{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

mid2sol - Department of Mechanical Engineering Yeditepe...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 6
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 8
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Department of Mechanical Engineering, Yeditepe University ME 342 MACHINE ELEMENTS 1a Namik Ciblak MIDTERM EXAM 11, May 6*, Spring 2008 NAME: 5 0 L U T1 0 N 5 Time: 150 Minutes Open books and notes. Four questions. Q. l. (10%) Answer the following questions as true (T) or false (F). C_______IRCLES ONLY. Desi- _n is as art as it is science. DET 15 the most conservative static desi- theo The von-Mises stress is not really a stress. IV. In static design of ductile materials, the designer may choose not to include stress concentration effects since they occur in highly localized regions and are relieved due to strain-hardenin_ henomenon. If the stress levels are below the yield strength of the material, fatigue does not happen. Fatigue fracture somewhat resembles the static brittle fracture. la]- VI. The endurance limit modification factors are used because the stress— life ex neriments are not reliable. IX. The surface finish modification factor is used to account for the differences in crack creation in different manufacturing processes. All materials exhibit certain endurance limits. Q.2. (30%) The stresses at a point in a machine part made of Gray Cast Iron ASTM grade 40 are found, in MPa, to be ox 2 200,0), : ~500,0z = —250,ryz = 200,233, 2 400,er = 300 Determine the static factor of safety. Assume brittle material and use Modified-Mohr theory. Let 0A =01 and 0'3 :03. Q.3. (30%) The sign post in the figure is subjected to a uniformly distributed load due to a steady wind with a velocity of 36 kmfh in ' —z direction as shown. As you learned in fluid mechanics, one can apply the Bernoulli’s equation between a point upstream and a point on the sign post, where stagnation is assumed, to get the following relation Ty'fézrr AP=PS -Pa =épu2 where ,0 =12 kg/m3 is the air density. Determine the ratio -— corresponding to a static factor of safety of 3 according to the distortion energy theory. Material: A181 1030 HR Q.4. (30%+10%) The figure shows a traditional swing that you could see in many playgrounds. The post (the column) of the main structure is to be designed. Assume that the swing executes a circular motion from — 9m“ to + 6m,1x . Note that the maximum velocity is attained at 6 = 0 and velocity is zero at maximum swing angle. We are interested in determining the maximum moment at the bottom of the post due to tension 2". For this, one should first complete the dynamic analyses. Using the free—body diagram of the swing seat as shown in the figure at right, the following equilibrium equations in curvilinear coordinates can be written: v2 2F, =—Wsin6=ma, and SF" =T—Wcose9=man =m? 172 Therefore the tension at any angle is given by: T = W 00319 + m T . Now, if one writes the energy equation, assuming no dissipation, between the lowest position and any angle, the following is obtained: v2 = 2gL[cos€ - cos 6mm ]. Therefore, T = W 0056 + 2mg[cos 6 — cos Qmax] = W[3 cos 6 — Zcosflmax] a) (BONUS: 10%, Please try to solve this as last) Show that the maximum and minimum moments at the base of the post occur at following angles. am, if 9m 3 30° 6 . . z i critical COS—1 [.16. [005 6m“ + m1] if 6m” 2 300 b) (5%) Assuming that the result in part (a) is correct. Determine the angle and value of maximum moment if m = 100 kg, L = 2.5 m, amax = 60°. Take g =9.81 III/52. c) (20%) The post is to be made of A181 1030 CD round tubing, with an outer diameter of 60-min and thickness of S-mm. Estimate the life in cycles corresponding to a reliability of 99.99%. (1) (5%) Assume that the swing is used 10% of the time in a day and the period of one swing (oscillation) is about 3 seconds. Now, state the life in days. YEDITEPE UNIVERSITY FACULTY OF ENGINEERING AND ARCHITECTURE DEPAITIENT 0F __ YEDITEPE UNIVERSITY ., ,, my". . ......., ..... FACULTY OF ENGINEERMG AND ARCHITECTURE {fig Wages—IE. ------------------------------------------ _ bananas? or __ ___________________ W 5:10;”? 44' 5:4" . _, mfls Sm: ’ 292 Fm 70‘1"" Au §u0= 370 mp“ ._( 970-293 _ “1.7.1!— .:2. Cr—f 35‘”) 970 {13 970*393 ___—— ’5) £61,111 YEDITEPE UNIVERSITY /; FACULTY or “smegma AND mcnrrecwnz ”W DEPAITHENT 0F __ .—-.u-ou.o—-.~. ’r i: z/{iit/ 0;? nu-——-mq——m—__—_u._—-—uuu——-_—..... YEDITEPE UNIVERSITY FACULTY OF ENGINEERING AND ARCHITECTURE DEPARTMENT OF if- cue (g‘flg'zwa'w)+ :: 2: ‘3 0L9 .. 7cu‘6—35inge —— 20“5m"‘ “36; can? ='—«0 a 3mm; —- 3 (”“2” " 2609”“ '(Ooéze -- ZCGWM 609 ”3:0 '1‘ 6056' '- ‘ 2 MM)“ TAG I] d ? MEM’S :ZdJamtx 1: 4.663900“ "4* 6‘63) (Cu 9 L = m- ‘ I) :Z![Cnam.£~/W C70 ..- 8mm -. 9.04471'M : 5"” 6° / 7 C03 e >/ C4” 6W W M a ‘fmwmml WW" ‘ + 5"“ >/ WM ‘33 GM :9) 1% * w'Ow-K 2 75 3 a 3.2- .— Cdj Gm é '24"— 4r 5% A (.71 mcfc‘fl M" 3:,1 égnw wimZ mar @‘ignmx- YEDITEPE UNIVERSITY FACULTY OF ENGINEERING AND ARCHITECTURE DEPAITIEIT 0F ___ .-.._.._.._.-_.,_.._ ' 5 1: «57,312 M 6 W46 _M/mm m 3730 m » -73,” 5M6 0] M -h l m /m - 2452 1; 6.‘a(373‘3)[2w(3wl3)6/] _ + , .-. Z; 2060‘; N m fwd-M’s“ ' Q 6: 37'3” 1L1, ~6o“\ .6 x. T J \ / zogoxum “a .00 (Fm?! Joe 63%“) I .:_ ‘2 h .5 \1x36005‘ l 6103 MB I C“? ”A310 SE60 cl 6) (0/0 MIG-98 ( oLfiD""J"e') I: I2‘-S— day! ((534 M J )52092 cvf-/(‘{3“""' 3/) 427,0 YEDITEPE UNIVERSITY FACULTY OF ENGlNEEMNG AND ARCHITECTURE DEPAITIENT OF _._ unuwu—u-uuq...—_——_..__..—-....————-._.-. lure 64. 5’24 (0W0 deco-37.615510 -.:. 22'? mm ,s Q :; 1.24 (22.2) ' :of—io k z I (WW3) m M m: f“ I (<2 500 W at;- , (w) (a: :19.”er / (if :1 “R'— (\ H C‘\ D- «.9 GR 8, ex 0 So NS ca. V ('\ 9 \I a Q", Q CA a. ‘i 0‘ .‘D 4 ‘ .~ g ,3 0"“:- -———-——-—‘-" z _ . v.39"? ‘ a Iszzfl Wk :-—o.\734o 5f 5r77 ”0.1.2774 I 1. twig“) .— L 3 d4”- Co-ew'fio) ’ - ”ll°3( 139.7 3 N” '53’5'7’ ...
View Full Document

{[ snackBarMessage ]}