Question

The cold drawn AISI 1040 steel bar with 25-mm width and 10-mm thick has a 6- mm diameter thru hole in the center of the plate. The plate is subjected to a completely reversed axial load that fluctuates from 12kN to 28kN. Use notch sensitivity of 0.83. (40 points) a. Estimate the fatigue factor of safety based on yielding criteria. b. Estimate the fatigue factor of safety based on Goodman and Morrow criteria.

Answer 1

Endurance limit (Se) = Ka kb Ke Se = kako ke los sut) Se =0.838088 X0.85X0SX590 = 183.15 MPa Ord AF solution width of steel bar (10)=25mm thickness of steel bar (t) = 70mm diameter of holeld=6mm FG It and Area of steel ber (19) (4)=tw-el) A=10(25-6)= 190 mm2 notch sensitivity (%) = 0.83 Lar Load 12 KN to 28 KN from figure chart, at d = 2 = 0.24, K4=240 Kf = 1+qkt-1) = 1 + 0.83(2-4 4) –2-162. Amplitude load (ta) = 28-12 = 8kN Hean load (5m) = 28+18 = 20 kN Amplitude stress (P) = Rp Fa - 2152x8x103 = 91.03 MPa Mean stress (6m) = KA Fan Kp Fm - 2:162X 20x183 for cold drawn m = 227.58 MPa Now, surface factor (ka) = his! Sut [ from table Ku = 4:57 (5590) -0.265 Ka = - 0.83 Size Pictool kb) = 1:241257-0107 А 190 A 190 -0.265 Por1040 AISI Styff Sut = 590MPa Syt = 490 MPa = 0.88 Loading factor (ko) =085 for axia) londing

q) fatigue factor of safety based on yielding criteria 69 +6m = syt N 91.03+ 227,58 = 490 N N=1.54 fatigue factors of safety basedox on yielding (N) =:54 b) Factor of safety based on brood man and 6m Sut 6a + Se 91.03 183.95 227.58 + 590 =t 지 N-):133 Factor of sufety based on tundman (N=1133) Morrow criteria N= of '- fatigue strength come coefficient = Sutt 45 = 590+345 = 938 MPa N = = 1:35 (91035) + ( 291745) fatigue factor of safety on morrow (N)=1.35