A solid round bar with diameter of 2.75-in has a groove cut to a diameter of 2.5-in, with a radius of

0.125-in. The bar is not rotating. The bar is loaded with a repeated bending load that causes the bending

moment at the groove to fluctuate between 10 kip.in and 30kip.in and a reversing torque of +10kip.in.

The bar is hot-rolled AISI 1095 (s,, = 66 kpsi, Sut = 120 kpsi), but the groove has been machined.

Determine the number of cycles to failure.