Question

Calculate the fatigue stress concentration for a steel filleted shaft that is loaded in bending. Given Data: Sut = 440 MPa D (for larger cross-section) = 64 mm d (for smaller cross-section) = 32 mm r(fillet radius) = 4 mm

Answer 1

`K_f = 1.422`

Explanation:

We know that relationship between fatigue and stress concentration factor

`K_f = 1+q(K_t-1)`

Where

`K_f`=fatigue concentration factor

`K_t`=stress concentration factor

q=Notch sensitivity

Here D/d=2 and r/d=0.125

Now from standard design data book
`K_t=1.79`

For Sut=440 MPa and r= 4 mm

q=0.8

Now by putting the values

`K_f = 1+q(K_t-1)`

`K_f = 1.8(1.79-1)`

`K_f = 1.422`