A polished round shaft (6 mm dia.) is rotating and under a bending load. There is no torsion on this section of the shaft. It is initially under a fully reversed bending stress of 500 MPa. After 10,000 cycles, that stress is reduced to 465 MPa and cycled to failure. What is the total life of the shaft? Assume the shaft material is a steel with properties Sy = 510 MPa and Sut = 900 MPa.

Find constant a and b in Basquin's Equation,Determine N₁ and N₂ then What is the total service life of the part