Question

A bar of steel has the minimum properties S_e = 40 kpsi, S_y = 60 kpsi, and S_ut = 80 kpsi. The bar is subjected to a steady torsional stress (τ_m) of 19 kpsi and an alternating bending stress of (σ_a) 10.2 kpsi. Find the factor of safety guarding against a static failure, and either the factor of safety guarding against a fatigue failure or the expected life of the part.

Based on:

A. modified Goodman criterion

B. Gerber criterion

C. Morrow criterion.

Answer 1

because there is axial and torsional both stresses are given,

So first of all ,we have to find alternating stress( sigma a) and mean stress( sigma m)

After that,,

Acc to given criterian,

We find FOS