Question

A cylindrical steel shaft is subjected to a alternating stress of 150 MPa. Fatigue strength to sustain 1000 cycle is 500 MPa. If corrected endurance strength is 80 MPa, the estimated shaft life will be

Answer 1

Basquin's equation :

$A=S_f{L}^B$

$A=500\times {10}^{3}B$ .... (1)

$A=80\times {10}^{6}B$ ....(2)

Solving (1) & (2)

$A=3125,$

$B=0.266529$

$312=100\times L^{0.26529}$

$\Rightarrow L=93542$