An annealed Inconel 601 M12times175 screw experiences cyclic

An annealed Inconel 601 M12times1.75 screw experiences cyclical loading along its axis. If failure is expected at the root of the thread, estimate the maximum axial load this screw can support if it is designed to withstand one million load cycles. Screw dimensions can be found at The diameter at the thread root is indicated by d_3 in the diagram.

Solution

d3 = 9.853 mm

yield strength = 450 MPa

From the S-N curve of annealed inconel 601 we get fatigue stress of 600 MPa (assuming please verify)

600 * 10^6   =   F / pi * 0.009853^2 /4

F = 45.748 kN