• Build upon the results of problem 3-85 to determine the minimum factor of safety for fatigue based on infinite life, using the modified : Goodman criterion. The shaft CD rotates at a constant speed, has a constant diameter of 1.13 in, and is made from cold-drawn AISI 1018 steel. From problem 3-85, the critical stress element in shaft CD experiences a completely reversed bending stress due to the rotation, as well as steady torsional and axial stresses. Thus, a, bend= 12 kpsi, Om, bend= 0 kpsi, Oa, axial= 0 kpsi, om, axial= -0.9 kpsi, Ta = 0 kpsi, and Im = 10 kpsi. The minimum factor of safety for fatigue is

minimum factor of safety for fatigue is = 1.5432

Explanation:

given data

AISI 1018 steel cold drawn as table

ultimate strength Sut = 63.800 kpsi

yield strength Syt = 53.700 kpsi

modulus of elasticity E = 29.700 kpsi

we get here

=    ...........1

here kb and kt = 1 combined bending and torsion fatigue factor

put here value and we get

=    

= 12 kpsi

and

=     ...........2

put here value and we get

=  

= 17.34 kpsi

now we apply here goodman line equation here that is

    ...................3

here Se = 0.5 × Sut

Se = 0.5 × 63.800 = 31.9 kspi

put value in equation 3 we get

solve it we get

FOS = 1.5432

I would say 47 or if u use a yard it would be 69 seconds! Happy braining! Also Nina is a god breian!

Explanation: