. the magnitude of the applied stress d. all of the above C 8. Solid solutions have higher yield strengths than the pure metal because a. they have larger grain sizes b. they coutain more dislocations c. dislocations are more difﬁcult to move d the bonds between the atorns are stronger B 9. Creep rate increases a. during the intermediate stage b. when the temperature is raised c. when the applied stress is decreased d. all of the above C 10. When a material stressed above the critical resolved shear stress a. modulus changes b. cracks grow 0. slip occurs d. failure occurs 12 11. Yield Strength is increased by a. reducing grain size b. increasing the amount of impurity atoms c. cold working d. all of the above D 12. A material with a high fracture toughnes a. will fail in a brittle manner ' . b. will fail at comparatively low stresses if small cracks are present c. will exhibit a relatively smooth fracture surface d. none of the above 13. (10 pts) When a metal is annealed in the recrystallization temperature range what happens to the following properties. Answer I (increases), D (decreases) or NC (no change) 1 2 Tensile Strength Yield Strength Elastic modulus Ductility (% elongation) Wale Hardness — page 2 - l4. (5 points) Describe the process of fatigue failure (beginning with crack initiation). How can the fatigue properties of a metal part be improved? fit Same ‘Wt/j. (raw-ex 7U“ Swami? ﬂai‘ﬂ/f7 ‘ ' a 'c’; 40-2} «Cfdc./ﬁ§ ion/{77(6) f/ajfegf,‘yu Ace/#2362} JQMQjL &ue )1 C/ 149 I ' (far/c 5 1’0th " Final Suo’Jen Sfécflmn 0‘9 fungi/Maj (/MS- gee/Lida Pﬁsggyu Im/ﬂ/aL/eme/ris I Sat/gage ifeola‘l/ﬁeu’}; 71.9 angiya/}£/c/aci( nun/9min» o’fj’awﬂ “3.9. >La+p9€nzhcjj Pe’fyf'q/hj/ a -°y¥nj _ G/ﬁz‘n . 5,372. ﬂair-oak} mP’Wa/S aJRQJAQ - Aim)qu «Hue Eﬂecf og sting; ContrtJﬁA/Dé/F (ﬂashy/90 4999/110er {Wﬂtgf (“a/[0L7i — page 3 - 15 ; (12 points) Draw an engineering stress vs. strain curve for a metal. LABEL the axes. Indicate on the plot the following ﬁve quantities: modulus of elasticity, yield strength, tensile strength, toughness and ductility. Also draw a DASHED curve for a metal which has a lower modulus of elasticity, a lower tensile strength and is more ductile than the ﬁrst metal (solid line). 7- t. that Slram I C 16. (6 points) Draw a graph of Yield Strength vs. annealing temperature for a cold-worked metal. LABEL the axes and indicate the three STAGES of annealing (example- recrystallization). , . 17. (6 points) Illustrate an example of a metal showing a ductile-brittle transition on the axes below LABEL the axes. Using a dashed line, show the behavior of an FCC metal such as stainless steel. Tempe/‘6? iii/(’- 18. (5 points) Draw a creep curve showing the stages. Label the axes. Draw also a creep curve using a dashed line at a lower stress and equal temperature. Raf-{KW e" - page 5 — 19. (5 points) A plate is coldworked by passing it between rollers. It has an initial thickness of 0.5 cm and a Width of 4 cm. If we wish to cold work this plate 25%; what should be its thickness after rolling. A”, '45”; >< loo 00 Axum» 0n fie ‘Hij/C/lfﬂ fs‘ ZCl/Uz (Aaﬂﬁt’l AV FOHQ/J, 20. (6 points) A rod 2 meters long and 5 mm in diameter is loaded in tension with a force of 2000N It stretches elastically 0.0004 meters. Calculate its Modulus of Elasticity. , ._ Mi “MW-~- : Q .X 10’ 11,40 /o I M 194009," rzﬁ 9 - page 6 - 21. (9 points) A steel bar is 4 meters long and has a cross sectional area of 0002 m2. It has a Yield Strength of 666 MPa and a Tensile Strength of 880 MPa. Its Ductility is 0.25 (25%). Calculate (a) the maximum load (N) it can sustain without any plastic deformation occurring, (b) the load it would take to break the bar and (c) the maximum amount of plastic deformation (meters) which could be observed in this material- N: 47/; ; (reampﬁ\(0,gozm.>/‘ 22. (6 points) Aluminum oxide has a fracture toughness KIC = 3.8 MPa-mm. If it has surface cracks no larger than 15 x 10'6 m size, what tensile stress can this material withstand before failure? Assume that Y = 1.0. Kid: YJW . Ky ﬂ-I ’6,%Mﬁa-AU“.(// if YW/j WHOM/Mr») /. 5: rsq/Wa / - page 7 - Print Name Here 23. (6 points) Creep rates are given at 2OOMPa for a metal: 10000 3.4x10'6 perhoux 11500 _ 6.8x10‘6 perhour What is the Activation Energy (Q) for Creep? aé - ( 3'7? :K0_nexp6% 5% I” ’ [wk 1- nlﬂd' ﬂf I 0‘ I ‘ ‘1 [3 Wield/la] = In K "‘ “"4 (“Mm " (3st 14M; new) 63: I. In [as want/h] : (“K ,4, ,1 In [mo-Ma) " 6/3, aj/mbk 5001”) Gr _'j____ I ﬁt 3“ {link "(1‘2 3 A: I (O; a) Wpu—a Q¢= - page 8 -' ...
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t2f05 - MAT 200 Quiz#2 — Fall ’04 circle Name(Print Dr...

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