Question

(a) Part 1-7 6) Leeding Digun The figure shows the tentative design of a cantilevered machine component, and the corresponding loading diagram. The component resists a load P varying from 0 to 3400 1bs., for an infinite number of cycles at ambient room tem- perature and 95% reliabilfity. The part is machined from cold drawn steel with an ultimate strength of S 64 kpsi and a yield strength S, = 54 kpsi. con for the part, if the stress c Determine a suitable min imum diameter d centration factor K, = 1.5 and the size correction factor is 0.875 List all assumptions and decis jons made in the calculations and determine the endurance strength factor of safety for your design Use the attached information. ENDURANCE-LIMIT MODIFYING FACTORS Neth seitity is defined by the equain een that the retating-beam specimen used in the laboranory to deser- ne eurance limis is prepared very carefully and asted under elosele con led conditions. It is unrealistic to expect the endurance limit ofa mechanical al member to match values obtained in the laboratory. warin classifies some of the factors that modify the enduranee limit, and are shown in Table 7-4. To account for the most important of these nditions we employ a variety of modifying factors, each of which in intended t r ha K,- where e is unually berween zere and unity k, STEESS CONeem PheTOR count for a single effect. Using this idea we may write s.-,kS ere S,endurance limit of mechanical element S-endurance limit of rouacing-beam specimen surface factor -size facter k,-reliability factor temperature factor modifying factor for stress concentration k,-miscellaneous-effects tactor Neveh rdun,m 10 1.440 20 25 16 3.5 S-200 p p7 Sorels Num aloy GIF 14 Noh rs in Nochsidviry charu for sueels and UNS A3202 wghe alumiam aloys subjeced ta severned beading or revese al loads For larger noch radi we the values of corraponding r a16 a (4 ma) (Rpradaced by piri frm Gre Sins and J. L Waimed, Msal Fai, MeGrH, Ne Yrk, 19, p 2, 3 Mean sress. Faigue when the rnsie of the two is given values ofe, and e. agram showing how to ind the limiing Surface-6nish modificacion facton for ated Thee are the , faciors for use in Eq. (7-15) RELLABILITY FACTORS CORRESPONDING TO Tensle strengh S, GPa PERCENT STANDARD DEVIATION OF THE AN ENDURANCE LIMIT 1.6 0.6 0.3 10 1.2 1,4 Plished Ground7 I Reliability factor Reliabliry R Sandardized variable 09 08 L000 Machined or cond drawn 0 9.897 4868 1443 222 0814 0.733 4.202 0638 4420 101 4263 Mor pledi As forged 99 99 0331 0.320 S612 a 99 Thus, the reliability factor i, is mean endurance limit, 220 240 180 200 80 140 160 1-0.08 Tensile strengh Skpsi www.

Answer 1

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