Question

5. (20 pts) A notched circular shaft shown is subjected to fully reversed bending. D-12.7mm, d-10.16 mm, and r-0.5mm. The steel material has the following mechanical and fatigue properties: yield strength (0o)-1000 MPa, ultimate strength (o ) 1200 MPa, the fatigue strength coefficient (σ) 1600 MPa, the fatigue strength exponent (b) 0.1, and the fatigue limit (oe)-400 MPa. a) (10 pts) Determine the fatigue (S-N) curve for the given notched circular shaft under fully reversed bending (computer generated graph is required) b) (10 pts) What is the bending moment amplitude if the desired fatigue life of the notched shaft is 60,000 cycles (considering a safety factor of one)

Answer 1

In this solution some basic concepts and formulas of Fatigue Mechanical Design are used. For more information, refer to any standard textbook or drop a comment below. Please give a Thumbs Up, if solution is helpful.

Solution :

a.)

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The Matlab Code to create the plot would be as follows,

N = [1 1000 1000000 10000000000];

Su = 1200; % Ultimate Strength
Se = 216.15; % Endurance Limit

S(1) = log10(Su);
S(2) = log10(0.9*Su)
S(3) = log10(Se);
S(4) = S(3);

semilogx(N,S)
xlabel('Numbe of Cycles (N) ')
ylabel('Fatigue Stress')
xlim([0 100000000])
ylim([2.2 3.1])
grid on

2.2 10 102 106 เจ้ 10 10 10 Numbe of Cycles (N) 10

b.)

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