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Ps 8 Solutions

Wiley: Fundamentals of Machine Component Design, 5th Edition ... www.wiley.com › ... › Mechanical Engineering › Design Considered a standard in the course, Juvinall and Marshek's, Fundamentals of Machine Component Design continues to focus on the fundamentals of ...

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272 views23 pages

Ps 8 Solutions

Wiley: Fundamentals of Machine Component Design, 5th Edition ... www.wiley.com › ... › Mechanical Engineering › Design Considered a standard in the course, Juvinall and Marshek's, Fundamentals of Machine Component Design continues to focus on the fundamentals of ...

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maris
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8,5) Assumptions: 1. For steel, the tensile strength in psi is 500 times the Brinell hardness. 2. The curve in Fig. 8.5 is an accurate representation of the S-N data for steel. 3. For steel, the endurance limit in psi is 250 times the Brinell hardness. 4. For steel, the endurance limit for 10° cycle is 90% of the ultimate strength. Analysis: 1. Sp’ = 0.5Su in ksi. 2. $ for 103 cycle = 0.9Sy 3. Sutksi) Sy (ksi) § for 10° cycle (ksi) 95 47.5 85.5 185 92.5 166.5 240 100~125 216 Comments: 1, The relationship Sp’ = 0.5Sy is accurate only to ultimate tensile strength values of 200 ksi. The endurance limit may or may not continue to increase for greater tensile strength values depending on the composition of the steel. . 2. For 10°-cycle fatigue strength, actual stress is not as high as calculated values because of significant yielding, SOLUTION Ge) ig Four known standard R.R. Moore specimens are given. Find: Estimate the long-life rotating bending fatigue strength (state whether it is for 108 or 5 x 108 cycles). ~ Schematic and Given Data: ‘Wrought aluminum Sus 29 ksi Wrought aluminum Sa= 73 ksi High grade cast alumi High grade forged magnesium Assumptions: 1, The specimen is subjected to pure bending (i.e., zero transverse shear). 2. Figs. 8.8, 8.9, and 8.10 can be used to estimate the fatigue strength of aluminum and magnesium. 84 . Analysis: From Fig. 8.9, for the wrought aluminum having Su = 29 ksi, the fatigue strength at 5 x 108 cycles is 12 ksi. = 2. From Fig. 8.9, for the wrought aluminum having Su = 73 ksi, the fatigue strength at 5 x 108 cycles is 19 ksi. . 3. From Fig. 8.8, for the high grade cast aluminum, the fatigue strength at 5 x 108 cycles is 11 ksi for sand cast and 15 ksi for permanent mold cast. li 4. From Fig. 8.10, for high grade forged magnesium, the fatigue strength at 108 cycles is 22 ksi. SOLUTION (8.7) Known: Standard R.R. Moore test specimens are made of steels having known ultimate tensile strengths. Find: Estimate the rotating bending endurance limit and also the 10? cycle fatigué strength. Schematic and Given Data: Assumptions: 1. For steel, the tensile strength in psi is 500 times the Brinell hardness. 2. The curve in Fig. 8.5 is an accurate representation of the S-N data for steel. 3. For steel, the endurance limit in psi is 250 times the Brinell hardness. 4. For steel, the endurance limit for 103 cycle is 90% of the ultimate strength. Analysis: 1. Sp’ = 0.58, in ksi. 2. $ for 10° cycle = 0.9Sy 3. oO Syke Sis Stari 10? evele (ksi) Sfp 160 0 as 280 100~125 252 Comments: 1. The relationship Sn’ = 0.5Sy is accurate only to ultimate tensile strength values of 200 ksi. The endurance limit may or may: not continue to increase for greater tensile strength values depending on the composition of the steel. 8-5 2. For the 10°-cycle fatigue strength, the actual stress is not as high as calculated > values because of significant yielding. SOLUTION Known: Standard R.R. Moore test specimens are made of steels having known Brinell hardness. Find: Estimate the rotating bending endurance limit and also the 10° cycle fatigue strength. Schematic and Given Data: Assumptions: 1. For steel, the tensile strength in psi is 500 times the Brinell hardness. 2. The curve in Fig. 8.5 is an accurate representation of the S-N data for steel. 3. For steel, the endurance limit in psi is 250 times the Brinell hardness. 4. For steel, the endurance limit for 103 cycle is 90% of the ultimate strength. 3. S for 10° cycle = 0.9Sa 4, Bho Sa‘tksi) Stor 10" cycle si 200 100 50 350 175 87.5 13. 5 500 250 100~125 225 Comments: 1, The relationship Sp’ = 0.25 Bhn is accurate only to Brinell hardness values of about 400. 2. For the 10?-cycle fatigue strength, the actual stress is not as high as calculated values because of significant yielding. SOLUTION (8.9) Known: Standard R.R. Moore specimens are subjected to loading. | 19) Consider a 3S" dinmdter sel bar S,~ ksi’ S bP ker & machined gurtasat, Eitinglt He Gahyt sheagth For Dsok or more qeles Srio ayes Gor banding Paxil, & ? torsional lading smo: ose tae 2.1, Use Pigs BB tb eshnde Cs, Co2.9 Dh cytes Ce, endures iit) See Ges [oie Bide berding = Gale, Co=.8, (5% 1 pe, Fai tis Oustuey) “oft Sn = SSu= (SFP) = HS dest (Sepang Bee <—_Graplacally 4 30 my te! anal ~ Ce), rhe, BL9), GK > EWS ksi b 5, 2 (BS ks\ IN. BFE) =] 99.5 ksi J torsion - Gs 88, 652.9 ,G2.76 Sys (4a. ks)(s88X. 3%) [FRE ker] A OF cycle sheagth ~ Pht SN gaph, 2 ract aft Sxto cycles | Bonding all fete ples Soon table &L OSa 2 HAA)D P37 key Axial . FSS. BS GPs F248 kel Tocsim Gee Swotncte eYe table 2!) Suse 9 (8) Su =, F097) = 69.8 kei i", 87, gad Ose ‘ tessit ok : 30K! Su gp) ~ = Tas ksi ¥) Sqe Bb Kei ©) See Ks! {boats toon! ince Palen appoint, Sxio!

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