Question

(b) The figure below shows two designs for a beam to carry a repeated central load of 5.4 kN. Which design would have the highest design factor for the selected material? (Use SAE 1040 cold drawn steel) | 5.4 kN = 40 mA 250 mm 250 mm SP: 52 MP 050 mm 2.7k Sh Coolioo brought est = 1.00 ( Bondi 500 mm 15.4 kN R=0.90 C8=0.5 200 mm _ 200 mm r5 mm 050 mm 075 mm 7.7K (b)

Answer 1

Solution Geilen Loed (P) = 5.4 kN = 5400N Materiaal SAE 1040 cold dracon steel Sy = 440 MPa Su = 562 MP a Sn = 220 MPa Material facker Cm1 Size Factor (s = 0.81 stres facter Cst 1 Reliability Factor CR=0.8

a) Dia of Shaft D = 150 mm = 0.05m Length of shaft L = 500 mm = 0.5 m RA= Pag = = 2700 N (03) 24 KN Maximum Moment Mmcn = PL - 2.7 40.5 32 32 = 063375 knom = 337.5 Nm Minimum Moment Mrein = o nome Section Mocleellis (z) - I - TB/64 , TOO Z - TID3 - TI/0.053 Z = 1.23x10-5 mp Max stress Than - Mean = 3375 1.23x105 = 2.95 x10 N 2:7.5 MPa Min stress Trin = Mamin - 0 MPa - 2 2 Mecan stres Tream = Than A Trim = 27.5 = 13.75 MPa T amplitude = Maam - 13.75 MPa Good Mauns Guteria mean J Amplitude Su FOS

Diameter Rctionary Diameter Ratio 8 = 2 of 75 - @ 1.5 B0 corrected endurance strength sn= Snt Com - Cat & Cpx (s = 220v 1 x 1 x 0.8 *0.81 Sn= 142.56 MPa .. From ① 13.75 + 13.75 at 562 142.56 FOS Farcicer of Ecefelly Fos= 8.27 b) The Shaft is stepped so stres concentration factcore) should considered By using Graph with 8o and Grominal 324e па? ķ-1.91 From Fig bo-Beiding honout M at point 'C' live at X=200m) M= 2.7462) = 540 Nom .: Trean = Me = 540 = 43.90 MPa o amplitude = ktrorean = 83.85 MPa : From 0 43,90 + 83.8 6 1 70s 562 Design Factor (on) factor of Scefety = 1.50 Design - a would have Highest Design Factar Z 1.22810