Question

reverse bending stress of 300 N/mm2 is acting on 55 mm diameter steel. the ultimate strenth of steel is 590 N/mm2. Consider the factors ka= 0.45,Kb=0.85,Kc=0.89 and remaining factor are 1. Calculate the life of the bar for the reliability of 90%.

Answer 1

$S_e'=0.5S_{ut}$

$S_e'=0.5\times 590 =295 \frac{N}{mm^2}$

$S_e= (k_a) (k_b) (k_c) (S_e')=0.45\times0.85\times0.89\times295 =100.42 \frac{N}{mm^2}$

After plotting SN curve:

$log_{10}^{N}=3+1.37=4.37$

N= 23735 Cycles